Method and apparatus for low-temperature separation of a gas containing co2 to produce a co2-rich fluid
Patent Information
- Application Number
- EP2023727952
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-07-29
- Filing Date
- 2023-05-16
- Publication Date
- 2025-03-26
AI Technical Summary
Current methods are ineffective in efficiently separating CO2 from gases containing lighter components at low temperatures, particularly in producing a CO2-rich fluid with high CO2 concentration from combustion processes or waste gases.
A process and apparatus involving a multi-stage compressor, cooling stages, heat exchangers, phase separation, and distillation columns to compress, cool, and separate CO2 from lighter components, utilizing a turbine-driven refrigeration cycle to enhance energy recovery and produce a CO2-rich fluid through partial condensation and distillation.
The solution effectively produces a CO2-rich fluid with concentrations above 80 mol% CO2, operating at low temperatures below 0°C, and integrates energy recovery to enhance efficiency and productivity.
Smart Images
Figure 1.1
Abstract
Description
Method and apparatus for low temperature separation of a CO2-containing gas to produce a CO2-rich fluid
[0001] The present invention relates to a method and apparatus for low-temperature separation of a gas containing CO2 to produce a CO2-rich fluid. The mixture to be separated contains CO2 and at least one component lighter than CO2, such as carbon monoxide, hydrogen, nitrogen, oxygen, methane.
[0002] In particular, the process can treat a gas resulting from combustion, for example an oxycombustion process, to form a product rich in CO2, for example containing at least 80 mol% of CO2, or even at least 90 mol% of CO2.
[0003] A gas containing CO2, for example a waste gas from an H2 PSA or a CO2 PSA.
[0004] Low temperature separation operates at temperatures below 0°C or even below -40°C.
[0005] According to the invention, there is provided a method for the low-temperature separation of a CO2-containing gas to produce a CO2-rich fluid in which a gas containing CO2 and at least one component lighter than CO2 is compressed in a compressor comprising at least two stages, the gas being cooled downstream of a last of the stages first in a cooler and then cooled by heat exchange with water at room temperature or vice versa and then cooled in a first heat exchanger, the gas cooled in the first heat exchanger is separated at low temperature by partial condensation to produce a liquid enriched in CO2 and depleted in the component lighter than CO2 and a gas depleted in CO2 and enriched in the component lighter than CO2,the CO2-depleted gas is first heated in the first heat exchanger and then in the cooler before being expanded in a turbine and the CO2-enriched liquid is separated by distillation to form at least one CO2-rich fluid.,
[0006] According to other optional features:the at least one CO2-rich fluid is a liquid and at least a portion of the CO2-rich fluid vaporizes in the first heat exchanger.the at least one vaporized CO2-rich fluid is compressed in a compressor driven by the turbine.the CO2-enriched liquid is expanded and sent to the top of a stripping column and the at least one CO2-rich fluid is a bottom liquid of the stripping column.the CO2-enriched liquid is sent to the top of a scrubbing column and the liquid from the scrubbing column feeds a distillation column.a top gas from the distillation column is compressed in a compressor driven by the turbine.the CO2-depleted gas enters the cooler at a temperature above ambient temperature, for example above 30°C.the gas to be separated is separated by partial condensation (S) to produce the CO2-depleted gas and a liquid, the liquid is separated by distillation in a distillation column to produce the CO2-rich fluid, which is preferably a CO2-rich liquid. at least part of the cold is provided by a closed refrigeration cycle comprising at least one cycle compressor driven by the turbine. the at least one CO2-rich fluid is a gas which heats up in the first heat exchanger before being compressed.
[0007] According to another object of the invention, there is provided an apparatus for the low temperature separation of a gas containing CO2 to produce a CO2-rich fluid comprising a compressor comprising at least two stages, a cooler, a water cooler, a first heat exchanger, a phase separator, a turbine and at least one distillation column, means for sending a gas containing CO2 and at least one component lighter than CO2 to the compressor comprising at least two stages, means for sending the compressed gas from the compressor to cool in the cooler and the water cooler, means for sending the cooled gas in the cooler and the water cooler to the first heat exchanger,means for sending the cooled gas in the first heat exchanger to the phase separator to form a liquid enriched in CO2 and depleted in the component lighter than CO2 and a gas depleted in CO2 and enriched in the component lighter than CO2, means for sending the CO2-depleted gas to be heated first in the first heat exchanger and then in the cooler, means for sending the CO2-depleted gas heated in the cooler to expand in the turbine and means for sending the CO2-enriched liquid is separated in the at least one distillation column to form at least one CO2-rich fluid.,
[0008] According to other optional aspects:the apparatus comprises a cycle compressor coupled to the turbine.the apparatus comprises a CO2-rich product compressor coupled to the turbine.a portion of the gas compressed in the product compressor is liquefied and returned to the at least one distillation column as reflux.the apparatus comprises a distillation column fed with the CO2-enriched liquid from the phase separator and a NOX removal column fed with a bottom liquid of the distillation column.
[0009] According to another object of the invention, there is provided an apparatus for the low-temperature separation of a gas containing CO2 to produce a CO2-rich fluid comprising a compressor comprising at least two stages, a first heat exchanger, a cooler, a distillation system comprising at least one phase separator and / or at least one distillation column, a turbine, means for sending a gas containing CO2 and at least one component lighter than CO2 to be compressed in the compressor, means for sending compressed gas to cool downstream of at least one of the stages in the cooler, means for sending the compressed and cooled gas to cool in the first heat exchanger,means for sending the cooled gas into the first heat exchanger to separate by partial condensation and / or distillation to produce a fluid rich in CO2 and depleted in the component lighter than CO2 and a gas depleted in CO2 and enriched in the component lighter than CO2, means for sending the CO2-depleted gas to heat up first in the first heat exchanger and then in the cooler and means for sending the CO2-depleted gas heated in the cooler to expand in the turbine.,
[0010] The invention will be described in more detail with reference to the figures:
[0011] schematically represents a method according to the invention.
[0012] schematically represents a method according to the invention.
[0013] schematically represents a process using a single distillation column to remove a component lighter than CO2 in a first column.
[0014] A gas flow 1 is compressed in a multi-stage compressor, here four stages C1, C2, C3, R4, here with a cooler R1, R2, R3 between each pair of stages and two coolers R4, R5 downstream of the last stage. This flow 1 can for example be the waste of a PSA H2 or CO2 and can be compressed to at least 35 bar abs in the compressor stages C1 to C4. The coolers R1 to R3 are cooled only by cooling water CW, as is the cooler R5.
[0015] Gas stream 1 contains CO2 and at least one lighter component which may be hydrogen, carbon monoxide, nitrogen or oxygen. In this example, the gas stream is rich in nitrogen. Preferably gas stream 1 contains less than 1 mol% methane.
[0016] The gas flow cooled in the two coolers R4, R5 downstream of the last stage is cooled to a temperature below -50°C in a first heat exchanger E by heat exchange with at least one fluid from the cold separation. This exchanger E can be of the brazed aluminum plate and fin type.
[0017] The gas flow 1 partially condenses in the first heat exchanger E and the two-phase flow formed is separated in a phase separator S forming a gas 3 enriched in the at least one lighter component, here at least nitrogen. This gas heats up in the first exchanger E to a temperature above ambient temperature, for example above 30°C and then heats up in the first cooler R4 directly following the last stage C4 of the compressor from a temperature of 30°C to a temperature of 100°C, being the only cooling fluid sent to this first cooler R4. Then the gas cooled in the first cooler R4 cools down in a second cooler R5 against cooling water CW to an ambient temperature below 40°C, or even below 30°C.
[0018] Alternatively, the gas flow 3 enriched with the at least one light component can cool the compressed gas in the second cooler R5, the first being cooled by water.
[0019] Alternatively or in addition, the flow enriched with at least one light component can cool the compressed gas in a cooler R1, R2, R3 between two stages of the compressor.
[0020] Thus the gas 3 to be expanded in a turbine T is preheated against the compressed gas in the compressor C1 to C4, so that the heat of compression makes it possible to produce more energy in the turbine.
[0021] The gas flow 3 enriched with light component heated in the first cooler R4 is at 8 bar and is expanded in the turbine T from this pressure to approximately atmospheric pressure. The gas flow enriched with light component 3 can then be used to regenerate adsorbents to dry the gas feeding the PSA to produce flow 1.
[0022] The liquid 5 from the phase separator S is expanded and then sent to the top of a distillation column C which is a stripping column from which a liquid 9 enriched in CO2 and depleted in the at least one light component is withdrawn at the bottom. This liquid can form at least part of the product of the process. At least part of the liquid is pressurized by a pump P and can be sent to vaporize in the first heat exchanger E, a part 11 of the vaporized liquid possibly being sent to the bottom of the column C as reboil. At least a part 13 of the vaporized liquid can be compressed in a product compressor C5 driven by the turbine T to produce a CO2-rich gas. The gas is then compressed by other compression stages C6, C7, with a water cooler CW between each pair of stages (R6 between C5 and C6) and a final cooler downstream of stage C7. The gas compressed in C7 constitutes the CO2-rich gaseous product in this example.
[0023] The head gas 7 from column C is heated in the first exchanger E.
[0024] Exchanger E, phase separator S and column C are inside a thermally insulated enclosure CB.
[0025] Two means of cold production are used: A closed cycle in which CO2 is compressed in a CC cycle compressor and returned to the first heat exchanger where it is cooled, liquefied, separated and expanded in two different valves to form two flows at 5.5 and 9.5 bar abs. These two flows are reheated in the first heat exchanger E to provide cold and are then returned to the CC cycle compressor. Vaporization of the liquid 9 in exchanger E.
[0026] Obviously the system can include several phase separators, in series and / or in parallel and upstream of the distillation as well as at least one distillation column.
[0027] If the system does not include a column separator, the gas expanded in the turbine will be taken at the top of the distillation column.
[0028] schematically represents a process using two columns to remove a component lighter than CO2 in a first column and a component heavier than CO2 in a second column.
[0029] A gas flow 1 is compressed in a multi-stage compressor, here four stages C1, C2, C3, C4, here with a cooler R1, R2, R3 between each pair of stages and two coolers R4, R5 downstream of the last stage. This flow 1 can for example be the waste of a PSA H2 or CO2 and can be compressed to at least 35 bar abs in the compressor stages C1 to C4. The coolers R1 to R3 are cooled only by cooling water CW, as is the cooler R5.
[0030] Gas stream 1 contains CO2 and at least one lighter component which may be hydrogen, carbon monoxide, nitrogen or oxygen. In this example, the gas stream is rich in nitrogen. Preferably gas stream 1 contains less than 1 mol% methane.
[0031] The gas flow cooled in the two coolers R4, R5 downstream of the last stage is cooled to a temperature below -50°C in a first heat exchanger E by heat exchange with at least one fluid from the cold separation. This exchanger E can be of the brazed aluminum plate and fin type.
[0032] The gas flow 1 partially condenses in the first heat exchanger E and the two-phase flow formed is separated in a phase separator S forming a gas 3 enriched in the at least one lighter component, here at least nitrogen. This gas heats up in the first exchanger E to a temperature above ambient temperature, for example above 30°C and then heats up in the first cooler R4 directly following the last stage C4 of the compressor from a temperature of 30°C to a temperature of 100°C, being the only cooling fluid sent to this first cooler R4. Then the gas cooled in the first cooler R4 cools down in a second cooler R5 against cooling water CW to an ambient temperature below 40°C, or even below 30°C.
[0033] Alternatively, the gas flow 3 enriched with the at least one light component can cool the compressed gas in the second cooler R5, the first being cooled by water.
[0034] Alternatively or in addition, the flow enriched with at least one light component can cool the compressed gas in a cooler R1, R2, R3 between two stages of the compressor.
[0035] Thus the gas 3 to be expanded in a turbine T is preheated against the compressed gas in the compressor C1 to C4, so that the heat of compression makes it possible to produce more energy in the turbine.
[0036] The gas flow 3 enriched with light component heated in the first cooler R4 is at 8 bar and is expanded in the turbine T from this pressure to approximately atmospheric pressure. The gas flow enriched with light component 3 can then be used to regenerate adsorbents to dry the gas feeding the PSA to produce flow 1. In addition or alternatively the expanded flow 3 can feed the PSA unit to recover the CO2 it contains.
[0037] The liquid 5 from the phase separator S is expanded and then sent to the top of a distillation column C from which a liquid 9 enriched in CO2 and depleted in the at least one light component is withdrawn in the bottom. At least part of the liquid is pressurized by a pump P and can be sent to vaporize in the first heat exchanger E, a part 11 of the vaporized liquid possibly being sent to the bottom of the column C as reboiling and the other part 19 being sent to feed the column N in the bottom. The top gas 7 from the column C is heated in the first exchanger E.
[0038] The N column is a column for removing NOx heavier than CO2, NOx being a term covering the following compounds: nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (N2O), dinitrogen tetraoxide (N2O4), nitrogen trioxide (N2O3). Since NO is lighter than CO2, the N column is used to remove nitrogen dioxide (NO2), nitrous oxide (N2O), dinitrogen tetraoxide (N2O4), nitrogen trioxide (N2O3), if present in the liquid.
[0039] In this column fed by flow 19, at least one impurity heavier than CO2 is washed by an intermediate reflux of CO2 15 and a head reflux 23 of pure CO2 to produce in the tank a liquid enriched in at least one heavier impurity 25, such as NOX, for example NO2.
[0040] The liquid enriched in the at least heavier impurity 25 vaporizes in the first exchanger E.
[0041] The overhead gas 21 from column N constitutes the product purified of at least one heavier impurity and is heated in the first exchanger E before being compressed in a first compression stage C5 driven by the turbine T. After cooling in R6, the flow is divided, a part 23 being condensed in the first exchanger E and the remainder 27 being compressed in the compression stages C6, C7 to form a pressurized gaseous product. The gas compressed in C7 constitutes the CO2-rich gaseous product in this example.
[0042] Part 23 is returned to the head of column N as reflux.
[0043] Exchanger E, phase separator S and column C are inside a thermally insulated enclosure CB.
[0044] Two means of cold production are used: A closed cycle in which CO2 is compressed in a CC cycle compressor and returned to the first heat exchanger where it is cooled, liquefied, separated and expanded in two different valves to form two flows at 5.5 and 9.5 bar abs. These two flows are reheated in the first heat exchanger E to provide cold and are then returned to the CC cycle compressor. Vaporization of the liquid 9 in exchanger E.
[0045] Obviously the system can include several phase separators, in series and / or in parallel and upstream of the distillation as well as at least one distillation column.
[0046] If the system does not include a column separator, the gas expanded in the turbine will be taken at the top of the distillation column.
[0047] Preferably, at least one of the CC cycle compressors and at least one product compressor C6, C7 are integrated into a single compression machine.
[0048] The turbine may drive at least one refrigeration cycle compressor, e.g. CC and / or at least one other product compressor C6, C7 in addition to or instead of compressor C5.
Claims
A low-temperature separation process of a CO2-containing gas to produce a CO2-rich fluid, in which a gas containing CO2 and at least one component lighter than CO2 is compressed in a compressor (C1, C2, C3, C4) comprising at least two stages, the gas being cooled downstream of a last of the stages first in a cooler (R4, R5) and then cooled by heat exchange with water (CW) at ambient temperature or vice versa and then cooled in a first heat exchanger (E), the gas cooled in the first heat exchanger is separated at low temperature by partial condensation to produce a liquid (5) enriched in CO2 and depleted in the component lighter than CO2 (9, 21) and a gas (3) depleted in CO2 and enriched in the component lighter than CO2,The CO2-depleted gas is first heated in the first heat exchanger and then in the cooler before being expanded in a turbine (T) and the CO2-enriched liquid is separated by distillation to form at least one CO2-rich fluid (8,9,21). Method according to claim 1 wherein at least one CO2-rich fluid is a liquid (9) and at least a part of the CO2-rich fluid vaporizes in the first heat exchanger (E). Method according to claim 2 wherein at least one vaporized CO2-rich fluid is compressed in a compressor (C5) driven by the turbine (T). A method according to claim 2 or 3 wherein the CO2-enriched liquid is expanded and sent to the top of a stripping column (C) and at least one CO2-enriched fluid is a tank liquid (8,9) of the stripping column. A method according to any one of the preceding claims in which the CO2-enriched liquid (5) is sent to the top of a washing column and the liquid from the washing column feeds a distillation column. A method according to claim 5 in which a head gas (21) from the distillation column (C) is compressed in a compressor (C5) driven by the turbine (T). A method according to any one of the preceding claims in which the CO2-depleted gas enters the cooler (R4) at a temperature above the ambient temperature, for example above 30°C.
8. A process according to any one of the preceding claims wherein the gas to be separated is separated by partial condensation (S) to produce the CO2-depleted gas (3) and a liquid (5), the liquid is separated by distillation in a distillation column to produce the CO2-rich fluid (9,21), which is preferably a CO2-rich liquid (9). A method according to any one of the preceding claims, wherein at least a part of the cooling is provided by a closed refrigeration cycle comprising at least one cycle compressor driven by the turbine (T). A method according to any one of the preceding claims in which at least one CO2-rich fluid is a gas (21) which is heated in the first heat exchanger (E) before being compressed. A low-temperature separation apparatus for a CO2-containing gas to produce a CO2-rich fluid comprising a compressor (C1, C2, C3, C4) having at least two stages, a cooler (R4, R5), a water cooler, a first heat exchanger (E), a phase separator, a turbine (T) and at least one distillation column, means for sending a gas containing CO2 and at least one component lighter than CO2 to the compressor (C1, C2, C3, C4) having at least two stages, means for sending the compressed gas from the compressor to be cooled in the cooler (R4) and the water cooler (CW), means for sending the cooled gas from the cooler and the water cooler to the first heat exchanger (E), means for sending the cooled gas from the first heat exchanger to the phase separator to form a liquid enriched in CO2 and depleted in the component lighter than CO2 (9,21) and a gas (3) depleted in CO2 and enriched in the component lighter than CO2, means for sending the CO2-depleted gas to be heated first in the first heat exchanger and then in the cooler, means for sending the CO2-depleted gas heated in the cooler to expand in the turbine, and means for sending the CO2-enriched liquid to be separated in at least one distillation column to form at least one CO2-rich fluid. Apparatus according to claim 11 comprising a cycle compressor (CC) coupled to the turbine (T). Apparatus according to claim 11 comprising a CO2-rich product compressor (C5) coupled to the turbine (T). Apparatus according to claim 13 in which a portion (23) of the gas compressed in the product compressor (C5) is liquefied and returned to at least one distillation column (C) as reflux. Apparatus according to any one of claims 11 to 14 comprising a distillation column fed by the CO2-enriched liquid (5) from the phase separator and a NOX removal column (N) fed by a tank liquid from the distillation column.