U.S. patent application number 12/142544 was filed with the patent office on 2009-01-01 for system and process for inhibitor injection.
This patent application is currently assigned to H R D CORPORATION. Invention is credited to Rayford G. ANTHONY, Ebrahim BAGHERZADEH, Gregory BORSINGER, Abbas HASSAN, Aziz HASSAN.
Application Number | 20090001188 12/142544 |
Document ID | / |
Family ID | 40159188 |
Filed Date | 2009-01-01 |
United States Patent
Application |
20090001188 |
Kind Code |
A1 |
HASSAN; Abbas ; et
al. |
January 1, 2009 |
SYSTEM AND PROCESS FOR INHIBITOR INJECTION
Abstract
A method for introducing inhibitor into a fluid to be treated by
forming a dispersion comprising droplets, particles, or gas bubbles
of the inhibitor dispersed in a continuous phase of a carrier,
wherein the droplets, particles, or gas bubbles have a mean
diameter of less than 5 .mu.m, and wherein either the carrier is
the fluid to be treated or the method further comprises introducing
the dispersion into the fluid to be treated. A system for
inhibiting an undesirable component, the system comprising at least
one high shear mixing device comprising at least one generator
comprising a rotor and a stator separated by a shear gap, wherein
the high shear mixing device is capable of producing a tip speed of
the rotor of greater than 22.9 m/s, and a pump for delivering a
mixture of a carrier and an inhibitor to the high shear mixing
device.
Inventors: |
HASSAN; Abbas; (Sugar Land,
TX) ; BAGHERZADEH; Ebrahim; (Sugar Land, TX) ;
ANTHONY; Rayford G.; (College Station, TX) ;
BORSINGER; Gregory; (Chatham, NJ) ; HASSAN; Aziz;
(Sugar Land, TX) |
Correspondence
Address: |
CONLEY ROSE, P.C.;David A. Rose
P. O. BOX 3267
HOUSTON
TX
77253-3267
US
|
Assignee: |
H R D CORPORATION
Houston
TX
|
Family ID: |
40159188 |
Appl. No.: |
12/142544 |
Filed: |
June 19, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60946463 |
Jun 27, 2007 |
|
|
|
Current U.S.
Class: |
239/10 ; 239/398;
366/282; 366/293; 366/305 |
Current CPC
Class: |
Y10S 516/929 20130101;
E21B 41/02 20130101; B01F 7/00766 20130101; B01F 13/1027 20130101;
C09K 8/54 20130101; Y10S 516/923 20130101; B01F 2215/0481
20130101 |
Class at
Publication: |
239/10 ; 239/398;
366/282; 366/293; 366/305 |
International
Class: |
B01F 3/00 20060101
B01F003/00; B01F 7/26 20060101 B01F007/26; B01F 15/02 20060101
B01F015/02; B05B 17/00 20060101 B05B017/00; B01F 3/08 20060101
B01F003/08 |
Claims
1. A method for introducing inhibitor into a fluid to be treated,
the method comprising: forming a dispersion comprising droplets,
particles, or gas bubbles of the inhibitor dispersed in a
continuous phase of a carrier, wherein the droplets, particles, or
gas bubbles have a mean diameter of less than 5 .mu.m, and wherein
either the carrier is the fluid to be treated or the method further
comprises introducing the dispersion into the fluid to be
treated.
2. The method of claim 1 wherein the inhibitor is selected from
corrosion inhibitors, transport-enhancing inhibitors, scale
inhibitors, hydrate inhibitors, ice-formation inhibitors, and
combinations thereof.
3. The method of claim 1 wherein the dispersion is formed from a
liquid or solid inhibitor.
4. The method of claim 1 wherein the dispersion is formed from a
gaseous inhibitor.
5. The method of claim 1 wherein the droplets or gas bubbles have a
mean diameter of less than 1 .mu.m.
6. The method of claim 5 wherein the droplets or gas bubbles have a
mean diameter of no more than 400 nm.
7. The method of claim 1 wherein the fluid to be treated comprises
boiler feedwater or a transport stream comprising hydrocarbons.
8. The method of claim 1 wherein the carrier comprises at least a
portion of the fluid to be treated.
9. The method of claim 1 wherein forming the dispersion comprises
subjecting a mixture of the inhibitor and the carrier to a shear
rate of greater than about 20,000 s.sup.-1.
10. The method of claim 1 wherein forming the dispersion comprises
contacting the inhibitor and the carrier in a high shear device,
wherein the high shear device comprises at least one rotor, and
wherein the at least one rotor is rotated at a tip speed of at
least 22.9 m/s (4,500 ft/min) during formation of the
dispersion.
11. The method of claim 10 wherein the high shear device produces a
local pressure of at least about 1034.2 MPa (150,000 psi) at the
tip of the at least one rotor.
12. The method of claim 10 wherein the energy expenditure of the
high shear device is greater than 1000 watts per cubic meter of
fluid therein during dispersion formation.
13. A method for introducing inhibitor into a fluid to be treated,
the method comprising: subjecting a fluid mixture comprising
inhibitor and a carrier to a shear rate greater than 20,000
s.sup.-1 in a high shear device to produce a dispersion of
inhibitor in a continuous phase of the carrier; wherein either the
carrier is the fluid to be treated or the method further comprises
introducing the dispersion into the fluid to be treated.
14. The method of claim 13 wherein the dispersion comprises
particles, droplets, or gas bubbles of inhibitor dispersed in the
continuous phase, and wherein the average diameter of the droplets,
particles, or gas bubbles is less than about 5 .mu.m.
15. The method of claim 13 wherein the high shear device comprises
at least two generators, each generator comprising a stator and a
complementarily-shaped rotor.
16. A system for inhibiting a component in a fluid, the system
comprising: at least one high shear mixing device comprising at
least one generator comprising a rotor and a stator separated by a
shear gap, wherein the shear gap is the minimum distance between
the rotor and the stator, and wherein the high shear mixing device
is capable of producing a tip speed of the rotor of greater than
22.9 m/s (4,500 ft/min); and a pump configured for delivering a
mixture of a carrier and an inhibitor to the high shear mixing
device.
17. The system of claim 16 wherein the component is selected from
ice, scale, hydrates, acidic chemicals, and combinations
thereof.
18. The system of claim 16, further comprising: a flow line or
vessel configured for receiving the dispersion from the high shear
device.
19. The system of claim 18 wherein the vessel is a boiler.
20. The system of claim 16 wherein the at least one high shear
mixing device is configured for producing a dispersion of the
inhibitor in a continuous phase comprising the carrier, wherein the
dispersion comprises bubbles, particles, or droplets of inhibitor
having a mean diameter of less than 5 .mu.m.
21. The system of claim 16 wherein the at least one high shear
mixing device is capable of producing a tip speed of the rotor of
at least 40.1 m/s (7,900 ft/min).
22. The system of claim 16 comprising at least two high shear
mixing devices.
23. The system of claim 16 wherein the at least one high shear
device comprises at least two generators.
24. The system of claim 23 wherein the shear rate provided by one
generator is greater than the shear rate provided by another
generator.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119(e) of U.S. Provisional Patent Application No. 60/946,463
entitled "High Shear Inhibitor Injection Process," filed Jun. 27,
2007 the disclosure of which is hereby incorporated herein by
reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable.
BACKGROUND OF THE INVENTION
[0003] 1. Technical Field
[0004] The present invention relates generally to inhibitor
injection. More particularly, the present invention relates to a
system and process for inhibitor injection comprising high shear
dispersing.
[0005] 2. Background of the Invention
[0006] An inhibitor is a chemical agent added to a fluid system to
inhibit or prevent an undesirable reaction from occurring within
the fluid or with the materials present in the surrounding
environment. Numerous inhibitors are used in the petroleum,
petrochemical, and chemical industries. For example, corrosion is
recognized as a serious problem in the development of geoenergy
sources, including oil and natural gas reserves, geothermal, and
geopressured systems and leads to great costs to the industry every
year. Corrosion problems are greatly aggravated by the presence of
acid gases such as hydrogen sulfide and carbon dioxide, and by the
co-production of brine solutions. As an alternative to the use of
high alloy components which are expensive in relation to common
carbon steels, a range of corrosion inhibitors have been researched
for mitigating the occurrence of corrosion in the production and
servicing of oil and gas wells. The use of inhibitors may permit
the use of regular carbon steel components rather than more
expensive alloys. Corrosion inhibitors are injected into process
streams (for example in acidizing treatments) to inhibit corrosion
of metal equipment and wellbore components and are generally
carried in liquid steams to contact inner surfaces and other
contact surfaces of plant equipment. A corrosion inhibitor may
create a protective film or passivation layer on a metal surface
and thus inhibit corrosion by acidic components in a process
stream. For example, drill pipe may be coated with amine film to
arrest corrosion of the pipe on contact with air.
[0007] Corrosion problems may be greater when production from
deeper formations is pursued. Production of deep, sour gas reserves
and deep geopressured zones may involve high bottom hole
temperatures (as high as 200.degree. C.) and pressures (up to 140
MPa). Additionally, the produced gas may contain primarily acid
gases such as carbon dioxide and hydrogen sulfide and minor amounts
(as low as about 20%) of desired hydrocarbon such as methane. The
acid gases may be present along with high salinity sodium chloride
brine in the producing formations, with chloride contents ranging
as high as several moles per kilogram of water. Lower pH fluids are
generally more corrosive, and, with pH values which may be as low
as 2 to 3, deep downhole fluids may be very corrosive.
[0008] In the case of geopressured and geothermal systems, the acid
gas content is typically much lower. However, these systems may be
characterized by high salinity brines (as much as 150,000 ppm of
chloride, for example) and high bottom hole temperatures (up to
310.degree. C.). These fluids may have higher pH values than those
estimated for deep sour gas systems, generally in the range of 4 to
5, however higher bottom hole temperatures may increase the
potential for corrosion in such systems.
[0009] Conditions such as high acid gas (e.g. hydrogen sulfide)
concentration, severe scale deposition, ice or hydrate formation,
and flow reduction may be inhibited by injection of inhibitors. A
challenge to the application of inhibitors is that inhibitors are
typically used in small amounts as low as parts per million and
care must be taken to adequately introduce the small quantity such
that the inhibitor is uniformly dispersed in the fluid to be
treated.
[0010] Accordingly, there is a need in industry for improved
systems and processes for injecting inhibitors into fluids whereby
increased process fluid throughput, increased degree of inhibition
of undesirable component or condition, and/or the use of reduced
amounts of generally costly inhibitor may be achieved.
SUMMARY
[0011] A high shear system and process for enhancing inhibitor
injection are disclosed. The high shear process may make possible a
reduction in mass transfer limitations of conventional inhibitor
injection processes, thereby increasing the inhibitor efficiency
and potentially enabling a reduction in required amount of
inhibitor, an increased elimination/prevention of undesirable
components (for example, corrodents, ice, scale), and/or an
increase in throughout. The system and process employ an external
high shear mechanical reactor to provide enhanced conditions for
inhibition. In some embodiments, these conditions result in
accelerated chemical reactions between multiphase reactants. In
embodiments, these enhanced conditions result in enhanced
interaction between liquid components. The high shear device may be
an external pressurized high shear device that may permit reduction
in the amount of inhibitor required.
[0012] A method is provided for introducing inhibitor into a fluid
to be treated by forming a dispersion comprising droplets,
particles, or gas bubbles of the inhibitor dispersed in a
continuous phase of a carrier, wherein the droplets, particles, or
gas bubbles have a mean diameter of less than 5 .mu.m, and wherein
either the carrier is the fluid to be treated or the method further
comprises introducing the dispersion into the fluid to be treated.
The inhibitor may be selected from corrosion inhibitors,
transport-enhancing inhibitors, scale inhibitors, hydrate
inhibitors, ice-formation inhibitors, and combinations thereof. In
embodiments, the dispersion is formed from liquid or solid
inhibitor. Alternatively, the dispersion is formed from a gaseous
inhibitor. Droplets or gas bubbles of inhibitor may have a mean
diameter of less than 1 .mu.m, or less than or equal to 400 nm. In
embodiments, the fluid to be treated comprises boiler feedwater or
a transport stream comprising hydrocarbons. The carrier may
comprise at least a portion of the fluid to be treated. The carrier
may comprise LPG. Forming the dispersion may comprise subjecting a
mixture of the inhibitor and the carrier to a shear rate of greater
than about 20,000 s.sup.-1. Forming the dispersion may comprise
contacting the inhibitor and the carrier in a high shear device,
wherein the high shear device comprises at least one rotor, and
wherein the at least one rotor is rotated at a tip speed of at
least 22.9 m/s (4,500 ft/min) during formation of the dispersion.
The high shear device may produce a local pressure of at least
about 1034.2 MPa (150,000 psi) at the tip of the at least one
rotor. In applications, the energy expenditure of the high shear
device is greater than 1000 watts per cubic meter of fluid therein
during dispersion formation.
[0013] Also disclosed is a method for introducing inhibitor into a
fluid to be treated by subjecting a fluid mixture comprising
inhibitor and a carrier to a shear rate greater than 20,000
s.sup.-1 in a high shear device to produce a dispersion of
inhibitor in a continuous phase of the carrier; wherein either the
carrier is the fluid to be treated or the method further comprises
introducing the dispersion into the fluid to be treated. The
dispersion may comprise particles, droplets, or gas bubbles of
inhibitor dispersed in the continuous phase, wherein the average
diameter of the droplets, particles, or gas bubbles is less than
about 5 .mu.m. The dispersion may be stable for at least about 15
minutes at atmospheric pressure. In some applications, the high
shear device comprises at least two generators, each generator
comprising a stator and a complementarily-shaped rotor.
[0014] Also disclosed is a system for inhibiting a component in a
fluid, the system comprising at least one high shear mixing device
comprising at least one generator comprising a rotor and a stator
separated by a shear gap, wherein the shear gap is the minimum
distance between the rotor and the stator, and wherein the high
shear mixing device is capable of producing a tip speed of the
rotor of greater than 22.9 m/s (4,500 ft/min), and a pump
configured for delivering a mixture of a carrier and an inhibitor
to the high shear mixing device. The component to be inhibited may
be ice, scale, hydrates, acidic chemicals, and combinations
thereof. The system may further comprise a flow line or vessel
configured for receiving the dispersion from the high shear device.
The vessel may be a boiler. The at least one high shear mixing
device may be configured for producing a dispersion of the
inhibitor in a continuous phase comprising the carrier, wherein the
dispersion has a mean bubble, particle, or droplet diameter of less
than 5 .mu.m. In applications, the at least one high shear mixing
device is capable of producing a tip speed of the rotor of at least
40.1 m/s (7,900 ft/min). The shear gap of the at least one
generator may be in the range of from about 0.02 mm to about 5 mm.
The at least one high shear device may comprise at least two
generators. In applications, the shear rate provided by one
generator is greater than the shear rate provided by another
generator. The system may comprise at least two high shear mixing
devices.
[0015] Certain embodiments of the above-described methods or
systems potentially provide overall cost reduction by providing
increased inhibition per unit of inhibitor consumed, permitting
increased fluid throughput, permitting operation at lower
temperature and/or pressure, and/or reducing capital and/or
operating costs. These and other embodiments and potential
advantages will be apparent in the following detailed description
and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] For a more detailed description of the preferred embodiment
of the present invention, reference will now be made to the
accompanying drawings, wherein:
[0017] FIG. 1 is a schematic of an inhibitor injection system
according to an embodiment of the present disclosure comprising
external high shear dispersing.
[0018] FIG. 2 is a longitudinal cross-section view of a multi-stage
high shear device, as employed in an embodiment of the system.
NOTATION AND NOMENCLATURE
[0019] As used herein, the term "dispersion" refers to a liquefied
mixture that contains at least two distinguishable substances (or
"phases") that will not readily mix and dissolve together. As used
herein, a "dispersion" comprises a "continuous" phase (or
"matrix"), which holds therein discontinuous droplets, bubbles,
and/or particles of the other phase or substance. The term
dispersion may thus refer to foams comprising gas bubbles suspended
in a liquid continuous phase, emulsions in which droplets of a
first liquid are dispersed throughout a continuous phase comprising
a second liquid with which the first liquid is immiscible, and
continuous liquid phases throughout which solid particles are
distributed. As used herein, the term "dispersion" encompasses
continuous liquid phases throughout which gas bubbles are
distributed, continuous liquid phases throughout which solid
particles (e.g., solid catalyst) are distributed, continuous phases
of a first liquid throughout which droplets of a second liquid that
is substantially insoluble in the continuous phase are distributed,
and liquid phases throughout which any one or a combination of
solid particles, immiscible liquid droplets, and gas bubbles are
distributed. Hence, a dispersion can exist as a homogeneous mixture
in some cases (e.g., liquid/liquid phase), or as a heterogeneous
mixture (e.g., gas/liquid, solid/liquid, or gas/solid/liquid),
depending on the nature of the materials selected for
combination.
[0020] The term "inhibitor" is used herein to refer to any chemical
compound used to inhibit formation of an undesirable component in a
fluid or inhibit an undesirable condition in a flow line or vessel
or on a contact surface thereof. For the purposes of this
disclosure, the term "inhibitor" includes conventional inhibitors
as well as chemical compounds such as viscosity reducers, which may
prevent an undesirable reduction of flow rate in a flow line.
[0021] The term "flow line" is used herein to indicate any vessel
or line used to transport, hold, or contact a fluid that contains a
component to be inhibited via the inhibitor. The term "flow line"
thus encompasses lines such as piping and transport lines and
vessels including without limitation boilers, pumps, condensers,
reflux drums, and reflux pumps.
DETAILED DESCRIPTION
[0022] Overview. The rate of chemical reactions involving liquids,
gases and solids depend on time of contact, temperature, and
pressure. In cases where it is desirable to react two or more raw
materials of different phases (e.g. solid and liquid; liquid and
gas; solid, liquid and gas), one of the limiting factors
controlling the rate of reaction involves the contact time of the
reactants. When reaction rates are accelerated, residence times may
be decreased, thereby increasing obtainable throughput. Enhancing
contact via the use of high shear may permit increased throughput
and/or the use of a decreased amount of generally expensive
inhibitor relative to conventional inhibitor injection
processes.
[0023] Contact time for the reactants is often controlled by mixing
which provides contact with two or more reactants involved in a
chemical reaction. A system and process for inhibitor injection
comprises an external high shear mechanical device to provide rapid
contact and mixing of chemical ingredients in a controlled
environment in the reactor/mixer device. A reactor assembly that
comprises an external high shear device or mixer as described
herein may decrease mass transfer limitations and thereby allow an
inhibition reaction to more closely approach kinetic limitations.
In embodiments, the high shear device is used to form a dispersion
of a gas in a liquid. In other embodiments, the high shear device
is used to intimately mix two liquids, for example, hydrocarbon and
a liquid inhibitor. In embodiments, the inhibitor is a gas. In
embodiments, the inhibitor is a liquid. In applications, the
inhibitor is a gas and is injected into a liquid carrier. In
alternative applications, the inhibitor is a liquid and is injected
into a liquid carrier. In the case of homogeneous reactions, for
example liquid/liquid reactions, enhanced mixing may increase the
rate of inhibition reaction(s) and may also homogenize the
temperature within the reaction zone(s).
[0024] The disclosed high shear system and method may be
incorporated into conventional inhibitor injection processes,
thereby enhancing inhibition of an undesirable component or
condition. For example, inhibitors may be added to avoid the
production of scale, corrosion (e.g., from hydrogen sulfide, carbon
dioxide, etc.), formation of ice, formation of gas hydrates, and
the like.
[0025] Other uses of the disclosed system and method will become
apparent upon reading the disclosure and viewing the accompanying
drawings. While the following description will be given with
respect to injection of inhibitors via an injection line run
alongside a pipeline to permit injection of inhibitors or similar
treatments, other embodiments are envisioned. The embodiments
described herein are exemplary only, and are not intended to be
limiting. For example, the high shear system and process may be
used for the injection of disparate types and phases (e.g. gas or
liquid) of inhibitors into various flow lines (i.e. lines or
vessels).
[0026] System for Introduction of Inhibitor. A high shear inhibitor
injection system will now be described in relation to FIG. 1, which
is a process flow diagram of an embodiment of a high shear system
100 for introduction of inhibitor into a fluid to be treated. The
basic components of a representative system include external high
shear mixing device (HSD) 40 and pump 5, and flow line 10. The term
"flow line" is used herein to indicate any vessel or line used to
transport or hold a fluid that contains a component to be inhibited
via the inhibitor. The term "flow line" thus encompasses lines such
as piping and transport lines and vessels including without
limitation boilers, pumps, condensers, reflux drums, and reflux
pumps. As shown in FIG. 1, high shear device 40 is located external
to flow line 10. Each of these components is further described in
more detail below. Line 21 is connected to pump 5 for introducing
carrier fluid into HSD 40. Line 13 connects pump 5 to HSD 40, and
line 18 may connect HSD 40 to flow line 10. Line 22 may be
connected to line 13 for introducing inhibitor into HSD 40.
Alternatively, line 22 may be connected directly to an inlet of HSD
40. Additional components or process steps may be incorporated
between flow line 10 and HSD 40, or ahead of pump 5 or HSD 40, if
desired, as will become apparent upon reading the description of
the high shear inhibitor injection process hereinbelow. For
example, line 20 may be connected to line 21 or line 13 from flow
line 10, such that fluid in flow line 10 may be used as carrier.
Line 20 may be connected to flow line 10 at a location 14 upstream
of the position where inhibition is required, for example, upstream
of a location at which conditions for scale formation or corrosion
are predicted. In embodiments, line 21 and line 20 are a single
line connecting flow line 10 and pump 5. Treated fluid may continue
along flow line 10 downstream the intersection 16 of line 18 and
flow line 10.
[0027] High Shear Mixing Device. External high shear mixing device
(HSD) 40, also sometimes referred to as a high shear device or high
shear mixing device, is configured for receiving an inlet stream,
via line 13, comprising carrier fluid and inhibitor. Alternatively,
HSD 40 may be configured for receiving the carrier fluid and the
inhibitor via separate inlet lines (not shown). Although only one
high shear device is shown in FIG. 1, it should be understood that
some embodiments of the system may have two or more high shear
mixing devices arranged either in series or parallel flow. HSD 40
is a mechanical device that utilizes one or more generator
comprising a rotor/stator combination, each of which has a gap
between the stator and rotor. The gap between the rotor and the
stator in each generator set may be fixed or may be adjustable. HSD
40 is configured in such a way that it is capable of producing
submicron and micron-sized bubbles or droplets of inhibitor in a
continuous phase comprising the carrier flowing through the high
shear device. The high shear device comprises an enclosure or
housing so that the pressure and temperature of the fluid therein
may be controlled.
[0028] High shear mixing devices are generally divided into three
general classes, based upon their ability to mix fluids. Mixing is
the process of reducing the size of particles or inhomogeneous
species within the fluid. One metric for the degree or thoroughness
of mixing is the energy density per unit volume that the mixing
device generates to disrupt the fluid particles. The classes are
distinguished based on delivered energy densities. Three classes of
industrial mixers having sufficient energy density to consistently
produce mixtures or emulsions with particle sizes in the range of
submicron to 50 microns include homogenization valve systems,
colloid mills and high speed mixers. In the first class of high
energy devices, referred to as homogenization valve systems, fluid
to be processed is pumped under very high pressure through a
narrow-gap valve into a lower pressure environment. The pressure
gradients across the valve and the resulting turbulence and
cavitation act to break-up any particles in the fluid. These valve
systems are most commonly used in milk homogenization and can yield
average particle sizes in the submicron to about 1 micron
range.
[0029] At the opposite end of the energy density spectrum is the
third class of devices referred to as low energy devices. These
systems usually have paddles or fluid rotors that turn at high
speed in a reservoir of fluid to be processed, which in many of the
more common applications is a food product. These low energy
systems are customarily used when average particle sizes of greater
than 20 microns are acceptable in the processed fluid.
[0030] Between the low energy devices and homogenization valve
systems, in terms of the mixing energy density delivered to the
fluid, are colloid mills and other high speed rotor-stator devices,
which are classified as intermediate energy devices. A typical
colloid mill configuration includes a conical or disk rotor that is
separated from a complementary, liquid-cooled stator by a
closely-controlled rotor-stator gap, which is commonly between
0.025 mm to 10 mm (0.001-0.40 inch). Rotors are usually driven by
an electric motor through a direct drive or belt mechanism. As the
rotor rotates at high rates, it pumps fluid between the outer
surface of the rotor and the inner surface of the stator, and shear
forces generated in the gap process the fluid. Many colloid mills
with proper adjustment achieve average particle sizes of 0.1-25
microns in the processed fluid. These capabilities render colloid
mills appropriate for a variety of applications including colloid
and oil/water-based emulsion processing such as that required for
cosmetics, mayonnaise, or silicone/silver amalgam formation, to
roofing-tar mixing.
[0031] Tip speed is the circumferential distance traveled by the
tip of the rotor per unit of time. Tip speed is thus a function of
the rotor diameter and the rotational frequency. Tip speed (in
meters per minute, for example) may be calculated by multiplying
the circumferential distance transcribed by the rotor tip, 2.pi.R,
where R is the radius of the rotor (meters, for example) times the
frequency of revolution (for example revolutions per minute, rpm).
A colloid mill, for example, may have a tip speed in excess of 22.9
m/s (4500 ft/min) and may exceed 40 m/s (7900 ft/min). For the
purpose of this disclosure, the term `high shear` refers to
mechanical rotor stator devices (e.g., colloid mills or
rotor-stator dispersers) that are capable of tip speeds in excess
of 5.1 m/s. (1000 ft/min) and require an external mechanically
driven power device to drive energy into the stream of products to
be reacted. For example, in HSD 40, a tip speed in excess of 22.9
m/s (4500 ft/min) is achievable, and may exceed 40 m/s (7900
ft/min). In some embodiments, HSD 40 is capable of delivering at
least 300 L/h at a tip speed of at least 22.9 m/s (4500 ft/min).
The power consumption may be about 1.5 kW. HSD 40 combines high tip
speed with a very small shear gap to produce significant shear on
the material being processed. The amount of shear will be dependent
on the viscosity of the fluid in HSD 40. Accordingly, a local
region of elevated pressure and temperature is created at the tip
of the rotor during operation of the high shear device. In some
cases the locally elevated pressure is about 1034.2 MPa (150,000
psi). In some cases the locally elevated temperature is about
500.degree. C. In some cases, these local pressure and temperature
elevations may persist for nano or pico seconds.
[0032] An approximation of energy input into the fluid (kW/L/min)
can be estimated by measuring the motor energy (kW) and fluid
output (L/min). As mentioned above, tip speed is the velocity
(ft/min or m/s) associated with the end of the one or more
revolving elements that is creating the mechanical force applied to
the fluid. In embodiments, the energy expenditure of HSD 40 is
greater than 1000 watts per cubic meter of fluid therein. In
embodiments, the energy expenditure of HSD 40 is in the range of
from about 3000 W/m.sup.3 to about 7500 W/m.sup.3.
[0033] The shear rate is the tip speed divided by the shear gap
width (minimal clearance between the rotor and stator). The shear
rate generated in HSD 40 may be in the greater than 20,000
s.sup.-1. In some embodiments the shear rate is at least 40,000
s.sup.-1. In some embodiments the shear rate is at least 100,000
s.sup.-1. In some embodiments the shear rate is at least 500,000
s.sup.-1. In some embodiments the shear rate is at least 1,000,000
s.sup.-1. In some embodiments the shear rate is at least 1,600,000
s.sup.-1. In embodiments, the shear rate generated by HSD 40 is in
the range of from 20,000 s.sup.-1 to 100,000 s.sup.-1. For example,
in one application the rotor tip speed is about 40 m/s (7900
ft/min) and the shear gap width is 0.0254 mm (0.001 inch),
producing a shear rate of 1,600,000 s.sup.-1. In another
application the rotor tip speed is about 22.9 m/s (4500 ft/min) and
the shear gap width is 0.0254 mm (0.001 inch), producing a shear
rate of about 901,600 s.sup.-1.
[0034] HSD 40 is capable of highly dispersing the inhibitor into a
continuous phase comprising the carrier, with which it would
normally be immiscible. In some embodiments, HSD 40 comprises a
colloid mill. Suitable colloidal mills are manufactured by IKA.RTM.
Works, Inc. Wilmington, N.C. and APV North America, Inc.
Wilmington, Mass., for example. In some instances, HSD 40 comprises
the Dispax Reactor.RTM. of IKA.RTM. Works, Inc.
[0035] The high shear device comprises at least one revolving
element that creates the mechanical force applied to the fluid
therein. The high shear device comprises at least one stator and at
least one rotor separated by a clearance. For example, the rotors
may be conical or disk shaped and may be separated from a
complementarily-shaped stator. In embodiments, both the rotor and
stator comprise a plurality of circumferentially-spaced teeth. In
some embodiments, the stator(s) are adjustable to obtain the
desired shear gap between the rotor and the stator of each
generator (rotor/stator set). Grooves between the teeth of the
rotor and/or stator may alternate direction in alternate stages for
increased turbulence. Each generator may be driven by any suitable
drive system configured for providing the necessary rotation.
[0036] In some embodiments, the minimum clearance (shear gap width)
between the stator and the rotor is in the range of from about
0.025 mm (0.001 inch) to about 3 mm (0.125 inch). In certain
embodiments, the minimum clearance (shear gap width) between the
stator and rotor is about 1.5 mm (0.06 inch). In certain
configurations, the minimum clearance (shear gap) between the rotor
and stator is at least 1.7 mm (0.07 inch). The shear rate produced
by the high shear device may vary with longitudinal position along
the flow pathway. In some embodiments, the rotor is set to rotate
at a speed commensurate with the diameter of the rotor and the
desired tip speed. In some embodiments, the high shear device has a
fixed clearance (shear gap width) between the stator and rotor.
Alternatively, the high shear device has adjustable clearance
(shear gap width).
[0037] In some embodiments, HSD 40 comprises a single stage
dispersing chamber (i.e., a single rotor/stator combination, a
single generator). In some embodiments, high shear device 40 is a
multiple stage inline disperser and comprises a plurality of
generators. In certain embodiments, HSD 40 comprises at least two
generators. In other embodiments, high shear device 40 comprises at
least 3 high shear generators. In some embodiments, high shear
device 40 is a multistage mixer whereby the shear rate (which, as
mentioned above, varies proportionately with tip speed and
inversely with rotor/stator gap width) varies with longitudinal
position along the flow pathway, as further described herein
below.
[0038] In some embodiments, each stage of the external high shear
device has interchangeable mixing tools, offering flexibility. For
example, the DR 2000/4 Dispax Reactor.RTM. of IKA.RTM. Works, Inc.
Wilmington, N.C. and APV North America, Inc. Wilmington, Mass.,
comprises a three stage dispersing module. This module may comprise
up to three rotor/stator combinations (generators), with choice of
fine, medium, coarse, and super-fine for each stage. This allows
for creation of dispersions having a narrow distribution of the
desired bubble or droplet size (e.g., gas bubbles or liquid
droplets of inhibitor). In some embodiments, each of the stages is
operated with super-fine generator. In some embodiments, at least
one of the generator sets has a rotor/stator minimum clearance
(shear gap width) of greater than about 5 mm (0.2 inch). In
alternative embodiments, at least one of the generator sets has a
minimum rotor/stator clearance of greater than about 1.7 mm (0.07
inch).
[0039] Referring now to FIG. 2, there is presented a longitudinal
cross-section of a suitable high shear device 200. High shear
device 200 of FIG. 2 is a dispersing device comprising three stages
or rotor-stator combinations. High shear device 200 is a dispersing
device comprising three stages or rotor-stator combinations, 220,
230, and 240. The rotor-stator combinations may be known as
generators 220, 230, 240 or stages without limitation. Three
rotor/stator sets or generators 220, 230, and 240 are aligned in
series along drive shaft 250.
[0040] First generator 220 comprises rotor 222 and stator 227.
Second generator 230 comprises rotor 223, and stator 228. Third
generator 240 comprises rotor 224 and stator 229. For each
generator the rotor is rotatably driven by input 250 and rotates
about axis 260 as indicated by arrow 265. The direction of rotation
may be opposite that shown by arrow 265 (e.g., clockwise or
counterclockwise about axis of rotation 260). Stators 227, 228, and
229 may be fixably coupled to the wall 255 of high shear device
200.
[0041] As mentioned hereinabove, each generator has a shear gap
width which is the minimum distance between the rotor and the
stator. In the embodiment of FIG. 2, first generator 220 comprises
a first shear gap 225; second generator 230 comprises a second
shear gap 235; and third generator 240 comprises a third shear gap
245. In embodiments, shear gaps 225, 235, 245 have widths in the
range of from about 0.025 mm to about 10 mm. Alternatively, the
process comprises utilization of a high shear device 200 wherein
the gaps 225, 235, 245 have a width in the range of from about 0.5
mm to about 2.5 mm. In certain instances the shear gap width is
maintained at about 1.5 mm. Alternatively, the width of shear gaps
225, 235, 245 are different for generators 220, 230, 240. In
certain instances, the width of shear gap 225 of first generator
220 is greater than the width of shear gap 235 of second generator
230, which is in turn greater than the width of shear gap 245 of
third generator 240. As mentioned above, the generators of each
stage may be interchangeable, offering flexibility. High shear
device 200 may be configured so that the shear rate will increase
stepwise longitudinally along the direction of the flow 260.
[0042] Generators 220, 230, and 240 may comprise a coarse, medium,
fine, and super-fine characterization. Rotors 222, 223, and 224 and
stators 227, 228, and 229 may be toothed designs. Each generator
may comprise two or more sets of rotor-stator teeth. In
embodiments, rotors 222, 223, and 224 comprise more than 10 rotor
teeth circumferentially spaced about the circumference of each
rotor. In embodiments, stators 227, 228, and 229 comprise more than
ten stator teeth circumferentially spaced about the circumference
of each stator In embodiments, the inner diameter of the rotor is
about 12 cm. In embodiments, the diameter of the rotor is about 6
cm. In embodiments, the outer diameter of the stator is about 15
cm. In embodiments, the diameter of the stator is about 6.4 cm. In
some embodiments the rotors are 60 mm and the stators are 64 mm in
diameter, providing a clearance of about 4 mm. In certain
embodiments, each of three stages is operated with a super-fine
generator, comprising a shear gap of between about 0.025 mm and
about 4 mm.
[0043] High shear device 200 is configured for receiving at inlet
205 a fluid mixture from line 13. The mixture comprises inhibitor
as the dispersible phase and carrier fluid as the continuous phase.
Feed stream entering inlet 205 is pumped serially through
generators 220, 230, and then 240, such that product dispersion is
formed. Product dispersion exits high shear device 200 via outlet
210 (and line 18 of FIG. 1). The rotors 222, 223, 224 of each
generator rotate at high speed relative to the fixed stators 227,
228, 229, providing a high shear rate. The rotation of the rotors
pumps fluid, such as the feed stream entering inlet 205, outwardly
through the shear gaps (and, if present, through the spaces between
the rotor teeth and the spaces between the stator teeth), creating
a localized high shear condition. High shear forces exerted on
fluid in shear gaps 225, 235, and 245 (and, when present, in the
gaps between the rotor teeth and the stator teeth) through which
fluid flows process the fluid and create product dispersion.
Product dispersion exits high shear device 200 via high shear
outlet 210 (and line 18 of FIG. 1).
[0044] The product dispersion has an average droplet or gas bubble
size less than about 5 .mu.m. In embodiments, HSD 40 produces a
dispersion having a mean droplet or bubble size of less than about
1.5 .mu.m. In embodiments, HSD 40 produces a dispersion having a
mean droplet or bubble size of less than 1 .mu.m; preferably the
droplets or bubbles are sub-micron in diameter. In certain
instances, the average droplet or bubble size is from about 0.1
.mu.m to about 1.0 .mu.m. In embodiments, HSD 40 produces a
dispersion having a mean droplet or bubble size of less than 400
nm. In embodiments, HSD 40 produces a dispersion having a mean
droplet or bubble size of less than 100 nm. The dispersion may be
capable of remaining dispersed at atmospheric pressure for at least
about 15 minutes.
[0045] In certain instances, high shear device 200 comprises a
Dispax Reactor.RTM. of IKA.RTM. Works, Inc. Wilmington, N.C. and
APV North America, Inc. Wilmington, Mass. Several models are
available having various inlet/outlet connections, horsepower, tip
speeds, output rpm, and flow rate. Selection of the high shear
device will depend on throughput requirements and desired particle,
droplet or bubble size in dispersion in line 18 (FIG. 1) exiting
outlet 210 of high shear device 200. IKA.RTM. model DR 2000/4, for
example, comprises a belt drive, 4M generator, PTFE sealing ring,
inlet flange 25.4 mm (1 inch) sanitary clamp, outlet flange 19 mm
(3/4 inch) sanitary clamp, 2HP power, output speed of 7900 rpm,
flow capacity (water) approximately 300-700 L/h (depending on
generator), a tip speed of from 9.4-41 m/s (1850 ft/min to 8070
ft/min).
[0046] Flow Line. Flow line 10 is any line or vessel in which
inhibition of an undesirable component or condition is desired. For
instance, as indicated in the embodiment of FIG. 1, flow line 10
may be a transport pipeline. Such a pipeline may be used for
transport of hydrocarbon streams comprising water and acid gases.
In some applications, HSD 40 is positioned inline on flow line 10
such that the entirety of the fluid in flow line 10 is passed
through one or more high shear devices. In embodiments, the
entirety of the fluid passing through flow line 10 passes through
one or more high shear devices operated in series or in parallel.
In applications, flow line 10 is a vessel the use of which
comprises contact with a fluid comprising an undesirable component
or a component which may lead to formation of an undesirable
component. For example, flow line 10 may be a boiler, a pump, a
reflux drum, a condenser, or another vessel used to process a fluid
for which inhibition of an undesirable component or condition is
desired.
[0047] Inhibition will occur whenever suitable conditions (e.g.
time, inhibitor concentration, temperature, pressure, fluid
composition) exist. In this sense inhibition could occur at any
point in the flow diagram of FIG. 1 if conditions are suitable. For
example, injection of dispersion comprising inhibitor into flow
line 10 may serve to passivate the surface of flow line 10 such
that corrosion is avoided/ameliorated. In applications, the
inhibitor interacts with an acid gas component of the fluid or
carrier such that corrosion is avoided/ameliorated. In embodiments,
inhibitor injection prevents the formation of gas hydrates or ice
within flow line 10. In embodiments, inhibitor injection prevents
the formation of gas hydrates or ice within flow line 10. In
embodiments, the inhibitor serves to inhibit scale formation within
flow line 10. In applications, the inhibitor is a
viscosity-reducing agent or antifreeze.
[0048] Heat Transfer Devices. Internal or external heat transfer
devices for heating the fluid to be treated are also contemplated
in variations of the system. For example, the fluid may be heated
via any method known to one skilled in the art to help prevent ice
or hydrate formation in addition to the use of chemical inhibitor.
Some suitable locations for one or more such heat transfer devices
are between pump 5 and HSD 40, between HSD 40 and flow line 10, and
between flow line 10 and pump 5 when fluid in flow line 10 is used
as carrier fluid. Some non-limiting examples of such heat transfer
devices are shell, tube, plate, and coil heat exchangers, as are
known in the art.
[0049] Pumps. Pump 5 is configured for either continuous or
semi-continuous operation, and may be any suitable pumping device
that is capable of providing controlled flow through HSD 40 and
system 100. In applications pump 5 provides greater than 202.65 kPa
(2 atm) pressure or greater than 303.975 kPa (3 atm) pressure. Pump
5 may be a Roper Type 1 gear pump, Roper Pump Company (Commerce
Georgia) Dayton Pressure Booster Pump Model 2P372E, Dayton Electric
Co (Niles, Ill.) is one suitable pump. Preferably, all contact
parts of the pump comprise stainless steel, for example, 316
stainless steel. In some embodiments of the system, pump 5 is
capable of pressures greater than about 2026.5 kPa (20 atm). In
addition to pump 5, one or more additional, high pressure pump (not
shown) may be included in the system illustrated in FIG. 1. For
example, a booster pump, which may be similar to pump 5, may be
included between HSD 40 and flow line 10 for boosting the pressure
into flow line 10.
[0050] Process for Introduction of Inhibitor into a Fluid to be
Treated. Operation of high shear inhibitor injection system 100
will now be discussed with reference to FIG. 1. In operation for
the introduction of an inhibitor into a fluid, an inhibitor to be
dispersed is introduced into system 100 via line 22, and combined
in line 13 (or within HSD 40) with a fluid carrier.
[0051] The carrier may be the fluid to be treated or may be another
fluid utilized to form the dispersion with the inhibitor which is
subsequently injected into the fluid to be treated, for example,
via injection into flow line 10 through which the fluid to be
treated flows. The carrier may be a liquid or a gas. In
embodiments, the carrier is a portion of the fluid to be treated.
In embodiments, the carrier comprises liquid hydrocarbon. In
embodiments, the carrier comprises LPG.
[0052] The inhibitor may be a gas or a liquid. In embodiments,
inhibitor in line 22 comprises an inhibitor effective for
inhibiting the production of an undesirable component selected from
ice, acidic components, scale, or flow reducers. In embodiments,
the inhibitor is a corrosion inhibitor and interacts with acidic
components of the fluid to be treated or a contact surface (e.g.
interior wall) of flow line 10 such that corrosion of flow line 10
is minimized or prevented. Inhibitor may comprise corrosion
inhibitor effective for preventing/reducing corrosion of flow lines
10 due to a corrodent in a fluid that the flow line contacts. For
example, when flow line 10 carries a hydrocarbon fluid comprising
acid gas corrodents such as carbon dioxide, hydrogen sulfide,
and/or hydrogen chloride in the presence of water, inhibitor 22 may
be added to the fluid to inhibit corrosion.
[0053] Generally, a corrosion inhibitor is a chemical compound
that, when added in small concentration, stops or slows down
corrosion of metals and alloys. A desirable inhibitor may be
selected as known to those of skill in the art. The inhibitors
generally are applied in very small amounts, usually below 100 ppm
and more particularly in the range of from 5 to about 50 ppm. A
good corrosion inhibitor may provide 95% inhibition at
concentrations of 80 ppm, and 90% at 40 ppm. The corrosion
inhibitor may function by effecting formation of a thin film or
passivation layer on a contact surface of flow line 10. This
passivation layer may prevent access of the corrosive substance to
the material of the contact surface (e.g., metal). The so called
"passivating" inhibitors (e.g., chromate) are frequently effective
under very extreme conditions. In embodiments, the disclosed system
and method are used to protect drill pipe through which drilling
fluids containing the corrodents are passed. In such embodiments,
at least a portion of the carrier in line 21 may comprise the fluid
to be treated. The corrosion inhibitor may inhibit either oxidation
or reduction of the redox corrosion system (anodic and cathodic
inhibitors). The corrosion inhibitor may scavenge dissolved oxygen.
In applications, the corrosion inhibitor may provide a combination
of two or more of these protection mechanisms.
[0054] The corrosive component of the fluid to be treated may be
one or more of hydrogen sulfide, carbon dioxide, and sodium
chloride. In embodiments, corrosion inhibitor in line 22 comprises
hexamine, phenylenediamine, dimethylethanolamine, sodium nitrite,
cinnamaldehyde, condensation products of aldehydes and amines
(imines), chromates, nitrites, phosphates, hydrazine, ascorbic
acid, and combinations thereof. The suitability of any given
inhibitor for a certain application depends on the material of the
contact surfaces, the nature of the corrodents and other components
of the fluid into which the inhibitors are added and the operating
temperature.
[0055] In embodiments, the high shear system and method are used to
ameliorate reactive sulfur corrosion e.g. from hydrogen sulfide,
which may occur in either the liquid or vapor phase. In
embodiments, high shear system 100 is used to ameliorate naphthenic
acid corrosion which tends to occur in liquid and in condensate
phases and may be enhanced in high velocity regions.
[0056] U.S. Pat. No. 5,961,885 describes a corrosion inhibitor
comprising a dispersant, an imidazoline, an amide, an alkyl
pyridine and a heavy aromatic solvent. The resultant blend
effectively inhibits corrosion of flow lines containing low pH
mixtures of hydrocarbons, water, and acid gases. In an embodiment,
the inhibitor in line 22 is a corrosion inhibitor as described in
U.S. Pat. No. 5,961,885 comprising a dispersant, an imidazoline, an
amide, an alkyl pyridine and a heavy aromatic solvent.
[0057] U.S. Pat. No. 5,188,179 describes methods for inhibiting
corrosion in oil field pipe by continuously bringing reactants
together in a fluid passing through the pipe to form a precipitated
film of iron disulfide on the interior wall of the pipe as an
amorphous corrosion inhibiting coating which is continuously being
removed away and also being continuously replenished by the
continuing reaction of the reactants. The corrosion inhibiting film
which is formed is a precipitate film formed by the reaction of a
polysulfide with ferrous iron. The ferrous iron may be a
constituent of the fluid to be treated or separately introduced.
The polysulfide is the reaction product of hydrogen sulfide as a
constituent existing in the passing fluid and an oxidizing agent
such as ammonium nitrate which is separately introduced into the
passing fluid. In embodiments, the inhibitor is a corrosion
inhibitor comprising an oxidizing agent which reacts with hydrogen
sulfide in the carrier or corrosive fluid to be treated to produce
a polysulfide which then reacts with ferrous iron in the fluid to
be treated to precipitate a corrosion inhibiting film on a contact
surface of flow line 10.
[0058] The inhibitor may be a scale inhibitor which inhibits
production of scale in flow line 10. Scale deposits can occur in
brine when the solubility of the inorganic species in the brine
decreases due to changes in the pressure and/or temperature or upon
mixing of incompatible waters. Primary scales include sulfates
(BaSO.sub.4, CaSO.sub.4, SrSO.sub.4) and carbonates (CaCO.sub.3,
MgCO.sub.3, FeCO.sub.3). Carbonates can form in a transport line
due to reduction of the system pressure, which reduces the amount
of carbon dioxide solubilized in the brine. Sulfates can form due
to mixing of incompatible brines (seawater and formation brine) or
reduction of temperature, for example seawater injection into a
formation with barium.
[0059] Scale inhibitors may be selected from sulfonated compounds,
polymer based inhibitors and phosphonates. In embodiments, the
inhibitor may comprise phosphine-polycarboxylate acid (PPCA) for
the inhibition of scale production. Typical dosage of scale
inhibitor is about 5-100 ppm.
[0060] In embodiments, high shear system 100 is utilized for scale
control in, for example, a transport flow line 10. Inhibitor may be
injected upstream of the point of scale risk. In embodiments, the
injection of scale inhibitor into flow line 10 via high shear
device 40 is before or while the fluid is downhole. In embodiments,
the injection of scale inhibitor into flow line 10 is into or
upstream a wax eater unit.
[0061] Inhibitor may be a hydrate inhibitor which minimizes or
prevents production of hydrates (e.g. gas hydrates) in flow line
10. The inhibitor may be an ice inhibitor, such as antifreeze which
prevents/minimizes production of ice and flow reduction in flow
line 10. The inhibitor may be a viscosity reducer, which helps
maintain flow within flow line 10.
[0062] The concentration of inhibitor will normally be correlated
with the concentration of reactant components in the fluid volume
to be treated, for example, the concentration of acidic components
in the fluid in flow line 10. Inhibitor in line 22 is intimately
mixed, via high shear device 40, with carrier in 21. In
applications, carrier in line 21 comprises a slipstream drawn from
flow line 10. In such instance, the carrier is the same fluid as
the fluid to be treated (e.g. line 21 and line 20 may be a single
line). In alternative embodiments, the entirety of fluid in flow
line 10 is sent through one or more high shear mixers, in series or
in parallel, to intimately mix the contents of flow line 10 with
inhibitor.
[0063] In embodiments, the inhibitor is fed directly into HSD 40,
instead of being combined with the carrier in line 13. Pump 5 may
be operated to pump the carrier through line 21, providing a
controlled flow throughout high shear device (HSD) 40 and high
shear system 100. Pump 5 may build pressure and feed HSD 40. In
some embodiments, pump 5 increases the pressure of the HSD inlet
stream in line 13 to greater than 200 kPa (2 atm) or greater than
about 300 kPa (3 atmospheres). In this way, high shear system 100
may combine high shear with pressure to enhance reactant intimate
mixing.
[0064] After pumping, the inhibitor and carrier are mixed within
HSD 40, which serves to create a fine dispersion of the inhibitor
in the carrier fluid. In HSD 40, the inhibitor and carrier are
highly dispersed such that nanobubbles, submicron-sized bubbles,
and/or microbubbles of gaseous inhibitor or nanodroplets,
submicron-sized droplets, and/or microdroplets of liquid inhibitor
are formed for superior dissolution into solution and enhancement
of fluid mixing. For example, disperser IKA.RTM. model DR 2000/4, a
high shear, three stage dispersing device configured with three
rotors in combination with stators, aligned in series, may be used
to create the dispersion of inhibitor in fluid carrier. The
rotor/stator sets may be configured as illustrated in FIG. 2, for
example. The combined mixture of inhibitor and carrier may enter
the high shear device via line 13 and enter a first stage
rotor/stator combination. The rotors and stators of the first stage
may have circumferentially spaced first stage rotor teeth and
stator teeth, respectively. The coarse dispersion exiting the first
stage enters the second rotor/stator stage. The rotor and stator of
the second stage may also comprise circumferentially spaced rotor
teeth and stator teeth, respectively. The reduced bubble or
droplet-size dispersion emerging from the second stage enters the
third stage rotor/stator combination, which may comprise a rotor
and a stator having rotor teeth and stator teeth, respectively. The
dispersion exits the high shear device via line 18. In some
embodiments, the shear rate increases stepwise longitudinally along
the direction of the flow, 260.
[0065] For example, in some embodiments, the shear rate in the
first rotor/stator stage is greater than the shear rate in
subsequent stage(s). In other embodiments, the shear rate is
substantially constant along the direction of the flow, with the
shear rate in each stage being substantially the same.
[0066] If HSD 40 includes a PTFE seal, the seal may be cooled using
any suitable technique that is known in the art. For example,
carrier in line 21, fluid mixture in line 13, or fluid in flow line
10 may be used to cool the seal and in so doing be preheated prior
to entering high shear device 40.
[0067] The rotor(s) of HSD 40 may be set to rotate at a speed
commensurate with the diameter of the rotor and the desired tip
speed. As described above, the high shear device (e.g., colloid
mill or toothed rim disperser) has either a fixed clearance between
the stator and rotor or has adjustable clearance. HSD 40 serves to
intimately mix the inhibitor and the carrier fluid. In some
embodiments of the process, the transport resistance is reduced by
operation of the high shear device such that the velocity of the
reaction is increased by greater than about 5%. In some embodiments
of the process, the transport resistance is reduced by operation of
the high shear device such that the velocity of the reaction is
increased by greater than a factor of about 5. In some embodiments,
the velocity of the reaction is increased by at least a factor of
10. In some embodiments, the velocity is increased by a factor in
the range of about 10 to about 100 fold.
[0068] In some embodiments, HSD 40 delivers at least 300 L/h at a
tip speed of at least 4500 ft/min, and which may exceed 7900 ft/min
(40 m/s). The power consumption may be about 1.5 kW. Although
measurement of instantaneous temperature and pressure at the tip of
a rotating shear unit or revolving element in HSD 40 is difficult,
it is estimated that the localized temperature seen by the
intimately mixed fluid is in excess of 500.degree. C. and at
pressures in excess of 500 kg/cm.sup.2 under cavitation conditions.
The high shear mixing results in dispersion of the inhibitor in
micron or submicron-sized bubbles or droplets. In some embodiments,
the resultant dispersion has an average bubble or droplet size less
than about 1.5 .mu.m. Accordingly, the dispersion exiting HSD 40
via line 18 comprises micron and/or submicron-sized droplets or gas
bubbles. In some embodiments, the mean bubble or droplet size is in
the range of about 0.4 .mu.m to about 1.5 .mu.m. In some
embodiments, the resultant dispersion has an average bubble or
droplet size less than 1 .mu.m. In some embodiments, the mean
bubble or droplet size is less than about 400 nm, and may be about
100 nm in some cases. In many embodiments, the dispersion is able
to remain dispersed at atmospheric pressure for at least 15
minutes.
[0069] Once dispersed, the resulting gas/liquid or liquid/liquid
dispersion exits HSD 40 via line 18 and feeds into flow line 10, as
illustrated in FIG. 1. The contents of flow line 10 may be
maintained at a specified reaction temperature using heating and/or
cooling capabilities (e.g., heaters) and temperature measurement
instrumentation. Pressure in the flow line may be monitored using
suitable pressure measurement instrumentation, employing techniques
that are known to those of skill in the art.
[0070] Conditions of temperature, pressure, space velocity and
inhibitor injection per volume of fluid to be treated may be
calculated as known to those of skill in the art. The use of high
shear device 40 may allow for better interaction and more uniform
mixing of the inhibitor with the fluid to be treated and may
therefore permit a reduction in the amount of inhibitor utilized,
and/or an increase in possible throughout. In some embodiments, the
operating conditions of system 100 comprise a temperature of at or
near ambient temperature. In embodiments, flow line 10 is operated
at or near atmospheric pressure.
[0071] Optionally, the product dispersion in line 18 may be further
processed prior to entering flow line 10, if desired. In flow line
10, inhibition of undesirable component or condition occurs or
continues. For example, if inhibitor in line 22 is corrosion
inhibitor, passivation of surfaces within flow line 10 may occur.
In embodiments, the injection of dispersion in line 18 into flow
line 10 prevents ice formation, flow reduction, or scaling within
flow line 10, as discussed hereinabove. Fluid in line 10 downstream
of injection location 16 having been treated with inhibitor may
proceed to flow along flow line 10.
[0072] Multiple Pass Operation. In the embodiment shown in FIG. 1,
the system is configured for single pass operation, wherein the
treated fluid beyond injection point 16 in line 10 continues along
flow line 10. In some embodiments, flow line 10 may comprise a
vessel, such as a boiler. In such embodiments, it may be desirable
to pass the contents of flow line 10, or a liquid fraction thereof,
through HSD 40 during a second pass. In this case, at least a
portion of the contents of flow line 10 may be recycled from flow
line 10 and pumped by pump 5 into line 13 and thence into HSD 40.
Additional inhibitor may be injected via line 22 into line 13, or
it may be added directly into the high shear device (not shown). In
other embodiments, product stream in beyond injection location 16
may be further treated prior to recycle of a portion thereof being
recycled to high shear device 40.
[0073] Multiple High Shear Mixing Devices. In some embodiments, two
or more high shear devices like HSD 40, or configured differently,
are aligned in series, and are used to further inhibit an
undesirable component or condition. In embodiments, a plurality of
high shear mixers is positioned along a transport or process flow
line 10 whereby inhibitor is added at many locations 16 along the
line via multiple high shear mixers. Operation of the mixers may be
in either batch or continuous mode. In some instances in which a
single pass or "once through" process is desired, the use of
multiple high shear devices in series may also be advantageous. For
examples, in embodiments, the entirety of the fluid flow in flow
line 10 is passed through multiple high shear devices 40 in serial
or parallel flow such that all of the fluid in flow line 10 is
contacted with inhibitor via high shear. For example, in
embodiments, outlet dispersion in line 18 is fed into a second high
shear device. When multiple high shear devices 40 are operated in
series, additional inhibitor may be injected into the inlet
feedstream of each device. In some embodiments, multiple high shear
devices 40 are operated in parallel, and the outlet dispersions
therefrom are introduced into one or more flow lines 10.
[0074] Features. The increased surface area of the micrometer sized
and/or submicrometer sized inhibitor droplets or gas bubbles in the
dispersion in line 18 produced within high shear device 40 may
result in faster and/or more complete inhibition of undesirable
conditions or components within flow line 10.
[0075] While the description has been given with respect to a
system incorporating inhibitor injection into a pipeline, it is to
be understood that the disclosed system and method are applicable
to the injection of various inhibitors, including, but not limited
to, inhibitors for the reduction of scale production, inhibitor for
the prevention of gas hydrate formation, inhibitors for prevention
of corrosion, injections of materials for enhancing the flow of
transport streams, for example, antifreeze, viscosity-reducers, and
combinations thereof. The inhibitor may be added as a solid, a
liquid, or a gas and may be mixed with a liquid or a gas carrier.
For example, solid inhibitor in line 22 may be added to high shear
device 40 where it is intimately mixed with carrier fluid
introduced via line 21.
[0076] In embodiments, use of the disclosed process comprising
reactant mixing via external high shear device 40 allows use of
reduced quantities of inhibitor than conventional inhibition and/or
increases the degree of inhibition. In embodiments, the method
comprises incorporating external high shear device 40 into an
established process thereby reducing the amount of inhibitor
required to effect inhibition and/or enabling the increase in
production throughput from a process operated without high shear
device 40. In embodiments, the disclosed method reduces operating
costs/increases production from an existing process. Alternatively,
the disclosed method may reduce capital costs for the design of new
processes.
[0077] Without wishing to be limited to a particular theory, it is
believed that the level or degree of high shear mixing may be
sufficient to increase rates of mass transfer and also produce
localized non-ideal conditions that enable reactions to occur that
would not otherwise be expected to occur based on Gibbs free energy
predictions. Localized non ideal conditions are believed to occur
within the high shear device resulting in increased temperatures
and pressures with the most significant increase believed to be in
localized pressures. The increase in pressures and temperatures
within the high shear device are instantaneous and localized and
quickly revert back to bulk or average system conditions once
exiting the high shear device. In some cases, the high shear mixing
device induces cavitation of sufficient intensity to dissociate one
or more of the reactants into free radicals, which may intensify a
chemical reaction or allow a reaction to take place at less
stringent conditions than might otherwise be required. Cavitation
may also increase rates of transport processes by producing local
turbulence and liquid micro-circulation (acoustic streaming). An
overview of the application of cavitation phenomenon in
chemical/physical processing applications is provided by Gogate et
al., "Cavitation: A technology on the horizon," Current Science 91
(No. 1): 35-46 (2006). The high shear mixing device of certain
embodiments of the present system and methods induces cavitation
whereby inhibitor and/or carrier fluid are dissociated into free
radicals, which then react to provide inhibition of undesirable
components of a fluid or undesirable conditions in a flow line
10.
[0078] While preferred embodiments of the invention have been shown
and described, modifications thereof can be made by one skilled in
the art without departing from the spirit and teachings of the
invention. The embodiments described herein are exemplary only, and
are not intended to be limiting. Many variations and modifications
of the invention disclosed herein are possible and are within the
scope of the invention. Where numerical ranges or limitations are
expressly stated, such express ranges or limitations should be
understood to include iterative ranges or limitations of like
magnitude falling within the expressly stated ranges or limitations
(e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater
than 0.10 includes 0.11, 0.12, 0.13, and so forth). Use of the term
"optionally" with respect to any element of a claim is intended to
mean that the subject element is required, or alternatively, is not
required. Both alternatives are intended to be within the scope of
the claim. Use of broader terms such as comprises, includes,
having, etc. should be understood to provide support for narrower
terms such as consisting of, consisting essentially of, comprised
substantially of, and the like.
[0079] Accordingly, the scope of protection is not limited by the
description set out above but is only limited by the claims which
follow, that scope including all equivalents of the subject matter
of the claims. Each and every claim is incorporated into the
specification as an embodiment of the present invention. Thus, the
claims are a further description and are an addition to the
preferred embodiments of the present invention. The disclosures of
all patents, patent applications, and publications cited herein are
hereby incorporated by reference, to the extent they provide
exemplary, procedural or other details supplementary to those set
forth herein.
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