U.S. patent application number 17/394230 was filed with the patent office on 2022-02-10 for gas compression process.
This patent application is currently assigned to Bell Engineering, Inc.. The applicant listed for this patent is Bell Engineering, Inc.. Invention is credited to Tyler Briggs, Robert Richardson.
Application Number | 20220042741 17/394230 |
Document ID | / |
Family ID | 1000005812723 |
Filed Date | 2022-02-10 |
United States Patent
Application |
20220042741 |
Kind Code |
A1 |
Richardson; Robert ; et
al. |
February 10, 2022 |
Gas Compression Process
Abstract
Example embodiments for a method for compressing gas into a
liquified gas using a plurality of pairs of liquid gas displacers
in parallel moving a working fluid between each pair of displacers
to pressurize the gas, arranging sets of the parallel liquid gas
displacers in a series to raise the pressure, directly cooling the
gas at each displacer pair, and finally condensing the gas using a
coolant, collecting the liquified gas, and pressurizing the
liquified gas for use in a pipeline.
Inventors: |
Richardson; Robert;
(Beaumont, TX) ; Briggs; Tyler; (Beaumont,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bell Engineering, Inc. |
Orange |
TX |
US |
|
|
Assignee: |
Bell Engineering, Inc.
Orange
TX
|
Family ID: |
1000005812723 |
Appl. No.: |
17/394230 |
Filed: |
August 4, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
63061049 |
Aug 4, 2020 |
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|
63061059 |
Aug 4, 2020 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25J 1/0052 20130101;
F25J 1/0027 20130101; F25J 2230/30 20130101 |
International
Class: |
F25J 1/00 20060101
F25J001/00 |
Claims
1. A method for compressing gas comprising: compressing a gas at a
first stage compressor to create a first compressed gas; cooling
the first compressed gas; compressing the first compressed gas at a
second stage compressor to create a second compressed gas; cooling
the second compressed gas; compressing the second compressed gas at
a third stage compressor to create a third compressed gas; cooling
the third compressed gas; compressing the third compressed gas at a
fourth stage compressor to create a fourth compressed gas; cooling
the fourth compressed gas; condensing the fourth compressed gas
into a liquified gas; collecting the liquified gas; pressuring the
liquified gas; delivering the liquified gas into a gas line.
2. The method for compressing gas of claim 1 wherein the gas is
CO.sub.2.
3. The method for compressing gas of claim 1 wherein the first
stage compressor is a plurality of pairs of displacement vessels
each pair having a dedicated pump.
4. The method for compressing gas of claim 1 wherein the second
stage compressor is a plurality of pairs of displacement vessels
each pair having a dedicated pump.
5. The method for compressing gas of claim 1 wherein the third
stage compressor is a plurality of pairs of displacement vessels
each pair having a dedicated pump.
6. The method for compressing gas of claim 1 wherein the fourth
stage compressor is a plurality of pairs of displacement vessels
each pair having a dedicated pump.
7. The method for compressing gas of claim 1 wherein the first
stage compressor includes a plurality of centrifugal pumps.
8. The method for compressing gas of claim 1 wherein the cooling of
the first gas includes using a plurality of discharge coolers.
9. The method for compressing gas of claim 1 wherein the cooling of
the second gas includes using a plurality of discharge coolers.
10. The method for compressing gas of claim 1 wherein the cooling
of the third gas includes using a plurality of discharge
coolers.
11. The method for compressing gas of claim 1 wherein the cooling
of the fourth gas includes using a plurality of discharge
coolers.
12. The method for compressing gas of claim 1 wherein the
condensing of the fourth gas includes using a plurality of chillers
to chill water that is circulated with the gas to condense it.
13. The method for compressing gas of claim 1 wherein the
compressing of the liquified gas includes using a plurality of
pumps to increase the pressure.
14. A method for liquifying carbon dioxide comprising: Receiving
carbon dioxide gas from a source; Compressing the carbon dioxide in
a plurality of pairs of displacer vessels placed in a parallel
configuration to form a stage; Cooling the gas using a plurality of
discharge coolers, one for each pair of displacer vessels;
Compressing the carbon dioxide using a series of stages in a linear
configuration, wherein the pressure of the carbon dioxide is
increased and cooled with each stage until the carbon dioxide
becomes a liquid; and Pumping the liquid carbon dioxide to a
pipeline.
15. The method for liquifying carbon dioxide of claim 14 wherein
the pumps for each of the plurality of pairs of displacer vessels
is a centrifugal pump.
16. The method for liquifying carbon dioxide of claim 14 wherein
the pumps for each of the plurality of pairs of displacer vessels
is a vertical wet pit mixed pump.
17. The method for liquifying carbon dioxide of claim 14 further
comprising cooling the gas using a plurality of chillers to chill a
coolant fluid and then circulating the coolant fluid with the
gas.
18. The method for liquifying carbon dioxide of claim 14 further
comprising condensing the gas to liquified gas using chilled water
in a plurality of displacers.
19. The method for liquifying carbon dioxide of claim 18 further
comprising pressurizing the liquified gas using a plurality of
pumps.
20. A method for gas comprising: receiving gas from a source;
compressing the gas a plurality of pairs of displacer vessels
placed in a parallel configuration to form a stage, wherein a
working fluid is pumped alternatively into the pairs of displacer
vessels to pressurize the gas; cooling the gas using a plurality of
discharge coolers, one for each pair of displacer vessels;
compressing the gas using a series of stages in a linear
configuration, wherein the pressure of the carbon dioxide is
increased and cooled with each stage until the carbon dioxide
becomes a liquid; chilling a coolant and then circulating that
coolant within a final stage to produce liquified gas; collecting
the liquified gas; pressurizing the liquified gas using a plurality
of pumps; and pumping the liquid carbon dioxide to a pipeline.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 63/061,049, filed Aug. 4, 2020 and U.S. Provisional
Application No. 63/061,059, filed Aug. 4, 2020.
BACKGROUND OF THE INVENTION
[0002] To summarize the technology historically utilized in gas
compression processes involving low first stage suction pressures
would be using a reciprocating or centrifugal compressor to
increase the pressure in stages. The pressure increase per stage is
limited by the heat of compression temperature increase with
material of construction limits of around 225 F. Scrubber vessels
are located prior to the inlet of each stage to prevent liquids
from entering the compressor. Incompressible liquids can be very
harmful to mechanical compressors. The heat of compression is
removed from the gas after each stage of compression, usually by an
air-cooled exchanger. Some condensation of liquids is common during
the cooling of the vapor, so a two-phase separator is located after
the cooler to separate condensed liquids. The compression of carbon
dioxide, CO.sub.2, to pipeline pressures elevates the gas above
critical pressure, where the fluid is compressed/pumped to final
pressure.
SUMMARY OF EXAMPLE EMBODIMENTS
[0003] An example embodiment may include a method for compressing
gas comprising compressing a gas at a first stage compressor to
create a first compressed gas, cooling the first compressed gas,
compressing the first compressed gas at a second stage compressor
to create a second compressed gas, cooling the second compressed
gas, compressing the second compressed gas at a third stage
compressor to create a third compressed gas, cooling the third
compressed gas, compressing the third compressed gas at a fourth
stage compressor to create a fourth compressed gas, cooling the
fourth compressed gas, condensing the fourth compressed gas into a
liquified gas, collecting the liquified gas, pressuring the
liquified gas, delivering the liquified gas into a gas line.
[0004] A variation of the example embodiment may include the gas
being CO.sub.2. The first stage compressor may be a plurality of
pairs of displacement vessels each pair having a dedicated pump.
The second stage compressor may be a plurality of pairs of
displacement vessels each pair having a dedicated pump. The third
stage compressor may be a plurality of pairs of displacement
vessels each pair having a dedicated pump. The fourth stage
compressor may be a plurality of pairs of displacement vessels each
pair having a dedicated pump. The first stage compressor may
include a plurality of centrifugal pumps. The cooling of the first
gas may include using a plurality of discharge coolers. The cooling
of the second gas may include using a plurality of discharge
coolers. The cooling of the third gas may include using a plurality
of discharge coolers. The cooling of the fourth gas may include
using a plurality of discharge coolers. The condensing of the
fourth gas may include using a plurality of chillers to chill water
that is circulated with the gas to condense it. The compressing of
the liquified gas may include using a plurality of pumps to
increase the pressure.
[0005] An example embodiment may include a method for liquifying
carbon dioxide comprising receiving carbon dioxide gas from a
source, compressing the carbon dioxide in a plurality of pairs of
displacer vessels placed in a parallel configuration to form a
stage, cooling the gas using a plurality of discharge coolers, one
for each pair of displacer vessels, compressing the carbon dioxide
using a series of stages in a linear configuration, wherein the
pressure of the carbon dioxide is increased and cooled with each
stage until the carbon dioxide becomes a liquid, and pumping the
liquid carbon dioxide to a pipeline.
[0006] An example variation may include the pumps for each of the
plurality of pairs of displacer vessels being a centrifugal pump.
The pumps for each of the plurality of pairs of displacer vessels
may be a vertical wet pit mixed pump. Cooling the gas may include
using a plurality of chillers to chill a coolant fluid and then
circulating the coolant fluid with the gas. Condensing the gas to
liquified gas may include using chilled water in a plurality of
displacers. Pressurizing the liquified gas may include using a
plurality of pumps.
[0007] An example embodiment may include a method for gas
comprising receiving gas from a source, compressing the gas a
plurality of pairs of displacer vessels placed in a parallel
configuration to form a stage, wherein a working fluid is pumped
alternatively into the pairs of displacer vessels to pressurize the
gas, cooling the gas using a plurality of discharge coolers, one
for each pair of displacer vessels, compressing the gas using a
series of stages in a linear configuration, wherein the pressure of
the carbon dioxide is increased and cooled with each stage until
the carbon dioxide becomes a liquid, chilling a coolant and then
circulating that coolant within a final stage to produce liquified
gas, collecting the liquified gas, pressurizing the liquified gas
using a plurality of pumps, and pumping the liquid carbon dioxide
to a pipeline.
[0008] An example embodiment may include an apparatus for
compressing the nearly pure CO.sub.2 byproduct stream from ethanol
production facilities. Instead of using a mechanical compressor to
compress the gas to 2,200 psig pipeline pressures, the near 0 psig
CO.sub.2 would be drawn into a liquid filled vessel by pumping the
liquid from the vessel to an adjacent vessel. Once the vessel is
emptied of liquid and filled with CO.sub.2, valving would reverse
the flow of the liquid and would begin refilling the vessel with
liquid. Either check valves or actuated valves would prevent the
CO.sub.2 gas from backflowing into the inlet piping. Instead, the
gas volume would increase with the rising liquid level resulting in
an increase in pressure inside the vessel. Flow of the compressed
gas would be routed to a higher-pressure discharge header by the
rising liquid displacing the liquid from the vessel into the
discharge header. Once the liquid filling sequence is completed,
the cycle would begin again with the emptying of the liquid from
the vessel, and the drawing in of more low-pressure CO.sub.2. For
efficiency, the adjacent vessel that liquid is pumped into and out
of is also used to draw in CO.sub.2, compress and displace the
compressed vapor into the discharge header. The two vessels working
together draw a continuous stream of low-pressure gas in for
compression and displacement. Air cooled exchangers will cool the
compressed gas after each stage to optimize compression by
increasing the density of the gas. Although, the gas is partially
cooled by heating the displacement liquid. A heat exchanger on the
pump discharge cools the displacement liquid. Once the CO.sub.2 is
compressed above 550 psig it can be condensed to a liquid. A
multi-stage centrifugal pump or progressive pump is used to pump
the liquid CO.sub.2 to the required pipeline pressure of 2,200
psig. Refrigeration can be used to condense the CO.sub.2 at lower
pressures, or the gas can be increased to a point where air cooled
exchangers can be used to condense the gas. Operating conditions
and atmospheric temperatures determine the most economical
operation.
[0009] An example embodiment may include a method for recompressing
the CO.sub.2 used in enhanced oil recovery (EOR). Oil fields using
EOR are most productive with low operating pressure recompression
headers operating less than 50 psig. Recompressed CO.sub.2 is
returned to the oilfield and reinjected at pressures above 2,000
psig. Instead of using a mechanical compressor to compress the gas
to 2,200 psig pipeline pressures, the near less than 100 psig
CO.sub.2 would be drawn into a liquid filled vessel by pumping the
liquid from the vessel to an adjacent vessel. Once the vessel is
emptied of liquid and filled with CO.sub.2, valving would reverse
the flow of the liquid and would begin refilling the vessel with
liquid. Either check valves or actuated valves would prevent the
CO.sub.2 gas from backflowing into the inlet piping. Instead, the
gas volume would increase with the rising liquid level resulting in
an increase in pressure inside the vessel. Flow of the compressed
gas would be routed to a higher-pressure discharge header by the
rising liquid displacing the liquid from the vessel into the
discharge header. Once the liquid filling sequence is completed,
the cycle would begin again with the emptying of the liquid from
the vessel, and the drawing in of more low-pressure CO.sub.2. For
efficiency, the adjacent vessel that liquid is pumped into and out
of is also used to draw in CO.sub.2, compress and displace the
compressed vapor into the discharge header. The two vessels working
together draw a continuous stream of low-pressure gas in for
compression and displacement. The gas is usually 85-95% CO.sub.2.
The balance of the composition is the full spectrum of volatile
hydrocarbons found in oilfield gas. Air cooled exchangers will cool
the compressed gas after each stage to optimize compression by
increasing the density of the gas. Some hydrocarbons will be
condensed as the gas pressure increases and are removed in a
separator downstream of the coolers. Although, the gas is partially
cooled by heating the displacement liquid. A heat exchanger on the
pump discharge cools the displacement liquid. Once the CO.sub.2 is
compressed above 550 psig it can be condensed to a liquid. Some
non-condensables will pass through the condenser and can be vented
to a fuel-gas header or an alternative purpose in the processing
facility. A multi-stage centrifugal pump or progressive pump is
used to pump the liquid CO.sub.2 to the required pipeline pressure
of 2,200 psig. Refrigeration can be used to condense the CO.sub.2
at lower pressures, or the gas can be increased to a point where
air cooled exchangers can be used to condense the gas. Operating
conditions and atmospheric temperatures determine the most
economical operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a thorough understanding of the present invention,
reference is made to the following detailed description of the
preferred embodiments, taken in conjunction with the accompanying
drawings in which reference numbers designate like or similar
elements throughout the several figures of the drawing.
Briefly:
[0011] FIG. 1 depicts an example embodiment of a flow diagram of a
liquid-piston CO.sub.2 compression process, first stage.
[0012] FIG. 2 depicts an example embodiment of a flow diagram of a
liquid-piston CO.sub.2 compression process, second stage.
[0013] FIG. 3 depicts an example embodiment of a flow diagram of a
liquid-piston CO.sub.2 compression process, third stage.
[0014] FIG. 4 depicts an example embodiment of a flow diagram of a
liquid-piston CO.sub.2 compression process, fourth stage.
[0015] FIG. 5 depicts an example embodiment of a flow diagram of a
liquid-piston CO.sub.2 compression process, condensation and final
pressure pumping.
[0016] FIG. 6 depicts an example embodiment of a flow diagram of a
liquid-piston CO.sub.2 compression process, process flow diagram
with material balance.
DETAILED DESCRIPTION OF EXAMPLES OF THE INVENTION
[0017] In the following description, certain terms have been used
for brevity, clarity, and examples. No unnecessary limitations are
to be implied therefrom and such terms are used for descriptive
purposes only and are intended to be broadly construed. The
different apparatus, systems and method steps described herein may
be used alone or in combination with other apparatus, systems and
method steps. It is to be expected that various equivalents,
alternatives, and modifications are possible within the scope of
the appended claims.
[0018] The general process flow takes low pressure CO.sub.2 gas
from the low-pressure source through the various equipment in the
compression technology. The fluid is compressed, and the heat of
compression removed to increase compression efficiency. The fluid
is condensed at high pressure and pumped to a pipeline for
transport.
[0019] The example embodiments fit an anthropogenic CO.sub.2 source
and will have a standard set of design elements, described herein
is designed to accommodate a range of operating conditions to
optimize the compression of CO.sub.2 produced to pipeline transport
pressures. The CO.sub.2 can then be used in the energy or
manufacturing industries. Anthropogenic CO.sub.2 is produced from
many different processes such as Transportation, Electricity
Production, Industrial Processes, Commercial and Residential
Heating, and Agriculture. The process is more economical on larger
scales, as such is most suitable for Electricity Production and
Industrial Processes such as ethanol production facilities.
[0020] An example embodiment is disclosed in FIG. 1 as the first
stage of the liquid piston CO.sub.2 compression process 500.
CO.sub.2 flow 502 enters one of the displacer vessels, 503(a-e),
504(a-e) where liquid from one of the pumps 505(a-e) moves liquid
into the displacer, displacing the CO.sub.2 out of the displacer
and to one of the gas coolers 501(a-e). Cooled gas leaves the gas
coolers 501(a-e) and proceeds to the second stage through header
506. Pumps 505(a-e) are shown as vertical pumps, but they can be
any type of pump, including centrifugal pumps. The displacer
vessels 503(a-e) rely on a working fluid to compress the gas, in
this case CO.sub.2. Any pump that can pump a working fluid, such as
water in this example embodiment, can be used as a pump 505(a-e).
Working fluids could include water, water glycol mix, hydraulic
fluid, produced oil, hydrocarbon by-product, produced water, or any
other suitable working fluid.
[0021] The displacer vessels 503(a-e) and 504(a-e) may be
displacement tanks that can be either horizontal or vertical in
orientation. The displacer vessels 503(a-e) and 504(a-e) are sized
based on the frequency of valve cycling desired. Displacer vessels
503(a-e) and 504(a-e) sized to fill in approximately 30 seconds
would experience about one million valve cycles per year. Valves
and actuators with two million cycle life estimates would provide
two years of operation without anticipated valve maintenance.
[0022] The liquid displacer pumps 505(a-e) are centrifugal. The
pumps 505(a-e) will operate along their design operating curve
between the beginning and ending pressure of the displacer vessels
503(a-e) and 504(a-e). For the rated gas flow rate of the unit, the
pumps 505(a-e) must displace the corresponding volume of liquid to
match the actual volume of the gas flowed during the compression
cycle. The density of the gas progressively increases during the
compression step as the displacer pressure increases.
[0023] The pumping or compressing cycle of the liquid piston unit
is controlled with low liquid level switches on each volume
displacer tank. The on-off valves are piped so that the pump
discharge can be routed to either tank. Likewise, the pump suction
can be lined up with either tank. When the liquid level switch of
the tank being emptied activates, the valves switch so that the
tank that was being emptied now becomes the tank being filled.
[0024] Inlet gas is routed to the top of each of the displacer
vessels 503(a-e) and 504(a-e). A check valve at the inlet of each
displacer vessels 503(a-e) and 504(a-e) only allows gas to enter
but not exit. The dropping liquid in the displacer vessels 503(a-e)
and 504(a-e) being emptied draws gas into the tank. The rising
liquid level in the displacer vessels 503(a-e) and 504(a-e) being
filled displaces gas from each of the displacer vessels 503(a-e)
and 504(a-e), but the check valve on the inlet header prevents
back-flow of the gas. Instead the gas exits into the discharge
header. The discharge header also has check valves where the header
attaches to each pair of displacer vessels 503(a-e) and 504(a-e).
However, the check valves only allow gas to exit the displacer
vessels 503(a-e) and 504(a-e) and flow into the discharge header.
If too much gas is drawn through the displacer vessels 503(a-e) and
504(a-e), the suction pressure will drop below the desired pressure
set point. To control the suction pressure, a valve allows some gas
from the discharge header to flow back to the inlet header.
[0025] Higher differential pressures can be achieved if displacer
vessels 503(a-e) and 504(a-e) are linked in series. Multiple stages
of compression are more efficient than one large pressure
differential stage. As the gas compresses, less and less volume of
liquid is required to displace the same SCFM flow rate of gas. The
denser gas that requires less liquid displacement requires less
pumping horsepower. Interstage pressures are maintained and
balanced with feathering control valves on the gas header from the
discharge of a stage back to its suction. Heat of compression is
removed with an appropriately sized heat exchanger(s), in this
example gas coolers 501(a-e).
[0026] An example embodiment is disclosed in FIG. 2 as the second
stage of the liquid piston CO.sub.2 compression process 510.
CO.sub.2 flow 506 enters one of the displacer vessels, 513(a-e),
514(a-e) where liquid from one of the pumps 515(a-e) pumps liquid
into the displacer, displacing the CO.sub.2 out of the displacer
and to one of the gas coolers, 511(a-e). Cooled gas leaves the
cooler and proceeds to the second stage through header 516.
[0027] An example embodiment is disclosed in FIG. 3 as the third
stage of the liquid piston CO.sub.2 compression process 520.
CO.sub.2 flow 516 enters one of the displacer vessels, 523(a-e),
524(a-e) where liquid from one of the pumps 525(a-e) pumps liquid
into the displacer, displacing the CO.sub.2 out of the displacer
and to one of the gas coolers, 521(a-e). Cooled gas leaves the
cooler and proceeds to the second stage through header 526.
[0028] An example embodiment is disclosed in FIG. 4 as the fourth
stage of the liquid piston CO.sub.2 compression process 530.
CO.sub.2 flow 526 enters one of the displacer vessels, 533(a-e),
534(a-e) where liquid from one of the pumps 535(a-e) pumps liquid
into the displacer, displacing the CO.sub.2 out of the displacer
and to one of the gas coolers, 531(a-e). Cooled gas leaves the
cooler and proceeds to the second stage through header 536.
[0029] An example embodiment is disclosed in FIG. 5 as the fourth
stage of the liquid piston CO.sub.2 compression process 540.
CO.sub.2 flow 536 enters one of the vapor condensers, 542(a-e),
where CO.sub.2 is condensed and collected in one of the liquid
receivers, 543(a-e). Vapor condensers 542(a-e) is a heat exchanger.
Vapor entering via CO.sub.2 flow 536 is cooled by vapor condensers
542(a-e), utilizing cooled water recirculating via pumps 545(a-h)
from chillers 541(a-h). As the vapor cools it condenses into
liquid, that liquefied gas is then collected first in liquid
receiver tanks 543(a-e), then pumps, such as multi-stage
centrifugal pump, 544(a-e), raises the pressure of the liquid gas
and feeds it into the pipeline. Cooling for the 542(a-e) condensers
is provided by recirculating the chilled liquid through chillers
541(a-h) using chilled water pumps 545(a-h). Liquid CO.sub.2 from
5th stage liquid receiver, 543(a-e) is pumped to pipeline pressure
using 5.sup.th stage liquid CO.sub.2 pumps, 544(a-e). High-pressure
liquid CO.sub.2 leaves the process through header 546. The chilled
liquid is a coolant and can be water or some other suitable coolant
liquid. The coolant may be circulated within the vapor condensers
542(a-e) using piping or coils to maximize heat transfer between
the coolant and the gas being condensed.
[0030] Pumps 505(a-e) are different from other pumps, such as
515(a-e) for economic reasons. At the high flow rates required for
the first stage, the cost of traditional horizontal pumps is
significantly higher than that of vertical wet pit mixed flow
pumps. These vertical wet pit mixed flow pumps are normally used in
agriculture and in industrial cooling towers where relatively low
head and very high flows are required.
[0031] The chillers used in stage 5 are different than the air
coolers in stages 1-4 because of pressures and temperatures
involved. With CO.sub.2 there are two potential paths to take in
converting the gas to a liquid. One path is to use only
compression, taking the gas above the critical point and
compressing it to a point that when cooled back to atmospheric
temperatures it becomes a liquid out of the critical region. The
second path is more economical wherein the gas is compressed only
up to a point so that when a chiller is employed the gas condenses.
This requires less horsepower to pump the liquid up to pipeline
pressure of about 2,200 psig. Depending on the refrigeration
temperatures used, the compression point can be as low as 250 psig,
or up to about 700 psig. Relatively mild refrigeration using
off-the shelf chillers may be more practical and less expensive in
the example embodiments.
[0032] The vapor condensers in stage 5 are necessary because the
stage 5 is the breakover point where compression stops and
condensing starts so that multi-stage centrifugal pumps can bring
the pressure from 700 psig to 2,200 psig.
[0033] FIG. 6 shows an example embodiment of the stages 1-5 linked
together. First stage of the liquid piston CO.sub.2 compression
process 500 takes energy Q-1 to compress CO.sub.2 which is then
cooled in first stage discharge coolers 501(a-e) where energy Q-6
is removed resulting in the compressed CO.sub.2 output 506. The
output 506 of the first stage is then fed into the second stage
compression process 510 using energy Q-2 to compress the CO.sub.2,
which is then cooled in the second stage discharge coolers 511(a-e)
where energy Q-7 is removed, resulting in compressed CO.sub.2
output 516. The output 516 of the second stage is then fed into the
third stage compression process 520 using energy Q-3 to compress
the CO.sub.2, which is then cooled in the third stage discharge
coolers 521(a-e) where energy Q-8 is removed, resulting in
compressed CO.sub.2 output 526. The output 526 of the third stage
is then fed into the fourth stage compression process 530 using
energy Q-4 to compress the CO.sub.2, which is then cooled in the
fourth stage discharge coolers 531(a-e) where energy Q9 is removed,
resulting in compressed CO.sub.2 output 536. Compressed CO.sub.2
536 is then fed into the fifth stage pump 540 where energy Q-5 is
used to condense the CO.sub.2 into a liquid, collect the liquified
portion, and then pressurize it up to the line pressure, typically
around 2,200 psig, and then produce an output 546 of pressurized
liquified CO.sub.2.
[0034] The displacer vessels can use a working fluid to compress
the gas, in this case CO.sub.2. The working fluid can be in direct
contact with the gas, it can be contained in a bladder that
expands, or there could be a physical piston within the displacer
vessel separating the gas from the working fluid. Any pump that can
pump a working fluid, such as water in the disclosed example
embodiments. Suitable working fluids include water, water glycol
mix, hydraulic fluid, produced oil, hydrocarbon by-product,
produced water, or any other suitable working fluid.
[0035] The gas being compressed to a liquid in the disclosed
examples is CO.sub.2. However, any gas or vapors could be
compressed using the disclosed embodiments, with modifications to
account for different pressures, temperatures, and other properties
associated with phase changes for a particular gas.
[0036] The displacer vessels may be displacement tanks that can be
either horizontal or vertical in orientation. The displacer vessels
are sized based on the frequency of valve cycling desired.
[0037] The liquid displacer pumps may be centrifugal, vertical,
positive displacement, or any other pumps suitable for the desired
working fluid at the desired temperature and pressure. The pumps
will operate along their design operating curve between the
beginning and ending pressure of the displacer vessels. For the
rated gas flow rate of the unit, the pumps must displace the
corresponding volume of liquid to match the actual volume of the
gas flowed during the compression cycle. The density of the gas
progressively increases during the compression step as the
displacer pressure increases.
[0038] The example embodiments will be equipped with multiple PLCs
and/or a DCS control system. The controls and will be powered via
UPS power. Electric valves, if installed, considered to be critical
for a safe shutdown of the process will be powered by the battery
backup boxes. UPS supply will be from a 24 VDC Battery Box or a
redundant power supply. In case of absence of Main Utility power,
the batteries at the battery-backup boxes will provide enough
backup time to the process DC S/PLC, critical valves, and critical
instrumentation throughout the process with the purpose of a safely
shutdown of the process and have the ability to identify and
monitoring the main process variables and parameters during this
time.
* * * * *