U.S. patent application number 14/237814 was filed with the patent office on 2014-07-31 for separating oil and water streams.
The applicant listed for this patent is Per-Reidar Larnholm, Scott M. Whitney. Invention is credited to Per-Reidar Larnholm, Scott M. Whitney.
Application Number | 20140209465 14/237814 |
Document ID | / |
Family ID | 47914756 |
Filed Date | 2014-07-31 |
United States Patent
Application |
20140209465 |
Kind Code |
A1 |
Whitney; Scott M. ; et
al. |
July 31, 2014 |
Separating Oil and Water Streams
Abstract
Embodiments described herein provide a system and methods for
separating oil and water streams. The method includes separating a
fluid stream into an oil continuous stream and a water continuous
stream using a cyclonic separator, flowing the oil continuous
stream to a first gravity separation vessel, and flowing the water
continuous stream to a second gravity separation vessel. The method
also includes separating the oil continuous stream in the first
gravity separation vessel into an oil stream and a water stream and
separating the water continuous stream in the second gravity
separation vessel into an oil stream and a water stream.
Inventors: |
Whitney; Scott M.; (Missouri
City, TX) ; Larnholm; Per-Reidar; (Moss, NO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Whitney; Scott M.
Larnholm; Per-Reidar |
Missouri City
Moss |
TX |
US
NO |
|
|
Family ID: |
47914756 |
Appl. No.: |
14/237814 |
Filed: |
August 31, 2012 |
PCT Filed: |
August 31, 2012 |
PCT NO: |
PCT/US12/53409 |
371 Date: |
February 7, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61537317 |
Sep 21, 2011 |
|
|
|
Current U.S.
Class: |
204/555 ;
204/554; 204/666; 210/252; 210/788 |
Current CPC
Class: |
E21B 43/34 20130101;
C10G 33/06 20130101 |
Class at
Publication: |
204/555 ;
210/788; 204/554; 210/252; 204/666 |
International
Class: |
E21B 43/34 20060101
E21B043/34 |
Claims
1. A method for separating oil and water streams, comprising:
separating a fluid stream into an oil continuous stream and a water
continuous stream using a cyclonic separator; flowing the oil
continuous stream to a first gravity separation vessel; flowing the
water continuous stream to a second gravity separation vessel;
separating the oil continuous stream in the first gravity
separation vessel into a first oil stream and a first water stream;
and separating the water continuous stream in the second gravity
separation vessel into a second oil stream and a second water
stream.
2. The method of claim 1, further comprising: combining the first
oil stream and the second oil stream into a single oil stream; and
combining the first water stream and the second water stream into a
single water stream.
3. The method of claim 1, comprising using a swirl element within
the cyclonic separator to impart radial acceleration to the fluid
stream.
4. The method of claim 2, comprising controlling a radial
acceleration to avoid forming an emulsion.
5. The method of claim 4, comprising controlling the radial
acceleration using a plurality of swirl vanes arranged in parallel
or in series on the swirl element.
6. The method of claim 3, comprising generating the radial
acceleration within the fluid stream with a total pressure drop of
less than about 1 bar.
7. The method of claim 1, comprising using a vortex finder within
the cyclonic separator to remove the oil continuous stream.
8. The method of claim 1, comprising using an electrostatic
coalescer upstream of the cyclonic separator to create larger water
droplets.
9. The method of claim 1, comprising using an electrostatic
coalescer downstream of the cyclonic separator and upstream of the
first gravity separation vessel.
10. The method of claim 8, comprising automatically shutting off
the electrostatic coalescer if the fluid stream approaches a water
continuous phase.
11. The method of claim 1, comprising using an additional cyclonic
separator downstream of the first gravity separation vessel or the
second gravity separation vessel, or both, for further separation
of oil from water.
12. A system for separating oil and water streams, comprising: a
cyclonic separator configured to separate a fluid stream into an
oil continuous stream and a water continuous stream; a first
gravity separation vessel configured to separate the water
continuous stream into a first oil stream and a first water stream;
and a second gravity separation vessel configured to separate the
oil continuous stream into a second oil stream and a second water
stream.
13. The system of claim 12, comprising an electrostatic coalescer
upstream of the cyclonic separator.
14. The system of claim 12, comprising an electrostatic coalescer
on the oil continuous stream.
15. The system of claim 12, wherein a swirl element within the
cyclonic separator comprises a plurality of swirl vanes arranged
parallel or in series.
16. The system of claim 12, comprising an antiswirl device for
straightening a flow path of the water continuous stream or the oil
continuous stream, or both, downstream of the cyclonic
separator.
17. A method for separating two immiscible phases from a fluid
stream, comprising: sending the fluid stream into a cyclonic
separator; generating radial acceleration within the cyclonic
separator using a swirl element; controlling the radial
acceleration at a value at which the two immiscible phases separate
into two continuous phases; removing the two continuous phases from
the cyclonic separator into two lines using a vortex finder; and
sending the two continuous phases to two separate downstream
vessels for further separation of the two immiscible phases.
18. The method of claim 17, comprising controlling the radial
acceleration of the fluid stream by selecting an angular
orientation of at least one swirl vane on the swirl element.
19. The method of claim 17, comprising decreasing the tangential
velocity component of the fluid stream perpendicular to a flow path
using an antiswirl device downstream of a point at which the radial
acceleration was generated.
20. The method of claim 17, comprising controlling the swirling of
the fluid stream to maintain the radial acceleration at a value at
which shearing of the two immiscible phases does not cause an
emulsion to form.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority benefit of U.S.
Provisional Patent Application 61/537,317 filed Sep. 21, 2011
entitled SEPARATING OIL AND WATER STREAMS the entirety of which is
incorporated by reference herein.
FIELD
[0002] Exemplary embodiments of the subject innovation relate to
the separation of oil and water streams in a subsea or topside
environment.
BACKGROUND
[0003] Obtaining hydrocarbons from subsea environments is becoming
an increasingly important alternative to obtaining hydrocarbons
from land-based sources. As long as energy prices continue to
increase, this trend is likely to continue. Delivering hydrocarbons
from a subsea well to the surface presents technologists with a
number of challenges. Water in hydrocarbons can form hydrate
clathrates in transportation lines and subsea equipment as the
fluid cools, creating flow restrictions. Further, fluid obtained
from a subsea well may comprise a large proportion of water
relative to hydrocarbons, reducing the efficiency of hydrocarbon
transportation from the well. In such situations, it may be
desirable to attempt to separate hydrocarbons out of the liquid
produced by a subsea well at the sea floor.
[0004] Separating hydrocarbons flowing from a subsurface well from
other fluids may present difficulties. While subsea separation is
not trivial in shallow waters, for example, fifteen hundred meters
or less, it becomes much more challenging in deeper water. As water
depth increases, the external pressure on a vessel created by the
hydrostatic head increases the required wall thickness for vessels
used for subsea processing. At depths in excess of fifteen hundred
meters, this wall thickness becomes great enough, that typical
gravity separation is not practical because the allowable vessel
size is limited in diameter by wall thickness and weight. As a
result, deepwater subsea separation of hydrocarbons is relatively
difficult because traditional large-diameter separators cannot be
used. This disadvantage is further increased if the separation is a
heavy oil and water, which may emulsify.
[0005] Typically, separation of heavy oils from water necessitates
the use of a large gravity separation vessel that provides long
retention times for the oil and water to separate. However, due to
size and weight constraints, the use of large gravity separation
vessels is not practical for many applications, both on and
offshore. Topside applications of large gravity separation vessels
can be limited by the space requirements of the vessel. In some
instances, the ability to use a smaller, more efficient separation
system may be desirable.
[0006] Separation of oil and water is especially difficult when the
fluids are in an inversion range, for example, when the watercut of
the stream in the range between about 40% and about 60%. The
watercut is the ratio of water produced compared to the total
volume of liquid produced. In the fluid inversion range, emulsion
layers may form and inhibit effective separation of hydrocarbons
and water. An emulsion is a physical mixture of two liquids which
are immiscible, in which one liquid exists as nearly stable
droplets that are dispersed in the other liquid. An emulsion is
also known as a colloid. While overcoming this problem is difficult
topside, performance can be improved by heat, chemicals, or time.
However, in subsea applications, these techniques are often not
feasible.
[0007] The current practice to separate oil and water in the
inversion range is through separation enhancers. An example of a
separation enhancer includes mixing chemicals, such as
demulsifiers, with the fluid. However, as the fluid properties
change, such as by turning on new wells, the appropriate amount of
demulsifier to use becomes difficult to predict. This can lead to
using excess amounts of demulsifier, which is expensive and often
causes other challenges, such as foaming.
[0008] Another example of a separation enhancer is the application
of heat to lower the viscosity of the fluids and ease separation.
However, applying heat is expensive, and is very challenging in a
subsea environment.
[0009] Another example of a separation enhancer is the injection of
water into a separator to raise the watercut beyond the inversion
range. This is the most common currently-used method for subsea oil
and water separation. However, recirculation can require large
amounts of water, which necessitates an increase in the size of
equipment, such as vessels, pumps, and piping. Further, deepwater
vessels are limited in terms of available vessel volume due to the
external pressures. Therefore any waste of space due to added water
is a disadvantage.
[0010] Another separation enhancer involves the use of
electrostatic coalescers. Electrostatic coalescers place a charge
across a fluid or fluid mixture to cause droplets of polar fluids,
such as water, to coalesce into larger droplets. Although,
electrostatic coalescers are relatively effective, and are
currently used in many applications, they will turn off
automatically once the fluid mixture approaches a water continuous
phase to avoid shorting out. Therefore, since the separation will
still be difficult past the operation point of the electrostatic
coalescers, the use of electrostatic coalescers may not be relied
on as a total solution to the problem of separating oil and water
in the inversion range.
[0011] U.S. Pat. No. 6,197,095 to Ditria, et al., discloses a
method for subsea multiphase fluid separation. The initial step of
the method is the separation of solids using a cyclonic solids
separator. In a second step, bulk gas is removed from the liquid
using a cyclone or auger separator. In a third step, water is
separated from the oil using a liquid-liquid hydrocyclone. In a
final step, a gravity separator is used to cause further separation
of the water from the oil. However, the method is limited by the
size of the gravity separator, since a fairly large vessel may be
required to cause sufficient separation of the water from the oil
using one gravity separator.
[0012] International Patent Publication No. WO2004/007908 by
Gulbraar, et al., discloses an apparatus for separating water from
oil. The apparatus includes an electrostatic coalescer for the
separation of the water droplets from the oil droplets within a
stream. After the water has been partially separated from the oil
by the electrostatic coalescer, the stream is sent to an oil/water
separation arrangement for further separation of the water from the
oil. However, while the electrostatic coalescer may help to avoid
the formation of emulsions, the coalescer may not be sufficient to
ensure the avoidance of separation in the inversion range. In
addition, the use of only one oil/water separation arrangement may
increase the required size of the apparatus and limit the
effectiveness of the system.
SUMMARY
[0013] An embodiment provides a method for separating oil and water
streams. The method includes separating a fluid stream into an oil
continuous stream and a water continuous stream using a cyclonic
separator, flowing the oil continuous stream to a first gravity
separation vessel, and flowing the water continuous stream to a
second gravity separation vessel. The method also includes
separating the oil continuous stream in the first gravity
separation vessel into an oil stream and a water stream and
separating the water continuous stream in the second gravity
separation vessel into an oil stream and a water stream.
[0014] Another embodiment provides a system for separating oil and
water streams. The system includes a cyclonic separator configured
to separate a fluid stream into an oil continuous stream and a
water continuous stream, a first gravity separation vessel
configured to separate the water continuous stream into a first oil
stream and a first water stream, and a second gravity separation
vessel configured to separate the oil continuous stream into a
second oil stream and a second water stream.
[0015] Another embodiment provides a method for separating two
immiscible phases from a fluid stream. The method includes sending
the fluid stream into a cyclonic separator, generating radial
acceleration within the cyclonic separator using a swirl element,
and controlling the radial acceleration at a value at which the two
immiscible phases separate into two continuous phases. The method
also includes removing the two continuous phases from the cyclonic
separator into two lines using a vortex finder and sending the two
continuous phases to two separate downstream vessels for further
separation of the two immiscible phases.
DESCRIPTION OF THE DRAWINGS
[0016] The advantages of the present techniques are better
understood by referring to the following detailed description and
the attached drawings, in which:
[0017] FIG. 1 is an illustration of a subsea hydrocarbon field that
uses subsea separation techniques prior to sending materials to the
surface;
[0018] FIG. 2 is a schematic of a system for separating oil and
water using a cyclonic separator upstream of two gravity separation
vessels;
[0019] FIG. 3 is a schematic of a complete system for separating
gas, oil, water, and sand;
[0020] FIG. 4 is a schematic of a complete system, including an
electrostatic coalescer, for separating gas, oil, water, and
sand;
[0021] FIG. 5 is an illustrative view of a cyclonic separator that
may be used to separate oil and water streams;
[0022] FIG. 6 is an illustrative view of the swirl element that may
be used in the cyclonic separator; and
[0023] FIG. 7 is a process flow diagram showing a method for the
separation of oil and water streams.
DETAILED DESCRIPTION
[0024] In the following detailed description section, specific
embodiments of the present techniques are described. However, to
the extent that the following description is specific to a
particular embodiment or a particular use of the present
techniques, this is intended to be for exemplary purposes only and
simply provides a description of the exemplary embodiments.
Accordingly, the techniques are not limited to the specific
embodiments described below, but rather, include all alternatives,
modifications, and equivalents falling within the true spirit and
scope of the appended claims.
[0025] At the outset, for ease of reference, certain terms used in
this application and their meanings as used in this context are set
forth. To the extent a term used herein is not defined below, it
should be given the broadest definition persons in the pertinent
art have given that term as reflected in at least one printed
publication or issued patent. Further, the present techniques are
not limited by the usage of the terms shown below, as all
equivalents, synonyms, new developments, and terms or techniques
that serve the same or a similar purpose are considered to be
within the scope of the present claims.
[0026] A "facility" as used herein is a representation of a
tangible piece of physical equipment through which hydrocarbon
fluids are either produced from a reservoir or injected into a
reservoir. In its broadest sense, the term facility is applied to
any equipment that may be present along the flow path between a
reservoir and the destination for a hydrocarbon product. Facilities
may comprise drilling platforms, production platforms, production
wells, injection wells, well tubulars, wellhead equipment,
gathering lines, manifolds, pumps, compressors, separators, surface
flow lines, and delivery outlets. In some instances, the term
"surface facility" is used to distinguish those facilities other
than wells. A "facility network" is the complete collection of
facilities that are present in the model, which would include all
wells and the surface facilities between the wellheads and the
delivery outlets.
[0027] The term "gas" is used interchangeably with "vapor," and
means a substance or mixture of substances in the gaseous state as
distinguished from the liquid or solid state. Likewise, the term
"liquid" means a substance or mixture of substances in the liquid
state as distinguished from the gas or solid state. As used herein,
"fluid" is a generic term that may include either a gas or
vapor.
[0028] A "hydrocarbon" is an organic compound that primarily
includes the elements hydrogen and carbon although nitrogen,
sulfur, oxygen, metals, or any number of other elements may be
present in small amounts. As used herein, hydrocarbons generally
refer to organic materials that are transported by pipeline, such
as any form of natural gas or crude oil. A "hydrocarbon stream" is
a stream enriched in hydrocarbons by the removal of other
materials, such as water.
[0029] The terms "inversion range" or "fluid inversion range" refer
to a range between about 40%-60% watercut in a stream comprising
water and hydrocarbons. The inversion relates to a change of phase
in which the stream changes or "inverts" between a water continuous
stream and an oil continuous stream.
[0030] "Liquefied natural gas" or "LNG" is natural gas that has
been processed to remove impurities (for example, nitrogen, and
water and/or heavy hydrocarbons) and then condensed into a liquid
at almost atmospheric pressure by cooling and depressurization.
[0031] The term "natural gas" refers to a multi-component gas
obtained from a crude oil well (termed associated gas) or from a
subterranean gas-bearing formation (termed non-associated gas). The
composition and pressure of natural gas can vary significantly. A
typical natural gas stream contains methane (CH.sub.4) as a
significant component. Raw natural gas will also typically contain
ethylene (C.sub.2H.sub.4), ethane (C.sub.2H.sub.6), other
hydrocarbons, one or more acid gases (such as carbon dioxide,
hydrogen sulfide, carbonyl sulfide, carbon disulfide, and
mercaptans), and minor amounts of contaminants such as water,
nitrogen, iron sulfide, wax, and crude oil.
[0032] "Pressure" is the force exerted per unit area by the fluid
on the walls of the volume. Pressure can be shown as pounds per
square inch (psi). "Atmospheric pressure" refers to the local
pressure of the air. "Absolute pressure" (psia) refers to the sum
of the atmospheric pressure (14.7 psia at standard conditions) plus
the gage pressure (psig). "Gauge pressure" (psig) refers to the
pressure measured by a gauge, which indicates only the pressure
exceeding the local atmospheric pressure (i.e., a gauge pressure of
0 psig corresponds to an absolute pressure of 14.7 psia).
[0033] "Production fluid" refers to a liquid and/or gaseous stream
removed from a subsurface formation, such as an organic-rich rock
formation. Produced fluids may include both hydrocarbon fluids and
non-hydrocarbon fluids. For example, production fluids may include,
but are not limited to, oil, natural gas, and water.
[0034] "Substantial" when used in reference to a quantity or amount
of a material, or a specific characteristic thereof, refers to an
amount that is sufficient to provide an effect that the material or
characteristic was intended to provide. The exact degree of
deviation allowable may in some cases depend on the specific
context.
[0035] The term "watercut" refers to the proportion of water
present in a stream that comprises both water and other components
such as hydrocarbons. For example, a stream having a 20% watercut
comprises about 20% water and 80% other components.
[0036] "Well" or "wellbore" refers to a hole in the subsurface made
by drilling or insertion of a conduit into the subsurface. The
terms are interchangeable when referring to an opening in the
formation. A well may have a substantially circular cross section,
or other cross-sectional shapes (for example, circles, ovals,
squares, rectangles, triangles, slits, or other regular or
irregular shapes). Wells may be cased, cased and cemented, or
open-hole well, and may be any type, including, but not limited to
a producing well, an experimental well, and an exploratory well, or
the like. A well may be vertical, horizontal, or any angle between
vertical and horizontal (a deviated well), for example a vertical
well may comprise a non-vertical component.
[0037] "Clathrate hydrates" (hereinafter clathrate or hydrate) are
composites formed from a water matrix and a guest molecule, such as
methane or carbon dioxide, among others. Clathrates may form, for
example, at the high pressures and low temperatures that may be
found in pipelines and other hydrocarbon equipment. For any
particular clathrate composition involving water and guest
molecules, such as methane, ethane, propane, carbon dioxide, and
hydrogen sulfide, at a particular pressure there is a specific
clathrate equilibrium temperature, above which clathrates are not
stable and below which they are stable. After forming, the
clathrates can agglomerate, leading to plugging or fouling of the
equipment. Further, many hydrocarbons, such as crude oil, may
contain significant amounts of wax, e.g., in the form of paraffinic
compounds that may precipitate as temperatures are lowered. These
paraffinic compounds can form layers along cold surfaces, such as
the inner wall of a subsea pipeline, and can cause fouling or
plugging of equipment.
[0038] A "piston motor valve" (PMV) is a type of valve that uses
the linear motion of a piston to open or close the valve. A PMV is
used when a fully open or fully closed valve is desirable for flow
control.
[0039] A "diaphragm motor valve" (DMV) is a type of device or
component that may be used to control the flow of a fluid through a
pipe or tube by moving a valve though a range of positions from
fully closed to fully open. A DMV is generally used to throttle
fluid flow in a line.
Overview
[0040] Current separation systems, including both subsea and
topside separation systems, encounter difficulty in the separation
of oil and water once the fluid mixture approaches the inversion
range. The inversion range of an oil and water fluid mixture is
typically around 40% to 60% watercut. Below the lower watercut
limit, the mixture is usually oil continuous; and the water
droplets are dispersed into the oil. Above the upper watercut
limit, the mixture is usually water continuous and the oil is the
dispersed phase. However, emulsions can be formed in the
intermediate range of watercuts where the two phases are switching
from continuous to dispersed phase. The formation of stable
emulsions makes separation of oil and water in the inversion range
very challenging.
[0041] Embodiments disclosed herein provide methods and systems
that allow for the separation of gas, oil, water, and sand
throughout all watercuts, including those in the inversion range.
The method lowers the likelihood of separating mixtures in the
inversion range through the utilization of a cyclonic separator
upstream of two gravity separation vessels. Accordingly, the system
may function effectively without the use of separation enhancers
for gravity separation in the fluid inversion range, since gravity
separation techniques are not applied while the fluid is in the
inversion range.
[0042] The cyclonic separator is placed upstream of the two gravity
separation vessels to provide an initial separation of the fluid
into a water continuous stream and an oil continuous stream. A
fixed swirl element inside the cyclonic separator creates a radial
acceleration in the fluid, e.g., by generating a cyclone action.
The fixed swirl element is designed to have a low pressure drop to
lower turbulence and fluid mixing. The cyclonic action generates a
centripetal force that causes the heavier fluid phase, water, to
move towards the outside wall of the pipe and the lighter fluid
phase, oil, to move towards the center. In this manner, the swirl
element performs a bulk phase separation of the fluids.
[0043] The streams may be split by means of a vortex finder in the
center of the cyclonic separator or by a horizontal flow split with
a baffle running parallel to the cyclonic separator. Some amount of
the other component will remain in each stream. The two different
streams may be sent to separate gravity separation vessels, e.g.,
pipe separators, for further separation of oil and water phases.
Thus, separation of fluids in a gravity separation vessel is not
attempted while the mixture is in the inversion range.
[0044] After the two different streams enter into the separate
gravity separation vessels, further separation is performed, and
each vessel has an oil outlet and a water outlet. The oil streams
from the gravity separation vessels may remain separate or may be
blended together. The same is true for the water streams from the
gravity separation vessels. The particular application or system
configuration may be used to determine whether the fluid streams
from multiple gravity separation vessels should be combined or
remain separated. Further, a number of the separation systems may
be utilized in one area, with the like streams combined into single
streams.
[0045] In an embodiment, the present techniques may be used in any
transportation or production environment that is susceptible to
clathrate, including subsea to shore pipelines, on-shore pipelines,
wells, oil from oil sands, natural gas, or any number of liquid or
gaseous hydrocarbons from any number of sources. For example, a
specific application of the present techniques may include the
protection of subsea lines from a production field.
[0046] The system described herein may be used on the seafloor to
separate oil and water mixtures that are in or near the inversion
range by avoiding gravity separation while fluids are in the
inversion range. This system does not depend on the use of
separation enhancers, which can be costly and may limit the
capacity of the system.
[0047] FIG. 1 is an illustration of a subsea hydrocarbon field 100
that uses a cyclonic separation technique. The field 100 can have a
number of wellheads 102 coupled to wells 104 that harvest
hydrocarbons from a formation (not shown). As shown in this
example, the wellheads 102 may be located on the ocean floor 106.
Each of the wells 104 may include single wellbores or multiple,
branched wellbores. Each of the wellheads 102 can be coupled to a
central pipeline 108 by gathering lines 110. The central pipeline
108 may continue through the field 100, coupling to further
wellheads 102, as indicated by reference number 112.
[0048] In an embodiment, a cyclonic separation system 114 is used
for the separation of gas, oil, water, and sand from the central
pipeline 108. Three lines 116, 118, and 120 may couple the cyclonic
separation system 114 to a platform 122 at the ocean surface 124.
The three lines 116, 118, and 120 may be flexible to allow movement
of the platform 122. The flexible lines 116, 118, and 120 may carry
gas, oil, and water, respectively, to the platform 122. The
platform 122 may be, for example, a floating processing station,
such as a floating storage and offloading unit (or FSO), that is
anchored to the sea floor 106 by a number of tethers 126.
[0049] Any number of other types of platforms or rigs may be used.
For example, the platform 122 may be a production platform with
equipment for dehydration, purification, oil and water separation,
oil and gas separation, and the like, such as a storage vessel or
separation vessel 128. The platform 122 may be a drilling platform
that includes drilling equipment, such as a tower or derrick 130.
The platform 122 may transport the processed hydrocarbons to shore
facilities by pipeline (not shown). The separation of the
hydrocarbons in a cyclonic separation system 114 may prevent the
formation of hydrate plugs in transportation lines to the surface,
as the oil lines 118, and gas lines 118, are separate from the
water lines 120. Further, the separation at the sea floor, or at a
well site in a surface field, may provide water for reinjection
into the formation to enhance production.
Cyclonic Separation Apparatus
[0050] FIG. 2 is a schematic of a system 200 for separating oil and
water using a cyclonic separator 202 upstream of two gravity
separation vessels 204 and 206. The cyclonic separator 202 is
discussed further with respect to FIG. 5. The cyclonic separator
202 produces an oil continuous stream 208 and a water continuous
stream 210. The concentration of oil and water, respectively, in
each of the two streams may remain above 60%. Therefore, the two
streams may remain outside of the inversion range and be easier to
separate.
[0051] In an embodiment, the flow of liquid out of the cyclonic
separator 202 may be controlled by a level control or a back
pressure control, or any combination thereof, located on the
cyclonic separator 202. The level control or back pressure control
may allow for the extraction of the appropriate amount of liquid
from the cyclonic separator 202 according to the application or the
operation of the gravity separation vessels 204 and 206 downstream
of the cyclonic separator 202. In another embodiment, any other
type of controls may be used in conjunction with the system 200 to
regulate the flow of liquid from one component of the system 200 to
another.
[0052] The oil continuous stream 208 flows into a first gravity
separation vessel 204, and the water continuous stream 210 flows
into a second gravity separation vessel 206. The cyclonic separator
202 separates mixtures of oil and water that may be in the
inversion range prior to the gravity separation by the gravity
separation vessels 204 and 206.
[0053] Once the oil continuous stream 208 has entered the gravity
separation vessel 204, the oil and the water within the fluid may
be separated using conventional gravity separation techniques. The
less dense oil may float to the top and exit as oil stream 212,
while the denser water may sink to the bottom and exit as water
stream 214. The same process may occur once the water continuous
stream 210 has entered the gravity separation vessel 206. The oil
may exit as oil stream 216 at the top of the gravity separation
vessel 206, and the water may exit as water stream 218 at the
bottom of the vessel. The pressure, fluid level, and temperature
within the gravity separation vessels 204 and 206 may be monitored
using sensors 220, 222, and 224, respectively.
[0054] The oil streams 212 and 216 containing the oil continuous
phase may be joined into one oil stream 226, while the water
streams 214 and 218 containing the water continuous phase may be
joined into one water stream 228. Diaphragm motor valves (DMV) 230
may be used as control valves to adjust the amount of flow of
streams 226 and 228. For example, the DMVs 230 may be partially
opened or partially closed to adjust the velocity and pressure of
the streams 226 and 228. In addition, the oil-in-water
concentration of the stream 228 may be monitored by an OIW sensor
232. The amount of oil in the water continuous phase at any point
in time may be used to determine the appropriate action to take
with respect to the fluid. For example, if a large amount of oil is
left in the water continuous phase, the fluid may be passed through
another cyclonic separator, or de-oiler, to salvage as much oil as
possible.
[0055] The system 200 may also include additional control features.
For example, a fluid level sensor 222 may determine the fluid level
in the pipes and send the information regarding the fluid level to
a computing device. The computing device may include a programmable
logic controller (PLC), distributed control system (DCS), or a
direct digital controller (DDC), among others. The computing device
may use the fluid level information to control the DMV 226, as
indicated by the dotted line 234. The DMV 226 may act as an
effector by adjusting the position of the valve to allow for
increased or decreased fluid flow. In another embodiment, the DMV
226 may be a smart valve, which may act as both the computing
device and the effector. In addition, it should be noted that
multiple DMVs or other effectors, for example, pumps or PMVs, may
be connected to one computing device and controlled based on
changes to multiple different sensors.
[0056] In an embodiment, any number of additional gravity
separation vessels may be used in conjunction with the system 200.
For example, the gravity separation vessels 204 and 206 may be
configured to operate in parallel with two additional gravity
separation vessels to allow for a higher degree of separation of
the oil from the water. As another example, two additional gravity
separation vessels may be configured to operate in series with and
downstream of the gravity separation vessels 204 and 206.
[0057] In another embodiment, additional cyclonic separators may be
used downstream of the first cyclonic separator 202. The additional
cyclonic separators may be placed upstream or downstream of the
gravity separation vessels 204 and 206, or may replace the gravity
separation vessels 204 and 206. In yet another embodiment, the
cyclonic separator 202 may be replaced with a bundle of multiple
cyclonic separators arranged in series or parallel. The use of
multiple cyclonic separators may allow for a more efficient
separation process.
[0058] FIG. 3 is a schematic of a complete system 300 for
separating gas, oil, water, and sand. In FIG. 3, like numbered
items are as discussed with respect to FIGS. 1 and 2. Liquid may
flow into the system through an initial control valve 302 from the
central pipeline 108. A series of sensors 304, 306, 308, and 310
may be used to measure the fluid pressure, temperature, multiphase
flow rate, and sand content, respectively, as the fluid flows
through the initial control valve 302 and into the gas liquid
separator 312. The gas liquid separator 312 may be used for bulk
separation of the gas phase from the liquid phase. The pressure,
temperature, and fluid levels within the gas liquid separator may
be monitored using sensors 314, 316, and 318, respectively. Once
the gas phase and the liquid phase have been separated by the gas
liquid separator 312, the gas may flow out as gas stream 320, and
the liquid may flow out as liquid stream 322.
[0059] A DMV 323 may be controlled by the feedback from the sensors
314, 316, and 318. The feedback may be used to determine whether
the DMV 323 should be opened, closed, or partially opened or
closed, as indicated by the dotted line 324. The flow of the gas
stream 320 may also be monitored using a sensor 326. When the DMV
323 is open, the gas stream 320 may flow into the gas polisher 328.
The gas polisher 328 may be used to purify the natural gas. The
differential pressure within the gas polisher 328 may be monitored
using a differential pressure sensor 330. The value measured by the
differential pressure sensor 330 may be used to control the
position of the DMV 332, which controls the flow of an outlet gas
stream 334, as indicated by the dotted line 336. When the DMV 332
is open, the gas stream 334 from the gas polisher 328 may be sent
to the collection platform 122 (not shown), as discussed with
respect to FIG. 1. In addition, the flow of the gas stream 334 may
be controlled by an orifice plate 335. The orifice plate 335 may be
used to control the pressure of gas stream 334 in order to reduce
the possibility of backflow of the gas stream 334 into any
downstream lines. It should be noted that any number of additional
orifice plates 335 may be located within the system 300 and may be
used to control the pressure of various streams within the system
300.
[0060] A level sensor 338 may also be used to measure the fluid
level within the gas polisher 328 and may be used to control a DMV
340, as indicated by the dotted line 342. When the DMV 340 is open,
the liquid that has been separated from the natural gas by the gas
polisher 328 may flow into the system 200 as liquid stream 344. The
liquid stream 344 may be coupled to liquid stream 346 as it enters
system 200.
[0061] The flow rate of the liquid stream 322 from the gas liquid
separator 312 may be monitored by a sensor 348. The liquid stream
322 may flow into a desander 350, for example, to cyclonically
separate the sand from the liquid stream 322. A DMV 352 may be used
to control the outflow of sand from the desander 350 as stream 354.
The DMV 352 may be controlled by feedback from a differential
pressure sensor 356, which measures the differential pressure
between streams 322, 346, and 354. When the DMV 352 is open, stream
354 may flow into a sand accumulator 358.
[0062] From the sand accumulator 358, the sand may take several
routes. The sand may be released as stream 360 through a PMV 362.
The sand may be ejected as stream 360 into the outflowing water
stream. The PMV 362 may be either entirely open or entirely closed,
depending on the specification of the operator or specific
parameters of system 300. The sand content and pressure within the
sand accumulator 358 may be monitored using sensors 364 and 366,
respectively. The values measured by the sensors 364 and 366 may be
used to control the position of PMV 362.
[0063] In addition, the DMV 367 may be used to control the flow of
sand out of the sand accumulator 358. In an embodiment, the DMV 367
may remain closed as the sand accumulator 358 becomes pressurized
as it fills with sand. Once the sand accumulator 358 has reached a
certain pressure level, the DMV 367 may open to allow the sand
accumulator 358 to be emptied.
[0064] For a safety measure, a stream 368 may be allowed to flow
out of the top of the sand accumulator 358 if the sand accumulation
level becomes too high. The primary purpose of stream 368 is to
prevent the failure of system 300 through the clogging of the sand
accumulator 358 in the case of the failure of PMV 362. In addition,
any remaining liquid in the sand accumulator 358 may be released as
stream 370 through a PMV 372. In an embodiment, stream 370 may
include the liquid (mostly water) from which the sand has settled
and may be released from the top of the sand accumulator 358.
Stream 370 may allow for the maintenance of mass balance within the
sand accumulator 358 as stream 354 flows into the accumulator
358.
[0065] The liquid stream 346 from desander 350 may flow out as to
be input into the separation cyclone 202. A DMV 374 may regulate
the flow of liquid stream 346 into the system 200. The DMV 374 may
be controlled using feedback from the level sensor 318, which
determines the fluid level within the gas liquid separator 312, as
indicated by the dotted line 376.
[0066] The cyclone 202 may receive incoming liquid streams 344 and
346. The system 200 may be used to separate the oil from the water,
as discussed with respect to FIG. 2. The cyclonic separator 202 may
be used to create two fluid streams. The cyclonic separator 202 may
send an oil continuous stream 208 to the gravity separation vessel
204 and a water continuous stream 210 to the gravity separation
vessel 206. The oil from the gravity separation vessels 204 and 206
may be collected into oil streams 212 and 216, while the water may
be collected into water streams 214 and 218, respectively.
[0067] As discussed with respect to FIG. 2, the pressure, fluid
level, and temperature within the gravity separation vessels 204
and 206 may be monitored using sensors 220, 222, and 224,
respectively. The fluid level information may be used to control
the position of the DMV 230, as indicated by the dotted line 234.
In addition, the information from the sensors 220, 222, and 224 may
be used to control the positions of various other control valves,
including DMV 376 and DMV 378, as indicated by dotted lines 380 and
382, respectively. The DMV 376 may control the flow of stream 384
into the gravity separation vessel 204. The DMV 378 may control the
flow of a gas stream 386 from the gravity separation vessel 204 to
the gas outlet stream 334. An additional stream 388 may also be
directed to the gravity separation vessel 204 from stream 368. The
flow of stream 388 may be controlled by the DMV 390. The stream 388
may include any fluid that was remaining the in the stream 368.
[0068] Once the oil streams 212 and 216 are combined into one oil
stream 226, the DMV 230 may control the flow of the oil stream 226.
When the DMV 230 is open, the oil stream 226 may flow to an oil
pump 392. After the oil has passed through the oil pump 392, it may
be flow as stream 394 to the platform 122 (not shown), as discussed
with respect to FIG. 1.
[0069] Once the water streams 214 and 218 are combined into one
water stream 228, the DMV 230 may control the flow of the water
stream 228. When the DMV 230 is open, the water stream 228 may flow
into a bulk de-oiler 396. The bulk-de-oiler 396 may be a type of
cyclonic separator that is used to separate oil droplets from water
droplets. Any remaining oil in the water stream 228 may be
separated from the water by the bulk de-oiler 396 and sent as oil
stream 398 to be combined with the main oil stream 226 upstream of
the oil pump 392. The flow of oil stream 398 may be controlled by
the DMV 400. Once the water has been separated from the oil in the
bulk de-oiler 396, the water stream 402 may be sent to a second
de-oiler 404. In addition, the differential pressure between oil
stream 398 and water stream 402 may be measured by the differential
pressure sensor 406. The differential pressure value measured by
the sensor 406 may be used as feedback to control the DMV 400, as
indicated by the dotted line 408. The DMV 400 may be used to
control the flow of oil stream 398.
[0070] The second de-oiler 404 may be used to ensure an even higher
degree of oil and water separation by repeating the separation
process one more time. The oil which is separated from the water
within the second de-oiler 404 may be sent as oil stream 410 to be
combined with oil stream 398. A differential pressure sensor 412
may measure the differential pressure between oil streams 402 and
410 and value of the measurement may be used to control the
position DMV 414, as indicated by dotted line 416. The DMV 414 may
control the flow of oil stream 410. Once the remaining oil has been
separated from the water by the second de-oiler 404, the water
stream 418 may be sent to a water injection pump 420. The sensor
422 may be used to measure the final oil-in-water concentration of
water stream 418. In addition, water stream 370 from the sand
accumulator 358 may flow into water stream 418. In an embodiment,
if the oil-in-water concentration is considered to be low enough,
the water injection pump 420 may be omitted, and the water stream
418 may be released into the ocean. In some circumstances,
additional purification of the water may also take place before
releasing the water stream 418 into the ocean. In another
embodiment, the water stream 424 exiting the injection pump 420 may
be sent to the platform 122, as discussed with respect to FIG. 1.
The sand streams 360 and 368 may also flow into stream 424 to be
injected, released into the ocean, or sent to the platform 122 (not
shown).
[0071] It should be noted that the system 300 is not limited to the
configuration shown but, instead, may be arranged in any number of
different ways using any number of different components. For
example, additional DMVs, PMVs, and sensors may be added to the
system 300 to improve the functioning of the system 300. As another
example, more de-oilers may be added to the system in addition to
the de-oilers 396 and 404.
[0072] FIG. 3 illustrates a four-phase separation system that may
achieve the separation of gas, oil, water, and sand on the sea
floor. The majority of the components of system 300 may be designed
based on pipe code such that the required wall thicknesses are
greatly reduced while still being useful in deepwater operations.
In addition, the use of system 300 as a subsea separation system
may allow for the separation of oil and water in the inversion
range without the use of separation enhancers, which are costly and
may limit capacity.
[0073] FIG. 4 is a schematic of a complete system 426, including an
electrostatic coalescer 428, for separating gas, oil, water, and
sand. The system 426 is the same as system 300, except for the
addition of the electrostatic coalescer 428 upstream of the
cyclonic separator 202. Thus, in FIG. 4, like numbers are as
discussed with respect to the previous figures. An "electrostatic
coalescer" is a device that may be used to separate an emulsion
into its components, e.g., water and oil, in this case, by
subjecting the emulsion to a high-voltage electrical field. The
electrical field causes the water droplets in the emulsion, which
are conductive, to separate from the oil droplets, which are
non-conductive, by combining. The separation of the water from the
oil in the fluid may help to avoid the inversion range.
[0074] As shown in FIG. 4, the electrostatic coalescer 428 may be
positioned immediately upstream of the cyclonic separator 202. The
location of the electrostatic coalescer upstream of the cyclonic
separator 202 may enhance the coalescence and separation of the
dispersed phase, e.g., water, in the fluid. While the radial
acceleration of the swirl element within the cyclonic separator 202
may be sufficient for separating the water and oil phases, the use
of the electrostatic coalescer 428 may be beneficial, particularly
in the case of emulsion formation or the presence of high-viscosity
oil within the fluid.
[0075] In another embodiment, the electrostatic coalescer 428 may
be positioned downstream of the cyclonic separator 202 and upstream
of the gravity separation vessel 204. In this case, the
electrostatic coalescer 428 may be used for the same purpose as in
the previous embodiment. However, it should be noted that an
electrostatic coalescer 428 will turn off automatically if the
fluid mixture approaches water continuity in order to avoid a short
out and to conform to safety standards. Therefore, an electrostatic
coalescer may not be positioned upstream of gravity separation
vessel 206, since the water continuous stream 210 flows into
gravity separation vessel 206.
Cyclonic Separator
[0076] FIG. 5 is an illustrative view of a cyclonic separator 500
that may be used to separate oil and water streams. In FIG. 5, like
numbers are as discussed with respect to the previous figures. The
stream may enter the vessel 502 of the cyclonic separator 500 as
stream 346, as discussed with respect to FIGS. 2 and 3. As the
fluid enters the vessel 502, a swirl element 504 within the vessel
502 may impart a radial acceleration and a tangential velocity
component to the fluid through the rotation of twisted swirl vanes.
The swirl vanes may be arranged parallel or in series on the swirl
element 504. The swirling of the fluid using the swirl element may
be controlled to maintain the radial acceleration at a value at
which the two phases separate into two continuous phases, while
minimizing the turbulence to avoid shearing of the fluid. If
shearing occurs within the fluid, an emulsion of oil and water may
form. Once an emulsion has formed, it becomes even more challenging
and costly to separate the oil and water. Therefore, in order for
the cyclonic separator 202 to be effective, the centrifugal force
that is generated should be enough to effect bulk separation of the
oil and water, but not enough to cause significant shearing effects
within the fluid. To minimize the shearing, the radial acceleration
of the fluid may be maintained at a value which does not cause a
total pressure drop exceeding 1 bar in the fluid.
[0077] The radial acceleration imparted to the fluid may cause the
fluid to begin swirling through the vessel 502 due to the generated
centrifugal force. The heavier and denser water droplets may
migrate to the outer rim of the vessel 502 and begin traveling in a
wide circular path, while the lighter and less dense oil droplets
may migrate towards the center of the vessel 502 and begin
traveling in a narrow circular path. As the fluid continues to move
through the vessel 502, the fluid may be separated into two phases,
an oil continuous phase, and a water continuous phase. As the fluid
nears the end of the vessel 502, a vortex finder 506 may be used to
capture the oil continuous phase and send it out as oil stream 208,
while an outlet 508 may be used to capture the water continuous
phase and send it out as water stream 210.
[0078] An antiswirl device (not shown) may be positioned downstream
of the cyclonic separator 500. The antiswirl device may be used to
reduce the tangential velocity component of the oil stream 208 or
the water stream 210 perpendicular to the flow path. The antiswirl
device may help to align the flow path of a stream before the fluid
enters a gravity separation vessel, lessening the likelihood the
tangential velocity may cause mixing in the gravity separation
vessel.
[0079] FIG. 6 is an illustrative view 600 of a swirl element 504
that may be used in the cyclonic separator 500. In FIG. 6, like
numbers are as discussed with respect to the previous figures. The
swirl element 504 may be affixed inside the cyclonic separator pipe
502, near the inlet of stream 346. The swirl element may include
several twisted swirl vanes 602 that are used to swirl the stream
346 within the cyclonic separator pipe 502. The swirl vanes 602 may
be arranged parallel or in series on the swirl element 504 and may
be positioned at a particular angular orientation in order to
effectively control the swirling of the fluid. The radial
acceleration may be maintained at a value which causes the
separation of the two phases while preventing the generation of
shearing forces within the fluid. If shearing of the fluid occurs,
an emulsion may form. Emulsion generation may make it more
difficult to separate two phases, due to the strong interaction
forces between the individual particles of the two phases.
[0080] As the fluid flow rotates downstream of the swirl element
602, the oil continuous phase, indicated by the dark area in FIG.
6, moves to the core of the cyclonic separator pipe 502, while the
water continuous phase, indicated by the light area in FIG. 6,
moves toward the outer wall of the pipe 502. The swirl element 504
creates a gentle rotation within the fluid, thereby utilizing the
centrifugal force of the rotation to move the heavier, denser water
droplets within the fluid toward the outer wall. The ultimate
effect is to increase the number of water droplet interactions and
oil droplet interactions and, thus, coalescing the droplets in the
stream and removing the water phase from the oil phase.
Method for Separation
[0081] FIG. 7 is a process flow diagram showing a method 700 for
the separation of oil and water streams. The method 700 may be
useful for the harvesting of hydrocarbons from an oil well in both
subsea and topside environments. In addition, method 700 may
separate oil and water streams efficiently by avoiding the gravity
separation of the two phases in the inversion range.
[0082] At block 702, the stream may be separated into an oil
continuous stream and a water continuous stream using a cyclonic
separator. The cyclonic separator may use a number of swirl vanes
arranged parallel or in series to generate radial acceleration
within the stream, as discussed with respect to FIGS. 5 and 6. The
radial acceleration within the cyclonic device may also be
controlled to ensure effective separation of the oil continuous
phase and the water continuous phase.
[0083] At block 704, the oil continuous stream may be allowed to
flow into a first gravity separation vessel. The oil continuous
stream may be directed from the cyclonic separator to the first
gravity separation vessel using a vortex finder extended through
the center of the cyclonic separator pipe. An antiswirl device may
be used to straighten the flow of the oil continuous stream
upstream of the first gravity separation vessel.
[0084] At block 706, the water continuous stream may be allowed to
flow into a second gravity separation vessel. The water continuous
stream may be directed from the cyclonic separator to the second
gravity separation vessel through an outlet on the bottom of the
cyclonic separator pipe. The outlet may capture the water
continuous stream as it flows in a wide circular path around the
rim of the cyclonic separator pipe. An antiswirl device may be used
to straighten the flow of the water continuous stream upstream of
the second gravity separation vessel.
[0085] At block 708, the oil may be separated from the water in the
first gravity separation vessel using gravity separation
techniques. Because water is heavy and denser than oil, the water
will settle at the bottom of the vessel, while the oil will float
to the top. At block 710, the oil may be separated from the water
in the second gravity separation vessel using the same gravity
separation techniques as those discussed with respect to block
708.
[0086] It should be noted that the process flow diagram is not
intended to indicate that the steps of method 700 must be executed
in any particular order or that every step must be included for
every case. Further, additional steps may be included which are not
shown in FIG. 7. For example, the two oil streams may be combined
into a single oil stream, and the two water streams may be combined
into a single water stream downstream of the first and second
gravity separation vessels.
[0087] While the present techniques may be susceptible to various
modifications and alternative forms, the exemplary embodiments
discussed above have been shown only by way of example. However, it
should again be understood that the technique is not intended to be
limited to the particular embodiments disclosed herein. Indeed, the
present techniques include all alternatives, modifications, and
equivalents falling within the true spirit and scope of the
appended claims.
Embodiments
[0088] Embodiments of the invention may include any of the
following methods and systems, among others, as discussed herein.
This is not to be considered a complete listing of all possible
embodiments, as any number of variations can be envisioned from the
description above.
[0089] An exemplary embodiment provides a method for separating oil
and water streams. The method includes separating a fluid stream
into an oil continuous stream and a water continuous stream using a
cyclonic separator, flowing the oil continuous stream to a first
gravity separation vessel, and flowing the water continuous stream
to a second gravity separation vessel. The method also includes
separating the oil continuous stream in the first gravity
separation vessel into an oil stream and a water stream and
separating the water continuous stream in the second gravity
separation vessel into an oil stream and a water stream.
[0090] In some embodiments, the method may include combining the
oil streams into a single oil stream and combining the water
streams into a single water stream.
[0091] In some embodiments, the method may include using a swirl
element within the cyclonic separator to impart radial acceleration
to the fluid stream.
[0092] In some embodiments, the method may include controlling a
radial acceleration to avoid forming an emulsion.
[0093] In some embodiments, the method may include controlling the
radial acceleration using a plurality of swirl vanes arranged in
parallel or in series on the swirl element.
[0094] In some embodiments, the method may include generating the
radial acceleration within the fluid stream with a total pressure
drop of less than about 1 bar.
[0095] In some embodiments, the method may include using a vortex
finder within the cyclonic separator to remove the oil continuous
stream.
[0096] In some embodiments, the method may include using an
electrostatic coalescer upstream of the cyclonic separator to
create larger water droplets.
[0097] In some embodiments, the method may include using an
electrostatic coalescer downstream of the cyclonic separator and
upstream of the first gravity separation vessel.
[0098] In some embodiments, the method may include automatically
shutting off the electrostatic coalescer if the fluid stream
approaches a water continuous phase.
[0099] In some embodiments, the method may include using an
additional cyclonic separator downstream of the first gravity
separation vessel or the second gravity separation vessel, or both,
for further separation of oil from water.
[0100] Another exemplary embodiment provides a system for
separating oil and water streams. The system includes a cyclonic
separator configured to separate a fluid stream into an oil
continuous stream and a water continuous stream, a first gravity
separation vessel configured to separate the water continuous
stream into a first oil stream and a first water stream, and a
second gravity separation vessel configured to separate the oil
continuous stream into a second oil stream and a second water
stream.
[0101] In some embodiments, the system includes an electrostatic
coalescer upstream of the cyclonic separator.
[0102] In some embodiments, the system includes an electrostatic
coalescer on the oil continuous stream.
[0103] In some embodiments, the system includes a swirl element
within the cyclonic separator comprises a plurality of swirl vanes
arranged parallel or in series.
[0104] In some embodiments, the system includes an antiswirl device
for straightening a flow path of the water continuous stream or the
oil continuous stream, or both, downstream of the cyclonic
separator.
[0105] Another exemplary embodiment provides a method for
separating two immiscible phases from a fluid stream. The method
includes sending the fluid stream into a cyclonic separator,
generating radial acceleration within the cyclonic separator using
a swirl element, and controlling the radial acceleration at a value
at which the two immiscible phases separate into two continuous
phases. The method also includes removing the two continuous phases
from the cyclonic separator into two lines using a vortex finder
and sending the two continuous phases to two separate downstream
vessels for further separation of the two immiscible phases.
[0106] In some embodiments, the method includes controlling the
radial acceleration of the fluid stream by selecting an angular
orientation of at least one swirl vane on the swirl element.
[0107] In some embodiments, the method includes decreasing the
tangential velocity component of the fluid stream perpendicular to
a flow path using an antiswirl device downstream of a point at
which the radial acceleration was generated.
[0108] In some embodiments, the method includes controlling the
swirling of the fluid stream to maintain the radial acceleration at
a value at which shearing of the two immiscible phases does not
cause an emulsion to form.
* * * * *