U.S. patent application number 16/513156 was filed with the patent office on 2019-11-07 for coalescer for co-current contactors.
The applicant listed for this patent is J. Tim Cullinane, Stephanie A. Freeman, Edward J. Grave, P. Scott Northrop, Norman K. Yeh. Invention is credited to J. Tim Cullinane, Stephanie A. Freeman, Edward J. Grave, P. Scott Northrop, Norman K. Yeh.
Application Number | 20190336908 16/513156 |
Document ID | / |
Family ID | 55447099 |
Filed Date | 2019-11-07 |
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United States Patent
Application |
20190336908 |
Kind Code |
A1 |
Freeman; Stephanie A. ; et
al. |
November 7, 2019 |
Coalescer for Co-Current Contactors
Abstract
The disclosure includes a method, comprising passing a fluid
into a co-current contactor, passing a solvent into the co-current
contactor, dividing the solvent into solvent droplets having a
first average droplet size, placing the fluid in contact with the
solvent droplets to create a combined stream, coalescing at least a
portion of the solvent droplets to create solvent droplets having a
second average droplet size, wherein the second average droplet
size is greater than the first average droplet size, and separating
the fluid and the solvent.
Inventors: |
Freeman; Stephanie A.;
(Houston, TX) ; Grave; Edward J.; (Montgomery,
TX) ; Cullinane; J. Tim; (Montgomery, TX) ;
Northrop; P. Scott; (Spring, TX) ; Yeh; Norman
K.; (Shenandoah, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Freeman; Stephanie A.
Grave; Edward J.
Cullinane; J. Tim
Northrop; P. Scott
Yeh; Norman K. |
Houston
Montgomery
Montgomery
Spring
Shenandoah |
TX
TX
TX
TX
TX |
US
US
US
US
US |
|
|
Family ID: |
55447099 |
Appl. No.: |
16/513156 |
Filed: |
July 16, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15009936 |
Jan 29, 2016 |
10391442 |
|
|
16513156 |
|
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62132631 |
Mar 13, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 2300/207 20130101;
B01D 53/1462 20130101; C10L 3/10 20130101; B01D 11/0488 20130101;
C10G 21/16 20130101; C10G 70/06 20130101; C10L 2290/18 20130101;
B01D 11/0419 20130101; C10L 3/104 20130101; C10G 21/00 20130101;
C10L 2290/541 20130101; B01D 11/04 20130101; B01D 53/18 20130101;
B01D 2252/204 20130101; B01D 53/79 20130101; C10G 21/30 20130101;
B01D 2011/005 20130101; B01D 2257/504 20130101; C10L 3/103
20130101; B01D 53/1406 20130101; B01D 53/526 20130101; B01D
2257/304 20130101 |
International
Class: |
B01D 53/14 20060101
B01D053/14; B01D 53/18 20060101 B01D053/18; C10L 3/10 20060101
C10L003/10; B01D 53/52 20060101 B01D053/52; B01D 53/79 20060101
B01D053/79; C10G 21/16 20060101 C10G021/16; C10G 21/30 20060101
C10G021/30; C10G 70/06 20060101 C10G070/06; B01D 11/04 20060101
B01D011/04 |
Claims
1. A method, comprising: passing a fluid into a co-current
contactor, the fluid including a hydrocarbon and a contaminant;
passing a solvent into the co-current contactor; dividing the
solvent into solvent droplets having a first average droplet size;
placing the fluid in contact with the solvent droplets to create a
combined stream; absorbing the contaminant into the solvent
droplets; coalescing at least a portion of the solvent droplets to
create solvent droplets having a second average droplet size,
wherein the second average droplet size is greater than the first
average droplet size; separating the fluid from the solvent
droplets; collecting the solvent droplets in a boot; and recycling
gas, collecting in the boot, to the co-current contactor via a
recycle gas inlet.
2. The method of claim 1, wherein the first average droplet size is
between less than about 1 micrometer (.mu.m) and about 1000
.mu.m.
3. The method of claim 1, wherein the second average droplet size
is between about 2 micrometers (.mu.m) and about 10000 .mu.m.
4. The method of claim 1, wherein coalescing comprises electrically
inducing coalescence, mechanically inducing coalescence, or
both.
5. The method of claim 1, wherein coalescing takes between less
than about 0.01 seconds and about 15 seconds of residence time.
6. The method of claim 1, wherein coalescing comprises passing the
combined stream through a pre-coalescer to create solvent droplets
having a third average droplet size, wherein the third average
droplet size is greater than the first average droplet size and
less than the second average droplet size.
7. The method of claim 1, wherein the fluid and the solvent are
liquids.
8-20. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority benefit of U.S. Patent
Application 62/132,631 filed Mar. 13, 2015 entitled COALESCER FOR
CO-CURRENT CONTACTORS, the entirety of Which is incorporated by
reference herein.
BACKGROUND
[0002] The production of hydrocarbons from a reservoir oftentimes
carries with it the incidental production of non-hydrocarbon gases.
Such gases include contaminants such as hydrogen sulfide (H.sub.2S)
and carbon dioxide (CO.sub.2). When H.sub.2S or CO.sub.2 are
produced as part of a hydrocarbon stream (such as methane or
ethane), the raw gas stream is sometimes referred to as "sour gas."
The H.sub.2S and CO.sub.2 are often referred to together as "acid
gases."
[0003] In addition to hydrocarbon production streams, acid gases
may be associated with synthesis gas streams, or with refinery gas
streams. Acid gases may also be present within so-called flash-gas
streams in gas processing facilities. Further, acid gases may be
generated by the combustion of coal, natural gas, or other
carbonaceous fuels.
[0004] Gas and/or hydrocarbon fluid streams may contain not only
H.sub.2S or CO.sub.2, but may also contain other "acidic"
impurities. These include mercaptans and other trace sulfur
compounds (SO.sub.x). In addition, natural gas streams may contain
water. Indeed, water is the most common contaminant in many natural
gas streams. Such impurities should be removed prior to industrial
or residential use.
[0005] Processes have been devised to remove contaminants from a
raw natural gas stream. In the case of acid gases, cryogenic gas
processing is sometimes used, particularly to remove CO.sub.2 to
prevent line freezing and plugged orifices. In other instances,
particularly with H.sub.2S removal, the hydrocarbon fluid stream is
treated with a solvent. Solvents may include chemical solvents such
as amines. Examples of amines used in sour gas treatment include
monoethanol amine (MEA), diethanol amine (DEA), and methyl
diethanol amine (MDEA).
[0006] Physical solvents are sometimes used in lieu of amine
solvents. Examples include physical solvents currently marketed
under the brand names Selexol.RTM. (comprising dimethyl ethers of
polyethylene glycol) and Rectisol.TM. (comprising methanol). In
some instances hybrid solvents, meaning mixtures of physical and
chemical solvents, have been used. An example of one such hybrid
solvent is currently marketed under the brand name Sulfinol.RTM.
(comprising sulfolane, water, and one or more amines). However, the
use of amine-based acid gas removal solvents is most common.
[0007] Amine-based solvents rely on a chemical reaction with the
acid gases. The reaction process is sometimes referred to as "gas
sweetening." Such chemical reactions are generally more effective
than the physical-based solvents, particularly at feed gas
pressures below about 300 pounds per square inch absolute (psia)
(about 20 bar). There are instances where special chemical solvents
such as Flexsorb.RTM. (comprising hindered amine) are used,
particularly for selectively removing H.sub.2S from H.sub.2S and
CO.sub.2-containing gas and/or hydrocarbon fluid streams.
[0008] As a result of the gas sweetening process, a treated or
"sweetened" gas stream is created. The sweetened gas stream is
substantially depleted of H.sub.2S and/or CO.sub.2 components. The
sweetened gas can be further processed for liquids recovery, that
is, by condensing out heavier hydrocarbon gases. The sweet gas may
be sold into a pipeline or may be used for liquefied natural gas
(LNG) feed. In addition, the sweetened gas stream may be used as
feedstock for a gas-to-liquids process, and then ultimately used to
make waxes, butanes, lubricants, glycols and other petroleum-based
products. The extracted CO.sub.2 may be sold, or it may be injected
into a subterranean reservoir for enhanced oil recovery
operations.
[0009] When a natural gas stream contains water, a dehydration
process is usually undertaken before or after acid gas removal.
This is done through the use of glycol or other desiccant in a
water separator. The dehydration of natural gas is done to control
the formation of gas hydrates and to prevent corrosion in
distribution pipelines. The formation of gas hydrates and corrosion
in pipelines can cause a decrease in flow volume as well as frozen
control valves, plugged orifices and other operating problems.
[0010] Traditionally, the removal of acid gases or water using
chemical solvents or desiccants involves counter-currently
contacting the raw natural gas stream with the chemical. The raw
gas stream is introduced into the bottom section of a contacting
tower, or absorption tower. At the same time, the solvent solution
is directed into a top section of the tower. The tower has trays,
packing, or other "internals." As the solvent cascades through the
internals, it absorbs the undesirable components, carrying them
away through the bottom of the contacting tower as part of a "rich"
solvent solution. At the same time, gaseous fluid that is largely
depleted of the undesirable components exits at the top of the
tower.
[0011] The rich solvent or rich glycol, as the case may be, that
exits the contactor is sometimes referred to as an absorbent
liquid. Following absorption, a process of regeneration (also
called "desorption") may be employed to separate contaminants from
the active solvent of the absorbent liquid. This produces a "lean"
solvent or a "lean" glycol that is then typically recycled into the
contacting tower for further absorption.
[0012] While perhaps capable of performing desired contacting for
removal of contaminants from a gas and/or hydrocarbon-containing
fluid stream, historic contactor designs have had difficulty
scaling-up from lab and/or pilot-sized units to units capable of
efficiently processing up to a billion standard cubic feet per day
(BSFD) of gas. Past scale-up designs have high capital expenses
(e.g., due to having larger and more pieces of equipment, more
complicated transportation and installation, etc.) and high
operational expenses (e.g., due to less reliability and/or
operability, larger size and weight equipment, etc.). Consequently,
a need exists for a contacting designs that is smaller, has fewer
pieces of equipment, has improved operability and reliability, is
easier to transport and install, and weighs less than traditional
contacting equipment.
SUMMARY OF THE INVENTION
[0013] The disclosure includes a method, comprising passing a fluid
into a co-current contactor, passing a solvent into the co-current
contactor, dividing the solvent into solvent droplets having a
first average droplet size, placing the fluid in contact with the
solvent droplets to create a combined stream, coalescing at least a
portion of the solvent droplets to create solvent droplets having a
second average droplet size, wherein the second average droplet
size is greater than the first average droplet size, and separating
the fluid and the solvent.
[0014] The disclosure includes a co-current contactor apparatus,
comprising a first inlet configured to receive a first fluid stream
proximate to a first end of the co-current contactor, a second
inlet configured to receive a second fluid stream proximate to the
first end of the co-current contactor, an inlet section configured
to atomize at least a portion of the second fluid stream, a mass
transfer section configured to receive the first fluid stream and
the atomized second fluid stream, and to pass the atomized second
fluid stream and the the first fluid stream as a combined stream, a
coalescer configured receive the combined stream, and to increase
an average droplet size of the atomized second fluid stream, and a
separator configured to separate at least a portion of the atomized
second fluid stream from the combined stream.
[0015] The disclosure includes a co-current contacting system,
comprising a plurality of co-current contactors coupled in a
counter-current configuration, wherein each co-current contactor
comprises a first inlet configured to receive a first fluid stream
proximate to a first end of the co-current contactor, a second
inlet configured to receive a second fluid stream proximate to the
first end of the co-current contactor, an inlet section configured
to atomize at least a portion of the second fluid stream, a mass
transfer section configured to receive the first fluid stream and
the atomized second fluid stream, and to pass the atomized second
fluid stream and the the first fluid stream as a combined stream, a
coalescer configured to receive the combined stream, and to
increase the average droplet size of the atomized second fluid
stream, and a separator configured to separate at least a portion
of the atomized second fluid stream from the combined stream.
[0016] It is understood that the methods above may be used to
remove a contaminant, e.g., an acid gas component, a water
component, etc., from other fluid streams. These separated fluid
streams may include, for example, a sour water stream, a flash-gas
stream, or a Claus tail gas stream.
DESCRIPTION OF THE DRAWINGS
[0017] So that the manner in which the present invention can be
better understood, certain illustrations, charts and/or flow charts
are appended hereto. It is to be noted, however, that the drawings
illustrate only selected embodiments of the inventions and are
therefore not to be considered limiting of scope, for the
inventions may admit to other equally effective embodiments and
applications.
[0018] FIG. 1A is a process flow diagram of a gas processing system
that includes a co-current flow scheme.
[0019] FIG. 1B is a process flow diagram of another gas processing
system that includes a co-current flow scheme.
[0020] FIG. 2 is a schematic diagram of a co-current contacting
system comprising multiple co-current contactors.
[0021] FIG. 3 is a side view of an embodiment of a single stage
multiple co-current contactor bundle configuration.
[0022] FIG. 4 is a schematic diagram of an embodiment of a
co-current contactor having a coalescing section.
DETAILED DESCRIPTION
[0023] As used herein, an "acid gas" means any gas that dissolves
in water producing an acidic solution. Non-limiting examples of
acid gases include hydrogen sulfide (H.sub.2S), carbon dioxide
(CO.sub.2), sulfur dioxide (SO.sub.2), carbon disulfide (CS.sub.2),
carbonyl sulfide (COS), mercaptans, or mixtures thereof.
[0024] As used herein, the term "atomize" means to divide, reduce,
or otherwise convert a liquid into minute particles, a mist, or a
fine spray of droplets having an average droplet size within a
predetermined range.
[0025] As used herein, the term "co-current contacting device" or
"co-current contactor" means an apparatus, e.g., a pipe, a vessel,
a housing, an assembly, etc., that receives (i) a stream of gas (or
other fluid stream to be treated) and (ii) a separate stream of
solvent (or other fluid treating solution) in such a manner that
the gas stream and the solvent stream contact one another while
flowing in generally the same direction within the contacting
device.
[0026] As used herein, the term "contaminant" means an acid gas,
water, another undesirable component, or a combination thereof
absorbable by a selected solvent.
[0027] As used herein, the term "flue gas" means any gas stream
generated as a by-product of hydrocarbon combustion.
[0028] As used herein, the term "fluid" refers to gases, liquids,
and combinations of gases and liquids, as well as to combinations
of gases and solids, and combinations of liquids and solids.
[0029] As used herein, the term "hydrocarbon" refers to an organic
compound that includes primarily, if not exclusively, the elements
hydrogen and carbon. Hydrocarbons generally fall into two classes:
aliphatic, or straight chain hydrocarbons, and cyclic, or closed
ring, hydrocarbons including cyclic terpenes. Examples of
hydrocarbon-containing materials include any form of natural gas,
oil, coal, and bitumen that can be used as a fuel or upgraded into
a fuel.
[0030] As used herein, the term "industrial plant" refers to any
plant that generates a stream containing at least one hydrocarbon
or an acid gas. One non-limiting example is a coal-powered
electrical generation plant. Another example is a cement plant that
emits CO.sub.2 at low pressures.
[0031] With respect to fluid processing equipment, the term
"inline" may mean that two or more items are placed along a flow
line such that a fluid stream undergoing fluid separation moves
from one item of equipment to the next while maintaining flow in a
substantially constant downstream direction, and/or that the two or
more items are connected sequentially or, more preferably, are
integrated into a single tubular device.
[0032] As used herein, the terms "lean" and "rich," with respect to
the absorbent liquid removal of a selected gas component from a gas
stream, are relative, merely implying, respectively, a lesser or
greater degree of content of the selected gas component. The
respective terms "lean" and "rich" do not necessarily indicate or
require, respectively, either that an absorbent liquid is totally
devoid of the selected gaseous component, or that it is incapable
of absorbing more of the selected gas component. In fact, it is
preferred, as will be evident hereinafter, that the so called
"rich" absorbent liquid produced in a first contactor in a series
of two or more contactors retains significant or substantial
residual absorptive capacity. Conversely, a "lean" absorbent liquid
will be understood to be capable of substantial absorption, but may
retain a minor concentration of the gas component being
removed.
[0033] As used herein, the term "natural gas" refers to a
multi-component gas obtained from a crude oil well (associated gas)
or from a subterranean gas-bearing formation (non-associated gas).
The composition and pressure of natural gas can vary significantly.
A typical natural gas stream contains methane (C.sub.1) as a
significant component. The natural gas stream may also contain
ethane (C.sub.2), higher molecular weight hydrocarbons, one or more
acid gases, and water. The natural gas may also contain minor
amounts of contaminants such as nitrogen, iron sulfide, and
wax.
[0034] As used herein, the term "non-absorbing gas" means a gas
that is not absorbed by a solvent during a gas treating or
conditioning process, e.g., during co-current contacting.
[0035] As used herein, the term "solvent" means a liquid phase
fluid or a multiphase fluid (a fluid comprising both a liquid and
gas phase) that preferentially absorbs one or more component over
other components. For example, a solvent may preferentially absorb
a contaminant, e.g., acid gas, thereby removing or "scrubbing" at
least a portion of the contaminant from a contaminated stream,
e.g., a contaminated natural gas stream.
[0036] As used herein, the term "sweetened gas stream" refers to a
fluid stream in a substantially gaseous phase that has had at least
a portion of acid gas components removed. Further, the term
"sweetened" may also refer to a fluid stream that has been
subjected to a dehydration or other conditioning process.
Description of Specific Embodiments
[0037] FIG. 1A is a process flow diagram of a gas processing system
100 that includes a co-current flow scheme arranged in a counter
current configuration. The gas processing system 100 may be used
for the removal of H.sub.2S or other acid gas components from a gas
stream 102. In addition, in some embodiments, the gas processing
system 100 may be used for the removal of water or other impurities
from the gas stream 102.
[0038] The gas processing system 100 may employ a number of
vertically oriented co-current contacting systems 104A-F. In some
embodiments, each vertically oriented co-current contacting system
104A-F includes vertically oriented co-current contactor upstream
of a separation system. In other embodiments, each vertically
oriented co-current contacting system 104A-F includes a number of
vertically oriented co-current contactors upstream of a single
separation system. As would be apparent to those of skill in the
art, any or all of the co-current contacting systems 104A-F may be
either vertically oriented or horizontally oriented, depending on
the details of the specific implementation, and such alternate
embodiments are within the scope of this disclosure.
[0039] The gas stream 102 may be a natural gas stream from a
hydrocarbon production operation. For example, the gas stream 102
may be a flue gas stream from a power plant, or a synthesis gas
(syn-gas) stream. If the natural gas stream 102 is a syn-gas
stream, the gas stream 102 may be cooled and filtered before being
introduced into the gas processing system 100. The gas stream 102
may also be a flash gas stream taken from a flash drum in a gas
processing system itself. In addition, the gas stream 102 may he a
tail gas stream from a Claus sulfur recovery process or an
impurities stream from a regenerator. Furthermore, the gas stream
102 may be an exhaust emission from a cement plant or other
industrial plant. In this instance, CO.sub.2 may be absorbed from
excess air or from a nitrogen-containing flue gas.
[0040] The gas stream 102 may include a non-absorbing gas, such as
methane, and one or more impurities, such as an acid gas. For
example, the gas stream 102 may include CO.sub.2 or H.sub.2S. The
gas processing system 100 may convert the gas stream 102 into a
sweetened gas stream 106 by removing the acid gases.
[0041] In operation, the gas stream 102 may be flowed into a first
co-current contacting system 104A, where it is mixed with a solvent
stream 108. If the gas processing system 100 is to be used for the
removal of H.sub.2S, or other sulfur compounds, the solvent stream
108 may include an amine solution, such as monoethanol amine (MEA),
diethanol amine (DEA), or methyldiethanol amine (MDEA). Other
solvents, such as physical solvents, alkaline salts solutions, or
ionic liquids, may also be used for H.sub.2S removal. In
embodiments used for other purposes, such as dehydration or
reactions, other solvents or reactants, such as glycols, may be
used. The solvent stream 108 may include a lean solvent that has
undergone a desorption process for the removal of acid gas
impurities. For example, in the gas processing system 100 shown in
FIG. 1A, the solvent stream 108 introduced into the first
co-current contacting system 104A includes a semi-lean solvent that
is taken from a central portion of a regenerator 110. A lean
solvent stream 112 taken from the regenerator 110 may also be
directed into a final co-current contacting system 104F.
[0042] In various embodiments, the gas processing system 100
employs a series of co-current contacting systems 104A-F. In some
embodiments, as shown in FIG. 1A, the co-current contacting systems
104A-F may be arranged in a counter current configuration. Each
co-current contacting system 104A-F removes a portion of the acid
gas content from the natural gas stream 102, thereby releasing a
progressively sweetened natural gas stream in a downstream
direction. The final co-current contacting system 104F provides the
final sweetened natural gas stream 106.
[0043] Before entering the first co-current contacting system 104A,
the natural gas stream 102 may pass through an inlet separator 114.
The inlet separator 114 may be used to clean the natural gas stream
102 by filtering out impurities, such as brine and drilling fluids.
Some particle filtration may also take place. The cleaning of the
natural gas stream 102 can prevent foaming of solvent during the
acid gas treatment process.
[0044] As shown in FIG. 1A, the solvent stream 108 is flowed into
the first co-current contacting system 104A. Movement of the
semi-lean solvent stream 108 into the first co-current contacting
system 104A may be aided by a pump 116. The pump 116 may cause the
semi-lean solvent stream 108 to flow into the first co-current
contacting system 104A at a suitable pressure, for example, of
about 15 psig to about 1,500 psig.
[0045] Once inside the first co-current contacting system 104A, the
natural gas stream 102 and the solvent stream 108 move along the
longitudinal axis of the first co-current contacting system 104A.
As they travel, the solvent stream 108 interacts with the H.sub.2S,
H.sub.2O, and/or other impurities in the natural gas stream 102,
causing the H.sub.2S, H.sub.2O, and/or other impurities to
chemically attach to or be absorbed by the amine molecules. A first
partially-loaded, or "rich," gas solvent or treating solution 118A
may be flowed out of the first co-current contacting system 104A.
In addition, a first partially-sweetened natural gas stream 1204
may be flowed out of the first co-current contacting system 104A
and into a second co-current contacting system 104B. This general
arrangement may be referred to as arranging co-current contactors
in a counter current configuration.
[0046] As shown in the example illustrated in FIG. 1A, a third
co-current contacting system 104C may be provided after the second
co-current contacting system 104B, and a fourth co-current
contacting system 104B may be provided after the third co-current
contacting system 104C. In addition, a fifth co-current contacting
system 104E may be provided after the fourth co-current contacting
system 104D, and a final co-current contacting system 104F may be
provided after the fifth co-current contacting system 104E. Each of
the second, third, fourth, and fifth co-current contacting systems
104B, 104C, 104D, and 104E may generate a respective
partially-sweetened natural gas stream 120B, 1200, 120D, and 120E
In addition, each of the second, third, fourth, fifth, and final
co-current contacting systems 104B. 104C, 104D, 104E, and 104F may
generate respective partially-loaded gas treating solution 118B,
118C, 118D, 118E, and 118F. If an amine is used as the solvent
stream 108, the partially-loaded gas treating solutions 1184-F may
include rich amine solutions. In the gas processing system 100, the
second loaded gas treating solution 118B merges with the rich gas
treating solution 118A and goes through a regeneration process in
the regenerator 110.
[0047] As the progressively-sweetened natural gas streams 1204-E
are generated, the gas pressure in the gas processing system 100
will gradually decrease. As this occurs, the liquid pressure of the
progressively-richer gas treating solutions 1184-F may be
correspondingly increased. This may be accomplished by placing one
or more booster pumps (not shown) between each co-current
contacting system 104A-F to boost liquid pressure in the gas
processing system 100.
[0048] In the gas processing system 100, solvent streams may be
regenerated by flowing the partially-loaded gas treating solutions
118A and 118B through a flash drum 121. Absorbed natural gas 122
may be flashed from the partially-loaded gas treating solutions
118A and 118B within the flash drum 121, and may be flowed out of
the flash drum 121 via an overhead line 124.
[0049] The resulting rich solvent stream 126 may be flowed from the
flash drum 121 to the regenerator 110. The rich solvent stream 126
may be introduced into the regenerator 110 for desorption. The
regenerator 110 may include a stripper portion 128 including trays
or other internals (not shown). The stripper portion 128 may be
located directly above a heating portion 130. A heat source 132 may
be provided with the heating portion 130 to generate heat. The
regenerator 110 produces the regenerated, lean solvent stream 112
that is recycled for re-use in the final co-current contacting
system 104F. Stripped overhead gas from the regenerator 110, which
may include concentrated H.sub.2S (or CO.sub.2), may be flowed out
of the regenerator 110 as an overhead impurities stream 134.
[0050] The overhead impurities stream 134 may be flowed into a
condenser 135, which may cool the overhead impurities stream 134.
The resulting cooled impurities stream 138 may be flowed through a
reflux accumulator 140. The reflux accumulator 140 may separate any
remaining liquid, such as condensed water, from the impurities
stream 138. This may result in the generation of a substantially
pure acid gas stream 142, which may be flowed out of the reflux
accumulator 140 via an overhead line 144.
[0051] In some embodiments, if the initial natural gas stream 102
includes CO.sub.2, and a CO.sub.2-selective solvent stream 108 is
used, the acid gas stream 142 includes primarily CO.sub.2. The
CO.sub.2-rich acid gas stream 142 may be used as part of a miscible
EOR operation to recover oil. If the oil reservoir to be flooded
does not contain a significant amount of H.sub.2S or other sulfur
compounds. the CO.sub.2 to be used for the EOR operation may not
contain significant H.sub.2S or other sulfur compounds. However,
concentrated CO.sub.2 streams from oil and gas production
operations may be contaminated with small amounts of H.sub.2S.
Thus, it may be desirable to remove the H.sub.2S from the CO.sub.2,
unless the acid gas stream 142 is to be injected purely for
geologic sequestration.
[0052] While a gas stream 102 is discussed herein, those of skill
in the art will appreciate that generally the same principles may
be applied to any fluid stream, including with respect to
liquid-liquid contacting. Consequently, use of the phrases "gas
stream," "gas inlet," "gas outlet," etc. are to be understood as
non-limiting and may optionally be replaced with "fluid stream,"
"fluid inlet," "fluid outlet," and so forth in various embodiments
within the scope of this disclosure. Use of the phrases "gas
stream," "gas inlet," "gas outlet," etc. are for the sake of
convenience only.
[0053] In some embodiments, if the initial natural gas stream 102
includes H.sub.2S, art H.sub.2S-selective solvent stream 1.08 may
be used to capture the H.sub.2S. The H.sub.2S may then be converted
into elemental sulfur using a sulfur recovery unit (not shown). The
sulfur recovery unit may be a so-called Claus unit. Those of
ordinary skill in the art will understand that a "Claus process" is
a process that is sometimes used by the natural gas and refinery
industries to recover elemental sulfur from H.sub.2S-containing gas
streams.
[0054] In practice, the "tail gas" from the Claus process, which
may include H.sub.2S, SO.sub.2, CO.sub.2, N.sub.2, and water vapor,
can be reacted to convert the SO.sub.2 to H.sub.2S via
hydrogenation. The hydrogenated tail gas stream has a high partial
pressure, a large amount of CO.sub.2, e.g., more than 50%, and a
small amount of H.sub.2S, e.g., a few percent or less. This type of
gas stream, which is typically near atmospheric pressure, is
amenable to selective H.sub.2S removal. The recovered H.sub.2S may
be recycled to the front of the Claus unit, or may be sequestered
downstream. Alternatively, a direct oxidation of the H.sub.2S to
elemental sulfur may be performed using various processes known in
the field of gas separation.
[0055] As shown in FIG. 1A, a residual liquid stream 146 may be
flowed out of the bottom of the reflux accumulator 140. The
residual liquid stream 146 may be flowed through a reflux pump 148,
which may boost the pressure of the residual liquid stream 146 and
pump the residual liquid stream 146 into the regenerator 110. The
residual liquid stream 146 may be flowed out of the regenerator
110, for example, from the bottom of the heating portion 130 as
part of the lean solvent stream 112. Some water may be added to the
lean solvent stream 112 to balance the loss of water vapor to the
partially sweetened natural gas streams 120A-E. This water may be
added at an intake or suction of the reflux pump 148.
[0056] The lean solvent stream 112 may be at a low pressure.
Accordingly, the lean solvent stream 112 may be passed through a
pressure boosting pump 150. From the pressure boosting pump 150,
the lean solvent stream 112 may be flowed through a cooler 154. The
cooler 154 may cool the lean solvent stream 112 to ensure that the
lean solvent stream 112 will absorb acid gases effectively. The
resulting cooled lean solvent stream 156 is then used as the
solvent stream for the final co-current contacting system 104F.
[0057] In some embodiments, a solvent tank 158 is provided
proximate the final co-current contacting system 104F. The cooled
lean solvent stream 156 may be flowed from the solvent tank 158. In
other embodiments, the solvent tank 158 is off-line and provides a
reservoir for the lean solvent stream 156.
[0058] The process flow diagram of FIG. 1A is not intended to
indicate that the gas processing system 100 is to include all of
the components shown in FIG. 1A. Further, any number of additional
components may be included within the gas processing system 100,
depending on the details of the specific implementation. For
example, the gas processing system 100 may include any suitable
types of heaters, coolers, condensers, liquid pumps, gas
compressors, blowers, bypass lines, other types of separation
and/or fractionation equipment, valves, switches, controllers, and
pressure-measuring devices, temperature-measuring devices,
level-measuring devices, or flow-measuring devices, among
others.
[0059] FIG. 1B is a process flow diagram of another gas processing
system 160 that includes a co-current flow scheme. Like numbered
items are as described with respect to FIG. 1A. Operation of the
gas processing system 160 of FIG. 1B is similar to that of the gas
processing system 100 of FIG. 1A. However, in the gas processing
system 160, the first co-current contacting system 104A receives
the partially-loaded gas treating solution 118B from the second
co-current contacting system 104B. Therefore, the gas processing
system 160 does not include the semi-lean solvent stream 108. In
this example, the series of co-current contacting systems 104A-F
acts like a separation column, for example, wherein each stage
corresponds to a packed stage.
[0060] Because the partially-loaded gas treating solution 118B
received by the first co-current contacting system 104A in FIG. 1B
has already been processed through the second co-current contacting
system 104B, the partially-loaded gas treating solution 118B may be
very rich. For this reason, it may be desirable to provide some
level of intermediate processing of the partially-loaded gas
treating solution 118B.
[0061] Alternatively, a semi-lean liquid stream could be taken from
other sweetening operations in the gas processing system 160 and
used, at least in part, as an amine solution for the first or
second co-current contacting system 104A or 104B. In this respect,
there are situations in which a single type of solvent is used for
more than one service in the gas processing system 160. This is
referred to as integrated gas treatment. For example, MDEA may be
used both for high-pressure, H.sub.2S-selective acid gas removal,
as well as in a Claus tail gas treating (TGT) process. The rich
amine stream from the TGT process is not heavily loaded with
H.sub.2S and CO.sub.2, owing to the low pressure of the process.
Thus, in some embodiments, the rich amine stream from the TGT
process is used as a semi-lean stream for the first or second
co-current contacting system 104A or 104B. The semi-lean stream
(not shown) may be pumped to a suitable pressure and injected into
the first or second co-current contacting system 104A or 104B,
possibly along with the partially-loaded gas treating solution from
the succeeding co-current contacting system.
[0062] Further, in the gas processing system 160 of FIG. 1B, the
first partially-loaded treating solution 118A is flowed through a
heat exchanger 162 after being flowed through the flash drum 121.
Within the heat exchanger 162, the temperature of the first
partially-loaded treating solution 118A is increased via heat
exchange with the lean solvent 112 taken from the regenerator 110.
This serves to heat the first partially-loaded treating solution
118A before introduction into the regenerator 110, while cooling
the lean solvent stream 112.
[0063] The process flow diagram of FIG. 1B is not intended to
indicate that the gas processing system 160 is to include all of
the components shown in FIG. 1B. Further, any number of additional
components may be included within the gas processing system 160,
depending on the details of the specific implementation.
[0064] FIG. 2 is a schematic diagram of a co-current contacting
system 200, e.g., any one of the co-current contacting systems
104A-F of FIG. 1. The components of FIG. 2 may be the substantially
the same as the corresponding components of FIG. 1 except as
otherwise noted. The co-current contacting system 200 has four
contacting units 202a-202d separately supplied by a header 204 for
a natural gas stream 102. The contacting units 202a-202d are
separately supplied by a header carrying a lean solvent stream 206,
e.g., a semi-lean solvent stream 108 or any of the partially-loaded
gas treating solutions 118A-F, and received proximate to a first
end of each each contacting unit 202a-202d. Each contacting unit
202a-202d has an inlet nozzle 208a-208d (respectively) for
atomizing and/or dividing the solvent into a large number of small
droplets and introducing the lean solvent stream 206. Atomizing the
lean solvent stream 206 increases the surface area available for
contact with the natural gas stream 102 and decreases the distances
required for diffusion of acid gas components in both the vapor and
liquid phases. Each contacting unit 202a-202d has a recycle gas
inlet 210a-210d supplied by gas collected and returned from a seal
pot or liquid boot 212a-212d. As depicted, each recycle gas inlet
210a-210d may include a swirl vane or equivalent structure to
assist in separation. The seal pot or liquid boot 212a-212d may
provide residence time for process control and may seal the
contacting units 202a-202d to prevent gas bypass. Each contacting
unit 202a-202d has a treated gas outlet 214a-214d and a rich
solvent outlet 216a-216d. The treated gas outlets 214a-214d are
depicted as comprising vortex tube finders, but alternate
embodiments are well known in the art. Treated gas exiting the
contacting units 202a-202d via the treated gas outlets 214a-214d
may be combined and passed as the sweetened gas stream 106, while
rich solvent exiting the contacting units 202a-202d via the rich
solvent outlets 216a-216d may be combined and passed as the rich
solvent stream 136.
[0065] In operation, each contacting unit 202a-202d receives a
natural gas stream 102 at an inlet section 220a-220d, where the
inlet nozzles 208a-208d atomize a lean solvent stream 206 and
expose it to the natural gas stream 102, creating a mixed,
two-phase flow or combined stream (not depicted). The mixed,
two-phase flow or combined stream passes through a mass transfer
section 222 where absorption occurs. The mass transfer section 222
may comprise a tubular body having a substantially empty bore
having one or more surface features, e.g., a hydrophobic surface, a
superhydrophobic surface, a raised surface, a recessed surface, or
any combination thereof, along an inner surface of the mass
transfer section 222. A separation section 224 follows the mass
transfer section. In the separation section 224, entrained liquid
droplets are removed from the gas stream, e.g., using a cyclone
inducing element, resulting in an at least partially dehydrated
and/or decontaminated treated gas stream. In some embodiments, the
inlet section 220 and the mass transfer section 222 may
collectively be referred to as a contacting section. The length of
the contacting section may be determined based on the residence
time required to obtain a predetermined decontamination and/or
dehydration level for the natural gas stream 102, e.g., in view of
the intended flow rate, pressure drop, etc. The treated gas stream
exits the contacting units 202a-202d through the outlet section
226. The contacting units 202a-202d may operate at about 400 psig
to about 1,200 psig, or higher. Because the contacting units
202a-202d must be individually constructed so as to tolerate these
pressures, weight and/or footprint increases linearly as the number
of contacting units 202a-202d is increased.
[0066] As co-current contactors become more compact, both in length
and diameter, it is important to ensure as much solvent as possible
reacts in the increasingly shortened mixing and/or mass transfer
section. The H.sub.2S reaction is instantaneous relative to the
CO.sub.2 reactions, lowering the residence time, i.e., the contact
time between the vapor and liquid phases, will result in less
CO.sub.2 being absorbed into the solvent. The design of the
co-current contacting systems 104A-F enhances selective H.sub.2S
removal due to the short contact time inherent in the equipment
design. Disclosed herein are techniques for inhibiting or impeding
an amount of liquid from propagating along a wall of the mass
transfer section using a surface feature. By inhibiting or impeding
liquid propagation along a wall of the mass transfer section, a
comparatively greater amount of solvent is retained in the interior
volume of the mass transfer section and, consequently, remains
available for reaction.
[0067] FIG. 3 is a. side view of an embodiment of a single stage
multiple co-current contactor bundle configuration 300. The
components of FIG. 3 are substantially the same as the
corresponding components of FIG. 2 except as otherwise noted. The
single stage multiple co-current contactor bundle configuration 300
is generally contained within a vessel 302 which may form a unitary
(single and/or common) pressure boundary for the compact contacting
occurring therein, The vessel 302 generally contains a single stage
bundle of substantially parallel separation units or compact
contactors comprising contacting units 202a-202n, also referred to
herein as separation units. Those of skill in the art will
understand that the number of contacting units 202a-202n in the
bundle of compact contactors may be optionally selected based on
the desired design characteristics, including desired flow rate,
separation unit diameter, etc., and could number from anywhere
between one to 300 or more units. The use of the letter
nomenclature(i.e., `a`, `b`, `n`, etc.) in conjunction with the
numerical reference characters is for ease of reference only and is
not limiting. For example, those of skill in the art will
understand that an illustrated set of contacting units 202a-202n
may, in various embodiments, comprise two, four, five, twenty, or
several hundred contacting units. The vessel 302 comprises an inlet
tubesheet 304 having inlet nozzles 208a-208n in the inlet section
220. The inlet section 220 is configured to receive the natural gas
stream 102 in a common inlet plenum through which the natural gas
stream 102 may be distributed substantially equally across the
contacting units 202a-202n. The contacting units 202a-202n may be
of a suitable size depending on the design requirements. For
example, the contacting units 202a-202n may have an individual
diameter from about 2 inches (in) (about 5 centimeters (cm)) to
about 24 in (about 61 cm), or any range there between. The inlet
tubesheet 304 is configured to receive the lean solvent stream 206
and pass the lean solvent stream 206 to the inlet nozzles
208a-208n, where the lean solvent stream 206 may be atomized. In
some embodiments, the lean solvent stream 206 originates from a
glycol supply system (not depicted) and the lean solvent stream 206
comprises glycol. The inlet nozzles 208a-208n may serve to entrain
the atomized solvent stream in the natural gas stream 102, and the
mixed stream of atomized solvent and natural gas may be passed to
the mass transfer section 222 where absorption occurs. Each
contacting unit 202a-202n has a recycle gas inlet 210a-210n
supplied by recycle gas collected and returned, e.g., from a common
boot 316. The boot 316 may be optionally included in low liquid
rate applications to improve liquid rate flow control. As depicted,
the boot 316 may have an internal vortex breaker 317 or other
appropriate internals. For ease of viewing, the recycle gas supply
lines for each of the recycle gas inlets 210a-210n are not
depicted. As will be understood by those of skill in the art, the
recycle gas inlets 210a-210n are optional, and recycle gas may
additionally or alternatively be sent downstream in other
embodiments. Rich solvent exiting the contacting units 202a-202n
via the rich solvent outlets 306a-306n may drain into a common
liquid degassing section or common contaminated liquid collection
plenum 312. The plenum 312 may provide sufficient residence time
for desired degasing, may reduce liquid surges coming with the
natural gas stream 102, and may provide liquid seal to a cyclonic
separation occurring in a contacting section of the separation
device 202a-202n. The residence time provided by the plenum 312 can
vary from 5 seconds to 5 minutes, depending on the operation of the
process, or from 30 seconds to 1 minute in various embodiments. The
vessel 302 contains a mist eliminator 314, e.g., a wire mesh, vane
pack plates, baffles, or other internal devices to reduce liquid
droplet carry over from degassing gas leaving the liquid phase of
rich solvent in the plenum 312. The mist eliminator 314 may also
serve as a momentum breaker for the rich solvent liquid exiting the
separation device 202a-202n to minimize aeration of the liquid. In
embodiments installed in offshore facilities or floating facilities
or otherwise subject to motion, the mist eliminator 314 may
mitigate wave motion effects in the bottom portion of the vessel
302. Each contacting unit 202a-202n has a treated gas outlet
214a-214n and a rich solvent outlet 306a-306n. The vessel 302 has a
vent 318 for expelling degassing gas, e.g., gas degassed from rich
solvent collected in the plenum 312 that may be fed upstream or
downstream of the multiple co-current contacting unit, depending on
the process configuration. The treated gas outlets 214a-214n couple
to an outlet tubesheet 310. The treated gas exiting the contacting
units 202a-202n via the treated gas outlets 214a-214n may be
referred to as the dehydrated and/or decontaminated natural gas
stream 102. The vessel 302 also contains level control ports 320a
and 320b for coupling a level control system (not depicted) and
controlling the amount of rich solvent 326, e.g., a semi-lean
solvent stream 108 or any of the partially-loaded gas treating
solutions 118A-F, exiting the boot 316. Rich solvent 326 exiting
the boot 316 may be sent to a regeneration system for treatment or
combined with streams in other processes.
[0068] FIG. 4 is a schematic diagram of a co-current contactor 400,
e.g., any of the co-current contacting units 202a-202d of FIGS.
2-3, having a coalescing section 402. The components of FIG. 4 are
substantially the same as the corresponding components of FIGS. 2-3
except as otherwise noted, The co-current contactor 400 includes
inlet section 220 and coalescing section 402 comprising one or more
coalescer(s) 404, e.g., an electrostatic coalescer, a mechanical
coalescer, etc. Suitable electrostatic coalescers are well known in
the art and are commercially available from a variety of vendors.
Suitable mechanical coalescers are well known in the art, and
include baffles, spiral baffles or swirl vanes, plates, plate
packs, gauze, wire mesh, random or structured packing, fiber media,
etc. Suitable mechanical coalescer materials include austenitic
steel, aluminum, copper, plastic, polytetrafluoroethylene (PTFE) or
PTFE coated materials, polyvinylidene fluoride or polyvinylidene
difluoride (PVDF), etc. Coalescer material selection decisions may
consider the wettability of the material with the dispersed fluid.
Coalescing media selection decisions may consider the desired
coalescing efficiency with consideration to fouling and/or solids
present in the system. In some embodiments, a pre-coalescer (not
pictured) may be included, e.g., a pre-coalescer inline
electrostatic coalescence device disposed immediately after the
mass transfer section 222 and prior to a separation section
224.
[0069] In operation, the solvent entering the coalescing section
402 may have an average droplet size in a range from a first
average droplet size to a second average droplet size, wherein the
first average droplet size is any of: less than about 1 micrometer
(.mu.m), about 1 .mu.m, about 5 .mu.m, about 10 .mu.m, about 25
.mu.m, about 50 .mu.m, about 75 .mu.m, about 100 .mu.m, about 250
.mu.m, about 500 .mu.m, or about 750 .mu.m, and wherein the second
average droplet size is any of: about 2 .mu.m, about 5 .mu.m, about
10 .mu.m, about 25 .mu.m, about 50 .mu.m, about 75 .mu.m, about 100
.mu.m, about 250 .mu.m, about 500 .mu.m, about 750 .mu.m, or about
1000 .mu.m. After passing through the one or more coalescer(s) 404,
the solvent may have an average droplet size in a range from a
first average droplet size to a second droplet size, wherein the
first average droplet size is any of: about 1 .mu.m, about 5 .mu.m,
about 10 .mu.m, about 25 .mu.m, about 50 .mu.m, about 75 .mu.m,
about 100 .mu.m, about 250 .mu.m, about 500 .mu.m, about 750 .mu.m,
about 1000 .mu.m, about 2500 .mu.m, about 5000 .mu.m, about 7500
.mu.m, or about 9000 .mu.m, and wherein the second average droplet
size is any of: about 2 .mu.m, about 5 .mu.m, about 10 .mu.m, about
25 .mu.m, about 50 .mu.m, about 75 .mu.m, about 100 .mu.m, about
250 .mu.m, about 500 .mu.m, about 750 .mu.m, about 1000 .mu.m,
about 2500 .mu.m, about 5000 .mu.m, about 7500 .mu.m, or about
10000 .mu.m. In embodiments with a pre-coalescer, after passing
through the pre-coalescer, the solvent may have an average droplet
size in a range from a first average droplet size to a second
droplet size, wherein the first average droplet size is any of:
about 1 .mu.m, about 5 .mu.m, about 10 .mu.m, about 25 .mu.m, about
50 .mu.m, about 75 .mu.m, about 100 .mu.m, about 250 .mu.m, about
500 .mu.m, about 750 .mu.m, about 1000 .mu.m, about 2500 .mu.m,
about 5000 .mu.m, about 7500 .mu.m, or about 9000 .mu.m, and
wherein the second average droplet size is any of: about 2 .mu.m,
about 5 .mu.m, about 10 .mu.m, about 25 .mu.m, about 50 .mu.m,
about 75 .mu.m, about 100 .mu.m, about 250 .mu.m, about 500 .mu.m,
about 750 .mu.m, about 1000 .mu.m, about 2500 .mu.m, about 5000
.mu.m, about 7500 .mu.m, or about 10000 .mu.m.
[0070] The average residence time in the coalescer for a gas-liquid
contacting system may be in a range from a first average residence
time to a second average residence time, wherein the first average
residence tune is any of: less than about 0.01 seconds (s), about
0.01 s, about 0.1 s, or about 0.2 s, and wherein the second average
residence time is any of: about 0.01 s, about 0.1 s, or about 0.2
s. The average residence time in the coalescer for a liquid-liquid
contacting system may be in a range from a first average residence
time to a second average residence time, wherein the first average
residence time is any of: less than about 0.1 seconds (s), about 1
s, about 5 s, or about 10 s, and wherein the second average
residence time is any of: about 1 s, about 5 s, about 10 s, or
about 15 s.
[0071] While it will be apparent that the invention herein
described is well calculated to achieve the benefits and advantages
set forth above, it will be appreciated that the invention is
susceptible to modification, variation and change without departing
from the spirit thereof.
* * * * *