METHOD AND INSTALLATION FOR CAPTURING CO2 CONTAINED IN A COMBUSTION GAS

Abstract

The invention relates to a method for capturing CO2 present in combustion gases, comprising:- a separation step during which combustion gases containing CO2 are brought into contact with an absorbent solution, this step producing gases depleted in CO2 and an absorbent solution enriched in CO2,- a step of regeneration of the absorbent solution enriched in CO2 during which the CO2 it contains is released by heating the solution by means of at least one reboiler supplied with low-pressure steam, - a step of compression of the released CO2. Part of the heat from the combustion gases is recovered upstream of the separation step by a heat pump (50). The heat produced by the latter is redistributed to reduce the amount of energy required to produce the steam used during the regeneration step. Abstract figure: figure 1

Description

Title of the invention: METHOD AND INSTALLATION FOR CAPTURING CO2 CONTAINED IN A COMBUSTION GAS Technical field

[0001] The present invention relates to a method and an installation for capturing CO2 contained in a combustion gas. Background to the invention

[0002] Gases containing acidic compounds such as CO2 and / or H2S are usually treated by absorption, by a process in which the gases are brought into contact with an absorbent solution which retains the acidic compounds by simple physical dissolution and / or by dissolution after formation of a salt or a thermally unstable complex, by reaction of said acidic compounds with a basic compound present in the absorbent solution. The absorbent solution loaded with acidic compounds is then regenerated in a regeneration zone (a stripper) in which it is kept boiling under pressure. The heat necessary to maintain this boiling is provided by reboiling the absorbent solution, that is to say by indirect heat exchange between a part of the solution to be regenerated and a hot fluid at an appropriate temperature, generally saturated water vapor.

[0003] The energy consumption of this process is however high, mainly due to the energy required for the process of regenerating the absorbent solution. Prior art

[0004] Many processes have been developed to reduce the energy consumption of a CO2 capture process.

[0005] Thus, for example, it is known to implement mechanical vapor recompression (MVR) to produce part of the vapor necessary for reboiling. This technique consists of expanding the regenerated absorbent solution at the outlet of the regeneration zone in order to produce a gaseous fluid containing essentially water and CO2, which is then compressed and returned to the regeneration zone. Similarly, it is possible to expand the absorbent solution containing the CO2 before it enters the regeneration zone, in order to produce a gaseous stream and a liquid stream. The gaseous stream is recompressed and reintroduced at the bottom of the regeneration zone while the liquid stream is sent to the top of the regeneration zone.

[0006] It is also known to compress the purified gas exiting at the top of the regeneration zone and to partially condense it (a process called “Stripper Overhead Com pressure" or SOC in English). The heat released is then used to generate steam introduced at the bottom of the regeneration zone and thus produce part of the steam required for reboiling. This method has the disadvantage of heating the purified gas, which has a negative impact on its subsequent compression.

[0007] However, there is still a need to reduce the energy consumption of a CO2 capture process. Description of the invention

[0008] The invention provides a method for capturing CO2 present in combustion gases, said method comprising:

[0009] - a step of supplying combustion gas containing CO2 to be separated,

[0010] - a step of separation of the combustion gases supplied during which the gases combustion gases supplied are brought into contact with an absorbent solution, this step producing CO2-depleted gases and a CO2-enriched absorbent solution,

[0011] - a step of regeneration of the absorbent solution enriched in CO2 during in which the CO2 it contains is released by heating the solution by means of at least one reboiler supplied with low pressure steam, in particular at a pressure of 0.1 to 1.2 MPa, preferably 0.4 to 0.6 MPa,

[0012] - a step of compressing the CO2 released during the regeneration step by means of of at least one compressor.

[0013] According to the invention, part of the heat from the supplied combustion gases is recovered by a heat pump upstream of the separation step and said heat pump distributes heat used (i) to preheat water entering a boiler producing steam supplying the at least one reboiler, (ii) to produce part of the water vapor supplying the at least one reboiler or (iii) to heat the absorbent solution to be regenerated in the regeneration step.

[0014] The present invention thus consists in recovering the heat from the combustion gases by means of a heat pump and reusing this thermal energy in the process. By using a heat pump, non-recoverable thermal energy is transformed into useful thermal energy for the process. For one unit of mechanical energy supplied to the compressor of the heat pump, several units of useful thermal energy can be produced. Thus, either by preheating the water entering the boiler and / or by producing part of the steam and / or by directly heating the absorbent solution to be regenerated in the regeneration step, it is possible to reduce the carbon footprint of the steam necessary for the regeneration of the absorbent solution by reducing the calorific value to be provided by the combustion of fossil fuel when the boiler is combustion-based.Thus, the energy efficiency and CO2 footprint of the process according to the invention are improved.

[0015] As regards the use of the heat produced by the heat pump, the Embodiments (i) or (ii) are preferred.

[0016] The low pressure steam entering the at least one reboiler is heated and condenses as it passes through the at least one reboiler. Thus, at the outlet of the latter, condensed steam is recovered.

[0017] The steam supplying the at least one reboiler can advantageously circulate in a closed circuit passing through the boiler to receive calories from the latter, passing through the at least one reboiler to transfer calories to the absorbent solution, and optionally the closed circuit comprises at least one turbine driving the at least one compressor of the compression stage or driving at least one compressor of the heat pump.

[0018] Thus, advantageously, the water entering the boiler can be condensed steam leaving the at least one reboiler.

[0019] The boiler used to produce steam supplying the at least one reboiler can produce low pressure steam, in particular at an absolute pressure of 0.2 to 1.2 MPa (1-10 bar gauge), preferably 0.4 to 0.6 MPa (3-5 bar gauge). This low pressure steam can then be sent directly to the at least one reboiler.

[0020] Alternatively, this boiler can produce steam at a so-called "high pressure" higher than the low pressure, for example at an absolute pressure of 2 to 13.5 MPa (20-135 bar gauge), preferably 4 to 9 MPa (40 - 90 bar gauge).

[0021] In this case, the high pressure steam produced by the boiler can advantageously supply at least one turbine driving the at least one compressor of the compression stage and / or driving at least one compressor of the heat pump, and the low pressure steam leaving the at least one turbine can then supply the at least one reboiler.

[0022] Advantageously, in an embodiment in which the boiler produces high pressure steam, the heat pump can produce heat transferred, in particular via a heat distribution section, to the water entering the boiler, and: - the heat pump comprises at least one compressor driven by at least one turbine, and - said heat pump turbine is driven by part of the high pressure steam produced by the boiler and the low pressure steam leaving the heat pump turbine feeds the at least one reboiler.

[0023] Advantageously, in particular in an embodiment in which the boiler produces high pressure or low pressure steam, the heat pump can produce heat transferred, in particular via a heat distribution section, to a portion of condensed steam leaving the at least one reboiler to vaporize it again and return it to the inlet of the at least one reboiler.

[0024] The recovery of heat from the combustion gases by the heat pump upstream of the separation step can be implemented in various ways, independently of the use of the heat produced by the heat pump.

[0025] In one embodiment, the heat pump can recover at least a portion of the heat from the combustion gases supplied by heat transfer via a heat recovery section in which said combustion gases circulate. This embodiment can advantageously be implemented upstream of any cooling step.

[0026] In another embodiment, the heat pump can recover at least a portion of the heat from the combustion gases supplied by heat transfer via a heat recovery section in which circulates a hot fluid having received by heat transfer at least a portion of the heat from the combustion gases. Typically, this hot fluid circulates in a closed cooling circuit receiving the heat from the combustion gases by heat transfer, for example via a direct or indirect heat exchanger. This embodiment can also advantageously be implemented upstream of any cooling step.

[0027] Advantageously, the method can comprise, upstream of the separation step with respect to the circulation of the gases: - a step of cooling the supplied combustion gases, this cooling step being implemented in a cooling system in which the supplied combustion gases are cooled by a fluid (for example via a direct contact exchanger).

[0028] Therefore, the heat pump can recover part of the heat from the combustion gases supplied by heat transfer via a heat recovery section in which the fluid heated by the combustion gases during the cooling step circulates.

[0029] Typically, the combustion gases supplied to be cooled circulate from bottom to top in the cooling system. The latter may advantageously be a gas-liquid contactor with one or more cooling stages. Typically, the cooling fluid is water and circulates in a closed circuit.

[0030] In a variant, the method comprises a second cooling step implemented after this first cooling step and before the separation step. This second cooling step is then implemented in a second cooling system in which the supplied combustion gases are further cooled by a fluid. This second cooling step may be a quenching step. Thus, the fluid leaving the second cooling step is at a lower temperature than that of the fluid leaving the first cooling step.

[0031] In another variant, the method may comprise a single cooling step. implementation in a single cooling system and the single cooling system may comprise at least two cooling stages, the combustion gases passing through the lowest cooling stage being cooled by a fluid circuit independent of at least one other fluid circuit cooling the at least one other cooling stage. Therefore, the heat pump can recover part of the heat from the combustion gases by heat transfer, via a heat recovery section in which circulates the fluid heated by the combustion gas from the lowest cooling stage.

[0032] Advantageously, the combustion gases supplied during the supply step may be combustion gases chosen from: - combustion gases from a gas turbine, in particular from a gas turbine of a natural gas liquefaction unit and / or from a combined cycle gas turbine, and / or, - the combustion gases from a combustion boiler, in particular from the boiler producing steam for the regeneration stage,

[0033] - combustion gases from industrial combustion furnaces, in particular from units of refining and in particular fluid catalytic cracking units.

[0034] The invention also relates to an installation for capturing CO2 present in combustion gases, in particular adapted to implement the method according to the invention. The installation comprises:

[0035] - a combustion gas supply line containing CO2 to be separated, - a separation unit connected to the supply line in which the supplied combustion gases are brought into contact with an absorbent solution, this unit producing CO2-depleted combustion gases and a CO2-enriched absorbent solution, - a regeneration unit connected to the separation unit and receiving the absorbent solution enriched in CO2, in which the CO2 contained in the absorbent solution is released by heating the solution by means of at least one reboiler supplied with low-pressure water vapour, - a CO2 compression unit connected to the regeneration unit and receiving the released CO2, and comprising at least one compressor.

[0036] According to the invention, the installation further comprises a heat pump comprising a heat recovery section and a heat distribution section, and: - the heat recovery section (a) is mounted on the supply line upstream of the separation unit or (b) is mounted on a line of a combustion gas cooling circuit located upstream of the separation unit with respect to the gas circulation, - the heat distribution section is mounted (i) on a water supply pipe of a boiler producing steam supplying the at least one reboiler, (ii) on a steam line supplying the at least one reboiler or (iii) the regeneration unit to heat the absorbent solution to be regenerated.

[0037] Typically, the installation may comprise a closed circuit connected to the boiler and to the at least one reboiler such that the water entering the boiler may be condensed steam leaving the at least one reboiler.

[0038] The installation may comprise at least one turbine driving the at least one compressor of the compression unit and / or driving at least one compressor of the heat pump, and the at least one turbine is supplied with high-pressure steam produced by the boiler via a pipe connected to an outlet of the boiler and a pipe connects an outlet of the at least one turbine to an inlet of the at least one reboiler to supply it with low-pressure steam.

[0039] The installation may include one of the following features:

[0040] - the heat distribution section is connected to a steam line condensed connected to an outlet of the at least one reboiler, this pipe being connected to an inlet of the at least one reboiler, or - the heat distribution section is connected to a water supply line of the boiler, the heat pump comprises at least one compressor and at least one turbine driving the at least one compressor, and said heat pump turbine receives a portion of the high pressure steam produced by the boiler via a line connected to an outlet of the boiler, and supplies low pressure steam via another line supplying an inlet of the at least one reboiler.

[0041] The cooling circuit on the pipe of which the heat recovery section can be mounted, can be part of a flue gas cooling system or be a separate, independent closed circuit, equipped with an indirect heat exchanger.

[0042] The installation may in particular comprise one of the following characteristics:

[0043] - a single cooling system comprising at least two cooling stages dissement, a first cooling fluid circuit of the lowest cooling stage, and at least one other cooling fluid circuit the at least one other cooling stage independent of the first circuit, the heat recovery section of the heat pump being connected to the first cooling fluid circuit, - a first cooling system comprising a first cooling fluid circuit, optionally mounted upstream of a second cooling system comprising a second cooling fluid circuit, said cooling system(s) being located upstream of the separation unit with respect to the circulation of the gases, and the heat recovery section of the heat pump is connected to the first cooling fluid circuit.

[0044] The installation may comprise at least one combustion gas supply pipe connected to the exhaust of a gas turbine and / or to a combustion boiler and / or to any other combustion gas production unit, such as an industrial combustion furnace, in particular of a refining unit. Detailed description of the invention

[0045] The terms "comprising" and "comprises" as used herein are synonymous with "including," "includes," or "contains," "containing," and are inclusive or unbounded and do not exclude additional features, elements, or method steps not specified. These terms include embodiments in which they are replaced by "constituting" or "consisting of."

[0046] In the following description, the different embodiments described, and in particular the preferred embodiments of each step, can be combined according to the desired objective.

[0047] In the present description, by “low pressure” steam, also noted BP, is meant steam at an absolute pressure of 0.1 to 1.2 MPa.

[0048] In the present description, by “medium pressure” steam, also noted MP, is meant steam at an absolute pressure of 0.8 to 3 MPA.

[0049] In the present description, by “high pressure” steam, also noted HP, is meant steam at a pressure higher than a “low pressure”, for example at an absolute pressure of 2 to 13.5 MPA. Detailed description of the figures

[0050] Other features and advantages of the invention will emerge from reading the description given below of a particular embodiment of the invention, given for informational purposes but not as a limitation, with reference to the appended drawings in which:

[0051] [Fig. 1] schematically represents a CO2 capture installation combining several embodiments of the invention.

[0052] [Fig.2] schematically represents a CO2 capture installation according to the prior art.

[0053] [Fig. 3] schematically represents a CO2 capture installation according to a first embodiment of the invention.

[0054] [Fig.4] schematically represents a CO2 capture installation according to a second first embodiment of the invention.

[0055] [Fig.5] schematically represents a CO2 capture installation according to a third first embodiment of the invention.

[0056] [Fig.6] schematically represents a CO2 capture installation according to a fourth embodiment of the invention.

[0057] In the figures, the same elements are designated by the same references. CW means cold / chilled water.

[0058] [Fig.l] schematically represents a CO2 capture installation 1 comprising a combustion gas supply pipe 10, a CO2 capture unit 20, a captured CO2 compression unit 30 and a boiler 40. These units are connected to each other for implementing the method according to the invention.

[0059] The combustion gas supply line 10 may be connected to a unit producing combustion gases, in particular to the exhaust of a unit such as a gas turbine and / or to a combustion boiler and / or to an industrial furnace. The gas turbine may be any turbine producing combustion gases (namely any turbine comprising a combustion chamber, internal or external), including combined cycle gas turbines. The combustion boiler may be any boiler producing heat by combustion of a fuel. This fuel may be a gas or any other fuel, preferably a gas. The industrial furnace may be any industrial furnace, in particular forming part of a refinery, for example a furnace of a fluid catalytic cracking unit. A blower B101 ensures the movement of the gases in the line 10.

[0060] The present invention is suitable for various processes in which the combustion gases have a temperature above 50°C, preferably above 100°C and preferably above 130°C, for example from 50 to 180°C, typically from 120°C to 180°C.

[0061] The combustion gas supply step of the method according to the invention can thus be implemented via this supply line 10.

[0062] The CO2 capture unit 20 typically comprises a separation unit 210 and a regeneration unit 220. It also generally comprises a cooling unit or gas quenching unit 200 before they enter the separation unit 210. An example of a capture unit according to the prior art is shown [Fig.2] and its operation described below.

[0063] With reference to [Fig. 2], the combustion gases to be separated are brought to the CO2 capture unit 20 via the pipe 10. They are then cooled in a cooling unit 200 comprising a cooling system 201, typically a gas-liquid contactor 201, in which they are cooled by water circulating in a closed circuit 202. This closed circuit generally comprises a pump 204 and a condenser 206.

[0064] The cooled gases, typically to a temperature of 30°C to 50°C, then enter the separation unit 210, comprising, in particular only, an absorption zone 210. This absorption zone may be part of an absorption column. For this purpose, the absorption columns usually used in this type of process may be used.

[0065] The separation of CO2 contained in the combustion gases is generally carried out by scrubbing the gases with an absorbent solution which retains the CO2 by simple physical dissolution and / or by dissolution after formation of a salt or a thermally unstable complex, by reaction of the CO2 with a basic compound present in the absorbent solution. In practice, the combustion gases containing CO2 are brought into contact, preferably countercurrently, in an absorption zone with the absorbent solution chosen under pressure and temperature conditions such that the absorbent solution fixes almost all of the CO2. Suitable pressure and temperature conditions are, for example, absolute pressures ranging from 0.1 to 12 MPa and temperatures of the order of 30 to 110 °C.

[0066] The absorbent solution used to fix the absorbable gaseous compounds, and in particular CO2, may be any of the absorbent solutions known in the art for this purpose. This absorbent solution may in particular consist of an organic solvent, such as amines, possibly containing antioxidant additives. Most often, the absorbent solution consists of an aqueous solution of a basic compound fixing CO2 in the form of complexes decomposable by heating, this basic aqueous solution being for example an aqueous solution of potassium phosphate or potassium carbonate, an aqueous solution of an amino acid such as glycine, and in particular an aqueous solution of a primary, secondary, or tertiary alkanolamine such as in particular monoethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, diisopropanolamine.

[0067] The combustion gases depleted in CO2 exit at the top of the absorption zone 210 via an upper pipe 212 and, if necessary, can then be directed towards a soda scrubber in which the last traces of acid compounds that they may still contain are retained (not shown).

[0068] The absorbent solution to be regenerated, that is to say the absorbent solution loaded with CO2 withdrawn from the separation unit 210, and in particular from the absorption zone thereof, via a lower pipe 214 equipped with a pump 215, is brought to the regeneration unit 220, comprising, in particular only, a regeneration zone 220. This regeneration zone may be part of a regeneration column. For this purpose, the regeneration columns usually used in this type of process may be used.

[0069] In this regeneration zone 220, the absorbent solution to be regenerated is kept boiling and under pressure. The heat necessary to maintain this boiling is provided by reboiling the absorbent solution contained in the regeneration zone, that is to say by indirect heat exchange between a portion of the solution to be regenerated located in the lower half of the regeneration zone and a hot fluid at an appropriate temperature, generally saturated water vapor. This reboiling is carried out in one or more reboilers 222, here only one.

[0070] During regeneration, the CO2 contained in the absorbent solution to be regenerated, maintained at boiling point, is released and stripped by the vapors of the absorbent solution. The CO2 leaves the regeneration zone at the top via a pipe 224 and is evacuated through a condenser system 226 which brings back into the regeneration zone 220 the liquid phase resulting from the condensation of the vapors of the absorbent solution entrained from the regeneration zone with the CO2. The CO2 is then compressed in the compression unit 30, represented here schematically by a single compressor but which may comprise one or more stages of compressors, possibly subjected to dehydration 34, and is evacuated from the compression unit 30 via the pipe 32.

[0071] A boiler 40 makes it possible to produce steam ensuring the reboiling of the absorbent solution to be regenerated, the steam circulating in a closed circuit 42. This circuit 42 typically comprises a pump 44 for the circulation of the water, the path of which is as follows: the boiler 40 produces water vapor which is sent to the reboiler 222 in which calories are transferred to the absorbent solution to be regenerated, which causes the condensation of the water vapor. This condensed water vapor leaving the reboiler is returned to the boiler 40 thanks to the pump 44.

[0072] At the bottom of the regeneration zone 220, the hot regenerated absorbent solution is withdrawn and this regenerated solution is recycled to the absorption zone via a pipe 228 equipped with a pump 229, after having used part of the calories of this solution to heat, by indirect heat exchange, here via an exchanger 230 (also called an economizer), with the solution to be regenerated withdrawn from the absorption zone before its introduction into the regeneration zone 220. A condenser 231 makes it possible to further cool the regenerated absorbent solution before its introduction into the absorption zone 210.

[0073] According to the invention, as shown [Fig.l] and in Figures 3 to 6, the CO2 capture installation 1, comprising a capture unit 20, here similar to that described with reference to [Fig.2], further comprises a heat pump 50 comprising a heat recovery section 52 and a heat distribution section 54 arranged so as to reduce the energy consumption necessary to operate the capture unit 20, and in particular the regeneration unit 220 of this capture unit.

[0074] The invention is however not limited to a particular capture unit, in particular of the type described with reference to [Fig.2], and can be applied to any existing capture unit to produce all or part of the steam necessary for the regeneration of the absorbent solution or for the operation of the capture unit.

[0075] Typically, each heat recovery 52 and distribution 54 section comprises at least one indirect heat exchanger 520, 540 respectively, the heat pump further comprising a circuit 51 in which a working fluid circulates, and passing through the recovery 52 and distribution 54 sections. The heat pump 50 also usually comprises at least one compressor 56, only one in the figures, and at least one expansion device 58 (calibrated orifice, electronic expansion valve, turbine, semi-closed valve, etc.), only one in the figures. The compressor(s) 56 may be driven by an electric motor 57 (see [Fig.4]) or by a turbine 59 (figures 3, 5, 6). In the present invention, it will be considered that the recovery section 52 of the heat pump comprises only the at least one indirect heat exchanger 520, the other elements of the heat pump, in particular the at least one indirect heat exchanger 540, the compressor(s) 56 and the at least one expansion device 58, are part of the heat distribution section 54 of the heat pump.These different elements are not represented [Fig.l] for the sake of simplification. The working fluid can be water, a hydrocarbon, in particular an alkane such as butane or cyclopentane, a refrigerant such as a hydrofluoroolefin (called HFO), or a hydrochlorofluoroolefin (called HCFO), a gas such as CO2, NH3, or other.

[0076] According to the invention, the heat pump 50 recovers via the heat recovery section 52 a portion of the heat from the combustion gases supplied upstream of the capture unit 20, and in particular from the separation unit 210. In addition, the heat pump 50 distributes, via its heat distribution section 54, heat used (i) to preheat water entering the boiler 40, or (ii) to produce a portion of the water vapor supplying the at least one reboiler 222 or (iii) to heat the absorbent solution to be regenerated in the regeneration unit 220.

[0077] Different possible embodiments for the recovery of heat by the pump and for the use of the heat distributed by the heat pump are brought together [Fig.l], in which the following references designate:

[0078] B: flue gas heat recovery section which transfers (directly or indirectly) the heat from the flue gases to the heat recovery section 52 of the heat pump 50,

[0079] 50: heat pump 50 (also noted “PAC” 50) receiving the heat (6) coming from from the hot source, electricity (Ul), a cold fluid to be heated and producing a heated hot fluid (11),

[0080] 10: combustion gas supply line,

[0081] 2: conduit in which the combustion gases circulate, cooled by the section of heat recovery,

[0082] 3: conduit through which the combustion gases depleted in CO2 are evacuated,

[0083] 4: pipe in which the CO2 leaving the capture unit 20 circulates,

[0084] 5: pipe in which the compressed CO2 leaving the compression unit circulates,

[0085] 7: low pressure steam required for the regeneration unit 220 of the unit of capture 20,

[0086] 8: low pressure steam produced by at least one turbine driving the at least one compressor of the heat distribution section of the heat pump, when such a turbine is present,

[0087] 9: condensed steam (from the reboiler of the regeneration unit of the unit capture) heated by its passage through the heat distribution section,

[0088] 11: low pressure steam generated by the heat pump,

[0089] 12: high pressure steam produced by the boiler 40 when the latter is a high pressure boiler, this high pressure steam supplying at least one turbine driving at least one compressor of the heat pump 50, when such a turbine is present,

[0090] 13: low pressure steam produced by the boiler 40 when the latter is a low pressure boiler,

[0091] 14: high pressure steam produced by the boiler when the boiler is a high pressure boiler, this high pressure steam supplying at least one turbine driving at least one compressor of the compression unit when such a turbine is present,

[0092] 15: low pressure steam exiting the at least one turbine of the control unit pressure when present,

[0093] 16: combustion gases emitted by the boiler 40 when it is in combustion, these gases being returned to line 10 in order to capture the CO2 they contain and reduce the CO2 footprint of the boiler and the steam it produces,

[0094] 17: condensed steam leaving the reboiler and returned to boiler 40,

[0095] U1: electricity supplying the heat pump compressor motor or the boiler when it is electric,

[0096] U2: fuel supplying the boiler when it is burning, for example gas,

[0097] U3: imported steam (optional),

[0098] U4: cooling water (for the cooling system(s) of the capture unit.

[0099] Section B receives calories, typically via an exchanger with a heat source, from flue gases from which CO2 is to be captured, and optionally from another fatal heat source available on the nearby site. The main heat input is flue gases from upstream units. The cooled flue gases 2 are then exported to the capture unit 20. The extracted heat is transferred to the heat distribution section 54 of the heat pump.

[0100] Heat recovery at section B1 can be done in different ways ways, for example in a heat exchanger with the combustion gas, in a dedicated enclosure where water serves as a cooling fluid by direct contact and where the heat is recovered from the water to the heat pump, or via an enclosure of a direct contact cooling unit usually present in a capture unit 20, or even via a dedicated cooling circuit receiving calories from the combustion gases. These different embodiments are described below with reference to Figures 3 to 6.

[0101] The CO2 capture unit 20 is typically a capture unit using an absorbent solution of the type described with reference to [Fig. 2]. This unit generally comprises a quenching unit (for example in the form of a direct contact cooler, DCC (Direct Contact Cooler)) to cool the combustion gases. The cooled combustion gases saturated with water are then sent to the absorption unit where the absorbent solution, possibly regenerated, captures the CO2. The CO2-depleted combustion gases (3) are then sent to the atmosphere. The absorbent solution to be regenerated is sent to the regeneration unit to recover the captured CO2 (4) and regenerate the solution. This operation requires heat which is normally used in the form of steam. This steam can be supplied either by the heat pump 50 via line (11), or by the boiler 40 via line (12) and / or by external sources U4.

[0102] The heat recovery section 52 may be integrated into the quenching unit of the capture unit 20. This makes it possible to increase the heat transfer coefficient and to reduce the size of the heat exchangers. In this case, the quenching unit may comprise a dedicated cooling system with a higher temperature which makes it possible to minimize the temperature rise that the heat pump must achieve and thus to maximize the Coefficient of Performance (COP) of the heat pump, as described below with reference to Figures 4 and 6. The cooling fluid of this dedicated cooling system may have a temperature above 60°C, preferably above 70°C, and preferably above 80°C, typically from 60°C to 90°C.

[0103] The heat distribution section 54 of the heat pump receives heat from the combustion gases, electricity (Ul) and / or high pressure steam (12) for the rotating equipment (turbine(s) possibly present to drive the compressor(s) of the heat pump). The heat produced by this distribution section 54 may be HP steam which can be used for the rotating equipment (turbines) and then for the regeneration of the absorbent solution (8), or preferably LP steam (11) which will be used for the regeneration of the absorbent solution, or heat integrated into the boiler to reduce its fuel consumption, typically natural gas, or reduce its electrical consumption in the case of an electric boiler. The heat distribution section 54 can be integrated in different forms with the boiler 40, either as a preheater or intercooler in the boiler (as described with reference to Figures 3, 5, 6), or as a parallel unit to produce heat / steam to reduce the operation of the boiler (as described with reference to [Fig. 4]). In this case, the steam produced will be used mainly for the regeneration of the absorbent solution in the capture unit 20. A possible arrangement also consists of using the mechanical energy produced by the expansion of the HP steam (14) produced by the boiler to drive a compressor or a pump of the CO2 compression unit 30 using a turbocharger or a turbopump system. However, this arrangement may, in certain cases, lead to implementation difficulties.The operation of the boiler 40 is optimal when it is as close as possible to the capture unit 20, and in particular to the regeneration unit. When the compression unit 30 cannot be implemented next to the capture unit 20, due to land availability reasons, which can often occur in projects involving existing refineries, then an HP steam line or a CO2 flow before / during / after compression must be considered, which entails significant costs. On the other hand, the heat distribution section 54 is preferably close to the capture unit 20, since it produces the steam for the regeneration unit.Therefore, a configuration in which a heat pump 50 provides part of the regeneration energy in the form of steam in addition to a gas boiler 40 offers the opportunity to implement a direct mechanical drive with a reduced cost compared to a configuration without a heat pump.

[0104] The boiler 40 produces the heat necessary for the regeneration of the absorbent solution, and possibly the energy required for the rotating equipment. The steam necessary for the regeneration of the absorbent solution is low pressure steam (7), e.g. at an absolute pressure of 0.2 to 1.2 MPa, preferably 0.4 to 0.6 MPa. In one embodiment of the present invention, this boiler produces HP steam, e.g. at an absolute pressure greater than 2 MPa, preferably greater than 5 MPa, e.g. 4 MPa to 13.5 MPa. This steam will first be used to rotate the rotating CO2 compression equipment (14) and the heat pump (12). The steam at the outlet of the turbines will be in the state of low pressure steam (15) (8). This low pressure steam will then be used for the regeneration of the absorbent solution. Another possibility is to use LP or MP steam to drive the heat pump's rotating equipment.MP steam can be produced and used for regeneration of the absorbent solution. For this purpose, LP steam can be sent to a compression section to produce a . MP steam, for example a water vapor compression system, before sending it to the reboiler of the regeneration unit. This MP steam can also be used for the rotation of the rotating equipment of the heat pump.

[0105] The boiler 40 can be decarbonized either by the capture unit 20 or by using an oxy-combustion system where the air is replaced by oxygen. In this case, the output will be rich in CO2 and H2O and can be sent to the compression unit 30 directly, possibly after a pretreatment step depending on the quality of the fuel. In another variant, the fuel of the boiler can be entirely or partially replaced by decarbonized H2. In these cases, the implementation of the heat pump according to the invention makes it possible to reduce operating costs. The presence of a boiler in the installation improves the overall availability and flexibility of the installation thanks to the fact that it offers an alternative source of steam. This operating case is potentially at a lower steam rate because the heat pump will not operate entirely or partially.

[0106] The CO2 compression unit 30 typically comprises compressors and possibly pumps. These devices can advantageously be partially or totally driven by turbines which use the HP steam (14) produced by the boiler and / or the heat pump as described above. The steam is not entirely exploited by the turbines and leaves them in the form of LP steam (15) and possibly MP steam (not shown in the diagram). It should be noted that the compression of the CO2 generates heat which can be used as an additional heat source which can be recovered by the recovery section of the heat pump.

[0107] The advantages of this invention are as follows:

[0108] - Reduction of the overall consumption of electricity and fuel supplying the boiler (typically natural gas) in a CO2 capture unit thanks to the additional heat recovered by the heat pump and the use of high-energy steam for the compressors and low-energy low-pressure steam from the turbine for regeneration of the absorbent solution. This reduces the carbon and energy footprint of the CO2 capture unit by absorbent solution.

[0109] - The use of a heat pump makes it possible to reduce the temperature of the gases combustion below the original temperature. This reduces the cooling water requirements of the quenching unit and therefore saves CAPEX and OPEX.

[0110] - It is possible to optimize the size of the heat recovery units in the case combined cycle turbines or steam turbines with heat recovery unit. In this case, thanks to the fact that the heat pump allows to recover the energy from the flue gases, the outlet temperature of a HRSG (Heat Recovery Steam Generator) unit can be adjusted to optimize the overall heat transfer surfaces and therefore reduce the size and cost of the HRSG unit.

[0111] - The use of low-carbon steam makes it possible to reduce emissions that would have were induced by the use of electricity.

[0112] Note that the boiler used in the present invention may be an electric boiler or a combustion boiler or an oxy-combustion boiler.

[0113] Exemplary embodiments of the different embodiments of heat recovery via the heat recovery section 52 are described below with reference to FIGS. 3 to 6.

[0114] Exemplary embodiments of different embodiments of the heat distribution by the heat pump are also described below with reference to Figures 3 to 6.

[0115] These different embodiments of heat recovery and heat distribution can be combined with each other depending on the desired objective.

[0116] In these different examples, the compression unit 30 comprises at least one turbine 36 for driving the compressor(s) and pump(s) of the compression unit. This turbine 36 is driven by HP steam produced by the boiler 40. At the outlet of the turbine 36, the LP steam is returned to the reboiler of the capture unit. Although this is not preferred, the boiler 40 can alternatively produce only LP steam which is then sent directly to the reboiler. The turbine 36 is then absent and replaced by a motor (as shown [Fig.2]) or powered by HP steam from another source.

[0117] Heat recovery from combustion gases by heat pump

[0118] In a first embodiment shown [Fig.3], the heat exchanger 520 of the heat recovery section 52 of the heat pump is mounted directly on the supply line 10 upstream of the separation unit 210, and in particular upstream of the cooling unit 200 and its contactor 201.

[0119] In a second embodiment shown in dotted lines [Fig. 3], the heat exchanger 520' of the heat recovery section 52 of the heat pump is mounted on a pipe of a cooling circuit 202' instead of being mounted directly on the combustion gas pipe 10 (in this second embodiment, 520 is omitted and replaced by 520', the circuit 51 passing only through 520'). This combustion gas cooling circuit 202' is located upstream of the separation unit 210 with respect to the circulation of the gases, preferably upstream of any other cooling system. This cooling circuit 202' forms a closed loop in which a hot fluid circulates, typically water, receiving the heat from combustion fumes by heat transfer via an indirect heat exchanger 205 mounted on the flue gas pipe 10.

[0120] In a third embodiment shown in Figures 4-6, the heat exchanger 520 of the heat recovery section of the heat pump is mounted on a pipe of a cooling circuit 202a of a system 201 or 203 for cooling the combustion gases located upstream of the separation unit 210 with respect to the circulation of the gases. This heat recovery can be carried out according to two variants.

[0121] In the variant shown in Figures 4 and 6, the cooling unit 200 of the capture unit 20 comprises a first cooling system 201a and a second cooling system 201b mounted in series upstream of the separation unit, each of these cooling systems comprising a cooling circuit, 202a and 202b respectively, each equipped with a pump 204a, 204b. The cooling circuit 202b of the second cooling system 201b further comprises a condenser 206. In this variant, the heat exchanger 520 of the heat pump is mounted on the cooling circuit 201a of the first cooling system 201, at the outlet of the cooling system relative to the direction of circulation of the cooling fluid and thus serves as a condenser.Thus, the cooling fluid heated by its passage in the first cooling system 201a transfers calories to the working fluid of the heat pump via the heat exchanger 520, which causes it to condense, then is returned to the cooling system 201a.

[0122] In the variant shown [Fig. 5], the cooling unit 200 of the capture unit 20 comprises a single cooling system 201 upstream of the separation unit 210. This cooling system 201 here comprises two cooling stages, a lower stage 203a comprising a first cooling circuit 202a equipped with a pump 204a and an upper stage 203b comprising another cooling circuit 202b equipped with a pump 204b and a condenser 206, separate from the first cooling circuit. Note that the invention is not limited by the number of cooling stages of the single cooling system, which could comprise three or more cooling stages. It will then be possible to provide a single cooling circuit for the upper stages. In the variant of [Fig.5], the heat exchanger 520 of the heat recovery section is mounted on the first cooling circuit 202a of the lower stage of the cooling system, at the outlet of the cooling system 201, relative to the direction of circulation of the cooling fluid and thus serves to condense the latter at the outlet of the first cooling stage 203a. Thus, the cooling fluid heated by its passage in the first stage 203a of the cooling system 201. transfers calories to the working fluid of the heat pump via the heat exchanger 520, which causes it to condense, and is then returned to the first stage 203a of the cooling system 201. In general, the combustion gases enter the cooling system 201 through the lowest stage and circulate from bottom to top.

[0123] Typically, in the various embodiments, the cooling fluids are water, possibly comprising additives capable of reducing corrosion, and the cooling system is a multi-stage gas-liquid contactor or “direct contact cooler”, which may comprise one or more beds each comprising one or more internal packings, structured or not. The invention is however not limited to this type of cooling system or cooling fluid and any cooling system usually used in CO2 capture installations may be used.

[0124] The second and third embodiments make it possible to reduce the dimensions of the heat recovery section, and in particular of the heat exchanger, of the heat pump compared to the first embodiment.

[0125] Distribution of heat produced by the heat pump

[0126] In a first embodiment shown in Figures 3, 5 and 6, the heat distributed by the heat distribution section can be used to preheat the water entering the boiler 40.

[0127] In the embodiments shown in these figures, the installation 1 comprises a closed circuit 42 in which the water follows the following path: the water leaving the reboiler 222 is heated by passing through the heat exchanger 540 of the heat distribution section of the heat pump, then enters the boiler 40 in which it is vaporized, here at high pressure, the high pressure steam produced by the boiler 40 then feeds a turbine 36 of the compression unit in order to drive the compressor thereof, and leaves the turbine 36 at low pressure before entering the reboiler 222 again. This closed circuit typically comprises a pump 44 to ensure the circulation of the water, generally positioned upstream of the inlet of the boiler 40, between the outlet of the reboiler 222 and the inlet of the boiler 40.

[0128] In the example, the heat exchanger 540 is advantageously arranged between the pump 44 and the inlet of the boiler 40.

[0129] In a variant not shown, the boiler 40 can produce LP steam. In this case, the low pressure steam from the boiler is sent directly to the reboiler 222. The compressor of the compression unit is then not driven by a turbine, or the steam necessary for the operation of the turbine is produced elsewhere. This variant is not preferred, however.

[0130] In all cases, preheating the water entering the boiler 40 makes it possible to reduce the amount of energy to be supplied by the boiler to produce steam (low or high pressure). This embodiment is particularly advantageous when the boiler is electric.

[0131] In a second embodiment shown [Fig.4], the heat distributed by the heat distribution section via the heat exchanger 540 is used to produce steam.

[0132] In this embodiment, the installation also comprises the closed circuit 42 described with reference to the first embodiment. It further comprises a bypass pipe 46, one end of which is connected to the closed circuit 42 at the outlet of the reboiler 222 and upstream of the boiler 40, and the other end of which is connected to the closed circuit 42 at the inlet of the reboiler 222 and downstream of the turbine 36 (and therefore of the boiler 40). Note that this embodiment can also be applied in the case of a boiler 40 producing low-pressure steam, the closed circuit 42 then not passing through the turbine 36.

[0133] This bypass pipe 46 may further comprise a pump 47 for circulating the condensed steam leaving the reboiler 222.

[0134] This embodiment makes it possible to reduce the size of the boiler since only part of the water circulating in the closed circuit circulates through the boiler.

[0135] Finally, in a variant not shown, it will be possible to provide a transfer of calories from the working fluid of the heat pump to the absorbent solution to be regenerated via the heat exchanger 540 of the distribution section of the heat pump.

[0136] The different modes of heat recovery by the heat pump and heat distribution can be combined depending on the desired objective. Figures 3 to 6 correspond to some of these combinations.

[0137] Furthermore, whatever the embodiment, the at least one compressor 56 of the heat pump can be driven by a motor 57 ([Fig.4]) or by a turbine 58 ([Fig.3], 5, 6). In the latter case, it is particularly advantageous to supply the turbine(s) 58 with high pressure steam produced by the boiler 40, the LP steam leaving the turbine(s) 58 then being returned to the inlet of the reboiler 222, as shown in these figures.

[0138] Furthermore, in the various embodiments, when the boiler 40 is a combustion boiler, the combustion gases from the boiler can be sent to the capture unit 20 via a pipe 60, here equipped with a fan 62.

[0139] The following description presents several non-limiting examples of application of the invention.

[0140]

[0141]

[0142]

[0143] Examples Example 1 [Fig.3] illustrates an example of application of the invention to the flue gases of a heat recovery steam generator (HRSG) downstream of a gas turbine in a 200 MWe LNG (Liquefied Natural Gas) plant. The composition of the flue gases is shown in Table 1. [Table 1] Composition of combustion gases (molar %) n2 73.41% co2 3.54% Ar 0.88% o2 12.7% h2o 9.47%

[0144] The flue gases flowing in line 10 have a flow rate of 1,400 t / h and a temperature of 135 °C. The fan B101 increases their pressure to 0.1 MPa (1.1 bar) (absolute pressure). Heat is directly recovered from the gases through the heat exchanger 520. Considering a case where the flue gases are cooled in the exchanger 520 from 135 to 110 °C, 10.7 MW are recovered. It is possible to further reduce the temperature to 90 °C. This allows 19.3 MWth of energy to be recovered. The recovered energy can be transferred to the condensation water upstream of the boiler via the heat exchanger 540, as illustrated [Fig. 3].

[0145] Alternatively, this heat can also be used to produce steam by the heat pump 50, preferably low pressure steam (embodiment of [Fig.4]). This will produce 33 t / h of steam at an absolute pressure of 0.5 MPa (4.5 bar gauge) and 166°C. 95 t / h of steam will then be produced by the boiler at an absolute pressure of 5.5 MPa (45 bar gauge) to run the CO2 compression turbine and the heat pump compressor. This reduces the amount of imported natural gas for the boiler by 24%. The use of steam for rotating equipment will save 6.13 MWe. The CO2 is delivered at a pressure of 16.5 MPa. The natural gas savings associated with this case are 1942 NmVh.

[0146] In the example of [Fig.3], the heat recovered from the flue gases via the heat pump is used for the production of steam which, in turn, is used to drive the rotating equipment used in the heat pump and / or the compression of CO2. The recovered energy is converted into steam, allowing it to be used as kinetic and thermal energy. The flue gases from the boiler are also sent to the CO2 capture plant to capture CO2 and reduce thus the overall CO2 footprint of the system.

[0147] The use of this synergy makes it possible to improve the energy performance of the system thanks to the fact that the total quantity of steam produced is not modified, but only its quality is improved. This makes it possible to considerably reduce the overall energy footprint of the installation and to reduce electricity imports. The capture of CO2 at the boiler outlet makes it possible to have a low overall CO2 footprint because the steam produced has a low carbon footprint thanks to the synergy between CO2 capture and the use of the heat pump. This makes it possible to achieve an overall rate of CO2 avoided greater than 85%, or even greater than 90%.

[0148] Example 2

[0149] This example corresponds to the diagram shown [Fig.6] and has similar energy performances to Example 1. The main difference lies in the way heat is extracted from the flue gases. Heat recovery from flue gases requires relatively large heat exchangers. In order to reduce the size and costs, an alternative is proposed in this example. A dedicated flue gas cooling system 201a with water as the heat transfer fluid in direct contact is added. The water in direct contact with the flue gases recovers its energy and cools the flue gases at the same time. The heat required by the heat pump is then recovered from the recirculating water whose temperature is above 70°C, preferably 90°C. Excess water from potential condensation is removed from the system.The additional advantage of this configuration is that by installing it near the CO2 source, it allows to reduce its temperature and therefore to reduce the volumetric flow rate of the flue gases. This allows to reduce the flue gas piping system and therefore to reduce the capital expenditure. The B101 fan can be installed after or before this cooling system 201a.

[0150] Another solution is to integrate this heat recovery section into the cooling system which is normally present upstream of the absorption unit, as shown [Fig.5]. A cooling stage 203a comprising its own water loop 202a with a temperature of 90°C is then provided in the bottom. The heat pump then recovers the heat from this water loop. This provides an even higher heat transfer capacity than the embodiment of [Fig.6] and allows the size of the heat exchanger of the heat pump to be reduced, thus saving investment costs. An additional heat exchanger can be added from the cooling water loop to better control the water temperature and the overall heat balance of the system.

[0151] This concept can be used to electrify the CO2 capture unit in case using electricity in the heat pump and recovering the energy at a higher temperature in order to be able to produce HP steam with a heat pump sized for this purpose.

Claims

Claims

1. A method for capturing CO2 present in combustion gases, said method comprising: - a step of supplying combustion gases containing CO2 to be separated, - a step of separating the supplied combustion gases during which the supplied combustion gases are brought into contact with an absorbent solution, this step producing CO2-depleted gases and a CO2-enriched absorbent solution, - a step of regenerating the CO2-enriched absorbent solution during which the CO2 it contains is released by heating the solution by means of at least one reboiler (222) supplied with low-pressure steam, in particular at a pressure of 0.1 to 1.2 MPa, preferably 0.4 to 0.6 MPa, - a step of compressing the CO2 released during the regeneration step by means of at least one compressor,- characterized in that a portion of the heat of the supplied combustion gases is recovered by a heat pump (50) upstream of the separation step and in that said heat pump distributes heat used (i) to preheat water entering a boiler (40) producing steam supplying the at least one reboiler (222), (ii) to produce a portion of the water vapor supplying the at least one reboiler (222) or (iii) to heat the absorbent solution to be regenerated in the regeneration step.,

2. Method according to claim 1, characterized in that the water entering the boiler (40) is condensed steam leaving the at least one reboiler (222).

3. Method according to claim 1 or 2, characterized in that: - the boiler (40) produces steam at a so-called "high pressure" pressure higher than the low pressure, in particular at an absolute pressure of 2 to 13.5 MPa, preferably 4 to 9 MPa, and - the boiler (40) produces high pressure steam which feeds at least one turbine (36) driving the at least one compressor of the compression stage and the low pressure steam leaving the at least one turbine (36) feeds the at least one reboiler (222).

4. Method according to any one of claims 1 to 3, characterized in that: - the heat pump (50) distributes transferred heat, in particular via a heat distribution section (54), to the water entering the boiler (40), - the boiler (40) produces so-called "high pressure" steam higher than the low pressure, and: - the heat pump (40) comprises at least one compressor (56) driven by at least one turbine (59), and - said heat pump turbine (59) is driven by a portion of the high pressure steam produced by the boiler and the low pressure steam leaving the heat pump turbine (59) feeds the at least one reboiler (222).

5. Method according to any one of claims 1 to 3, characterized in that the heat pump (50) distributes transferred heat, in particular via a heat distribution section (54), to a portion of condensed vapor leaving the at least one reboiler (222) to vaporize it again and return it to the inlet of the at least one reboiler (222).

6. Method according to any one of claims 1 to 5, characterized in that the heat pump (50) recovers at least part of the heat from the combustion gases supplied by heat transfer via a heat recovery section (52) in which circulates said combustion gases or a hot fluid having received by heat transfer at least part of the heat from the combustion gases.

7. Method according to any one of claims 1 to 6, characterized in that it comprises, upstream of the separation step with respect to the circulation of the gases: - a step of cooling the combustion gases supplied, this cooling step being implemented in a cooling system in which the combustion gases supplied are cooled by a fluid, and in that: - the heat pump (50) recovers part of the heat from the combustion gases supplied by heat transfer via a heat recovery section (52) in which the fluid heated by the combustion gases supplied during the cooling step circulates.

8. Method according to claim 7, characterized in that it comprises: - a second cooling step implemented after the first cooling stage and before the separation stage, this second cooling stage being implemented in a second cooling system in which the supplied combustion gases are further cooled by a fluid.

9. Method according to claim 7, characterized in that it comprises: - a single cooling step implemented in a single cooling system (201), and - the single cooling system comprises at least two cooling stages (203a, 203b), the combustion gases supplied passing through the lowest cooling stage being cooled by a fluid circuit independent of at least one other fluid circuit cooling the at least one other cooling stage, and in that - the heat pump (50) recovers part of the heat from the combustion gases supplied by heat transfer, via a heat recovery section in which the fluid heated by the combustion gases from the lowest cooling stage circulates.

10. Installation (1) for capturing CO2 present in combustion gases, comprising: - a pipe (10) for supplying combustion gas containing CO2 to be separated, - a separation unit (210) connected to the supply line (10) in which the supplied combustion gases are brought into contact with an absorbent solution, this unit (210) producing supplied combustion gases depleted in CO2 and an absorbent solution enriched in CO2, - a regeneration unit (220) connected to the separation unit (210) and receiving the absorbent solution enriched in CO2, in which the CO2 contained in the absorbent solution is released by heating the solution by means of at least one reboiler (222) supplied with low pressure water vapor, - a CO2 compression unit (30) connected to the regeneration unit and receiving the released CO2, and comprising at least one compressor, - characterized in that it further comprises a heat pump (50) comprising a heat recovery section (52) and a heat distribution section (54), and: - the heat recovery section (52) is (a) mounted on the supply line (10) upstream of the separation unit (210) or (b) mounted on a line of a cooling circuit (202', 202, 202a) of the combustion gases located upstream of the separation unit (210) with respect to the circulation of the gases, - the heat distribution section (54) is mounted (i) on a water supply line of a boiler (40) producing steam supplying the at least one reboiler (222), (ii) on a water vapor line supplying the at least one reboiler (222), or (iii) the regeneration unit to heat the absorbent solution to be regenerated.

11. Installation (1) according to claim 10, characterized in that it comprises at least one turbine (36) driving the at least one compressor of the compression unit (30) and in that the at least one turbine (36) is supplied with high pressure steam produced by the boiler (40) via a pipe connected to an outlet of the boiler and a pipe connects an outlet of the at least one turbine (36) to an inlet of the at least one reboiler (222) to supply it with low pressure steam.

12. Installation (1) according to claim 10 or 11, characterized in that: - the heat distribution section (54) is connected to a condensed steam pipe (46) connected to an outlet of the at least one reboiler, this pipe (46) being connected to an inlet of the at least one reboiler, or - the heat distribution section (54) is connected to a water supply pipe of the boiler (40), the heat pump (50) comprises at least one compressor (56) and at least one turbine (59) driving the at least one compressor, and said heat pump turbine (59) receives a portion of the high-pressure steam produced by the boiler (40) via a pipe connected to an outlet of the boiler, and supplies low-pressure steam via another pipe supplying an inlet of the at least one reboiler (222).

13. Installation (1) according to any one of claims 10 to 12, comprising one of the following characteristics: - a single cooling system (201) comprising at least two cooling stages (203a, 203b), a first cooling fluid circuit (202a) of the lowest cooling stage, and at least one other cooling fluid circuit (202b) the at least one other cooling stage independent of the first circuit, the heat recovery section (52) of the heat pump being connected to the first cooling fluid circuit (202a), - a first cooling system (201a) comprising a first cooling fluid circuit (202a), optionally mounted upstream of a second cooling system (201b) comprising a second cooling fluid circuit (202b), said cooling system(s) being located upstream of the separation unit with respect to the circulation of the gases, and the heat recovery section (52) of the heat pump is connected to the first cooling fluid circuit (202a).

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