Method and apparatus for low-temperature separation of a gas containing co2 to produce a co2-rich fluid

Abstract

The invention relates to a method for the low-temperature separation of a feed gas (1) containing CO2, at least one component lighter than CO2 and at least one component heavier than CO2, wherein, in order to produce a CO2-rich fluid, the feed gas is compressed (Cl, C2, C3, C4), the compressed gas being cooled in a first heat exchanger (E), the gas cooled in the first heat exchanger is separated at low temperature in a first distillation column (C) to produce a liquid that is enriched in CO2 and depleted in the at least one component lighter than CO2 (8) and a gas that is depleted in CO2 and enriched in the at least one component lighter than CO2 (7), the gas depleted in CO2 is heated in the first heat exchanger, a first part of the liquid (15) enriched in CO2 is expanded and sent to a second distillation column (N) in liquid form, a second part (9) of the liquid enriched in CO2 is vaporised in the first heat exchanger then sent in gas form into the tank of the second distillation column, a liquid depleted in CO2 and enriched in the at least one heavier component (25) is withdrawn from the second column, and a gas enriched in CO2 and depleted in the at least one heavier component (21) is withdrawn at the top of the second column as product.

Description

Process 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 CO2-containing gas to produce a CO2-rich fluid. The mixture to be separated contains CO2, at least one component heavier than CO2, such as NO2, and at least one component lighter than CO2, such as carbon monoxide, hydrogen, nitrogen, oxygen, NO, methane.

[0002] In particular, the process can treat a gas resulting from combustion, for example an oxycombustion process, a boiler, an SMR, 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] It is known from "A study of the extraction of CO2 from the flue gas of a 500MW pulverized coal fired boiler" by Allam et al, Energy Conversion and Management, vol 33, no. 5-8, 1992 to separate CO2-containing flue gases in a first distillation column to produce a liquid enriched in CO2 and depleted in a lighter component and a gas depleted in CO2 and enriched in the lighter component. A gas from the first distillation column is separated in a second distillation column to form a liquid enriched in a heavy component and a gas enriched in CO2, which is the product of the process.

[0006] The present invention feeds the second column with a first portion of the CO2-enriched liquid which is expanded and sent to a second distillation column in liquid form and a second portion of the CO2-enriched liquid is vaporized in the first heat exchanger and then sent in gaseous form to the bottom of the second distillation column at an arrival point, the first portion of the liquid being sent to the second column at a level above the arrival point of the second portion of the liquid.

[0007] This vaporization of liquid contributes to the thermal balance of the process and allows operation of the second column as a stripping column, the first part of the liquid serving as washing gas.

[0008] According to the invention, there is provided a method for the low-temperature separation of a feed gas containing CO2, at least one component lighter than CO2 and at least one component heavier than CO2 to produce a CO2-rich fluid in which the feed gas is compressed in a compressor comprising at least two stages, the compressed gas being cooled in a first heat exchanger, the gas cooled in the first heat exchanger is separated at low temperature at least by distillation in a first distillation column to produce a liquid enriched in CO2 and depleted in the at least one component lighter than CO2 and a gas depleted in CO2 and enriched in the at least one component lighter than CO2, the gas depleted in CO2 is heated in the first heat exchanger,a liquid depleted in CO2 and enriched in at least one heavier component is withdrawn from the second column and a gas enriched in CO2 and depleted in at least one heavier component is withdrawn at the top of the second column as product characterized in that a first part of the liquid enriched in CO2 is expanded and sent to a second distillation column in liquid form, a second part of the liquid enriched in CO2 is vaporized in the first heat exchanger then sent in gaseous form to the bottom of the second distillation column at an arrival point, the first part of the liquid being sent to the second column at a level above the arrival point of the second part of the liquid.,

[0009] According to other optional features:a third portion of the liquid enriched in CO2 and depleted in the at least one lighter component vaporizes in the first heat exchanger and is returned to the first distillation column.a portion of the gas enriched in CO2 and depleted in the at least one heavier component is condensed and returned to the top of the second column.at least a portion of the cold to condense the portion of the gas enriched in CO2 and depleted in the at least one heavier component is produced by a first closed refrigeration cycle.a compressor of the first refrigeration cycle is driven by a turbine which expands at least a portion of a gas depleted in the at least one light component produced by the separation of the feed gas by partial condensation and / or by distillation.the second and optionally the third portion of the liquid enriched in CO2 and depleted in the at least one lighter component is pressurized by a pump upstream of the first heat exchanger. a closed refrigeration cycle produces cold to cool the first heat exchanger. the compressed and cooled feed gas is separated by partial condensation to produce the CO2-depleted gas and a liquid, the liquid is separated by distillation in the first distillation column, being sent to the top of the first distillation column. the second distillation column operates at a higher pressure than the first distillation column. the second distillation column operates at the same pressure as the first distillation column.

[0010] According to another object of the invention, there is provided an apparatus for the low-temperature separation of a feed gas containing CO2, at least one component lighter than CO2 and at least one component heavier than CO2 to produce a CO2-rich fluid comprising a compressor comprising at least two stages, a first heat exchanger, a first distillation column, a second distillation column, a conduit for sending the feed gas to be compressed in the compressor comprising at least two stages, a conduit for sending the compressed gas to cool in the first heat exchanger, means for sending the gas cooled in the first heat exchanger to separate at low temperature at least by distillation in the first distillation column 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,a pipe for sending the CO2-depleted gas to be heated in the first heat exchanger, an expansion means, a pipe for sending a first part of the CO2-enriched liquid to be expanded in the expansion means, means for withdrawing a CO2-depleted liquid enriched in the at least one heavier component from the second column and means for withdrawing a CO2-enriched gas depleted in the at least one heavier component at the top of the second column as a product characterized in that it comprises a pipe for sending the expanded first part to the second distillation column in liquid form, a pipe for sending a second part of the CO2-enriched liquid to vaporize in the first heat exchanger, and a pipe for sending the second vaporized part in the bottom of the second distillation column to an arrival point,the first part of the liquid being sent to the second column at a level above the point of arrival of the second part of the liquid,.,

[0011] According to another object of the invention, there is provided an apparatus for the low temperature separation of a feed gas containing CO2, at least one component lighter than CO2 and at least one component heavier than CO2 to produce a CO2-rich fluid comprising a compressor comprising at least two stages, a first heat exchanger, a first distillation column, a second distillation column, a conduit for sending the feed gas to be compressed in the compressor comprising at least two stages, a conduit for sending the compressed gas to cool in the first heat exchanger,means for sending the cooled gas in the first heat exchanger to separate at low temperature at least by distillation in the first distillation column to produce a liquid enriched in CO2 and depleted in the at least one component lighter than CO2 and a gas depleted in CO2 and enriched in the at least one component lighter than CO2, a pipe for sending the gas depleted in CO2 to be heated in the first heat exchanger, an expansion means, a pipe for sending a first part of the liquid enriched in CO2 to be expanded in the expansion means, a pipe for sending the first expanded part to the second distillation column in liquid form, means for withdrawing a liquid depleted in CO2 and enriched in the at least one heavier component from the second column and means for withdrawing a gas enriched in CO2 and depleted in the at least one heavier component at the top of the second column as product,a closed refrigeration cycle comprising at least one cycle compressor and comprising at least one product compressor, at least one said cycle compressor and at least one said product compressor being integrated into a single compression machine.,

[0012] According to other optional features, the apparatus comprises:a pump for pressurizing the second portion of the CO2-enriched liquid upstream of the first heat exchanger.a pump for pressurizing the first portion of the CO2-enriched liquid upstream of the second distillation column.a pump for pressurizing a portion of the CO2-enriched liquid upstream of the first heat exchanger and expansion means for expanding this portion of the liquid upstream of the first distillation column.a phase separator for separating the cooled feed gas in the first heat exchanger and means for sending liquid from the phase separator to the first distillation column.-the means for sending liquid from the phase separator to the first distillation column are connected to the head of the first distillation column.a single pump for pressurizing the second portion of the CO2-enriched liquid upstream of the first heat exchanger and the first portion of the CO2-enriched liquid upstream of the second distillation columna single pump for pressurizing the portion of the CO2-enriched liquid upstream of the first heat exchanger upstream of the first column and the second portion of the CO2-enriched liquid upstream of the first heat exchanger and / or the first portion of the CO2-enriched liquid upstream of the second distillation column.

[0013] The invention will be described in more detail with reference to the figures:

[0014] schematically represents the steps preceding a method according to the invention.

[0015] schematically represents a method according to the invention.

[0016] schematically represents a method according to the invention.

[0017] The process for treating a gas, for example from combustion, includes:cooling the gascompression of the cooled gasdrying the compressed gasseparation of the compressed gas by pressure swing adsorption (designated by the well-known acronym PSA)compression of the residual gas produced by the PSAlow-pressure separation of the compressed residual gas using cold production means.

[0018] illustrates the first steps of the method according to a variant of the invention.

[0019] FG gas is a combustion gas (in English "flue gas") containing CO2, nitrogen. It is cooled in a water washing column Q (in English "quench column"), water 41 being sent to the top of the column in order to reduce the temperature of the FG gas from 160 ° C to ~ 40 ° C. A part of the condensates taken from the bottom of column Q are cooled against water CW and are recycled as flow 45 to cool the FG gas.

[0020] The cooled gas 43 taken at the top of column Q is saturated with water and is compressed by a multi-stage compressor C1, C8, C9, C10 to a pressure of about 9 bar abs. Most of the water in the gas 43 is thus condensed and the water condensates formed in the separators S1, S2, S3, between the stages are collected to form part of the flow 45.

[0021] The compressed gas is then dried by partial condensation after water cooling CW and water cooling W from a cooling tower T to cool the compressed gas to about 10°C. The condensed water in separator S4 joins flow 45.

[0022] The gas is then further dried in dryers D before being sent to the PSA, here indicated as CO2 PSA, which produces a CO2-enriched and nitrogen-depleted gas at a first pressure 1 and a CO2-depleted but nitrogen-enriched gas at a second pressure higher than the first pressure. The regeneration of the PSA is carried out by a gas 3 which will be described later.

[0023] The nitrogen-enriched gas is expanded from about 8 bar to atmospheric pressure, in order to produce part of the energy to compress the gas FG. Then it is used to cool the water H20 in tower T before being sent to the air as the overhead gas of tower T. The cooled water W is pumped by pump P2 to cool the gas upstream of separator S4 as already described.

[0024] The CO2-enriched gas 1 from adsorption separation in the CO2 PSA unit is compressed in a compressor to approximately 39 bar and separated at low temperature, i.e. below 0°C or even below -30°C.

[0025] Two different ways to accomplish these next steps will be described in the set.

[0026] schematically represents a method according to the invention.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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 at least one lighter component, here at least nitrogen. This gas heats up in the first exchanger E 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] The liquid 5 from the phase separator S is 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.

[0036] Pump P can be used to simply overcome hydrostatic pressure and pressure losses, so that columns C, N operate at the same pressure.

[0037] Otherwise, column C can operate at a higher pressure than column N, the pressurization of the fluids entering the column by pump allowing a particularly inexpensive operation.

[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] schematically represents another method according to the invention.

[0049] 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 a single cooler R5 downstream of the last stage C4. This flow 1 is the residual of a CO2 PSA 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.

[0050] 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.

[0051] The cooled gas flow in the cooler 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.

[0052] 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 at least one lighter component, here at least nitrogen. This gas is heated in the first exchanger E and then expanded in a turbine T. The gas 3 contains most of the nitrogen present in the flow 1 as well as carbon dioxide.

[0053] 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 is then heated in the exchanger E and can be used to regenerate adsorbents to dry the gas feeding the PSA to produce flow 1. The gas used for the regeneration of the dryers D is mixed with the gas to be separated downstream of stage C10. In this way, the CO2 it contains is recovered and more NOX is absorbed during the partial condensation upstream of the separator S4.

[0054] In addition or alternatively the expanded flow 3 can feed the PSA unit to recover the CO2 it contains.

[0055] The liquid 5 from the phase separator S is expanded to approximately 14 bars and sent to the top of a distillation column C from which a liquid 9 enriched in CO2 and depleted in at least one light component is withdrawn in the bottom. The liquid can be pressurized by a pump P or otherwise transferred thanks to the pressure differential. A portion of the liquid is sent to vaporize in the first heat exchanger E, a portion 11 of the vaporized liquid sent to the bottom of column C as reboiling and the other portion 19 being sent to feed column N in the bottom in gaseous form. The remainder of the pressurized liquid is sent as intermediate reflux to column N in liquid form.

[0056] The overhead gas 7 from column C is heated in the first exchanger E and is enriched with light components of the liquid 5, for example oxygen and / or nitrogen and / or methane and / or NO. It can be recycled upstream of the PSA.

[0057] 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.

[0058] In this flow-fed column, the at least one impurity heavier than CO2 is washed by an intermediate reflux of CO2 and an overhead reflux of pure CO2 to produce in the tank a liquid enriched in the at least one heavier impurity, such as NOX, for example NO2.

[0059] Liquid 25 enriched in NOx heavier than CO2, such as NO2, is withdrawn from the bottom of column N. Liquid 25 is heated in exchanger E then recycled to the combustion gas FG upstream of column Q.

[0060] Compressor C5 driven by turbine T is part of a CO2 or ammonia refrigeration cycle. The gas is then compressed by further 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.

[0061] The overhead gas 21 from column N constitutes the CO2-rich gaseous product in this example. This gas, enriched in CO2 and depleted in at least one heavy component, is condensed in a heat exchanger 22, cooled by the refrigeration cycle C22, C23. A portion 28 is returned to column N as reflux and the remainder 24 of the liquid constitutes a product of the process.

[0062] Exchanger E, phase separator S and columns C, N are inside a thermally insulated enclosure CB.

[0063] Three 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. A closed cycle of CO2 or ammonia using compressors C22, C23.

[0064] 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.

Claims

A low-temperature separation process of a feed gas (1) containing CO2, at least one component lighter than CO2 and at least one component heavier than CO2 to produce a CO2-rich fluid in which the feed gas is compressed in a compressor (C1, C2, C3, C4) comprising at least two stages, the compressed gas being cooled in a first heat exchanger (E), the gas cooled in the first heat exchanger is separated at low temperature at least by distillation in a first distillation column (C) to produce a liquid enriched in CO2 and depleted in at least one component lighter than CO2 (8) and a gas (7) depleted in CO2 and enriched in at least one component lighter than CO2, the CO2-depleted gas (7) is heated in the first heat exchanger,a liquid depleted in CO2 and enriched in at least one heavier component (25) is drawn from a second column and a gas enriched in CO2 and depleted in at least one heavier component (21) is drawn from the top of the second column as product (24, 27) characterized in that a first part of the liquid (10, 15) enriched in CO2 is depressurized and sent to the second distillation column (N) in liquid form, a second part (9) of the liquid enriched in CO2 is vaporized in the first heat exchanger and then sent in gaseous form to the tank of the second distillation column at an arrival point, the first part of the liquid being sent to the second column at a level above the arrival point of the second part of the liquid, A process according to claim 1 wherein a third part (17) of the liquid enriched in CO2 and depleted in at least one lighter component vaporizes in the first heat exchanger (E) and is returned to the first distillation column (C). A process according to claim 1 or 2 in which a portion (23, 28) of the gas enriched in CO2 and depleted in at least one heavier component is condensed and returned to the top of the second column (N). A process according to claim 3 in which at least a part of the cold to condense the part (28) of the gas enriched in CO2 and depleted in at least one heavier component is produced by a first closed refrigeration cycle (C21, C22, C23). A method according to claim 4 wherein a compressor of the first refrigeration cycle (C21) is driven by a turbine (T) which expands at least a part (3) of a depleted gas into at least one light component produced by the separation of the feed gas by partial condensation (S) and / or by distillation (C). A method according to any one of the preceding claims wherein the second (9) and optionally the third part (17) of the liquid enriched in CO2 and depleted in at least one lighter component is pressurized by a pump (P) upstream of the first heat exchanger (E). A method according to any one of the preceding claims in which a closed refrigeration cycle (C21, C22, C23) produces cold to cool the first heat exchanger (E). A process according to any one of the preceding claims, wherein the compressed and cooled feed gas (1) is separated by partial condensation (S) to produce the CO2-depleted gas (3) and a liquid (5), the liquid is separated by distillation in the first distillation column (C), being sent to the top of the first distillation column. A low-temperature separation apparatus for a feed gas containing CO2, at least one component lighter than CO2 and at least one component heavier than CO2, to produce a CO2-rich fluid, comprising a compressor (C1, C2, C3, C4) comprising at least two stages, a first heat exchanger (E), a first distillation column (C), a second distillation column (N), a conduit for sending the feed gas to be compressed in the compressor comprising at least two stages, a conduit for sending the compressed gas to be cooled in the first heat exchanger, means for sending the cooled gas in the first heat exchanger to be separated at low temperature, at least by distillation in the first distillation column, to produce a liquid enriched in CO2 and depleted in at least one component lighter than CO2 and a gas depleted in CO2 and enriched in at least one component lighter than CO2.a conduit for sending the CO2-depleted gas to be heated in the first heat exchanger, an expansion means, means for drawing off a liquid (25) depleted in CO2 and enriched in at least one heavier component from the second column and means for drawing off a gas enriched in CO2 and depleted in at least one heavier component (21) at the top of the second column as product (24, 27) characterized in that it comprises a conduit for sending a first part of the liquid (10, 15) enriched in CO2 to be expanded in the expansion means, a conduit for sending the first expanded part to the second distillation column in liquid form, a conduit for sending a second part of the liquid (9) enriched in CO2 to be vaporized in the first heat exchanger and a conduit for sending the second vaporized part to the tank of the second distillation column at an end point,the first part of the liquid being sent to the second column at a level above the arrival point of the second part of the liquid. Apparatus according to claim 9 comprising a closed refrigeration cycle comprising at least one cycle compressor (CC) and comprising at least one product compressor (C6, C7), at least one said cycle compressor and at least one said product compressor being integrated into a single compression machine. Apparatus according to any one of claims 9 and 10 comprising a pump (P) for pressurizing the second part of the CO2-enriched liquid (9) upstream of the first heat exchanger. Apparatus according to any one of claims 9 to 11 comprising a pump (P) for pressurizing the first part of the liquid (19) enriched in CO2 upstream of the second distillation column (N). Apparatus according to any one of claims 9 to 12 comprising a pump (P) for pressurizing a portion of the liquid (17) enriched in CO2 upstream of the first heat exchanger (E) and expansion means (17) for expanding this portion of the liquid upstream of the first distillation column (C). Apparatus according to any one of claims 9 to 13 comprising a phase separator (S) for separating the cooled feed gas in the first heat exchanger (E) and means for sending liquid (5) from the phase separator to the first distillation column (C). Apparatus according to claim 14 in which the means for sending liquid (5) from the phase separator to the first distillation column (C) are connected to the head of the first distillation column.

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