Chemical engineering education

Material Information

Chemical engineering education
Alternate Title:
Abbreviated Title:
Chem. eng. educ.
American Society for Engineering Education -- Chemical Engineering Division
Chemical Engineering Division, American Society for Engineering Education
Publication Date:
Annual[ FORMER 1960-1961]
Physical Description:
v. : ill. ; 22-28 cm.


Subjects / Keywords:
Chemical engineering -- Study and teaching -- Periodicals ( lcsh )
periodical ( marcgt )
serial ( sobekcm )


Chemical abstracts
Additional Physical Form:
Also issued online.
Dates or Sequential Designation:
1960-June 1964 ; v. 1, no. 1 (Oct. 1965)-
Numbering Peculiarities:
Publication suspended briefly: issue designated v. 1, no. 4 (June 1966) published Nov. 1967.
General Note:
Title from cover.
General Note:
Place of publication varies: Rochester, N.Y., 1965-1967; Gainesville, Fla., 1968-

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
01151209 ( OCLC )
70013732 ( LCCN )
0009-2479 ( ISSN )
TP165 .C18 ( lcc )
660/.2/071 ( ddc )

UFDC Membership

Chemical Engineering Documents


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z 0 u C w C) z c,:: w w z l5 z w c,:: 0 LL. >1w u 0 V) z ii: w LL. 0 z 0 V) > C C) z ei:: w w z -0 z w _, u w :I: u VOLUME X NUMBER 2 SPRING 1976 Berkeley's JOHN PRAUSNITZ and his MOLECULAR THERMO FOR CHEMICAL PROCESS DESIGN ChE at WORCESTER POLYTECHNIC INSTITUTE Saponification Experiment Process Control by the PSI Method FLOWTRAN Simulation in Education Mass Transfer Coefficients: An Analysis An Ivory Tower Man Dines in the Real World Can An Engineer Be Actualized?


If we don't wash our wastewater he may have to drink it. Every day, a million people living in a typical American city generate about half a million tons of wastewater. Sewage systems in many cities cannot cope with these amounts. So wastewater is not cleaned thor oughly before it's discharged into rivers and lakes, and con tributes to their pollution. The same rivers and lakes we rely upon for our drinking water. Union Carbide has developed a wastewater treatment system called UNOX. It cleans the dirty water of towns and cities faster, cheaper, and uses less energy and space than any system de vised before it. The Unox System uses high purity oxygen instead of air.The oxygen is forced into a series of closed treatment tanks where it increases the efficiency of the microorganisms that feed on pol lution and improve water quality. Nearly 100 cities are now us ing or installing the Unox Systern. As the population of Amer ica grows, so does our need for clean water. And if we don't clean our dirty water, no one is going to do it for us. Today,something wedo will touch your life. An Equal Opportunity Employer M/F


EDITORIAL AND BUSINESS ADDRESS Department of Chemical Engineering University of Florida Gainesville, Florida 32611 Editor: Ray Fahien Associate Editor: Mack Tyner Business Manager: A. W. Westerberg (904) 39 2-0861 Editorial and Business Assistant: Bonnie N eelands (904) 392-0861 Publications Board and Regional Advertising Representatives: Chairman: William H. Corcoran California Institute of Technology SOUTH: Homer F. Johnson University of Tennessee Vincent W. Uhl University of Virginia CENTRAL: Leslie E. Lahti University of Toledo Camden A. Coberly University of Wisconsin Darsh T. Wasan Illinois Institute of Technology WEST: George F. Meenaghan Texas Tech University SOUTHWEST: J. R. Crump University of Houston James R. Couper University of Arkansas EAST: Le on Lapidus Princeton University Thomas W. Webe1 State University of New York L ee C Eagl eton Pennsylvania State University NORTH: J. J. Martin University of Michigan Edward B. Stuart University of Pittsburgh NORTHWEST: R. W. Moulton University of Washington Charles E. Wicks Oregon State University PUBLISHERS REPRESENTATIVE D. R. Coughanowr Drexel University UNIVERSITY REPRESENTATIVE Stuart W. Churchill University of Pennsylvania SPRING 1976 Chemical Engineering Education VOLUME X NUMBER 2 SPRING 1976 FEATURES 60 .l!eclwie1975 Molecular Thermodynamics for Chemical Process Design, J. Prausnitz DEPARTMENTS 56 The Educator John Prausnitz of Berkeley 70 Departmentslof Chemical Engineering Worcester Polytechnic Institute 74 Laboratory Saponification of Acetamide in a Batch Reactor, S. Weller Classroom 76 Instruction By the PSI Method in a Required Senior Course, D. Hubbard 84 Packed Column Mass Transfer Coefficients for Concurrent and Countercurrent Flow, J. Miller and T. Rehm 94 Can An Engineer Be Actualized? J. Biery 80 Views and Opinions An Ivory Tower Man Dines in the Real World, R. Robertus 90 CACHE Use of FLOWTRAN Simulation in Education, J. Clark and J. Sommerfeld 68, 93 Books and Reviews 59 News 55, 100 Division Activities CHEMICAL ENGINEERING EDUCATION is published quarterly by the Chemical Engineering Division, American Society for Engineering Education. The publication is edited at the Chemical Engineering Department, University of Florida. Second-class postage is paid at Gainesville, Florida, and at DeLeon Sprin gs Florida. Correspondence regarding editorial matter, circulation and changes of address should be addressed to the Editor at Gainesvill e, Florida 32611. Advertising rates and information are available from the advertising representatives. Plates and other advertising material may be s ent directly to the printer: E. 0. Painter Printing Co., P. 0. Box 877, DeLeon Springs, Florida 32028. Subscription rate U S., Canada, and Mexico Is $10 per year, $7 per year mailed to members of AIChE and of the ChE Di vision of ASEE. Bulk s ub scr iption rates to ChE faculty on request Write for prices on individual back copies. Copyright 1976. Chemical Engineering Division of American Society for Engineering Education, Ray Fabien, Editor. The statements and opinions expressed in this periodical are those of the writers and not necessarily those of the ChE Division of the ASEE which body assumes no responsiNiity for them. Defective copies replaced if notified within 120 days The International Organization for Standarization has assigned the code US ISSN 0009-2479 for the identification of this periodical. 53


----------------------------ACl{NOWLEDGMENTS Industrial Sponsors: The following companies donated funds for the support of CHEMICAL ENGINEERING EDUCATION during 1975-76: MONSANTO COMPANY 3M COMPANY Departmental Sponsors: The following 115 departments contributed to the support of CHEMICAL ENGINEERING EDUCATION in 1976: University of Akron University of Alabama University of Alberta Arizona State University University of Arizona University of Arkansas Brigham Young University University of British Columbia Bucknell University University of Calgary California Institute of Technology University of California (Berkeley) University of California, (Davis) Case-Western Reserve University Chalmers University of Technology University of Cincinnati Clarkson College of Technology Clemson University Cleveland State University University of Coimbra University of Colorado Colorado School of Mines Columbia University University of Connecticut Cornell University University of Delaware University of Detroit Drexel University University College Dublin Ecole Polytech, Canada University of Florida University of Houston University of Idaho University of Illinois (Urbana) Illinois Institute of Technology Indiana Institute of Technology University of Iowa Iowa State University Kansas State University University of Kentucky Lafayette College Lamar University Laval University Lehigh University Loughborough University (England) Louisiana Technological University Lowell Technological Institute Manhattan College University of Maryland University of Massachusetts Massachusetts Institute of Technology McNeese State University University of Michigan Michigan State University Michigan Tech. University University of Minnesota University of Mississippi University of Missouri, Rolla Montana State University University of Nebraska University of New Hampshire New Jersey Institute of Technology New Mexi co State University City University of New York Polytechnic Institute of New York State University of N Y. at Buffalo North Carolina State University University of North Dakota University of Notre Dame Nova Scotia Technical College Ohio State University Ohio University Oklahoma State University University of Oklahoma Oregon State University University of Ottawa University of Pennsylvania Pennsylvania State University Princeton University University of Puerto Rico Purdue University Queen's University Rensselaer Polytechnic Institute University of Rhode Island Rice University University of Rochester University of South Carolina South Dakota School of Mines Stevens Institute of Technology Tennessee Technological University University of Tennessee Texas A & M University Texas A&I University University of Texas at Austin University of Toledo Tri-State College Tufts University University of Tulsa University of Utah Vanderbilt University Virginia Polytechnic Institute Washington State University University of Washington Washington University University of Waterloo Wayne State University West Virginia University University of Western Ontario University of Windsor University of Wisconsin Worcester Polytechnic Institute University of Wyoming Youngstown State University TO OUR READERS : If your department is not a contributor, please ask your department chairman to write CHEMICAL ENGINEERING EDUCATION, c / o Chemical Engineering Department, University of Florida, Gainesville, Florida 32611. 54 CHEMICAL ENGINEERING EDUCATION


.... ~~ ... CHEMICAL ENGINEERING DIVISION ACTIVITIES 3M Company Increases Annual Lectureship Award Grant The 3M Company has increased their grant to cover the Annual Lectureship Award from $2,500 to $3,500. The change is effective for 1976 and the additional funds will be used to provide a $500 honorarium to the awardee in recognition of the tour that he now makes to three schools where he presents the same lecture he gives at the An nual Conference. The purpose of this award is to recognize and encourage outstanding achievement in an im portant field of fundamental chemical engineering theory or practice. Bestowed annually on a dis tinguished engineering educator who delivers the Annual Lecture of the Chemical Engineering Di vision, the award consists of $1,000 and an en graved certificate. The 1975 ASEE Chemical Engineering Di vision Lecturer was Dr. John M. Prausnitz of the University of California, Berkeley. Dr. Prausnitz's lecture was entitled "Molecular Thermodynamics for Chemical Process Design." ANNUAL CONFERENCE OF THE AMERICAN SOCIETY FOR ENGINEERING EDUCATION University of Tennessee June 14-17, 1976 Chemical Engineering Program Chairman: A. J. Perna, New Jersey Institute of Technology Event 1620 STOP THE ROLLER COASTER WE WANT TO GET OFF OR DO WE? W. D. Baasal Session Chairman, Monday, 3:45-5:30 p.m. Event 2135 ChE Division Meeting Business Discussions / Executive Session, Tuesday, 7:30 a.m. Event 2520 3M AW ARD LECTURE, Tuesday, 1:45-3:30 p.m. Event 2735 ChE Division Banquet Sheraton Executive Park, Tuesday, 6 : 30 p.m. Event 3215 FACULTY WORKLOAD MEASUREMENT CORRECTION Editor's Note: Professor John Prausnitz of the University of California, Berkeley has pointed out an error in the article on Professor John O'Connell in the Winter 1976 issue. He was quoted as saying that a chair that O'Connell used at Berkeley "originally belonged to the late Professor Latimer, discoverer of the hydrogen bomb (sic) when he was dean of the college." What Professor PrausSPRING 1976 L. C Eagleton Session Moderator, Wednes day, 8:00-9:45 a.m. Event 3415 ChE Division Luncheon, Wednesday, 12:00 Noon Event 2603 PREPARING ENGINEERS FOR THE FOOD INDUSTRY, Tuesday, 3:45-5:30 p.m. Event 3310 LET'S NOT BOTCH METRIC CONVER SION, Wednesday, 10:00-11:45 a.m. Event 4205 FOOD / ENERGY / ENVIRONMENT SYS TEMS, Thursday, 8:00-9:45 a.m. Event 4320 Mini-Plenary FOOD/ENERGY ENVIRON MENTAL INTERFACE, Thursday, 10:0011:45 a.m. (co-sponsored by AIChE). nitz did write was ... Professor L at imer, dis coverer of the hydrogen bond." Since the various drafts of the paper have been destroyed, no one here knows how the incorrect attribution oc curred. (The editor's alibi is that he was in Vene zuela when the letter from Prausnitz arrived.) But we all deeply regret the error and apologize to Professor Prausnitz for any embarrassment it may have caused him. 55


[! ;j pll educator John Pl/aUd.mt1 Prepared by a colleague, C. J. KING, Un iver s i t y of Califo rni a Be r k e l ey, Californ i a 94720 of Berkeley J OHN PRAUSNITZ'S ASEE Chemical En gineering Division Award Lecture is published elsewhere in this issue. In it, John illustrates the utility of molecular thermodynamics for solving a number of key problems in the chemical pro cessing industries. This is a concept which has guided his entire academic career. His goal has been to span the wide gap between the theories of physical chemistry, molecular physics and statistical mechanics, on the one hand, and the real needs of the design engineer, on the other. How well John has succeeded in this mission is attested by the considerable impact his work John has had a particularly close relationship, during his years at Berkeley, with Joel Hildebrand who at age 94 remains active in thermodynamics and interpretation of liquid-state properties has had on the petroleum and chemical in dustries. Most large companies in those fields have now based their phase-equilibrium prediction methods on his extensive publications and on ap proaches which he and his co-workers have de veloped. Two books by John and his colleagues Comput e r Cal c ulations for Multicompon e nt Va por-Liquid Equilibria and Computer Calculations for High-Pr e ssur e Vapor-Liquid Equilibria, give predictive methods suitable for the computer 56 John and Joel Hildebrand celebrate the publication of "Molecular Thermodynamics of Fluid Phase Equilibria". They have been widely used and adapted in in dustry John has himself been a regular con sultant to a number of industrial companies, in cluding Air Products and Chemicals C orp. (for 16 years), Union Carbide C orporation and Fluor Corporation. Table 1 shows the current affiliations of 40 Berkeley graduates who have received the Ph. D during the period from 1959 to the present while carrying out research with John The large number of petroleum, chemical and design and construction companies represented on the list is no a ccident, for many of these graduates are serving as principal sources of expe r tise on phase equilibrium prediction and related problem s An estimate says that ten now ha v e such roles, while most of the rest are carrying out functions that draw on their Prausnitz background in other ways. Some of those listed hold high managerial level positions IMPACT ON EDUCATION JT IS ALSO APP ARENT from Table 1 that John has had great impact upon education, with graduates on the faculties of ten universities. Several of these professors have spread their ac tivities into other areas, but all have an element to their work that clearly stems from Berkeley and molecular thermodynamics. Further, nu merous visiting professors and post-doctoral fel lows, many from Europe, have carried "the mesCHEMICAL ENGINEERING EDUCATION


-------------------TABLE 1. Graduates Whose Ph.D. Theses were Supervised by John Prausnitz UNIVERSITY FACULTY Robert F. Blanks Alan L. Myers Charles A. Eckert Henry M. Renon John P. O'Connell H. Gordon Harris, Jr. Clayton J. Radke David C. Bonner Juan H. Vera Enrique R. Bazua IN INDUSTRY Elton J. Cairns Robert W. Hermsen Stephen A Shain Newell K. Muirbrook Robert F. Weimer William J. Lawrence John F. Heil Frank B. Sprow Ping-Lin C hueh Raymond N. Fleck Constantine Tsonopoulos George T. Preston Edward W. Funk Peter M. Cukor Richard D. Newman Cecil Chappelow III Denis S. Abrams KwangW. Won Dennis P. Maloney Samii Beret IN GOVERNMENT R. Norris Keeler Albe rt E. Sherwood Sadok E. Hoory William R. Parrish OTHER Ralph Anderson Morton Orentlicher Robert V. Orye Gerrit J. F. Breedveld Bryan L. Rogers Kevin K. Tremper SPRING 1976 Michigan State University University of Pennsylvania University of Illinois Ecole des Mines, Paris University of Florida University of Wyoming University of California, Berkeley Texas A&M University McGill University, Montreal National University of Mexico General Motors Corp. United Technology Co rp. Shell Development Co. Exxon Research & Engineer ing Co. Air Products & Che mical s Corp. United Technology Corp. Stauffer Chemical Corp. Exxon Company, U .S. A Shell Development Corp Union Oil Company Exxon Research & Engineer ing Co. Occidental Petroleum Corp. Exxon Research & Engineering Co Teknekron Corporation Gulf Oil Chemicals Co. Pfizer Corp Buffalo Salt Works, South Africa Fluor Corp. Exxon Research & Engineer ing Co. Union Carbide Corporation Chief Scientist, U.S. Navy Lawrence Livermore Labora tory Israel Atomic Energy Commission National Bureau of Standards Construction Business Biomedical Research, Columbia Medical School Dental School Research Associate, UCB Sculptor Medical School sage" back to their home institutions. Molecular Thermodynamics of Fluid-phase Equilibria, the Prausnitz text on molecular thermodynamics and ways of utilizing it, is found in classes at many universities both in the U.S. and abroad. Many of John's publications are based on re search done as independent projects by graduate students whose Ph. D. theses were directed by other faculty members. One example is the well known gas solubility correlation, co-authored by Fred Shair, now professor at Cal Tech; another one is the UNIF AC activity coefficient correlation co-authored by Professor Aa. Fredenslund (Den mark) and Russell Jones, now with Union Car bide . .. John is probably the one engineering professor anywhere to have produced a Ph.D. graduate (Bryan Rogers) with a joint degree in Chemical Engineering and Art, with ChE principles actually having been used as the basis for fluid kinetic sculptures. John grew up in Forest Hills, N. Y., at that time a still-green, crime -fr ee and pleasant part of New York City with open fields and wooded areas between ever-increasing urbanization. He attend ed Cornell as an undergraduate, in the Dusty Rhodes heyday. From this experience, he emerged a "pro" at technical writing, with a talent for clarity and standards still forcefully transmitted to students, and to faculty colleagues as well He uses a red pencil for "ordinary" errors and a green one for those that are particularly offensive to his aesthetic sensibilities. He has a passion for hyphenating compound adjectives and has a running battle with copy editors who keep trying to take the hyphen out. With Robert Reid and the late Tom Sherwood, John recently completed the third edition of "Properties of Gases and Liquids," now in press. Will any hyphens remain in the final text ? After a year" for a Master's at Rochester, John entered the Ph. D. program at Princeton. Although he already was intrigued by physical chemistry and by the broad power, universality and intellectual beauty of thermodynamics, he chose to work in the field of chemical reactor de sign for his Ph. D. research, so as to broaden his outlook and to enable a close association with Richard Wilhelm. John credits Wilhelm as one of the two great technical motivating forces in 57


One of his goals has been to span the wide gap between the theories of physical chemistry and molecular physics and statistical mechanics on the one hand, and the real needs of the design engineer on the other. his career; the other one is Joel Hildebrand. After two years as Instructor at Princeton, John came to Berkeley as Assistant Professor in 1955, and has been there ever since. Married in 1956, Susie and John live in the Berkeley Hills with their children, Stephanie and Mark. During his reactor-design days at Princeton, John's interest in thermodynamics was rekindled by his almost accidental discovery of the books, "Solubility of Non-Electrolytes" by Hildebrand and Scott and "Mixtures" by Guggenheim. The fascination of those two books, so different in style and yet so similar in purpose, set the goal of his career-to apply physico-chemical p r inciples for the development of efficient pro cedures for property estimation, vapor-liquid equilibria, solvent selection, etc., as needed for chemical engineering design. John has had a particularly close relationship during his years at Berkeley with Joel Hildebrand, who at age 94 remains active in thermodynamics and interpreta tion of liquid-state properties. Responding to a challenge from Ted Szabo, a friend from Union Carbide and a connection made through former student Bob Blanks, John has devoted much of his recent efforts to the prob lem of understanding the complex phase behavior of polymer-solvent systems, especially at high pressures This is a universal problem in polymer industries, and provides hopes for design modi fications to minimize the considerable energy con sumption of manufacturing processes for polyHe chose to work in the field of chemical reactor design for his Ph.D. research, so as to broaden his outlook and to enable a close association with Richard Wilhelm. John credits Wilhelm as being one of the two great technical motivating forces in his career; the other one is Joel Hildebrand. 58 ethylene and other polymers. John's many accomplishments were fittingly recognized by the Colburn and Walker A wards of AIChE and by election, in 1973, to the National Academy of Sciences. Stemming from his German background, John is a sausage-loving German-ophile and Swiss-ophile, having spent sabbatical leaves through Guggenheim Fellowships in Zurich (ETH) and Karlsruhe (Inst. fiir phys. chem.). He has this spring departed for another leave at the Technical University of Berlin, financed through the Alexander von Humboldt fellowship. SATURDAYS WITH THE MET ff E IS A LOVER of classical music, stemming from WQXR in New York, and has maintained strong interests in the history of science (from "Germanophile" Prausnitz occasionally travels west ward as well. Here he is after returning from Japan, along with Susie, Stephanie and Mark. Henry Guerlac at Cornell) and in philosophy and theology, stemming from encounters w ith Rein hold Niebuhr, Paul Tillich and Martin Buber at Princeton and in New York. Recently he served on the Ph. D. thesis committee of a student at the Berkeley Theological Union whose dissertation connected the thought of Jung, Kierkegaard and Niels Bohr. It is also no accident that John is probably the one engineering professor anywhere to have produced a Ph. D. graduate (Bryan Rogers) with a joint degree in Chemical En gineering and Art, with Chemical Engineering principles actually having been used as the basis CHEMICAL ENGINEERING EDUCATION


for fluid-kinetic sculptures. On Saturdays, John is usually in his office, ostensibly to catch up on his voluminous cor respondence. But intimates know the real reason is to hear the Metropolitan Opera broadcasts from New York. Pesistent rumors within the Department at Berkeley have it that John is a tennis player. Un fortunately his regular and obviously accomplish ed efforts on the courts seem to be carried out sub rosa, and the noontime Chem. E. faculty hackers league has yet to do him battle! John is a lover of the outdoors, but only in moderation. His real preference is for Swiss-style hiking where, after a few miles in the woods, one can find a cozy restaurant. An annual event most recently on the 100th anniversary of J. Willard Gibbs' great publication-is the grand trek and picnic of his research group and con freres to one of the more bucolic locations near the San Francisco Bay Area. INSPIRATION AND CONSOLATION T HE JIMINY CRICKET of the Berkeley cam pus, John is one to keep colleagues, and par ticularly harassed Chairmen, well reminded of the lil;)?I news PROFESSOR T. M. REED, UNIVERSITY OF FLORIDA Dr. Thomas M. "Tim" Reed, III, Professor of Chemical Engineering, University of Florida, died of injuries from a car-bicycle accident, March 5, 1976. He was 54. He was co-author with K. E. Gubbins of the University of Florida of the book, "Applifid Statistical M echanics", McGr aw Hill, 1973 and papers in statistical mechanics and fluoro carbon chemistry. He received his Ph.D. from Pennsyl vania State University and came to Florida in 1952. A memorial scholarship has been establis hed in his name by the Chemical Engineering Department of the University of Florida. Contributions should be made payable to th e University of Florida Foundation. BARLAGE NAMED CLEMSON DEPARTMENT HEAD William B. Barlage Jr., a native of Philadelphia, Pa., has been named head of the chemical engineering depart ment at Clemson University. Barlage, who began his Clemson teaching ~areer in 1958, has directed six research projects totalmg more than $174,000 since 1961. He is a former member of the advisory committee for chemical e n gineering technology at Greenville Technical College. In 1956 he was on the staff at North Carolina SPRING 1976 He is a lover of classical music, and has maintained strong interests in the history and in philosophy and theology, stemming from encounters with Reinhold Niebuhr, Paul Tillich and Martin Buber at Princeton and in New York. more philosophical and idealistic sides of their university endeavors. With great skill, he manages to avoid administrative positions. However, he maintains a close watch on the progress of young er colleagues, offering an interested ear, dis cussions, probing questions and occasional hints on possible sources of research funds. In his office he maintains a well-worn couch. It was intended to put students at ease but in fact it is used primarily by fellow faculty mem bers who are in need of inspiration or, more often, consolation. The Berkeley Chemical Engineering Depart ment is only 30 years old. Much of what it has become is the result of the perceptive and able efforts and accomplishments of John Prausnitz. State Universit y, where he taught chemical engineering aspects of nuclear engineering to students visiting the United States under the Atoms for Peace program. Barlage received the bachelo r's degree from Lehigh University (1954), master's from the University of Virginia (1956), Ph.D. from North Carolina State Uni versity ( 1960), and completed post-doctoral study at the University of North Carolina at Chapel Hill (1962). CALL FOR PAPERS FOR GRADUATE EDUCATION ISSUE IN A LETTER DATED APRIL 19, 1976 EACH DEPARTMENT CHAIRMAN WAS ASKED TO SUGGEST FACULTY MEMBERS IN HIS DEPART MENT WHO MIGHT BE INTERESTED IN PRE PARING A PAPER FOR THE SPECIAL FALL 1976 ISSUE OF CEE GRADUATE EDUCATION ISSUE. THIS ISSUE CONSISTS MAINLY OF ARTICLES ON GRADUATE COURSES WRITTEN BY PROFESSORS AT VARIOUS UNIVERSITIES, AND OF ADVER TISEMENTS PLACED BY DEPARTMENTS OF CHEMICAL ENGINEERING DESCRIBING THEIR GRADUATE PROGRAMS. IF YOU WOULD LIKE TO PREPARE A PAPER FOR THIS ISSUE PLEASE WRITE RAY FAHi EN, EDITOR, CEE C / O CHEMICAL ENGINEERING DEPARTMENT, UNIVERSITY OF FLORIDA, GAINESVILLE, FL 32611 OR CALL (904) 392-0861. 59


MOLECULAR THERMODYNAMICS FOR CHEMICAL PROCESS DESIGN J. M. PRA US NITZ University of California Berkeley, California 94720 T HE IMPORTANCE OF thermodynamics in chemical engineering is so well established that today every undergraduate curriculum in chemical engineering includes at least one course in thermodynamics. Along with a few other sub jects (e.g., transport phenomena, chemical kinetics, etc.), thermodynamics is recognized as one of the scientific cornerstones of chemical engineering science and practice. Thermodynamics is a large subject with many possible applications; this article considers only that aspect of thermodynamics which is particul arly important in chemical process design, viz., calculation of the equilibrium properties of fluid Since the Scatchard-Hildebrand equation is not highly accurate, the design engineer faces the embarrassing problem of not knowing if the benzene comes out overhead or in the bottoms. mixtures, especially as required in phase-separa tion operations. Design of most chemical processes requires at least some phase-equilibrium calcula tions since such processes, with rare exceptions, include separation steps effected by diffusional operations such as distillation, extraction, etc. While the technical importance of thermo dynamics is recognized by all chemical engineers, and while its intellectual eminence is duly recognized by chemical engineering professors, its practice by industrial design engineers, un fortunately, is often limited. This limitation is certai1ily not caused by any lack of books or articles since our library shelves groan with 60 publications on thermodynamics. Nor is this limitation caused by any lack of respect for or recognition of thermodynamics by practicing chemical engineers. Unfortunately, however, many practicing engineers feel a deep frustration when they try to use thermodynamics for prac tical purposes. The books are full of equations and more equations and still more equations, and while many data are reported in the literature, in a typical practical situation, they rarely per tain to the particular mixture of interest and even then only rarely to the particular desired conditions of temperature, pressure and composi tion. Therefore, many experienced chemical en gineers are disillusioned by thermodynamics; they regard thermodynamics the way a movie buff looks at the latest x-rated movie: it promises so much more than it delivers. Practical use of thermodynamics for phase equilibrium calculations is restrained by lack of appropriate data and by limited availability of methods for estimating needed mixture properties from a minimum of experimental information. Since the number of binary mixtures in current chemical technology is already extremely large, and since the possible number of multicomponent mixtures is large r than the United States national budget expressed in pennies, we may safely con clude that it is not possible that we shall ever have enough experimental data to satisfy all our needs. On the other hand, it is also unlikely that within the normal life span of even our youngest colleagues we shall be able to calculate thermo dynamic properties of multicomponent liquid mix tures from a fundamental theory, that is, by solv ing the Schrodinger equation. Clearly, therefore, it is necessary that we interpolate and extra polate limited experimental data to estimate the information needed for designing a particular process or a particular processing unit. To per form such interpolations and extrapolations, we require models and, to assure that these models CHEMICAL ENGINEERING EDUCATION


provide reliab l e answers, it is essential that they be based as much as possible on our growing knowledge of molecular behavior which, in turn, is expressed in macroscopic terms through sta tistical mechanics. When classical and statistical thermodynamics are combined w i th mo l ecu l ar physics, physical chemistry, limited experimental data and an efficient computer progra m we ob tain applied molecular thermodynamics. The pur pose of this engineering too l is to provide the chemical engineer with the techniques that he needs to give him the equilibrium information required for process design. To illustrate how molecular thermodynamics can he l p to solve engineering prob l e m s, four examples are briefly described in the following paragraphs. Each example refers to a real in dustrial situation. RECOVERY OF BENZENE FROM A DILUTE SOLUTION OF SATURATED HYDROCARBONS J N A REFINERY, a stream containing primarily C 6 saturated hydrocarbons also contains ben zene in low concentration This stream is blended with others for making gasoline but, considering the rising price of benzene, it appears to be economical to remove the benzene by distillation prior to blending. The obvious question facing the design engineer is: What is the volatility of benzene (B) at high dilution relative to hexane (H)? To obtain a reasonable first estimate we can calculate the activity coefficient of benzene using the Scatchard-Hildebrand equation as out lined in Figure 1. When we do so, we find that ' All symbols are defined at the end of the article B = Benzene H = Hexane pS = Vapor Pressure Y = Activity Coeff i c i en t EXTENDED SCATCHARD H I LDEBRAND THEORY CO VB [ 2 ] I n y B = R T (898H) + 2 JI 888H ( b.Evap)l/2 8 = S olubil it y Pa r a m eter = -v[ 1 /2 ( b.Evap) (b. Ev ap) (b.Evap)] ---( 1 J) V BH V B V H In or i g i na l (s i mp l e) theory JI = 0 FIG U RE 1. Rela t ive Volatility of Benzene in Dilute So lution with Sa t urated Hexanes SPRING 1976 20 1 0 I 0 3 JI O t---=--+--------,f-----+---"'0 2 0.4 0.6 0.8 -1 0 -20 -3 0 No. of CH 3 Gro u ps No of C Atoms in Sat u rated Hydrocarbon FIGURE 2 Correlation of Binary Parameter l with Methyl and Me t hylene Structure of Satu rated Hydrocarbon 00 a.n / H is uncomfortably c l ose to unity Since the ScatchardH i l debrand equation is not highly ac curate, the design engineer faces the embarrassing probl e m of not knowing if the benzene comes out overhead or in the bottoms. The key simplification in the Scatchard Hilde brand equation is the geometric-mean assumption which re l ates the cohesive energy density ( 6 Evn11 ) to those of the pure components. This V BH assu m pti o n can be relaxed by introduc i ng the binary constant l. Fortunately, experimental data for aromatic-saturated hydrocarbon systems are p l ent i ful and therefore it was possible to es tablish a reasonab l e correlation for the binary parameter l as shown in Figure 2 taken from Funk [l]. The deviation from the geometric mean is re lated to the extent of branching of the saturated hydrocarbo n ; the branching parameter, shown on the abscissa, varies from zero ( cyclohexane) to 0.8 (neopentane). Since the relative volatility depends not only on the solubility parameters, but a l so on l, to make rational design calculations, the design engineer must have some information on the extent of isomerization (branching) of the saturated-paraffin stream. With this information, parameter l can be estimated. Using Figure 2, it was possible to design the column with confidence and its performance corresponded fully to design specifications. MODIFICATION IN THE AMMONIA-SYNTHESIS PROCESS T HE CONVENTIONAL HABER process for synthesizing ammonia from nitrogen and hy drogen must include a purge stream to remove unwanted m ethane and argon, as indicated in the top part of Figure 3. Small quantities of these inert materials unfortunately enter the reactor 61


Conventional N2,H2 (Ar,CH 4 ) Modified N2, H2 (Ar,CH 4 ) NH 3 Recycle Reactor ~250 atm Reactor Recycle ~250 aim Absorber (~90C) Cooler Purge N2,H2, Ar, CH 4 NH 3 FIGURE 3. Modification of Ammonia Process: Reduction of Purge-Gas Losses. and unless they are removed, they eventually ac cumulate to an intolerable level, making the pro cess inoperable. The purge stream, while small, discards appreciable quantities of nitrogen and hydrogen and, what is economically most un attractive, it wastes the work of compression that has been expended to bring the thrown-away re actants to the high pressure at which the reactor must operate. To minimize purge-stream losses, a modifica tion of the ammonia process was suggested by Professor Scott Lynn [2], as shown in the lower part of Figure 3. In this modification the purge stream, at high pressure, is contacted with product liquid ammonia in an absorber, operating near 90 C. The absorber removes most of the un wanted argon and methane and allows most of the wanted nitrogen and hydrogen to be recycled to the reactor with essentially no work of compres sion. The effluent liquid ammonia, rich with argon and methane (and containing also some nitrogen and hydrogen), is then cooled and flashed. The advantage of this procedure is that the energy and material (H 2 N 2 ) loss in the purge stream is minimized. (It may also be possible to recover the argon with subsequent processing, but this is a secondary refinement.) The disadvantage lies in the capital invest ment needed to construct the high-pressure ab sorber. To investigate the economics of this pro cess modification, it was necessary to estimate phase equilibria in the five-component system NH 3 -H 2 -N 2 -Ar-CH 1 at high pressure An experi mental study would require much time and ex pense and the usual thermodynamic methods 62 found in textbooks are of little use here because in this mixture we have one subcritical component and four supercritical components. To make reasonable estimates, Alesandrini [3] used some molecular-thermodynamic tools summarized in Figure 4. For the liquid phase he used a model of the van Laar type, suggested earlier by Chueh [4] and for the vapor phase, a modified Redlich-Kwong (RK) equation of state. This modified RK equation, in turn, was made possible by an earlier study of O'Connell [5] which had investigated the polar and nonpolar interactions of ammonia molecules. Since the pressure is high, the effect of pressure on the liquid phase (Poynt ing effect) had to be taken into account and this, in turn, was made possible by a correlation of liquid partial molar volumes published in 1965 by Lyckman and Eckert [ 6]. The large advantage of Alesandrini's thermodynamic method is that only pure-component and binary data are required to predict the five-component phase equilibria by solving the equations shown in Figure 5. A computer program, containing an efficient itera tion scheme, was used to calculate the equilibria using the thermodynamic tools briefly mentioned above coupled with experimental Henry's con stants for each of the four gases in li q uid am monia; fortunately these were available in the literature. Some typical results from Alesandrini's cal culation are shown in Figure 6. The gas composi tion (NH 3 -free basis) is shown at the top and, in this example, the pressure is constant at 200 atm. The right ordinate shows the overall solu bility and the left ordinate shows the individual solubilities, both as a function of temperature. The mole fraction of ammonia in the gas phase is also shown. A few well-selected experimental Fugacity Coefficient 'P Modified Redlich-Kwong equation of state. Modification based on analysis of potential energy function for ammonia (O'Connell). Partial Molar Volume v Correlation based on cohesive energy density concept (Lyckman and Eckert) Activity Coefficients Y 1 and Yi Modified Van Loar Model (Chueh) Henry's Constant H Reduction of binary NH 3 -solute data FIGURE 4. Calculation of Thermodynamic Properties Needed for Solution of Phase-Equilibrium Equations. CHEMICAL ENGINEERING EDUCATION


NH 3 (I) (Subcritical) P = Pressure x = Male fraction (liquid) y = Male fraction (vapor) T = Temperature R = Gas Constant 'P = Fugacity Coefficient v = Partial Molar Volume Y 1 a Yj = Activity Coefficient H = Henry's Constant Y 1 -1 as YjI as ( r x -o) i~I I FIGURE 5. CALCULATION OF VAPOR-LIQUID EQUILIBRIA FOR NH3-Hz-Nz-Ar-CH4 measurements by Alesandrini served to indicate that the calculated equilibria are sufficiently ac curate for approximate design purposes. With these calculated phase equilibria it was then possible for Professor Lynn to make some economic evaluation of his modified ammonia process. While conclusions are not definite, it ap pears that under some circumstances the modified process may offer appreciable economic advant ages It would have been impossible to make even an approximate economic analysis without some reasonable estimates of the phase equilibria and these, in turn, could only be made because research had previously been performed on pertinent topics in molecular thermodynamics. .,, :c >< z zW -'11, 0 6 0 5 0-4 YNH3 0.016 0.032 0.073 0.148 0.273 P= 200 Atm ,, / / / ,, / ,, / / ,0 3 / >< / / / 0.2l:::.......'.N~2 ___ ...L-,,._+-=c..-.,. ..,. 0.1 _.,,,,,.--,,,,.Ar 0.06 0.04 .., .J :c >< z zt,,,.J -11, 0.03 0 .02 0 01 0 L_.L-_--1.... __. __ -L---'-----::-=-::-' 0 260 280 300 320 340 360 T K FIGURE 6. VAPOR-LIQUID EQUILIBRIA AT 200 ATM (yH2: YN2: YAr: YcH4 = 3.0: I.0:0.18: 0.44) SPRING 1976 DEVELOPMENT OF A DUAL-SOLVENT EXTRACTION PROCESS FOR REMOVAL OF ORGANIC POLLUTANTS FROM INDUSTRIAL WASTEWATERS WAS TEW ATERS IN PETROLEUM refineries and petrochemical plants frequently contain appreciable amounts (a few wt. per cent) of dis solved organic matter; much of this organic matter ( especially phenolics) is offensive in odor and does damage to marine life. To avoid over loading of biological wastewater-treatment ponds, it is often desirable to remove 90 or 99 % of the pollutants prior to biological treatment. The economics of such extraction may be particularly attractive if the recovered pollutants have com mercial value. Wastewater Containing Phenolics Ke tones Aromatic Hydrocarbons Esters Organic Acids Organic Chlorides etc. ~----. Recovery of Solvents and Solutes ----Polar Solvent ( e q., Butyl Acetate) ~--Volat i le Nonpolar Solvent (lsobutylene or lsobutane) "Clean" Wastewater Polar solvent extracts hard-to-get solutes (e q phenolics). Volat i le nonpolar solvent extracts (slightly) water-soluble polar sol vent. FIGURE 7. Dual-Solvent Extraction Process for Waste waters from Petrochemical Plants. To remove phenolics (and other polar organic solutes) from water by extraction, it is necessary to use an organic solvent which is polar; hydro carbon solvents, even aromatics, have low dis tribution coefficients for phenolics and similar pollutants. However, a typical polar organic sol vent is somewhat soluble in water and therefore, while the polar solvent may efficiently remo v e the pollutants, it becomes a pollutant itself. Further, the density of a typical polar solvent is often uncomfortably close to that of water thereby creating mechanical difficulties (flooding) in the extractor at economic flow rates. To circumvent these difficulties, it appeared desirable to consider a dual-solvent extraction process as shown in Figure 7. The primary solvent (e g butyl a c etate) efficiently removes phenolics and many other or ganic solutes but, since the solubility of butyl acetate in water is not negligible, it is necessary to remove it with another solvent which in this 63


case is isobutane or isobutylene. A rotating di s c column (RDC) is useful for this process. Waste water enters at the top and the C hydrocarbon enters at the bottom of the column. Near the middle of the column, butyl acetate is intro duced. Since the density of C 4 is much lower than that of butyl acetate, the density of the organic phase is always well below that of water, allowing relatively large flow rates without flood ing. The highly favorable distribution coefficients for the pollutants, distributing themselves be tween water and the mixed organic phase, permit operation at low solvent-to-water flow ratios. The high volatility of c is also beneficial in subse quent processing steps to recover the solvents The RDC operates at slightly elevated pressures, in the region 40-50 psia. To design this extraction process and to evalu ate its economic potential, it was necessary to ob tain distribution-coefficient data. For a non volatile solvent like butyl acetate such data are obtained easily. But for volatile solvents, distribu tion data must be obtained under pressure and the necessar y experimental work is much more difficult. Nevertheless, an apparatus and pro cedure for obtaining such data was developed by K. W. Won, as described elsewhere [7]. To mini mize the experimental effort, it was desirable to obtain only a few representative experimental results and then to generalize ( correlate) these with the help of molecular thermodynamics A simple technique for achieving at least partial correlation is outlined in Figure 8. The distribution coefficient K consists of two parts : first, the difference in work that must be done to create a hole in the solvent and to collapse a hole in the water as the solvent moves from one phase to the other and second, the difference in attractive energy experienced by the solute as it exchanges its aqueous environment to a hydroq = Size parameter for solute kq=k'q -k"q k'q = Work needed to moke "hole" for solute in water k"q = Work needed to make "hole" for solute in solvent ~U=U'-U" U' = Attractive energy for solute in woter U" = Attractive energy for solute in solvent FIGURE 8. Distribution Coefficient K is Correlated by Perturbed-Hard-Sphere Theory of Solutions. 64 1 000 .-----~-..---~-Ill C (I) ;:; i Cl) 0 u 1 00 C 1 0 0 lso b uty l e ne x lso b ut ane ] f ;:: Ill c 20 25 30 v*0 .7 3 5 4 0 FIGURE 9. Distribution Coefficients K at 25 C for Acetates. Units of V* are cm 3 /mol. (K = moles acetate per kilogram of hydro carbon/moles acetate per kilogram of water). carbon environment. The derivation of the equa ~ion shown in Figure 8 is given elsewhere [7] ; it 1s based on a v ery simple theory of dilute solu tions, which, in similar forms, has often been used in the physico-chemical literature, especially for pharmaceutical applications. For our purposes here, we only want to show how such a simple theory can be used to obtain straight-line correla tions for different solute families as shown in Figures 9 and 10 where size parameter q has been r eplaced by (V*) 0 7 The solute-size para meter V is obtained from fundamental pure component thermodynamic data. The exponent 0.7 was chosen because it is not clear whether the work to create a hole is proportional to the size V or to the surface area which, at least for spheres, is given by (V ) 2 /3. Empirically it was found that 0.7 gives the best straight-line correlation for the solutes considered in this par ticula r extraction process. Figures 8, 9 and 10 illustrate that simple molecular ideas can reduce experimental effort by providing a reasonable basis for interpolation and extrapolation of limited experimental data. Bench-scale pilot plant studies by Earhart [8] have shown that the extraction process out lined in Figure 7 has considerable potential for economic wastewater treatment. C HEMICAL ENGINEERING EDUCATION


OPTIMIZATION OF THE SEPARATION STEP PRIOR TO RECYCLE OF ETHYLENE IN THE HIGH PRESSURE PROCESS FOR POLYETHYLENE JN 1974, ANNUAL production of polyethylene was slightly in excess of four million tons. Much of this polyethylene is made by the high pressure process, shown schematically in Figure 11. Per pass, the conversion of ethylene to poly mer is in the region 10 30 % and it is therefore necessary, at the reactor outlet, to separate un reacted ethylene from the product stream, prior to recompression and recycle. Separation is easily achieved by decompression since the solu bility of ethylene is strongly pressure-dependent. The lower the pressure in the separator, the better the separation. But the lower the pressure "' ... C QI ;:; QI 0 u 0 C .!:! "S .a ;: .. "' Q lsobutylene 1 00 x l so butan e 10 1. 0 ti -'ii N C l ,: 0 I L-..L....--L-'--..L.......LL-J.J.........J 20 2 5 3 0 35 v ,..O 7 FIGURE 10. Distribution Coefficients K at 25 C for Ketones. Units of V* are cm 3 /mole. (K = moles ketone per kilogram of hydro carbon/moles ketone per kilogram of water). in the separator, the larger the cost of recom pression of unreacted ethylene for recycle to the reactor. Since energy costs are significant in this process, it is important for optimum design to give careful attention to the pressure at which the separator should operate or, if a series of separators is used, what pressure should prevail in each individual separator. For design optimi zation therefore, it is necessary to have quantita tive information on phase equilibria in the ethy lene-polyethylene system. SPRING 1976 ethylene compressor 1--~-compressor ethylene recycle polyethylene separator reactor (I000-3000 atm) (100-500 atm) FIGURE 11. Schematic Flow Diagram of High-Pressure Process for Polyethylene. If the polyethylene is monodisperse (all poly mer molecules have the same molecular weight), the phase diagram has the general f ea tu res shown in Figure 12. At very high pressures ethylene and polyethylene are completely miscible but, as the pressure falls, separation occurs. At low pressures there is very limited solubility of ethy lene in the polymer-rich phase and essentially no solubility of polymer in the ethylene-rich phase. To obtain a quantitative estimate of the de sired phase equilibria, it is necessary to use a molecular model, in this case, an equation of state suitable for polymer-monomer mixtures at inter mediate and high pressures. The common equa tions of state (e.g., Redlich-Kwong, Benedict Webb-Rubin, etc.) are not applicable here since these are intended for relatively small molecules, not polymers. However, Flory, Patterson and other physical chemists have proposed an equa tion of state based on Prigogine's theorem of corresponding states for chain molecules. This equation of state, shown in Figure 13, can be used with standard thermodynamics to calculate com ponent fugacities and from these, quantitative phase relations can be obtained. The fundamental idea of Prigogine is illustrat2000 E 1500 +0 IOOO => (f) (f) w 500 0 Critical point TWO-PHASE REGION ONEPHASE REGION 0 0-2 0.4 0 6 0.8 1.0 WEIGHT FRACTION POLYETHYLENE FIGURE 12. Ethylene-Polyethylene Binary Coexistence Curve (Constant T & Molecular Weight). 65


v = _y_ v* ~ p p = p* T = T T* v* = Hard-core (van der Waals) volume per segment p"' = S")/2v"' 2 T"' = S")/2ckv* k = Boltzmann's Constant s = Nt1mber of external surface sites per segment ")IV = Potential energy per surface-site contact 3c = Number of external degrees of freedom (trans lation, large-scale rotations and vibrations) Parameters v*, P*, and T* obtained from PVT data FIGURE 13. Equation of State for Polyethylene, Ethylene, and Their Mixtures at High Pressures. ed in Figure 14. In the upper part we show a con tainer of volume V containing Nr monomer mole cules at temperature T. In the lower part we show a container of the same volume V at the same temperature T, containing N polymer mole cules where each polymer molecule consists of r units (or segments); the total number of seg ments, then, is Nr. In both containers, there fore, the density is the same, viz. Nr / V. But clearly there is a difference between the two situa tions. The difference is that in the upper diagram the total number of external degrees of freedom is 3Nr (each molecule has 3 translational degrees of freedom) while in the lower diagram, due to chemical bonding of the segments, the total num ber of external degrees of freedom is smaller. How much smaller? There are 3N translational degrees of freedom but there are also many de grees of freedom due to rotation and vibration of the segments. Some of these are external (i.e., they are affected by the presence or absence of neighboring molecules) while others are internal (i.e., they are independent of density). The total . . ..... ........ .. . . . . . . ..... (Nr) SPHERICAL MOLECULES AT T AND V N CHAIN MOLECULES WITH r SEGMENTS EACH (Nr SEGMENTS) AT T AND V No OF EXTERNAL (DENSITY-DEPENDENT) DEGREES OF FREEDOM 3 Nr (ALL TRANSLATION) 3Nr(f) = 3Nc ONLY 3 N TRANSLATION 0<-%-<1 IF ALL SEGMENTS WERE INDEPENDENT, tWOULD EQUAL UNITY FIGURE 14. Corresponding States for Chain Molecules. '66 number of external degrees of freedom in the lower diagram is equal to 3Nr (c / r) and Pri gogine's theorem of corresponding states assumes that all of these can be treated as if they were equivalent translational degrees of freedom. The parameter c / r lies between zero and unity. If the polymer molecule is stiff (uncooked spaghetti), c / r < < 1 because in a stiff molecule rotations and vibrations are severely limited. On the other hand, if the polymer molecule is highly flexible (cooked spaghetti) c / r may be in the region 0 50.8; only in the limit, when all segments can act independently (all segment-segment bonds are broken) does c / r attain a value of unity. The equation of state shown in Figure 13 con tains three molecular reducing parameters, here called v*, T* and P* ; the first of these reflects the hard-core size of the molecules ( or segments) and the other two, in combination, reflect the characteristic segment-segment potential energy and the "flexibility" parameter c. Numerical This article considers only that aspect of thermodynamics which is particularly important in chemical process design, viz., calculation of the equilibrium properties of fluid mixtures, especially as required in phase separation operations. values of these parameters can be obtained from fitting the equation of state to experimental volumetric (PVT) data which are available for polyethylene and for dense ethylene. The equa tion of state can be applied to mixtures using reasonable mixing rules. In a real industrial situation, the polymer in the product stream is not monodisperse, but poly disperse and, therefore, the mixture is not a binary but a multi-component mixture. A realistic dis tribution of molecular weights of polyethylene is shown in Figure 15 ; this particular distribution is a log-normal distribution whose number-aver age molecular weight is given by M N and whose first and second moments are those indicated. Using the equation of state based on Prigo gine's theorem, the molecular-weight distribu tion shown, and a suitable computer program, it is possible to calculate phase equilibria in the separator [9]. Some results are shown in Table 1 ; these were calculated at 260 C for an entering stream containing 12.5 wt % polymer. At the lowest pressure (200 atm) the separation is CHEMICAL ENGINEERING EDUCATION


"' 0 I ::. 3' MN= 13,170 Mw/MN=IO i.1 2 /Mw=IO MASS=/w (Ml dM 0 .__------'-----"---------'--------' 0 25,000 50,000 75,000 100,000 POLYETHYLENE MOLECULAR WEIGHT, M FIGURE 15. Log-Normal Molecular Weight Distribution. sharp but at the highest (900 atm), the separa tion is poor: the heavy phase retains 21.8 wt. % ethylene and the light phase retains 7.5 wt. % polyethylene. Table 1 also gives the number-aver age molecular weights of both phases (ethylene free basis) and finally, the molecular-weight dis tributions for both phases at 900 atm. are shown in Figure 16. A variety of factors must be taken into ac count by the design engineer toward optimizing the high-pressure polyethylene process. Phase equilibria constitute only one of these factors but surely it is of utmost, indeed essential, importance. The type of phase equilibrium information re quired in this case is very difficult to obtain ex perimentally However, as outlined above, an ap propriate physicochemical model, coupled with a few well-selected experimental data, can provide the design engineer with estimates of the equilibria he needs for making rational de cisions (10). CONCLUSION THE FOUR EXAMPLES briefly described here illustrate how molecular thermodynamics can be of direct use in practical chemical engineer ing. The essential ingredients are classical ther"' 0 I 4000 8000 12,000 16,000 20,000 POLYETHYLENE MOLECULAR WEIGHT, M FIGURE 16. Molecular Weight Distributions in Equi librium Phases (at 260 C & 900 Atm.). SPRING 1976 modynamics, molecular physics or physical chemistry and an efficient computer program; in some cases, but not all, statistical thermodynamics is also required. When we look at the recent work of chemical physicists and physical chemists, we find that every month new quantitative results are reported in a language with which most chemical engineers are not familiar ; as is well known, each pro f esion has its own jargon. The role of molecular thermodynamicists is to bridge the gulf between the needs of the process design engineer and the research achievements of those scientists who dis cover new facts about molecular behavior. This gulf, unfortunately, is increasing. On the one hand, the variety of tools needed by the design engineer is rapidly growing with the size and sophistication of expanding chemical industry, TABLE 1 Effect of Separator Pressure on Ethylene-Polyethylene Equilibria at 260C (Feed Stream Contains 12.5 wt. % Polymer)* 200 500 900 atm. Wt.% of total polyethylene 0.01 0.30 7.50 retained in light phase Wt. % of total ethylene 1.10 4.80 21.8 retained in heavy phase M N in light phase 110 440 2600 (ethylene-free basis) M N in heavy phase 13350 14350 19500 (ethylene-free basis) *Molecular wt. distribution of the polymer feed is shown in Figure 15. and on the other, refinements of scientific con cepts and experimental instruments makes it ever more difficult for nonspecialists to under stand the significance and implications of new scientific insights and discoveries. Historically, it is clear, however, that progress in developing better design tools can come only from a better appreciation of new scientific results, tempered by mature judgment but also propelled by daring initiative. The innovative elements of creative chemical engineering are numerous but, for efficient design of chemical plants, it is evident that molecular thermodynamics is often required to reduce them to practice. ACKNOWLEDGMENT The author is grateful to the 3M Company which spon sors the ASEE Chemica \ Engineering Division Lectureship and, for support of research, to the National Science Foun67


dation, the Environmental Protection Agency, the Donors of the Petroleum Research Fund administered by the American Chemical Society, Union Carbide Corporation and Gulf Oil Chemicals Company. O NOTATION 3c = total number of external degrees of freedom per molecule 6 E vap = energy of isothermal vaporization from the satu rated liquid to the ideal gas f = fugacity H = Henry's constant for a gaseous solute in liquid k k K M N N Nr p p s P q R T T u V V v V V w(M) v* X y ammonia = a proportionality constant (Figure 8) = Boltzmann's constant ( Figure 13) = distribution coefficient for a solute b e tween water and an organic liquid phase = a binary parameter characterizing deviation from the geometric -m ean assumption = number-average molecular weight = number of polymer molecules = numb er of polymer segments (or monomers) = total pressure = saturation (vapor) pressure = a characteristic molecular parameter having units of p ress ure = a molecular size parameter = gas constant = absolute temperature = a characteristic molecular parameter having units of temperature = attractive energy of one mole of solute molecules at very high dilution in a liquid solvent = liquid molar volume (Figure 1) = volume p er segment (Figure 1 3 ) = partial molar liquid volume = total volume (Figure 1 3 ) = characteristic (hard-cor e ) volume, per mole = frequency of molecular weight M in molecularweight distribution = characteristic (hard-co re ) volume p er segment = liquid-phase mole fraction = vapor-phase mole fraction = relative volatility of benzen e infinitely dilute in hexan e = solubility parameter = vapor-phase fugacity coefficient = activity coefficient (norm a liz ed such that y 1 1 asx 1 1) = activity coefficient (normalized s uch that -y 1 1 as x 1 0) LITERATURE CITED 1. Funk, E. W. and J. M. Prausnitz, Ind. Eng. Chem. 62 8 (1970). 2 Lynn S., C. G. Alesandrini and A D. Sherman, IEC P ro c. Des. & Devel.1 2 217 (1973). 3 Alesand r ini, C. G. S. Lynn and J. M. Prausnitz, IEC Proc. Des. & Devel.11 253 (1972). 4. Chueh, P. L and J. M Prausnitz, Ind. Eng Chem. 60 34 (1968). 68 5 Lee, C S., J. P. O'Conn e ll, C. D Myr a t a nd J. M Prausnitz, Can. J. Chem. 48 2993 ( 1970). 6. Lyckman, E. W. C A. E c ke rt and J. M. Prau sn itz, Chem Eng. Sci. 20 685 (1965) 7 Won, K. W. and J M. Prausnitz, AIChE Jou rna l 20 1187 (1974). 8. King, C. ,J ., J. P. Earhart, K. W. Won and J. M. Prausnitz, "Ext ra:: tion of Chemical Pollutants from Industrial Wastewat e rs with Volatile Solvents", report submitted to the Environmental Protection Agency, Ada Oklahoma (1975). 9 Bonne r, D. C., D. P. Malon ey and J. M. Prau sni tz, IEC Proc D es & D eve l. 13 9 1 (1974). Erratum 1 3 198 (1974). 10. Malon ey D. P and J M. Prausnitz, IEC P roc D e s. & Devel. J.5 21 6 (1976) and AIChE Journal 22 74 (1976) [ti N I books received 7 The History of Qucintum Theo ry, Friedrich Hand, translated by Gordon Reece. Published by Barnes and Noble, New York, 260 pages. This book provides a survey of the history of quantum theory for students and those who may not have much knowledge of quantum theory. Elem en tar y G enera l Th er mod yna mi cs, M V. Sussman. Published by Addison-Wesley Publish ing Co., Reading, MA, 444 pages. This book pre sents a broad introduction to thermodynamic thought and methodology, and applications to many branches of engineering and science. P r o ce ss Eng ineering wi th Economi c Obj ec ti i i e, G L. Wells Published by Halsted Press, div. of John Wiley & Sons, New York, 168 pages. This guide to proce ss engineering w ith economic ob jective serves as an introduction and to integrate the fuller instruction available from specialist texts. Professional Obsoles cence, edited by S. S. Dubin. Published by Lexington Books, div. of D. C. Heath & Co ., Lexington, MA, 121 pages. This book is a record of a symposium on com batting professional obsolescence held at Churchill College, Cambridge (1970) under auspices of the Scientific Affair s Office of NATO. Phys ica l P r o per ti es of I n o rganic Compounds SI Units, A. L. Horvath. Published by Crane, Russak & Co., New York, 466 pages. In this book the essential physical properties of thirty one ele ments, and compounds which are needed by de sign engineers are presented in graphical and tabular form. Statistics fo r Te c hnolog y, Christopher Chat field. 1975 reprint of Halsted Press, div of John Continued on page 75. CHEMICAL ENGINEERING EDUCATION


332 of ourpeople left their jobs last year. We'reproud of that record. Job hopping is something we encourage through our Internal Placement Service. We happen to believe our most valuable corporate assets are people The more our people know, the stronger company we are. So just over a year ago we initiated IPS. In the first year, 332 Sun people changed jobs within the system. Here's how it works. Say you re an engineer. You'd like to broaden your experience and feel that you'd make a contribution in Marketing. You check the weekly job opening notices When there's an opening in Marketing you think you can fill, you apply-and get first consideration. You have freedom to experiment and move around at Sun. You learn more and you learn faster. You want to learn more right now-about Sun and IPS? Ask your Placement Director when a Sun Oil recruiter will be on campus. Or write for a copy of our Career Guide. SUN OIL COMPANY Human Resources Dept. CED, 1608 Walnut Street, Philadel phia, Pa. 19103. An equal opportunity employer m/f. A Diversified Energy and Petrochemical Company


,., Na department Worcester Polytechnic Institute And the WPI Plan W. L. KRANICH and I. ZWIEBEL Worcester Polytechnic Institute Worcester, Massachusetts 01609 JF YOU HAD LOOKED in on the chemical engineering department at Worcester Poly technic Institute (WPI) last January you might have seen the faculty members and their wives teaching "far-out" subjects ranging from natural childbirth (Imre and Barbara Zwiebel) and hatha yoga (Wilmer and Margaret Kranich), through Chinese gourmet cooking ( Maria Ma) and pottery (Eileen Weiss) to championship table tennis (Yi Hua Ma and John Meader) and winter mountaineering (Bob Wagner and Joe Kohler). Before you decide that chemical engineering education has gone completely astray under the WPI Plan, you should realize that these are mini courses available during the two weeks of January Intersession along with such subjects as practical chemical manufacture (Zwiebel and Kranich), chemical plant trips (Stan Weinrich), or gas chromatography (Al Weiss). Intersession courses are not required for a ChE degree at WPI ; in fact no specific courses are required. The degree is obtained after satis factory completion of four requirements. 70 An examination which tests overall competency in the major field An independent qualifying project in the major field (MQP) A demonstration of competence in a humanities area An independent qualifying project relating society and technology (IQP) THE IQP THE IQP, OR Interactive Qualifying Project is a new concept which brings learning about the technological society onto a personal level. While there is a tendency to take a ChE problem and evaluate its societal impact, such as "pollu tion control on the Nashua River" or "the effect of the petrochemical industry on Venezuela," often students approach this requirement from a non-departmental point of view. For example, teaching science in the secondary schools to special students involves the analysis of the problem (what makes the situation a special cir cumstance?), the development of a mode of at tack ( e.g., how to "turn students on" to chemistry) the execution of the plan, and the documentation. The final IQP reports are placed on the shelves of the WPI library, open to inspection by the public. CHEMICAL ENGINEERING EDUCATION


One innovative type of IQP takes a group of students to WPI's Internship Center in Washing ton, D C. There under the overall guidance of a resident faculty member, the students work for seven weeks in teams assigned to various agencies, societies, or lobbying groups. The Washington ex perience is preceded by a time of preparation and followed by a time of reporting. THE HUMANITIES SUFFICIENCY T HE HUMANITIES REQUIREMENT may in part be satisfied by passing a series of courses. These courses, however, have to be preselected to form a coherent, thematically related sequence. At the conclusion of this course sequence the students have to fuse together a selected topic, related to their theme, in an independent study seminar, and write a paper on the conclusions of the study. This approach, by design, emphasizes the study of a specific subject in depth rather than samplings of courses in each of the several hu manistic studies. In a recent article in EE (Volume 66, Number 4, page 319, Jan. 1976) members of the WPI Humanities Department faculty described details of the Humanities Sufficiency, at least as it applies to history. Sufficiencies in art, English, history of science, philosophy, music, drama, and foreign languages are also available. THE MQP T HE MAJOR QUALIFYING project (MQP) has already been discussed in this journal (Chem. Eng Educ., Winter, 1974). Students participate in a wide range of experimental, de sign, modeling, and theoretical projects: some work alone and some in groups. Some conduct their studies on campus and some at nearby in dustrial or governmental installations. The mini mum effort by each student is equivalent to full time activity for seven weeks. Most projects are devised in three approximately equal portions of preparation, execution, and reporting. At the end of the preparation stage the students usually write a project proposal describing the purpose and background of the project, outline their pro posed method of attack, and anticipate their re sults with appropriate indication of the intended correlations. At the completion of the project the final reporting is often accompanied by an oral presentation. The written report is deposited in the WPI Library and is open for inspection to the public. SPRING 1976 Education at WPI with its strong emphasis on project work, and individual programs and instruction, requires more faculty man-hours than conventional methods. THE COMPETENCY EXAMINATION E XPERIENCE WITH THE WPI competency examination was reported by Wil Kranich at the Fort Collins National Meeting of ASEE last year This presentation is summarized below with additional material to bring it up to date. The concept of a major examination shortly before expected graduation has long been in use in European universities. In the form employed at WPI, it is intended to test the readiness of the student to enter the profession. Thus it is not a collection of mini-final examinations in course work, but a major open-ended problem dem a nding a broad science background and engineering design creativity. The objectives of the examin a tion are taken from a departmental statement: "The profession al preparation for chemical engineering has not been split into subspecialities, and thus gradu ates are expected to have an understanding of a rather broad field. Chemical Engineers entering the profession should have a capability for solving the problems of the chemical process and related industries, such as the creative, practical, and economical design of plants and individual component units of such plants. This requires the establishment of material and energy balances, the analysis of equilibri a and the evaluation of French graduate students discuss structure of zeolite with Ma and Sand. 71


reaction rate and transport phenomena. Know ledge of physics and advanced chemistry, and the ability to solve problems involving differential equations is needed. The competency examination tests the students' ability to solve problems that are based upon situations which might be encountered in industry by a beginning professional. The central thrust of the examination is on the broad com petence which an industry or graduate school Kohler and Wagner conduct test for carbon monoxide on back packers stove. expects of all chemical engineers." In other departments at WPI, different examinations are provided for subdisciplines, such as materials engineering, power engineering or urban planning. In some cases individual examinations are especially designed for students with unconventional or interdisciplinary fields. For students who wish to be designated as chemical engineers, however, the same examina tion is presented to everyone taking it during any one period. Some optional questions are usually included to allow demonstration of particular competence in special fields. The examination is made up by a depart mental faculty committee of three, a different committee preparing each of the three exams given per year. Each exam is reviewed by the en tire department before it is prepared in final form. The style of several examinations has been similar to that of the AIChE Student Contest Problems-an open-ended problem in an indus trial setting. The four exams given so far have been based on : Copper smelting Coal gasificat ion 72 NOC! manufacture Single-stage production of adipic acid. In each case the process involved has been new to the student, and considerable time is re quired to review chemistry and obtain back ground. For this reason the examination period is the maximum allowed by the college rules-one week. Before a student may take any competency examination, he or she must be judged by the academic advisor as having appropriate prepara tion. This may be obtained by traditional course work, self-study in independent or guided learn ing, or by projects in appropriate fields. After the written exam has been evaluated by the committee, the candidates have individual oral exams which probe more deeply in question able areas. Each student's written and oral per formance is judged as a whole and assigned a passing grade of "distinction" or "acceptable," or is evaluated as "unacceptable," in which case no record is retained. After counseling by the examination commit tee and the student's advisor, and completion of appropriate remedial work, the unsuccessful student may take a later examination or, in rare cases, withdraw from the college. A few students, of course, change disciplines. While it is too early to establish meaningful statistics on examination performance, it appears that about two thirds to three quarters of the students attempting any given examination re ceive passing grades. Faculty and student opinion based on recent examinations is that they achieve their objectives, but at high cost in time and stress on both examiners and candidates. FACULTY INVOLVEMENT AND RESEARCH EDUCATION AT WPI with its strong emphasis on project work, and individual pro grams and instruction, requires more faculty man-hours than conventional methods. Each set of competency examinations for example, requires several man-weeks in evaluation. Project ad vising is costly and can be brought to acceptable levels only when several students work on different phases of a single topic, or when in dustry bears a portion of the cost in off-campus centers (which still require intensive involve ment by WPI faculty). If each student took full advantage of the available flexibility of the program and built a CHEMICAL ENGINEERING EDUCATION


----------------The IQP, or Interactive Qualifying Project, is a new concept which brings learning about the technological society onto a a personal level, while there is a tendency to take a ChE problem and evaluate its societal impact, such as "pollution control on the Nashua River" or "the effect of the petrochemical industry on Venezuela." Often students approach this requirement from a non-department point of view. unique interdisciplinary area of competence, the costs and logistics would become unmanageable. As might be expected, a majority of the ChE stu dents is seeking general education along tradition al lines. Even so, more than the usual effort is re quired of the faculty. In spite of the demands of the undergraduate program, nearly all of the faculty are deeply in volved in graduate education and research. In addition to research projects in the areas listed in the attached table, some of the faculty are involved in other exciting projects. For example : Weiss coordinates a US-USSR co operative program in formose reactions and, to gether with Kranich, supervises projects in catalytic detoxification of pesticides, and hydro liquefaction and gasification of solid wastes. Ma, in addition to his studies of multicomponent diffusion in porous media, conducts research in microwave vacuum freeze drying. Sand is in vestigating methods of synthesis and modification of ~eolitic materials. Zwiebel i s co-investigator of a binational research project dealing with the removal of sulfur from the products of coal gasi fication, and is concerned with the hybrid comWeiss watches visiting Russian scientist at console of interfaced chromatograph-mass spectrometer. puter solution of systems of partial differential equations. Kohler is studying the generation of methane from sewage and reactions of supported enzymes. Weinrich is working on the implemen tation of the department's newly acquired mini computer in the proces s control areas and for data acquisition in the various research projects The current level of industrial and governmental support of research exceeds $200,000 annually. The educational climate is greatl y enhanced by frequent visitors to the Department, the active Colloquium Series with monthl y presentations by ChE's in all walks of professional life, and v isit ing faculty and research associates from abro a d For example, during the 1975-76 academic ye ar each of six foreign visitors spent six to ten months lecturing in courses and doing research in our laboratories. In addition to teaching underg ra duate proj ects, r esearch and consulting, faculty memb er s maintain high levels of profes s ional standards. Membership in AIChE, ASEE, ACS, and oth e r s ocieties, regular attendance at meetings, partici pation in committees, as w ell a s involvement in civic and community activities are important functions in the educational process. We expect students to become acquainted with the faculty even outside the cla s sroom Facilitated by the projects, nearly individu a lized conta c t, often at the WPI Pub, is the r ule r a ther th a n the exception. The diverse non-professional activitie s of th e faculty include frequent hikin g e x peditions led b y Wagner and Kohler. In athletic c ompetitions St a n Weinrich and Joe Kohler a r e the D e partment a l r epr es entatives on the tenni s o r basketball cou r t s Music a l and artifltic ende a vo rs a re fo s tered b y Wil Kranich with hi s member s hip in th e W o r cester Chorus and the paintin g s and c o nstr u ct ions which adorn his office wall s Zwiebel "wa ste s" his time with bridge, st a mp s and talmudic s c h ol a rship. And, at la s t, the in g redi e nts to g ood who l e some living w ill be p r o v id e d b y the n ew e s t C ontinued on page 93.


laboratory SAPONIFICA TION OF ACET AMIDE IN A BATCH REACTOR S. W. WELLER State Uni v ersity of Ne w Yo r k Buffalo, NY 14214 JN DECEMBER 1974, Dr. E. 0. Eisen reported at an annual meeting of A.I.Ch.E. the results of a survey he had made on the teaching of under graduate kinetics [l]. Of those departments re porting the use of a laboratory experiment il lustrating homogeneous kinetics, most utilized either (a) the hydrolysis of acetic anhydride or (b) the saponification of a carboxylic acid ester such as ethyl acetate. We have refrained from the use of acetic an hydride by undergraduates because of the lacry matory and vesicant action of this material. Our own experience with ethyl acetate, over a period of several years with students, is that the saponi fication proceeds so rapidly, even in dilute solu tion at room temperature, that quenching of the reaction for subsequent titration of unreacted base is difficult to conduct reproducibly. As a re sult, wide variations in rate constants were re ported by different undergraduate groups in our laboratory, and attempts to determine an activa tion energy were hopeless failures. The purpose of this note is to report some work, apparently successful in the hands of st udents, on another reaction that can be useful in an undergraduate chemical engineering labora tory. The reaction is the saponification of aceta mide in aqueous solution : C H a CO NH 2 + NaOH C H 3 COO Na+ NH a (1) The reaction is effectively irreversible and is second order. Data on the second order rate constants are available in articles by Willems and Bruylants [2 ] and by Laidler and Chen [ 3]. Students are given these references in the laboratory instructions, with the note that the 1951 article is more di rectly useful for elevated temperatures. Interest74 ingly but not surprisingly, only one group of students has ever chosen to refer, in their labora tory report, to the article in French. The saponification of acetamide is much slow er than that of ethyl acetate, and it is convenient to conduct the reaction at modestly elevated temperatures, in the range of 40 to 80 C. This fact helps in quenching the reaction when aliquot samples are taken for analyses at room tempera ture The large difference in rates is illustrated by the data of Laidler and Chen: at 25 C., the rate constant is 8.0 x 10 2 z mole 1 sec 1 for the hydrolysis of ethyl acetate and 3 .77 x 10 5 z mole 1 sec 1 for the hydrolysis of acetamide. The results of Willems and Bruylants on acetamide, obtained over the temperature range 65 to 85 C lead to 2 6 2 2 QJ 0 E ...... ,._ 2 -_1.8 ::c 0 0 z u 1.4 40 0 0 80 I, minute 0 120 FIGRUE 1. Second-order rectifying plot for the saponi fication of a cetamide at 47.5 C. CHEMICAL ENGINEERING EDUCATION


Sol Weller did his undergraduate work at Wayne and obtained his Ph.D from the University of Chicago in 1941 under the Nobel Prize winner in physics, James Franck. After se r ving the N.D.R.C. and the Manhattan Project during W.W 11 he conducted research at the Bur eau of Mines. He was head of fundamental research at Houdr y Process Corp., then he joined the Aeronautic Division of Ford (later Philco-Ford). He came to SUNY / Buffalo in 1965 as pro fessor of chemical engineering. He has contentedly pursued research in kinetics and catalysis in Buffalo since then except for pleasant interludes as visiting professor at Berkeley U N technical expert in Haifa, and Fulbright lecturer in Madrid the following expression for the rate constant: k = 9.55 x 10 5 exp (-14,200 / RT) (2) This is also consistent with the 25 value of Laidler and Chen. We have found it convenient to use a solution that is initially lM in both acetamide and sodium hydroxide, prepared by mixing equal volumes of the corresponding 2M solutions. The batch re action is conducted in a multineck flask, im mersed in a thermostatted water bath, and equipped with a variable speed stirer; 0.1 N HCl and NaOH are used for the determination of un reacted NaOH in 2 ml. aliquots, removed periodically by pipette. Some feeling for the fre quency of sampling can be obtained by observing that the half-time for reaction at 50 C., for an initial concentration of lM for both reactants, is about 1.2 hr. Since the reactants are present in equimolar ratio, the rate constant is evaluated by any standard rectifying plot: e.g., 1 / C Na oH vs t. Figure 1 shows such a plot for a run conducted at 47.5 C by a student group. The slope cor responds to a value of k = 1.10 x 10 2 l mole 1 min 1, or 1.83 x 10 c1 l. mole 1 sec1 Some of the important sources of error are : Preparation of the stock solution of aceta mide by weighing directly from the bottle Aceta mide is hygroscopic. If concentration is to be de termined by weight, the material should be SPRING 1976 -----------------vacuum -d ried first (m.p. = 82 C) Alternately, the concentration may be determined by allow ing the alkaline hydrolysis with a known excess of NaOH to proceed to completion, with subse quent titration of residual alkali Non-reproducible technique in the use of a 2 ml. pipette. (Practice with this might be edu cational for the chemical engineering student who lacks prior exposure to an analytical chemistry l a boratory.) Failure to equilibrate the two initial solu tions at reaction temperature before mixing. One caution: NH is slowly produced in the reaction. The laboratory should be adequately ventilated, therefore, especially when the reac tion is run at temperatures above 50 ACKNOWLEDGEMENTS The experimental data show n in Fig. 1 were obtained by Guy Jamesson and Mahmood Jawaid, whom the author was delighted to have as students. D REFERENCES 1. Eisen, E. 0., Minis e ssion on T e aching of Undergradu a te Reaction Kinetics AIChE Meeting, Washington, D.C., December 4, 1974. 2 Willems, M. and Bruylants, A., Bull. Soc. Ch i m. Belg. 60, 191 ( 1951). 3. Laidler, K. J. and Ch e n, D Tran s Far. So c 54, 1026 (1958). BOOKS RECEIVED Continued from page 68. Wiley & Sons, New York, 359 pages. The purpose of this book is to acquaint the reader with the increasing number of applications of statistics in engineering and the applied sciences. Patterns of Problem Sol v ing, Moshe F. Rubin stein Published b y Prentice-Hall, Inc., Englewood Cliffs, NJ, 544 p a ges. The material in this book was developed while teaching a compus wide in terdisciplinary course, "Patterns of Problem Solving." The book attempts to provide the read er with tools and concept which are most produc tive in problem solving and are least likely to be eroded with the passage of time. Thermoplastics Properties and Des i gn, Edit ed by R. M. Ogorkiewicz. Published by Wiley Interscience, New York, 248 pages. This book sets out to provide an understanding of the principles underlying the properties of plastics, and also of the design problems associated with plastics in a way that will appeal to designers and engineers. D 75


(D pl classroom INSTRUCTION BY THE PSI METHOD IN A REQUIRED SENIOR COURSE DAVIS W. HUBBARD Michigan T e chnologi c al Uni v ersity Houghton, Mi c higan 49931 THE PSI METHOD of self-paced instruction introduced by Keller [1] has been gaining favor in higher education. Courses are being taught by this method at more than one hundred institu tions. The National Science Foundation has spon sored PSI workshops, and the Center for Per sonalized Instruction was organized at George town University in Washington, D.C. a little over a year ago. The American Institute of Chemical Engineers is becoming involved through the Modular Instruction Task Force-a subgroup of the CACHE Committee-sponsored by the Na tional Academy of Engineering. There are three important features of the PSI method-mastery orientation, self-paced study, and individual attention. Instruction is based on all students mastering all of the course ma terial. How well this is achieved will be indicated by dat a showing the results from two years of the course operation. The students learn at their own rate from a textbook, from supplementary material prepared by the instructor, and by con sulting with their fellow students and with staff members. The course material is divided into study units, and each student receives a study As in many courses taught by the PSI method, a few lectures are given to stimulate interest and for general information. These lectures do not deal specifically with any of the course objectives. guide for each unit. The study guide contains a list of objectives for the unit, a suggested study procedure, and some questions or problems. When the student decides that he has satisfied the ob jectives for a unit he asks for a quiz. The quiz covers all the objectives of the unit. The quiz is graded immediately when the student finishes. 76 TABLE 1 CM416 Process Dynamics and Control 1. Ordinary differential equations 2. Feedback control systems a. Conservation of mass and energy b. Feed back c. Block diagrams 3. Laplace transform techniques 4. First-order system response a. Transfer functions b. Time constants 5. Higher-order system response 6. Closed loop system operation 7. Control valves and controllers 8. Closed loop system response 9. Analog computer techniques 10 System stability 11. Root locus plots a. Stability b. Response In order for a student to pass a quiz, the work must be entirely correct. The student is allowed to correct minor errors which he discovers during the grading process. If a student does not pass a quiz, another quiz covering the same ob jectives may be taken after a suitable study period. The instructor does not transmit informa tion by lecturing and is free to help individual students who have learning difficulties or who have questions about the course material. These general features of the PSI method are often modified to fit the needs of individual courses or instructors. At Michigan Tech, the PSI method was chosen for the process dynamics and control course, because it simulates the employment en vironment much more closely than does a course given using a lecture format. In an employment envrionment, people learn at their own rate by reading and by consulting with colleagues. The course in question is based on the text by Coughanowr and Koppel [2 ] and comprises the mixture of mathematics, response topics, and hardware topics usually covered in a ten-week term. A brief outline of the course is given in Table 1. This course is a required course for CHEMICAL ENGINEERING EDUCATION


seni o r ChE students. Since it is offered on l y once each year, students have good incentive to com plete the course. In this respect, it is j ust l ike any other senior ChE course at Michigan Tech This required course is followed by an el ective course covering frequency res p onse a n a l ysis, contro ll er construction, and advanced to p ics. T he elective course is taught using the nor m a l recita tion method, and there is a laboratory associated with it. The unit operations course is recom m end ed as a prerequisite for the first course, but third year ChE students and electrical eng i neering students have co m pleted the course successf u lly. Tutors are available ten hours each w e ek for quizzing and consultation. Students enro lle d in the course usually are unable to use a ll of t h e available hours because of conflicts with other courses. There is a paid graduate teach i ng assis tant to help with grading and course ad mi n i stra tion. Students enrolled in the course may also serve as tutors if inv i ted to do so. The grading load is heavy, and assistance is necessary for 4 0r------------"' 30 ... z "' 0 :, ... 1 9 7 4 = "' ... 20 0 1 973 = ... z "' .., 0: 1 0 "' .. 1. 8 2 0 2 2 2 4 2 6 >2.6 QUIZZES PER UNI T C OMPLETED FIGURE 1 Frequency Chart for Quizzes per Unit. smooth administration. More than 600 individual quizzes must be graded for a class of 40 students. This means that using the PSI method is quite time consuming Figure 1 shows data for the number of quizzes taken per unit Most students seem to take between 1.0 and 1.5 quizzes per unit The mean was 1.2 in 1973 and 1.6 in 1974. This indicates some false starts but not too many Students apparently are diligent in their study before requesting a quiz. They do not see m to take a quiz just to determine the nature of the questions A FEW LECTURES A S IN MANY courses taught by the PS I meth od, a few lectures are given to stimulate inSPRING 1976 1 2 0 10 UJ IUJ 8 -J

ILi 0 < a: C> 50 C> :z > ;:;:; <.J ILi a: Iz ILi <.J a: ILi Q. 0 ,.:.: -:;:,.: . ~; ,;'} ;;; A 1974(PSI) 1 973(PSII D 1 97 1 (LECTURE) B C D F GRADE ASSIGNED F I GURE 4 G r ade Distributions three different students are plotted along with the recommended progress. The average progress for the class is shown in F i gure 3 along with the r e commended progress. It is typical of PSI courses that the average progress falls short of the recommended progress. For example, Phi l ippas and Sommerfeldt [3] find this for an elementary physics course The data in Figure 1 show one in teresting thing. In 1973, no penalty was assessed for units completed late. General student opinion was that there ought to be a penalty for being l ate In 1974, a mild penalty was established. The data for the average progress show that the penalt y had little effect Grades are assigned acco r din g to the point scale shown in Table 2. An "A" is awarded if a student obtains 85 percent of the maximum TABLE 2 CM416 Grading Scale A+ A B C D F 2 0 0 171 128 96 63 63 number of points, a "B" if a s tudent obtains 63 percent, a "C" for 4 9 percent, and a "D" for 31 percent The system for awarding points is shown in Table 3. This point system seems to provide TABLE 3 CM416 Point System Pass a study unit ___________ _______ + 10 Pass a study unit early ___ ____ _____ + 1 Pass a st u dy u n it late ________________ 1 Assist as tutor (2 hours) __________ + 1 Fi n al Examination _______ (Score x 68) 100 7~ a balance of incentive and penalties which stimu late most students to progress through the course at a reasonab l e rate. Having a penalty associated with passing a unit late means that the course is not truly a "Keller Plan" self paced course. INCREASED COMPETENCE T H E GRA D E DIST R IBUTION data reported in Figure 4 show that there is an overall in creased co m petence at the end of t h e course com p ared to the same course taught by the lect u re me t hod in 1971. The grade distributions show one effect of the penalty for completing units late. When no p e na l ty was assessed in 1 9 73, there were roughly twice as many A's awarded as B's. The 100 >z < :z 80 < <>: :c C> I:z -a: >1&.1 <1:C < 60 ILi "'a: IC> z Lo.Ill: co :::, 1o ,.j "'Ia: 40 ~ _J 8 O < Ul :::, i-oc ~L&JUJ 20 UL&J~ a: <.J a:o"' Lo.loo... 0...Ul Ul 0 0 , \ \, \ ... ,::; 1 974 { PSI ) I / ~. "-:. .. ... ... \ :. ', /1973/P S I) 1971 (LE C TURE)~ . > ', .. .. \ \ . \ .. \ I L \ . ', .. . \ \ -~ 1\ -:-: 20 40 60 80 100 RAW S CO RE FIGURE 5. Final Examination Raw Score Di st r i butions. situation is exactly the opposite for 19 7 4 when the pena l ty was begun. T he grade distributions also show an effect which may be typical of required courses taught by the P SI method compared to required courses taught by the lecture method F or a PSI course, a greater number of students earn A or B than for a lecture course. For a PSI course, which is required in the curriculum, the number of students earning F is small b u t significantly greater than for a lect u re course. It may be that in a lect u re course students who hav e difficulty working inde p endently will l earn so m e thing just by attending class These students will be unable to begin in a PSI method, can drop the course if they are unable to get started T he drop rate for the required process dynamics and control course is between six and twelve percent CHEMICAL ENGINEERING EDUCATION


"' ,_ z L,J 50 0 ::::, ,_ "' "0 ,_ z L,J 0 "' L,J Q. 0 0 1974 = 1973 = 2 3 4 5 6 7 8 9 10 11 12 NUMBER OF UNITS COMPLETEO FIGURE 6. Frequency Chart for the Number of Units Completed. compared to a 29 percent drop rate for a senior biological sciences elective course and a 20 percent drop rate for the required dynamics course offered in the sophomore year. [4] Both the latter courses are taught using self-paced methods. For the dynamics course, students also have the op tion of taking the course by the lecture format. For the process dynamics and control course, the final examination is a comprehensive examina tion covering a sampling of all objectives. The score counts a little more than one-third of the final grade. The raw score distributions for the PSI course and the lecture course are compared in Figure 5. Nearly the same final examination was given for both courses. However, the examinations for the PSI courses covered some what more material and were closed book examinations. The examination for the lecture course was an open book examination. These data show that students who have studied by the PSI method do just as well if not better on written examinations as do students who have studied by the lecture method. In the range of raw scores between 30 and 75, the students who studied by the PSI method had generally higher scores than the students who studied by the lecture method. In the higher range and the lower range of raw scores, there does not seem to be much difference between the two groups. In Figure 6, frequency data for the number of units completed by the end of the course are shown. Most students complete eleven or twelve units in the time allotted for the course. Com paring the data for 1973 (no late penalty) and 1974 (late penalty) shows again that the penalty for passing a unit late has no significant effect. Correlations of final examination score with number of units completed presented in Figure 7 show that lower examination scores are typically SPRlNG 1976 associated with a smaller number of units com pleted though there is considerable scatter. The examination grades range downward from the perfect correlation line passing through the origin and a raw score of 100 for a student com pleting all twelve units. The data presented in Figure 8 show that no student who completed all units earned a "C" and that no student who did not complete all units earned an "A". QUESTIONNAIRE RESULTS AN OPINION questionnaire was employed during 1973 and 1974 to obtain student ideas about the course. Students generally feel that the objectives are clear and related to other courses and to professional practice. They are favorably disposed toward the textbook, the quizzes, and the LL.I a:: 0 100------------_,._ 1974 I <.> 50 (/) I I LL.I a:: 0 (.) (/) 0 "--'--_..____.___,___._____.__,'--..,__....._ ........ __.___,_-J 0 2 4 6 8 10 12 UNITS COMPLETED 100 .-------------I 1973 50 .. I I 0 kC..-L-_..__..L-_.___,__,___.____.___.--''--L-....__, 0 2 4 6 8 10 UNITS COMPLETED FIGURE 7. Examination Score Correlations. 12 Continued on page 101. 79


rtn ;I views and opinions AN IVORY TOWER MAN DINES IN THE REAL WORLD R. J. ROBERTUS Washington State University Pullman, WA 99163 THE FAMINE BE COMING A UNIVERSITY professor immediately after receiving a doctorate degree can be an uneasy experience. All those years in graduate school flood the mind with differential equations and FORTRAN programs. Bounda ry layers, laplace transforms and digital computers become a way of life. Little time is spent worrying about why pumps cavitate, why heat exchangers leak, why bearings fail, why pipelines corrode away or why reactors plug. Even less time is de voted to solutions to the above problems. The rea son is simple. Popular text books rarely discuss them. Chemical engineers with bachelor's degrees are confronted with these problems daily. A use ful education for them demands that their instruc tors know the answers to such questions and relate the importance of such "mundane" problems. Graduate students on assistantships or fellow ships seldom worry about financial red tape. Their advisers take care of that. The paycheck somehow gets home every month. The student researcher's mind can't be cluttered with priorities, justifica tions, budget estimates, transfer of funds and similar monetary considerations. In industry, making a profit for stockholders is the primary justification for existence. How money is handled determines whether it's a steak or hamburger year. Engineers must help decide how much and where money is spent. Instructors who don't know can't tell students. The above paragraphs are not meant to unduly criticize the educational system per se. The point is that industrial experience is essential for any instructor who is preparing students for an engi80 neering career outside reesarch. Getting this ex perience without giving up teaching altogether is a difficult task in many universities. FOOD FOR THE HUNGRY THE AMERICAN SOCIETY for Engineering Education (ASEE) sponsors a Resident Fel low Program just for engineering faculty want ing 12-15 months industrial employment. Research work is discouraged and "real-life" experiences are top priority. Industry pays the Fellow's wages, while ASEE picks up moving expenses from and to the university. Employment depends on com pany / faculty match of interests. Luckily, Stand ard Oil Company of California was willing to hire this writer. THE MENU Few of the problems discussed required extensive calculations for their solution. Some of the day-to day problems, however, do require mathematical treatment. WORKING IN A LARGE industry for one year (365 days in this case) can be handled in dif ferent ways. The Fellow can spend short periods of time in many different areas, thereby gaining lots of superficial knowledge about an entire com plex operation. Benefits to the Fellow are many but the employer gets little return for his invest ment because time spent in any one area is too short. A second approach is to treat the Fellow as an ordinary employee and have him become inti mately familiar with one or two plants. He may CHEMICAL ENGINEERING EDUCATION


not see the entire manufacturing complex but should be quite valuable to the company before he leaves. Other options such as assignment to de tailed design projects are also available. Personal preference of the Fellow and company needs de termine the final choice. HORS D'OEUVRES Before an engineer can do meaningful work for a company, he must learn a few things about the firm or unit where he is employed: Where is technical information located? (Don't underestimate the yellow pages!) Who are the company experts in specialized areas? How are equipment files organized? What paper work is required to get work done in the field? Who sets priorities on field work? How are materials ordered and delivered? How are contracts written, approved and executed? What are the safety requirements set by the company? How is money obtained for expen s ive maintenance projects? What levels of approval are needed for capital expendi tures? What are the lines of communication, i.e., who is sup posed to know what you're doing? Answers to all these questions will vary from company to company, but they are facts which every engineer needs. THE MAIN COURSE MOST OF THE JOBS discussed below were problem types assigned to the author or any engineer in manufacturing. Some solutions are given. At times no solutions were found. None of the work items were textbook problems with an swers in the appendix. They are discussed briefly in order to show future Fellows the variety of problems to which they can be exposed. Industrial readers should note that a Ph.D. doesn't immunize an engineer from dirt and grease. Student readers will guess that even professors can't solve all their problems. Leaks around stems and bonnet gaskets of valves are never-ending problems. Replacing pack ing and gaskets is straightforward if the valves can temporarily be taken out of service. New seal ing materials are often tried on repeaters. Grafoil (a patented Union Carbide form of graphite) is the latest wonder product in many applications. On occasion, a leaking valve can shut down an en tire plant if it can't be isolated. Other times, speSPRING 1976 cial clamps must be designed so a heat-setting ma terial (like Copaltite) can be pumped inside the clamp to surround the leak. As the Copaltite sets up it stops the leak. (This solution works only on valves handling hot stock ... that should have been obvious) Erosion / corrosion of trim in valves can be tough to stop. Deciding if corrosion is the primary factor often requires detailed metallurgical anal yses. Materials selection is not a cut-and-dried procedure. Exotic materials are expensive (carbon steel is getting that w ay) and may not give ap preciably longer life Past experience can be the best guideline When erosion is the real problem, hard-surfacing the wearing parts may be the an swer Other times, changing the style of trim will A useful education for B.S. ChE's demands tha t !he i r instructors know the answers to such pract i cal ques t ions and relate the importance o f such "mundane" prob l ems. help. Really bad cases require replacing the entire valve with one of suitable t r im and material. Piping flange leaks have many causes but no cheap solutions once they start. The most common cause is dirt on the sealing surfaces Poorly made gaskets and improper bolt-up are other culprits. Short spools which don t line up perfectly in tight spaces can induce strains which prevent proper seating of the gasket. Also, designers sometimes follow codes too explicitly so that not enough extra "beef" is available. As a result flanged joints can't take the strain for a variety of reasons and leak. The unfortunate cure for many leaks is to shut down a large section of a plant until the gasket can be replaced or the seating surfaces re machined or the piping s ystem modified. Once in a while a special clamp plus C opaltite will seal off the leak. If a particular flange leaks repeatedly after start-ups, it's time to c onsider a new-style gasket. In extreme cases, flanges may be welded or removed and replaced with a straight piece of pipe. Seal and / or bearing failures in pumps, tur bines or compressors are fre q uent headaches. Fri day evening is the most common time for these oc currences. Improper type of lubricating oil is sel dom the problem. Misalignment, inadequate flush to the seals or too little oil cir c ulation to the bear 81


ings is the usual cause. Old age is another if a pump gets overlooked on the maintenance sched ule. Cures range from in-kind replacement to com plete modification of the seals and seal flush sys tem and / or oil lubrication system. Few of the problems discussed so far required extensive calculations for their solution. Some of the day-to-day problems, however, do require mathematical treatment. Sizing pipelines for vents or recycle streams is a familiar calculation. Cal culating maximum operation temperatures for re action vessels is done periodically, particularly if part of a refractory lining has been changed. Op erating temperatures are normally limited by temperature limits on the shell as set by ASME code requirements. Changing ranges on flow meters and resizing control valves are among the most common calculations made. Energy conservation is even more critical now than in the past. Seemingly small items like re covering condensate from steam traps add up to many dollars in a large plant. Critical evaluation of blowdown systems in plants with several steam boilers can show ways of generating more steam without consuming more fuel. Since furnaces are large consumers of fuel, careful control of fuel/ air ratios (e.g., by installing stack dampers) is al ways economically attractive. Igniting a smoke bomb in furnaces (whose stacks can be sealed off) when they are shut down will show where leaks may exist in the stacks or other seams of the furnace. Unwanted air may leak through the openings during operation. Noise pollution is a real concern, particularly if a plant is close to a residential area. Valves, In graduate school ... little time is spent worrying about why pumps cavitate, why heat exchangers leak, why bearings fail, why pipelines corrode or why reactors plug. compressors and furnaces are all contributors. For new systems, designs can incorporate "quiet" equipment. In existing plants, reducing noise by lagging pipe or adding burner mutes to furnaces is an expensive and marginally effective solution in most cases. In this relatively new field much work remains to be done. Major projects (those with budgets > $50,000) consume about one-third of an engineer's time the 82 first year. Probably the most emotional of projects -and best learning experience-is being a shut down engineer. Preparing a worklist and ordering materials begins two to three months in advance (or sooner now because of material problems). The actual time a plant is down while equipment is being dismantled depends on the size of the plant and the amount of work to be done. Meeting deadlines is a real challenge. Dealing with the un expected is the most exciting aspect of the job. The success or failure of a shutdown engineer de pends largely on his ability to deal with people on the spur of the moment. There is no time to look in a favorite reference book or cite famous litera ture articles. Getting critical materials to the plant site in a hurry is a fun task. Transportation costs often exceed the price of the material. Cannonball express is a very descriptive phrase. A truck can be hired to drive up to 100 miles from the plant to pick up something as small as a valve bonnet gasket. Justification for such delivery expendi tures is simple. Every hour that the plant is shut down beyond the schedule costs hundreds or even thousands of dollars in lost production. The educational (in a textbook sense) part of a shutdown is seeing internals of all the equip ment discussed functionally in lectures. No picture can give the same effect as actually seeing it in person. It's a real eye-opening experience to see an exchanger bundle covered with carbon particles and then find out it was still operating satisfac torily. Equally amazing is seeing a pump impeller corroded so badly it begins to crumble when touched-and then verifying that it was still pumping sour water. Materials availability and price spirals chal lenge the best cost estimators Small amounts of rare metals like lncoloy 825 or Inconel 600 are located in very obscure places. Finding them gives Ma Bell a real shot in the arm. For large amounts, no price can get deliveries speeded up. Companies just wait their turn. Previously abundant things like refractories are being added to the scarce list. Even Tokyo can't supply some varieties in less than three months. DESSERT BESIDES DOING ENGINEERING work, Fellows are exposed to management philosophies and actions through informal luncheons (free!) or committee meetings. Safety, pollution and pub lic relations are high-priority items. The dollars spent to modify equipment which offends nearby CHEMICAL ENGINEERING EDUCATION


Industrial experience is essential for any instructor who is preparing students for an engineering career outside research. Getting this experience without giving up teaching altogether is a difficult task in many universities. residents is nearly unbelievable. Such expendi tures seldom show a return on investment. Working for an oil company during the energy crisis and Arab embargo was prime time for ob serving management and publicity men in action. Statistics in newspapers can be ve r y misleading unless they show the whole picture Getting both sides of the story certainly cleared a lot of fog. Knowing the oil companies' views makes one a believer in energy conservation A LITTLE ALKA SELTZER H EADACHES WERE FEW, but some helpful hints seem in order for future participants to make thinks even smoother. Industry-forget the Fellow has a Ph.D. This can actually be a handicap. He probably hasn't had his hands dirtied by anything more than carbon paper on computer printout. Grafoil gas kets, John Crane 187-I packing, dumdum, Copal tite and Locktite are still Greek the first few weeks. Maintenance people are hard to convince that a doctor doesn't know everything. Bachelors are more easily forgiven for their "ignorance." Keep the man busy. Boredom quickly discourages even the most enthusiastic engineer. Fellows-don t brag about having your doc torate. A 50-year-old machinist with 30 years ex perience knows a lot more about his plant than any book will tell you. Just because a man is old, don't assume he's senile An experienced pipe fitter can help you out of more piping problems than any Reynold's Number-Friction Factor Chart. On the other end, don't think a man your age without a college education must be dumb. Listen to what he has to say-in fact, ask his opinion then thi n k about it. The more people you ask the more apt you are to find the real problem and then its solution. Don't be afraid to admit you were wrong and a less educated person was right. Only God never makes mistakes. Don't fret if all your fancy calculations say something should work, but it doesn't. (Molecules sometimes refuse SPRING 1976 to be ideal gases). Quite often there is no substi tute for "gut reaction" engineering. You did it because deep down inside it felt good. Very few equations have a symbol for common sense, even though it is the most important factor in many solutions Above all, don t expect to acquire a portfolio of problems which can be used as classroom ex ercises. Such is not the point of the program. The non-cookbook problems are most important for rounding out your education. Many will be inter esting tales to relate during lectures but won't be amenable to solution with an HP-35. Life in industry won't be a bed of roses. Some days are boring ; others are frightfully frustrat ing. Most, however, can be quite enjoyable with the proper attitude. MINTS ANYONE? LITERATURE ON THE Resident Fellow Program seems to reach universities through en gineering education magazines. Unfortunately, several large chemical companies were contacted by the author and had never heard of the idea or were not actively involved in it. Benefits to indus try are not just the work a Fellow performs. Good relations can be established with a university and communication lines are opened to express crit icism of graduates and suggest improvements in engineering curricula. These thoughts can be con veyed during, as well as after, the residency. Future success of the Residency Program will depend on greater support by industry. A modi fication worth exploring would be to set up an ex change program whereby someone from industry replaces the faculty member at the university. Caution: University pay scales are significantly lower than industrial ones. GRATUITIES The author wishes to express his sincere and long-lasting thanks to the many employees of Standard Oil Company of California, who made life easier when he didn't yet know which fork to use. Thanks also goes to the American Society for Engineering Education for picking up part of the tab for this most worthwhile experience. D R J Robertus received his B.S (1965) and his Ph.D. (1971) from Montana State University. He has been an Assistant Professor at Wash ington State University since 1970. He was an ASEE Resident Fellow, from August 1973 through August 197 4 His research interests include gas phase combustion kinetics, coal combustion wood particle drying. 83


PACKED COLUMN MASS TRANSFER COEFFICIENTS FOR CONCURRENT AND COUNTERCURRENT FLOW: AN ANALYSIS OF RECENT WORK JOHN D. MILLER, THOMAS R. REHM University of Arizona Tucson, Arizona 85721 THERE ARE CERTAIN advantages to concurrent as opposed to countercurrent flow. The concurrent liquid flow rates need not be as high as those in countercurrent flow. As a conse quence, lower pressure drops over the packed column are found in concurrent flow. Flooding, a change from gas-continuous liquid-dispersed to liquid-continuous gas-dispersed operation, will not occur in a concurrent operation. Although a large uniform concentration difference is more easily maintained in countercurrent flow, a gas liquid reaction can create the same absorption concentration difference even under concurrent flow conditions. The following four papers present recent concurrent flow research. Dodds, Stutzman, Sollami and McCarter (1960) studied the absorption of carbon dioxide by caustic solutions. This was done with concur rent flow and minor liquid partial pressures, but only over-all coefficients, Kga, were reported. They found that above the 99 % significance level, temperature, liquid and gas flow rates, and the type of packing were the only parameters that affected K g a. Their study showed that only under certain conditions was concurrent flow more ad vantageous. Wen, O'Brien and Fan (1963) studied the air-water and air-2.5N Na 2 CO a systems in con current flow using different liquid and gas flow rates, and various packings. They obtained pres sure drop as a function of the above parameters in an empirical expression of the form 6 P = a (L-b) 0 + d lO G. The constants a,b,c,d and e must be evaluated for each packing, as well as for different fluid properties. However, this form 84 could not be directly extended into other packing or fluid systems without further investigation. Reiss ( 1967) obtained ammonia absorption and oxygen desorption mass transfer coefficients for concurrent gas-liquid contacting in packed columns. The experimental mass transfer co efficient for oxygen desorption at 77 F within + 25 % is Kia=0.12 (Ei) 1 1 2 where Ei is the energy dissipation per unit volume, Vi ( 6 P / 6 Z) g He ob tained a similar expression for ammonia absorp tion, but as kga=2.0+0.91 (E g ) 2 13 Although these correlations are for mass transfer coefficients and particular systems, they are not good over ex tended regions of liquid and gas flow rates. The system studied by Ufford and Perona (1973) was one in which gas (CO 2 ) was John D. Miller (Left) rec eived his BSChE from the University of Texas (1970) and MS from the University of Arizona (1973) His re search activities have included crystallization, extrusion and polymer engineering He is currently a predoctoral student at the University of Arizona working on a biomedical / crystallization project. Thomas R Rehm (Right) received his BSChE and PhD from the University of Washington (19 60 ). He is now a professor of chemical engineering at the University of Arizona, Tucson. His research and teaching interests are in applied design mass transfer process instrumentation, and distillation. CHEMICAL ENGINEERING EDUCATION


transferred from a moving gaseous phase ( CO 2 air) into a concurrent liquid phase (H 2 O) in which it is slightly soluble. In this system, as the two phases move through the column, the concen tration of the gas in the liquid phase increases because after the gas enters the liquid, no signifi cant reaction takes place CONCURRENT FLOW DEVELOPMENT BECAUSE OF THE RELATIVE inexperience chemical engineers have had with concurrent flow in packed column applications, it is ap propriate to develop the mass transfer equations that apply in this situation. The development presented here follows that of Ufford and Perona (1973) and, therefore, applies directly to system s of gas-liquid absorption without significant chemical reaction. In terms of measurable concentrations, the r a te of tr a nsport of the g a s into the liquid per unit area of contact, N, times the local inter facial area per unit volume of column, a, can be g iven by Na= k x a(x ix) for the liquid, and Na = k y a(y y i ) (1) (2) for the gas. The mass transfer coefficients in the liquid and gas phases are given by k x and k y respectively. The units of k x and k y are moles per time per area per concentration differences Ufford and Perona (1973) and others have as s umed that the interfacial c oncentrations, Y i and xi are in equilibrium and can, therefore, be re lated to Henry's Law, y = (H / p)x where H is the law constant and P is the total pressure of the system. The interfacial concentrations, y i and X ; are equilibrium concentrations, and, therefore, correspond to equal chemical potentials of CO 2 in both phases at the interface (Treybal, 1968). Since the interfacial concentrations are not measured practically, a more useful relation em ploying the bulk phase concentration, x can be used. In terms of the bulk li q uid phase concentra tion Na= K x a(x -x) (3) w here K x is the over-all mass transfer coefficient. This can be used because x is related to the bulk gas phase concentration, y, through the equilib rium relationship This allows conditions in both phases to be included in the exp r ession for Na. There is also a relationship between the inSPRING 1976 --------------z 2 = Z dz G,y L,x T i ----------z, = 0 Gi, Yi Lj, Xj FIGURE 1. Concurrent flow packed column model. dividual phase coefficients, k x and k y and the over all mass transfer coefficient. Equation ( 1) can be arranged to give 1 k x a (4) Substituting Henry's Law, x i = ( P/ H)Yi and x = ( P / H )Y, and (xi-x) = (x*-x) + (x ,x*), E q uation ( 4) becomes 1 k x a (x -x) Na (P / H) (Y-Y 1 ) 1 P Na = k x a Hk y a (5) Equation (6) represents the over-all resistance to mass transfer in terms of the individual phase resistances. In systems where the gas phase is slightly soluble in the liquid phase, Henry's Law con stant will be large. It can therefore be assumed 85


that there will be negligible resistance in the gas phase. Therefore, the liquid phase resistance would be controlling the absorption process, and therefore Equation (6) may be written as (7) Equation (7) was checked and verified by Ufford and Perona (1973) using a trial and error pro cedure; however, no specific details of the pro cedure were given. This relation has also been verified elsewhere (Koch Stutzman, Blum and Hutchings, 1949). Using experimental data an expression for K x a can be found. Consider a differential section of packed column as shown in Figure 1. It is as sumed that k x and a are the same in all parts of a packed column. The validity of this assump tion depends primarily on the packing size to There are certain advantages to concurrent as opposed to countercurrent flow. column diameter ratio If the column height is more than a few times the column diameter, channeling usually occurs. While operating at steady state, the change in the amount of solute per unit time in the liquid phase in a differential section, ed (Lx), is equal to the transfer of solute into the liquid phase per unit time, K x a (x*-x) eS (-dz). Since the amount of solute in the liquid phase at any point, Lx, increases in the negative z direction, a negative dz must be used. In equation form, without the differential increment, the above statement can be written as (Van Winkle, 1968, p. 619) : d(Lx) = K a(x *x)S( dz) (8) To determine the relationship between x* and x an operating line must be derived which expresses the equilibrium phase concentrations over the entire column. To obtain the operating line a molar balance (no reaction) is written over the top of the column and the differential section This balance may be written as (9) When there is no reaction and the gas is slightly soluble, the changes in the liquid and gas flow rates are negligibly small. The flow rates can 86 therefore be assumed approximately constant, thus G 2 = G and L 2--=-L. Equation (9) may then be written as y = (L / G) (x 2 x) + Y 2 (10) From Henry's Law, the bulk gas phase concentra tion, y, would be in equilibrium with the bulk phase concentration x and thus x* = (P / H)y. Combining this with Equation (10) yields x* = (P / H) (L / G) (x 2 x) + (P / H) y 2 (11) Reiss ( 1967) also used this equation for absorp tion. Defining ( L /a ) ( P / t i) = A as a constant and substituting Equation ( 11) into Equation ( 8) yields, since L is approximately constant, Ldx = K x aS (A (x 2 x) + x 2 x) (-dz) (12) Solving for dz and integrating yields f L f dx -dz= z = K x a:S (Ax +x 2 (l-A)x) (13) With X 2 = 0, integration of the right side of Equation ( 13) yields -L 1 X2 z = K x aS(l+A) n x 2* -(l+A)x 1 Solving this equation for the over-all transfer coefficient gives (14) mass (15) K x a or k x a can be calculated directly from experi mental data using this equation. From Equation (13) the over-all height of a transfer unit (HTU) for the liquid phase is seen to be L Ho L = K x aS and thus, the over-all number of transfer (NTU) is f dx No L = (Ax 2 +x -(l+A)x) such that Z = No L Ho L From Equation (15) it can be seen that (16) units (17) (18) CHEMICAL ENGINEERING EDUCATION


1 X 2 NoL= (A+l) ln X 2 *(A-l)x 1 (20) In comparing Equations (19) and (20) it is ap parent that the only differences are the negative 1 in the (A-1) term and the + sign in the de nominator of the ln function. This is due to the gas stream flowing in the positive z direction. D I SCUSSION THE FOLLOWING discussion will now compare the relative magnitudes of concurrent and countercurrent mass transfer coefficients. For proper comparison, only research on similar systems will be used. Ufford and Perona (1973) experimented with 3 / 4-inch Berl saddles, and 1 / 4and 1 / 2-inch Raschig rings using liquid flow rates up to 66,100 lb / hr-ft 2 and gas rates ranging from 43 to 120 lb / hr-ft 2 Their experiments were done in con current flow, using the COrair-water system. They fit their experimental data to a model that is represented in the form k x a = k x a = CL"G The coefficient and exponent values for the model for each type of packing are shown in Table 1. TABLE 1. Correlation Parameters (Ufford and Perona, 1973) Packing Type: 3/4-inch Berl Saddles 1/2-inch Raschig Rings 1/4-inch Raschig Rings C 7.78 3.59 4.23 r 0.82 0.93 1.06 s 0.46 0.42 0.75 Although the values for the coefficients in Table 1 are said to be well representative, the authors do not indicate how representative. A statistical parameter such as r2, indicative of fit, would have been appropriate. Their results for k L a, using Raschig rings compared with other workers' results are shown in Table 2. These re sults are for various packed heights, gas rates and liquid rates. The liquid flow rate power de pendence is also given for comparison purposes. TABLE 2. Liquid Phase Mass Transfer Coefficients: k L a(lb/hr-ft 2 ) SOURCE 1 2 2 3 4 2 2 5 6 4 2 4 2 SYSTEM 1 2 2 2 2 2 2 2 3 4 2 2 2 FLOW CTC CNC CNC CTC CTC CNC CNC CNC CNC CTC CNC CTC CNC PACKED HT. 12" 10" 10 3.36'13.2" 10" 10" 0-75" 12 15.3" 10" 17 10 4.34' PACKING 1 2 3 4 3 3 3 3 5 6 7 8 7 G(~) 58 58 58 18.75100 100 150 3046.4100 100 230 230 hr-ft 2 84.3 1380 125.4 r 1500 1710 438 541 1090 2017 680 806 1050 680 1730 547 2479 1660 2000 1997 594 707 1436 2434 888 1050 1360 906 2130 692 3051 2101 L( lb ) 3000 2434 913 1030 2120 3166 1295 1630 1990 1360 2870 965 4084 2930 hr-ft 2 4000 2883 1238 1346 2793 3817 1692 2006 2587 1810 3510 1222 5036 3709 l 6000 3607 1903 1963 4122 4967 2467 2930 3910 2721 4700 1704 6741 5172 8000 4087 2582 2565 5989 3224 3640 5340 3620 5785 2157 8044 6548 10,000 4692 3271 3156 6924 3968 4703 6900 4530 6890 2590 9718 7863 0.54 1.06 0.93 0.96 0.65 0.93 0.72 0.99 1.00 0.72 0.82 0.72 0.82 SOURCES SYSTEMS FLOW PACKING 1. Allen (1938) 1. CO 2 -Water CTC-Countercurrent 1. 3/8" Raschig Rings 2. Ufford & Perona (1973) 2. CO 2 -Air-Water CNC-Concurrent 2. 1/4" Raschig Rings 3. Koch et al (1949) 3. O 2 -Air-Water 3. 1/2" Raschig Rings 4. Sherwood & Holloway (1939) 4. CO 2 -0.5M 4. 3/8 -1 1/ 4 Raschig Rings 5. Reiss (1967) Na 2 SO 1 5. 1 1/2" Raschig Rings 6. Danckwerts Gillham (1966) 6. 1/2 Berl Saddles 7. 3/4 Berl Saddles 8. 1 Berl Saddles 9. 3/4" Berl Saddles SPRING 1976 87


t, .., 4000 1000 500 2000 5000 L, lb/hr-ft 2 10,000 FIGURE 2. Mass transfer coefficients for Raschig rings at lower gas mass velocities in C0 2 -air water systems. Comparisons between the concurrent and countercurrent results tabulated in Table 2 are more readily seen in Figures 2 to 4. Sherwood and Holloway (1939) ran countercurrent flow experiments on the hydrogen-, oxygenand car bon dioxide-water system using 0.5-, 1.5and 2.0-inch Raschig rings. The gas flow rates ranged from 30 to 1300 lb / hr-ft 2, and liquid flow rates varied from 200 to 32,00 lb / hr-ft 2 Comparison of 0.5-inch Raschig rings between Sherwood and Holloway, and Ufford and Perona at various liquid flow rates are shown in Table 2. A gas flow rate of 100 lb / hr-ft 2 is used because Sher wood and Holloway used this as their only gas flow rate for 0.5-inch rings. As shown in Table 2, the L dependence from the correlation of Sher wood and Holloway for 0.5-inch rings is 0.65. Ufford and Perona found a dependence of 0.93. The countercurrent liquid mass transfer co efficients are greater by factors of about 3 at the lowest liquid flow rate and about 1.75 at the high est liquid flow rate. This is notable because the same mass transfer coefficients are attainable at very high liquid flow rates if extrapolation is al lowed. This liquid flow rate for matching mass transfer rates is above the countercurrent flood ing point of approximately 13,300 lb / hr-ft 2 88 For 1.0-, 1.5and 2.0-inch Raschig rings, Sher wood and Holloway found a liquid flow rate power dependence of 0.72, but this was using gas flow rates of 100, 230 and 230 lb / hr-ft 2 for each pack ing, respectively They did not vary enough gas flow rates for each type of packing; therefore, gas rate dependence is undetermined. Packing height was varied from 6 to 49 inches with no effect on the mass transfer coefficient. Ufford and Perona stated that Sherwood and Holloway cor related data on 0.5-inch Raschig rings from Allen (1938). Allen experimented with 3 / 8-inch rings only. Allen found a liquid flow rate power de pendence of 0.54 for a gas flow rate of 58 lb / hr ft 2 This dependence was determined by Sher wood and Holloway using their correlation model. A comparison between the data of Allen and that of Ufford and Perona is shown in Table 2. The countercurrent mass transfer coefficient is 3.16 and 3.91 times larger than the concurrent co efficients for 1 / 2and 1 / 4-inch rings, respectively, at the lowest liquid flow rate. This compares with a countercurrent coefficient that is 1.43 and 1.49 times larger at the highest liquid flow rate. After an L of about 14,000 lb / hr-ft 2, a concurrent tower using 1 / 4or 1 / 2-inch rings yields higher transfer coefficients than a countercurrent tower packed "' ... I ... .c .c 6000 4 0 00 2000 t, ~.., 1000 700 __ ...._ ___ _.___....__...._ _.__ __ ...._ ........ 2000 5000 L, lb/hr-ft2 10,000 FIGURE 3. Mass transfer coefficents for Rashig rings at higher gas mass velocities, CO 2 -air-water except for Danckwerts and Gillham. CHEMICAL ENGINEERING EDUCATION


with 3 / 8-inch rings at a gas rate of 58 lb / hr-ft 2 At first glance, without examination of other parameters, the concurrent tower would obvious ly be much superior to the countercurrent tower for high flow rates. It must be remembered that this only applies to the COrwater system. Over a range of 3 / 8to 1 / 4-inch Raschig rings in countercurrent flow, Koch, Stutzman, Blum and Hutchings (1949) found that the following cor relation fit all their dates within + 10.1 % k L a = 0.25 L D-9 6 where L is given in lb-moles / hr-ft 2 and k L a is given in lb-moles / hr-ft 2 (lb-moles / ft 3 ). The liquid flow rates were varied from 61.2 to 4140 lb / hr-ft 2, while the gas rates were varied from 18.75 to 84.3 lb / hr-ft 2 Thus, the data of Koch et al was used as a comparison with Ufford and Perona because the power dependence of L is approximately the same. The Koch et al co efficient is 2.0 to 2.5 times larger at the lowest liquid flow rate and 2.1 to 2.17 times larger at the highest (extrapolated) liquid flow rate than the 1 / 2or 1 / 4-inch ring coefficients of Ufford and Perona. Ufford and Perona state that Koch e t al found little variation of k L a for all sizes of rings. This is not quite true. Koch et al found up to a 24 % deviation using the 0.96 correlation for 3 / 8-inch rings, and no deviation for 3 / 4and 11 / 4-inch rings, (their Tables 3, 4 and 6). As Koch et al explained it, "It may be pointed out that different powers on L could have been used within the experimental error of the data, and it is possible to use an exponent of 0 8 which is the more widely accepted one. However, a careful analysis of the data indicated that an exponent of 0.96 represented the best compromise between average deviation of the data and representation at both extremes of liquid rates." Reiss (1967) experimented with stacked and dumped 1 / 2and 1-inch Raschig rings for oxygen desorption in concurrent flow. He found that his data fit an expression in the form of the Ergun (1952) equation: 8 ( g c ;~P 3 ) { l~ ) 3 = aRe + ,8Re 2 where Re= DpVp ,(1-e) The values of a and ,8 are different for each type of packing. Reiss based his mass transfer SPRING 1976 N ... I .c ...... .0 8000 4000 2000 -.lie 1000 700 Sherwood a Holloway / 2000 Ufford a Perona~ 5000 L, lb/hr-ft 2 / / 10,000 FIGURE 4. Mass transfer coefficients for Berl saddle packings, CO 2 -air-water system. coefficients on an energy dissipation function for the liquid phase: E i = V i ( ) 1g where ( .6 P /.6 Z) 1g is the pressure gradient of the gas-liquid phases combined and V i is the super ficial liquid phase velocity. Reiss' correlation allows design calculations that are accurate to + 50 % From representative calculations it can be seen that there is a definite gas flow rate dependence because the frictional pressure gradient, 8, must be calculated for both phases using the Reynolds number for each phase. Gas flow rates ranging from 138 to 1380 lb / hr ft 2, and liquid flow rates ranging from 2246 to 22,460 lb / hr-ft 2 were used. A comparison between the coefficients of Ufford and Perona with those of Reiss at a gas rate of 150 lb / hr-ft 2 and various liquid rates is shown in Table 2. At the lowest liquid flow rate, the coefficient of Reiss is 1.3 times larger than that of Ufford and Perona for 1 / 2-inch rings. At the highest liquid flow rate, the Reiss coefficient is 1.47 times larger. Sher wood and Holloway (1939) and Higbie (1935) Continued on page 102. 89


USE OF FLOWTRAN SIMULATION IN EDUCATION J. PETER CLARK Virginia Polytechnic Inst. and State U. Blacksburg, Virginia 24061 JUDE T. SOMMERFELD Georgia Inst. of Technology Atlanta Georgia 30332 0 VER THE PAST few years, one of the major efforts of the CACHE Committee ( Computer Aids to Chemical Engineering, a committee of the National Academy of Engineering) has been the installation and maintenance of FLOWTRAN on a commercial network for use by ChE edu cators. FLOWTRAN is a large, general-purpose, steady-state simulator of chemical processes with extensive facilities for physical and thermo dynamic property data handling and a large li brary of equipment modules, including cost esti mation capability. It was developed by the Mon santo Company for internal use and was offered, for a time, as a commercial service by Monsanto. Currently, FLOWTRAN is available only by out right purchase (at a cost of $105,000) to com mercial users. In 1972 the Large Scale Systems and Pro gram Distribution Task Forces of CACHE examined most of the commercially available general-purpose simulators in a search for one that would best serve ChE departments. The de cision to concentrate on FLOWTRAN resulted in initial inquiries to Monsanto in 1972. On De cember 10, 1973 Monsanto agreed to make FLOW TRAN available to universities via a national computer network. Further, Monsanto provided a cash grant to subsidize the installation of the program on a commercial network (United Com puting System, Inc.) and the preparation of a text by CACHE to aid users. In addition, Dr. A. C. Pauls of Monsanto was assigned by Mon santo as a consultant to CACHE to assist in the use and promotion of the system. This paper reports on experiences with FLOWTRAN since its installation for educational use in mid-1974. The authors are co-chairmen of 90 the FLOWTRAN User's Group, which has been established to aid users and further additional exploitation of this new teaching and research resource. FLOWTRAN ACCESS F LOWTRAN IS INSTALLED on a CDC 6600 in Kansas City, headquarters of UCS. There are two ways of accessing the program: by slow speed terminals (RJE, Remote Job Entry) or by high-speed terminals (RBE, Remote Batch). Slow-speed terminals are such devices as Tele types or Execuports; there are many high-speed terminals, such as those made by Unitech, Mo hawk, and CDC. For the use of slow-speed terminals, UCS provides local phone numbers in Jude T. Sommerfeld is a professor of chemical engineering at the Georgia Institute of Technology He received his BChE from the Uni versity of Detroit and his MSE and PhD from the Univ e rsity of Mich igan His activities include teaching research and consulting in the areas of process design, reactor design and computer application s. He has had l O years of engineering and management experience with BASF-Wyandotte Corp Monsanto Co Parke, Davis and Co and Ethyl Corp and is a member of AIChE, ACS NSPE and ISA He is also a registered professional engineer in Georgia. J. Peter Clark received his B S in Chemical Engineering from Notre Dame and his PhD from the University of California Berkeley Before joining the faculty at Virginia Tech in 1972 he spent four years in the U.S Agricultural Research Service His research interests are food en gineering, chemurgy, plant tissue culture, and was t e water treatment. He teaches design, simulation and optimization and serves as co-chair man of the FLOWTRAN Users Group. CHEMICAL ENGINEERING EDUCATION


about 90 cities. These are nodes from which data is sent over USC's own lines to the computer, thus saving the user phone charges. High speed users call directly to Kansas City over WA TS lines (toll-free 800 numbers). Originally it was felt that most users would only have access to slow speed terminals and so the wide coverage of UCS influenced its choice as a network. In prac tice, most users have found a high-speed terminal, which is more economical. Details on procedures for using FLOWTRAN from either sort of ter minal are provided in a manual [1] written by Dr. R. R. Hughes of Wisconsin, which is given to each user. User's gain access to FLOWTRAN by sign ing a three-party contract among CACHE, Mon santo and the user. A potential user should at tend one of the Workshops offered by CACHE through AIChE before attempting to use the system. The Workshops are based on the text written by J. D. Seader (Utah, W. D. Seider (Pennsylvania) and A. C. Pauls (Monsanto) with an extensive example by R. R. Hughes (Wis consin). [2] The text is available from Ulrich's Bookstore in Ann Arbor, Michigan for $9.95 with discounts available to bookstores. The primary provision of the agreement is that the user will only use FLOWTRAN for teaching and research purposes. After signing, the user receives an ac count number, password, and as many user IDs (for his students) as he specifies. To aid and encourage users after training and to promote further use, the FLOWTRAN User's group holds meetings at many AIChE meetings, publishes a newsletter which is sent to all de partments, provides consultants and is collecting information (such as problems for class use) for dissemination by CACHE. The consultants and their addresses are listed in Table 1. EXTENT OF FLOWTRAN USAGE A S OF JUNE 30, 1974, there were 25 user schools with cumulative billings to that date of $15,716. Professors from about 50 schools at tended two FLOWTRAN workshops (North western in August 1974 and Houston in March 1975). Another workshop was held in Boston in September 1975. The range of billings, as of June 30, 1975, was up to $2890. Five schools had spent over $1000 and eight others had spent be tween $500 and $1000. Two other schools have issued purchase orders. The cost of using FLOWTRAN on the UCS SPRING 1976 TABLE 1 FLOWTRAN Consultants by Region New England: NJ, PA, MD, DE, NY Warren D. Seider Department of Chemical Engineering University of Pennsylvania Philadelphia, PA 19174 Southeast: NC, TN, SC, GA, FL, AL, MS Jude T. Sommerfeld Department of Chemical Engineering Georgia Institute of Technology Atlanta, GA 30332 Mid-Atlantic: VA, WV, OH, KY, MO J. Peter Clark Department of Chemical Engineering Virginia Polytechnic Institute and State University Blacksburg, VA 24061 Great Lakes: Ml, IN, IL Richard S. H. Mah Department of Chemical Engineering Northwestern University Evanston, IL 60201 Midwest: WI, MN, IA, KS Richard R. Hughes Department of Chemical Engineering University of Wisconsin Madison, WI 53706 Everything else (West and Southwest) J. D. (Bob) Seader Department of Chemical Engineering University of Utah Salt Lake City UT 84112 Consultant to the Consultants Allen C. Pauls Corporate Engineering Department Monsanto Company St. Louis, MO 63166 network is not excessive. Using Remote Batch Entry on overnight service, costs run from ap proximately $2.00 for small jobs to $7.00 for large jobs. One technique for minimizing cost while the student is learning to use FLOWTRAN is to require "dry runs" (i.e., FLOWTRAN input data on computer coding forms that are checked for errors, but not executed). Students are supplied FLOWTRAN solutions to their "dry runs" for analysis. Only then are they permitted access to the computer. A problem of "hard" vs. "soft" computer money may exist. Some campuses have an internal budget for computing which involves only paper transfers of funds. Use of FLOWTRAN requires a purchase order to UCS for real or "hard" money. However, this problem is not insurmount91


able. W ith the advent of external networks, many computing centers are changing to a "real money system of accounting. Also, the re are sources of money for educational purposes, such as teach ing innovation grants, on many campuses which can fund activities like using FLOWTRAN. Judging by the vo lume of usage so far, pro fessors have been creative in persuading their departments to provide the resources necessary to gain access to FLOWTRAN. HOW IS FLOWTRAN USED? T HERE SEEM TO BE at least four categories of FLOWTRAN use. These are: conventional process design courses, computer-aided design electives, separations courses, and thermo dynamics courses. Without a detailed survey, we can only speculate on the distribution of actual usage, but these four categories embrace those we have learned of. It is remarkable that the system is versatile enough to include so many possibilities. In conventional process design courses, one procedure is to assign cases to groups or in dividuals who, after training and orientation to FLOWTRAN, use the system to prepare a design report, possibly including an economic evaluation. Many interesting processes can be analyzed using FLOWTRAN with relatively little difficulty. For example, the FLOWTRAN system includes physical property constants for 180 chemical com pounds. It also includes 30 modules for simulat ing equipment items. It is not difficult to add new compounds or new equipment modules, such as special -purpose reactors, as they are needed. FLOWTRAN frees the student from tedious and repetitive calculations, allowing him to explore parametric cases and flow-sheet variations. Ob viously, good judgment in evaluating the results must be emphasized since FLOWTRAN, like any computer program, will only do what it is told to do. A slightly different orientation exists in courses that emphasize computer-aided design, a fairly common elective or extension of the con ventional design course. Here the point really is to learn problem formulation (where to tear re cycles or how to avoid them) and also come to understand the characteristics and limitations of models and simulators. Another objective, fre quently as a research topic, might be how to ex tend the usefulness of general purpose simulators. Hughes, for example, described the use of FLOW TRAN in optimization in a recent paper. [3] 92 Finally, FLOWTRAN contains some power ful facilities for the study of complex vapor liquid, vapor -li quid-liquid, and liquid-liquid sepa rations and corre lation of thermodynamic data for pure compounds and nonideal mixtures. These facilities were included to support design efforts and, of course, are valuable there. But they can also stand alone and be exciting adjuncts to graduate courses in these subjects. FUTURE DEVELOPMENTS F LOWTRAN USAGE IN universities is off to a good start but clearly has not reached its full potential. Usage under the present arrange ment is expected to about double in the next academic year. Beyond that it will grow at a less rapid rate. In the meantime, however, other de velopments may greatly expand the community of users. The CACHE Committee, because of its experience with FLOWTRAN, is one of the leaders in the field of academic application of computer networks. A network is an arrangement of computing facilities which ex change resources and data over a communications me dium suc h as telephone lines or microwa ve links. UCS is a commercial network with one host (containing FLOWTRAN among many other resources) and many node s. Soon, there are likely to be one or more multi ho st networks connecting educational institutions. In fact, a prototype network involving twenty universities will probably be established within a few years. FLOW TRAN as an example of a largescale resource for ChE, will probably be installed on this prototype network. One of the consequences will be much lower costs for those fortunate enough to have access to the network. If the prototype is successful, the network will almost s urely be expanded to involve many more institutions. The CACHE Committee, thpiJgh its Task Forces, is examining other resource s that could be provided to ChE departments. A mong the possibilities are: proce ss sy nthe sis programs, physicai:a~d chemical property data bases, and safety and relia~ility analysis programs. There are many problem s to be solve d before another large system can be widely disseminated, including docu mentation, maintenance and easy access. However, it is quite likely that ChE educators can anticipate further expansion of their arsenal of computer-based weapons in the next few years. Willing volunteers for the many tasks that mu st be handled first are urged to make themselves known. D REFERENCES 1. Hughes, R R. "CACHE Use of FLOWTRAN on UCS," CACHE, Inc., Cambridge, Mass. 1975. 2. Seader, J. D., W. D. Seider, A C. Pauls. "FLOW TRAN Simulation-An Introduction," CACHE, Inc., Cambridge, Mass. 1974 3. Hughes, R. R. "Optimization Methods for Block Sim ulation," paper presented at VI Interamerican Con gress of Chemical Engineering, Caracas, 1975. CHEMICAL ENGINEERING EDUCATION


WORCESTER POLYTECHNIC INSTITUTE Continued from page 73. addition to the Department faculty, Bob Thomp son, who is an expert wine maker and bread baker. The Department had its beginnings in 1922 when the late B. F. Dodge, then a recent PhD from Harvard, was invited to be lecturer in In dustrial Chemistry and Chemical Engineering for the senior chemistry students. In 1925 T. K. Sherwood was appointed to the faculty to broaden the ChE curriculum within the chemistry de partment. In 1940 Ernest Wilson, a chemical engineer, became the chairman of the combined chemistry and ChE department, and until his death in 1958, he built a faculty, laboratory facili ties and a strong undergraduate program. Be ginning in 1958, Wil Kranich presided over a growing graduate and research program, a new building, and the redirection of the undergraduate program under the WPI Plan. When Kranich be came Dean of Graduate Studies, the chairmanship passed in 1975 to Imre Zwiebel. With a strong department faculty and a healthy level of out side support, challenges and opportunities still remain for growth, excellence and unknown new horizons. WPI CHEMICAl ENGINEERING FACULTY Kohler, J. T.: Assistant Professor Biomedical and enzyme engineering bio transport phenomena Kranich, W. L.: George C. Gordon Professor and Dean of Graduate Studies Catalysis, process development Ma, Y. H.: Associate Professor (Professor as of July 1, 1976) Applied mathematics, simulation, diffu sion in porous solids Meader, J. W.: Assistant Professor Rheology, heat transfer Sand, L. B.: Professor Materials synthesis, molecular sieve cat alysts, sorbents, geochemistry Thompson, R. W.: Assistant Professor Adsorption phenomena, applied kinetics and chemical reactor behavior, emul sion polymerization kinetics Wagner, R. E.: Professor Nuclear technology, transport phenom ena, thermodynamics Weinrich, S. D.: Leonard P. Kinnicutt Assistant Profes sor Weiss, A.H.: SPRING 1976 Systems analysis, optimization, process control Professor Zwiebel, I.: 1975-76 Aharoni, C.: Aiello, R.: Antoshin, G.: Guczi, L.: Complex reaction kinetics, catalysis, re source recovery Professor and Department Head Adsorption, applied mathematics, reactor design proces s design, mass transfer VISITING RESEARCH FACULTY Technion-Israel Institute of Technology, Haifa, Israel Catalysis, adsorption University of Naples, Naples, Italy Molecular sieves USSR Academy of Science, Moscow, USSR Catalysis Institute of Isotopes of the Hungarian Academy of Science, Budapest, Hun gary Catalysis [eJ ;j :>Ill book reviews PARTICLE SIZE MEASUREMENT by Terry Allen Halst ed Press, 19 75. 454 pages, $ 25.95. Reviewed by Clyde Orr, Georgia Institute of Technology The author, a Lecturer at the University of Bradford in England, has expanded and partially updated his earlier edition of the same title. Coverage is broader than the title would suggest, encompassing, in addition to the stated subject, treatment of sampling, surface area evaluation, and pore determinations in porous materials. An effort is made to develop the theoretical back ground of each subject, but much of the treat ment consists of technique and procedural re views. This makes the book valuable for the no vice. Others more knowledgable will recognize the author's bias occasionally creeping into the presentation. The work consists of 18 chapters the first three of which cover bulk powder sampling from gas streams, and atmospheric sampling. Separate chapters pertain to the treatment of size distribu tions, to the interaction between particles and fluids in a gravitational field, and to powder dis persion. Remaining chapters are devoted more Continued on page 104 93


(D ;I classroom CAN AN ENGINEER BE ACTUALIZED? A Senior Seminar Course JOHN C. BIERY Uni versi ty of Flo ri da Gaines vi lle, Florida 32611 CAN AN ENGINEER be actualized?" This is a question that I have been asking our stu dents in chemical engineering here at the Uni versity of Florida for the last three years. No, I haven't gotten a clear and concise answer to the question. You may ask, why even ask it. Why is it important? Particularly, why is it important to me? The question, I believe, for me as a chemical engineer, has been very important; although I didn't know enough to ask the question when I should have. I worked for a chemical company for seven years after graduating from the University of Michigan in 1951. My first supervisor in that chemical company, a production supervisor, was very much unaware of the characteristics of ac tualization. As a result, I found myself aching for some honest sharing, and maybe I should say car ing feedback concerning my own interaction and productivity in that particular company I worked with this individual for four years. And really, during that total period of time I never did have any positive, constructive view of my value to the company. If I was doing anything really all right, I never knew it. I now look back at my experience there as a positive one. I learned much, and I think I was a productive engineer. However, I do re member having an aching gut almost every spring when I was working for this company. I believe part of that ache resulted from my lack of knowl edge of myself, and, particularly, from the inter action or lack of it with my own supervisor. After leaving the chemical company to go back to school to obtain a Ph.D., I then joined one of the national laboratories. In that particular or ganization, much freedom was given to each of the staff members and much of the productivity of that organization resulted from the grass root ideas and the involvement of each staff member, 94 even though he or she did not have an official title Unfortunately, I did not realize that my responsi bility was to dive in, to let people know where I stood, to let them know what ideas I had and how they should be expedited. Initially, I went back into my little corner, utilizing my new tools ob tained in the Ph.D. program, ran the computer, worked with my mathematics, and did not pro ductively contribute to the guidance and sense of direction of the organization. Finally, after about three years of this type of non-involvement, I sud denly became very aware of my potential to the group and to myself. Fortunately, I did turn around and did start to contribute aggressively at every level that was reasonable. Can the engineer move out of Consciousness I and Consciousness II and still maintain the high level of productivity and creativity that is necessary in our very technologically oriented society of today? I've shared with you these two experiences in my own engineering past to give emphasis to my own strong belief that we, as engineers, do need to have some of the characteristics of actualiza tion to be more effective and to enjoy more posi tively the engineering experience. My own experi ence in industry has indicated that much of the actualized characteristics are not there among the engineering community. Maybe I should ask why More important, I should ask, what can we do about increasing the level of actualization, the level of positive interaction that we as engineers can produce in our industrial environment. CHARACTERISTICS OF ACTUALIZATION A BRAHAM MASLOW INTRODUCED his ideas of actualization in the mid-fifties, and they have had considerable impact through the CHEMICAL ENGINEERING EDUCATION


humanistic psychologist upon many of us and also upon industrial management. I feel that there are certain ones of the characteristics of the actual ized person that are very meaningful to me, and they are the ones that I would like to emphasize during this presentation. Dr. Maslow discovered in his group of actualized people he studied that they seemed to have certain common character istics. They seemed to center around words such as honesty, awareness, trust, and openness. I will not try to describe in great detail these terms. Dr. Maslow's books are there to be read, as are others who have utilized his ideas and concepts. But the feeling that I obtained from his works is one of being free, of being very aware of oneself and the human process going on around ourselves, of trusting our own capabilities, and trusting what we do detect in this process, and finally being very open in what we feel and what we would like to express to those about us. The terms "sharing" and "feedback" come to be an important part of this openness, trust, awareness, and honesty. The sharing is sharing of ourselves, of our deep feel ings inside. As Jess Lair has said so appropriately in I Ain't Much, Baby-But I'm All I' v e Got, the loving process to him is one of deep sharing. I think that I agree. Also, the actualized person tends to be very much "here and now" oriented. Again, the awareness seems to center on the now. The excitement of the moment stands out. Finally he is process-oriented. The goal, many times, tends to be much less important than the process that heads toward that goal. As a matter of fact, he can brighten the day or brighten the moment in the midst of a very hectic time by making the here and now, the momentary process very delightful and very enjoyable. ENGINEERS' CHARACTERISTICS T O ACTUALLY CATEGORIZE the engineer and state his characteristics is a very danger ous process. He obviously is a very talented per son, has been very creative in the technological sense, and is a very stable person in the com munity. I believe the divorce statistics indicate that the engineer has one of the lowest divorce rates among any of the professional groups. He makes a good husband. However, if you ask the average student on campus about the engineers on campus, we will be viewed as to being quite "square", very dedicated to our books, very non-participative in activities SPRING 1976 John C. Biery is Chairman and Professor of chemical engineer i ng at the University of Flor i da He received his bachelor's in chemical engineering at the University of Michigan and his Ph.D. at Iowa State University. He did postdoctoral work under Prof. R B. Bird at the University of Wisconsin and has worked at Dow Chemical Co. and at Los Alamos Scientific Laboratory. He has taught at th e University of Arizona and at Florida and is the author of papers on sodium technology transport phenomena liquid-liquid ex traction, and engineering education. He i s a member of the ASEE Chemical Engineering Division Executive Committee and chairman of the Motivational Techniques Session at the November 1975 AIChE meet i ng in Los Angeles on campus, maybe quite unaware of the human process. In the class seminar I am about to describe, we utilize Greening of America by Charles Reich to give us some awareness of the types of people with whom we interact. He has arbitrarily broken down society into three groups, and he calls them Consciousness I, II, and III. In brief, Conscious ness I includes those people who are very self reliant, do not lean on others at all. They feel they can do it alone. The pioneer, who was willing to hack out an open plot of land in a thick forest many miles away from the nearest neighborhood, undoubtedly is very characteristic of Conscious ness I. Consciousness II is the group which has be come convinced that the large organization, whether it be large government, or large union, or large industrial corporations, is very necessary in solving all of the problems of society. If there is a problem that exists, the way to solve it is to create another large organization, or another large com mittee, or another counteracting force to balance those that are existing in the society. The char acteristic of the Consciousness II person is that he is a very willing worker, and also a very willing consumer. He is very status-conscious; salary is very important; grades are very important. His 95


position among the hierarchy is important. He works hard all week mainly to get away on the weekends so that he can go off to his cabin, or the ocean, or to some recreational area that can be totally separated from his work. Many times the work is very unsatisfactory, and his only reason for pursuing his particular profession is to gen erate money so that the weekends and particularly his vacations can become more meaningful. Consciousness III is a more difficult group to describe. The group is more human-oriented, tends to care about the human beings around, is very aware of the human process. Goals, particularly can be rightly asked: can the engineer move out of Consciousness I and Consciousness II and take on some of the characteristics of Consciousness III and still maintain the high level of productiv ity and creativity that is necessary in our very technologically oriented society of today? BREAKING OUT OF THE MOLD J F WE REALLY WANT TO break out of the Consciousness I or II mold, what can we do? The first question is, "Do we really want to break out?" In reading Abraham Maslow's work and also that of Everett Shostrum, I get a thrill and a In the senior seminar, we concentrate for a while on role playing situations that help in these overall processes. Our students have been criticized before for not handling themselves very well at interviews, and, therefore, we are utilizing the interview process for our role playing situation. monetary and status goals, are relatively unim portant. Many of the characteristics of Conscious ness II have been rejected by Consciousness III. In some respects, the Consciousness III person might be described as being actualized. However, I believe the one-to-one relationship is not totally there. Charles Reich likes to describe the "hippie" of the mid-sixties as being the characteristic per son of Consciousness III-the long hair, the flow ing clothes, maybe even the use of drugs. There fore, by definition, Consciousness III is out of bounds for the "square" engineer-or is he out of bounds for the engineer? I guess the question I like to pursue is, "Are there characteristics of Consciousness III that can be nicely integrated into the intense work regimen of the engineer that can invigorate and enliven his own profes sional consciousness?" From my own view, I feel that the engineer generally sits in Consciousness I and II. I have personally worked with engineers who are so in dependent they will not even say hello in the hall as they walk along. There are others who are very much involved in the work and play schism, as indicated in Consciousness II. Also, many of the engineers become quite subservient to the overall process of industrial involvement of the organiza tion, become very aware of their very tenuous state that they seem perilously to maintain in a given organization. Yes, the question, I think 96 feeling of, "gee, wouldn't it be nice to have some of the thrill of life that the actualized individual seems to have! His openness, his honesty, his awareness. His feedback and sharing seem to be delightful things to use and participate in." Also, another aspect of the actualized process is that of being dedicated to the growth of the other person, or maybe to a vibrant idea. This dedication to growth has been expressed very nicely in a book by Milton Mayeroff, the title being On Caring which came out in 1971 and is published in Perennial Library in paperback. In that book, he states that the caring process is one of dedicating yourself to the growth of the other person or to an idea or process. To me, this view makes a lot of sense. The growth of one's wife is necessary if the relationship continues to be a vibrant one. Therefore, dedicating some of my efforts to her growth certainly is to me a loving and caring process. In the management field, the best managers, I feel, are those who are dedicated to the growth of the people they manage. They are aware of their needs, and they create an environ ment which contributes to the growth of these people. How do we move from one growth level to an other? Growth occurs slowly. I am sure that the reading we've done and can do is an important part. We need places to practice, however, the actualized process, even to be aware of what it might entail. My own feeling is group work, group CHEMICAL ENGINEERING EDUCATION


dynamics, being aware of the dynamics, is a very important part of this growth process. An as sociate of mine the other day stated that it takes time for one to become what he philosophically states when a change of philosophy has occurred. He indicates that maybe five years are required before a person can really assimilate and be what his philosophy tends to dictate. This is a very saddening realization, because even though I want to be actualized; even though I want to be aware, even though I want to be honest and open, I can not do it immediately today. I must practice, I must work, I must read, I must utilize the process in everyday life, in maybe artificial situations such as group activity, to be able to make it a part of me. SENIOR SEMINAR THE ABOVE STATEMENTS concerning actualization and the possible benefits of trying to be aware of it and the utilization of it as an en gineer have been the motivating force behind my presentation and involvement in a senior seminar for our chemical engineering students at the Uni versity of Florida. The course meets once a week, is one hour credit, and is totally dedicated at the moment to the study of humanistic processes and the involvement of the engineer in those processes. We utilize Greening of America by Reich, Man, the Manipulator by Shostrum, On Caring by May eroff, and I Ain't Much, Baby-But I'm All I' v e Got by Jess Lair as the textbooks in this course. The texts are nowhere near as important, how ever, as what goes on in the course itself. The group dynamics, the interaction, the sharing, the caring and feedback processes are very important to try, to risk a little, to get the feel of what can and cannot be done. My own feeling about group work is that it best occurs when it is done in a caring way. The so-called encounter group totally turns me off. I don't like the antagonism and the non-caring that can go on in the so-called encounters. However, the sharing group or the support group can do much to enhance the characteristics of honesty, awareness, trust, and openness we would like to see developed in the members of the group. In the senior seminar, we concentrate for a while on role playing situations that help in these overall processes. Our students have been crit icized before for not handling themselves very well at interviews, and, therefore, we are utilizing SPRING 1976 the interview process for our role playing situa tion. I ask the students to go over to the Place ment Center and investigate a given company very thoroughly. A team of two students then will put on an interview for the rest of the group, and actually for themselves. One will be the inter viewer and the other the interviewee, and they will go through the total interview as best they envision it. The role playing has many advantages. They do obtain some practice in interviewing. Also, they become aware, with the assistance of the group, of their own participation in that inter view, of their own body language, their eye con tact, their nervousness or lack of nervousness, their interest or lack of interest in the process. They can be made aware of their manipulative be haviors, if they happen to take on any of the top dog or underdog characteristics as indicated by Shostrum. The interview, as we are all aware, can be very manipulative. It should be one of generat ing useful information for both participants, and I try to emphasize that the student should make it as non-manipulative as possible. This is a case for openness and being candid, of trying to make the interview useful for learning about the com pany he is investigating. He should not allow him self to be manipulated, if manipulation starts. All in all, the interviews tend to be quite exciting, and sometimes they are so well done that the students lose themselves in that process and really are totally unaware of the group that is looking on. The feedback session after the interview also is very worthwhile. We obtain practice in giving feedback, and giving it in a way that can be ac cepted by the recipient. In many cases, the feed back has to be relatively negative. How can the negative comments be couched in a way that they can be accepted, and then how can the person re ceiving the feedback accept it in a way so that his self-image is not totally destroyed. We, of course, in the industrial setting have to face this situation time and time again. In actuality, when it comes to employee evaluations particularly, the overall situation may totally be avoided by the supervisor who is not willing to involve himself in sharing and feedback, in honesty, which are necessary to facilitate the evaluation process. Another aspect of the group dynamics and group interaction that can occur in the seminar is the practice that can be obtained in sharing of one's deepest feelings. This sharing is a very dif ficult process. However, again, practice does help in making it an important part of our behavior. 97


RESULTS OF BEING ACTUALIZED T HE STUDENTS IN OUR SENIOR seminar in chemical engineering have not come to any conclusion as to whether the engineer working in our society, and usually for an employer, can be fully actualized, can be a member of Group Ill and still be productive. For instance, we dis cussed recently, the paper Dr. Ray Fahien and I presented at the American Society for Engineer ing Education Annual Conference in 1973 which was titled "Should Engineering Students Be Taught to Blow the Whistle on Industry?" In that paper, we discussed the hierarchy of values extrinsic, systemic, and intrinsic values-and we suggested that, depending upon the type of ques tion being viewed, the engineer might take dif ferent actions, both internally in and external to the company. Our group became v ery aware in the discussion of the paper that to take any action at all requires a great degree of self-confidence in the engineer, a high degree of awareness, and certainly a great feeling of being open and want ing to express honesty These, of course, are the characteristics of the actualized person. They, also, expressed a great fear in taking the risks that are necessary to be actualized. They felt their jobs might be in jeopardy, and that the Group II values, such as a sumptuous home, a boat, two or three cars, and a house or lot in the country, might be jeopardized if the person actually did behave in a fully actualized way. I believe the group in this discussion the other day was not very hope ful that the engineer, as they viewed themselves and as they viewed other engineers, could actually interact with industry in this manner. I guess my own view of the situation is much more hopeful. I believe that the risks can be taken, and that the risk can be taken and still productiv ity can result As a matter of fact, maybe more useful productivity can result than if the engineer is very passive and a very willing participant of the system, not questioning its sense of direction, both technical and ethical. I may be somewhat naive in my point of view, but I tend to feel that the feelings of Group III consciousness are grow ing and that they may become a more noticeable part of the large governmental, industrial system "Should Engine er ing Stud e nts Be Taught to Blow th e Whistle on Industry" was pr e s e nted by John Biery and Ray Fahi e n a t ASEE 1973 Annual Conf e r e nc e in Ames, Iowa. and w as published in th e Fall 1975 issue of G EE. 98 in which we are no w in v ol v ed. In the discussion that followed the presenta tion of this paper on "Whistle Blowing" at the Annual Conference in Ames, Iowa, the partici pants there felt very similarly to the members of my senior group-that the action necessary actu ally to blow the whistle on industry would seldom occur However, at least one member of the audi ence indicated that if a higher percentage of us were willing to r isk then that percentage would tend to grow. So it means if w e, as engineers, are to be actualized and are to actually express our feelings and try to influence the sense of direction of an organization, w e will have to take the risks pretty much alone. But, if we so do, there is a good chance that others will finally risk with us. What I am suggesting is that the actualized engineer is a possibility, and that productivity and the excitement from that productivity may well increase if we have more of us w ho actually have actualized characteristics The risks are not trivial in speaking out, in being honest, and being aware of our human situation. But my own feeling is that these risks are worth taking, and they make the job itself very exciting. R E SU L T S OF THE SEMINAR W HAT DO I THINK the r esults of such a seminar as we are conducting in chemical engineering might be? I certainly do not want to delude myself in thinking the students in this class will go out and take the risks necessary to be totally actualized. However, I am sure many of them will now be much more aware of their role in industry and the fact that they do have an ob ligation to let their views be felt. I do hope that their awareness of their interaction in the c om pany is heightened and that their ability to speak up, particularly in the technical sense is in creased. Also, they can become better supervisors by being again very aware of the human process about them, aware of the needs of the people they are supervising, and then being able to take again the risks that are necessary to make the human process within their group a vital one. Yes, I do feel our engineers can have many of the charac teristics of the actualized individual as postulated !)y Maslow. And, fo r those of you who are in the industrial community or even in the academic community, I hope we have the pleasure of inter acting more frequently with an actualized engi neer. D CHEMICAL ENGINEERING EDUCATION


FOR A CHEMICAL ENGINEER A good career decision is like a good ,,a,~ stew.0 many things should go into itl Technical challenge for e x ample is an important consideration At Procter & Gamble you ll find as much as you can handle As a major chemical process industry in volved in a very wide range of product and process development activities we welcome chemical en gineers who like a challenge You need only p i ck the direction that interests you most! A company's stability, despite abrupt changes in the economy, is another important consideration in mak ing your career choice As is the growth record of your prospective employer At P&G we make and sell things that people need and buy, in good times and bad According to Fortune magazine One or more P&G products are used in 95 out of 100 homes a penetration unequaled by any other manufacturer of anything! P&G sales and earnings have increased every year since 1952. Net sales have doubled in less than 10 years to more than $6 billion New products and product improvements are being added continually And if you're interested in benefits, consider our Profif-Sharing Trust Plan. The performance of this Plan to date has enabled P&G monthly salaried employees to retire at 65 with a lump sum amount equal to about 15 times their average career annual salary. This is without cost to the employee. Technical challenge Substantial initial responsibility Advancement on merit alone. Stability in good times and bad. A company marked by vigorous growth. A benefits program that ranks among the top 5% of all U S companies. Good reasons to see the P&G re cruiter when he visits your campus! PROCTER & CAMBLE An Equal Opportunity Employer


... (;]IZ) CHEMICAL ENGINEERING l]I] DIVISION ACTIVITIES SUMMER SCHOOL IN SNOWMASS The next Summer School for ChE Faculty will be held in Snowmass, Colorado, during the week of July 31 through August 5, 1977. The Summer School has been held every five years, under the sponsorship of the Chemica l Engineer ing Division of ASEE. The last previous Summer School was held at the University of Colorado in Boulder in 1972. Snowmass is located just minutes away from Aspen, in a high (8000 ft.) mountain valley, su: rounded by 14,000-ft. snow capped peaks. It 1s one of the most popular ski resorts in the nation during the winter, and is a secluded but active and attractive alpine resort in the summer. The Summer School has arranged lodging, at quite reasonable prices, in two adjacent inns and near by condominium facilities. Along with the lodging, Snowmass will provide large-group eating facili ties, classrooms and meeting rooms. For off-hours TABLE 100 1. Companies providing financial support for 1977 sum mer school for Chemical Enginee ring Faculty. Dow Chemical Company E. I. DuPont deNemours & Company Stauffer Chemical Company Union Carbide Corporation U pjohn Company Celanese Corporation Procter & Gamble Compa ny Exxon Corporation Fluor Corporation General Electric Company Ethyl Corporation Continental Oil Company General Foods Company Rohm & Haas Company Envirotech Corporation Snowmass offers many individual and family ac tivities from which to choose. Hiking trails to the mountains start from the front door, and the famous Maroon Bells area of the Rockies is near by. There are also golf, tennis, riding, raft trips down the Roaring Fork, and 13 swimming pools available to participants. Some families may wish to take advantage of the "Kindeheim," which offers day-time child-care services. Then there is Aspen itself, with interesting shops, old-West Museums and the reknowned summer Music Festival. Co-Chairmen of the Organizing Committee for the Summer School are C. Judson King and Michael C. Williams of the University of Cali fornia, Berkeley. They have arranged the pro gram in a Gordon-Conference format, with scheduled sessions in the mornings and evenings and with afternoons free. There will be opportuni ties for attendees to meet in informal discussion in off-hours, as they may desire. The program is built around a series of oneand two-day work shops, arranged so that there will be six simul taneous workshops at any time. The workshops are arranged by areas of interest, with opportuni ties for participants to switch between areas during the week if they wish. The theme of the program is "Expanding the Horizons of Chemical Engineering," with six main program areas. These areas, and their chairmen, are as follows: BIOLOGICAL (Stanley M. Barnett, U. of Rhode Island) will include sessions on education in bio-technology CHEMICAL ENGINEERING EDUCATION


fermentation and enzyme engineering, and food proc essing. o PROCESSES AND INDUSTRY (T. W. Fraser Russell, U. of Delaware) plans workshops on the economic struc ture of the chemical industry, process economics and in dustrial chemistry. CHEMICAL REACTIONS (Alexis T. Bell, U. of Cali fornia, Berkeley) will cover instruction in chemical kinetics, catalysis and subjects related to reactor design and dynamics. e APPLIED CHEMISTRY (Donald R. Woods, McMaster U .) is considering courses in electro-chemical engineer ing, meta ls process i ng surface and colloid chemistry, and solid fluid separations. TEACHING METHODS (Ernest J. Henley, U. of Hous ton) will take up motivational techniques and alterna tives to the lecture, as well as courses and curricula for non-chemical engineers and a modular course on safety and reliability analysis. e ADMINISTRATIVE (John W. Prados, U. of Tennessee) tentatively will include sessions on evaluating faculty HUBBARD: Instruction By the PSI Method Continued from page 79. (/) ..... z 0 a.. -I ct ..... 0 ..... (/) ..... z 0 a.. _. ct ..... 0 ..... 200 ~; A -J 8100 ] -. ,-r~ 1974 -. _,_: I I -~--------1F 0 L-=---------L---L-'-~---', __ .,__ ..... 0 2 4 6 8 10 12 UNITS COMPLETED 2001_A_ 1973 j } B : I }c + I 00 _ ____ .._ }D F-~----0 L----'-----'----'----'--___. __..._. 0 2 4 6 8 10 12 UNITS COMPLETED FIGURE 8. Total Score Correlations. SPRING 1976 workload and performance, as well as faculty recruit ment. Other sessions deal with the social and political aspects of engineering decision making, and one or more special topics. The detailed content of the workshops is still taking form. Financial support for the Summer School is being donated by a number of industrial com panies. At the moment there are 15 participating companies, listed in Table 1. It is anticipated that the number of participating companies will soon reach 20 or more, further reflecting the broad base of funding for the Summer School. The level of financial support is such that it will be possible to give a travel subsidy to attendees from the various universities around the country. Informa tion concerning applications for attendance and available subsidy will be distributed to Chairmen of ChE Departments, probably in late 1976. tutor system. They generally feel that supple mentary notes could be written more clearly. Eighty-eight percent of the students returning the questionnaire feel that they learn more study ing by the PSI method. Fifty-five percent of the students say that they prefer the PSI method to the lecture method. This is a somewhat lower preference than is usually seen for a PSI course. An overwhelming majority of students returning questionnaires usually say they prefer the PSI method. The lower positive response for the pro cess dynamics and control course may be due to its being a required course. When there is a choice of format as in the required dynamics course mentioned above, thirty-three percent of the students usually choose the self-paced method. For the process dynamics and control course, students who prefer a lecture format do not drop out, because there is no choice. If there were a choice, those students would drop out and would not have the opportunity to fill out a question naire. The questionnaire data from elective courses may be biased in favor of PSI. REFERENCES 1. Keller, F. S.; "Goodbye, Teacher", J. Appl. Behavior Anal.,1, 79 (1968). 2. Coughanowr, D.R. and L.B. Koppel; Process Systems Analysis and Control, McGraw-Hill Book Company, New York (1965). 3. Philippas, H. A. and R. W. Sommerfeldt, "Keller vs Lecture Method in General Physics Instruction", Am. Journal Phy s ics, 40, 1300 (1972). 4. Lord, H. W. and C. E. Work, "Self-Paced Instruction -Its Advantages and Pitfalls", ERM 4(3), 10 (1972). 101


MASS TRANSFER COEFFICIENTS: Miller and Rehm Continued from page 89. suggested the square root dependence of diffusivi ty for the mass transfer coefficients. If this diffusivity correction is used for the oxygen to carbon dioxide system, the Reiss coefficient is only 1.20 to 1.36 times larger. This shows good agree ment over the ranges studied. Reiss found a liquid flow rate power dependence of 0.99 compared to 0.93 for Ufford and Perona. This also shows good experimental agreement. Mcllvroid ( 1956) also did concurrent flow oxygen desorption studies using dumped 1 / 4-inch Ras chig rings, and 4and 6-mm glass beads. Gas rates ranged from 400 to 4000 lb / hr-ft2, while liquid rates varied from 7080 to 94,350 lb / hr-ft 2 Two distinct mass transfer mechanisms were found using the glass beads at various gas rates. The mechanism at the lower gas rates was due to a thinning of the liquid film with a correspond ing decrease in contact time and increase in kLa. As the gas rate increased, a more even distribu tion of the liquid phase with an increase in the effective wetted area available for mass transfer was found. A point was found at which all of the available area was completely wetted. At the higher gas rates, the effect on kLa was not as great because the film thickness continued to decrease, and / or the higher rates caused higher turbulence. The Raschig rings had only one mechanism present because of the hollow shape. This prevent ed a completely even distribution of the gas and liquid phases through the packing. Reiss ( 1967) found that Mcllvriod's data fit his correlation well, but from Fgure 18 of Reiss, there is either slightly less dependence on the liquid rate or slightly higher dependence on the gas rate. Danckwerts and Gillham (1966) experiment ed with 1-1 / 2-inch Raschig rings in concurrent flow. They absorbed CO 2 into 0.53M sodium sul phate solutions. Gas rates ranged from 46.4 to 125.4 lb / hr-ft2, while liquid rates varied from 2210 to 11,200 lb / hr-ft 2 Their mass transfer co efficient is compared to that of Ufford and Perona in Table 2 at a gas rate of 100 lb / hr-ft 2 and various liquid rates. Although the coefficients are equal at the lowest liquid flow rate, the com parison is between 1 / 2and 1-1 / 2-inch Raschig rings. The power dependence of the liquid flow rates are quite close though, 0.93 for Ufford and Perona and 1.0 for Danckwerts and Gill ham. Upon closer examination, using the correc102 tion for diffusivicity in the form V D / V D w the co efficients from Danckwerts and Gillham are 6.45 and 7.35 times larger than those of Ufford and Perona. It must be remembered that the packing is 1 / 2and 1-1 / 2-inch in size. The diffusivities, D and Dw, represent CO 2 in sodium sulphate and water, respectively. Sherwood and Holloway (1939) also experi mented with 1 / 2and 1-inch Berl saddles at gas flow rates of 100 and 230 lb / hr-ft 2 in countercur rent flow, respectively. Comparison of their co efficients with those of Ufford and Perona for these gas rates are shown in Table 2. For the 1 / 2inch saddles of Sherwood and Holloway compared to the 3 / 4-inch saddles of Ufford and Perona, the 1 / 2-inch saddle coefficients are 3.16 and 2.66 times larger at the lowest and highest liquid flow rates, respectively. The 1-inch saddles' co efficients are 1.48 and 1.23 times larger at the lowest and highest flow rates, respectively. The power dependence of the liquid flow rate for countercurrent flow is 0.72 and 0 82 for concur rent flow. There were not enough gas flow varia tions done to determine gas rate dependence. Ufford and Perona state that their coefficients are smaller as packing depth increases. They imply this is what is found experimentally. From Equation (15) it can be seen that this is a direct result of how they calculate their results. Since the packing height, Z, is in the denominator, any increase will correspondingly decrease the mass transfer coefficient. The ln term will probably change too, but not as severely as the inverse of the packing height. Danckwerts and Gillham ( 1966) do not suggest that the effect is not significant. From their Figure 15 they show ex perimental data up to 7 column diameters for two different flow rates that the transfer co efficient is independent of packing height. Their coefficients are reported in cm 3 / sec and are, there fore, not on a per volume of column basis. Wen et al (1963) found that, indeed, with a deeper bed k g a will decrease. From their Figure 18, the number of transfer units, No c, is a linearly de creasing function over a range of packing heights of from 1 to 3 6 column diameters. But, if k g a is plotted on log-log paper as a function of Z, above approximately 2 column diameters the negative slope begins to increase dramatically indicating a large effect. Although these results are inCHEMICAL ENGINEERING EDUCATION


dependent of all variables except packing height, their coefficients still contain a height dependence. This is because their coefficients are based on a per volume of column basis, and any comparisons should be made on a per area of column basis independent of height. This phenomenon was ex plained and observed as channeling. Ufford and Perona stated that coefficients measured with a height of 8.5 column diameters were much lower by factors of 3 to 4 compared with those measured with a height of 2.5 diameters at the lower liquid rates. They find this surprising. However, they base their co efficients on a per volume of column basis. This means that the height of packing is still a factor in the coefficient. If they based the coefficients on a per area of column basis and then compared the coefficients at the lower rates, it would be apparent that the coefficients were about the same. A packed height of 8.5 diameters compared to 2.5 diameters is greater by a factor of 3.4, which falls almost halfway between their lower values of 3 to 4. At the higher liquid rates, the factor was about 1.5 Basing their coefficients on area again, this shows the 8.5 diameter co efficients to be about 2 times larger than the 2.5 diameter ones at the higher rates. This is more interesting because they would then have larger coefficients in deeper packed beds. Ufford and Perona cited Porter and Temple man (1968) as having verified that the propor tion of liquid flowing down the wall decreased as the ratio of the column diameter to the pack ing particle diameter increased and as the liquid rate increased. They then state that the Berl saddles, according to Porter and Templeman, should be 2 to 3 times larger than the rings. Ac tually, they should be 1.5 to 3 times larger. As Ufford and Perona stated, Porter and Templeman did not employ a countercurrent or concurrent flow, but a stagnant gas phase. There was, there fore, a considerable lack of turbulence effect on their conclusion. This was, apparently unknow ingly, indirectly concluded by Ufford and Perona, who stated, "Hence wall flow alone does not appear to explain this effect, CRITICAL SUMMARY T HE RESULTS OF the above workers appear consistent in concurrent flow, and in compari son with countercurrent flow with respect to the values of the transfer coefficients. As generally expected, countercurrent coefficients were as much SPRING 1976 as 4 times more than the corresponding concur rent coefficients. The coefficients investigated covered ranges of liquid rates up to about 66,100 lb / hr-ft2, and gas rates from 43 to 230 lb / hr-ft 2 For the CO 2 -air-water system, the Ufford and Perona correlation for 1 / 4and 1 / 2-inch Raschig rings, and 3 / 4 inch Berl saddles in the form of kLa = CUG is an acceptable relation for design use in its proper flowrate regime. It has been stated (Ufford and Perona) that recent interest and development in the field of gas-liquid reactions in packed beds has stimulated concurrent flow mass transfer research. We do not feel that the CO 2 -air-water system is typically common in industry or unique. From a literature survey, it is apparent that the system seems a bit overwork ed. It would have been more pertinent and infor mative for our comparison if research had been reported on such systems as H 2 S-water absorp tion, CS 2 scrubbing, or NH 3 absorption. From our survey of the literature, NH 3 absorption would have been more straightforward as an example of a simultaneous absorption and chemical re action system. It should be noted that the packings used in the various work reported above by no means cover the sizes and types of packing currently available and used in the chemical process in dustry. As such, it is difficult to arrive at con crete relations showing the mass transfer co efficients dependence on liquid flow rate and gas flow rate. In general, it can be seen that since the liquid rate dependence is non-linear, there must be a gas-liquid rate interdependence. Ufford and Perona appear to be the first to present gas rate dependency work. We feel that packed column mass transfer coefficients would be more representative and easier to interpret with respect to packing height if they are reported as being independent of packing weight. Ufford and Perona drew certain conclusions about packing height effects that were shaded by coefficient dependence on packing height. They also made comparisons with other papers that were supposed to be general in na ture, but the other papers were specific about what they covered and, therefore, did not allow generalities to be drawn. A more general concurrent mass transfer co efficient relation must await further work using a wide variety of present day packings and different systems from both simple gas absorp tion and simultaneous absorption and chemical re action situations. 103


NOMENCLATURE a Local inter:facial area per unit volume of column, ft 2 a 0 Packing surface area per unit volume, ft1 D Diffusivity, ft2/sec. DP Equivalent spherical particle diameter, DP=6(l e) /a 0 ft. E Ene rgy dissipation per unit volume, lbcft/ft 3 -sec. G Gas flow rate per column cross-sectiona l area, lb/hr-ft 2 gc Conversion constant, 32.2 lbm-ft/lbcsec 2 H Henry's Law constant, pressure units. H 0 L Overall height of a mass transfer unit based on the liquid phase, ft. or in. K Overall mass transfer coefficient, lb/hr-ft 2 k Mass transfer coefficient based on film driving force, lb/hr-ft2. L Liquid flow rate per column cross-sectional area, lb/ hr-ft 2 N Rate of transport of gas into liquid phase per unit area of contact, lb/hr-ft 2 NOL Overall number of mass transfer units based on the liquid phase. P Pressure, pressure units. Re Reynolds number, DPV pl ,(1 e). S Column cross-sectional area, ft 2 V Super fi cial velocity, ft/sec. x Liquid-phase mole fraction, moles solute/moles liquid. y Gas-phase mole fraction, moles solute/moles gas. Z Packed column height, ft. or in. a Ergun constant used by Reiss (1967). /3 Ergun constant used by Reiss (1967). F ri ctional p ress ure gradient, p.s.i./ft e Packing void fraction used by Reiss (1967). Fluid viscosity, lb/hr-ft. p Fluid density, lb/ft 3 SUBSCRIPTS e Based on equilibrium. G Based on the gas phase. BOOKS: Continued from page 93. specifically to measurement methods such as those involving sieving, sedimentation (both gravita tional and centrifugal), radiation scattering, electrical sensing, permeametry, adsorption, and the like. The book suffers the common failing of many today because of delay between preparation and publication; few references are latter than 1972 Nevertheless, it alone is nearly current in the field; earlier works are severely outdated. Applied Optimal Control-Optimization, Estima tion, and Control. (Revised Printing) A. E. Bryson, Jr. and Yu-Chi Ho. Re vise d printing. The Halsted Press, John Wiley & Sons. New York, 1975. 481 pages. This widely acclaimed and used textbook in op timal control is now available in a revised print ing from the Halsted Press. 104 g Based on the gas phase. Based on interfacial contact. L Based on the liquid phase. l Based on the liquid phase. lg Based on the gas-liquid phases combined. x Based on the liquid phase. y Based on the gas phase. 1 Entrance to the packing. 2 Exit from the packing. SUPERSCRIPT Based on the liquid phase in equilibrium with the bulk gas phase. REFERENCES Allen, H. V., M .S. Th esis, M.I.T., 1938. Danckwerts, P. V., and A. J. Gillham, T1 ans. In stn Chem. Engrs., (Brit.), 44, T42 (1966). Dodds, W. S., L. F. Stutzman, B. J. Sollami, and R. J. Mc Carter, AIChE Journal, 6, 197 (1960). Higbie, R., T rans. Am e 1 Inst. Chem Engr., 31, 365 (1935). Koch, H. A., Jr ., L. F. Stutzman, H. A. Blum and L. E. Hatchings, Chem. Engr. Prag., 45, 677 (1949). Mcllvriod, H. G., Ph.D. Dissertation, Carnegie Inst. Tech., Pittsburgh, Pa., 1956. Porter, K. E., and J. J. Templeman, Tran s. In stn. Chem Eng1 s., (Brit.), 46, T86 (1968). Reiss, P. L., Ind. Eng. Chem. Process Des. Devel., 6, 486 (1967). Sherwood, T K., and F. A. L. Holloway, Trans. Amer. Inst. Chem. Engr., 36, 39 (1939). Treybal, R. E., "Mass Transfe r Operations," McGraw-Hill, N.Y. (1967). Ufford, R. C., and J J. Perona, AIChE Journal, 19, 1223 (1973). Van Winkle, M., "Distillation," McGraw-Hill, N.Y. (1967). Wen, C. Y., W. S. O'B rien, and Liang-Fseng Fan, J. Chem. Engr. Data, 8, 47 (1963). Tables on the Thermophysical Properties of Liq uids and Gases in Normal and Dissociated States, 2nd Ed. N. B. Vargaftik Halsted Press, New York, 1975. 758 pages. This extensive work presents thermodynamic and transport properties of a wide range of ma terials in the liquid, gaseous, dissociated and ionized states over a wide range of temperatures and pressures. The listed properties of pure sub stances in Part 1 include hydrogen and hydrogen compounds; metals ; carbon compounds; hydro carbons and organic compounds; nitrogen and ammonia; oxygen; sulfur dioxide; halogens; monoatonic gases. Part 2 presents properties of mixtures and includes air; diffusion in gases; thermodiffusion in gases ; thermophysical proper ties of gas mixtures and solutions; liquid fuels; high temperature heat transfer agents; and oils. CHEMICAL ENGINEERING EDUCATION


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