Group Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Title: 3.3.2 - Experimental Investigations of Particle Distribution and Desanding Efficiency of Solid-liquid/Gas-Liquid-Solid Separation in Helical Pipe with Gradually Changed Curvatures
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Permanent Link: http://ufdc.ufl.edu/UF00102023/00080
 Material Information
Title: 3.3.2 - Experimental Investigations of Particle Distribution and Desanding Efficiency of Solid-liquid/Gas-Liquid-Solid Separation in Helical Pipe with Gradually Changed Curvatures Industrial Applications
Series Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Physical Description: Conference Papers
Creator: Guo, L.J.
Pan, D.
Hu, X.W.
Zhang, X.M.
Publisher: International Conference on Multiphase Flow (ICMF)
Publication Date: June 4, 2010
 Subjects
Subject: helical pipe
desanding
solid-liquid/gas-liquid-solid
particle distribution
 Notes
Abstract: Helical pipe desanding separator is a new type of multiphase separation device with low-pressure loss and high efficiency of desanding. A new structural helical pipe desanding separator with gradually changed curvatures is introduced in this paper. In order to improve the desanding efficiency, the investigation of particle distribution in solid-liquid/gas-liquid-solid flow in helical pipe separation equipment was experimentally carried out. The influences of curvature, liquid velocity, particle volume fraction were investigated in solid-liquid separation experiments. And the influence of gas phase was also studied in gas-liquid-solid separation experiments. Furthermore, the experiments of single-stage and multi-stage desanding in solid-liquid/gas-liquid-solid flow were carried out respectively and the feasibilities of multi-stage desanding method were studied, which gives an important reference to optimization design for the helical pipe separator.
General Note: The International Conference on Multiphase Flow (ICMF) first was held in Tsukuba, Japan in 1991 and the second ICMF took place in Kyoto, Japan in 1995. During this conference, it was decided to establish an International Governing Board which oversees the major aspects of the conference and makes decisions about future conference locations. Due to the great importance of the field, it was furthermore decided to hold the conference every three years successively in Asia including Australia, Europe including Africa, Russia and the Near East and America. Hence, ICMF 1998 was held in Lyon, France, ICMF 2001 in New Orleans, USA, ICMF 2004 in Yokohama, Japan, and ICMF 2007 in Leipzig, Germany. ICMF-2010 is devoted to all aspects of Multiphase Flow. Researchers from all over the world gathered in order to introduce their recent advances in the field and thereby promote the exchange of new ideas, results and techniques. The conference is a key event in Multiphase Flow and supports the advancement of science in this very important field. The major research topics relevant for the conference are as follows: Bio-Fluid Dynamics; Boiling; Bubbly Flows; Cavitation; Colloidal and Suspension Dynamics; Collision, Agglomeration and Breakup; Computational Techniques for Multiphase Flows; Droplet Flows; Environmental and Geophysical Flows; Experimental Methods for Multiphase Flows; Fluidized and Circulating Fluidized Beds; Fluid Structure Interactions; Granular Media; Industrial Applications; Instabilities; Interfacial Flows; Micro and Nano-Scale Multiphase Flows; Microgravity in Two-Phase Flow; Multiphase Flows with Heat and Mass Transfer; Non-Newtonian Multiphase Flows; Particle-Laden Flows; Particle, Bubble and Drop Dynamics; Reactive Multiphase Flows
 Record Information
Bibliographic ID: UF00102023
Volume ID: VID00080
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: 332-Guo-ICMF2010.pdf

Full Text

Paper No 7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010


Experimental Investigations of Particle Distribution and Desanding Efficiency of
Solid-liquid/Gas-Liquid -Solid Separation in Helical Pipe with Gradually Changed
Curvatures


Liejin Guo, Dong Pan, Xiaowei Hu and Ximin Zhang

State Key Laboratory of Multiphase Flow in Power Engineering, Energy and Power Engineering, Xi'an Jiaotong University
Xianning West Road 28#, Xi'an, 710049, China
lj-guo@mail.xjtu.edu.cn


Keywords: Helical pipe, desanding, solid-liquid/gas-liquid-solid, particle distribution




Abstract

Helical pipe desanding separator is a new type of multiphase separation device with low-pressure loss and high efficiency of
desanding. A new structural helical pipe desanding separator with gradually changed curvatures is introduced in this paper. In
order to improve the desanding efficiency, the investigation of particle distribution in solid-liquid/gas-liquid-solid flow in
helical pipe separation equipment was experimentally carried out. The influences of curvature, liquid velocity, particle
volume fraction were investigated in solid-liquid separation experiments. And the influence of gas phase was also studied in
gas-liquid-solid separation experiments. Furthermore, the experiments of single-stage and multi-stage desanding in
solid-liquid/gas-liquid-solid flow were carried out respectively and the feasibilities of multi-stage desanding method were
studied, which gives an important reference to optimization design for the helical pipe separator.


Introduction

In the process of petroleum extraction, because of the
oil-layer erosion to the earth crust, crude oil mixture carries
sand inevitably. The existence of sand does not only
influence the performance of some subsequent technologies
such as measurement, heating, dehydration, separation, but
also severely harms the service life and operation of pump,
pipeline system and measuring instrument. So the desanding
must be carried out in advance. At present, the general
desanding technology applied in the crude oil production is
gravity desanding and hydroclone desanding. But some
obvious shortcomings exist in the two popular technologies.
For example, in gravity desanding, it needs large space and
eliminating sedimentation at tank bottom periodically which
make against for production continuously. While in
hydroclone desanding, it needs multiphase pump to drive
due to large drag. And because of the sand abrasion to the
multiphase pump, the desanding running costs, including the
dissipation and power consumption of multiphase pump,
increase.
Against the drawbacks of the above desanding technologies,
a new type of device, helical pipe separator was developed
in State Key Laboratory of Multiphase Flow in Power
Engineering (Guo 2002).The device utilizes the power
provided by the remaining pressure of oil well to drive the
high rate rotational flow of crude oil mixture in the helical
pipe. The density difference leads to the difference in
centrifugal forces among the four phases of oil, gas, water
and sand in crude oil mixture. And due to the effects of
centrifugal force, a stratified flow with sand moving at the


bottom along the wall appears in the helical pipe. On the
helical pipe, desanding orifices with a special configuration
have been installed previously. A high economical
efficiency can be achieved by the proper water yielding
through the desanding orifices. And the general research of
separation mechanics has been studied widely in our
laboratory since the proposition of the technology. At
present, the research about simplified models in horizontal
curved pipe, single-coil helical pipe has obtained a great
achievement (Chen & Guo 1999, Gao & Guo et al. 2002,
Gao 2003, Gao & Guo 2004, Zhao 2004). Because of
helical pipe separation with the characteristics of high
removal efficiency, low-pressure loss, it shows a great
development potential and application prospect in
solid-liquid separation of chemical industry and
environmental protection with the further development of
the technology.
In order to understand the technology characteristics of
phase separation in helical pipe, and to search for a helpful
helical pipe configuration to enhance the phase separation, a
new helical pipe structure with gradually changed
curvatures has been proposed in this paper based on the
original helical pipe. And both the experiments of
solid-liquid two-phase flow and gas-liquid-solid three-phase
flow have been carried out. By the experimental
investigation of solid-liquid two-phase flow in the new type
of helical pipe, the effect of gradually changed helical pipe
curvatures on phase separation has been reviewed, and the
influences of operating parameters, such as liquid mean
velocity, particle phase fraction on particle phase
distribution in helical pipe can be understudied further more.






Paper No


Through the experimental investigation of gas-liquid-solid
multiphase flow and phase separation phenomena of this
new pipe type, we can not only understand the technology
characteristics of multiphase separation in helical pipe, but
also can search for the helical pipe structure which is helpful
for multiphase separation for optimum design of helical pipe
separator.
Further more, single-stage in solid-liquid two-phase flow
and multi-stage in gas-liquid-solid three-phase flow
desanding experiments are carried out. And the feasibility of
multi-stage desanding in helical pipe separator is reviewed
for the optimum design.

Nomenclature


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

and gas-liquid-solid three-phase flow of all kinds of flow
patterns, and generate large pressure head with wider range
of experimental parameters.
Malvern particle size analyzer can measure the particle size
distribution through Fourier optics diffraction principle and
can measure particle average volume concentration in
channels. And its measurement range for particle size is
controlled by lens focus. The focus of lens used in this
experiment is 300mm, and the measurement range for
particle size is 5.8-564pm.Malvern particle size analyzer is
set on the frame of axes. The frame of axes can be moved
along the normal direction. And the particle concentration
and size distribution along the curvature radius direction can
be measured on the cross section.


superficial velocity (m s-')
concentration
curvature radius (m)


Subsripts
g gas
w water
p particle
av average
o outside
i inner side

Experimental Facility


Figure 1: Solid-liquid/gas-liquid-solid multiphase flow
experimental system: 1 water pump; 2 water tank; 3
waterway flowmeter; 4 air compressing engine of
solid-liquid mixing arrangement; 5 particle transport and
measuring device; 6 solid-liquid on-line mixer; 7 airway
compressor; 8 airway flowmeter; 9 gas-liquid-solid mixer;
10 experimental section; 11 solid-liquid filter separator ; 12
gas-liquid cyclone separator; P manometer.

The experimental system includes solid-liquid/gas-
liquid-solid experimental loop, Malvern particle size
analyzer measuring system and experimental section of
helical pipe with gradually changed curvatures. Fig. 1
presents the solid-liquid/gas-liquid-solid multiphase flow
experimental system developed in our laboratory, which
includes material adding system of gas/liquid/solid phase,
mixing section of three phases, experimental section and
recovery system of the three phases. This experimental
system can measure the flow rate of each phase precisely,
generate solid-liquid two-phase flow with uniform mixing


Figure 2: Helical pipe configurations with combined
gradually changed curvatures

Fig. 2 presents the helical pipe structure with combined
gradually changed curvatures. In this paper, the gradual
change of curvature radius is achieved by approximation of
multi-grade combined radius with gradual deceasing in the
flow direction. Though the configuration is not a helical
pipe with gradually changed curvatures strictly, as for the
experimental purpose of investigating the effects of
curvature change on phase distribution, the approximation
method is suitable.
The experimental section includes inlet straight section,
curved section of measurement, outlet curved section and
outlet straight section. Three observation locations, 180,
5400 and 9000 observation windows, are set on the curved
section of measurement. The two sides of observation
windows are made up of optical glass for the measurement
of Malvern particle size analyzer and observation of flow
patterns.
The difference in curvature radius of each-grade curved pipe
of curved section is 22.5mm. And the curvature radius for
observation windows of 1800, 5400 and 9000 are 172.5mm,
127.5mm, 82.5mm respectively. And the curvature radius
ratios with a wider variation range are 2.09: 1.55: 1, which
can reflect the effects of curvature radius on particle phase
distribution clearly in the experiment. There is a desanding
orifice in the downstream 300 direction of each observation
widow for the desanding experiment.
The particle size in the experiment is 50-300pm, and the
density is about 2500kg/m3. Experimental conditions
include four liquid mean velocities of 0.837m/s, 1.34m/s,
2.01m/s, 2.68m/s, and three particle phase concentrations of
0.05%, 0.1%, 0.15%.






7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010


Results and Discussion

(1)Phase distribution in solid-liquid two


U =1.34m/s,C =0.10%
* w.m p.av


S
4
.- -*


0.2 0.4 0.6
(Ro-R)/(Ro-R,)


Figure 3: Effects of
particle phase distribution


2.0-

1.8.

1.6.

1.4.

1.2

1.0-

0.8-

0.6-

0.4
fly '


gradually changed


180,CP =0.10%
pav


- 0.837
-*1.34r
2.01r
- 2.68r


0.0 0.2 0.4 0.6
(R-R)/(R-R,)


by the secondary flow again, and move around the inner
side of the helical pipe, the final separation degree of solid
s-phase flow and liquid decreases.
So if the curvature gradually increase during the flow, the
1800 decreasing of secondary flow is more significant than that of
5400 centrifugal force. And the particles overcoming the
00 entrainment by secondary flow under the interaction of
9000
centrifugal force will increase. More and more particles will
accumulate at the outside of the helical pipe and the
solid-liquid separation effect will be improved with the
curvature increasing.
Fig. 4 presents the effects of liquid mean velocity on
particle phase distribution. Generally, the phase separation
can be enhanced by increasing liquid mean velocity. When
the liquid velocity varies in a low or moderate range, the
enhancement of phase separation is obvious. For example,
liquid velocity varies from 0.837m/s to 1.34m/s and then to
2.01m/s, particle phase concentration distribution curve
0.8 1.0 varies greatly. When the liquid velocity achieves some
degree (2.01m/s), phase separation enhancement by
curvature on increasing liquid velocity is limited. For example, the
particle phase concentration distribution curves with liquid
velocities of 2.01m/s and 2.68m/s are close, almost
7m/s superposition. The phenomenon indicates the increasing of
m/s liquid velocity is helpful for phase separation. But the
n/s enhancement by increasing liquid velocity is limited. The
m/s enhancement for phase separation is not obvious when the
liquid velocity increases further more after some degree.
The reason for limited enhancement of phase separation by
increasing liquid velocity may be as follows: with the
velocity increasing, the leading of centrifugal force causes
the increasing of particle phase concentration at the outside
of helical pipe. And the interactions between particles
enhanced correspondingly. When the local particle
-a concentration is up to some value or the distance between
particles closes to some degree, interactions between
_I particles will be large, which makes it hard to improve
0.8 1.0 particle phase concentration by centrifugal force application
with increasing velocity any more.


Figure 4: Effects of liquid mean velocity on particle phase
distribution

From a theoretical aspect, centrifugal force is in inverse
proportion to the rotating radius. When the curvature radius
decreases continuously, the particle centrifugal force should
increase and the separation effects between solid and liquid
will be enhanced. However, in fact, the experimental result
is not the same. Fig. 3 presents the effects of gradually
changed curvature on particle phase distribution. With the
decreasing of curvature radius, the particle phase
concentration on the outside of helical pipe decreases
continuously, while the concentration of inner side increases
continuously, which means the curvature decrease weakens
the phase separation between the solid and liquid. The
proper reason for this phenomenon may be as follows: in the
process of curvature decreasing, though the particle
centrifugal force is increasing continuously, meanwhile the
secondary flow intensity of liquid phase is increasing
correspondingly too. And the increase of secondary flow
intensity is more significantly than that of centrifugal force.
During the flow, the particles overcoming centrifugal force
and entrained by the secondary flow will increase. Because
the particles separated by centrifugal force will be entrained


2.0-

1.8.

1.6.

1.4-

S1.2.

1.0.
C-)
0.8.

0.6.

0.4.

0.2
0.0


Uw,m=1.34m/s,540


t


-*0.05%
-*0.10%
- 0.15%


A k
*---- A


-i


0.2 0.4 0.6
(Ro-R)/(Ro-R)


0.8 1.0


Figure 5: Effects of particle phase average concentration on
particle phase distribution

Fig. 5 presents the effects of particle phase average
concentration on phase distribution. In the figure, the
influence of particle phase average concentration on particle


Paper No


- n


-
.






7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010


phase distribution in helical pipe is generally small.
However, with the particle phase average concentration
increasing, the solid-liquid separation decreases a little.
Under each flow condition in Fig. 5, with the particle phase
average concentration increasing, particle phase
concentration decreases at the outside of helical pipe, and
increases at the inner side. As discussed above, the reason
for this phenomenon is that the lower of particle phase
average concentration, the smaller of the interactions
between particles. And it is easier for particle phase to
accumulate at the outside. So the separation effect is better.
The phenomenon indicates the low particle phase average
concentration is helpful for the solid-liquid separation in
helical pipe.

(2)Phase distribution in gas-liquid-solid two-phase
flow

Based on the former research (Guo 2002), the optimum
separation of gas-liquid-solid three-phase in separator can
be obtained in steady stratified flow. So in order to ensure


the proper range of experin
experimental investigation for flov
out before the phase distribution
liquid-solid three-phase in helic
changed curvatures. Due to the lov
particle phase in this experiment (a
particle phase on two-phase flow
And only the experimental in
two-phase flow is carried out.


0.5+
0.0


0.5 1.0
J


9(m/s


J0.0
0.0 0.5 1.0
J (m/s)


3.0.

2.5 z

2.0.
E
S1.5

1.0.

0.5
0.0


n INT-ST
SSLGU
ST
ANU
900o


0.5 1.0 1.5 2.0 2.5
Jg(m/s)


Figure 6: Gas-liquid two-phase flow patterns through each
observation window of helical pipe with gradually changed
curvatures


mental parameters, the Fig. 6 presents the gas-liquid two-phase flow patterns
w pattern must be carried through each observation window of helical pipe with
in measurement of gas- gradually changed curvatures. The helical pipe with
al pipe with gradually gradually changed curvatures was laid horizontally (axis of
v volume concentration of helical line was horizontal with the ground). Due to the
bout 0.1%0), the effects of angles between the gravity forces and the centrifugal forces
pattern can be neglected. acting on the liquid and gas are varied with the locations of
investigation in gas-liquid helical perigon, the variation of the flow pattern is very
complicated. From Fig. 6, we can see that the flow patterns
in helical pipe with gradually changed curvatures include
INT-ST interminate stratified flow (INT-ST), stratified flow (ST),
SLGU slug flow (SLUG) and annular flow (ANU) in the
ST
S ANU experiment.
180 When the liquid velocity is low, only the interminate
4 4 4 4 stratified flow (INT-ST) appears whatever the gas rate
changes. Especially when the gas rate is lower, the slug flow
(SLUG) will be obtained. When the liquid velocity
. increases, stratified flow appears, and the range for stratified
. flow becomes wider. However, when the liquid velocity
. increases to some value, the range becomes small. And a
. transition flow from bubble annular flow (ANU) exists
between the stratified flow (ST) and interminate flow
I. I I (INT-ST).
1.5 2.0 2.5 From the aspect of pattern distribution, the area of stratified
) flow is the biggest through 900 0 observation window, and
the second biggest through 5400 observation, smallest in
. . INT-ST 1800, which indicates that with the decreasing of the
SLGU
.... n ST curvatures, the gas-liquid two-phase flow becomes more
v ANU stable. From the aspect of range for flow condition, the flow
540' condition range of interminate flow is the widest and ranges
of stratified flow, slug flow are the second, and annular flow
is the smallest.
Fig. 7 presents the influences of void fraction on particle
S. phase concentration distribution in stratified flow. In most
flow conditions, solid-liquid separation with adding gas has
been improved compared to that without gas. Particle phase
concentration at outside of helical pipe with adding gas
. almost increases, while particle phase concentration at inner
15 0 2 5 side of helical pipe decreases. The reason may be as
follows: after adding gas, the gas phase occupies part of the
flow section, which makes the liquid velocity and the
centrifugal force increasing; meanwhile, the depth-width


Paper No


n i-


I






7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010


ratio of flow section decreases, which weakens the particle
entrainment by secondary flow. Under the interaction of the
two effects above, the accumulating of particle phase on the
helical pipe outside enhances, and the phase separation
effect is improved.
In the figure, under each liquid velocity, the solid liquid
separation has been enhanced in some degree with the
increase of the void fraction. With the low flow rate, due to
the apparent increase of void fraction, the separation
enhanced apparently as well; while with the high flow rate,
due to the less increase of void fraction, the phase separation
enhanced less as well.


20 J =0.247m/s

1.8 --J ==0.494m/s
J =0.741 m/s
1.6 -- without gas


1.4-

1.2-

1.0.
O
C-)
0.8-

0.6-

0.4.

0.2 -
0.0






2.0-

1.8-

1.6-

1.4-

1.2-

S1.0
C-
0.8-

0.6-

0.4-

0.2
0.0


I~


-V


V,


0.2 0.4 0.6 0.8 1.0
(Ro-R)/(Ro-R)
Jw=1.34m/s,C av=0.10%,1800


- J =0.247m/s
- J =0.494m/s
J =0.741m/s
- without gas


SA


V


0.2 0.4 0.6 0.8 1.
(Ro-R)/(Ro-R)

Jw=1.34m/s,C =0.10%,5400
w 'p av


2.0-

1.8-

1.6-

1.4.

1.2.

a 1.0.

0.8

0.6-

0.4.

0.2-
0.0


V


-V
F~~T
* __
"~-


0.2 0.4 0.6
(Ro-R)/(Ro-R,)


J =1.34m/s,C =0. 10%,9000
w p av


2.0-

1.8.

1.6.

1.4.

1.2

1.0.

0.8

0.6.

0.4.

0.2-
0.0





2.0-

1.8.

1.6.

1.4-

S1.2

S1.0.

0.8.

0.6

0.4

0.2-
0.0


- J =0.247m/s
* J =0.494m/s
J =0.741m/s
v- without gas


0.2 0.4 0.6 0.8
(Ro-R)/(Ro-R)
J =2.68 m/s,C a=0.10%,1800
w p av


- J =0.247m/s
* J =0.494m/s
J =0.741m/s
- without gas


V


",
rT


0.2 0.4 0.6 0.8 1 .
(Ro-R)/(Ro-R)
Jw=2.68 m/s,Cp =0.10%,5400
w 'p av


Paper No


* J =0.247m/s
* J =0.494m/s
J =0.741m/s
v-without gas


0.8 1.0


-


-V.






7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010


Paper No




2.0-

1.8-

1.6-

1.4-

1.2.

O1.0.

0.8.

0.6

0.4

n 9. -


- J =0.247m/s
SJ =0.494m/s
J =0.741t as
v- without gas


0.0 0.2 0.4 0.6 0.8 1.0
(Ro-R)/(Ro-R)
J =2.68 m/s,C pv=0.10%,9000
Figure 7: Effects of void fraction on particle phase
concentration distribution in stratified flow



2.0-
1800
S1.8- 5400
S9000


0.2 0.4 0.6
(Ro-R)/(Ro-R)

Jw=1.34m/s,Jg=0.247m/s,Cpav=0.10%
w g p,av


-*180'
* 540'
900'


2.0-

1.8.

1.6.

1.4.

S1.2.

1.0.

0.8-

0.6

0.4

0.2-
0.0







2.0-

1.8.

1.6.

1.4.

1.2

1.0.

0.8-

0.6t

0.4

0.2-
0.0


- 180
* 540'
900o


2.0-

1.8-

1.6-

1.4.

1.2.

1.0.

0.8-

0.6j

0.4

0.2
0.


* 1800
* 5400
9000


0.2 0.4 0.6 0.8 1.0
(Ro-R)/(Ro-R)

Jw=2.68m/s,J =0.247m/s,C pav=0.10%


* 1800
*-5400
9000


0.2 0.4 0.6 0.8 1.0
(Ro-R)/(Ro-R)

Jw=2.68m/s,Jg=0.494m/s,Cav=O.10%
w 'g p,av


0.2 0.4 0.6
(Ro-R)/(Ro-R,)
Jw=1.34m/s,Jg=0.741 m/s,Cpav=0.10%
w g p,av


1.6-

1.4-

1.2

1.0

0.8.

0.6

0.4

0.2-
0.0


2.0-

1.8.

1.6-

1.4-

1.2-

O 1.0.
o
0.8-

0.6-

0.4-

02.


0.0 .2 04 0.


0.0 0.2 0.4 0.6
(Ro-R)/(Ro-R)
Jw=1.34m/s,Jg=0.494m/s,Cpav=0.10%


r-
.


-*






Paper No


K.


0.0 0.2 0.4 0.6 0.8 1.0
(Ro-R)/(Ro-R)
J =2.68m/s,J =0.741 m/s,Cp =0.10%
w g p,av
Figure 8: Effects of void fraction under different curvatures
on particle phase distribution

Fig. 8 presents the effects of void fraction under different
curvatures on particle phase distribution. With the increase
of void fraction, the separation enhanced more rapidly at
small curvatures of helical pipe. As shown in the figure, at
the beginning of adding gas, the liquid velocity slightly
increases due to the less gas, so the separation in curved
pipe remains the state that the separation at 1800 observation
is better than that at 5400 and better than that at 9000. With
the gradual increase of gas rate, the phase separation state in
curved pipe has changed gradually into the state that the
separation at 9000 observation is better than that at 5400 and
better than that at 1800.
So the separation effect at 1800 observation improves
slowly. Firstly, helical pipe with gradually changed
curvatures was laid horizontally in the experiment. When it
starts adding gas, during the first circle of curved pipe, a
transfer process of gas phase from outside to inner side
appears firstly. And the process will enhance the particle
perturbation in the curved pipe and counteract part of the
positive effects of gas rate increasing. So the separation
effect at 180 0 observation improves slowly with the
increasing of void fraction ; While no gas transfer process
existing at large curvature, the separation improved rapidly.
Further more, we can understand from the above analysis
that the separation effect at 5400and 900 observation after
adding gas enhanced with the decreasing of curvature. The
depth-width ratio of flow section decreases due to the gas
adding. Based on the former research (Gao 2003), the
secondary flow intensity is low in the flow section with a
small depth-width ratio. So gas adding decreases the
secondary flow intensity of liquid phase generally. On the
other side, under the double effects of curvature decreasing
and liquid mean velocity increasing, the increasing of
particle centrifugal force is more rapid than that of
secondary flow intensity. And the enhancement of
centrifugal force is the lead. Thirdly, with the gradual
decreasing of curvature, the stratified flow of gas-liquid is
becoming more and more steady, which decreases the effect
of gas-liquid interface fluctuation on solid-liquid separation.
And the existing of gas will suppress the secondary flow of
liquid phase on some degree. Under the interaction of the


1 2.

S10.
o
08.

06.

04.

02


- 1800
-*5400
9000


N -


S


0o2 0 4 06
(R,-R)/(R,-R)


0 8 10


Figure 9: Particle phase concentration distribution at each
inlet of desanding orifice


30.


25.


20.

.2

C
U)
5.
w
5n


- 2100 desanding orifice
- 5700 desanding orifice
9300 desanding orifice


u I .
0 2 4 6 8 10 12 14
Water Yielding Rate [%]
Figure 10: Desanding efficiency at different desanding
orifices under different water yielding rates

In order to investigate the desanding efficiency of each
desanding orifice, each desanding orifice configuration
should be the same, which means the particle phase
concentration at desanding orifice inlet should be uniform.
So a test experiment for each orifice was carried out under
the flow conditions of liquid mean velocity 2.68m/s, and
particle phase average concentration 0.1%. Fig. 9 presents
the particle phase distributions at the inlet of three
desanding orifices. And we can see that particle phase
concentrations at different stage desanding orifices are
almost uniform, which meets the experimental
requirements.
Fig. 10 presents the experimental results of desanding
efficiencies at different desanding orifices under different
water yielding rates. We can see that the variations of
desanding efficiencies at three desanding orifices against


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

three factors, the phase separation at small curvature
improved more significantly than that at large curvature,
which indicates the helical pipe with gradually changed
curvatures can enhance the separation between liquid and
solid in the stratified flow of gas-liquid-solid flow.

(3)Desanding efficiency


- 1800
* 5400
9000


* -.






Paper No


water yielding rates are almost uniform, which indicates that
each desanding orifice configuration reaches a great
uniformity. And the desanding efficiencies at each orifice
under different work conditions can represent the particle
accumulation around the orifices.

3.50 1


5 15


w 10


s-


0-2.5 2.5-5 5-7.5 7.5-10 10-12.5


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

desanding efficiency means desanding efficiency relative to
that of each stage inlet.

--


m 2.s/


o
210 57) 931
Cesandi g Cr if ice Locatin

Figure 12: Total desanding efficiency of each orifice under
different water yielding rates


water yielding rate [%]
Figure 11: Relative desanding efficiency at each desanding
orifice (desanding efficiency/water yielding rate)

Fig. 11 indicates the corresponding desanding efficiency
with each 1% water yielding rate under each variation range
of water yielding rates. From the figure we can know
desanding efficiency increases more rapidly as the water
yielding rate increases within 7.5% and desanding efficiency
increases most rapidly in the range of 2.5 5% where
desanding efficiency increases about 3% as water yielding
rate increases each 1%. Desanding efficiency increasing
tendency becomes flat as the water yielding rate increases
from 7.5% where desanding efficiency increases no more
than 1% as water yielding rate increases each 1%. So we
can conclude that desanding efficiency of single-stage is
highest during the range of 2.5-5%.And the range of 5-7.5%
is still a high efficiency range. And the optimum water
yielding rate in this experiment is 7.5% under the range of
flow conditions.
Configuration difference in each desanding orifice has been
investigated in the above single-stage desanding experiment
and the variation characteristics of desanding efficiency for
each orifice against water yielding rate under the same gas
rate has been discussed too. For multi-stage experiment in
solid-liquid two-phase flow, feasibilities of multi-stage
desanding will be discussed based on controlling total water
yielding rate as a main parameter. And the total water
yielding rate will be controlled in a relative economical
range (within 25%). Because total water yielding rate can
achieve some setting value by different matching ways
between three desanding orifices, the water yielding rate of
each orifice is set almost the same for simplifying. The
solid-liquid two-phase flow parameters in this experiment
are as follows: liquid mean velocity is 2.68m/s and particle
phase average concentration is 0.1%. Fig. 12 presents the
total desanding efficiency of each orifice under different
water yielding rates and Fig. 13 presents staged desanding
efficiency of each orifice under different water yielding
rates. Total desanding efficiency means desanding efficiency
relative to that of experimental section inlet. Staged


S20


* 2.3/o
* 5.C0
l 7. 3/o


210" 570" 930"
Desanding Orifice Location
Figure 13: Staged desanding efficiency of each orifice
under different water drain rates

Figure 12 shows many characteristics of multi-staged
desanding : Under each different water yielding rate, total
desanding efficiency of 2100 desanding orifice is the highest,
and that of 5700 is the second while that of 9300 is the
lowest, which means total desanding efficiency decreases
with the increasing of stages. And desanding efficiency
decreases most rapidly between the first and second stage.
However, desanding efficiency between the second and
third stage decreases more slowly. And the difference
between the first and second stage becomes larger with
higher water yielding rate. Because desanding of each
stage decreases the inlet sand concentration and liquid
velocity of the next orifice, the absolute desanding amount
decreases with stages and difference between the first and
second increases with the water yielding rate.
Fig. 13 also indicates that relative desanding efficiency
decreases more slowly though the total desanding efficiency
of each orifice decreases rapidly, which means a strong
separation effects of solid-liquid exist in the last two orifices
of helical pipe. It also means that the separating ability of
helical pipe is very strong.


^





7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010


60


Figure 14: Comparisons of desanding efficiency between
single-stage and multi-stage

Fig. 14 presents the efficiency curves of single-stage
desanding and multi-stage desanding. The figure indicates
that when water yielding rate is above 7.5%, multi-stage
efficiency still keeps a high increasing speed with water
yielding rate while single-stage efficiency increases slowly.
That means in the range of high water yielding rate,
multi-stage desanding efficiency is higher than that of
single-stage.
The performance of multi-stage desanding can be affirmed
by the experiment in solid-liquid two-phase flow. However,
it requires matching water yielding rate of each orifice
properly in order to obtain an optimum economical
efficiency. And to obtain a high desanding efficiency, it not
only needs a higher separation degree between liquid and
solid, and also a proper orifice configuration of collecting
sand. The configuration of desanding orifice in this
experiment was not reasonable generally causing the low
total desanding efficiency.
In order to investigate the multi-stage desanding
performance characteristics with gas adding and multi-stage
desanding feasibilities of gas-liquid-solid three-phase, the
corresponding experiment has been carried out too. It bases
on superficial gas velocity as a variable, and the optimum
single-stage water yielding rate 7.5% as the controlling
water yielding rate for each desanding orifice (total water
yielding rate is 22.5%). The liquid mean velocity is 2.68m/s,
particle phase average concentration is 0.1%.
60 1 1


S50 -
50
5 40
S30 -
20

10
=
rm


0 0.123 0.274 0.494 0.741
Jg [m/s]
Figure 15: Effects of gas adding on desanding efficiency of
multi-stage


0 0.123 0.274 0.494
Jg(m/s)
Figure 16: Effects of gas adding on total
efficiency of each desanding orifice


0.741


desanding


* 210c


20




S10

S5
0 1


0 0.123 0.274 0.494 0.741


Jg [m/s]
Figure 17: Effects of gas adding on staged desanding
efficiency of each desanding orifice

The reason for the above phenomenon may be as follows:
part of the liquid amount will be lost in each orifice during
multi-stage desanding, which will influence the flow pattern
and stability. And the optimum separation effect and highest
desanding efficiency will be obtained with gas rate up to
some value making flow the most stably.
It can be concluded from the experiment that multi-stage
desanding of gas-liquid-solid is hard to control, and the


Paper No


Fig. 15 presents the effects of gas adding on multi-stage
--210 desanding orifice desanding efficiency of helical pipe with gradually
decreasing curvatures. It indicates that, at the beginning of
-- 570 desanding orifice gas adding, desanding efficiency decreases compared to that
-A 930 desanding orifice without gas. But with the increasing of gas adding,
efficiency firstly increases and then decreases. The
superficial gas velocity with 0.274m/s corresponds to the
highest desanding efficiency.
Fig. 16 and Fig.17 present the effects of gas adding on total
Sand staged desanding efficiency of each desanding orifice
/ respectively. The figures indicate total and staged demanding
efficiency of each desanding orifice both increase firstly and
then decrease with the increasing of gas. At the same time,
0 5 10 15 20 25 we can see the similar phenomenon in solid-liquid
Water Yielding Rate[%] two-phase flow that total desanding efficiency decreases
iAth ctaoea mTorer roniA11i than ctaol a c rlanaino afficrelnr-7


v l g pLt- 111 gU11 YLII ytL / L ll l 1.^ll t


" 11





Paper No


optimum work condition is not easy to obtain. So the
multi-stage desanding is not suitable for gas-liquid-solid
three-phase flow.

Conclusions

In this paper, a new type of helical pipe configuration with
gradually changed curvatures has been introduced in this
paper. And the particle phase concentration distributions of
liquid-solid/gas-liquid-solid flow in this pipe have been
measured by Malvern particle size analyzer. The influences
of gradually changed curvature, liquid mean velocity,
particle phase average concentration and void fraction on
particle phase distribution have been investigated deeply.
And Single-stage in solid-liquid two-phase flow and
multi-stage in gas-liquid-solid three-phase flow desanding
experiments are carried out. And the feasibilities of
multi-stage desanding in helical pipe separator are
investigated for the optimum design and operation of helical
pipe separator. In solid-liquid two-phase flow, the
performance of multi-stage desanding is better than that of
single-stage desanding. But it requires a reasonable water
yielding rate for an economical desanding efficiency; for the
gas-liquid-solid three- phase flow, the multi-stage desanding
is not suitable due to the difficulties in obtaining an
optimum working condition.

Acknowledgements

We gratefully acknowledge the National Science Foundation
of China (No. 50536020) and Research Program for
Excellent State Key Laboratory (No.50823002).

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7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010


Naphon P. & Wongwises S. A Review of Flow and Heat
Transfer Characteristics in Curved Tubes, Renewable &
Sustainable Energy Reviews, Vol. 10, 463-490 (2006)

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