Process and installation for CO2 separation by partial condensation and / or distillation and by absorption

Abstract

Title: Method and installation for separating CO2 by partial condensation and / or distillation and by absorption A first gas (19) containing CO2 is separated in a CO2 absorption capture unit (21) using a chemical solvent producing a first stream (17) enriched in CO2 compared to the first gas, a second gas (9) containing CO2 is compressed in a first compressor (C1), cooled in a heat exchanger and separated in a partial condensation and / or distillation unit (13) producing a second stream (15) enriched in CO2 compared to the second gas, and heat generated by the compression of the second gas in the first compressor is used to regenerate the chemical solvent of the capture unit. Abstract figure: Fig. 1

Description

Title of the invention: Process and installation for separating CO2 by partial condensation and / or distillation and by absorption

[0001] The present invention relates to a method and an installation for separating CO2 by partial condensation and / or distillation and by absorption.

[0002] When compressing the flow to be separated by partial condensation and / or distillation, waste heat is generated. The same applies when compressing the CO2-rich gas produced by partial condensation and / or distillation. The flow to be separated may, for example, contain at least 15 mol% CO2 (for example, the fumes from a combustion) or at least 40 mol% CO2 (for example, the waste from a PSA H2).

[0003] These compressions are carried out by means of centrifugal compressors, consisting of several compression stages (typically between 4 and 8), between which refrigerants make it possible to cool the gas at the outlet of each compression stage (which is typically between 80 and 120°C) by means of heat exchange with a cooling water system. This heat is then dissipated, typically to the atmosphere, by means of a cooling tower (=semi-open circuit) or air / water exchangers (=closed circuit).

[0004] An aim of the present invention is to use this heat in a CO2 capture process by absorption using a solvent. The CO2 capture units by chemical solvent consist in particular of an absorber where the CO2 is absorbed by a solvent, and a regenerator where the solvent loaded with CO2 is thermally regenerated by supplying heat at a typical level of the order of 110-120°C. A flow of water vapor is generally used for this purpose.

[0005] Generally, when considering CO2 capture, a single CO2 capture technology is chosen, without attempting to integrate multiple capture technologies. In the case of the invention, a partial condensation and / or distillation separation unit and an absorption unit are used to capture CO2, without using the partial condensation and / or distillation separation unit to treat the CO2-enriched gas produced by the absorption unit. These units can produce CO2-rich products that are combined. They can be fed with CO2-containing gases from a single source, the gases having the same composition or different compositions, depending on the type of unit. Otherwise, they can be fed by independent sources.

[0006] According to an object of the invention, there is provided a process for separating CO2 by partial condensation and / or distillation and by absorption in which a. a first gas containing CO2 and at least one lighter component and / or heavier than CO2 is separated in a CO2 capture unit by absorption using a chemical solvent producing a first stream enriched in CO2 compared to the first gas b. A second gas containing CO2 and at least one component lighter and / or heavier than CO2, originating from a source other than the capture unit, is compressed in a first compressor, cooled in a heat exchanger and separated in a partial condensation and / or distillation unit comprising at least one phase separator and / or at least one distillation column producing a second stream enriched in CO2 relative to the second gas, the second stream being optionally compressed in a second compressor and c. Heat generated by the compression of the second gas in the first compressor and possibly by the compression of the second stream in the second compressor is used to regenerate the chemical solvent in the capture unit.

[0007] According to other optional features: • at least one component lighter than CO2 is chosen from the group nitrogen, oxygen, carbon monoxide, hydrogen, methane. • at least one component heavier than CO2 is chosen from the group NO2, mercury, hydrocarbon. • the temperature level of the recovered heat is greater than 60°C, preferably greater than 80°C and even greater than 90°C, or even greater than 110°C. • the first compressor and / or the second compressor comprises several stages, the compressed gas not being cooled by an external refrigerant between at least two consecutive stages and / or downstream of a last stage. • the temperature at the inlet of a stage of the first compressor and / or the second compressor is adjusted to reach a minimum temperature level at the outlet of the compressor. • a heat pump ensures the transfer of heat from the first compressor and possibly from the second compressor, the compression heat being at a level below 110°C, preferably below 100°C and the heat sent to the regenerator of the capture unit using a solvent being at a level above 110°C, preferably above 120°C. • the first gas contains less CO2 than the second gas. • the first gas consists of fumes from at least one reforming unit producing a synthesis gas. • the source of the second gas is at least one adsorption or permeation. • the source of the second gas is at least one adsorption or permeation unit which separates a gas produced by treating the synthesis gas from at least one reforming unit to separate the hydrogen it contains, the second gas being a hydrogen-depleted and CO2-enriched gas produced by the adsorption or permeation unit. • the first gas consists of fumes from at least one reforming unit producing a synthesis gas and the source of the second gas is at least one adsorption or permeation unit which separates a gas produced by treating the synthesis gas to separate the hydrogen it contains, the second gas being a gas depleted in hydrogen and enriched in CO2 produced by the adsorption or permeation unit. • the first and second gases come from the same reforming unit. • the first and second streams are mixed to produce a common flow. • the second stream produced by the partial condensation and / or distillation unit contains between 40 and 70% of the total CO2 captured on the at least one reforming unit, the remainder coming from the capture unit using a solvent. • a flow is separated to enrich it in CO2 to produce the second gas, preferably by adsorption. • the flow is compressed upstream of the separation in another compressor and the heat of compression generated by the other compressor is used to regenerate the chemical solvent in the capture unit. • the heat supplied from the first and possibly the second compressor or the other compressor represents at least 10%, preferably at least 25% or even at least 40% of the total heat requirements for regenerating the solvent. • the first gas comes from a reheating furnace or a naphtha cracking unit. • the second gas is a residual gas from a fluidized bed catalytic cracking unit. • the reheat furnace or naphtha cracking unit is part of the same oil refinery as the fluidized bed catalytic cracking unit. • at least one reforming unit is of the steam reforming (SMR) type. • at least one reforming unit is of the autothermal type (ATR).

[0008] According to another object of the invention, there is provided an installation for separating CO2 by partial condensation and / or distillation and by absorption comprising a. A CO2 absorption capture unit using a chemical solvent in which the regeneration of said solvent is carried out by supplying heat, means for sending a first gas containing carbon dioxide and at least one component lighter and / or heavier than CO2 to the capture unit and means for outputting a first stream enriched in CO2 compared to the first gas. b. A partial condensation and / or distillation unit comprising at least one phase separator and / or at least one distillation column, a first compressor, means for sending a second gas containing carbon dioxide and at least one component lighter and / or heavier than CO2, coming from a source other than the capture unit, to the first compressor, means for sending the second gas compressed in the first compressor to a heat exchanger to cool it, means for sending the second gas cooled in the heat exchanger to the at least one phase separator and / or to the at least one distillation column, means for outputting a second stream enriched in CO2 relative to the second gas from the partial condensation and / or distillation unit and optionally a second compressor for compressing the first stream enriched in CO2. c. Means for recovering heat during the compression step of the first gas in the first compressor and possibly during the compression step of the first flow in the second compressor and means for transferring this heat to the capture unit for the regeneration of the CO2 capture unit by chemical solvent.

[0009] According to another object of the invention, there is provided a hydrogen production plant comprising a reforming unit producing a synthesis gas, means for treating the synthesis gas, for example to enrich the synthesis gas with carbon dioxide, means for separating the treated synthesis gas into a flow enriched in hydrogen and depleted in carbon dioxide and a flow enriched in carbon dioxide and depleted in hydrogen, a CO2 separation plant as described above, means for sending the flow enriched in carbon dioxide to the separation unit by partial condensation and / or distillation as a first gas and means for sending fumes from the reforming unit to the separation unit by absorption as a second gas.

[0010] According to another object of the invention, there is provided an oil refining installation comprising a fluidized bed catalytic cracking unit producing a residual gas, means for separating the residual gas forming a flow enriched in carbon dioxide, a CO2 separation installation as described above, means for sending the flow enriched in carbon dioxide to the separation unit by partial condensation and / or distillation as first gas, another unit which may be a reheat furnace or a naphtha cracking unit and means for sending a tail gas from the other unit to the absorption separation unit as a second gas.

[0011] The invention will be described in more detail with reference to the figures where:

[0012] [Fig.l] schematically represents a method according to the invention applied to a hydrogen production unit.

[0013] [Fig.2] schematically represents a method according to the invention applied to a cracking unit.

[0014] According to the invention, a first gas 19 containing CO2 and at least one component lighter and / or heavier than CO2 is separated in a CO2 capture unit using chemical solvent 21 producing a first CO2-enriched stream 17 relative to the first gas 19. The capture unit 21 may use at least one amine or methanol as chemical solvent. The CO2 capture unit 21 using chemical solvent comprises an absorber where the CO2 is absorbed by a solvent, and a regenerator where the solvent loaded with CO2 is thermally regenerated by supplying heat at a typical level of the order of 110-120°C. The heat supplied comes according to the invention from another CO2 separation unit 13, constituting at least 10%, preferably at least 25% or even at least 40% of the total heat requirements for regenerating the solvent. A flow of water vapor 23 can be used to provide the remaining heat required.

[0015] A second gas 9, coming from a source other than the capture unit 21, is compressed in a first compressor C1, cooled in a heat exchanger and separated in a partial condensation and / or distillation unit 13 comprising at least one phase separator and / or at least one distillation column producing a second stream enriched in CO2 15 relative to the second gas, the second stream being optionally compressed in a second compressor C2.

[0016] Heat generated by the compression of the second gas 9 in the first compressor C1 and possibly by the compression of the second flow 15 in the second compressor C2 is used to regenerate the chemical solvent of the capture unit 21.

[0017] The temperature level of the recovered heat is greater than 60°C, preferably greater than 80°C and even greater than 90°C or even greater than 110°C.

[0018] The first compressor C1 and / or the second compressor C2 comprises several stages, the compressed gas not being cooled by an external refrigerant between at least two consecutive stages and / or downstream of a last stage. In this way, the compression is at least partially adiabatic. It is also possible to undersize the coolers between the stages or after the last stage to achieve higher temperatures.

[0019] It is possible to adjust the temperature at the inlet of a stage of the first compressor C1 and / or the second compressor C2 to achieve a minimum temperature level at the compressor outlet.

[0020] The heat can be transferred from the compressor C1 to the capture unit 21 by transfer means 25, 27, 29 which can be constituted by a fluid circulating between the two elements C1; 21. Otherwise the transfer means 25, 27, 29 can comprise a heat pump 25 which ensures the transfer of heat from the first compressor via a connection 29 and possibly from the second compressor, the compression heat being at a level below 110°C, preferably below 100°C and the heat sent to the regenerator of the capture unit using a solvent via the connection 27 being at a level above 110°C, preferably above 120°C.

[0021] In this example, the first gas 19 and the second gas 9 have different CO2 contents, the first gas containing between 15 and 30 mol% CO2 and the second gas 9 containing at least 40 mol% CO2.

[0022] Here the two CO2-enriched streams 15, 17 are mixed after compression in the compressors C2, C3 to form a common product 15.

[0023] In this example, the first gas 19 consists of fumes from at least one SMR or ATR type reforming unit fueled by natural gas 1. The reforming unit uses the natural gas as a fuel producing fumes 19 and as a raw material for a chemical reaction producing a synthesis gas. The synthesis gas 3 is treated, for example to convert carbon monoxide it contains into carbon dioxide, and the treated synthesis gas 5 is sent to at least one PSA H2 type adsorption unit or a permeation unit which separates the treated synthesis gas to produce the hydrogen 7 it contains, the second gas 9 being a hydrogen-depleted and CO2-enriched gas produced at low pressure by the adsorption or permeation unit as a waste gas.

[0024] In this case, the second stream 15 produced by the partial condensation and / or distillation unit 13 contains between 40 and 70% of the total CO2 captured on the at least one reforming unit, the remainder 17 coming from the capture unit using a solvent 21.

[0025] Optionally, a flow 26 enriched in at least one component lighter than carbon dioxide, such as hydrogen, can be sent from the separation unit 13 upstream of the adsorption unit.

[0026] [Fig.2] represents the invention applied in a refinery comprising a unit of fluidized catalytic cracking (FCC) producing a residual gas containing CO2 and a fired heater 18 producing a residual gas containing between 8%-20% mol CO2, for example between 8 and 12% mol CO2.

[0027] Fluidized bed catalytic cracking is a refining process which aims to transform, in the presence of a catalyst, heavy cuts with long hydrocarbon chains into light cuts to be used in the manufacture of fuel.

[0028] In the presence of the catalyst, at high temperature (450 to 550°C) and at almost atmospheric pressure, the large hydrocarbon molecules are broken down to obtain small molecules with a high octane number.

[0029] The industrial process, known since 1928, is based on the use of a fluidized bed of catalyst circulating between a reactor and a regenerator. Feed 1 (typically coming from the refinery's distillation and vacuum distillation units) is injected with the catalyst entering the reactor into a pipe (also called a "riser") where the cracking reaction takes place. The products of the catalytic cracking reaction leaving the pipe are separated from the catalyst by means of mechanical separators (typically cyclones) and are then sent to the fractionation tower.

[0030] During the cracking reaction, coke forms on the surface of the catalyst which flows continuously between the reactor and the regenerator where this coke will be at least partially oxidized mainly into CO and CO2 by injection of air (possibly enriched in oxygen).

[0031] The catalyst can thus be totally or partially (i.e. the coke is not completely eliminated) regenerated, then returned to the reactor.

[0032] A residual gas 3, called in English “fine gas”, containing carbon dioxide and nitrogen and possibly carbon monoxide, for example between 10 and 20% or between 15 and 20% mol of CO2 and between 0 and 10% of carbon monoxide typically 12.5% ​​CO2, 7.5% CO, 80% N2, all the percentages in this document being molar percentages (on a dry basis), is produced in the regenerator.

[0033] It is again separated from the catalyst and dust by mechanical gas / solid separators (generally cyclones) in the regenerator and then possibly in an electrostatic precipitator. The conditions of this residual gas at the outlet of the regenerator are typically a temperature between 500 and 850°C, a pressure between atmospheric pressure and 5 barg. The residual gas is then expanded (in a turbine or in a valve) to atmospheric pressure and then, if it contains CO, is treated to convert carbon monoxide into carbon dioxide in a converter called a "CO boiler". This converter produces heat which is used to produce water vapor or to heat another fluid (for example hot oil).

[0034] In the case of CO2 capture, US 11541348 proposes not to significantly modify the heart of the FCC process (=the reactor and the regenerator), but to innovatively treat the residual gas from the regenerator by producing a 'concentrated' FCC residual gas but containing less than 80% carbon dioxide, preferably Initially between 60 and 70% CO2, or even slightly less than 50% carbon dioxide. This concentration can be achieved by enriching the waste gas with CO2 in an adsorption unit after possibly converting the carbon monoxide still present in the waste gas into CO2.

[0035] Thus, as seen in [Fig.2], the residual gas 3 is compressed in a compressor C0 and then enriched in CO2 by adsorption in the adsorption unit 6 here of the PSA CO2 type or by permeation. The gas 9 containing between 20 and 80 mol% of CO2 is compressed in a compressor C1 and separated by partial condensation in a unit 13 containing at least one phase separator and a heat exchanger. The CO2-rich gas 15 produced by the partial condensation serves as the product of the process and a gas 26 depleted in CO2 compared to the gas 9 is returned upstream of the adsorption unit 6.

[0036] On the same site as the FCC cracking unit, there may be a unit 18 which is a reheating furnace using the heat created by the combustion of fuel to heat a fluid by indirect heat exchange or a naphtha cracking unit. This unit 18 produces a gas 19 containing between 10 and 20 mol% of CO2 and is separated in an absorption unit with chemical solvent 21, for example an amine wash. The unit 21 produces a CO2-enriched stream 17 which is compressed in a compressor C3 and mixed with the gas 15 to form a product.

[0037] Heat generated by the compression of the second gas 9 in the first compressor C1 and possibly by the compression of the flow 3 in the compressor C0 is used to regenerate the chemical solvent of the capture unit 21.

[0038] The temperature level of the recovered heat is greater than 60°C, preferably greater than 80°C and even greater than 90°C or even greater than 110°C.

[0039] Preferably, the first compressor C1 and / or the compressor C0 comprises several stages, the compressed gas not being cooled by an external refrigerant between at least two consecutive stages and / or downstream of a last stage. In this way, the compression is at least partially adiabatic.

[0040] It is also possible to undersize the coolers between stages or after the last stage to achieve higher temperatures.

[0041] It is possible to adjust the temperature at the inlet of a stage of the first compressor C1 and / or the second compressor C0 to achieve a minimum temperature level at the compressor outlet.

[0042] The heat can be transferred from the compressor C1 and / or the compressor C0 to the capture unit 21 by transfer means 25, 27, 29, 29A which can be constituted by a fluid circulating between the two elements C1, C0; 21. Otherwise the transfer means 25, 27, 29 can comprise a heat pump 25 which ensures the transfer of heat from the first compressor C1 by a connection 29 and possibly from the com CO presser by a connection 29A, the heat of compression being at a level lower than 110°C, preferably lower than 100°C and the heat sent to the regenerator of the capture unit using a solvent by the connection 27 being at a level higher than 110°C, preferably higher than 120°C.

Claims

Claims

1. Process for the separation of CO2 by partial condensation and / or distillation and by absorption in which a. a first gas (19) containing CO2 and at least one component lighter and / or heavier than CO2 is separated in a CO2 absorption capture unit (21) using a chemical solvent producing a first stream (17) enriched in CO2 compared to the first gas b. A second gas (9) containing CO2 and at least one component lighter and / or heavier than CO2, coming from a source (SMR, PSA H2, FCC, 6) other than the capture unit, is compressed in a first compressor (Cl), cooled in a heat exchanger and separated in a partial condensation and / or distillation unit (13) comprising at least one phase separator and / or at least one distillation column producing a second stream (15) enriched in CO2 compared to the second gas, the second stream being optionally compressed in a second compressor (C2) and c. Heat generated by the compression of the second gas in the first compressor and possibly by the compression of the second stream in the second compressor is used to regenerate the chemical solvent in the capture unit.

2. Method according to claim 1 in which the temperature level of the recovered heat is greater than 60°C, preferably greater than 80°C and even greater than 90°C or even greater than 110°C.

3. Method according to claim 1 or 2 in which the first compressor (Cl) and / or the second compressor (C2) comprises several stages, the compressed gas not being cooled by an external refrigerant between at least two consecutive stages and / or downstream of a last stage.

4. Method according to claim 1 or 2 or 3 in which the temperature at the inlet of a stage of the first compressor (Cl) and / or of the second compressor (C2) is adjusted to reach a minimum temperature level at the outlet of the compressor.

5. Method according to one of the preceding claims in which a heat pump (25) ensures the transfer of heat from the first compressor (Cl) and possibly from the second compressor (C2), the heat of compression being at a level below 110°C, preferably below 100°C and the heat sent to the regenerator of the capture unit using a solvent (21) being at a level above 110°C, preferably above 120°C.

6. Method according to one of the preceding claims in which the first gas (19) contains less CO2 than the second gas (9).

7. Method according to one of the preceding claims in which the first gas (19) consists of fumes from at least one reforming unit (SMR) producing a synthesis gas (3) and the source of the second gas is at least one adsorption or permeation unit (PSA H2) which separates a gas produced by treating the synthesis gas to separate the hydrogen (7) which it contains, the second gas (9) being a gas depleted in hydrogen and enriched in CO2 produced by the adsorption or permeation unit.

8. Method according to claim 7 in which the second stream (15) produced by the partial condensation and / or distillation unit (13) contains between 40 and 70% of the total CO2 captured on the at least one reforming unit (SMR), the remainder coming from the capture unit using a solvent (21).

9. Method according to one of the preceding claims in which a flow (3, 5) is separated to enrich it with CO2 to produce the second gas (9), preferably by adsorption (PSA H2, 6).

10. A method according to claim 10 wherein the flow (3,5) is compressed upstream of the separation in another compressor (CO) and the heat of compression generated by the other compressor is used to regenerate the chemical solvent of the capture unit (21).

11. Method according to one of the preceding claims in which the heat supplied from the first (Cl) and optionally from the second compressor (C2) or from the other compressor (CO) represents at least 10%, preferably at least 25% or even at least 40% of the total heat requirements for regenerating the solvent.

12. A method according to one of claims 1 to 6 or 9 to 11 in which the first gas (19) comes from a reheating furnace or a naphtha cracking unit (18) and the second gas (9) is a waste gas from a fluidized catalytic cracking (FCC) unit.

13. CO2 separation plant by partial condensation and / or dis-

14. tillation and absorption including: a. A CO2 absorption capture unit using a chemical solvent in which the regeneration of said solvent is carried out by supplying heat, means for sending a first gas containing carbon dioxide and at least one component lighter and / or heavier than CO2 to the capture unit and means for outputting a first stream enriched in CO2 compared to the first gas b. A partial condensation and / or distillation unit comprising at least one phase separator and / or at least one distillation column, a first compressor, means for sending a second gas containing carbon dioxide and at least one component lighter and / or heavier than CO2, coming from a source other than the capture unit, to the first compressor, means for sending the second gas compressed in the first compressor to a heat exchanger to cool it, means for sending the second gas cooled in the heat exchanger to the at least one phase separator and / or to the at least one distillation column, means for outputting a second stream enriched in CO2 relative to the second gas from the partial condensation and / or distillation unit and optionally a second compressor for compressing the first stream enriched in CO2. c. Means for recovering heat during the compression step of the first gas in the first compressor and possibly during the compression step of the first flow in the second compressor and means for transferring this heat to the capture unit for the regeneration of the CO2 capture unit by chemical solvent. Hydrogen production plant comprising a reforming unit producing a synthesis gas, means for treating the synthesis gas, for example to enrich the synthesis gas with carbon dioxide, means for separating the treated synthesis gas into a flow enriched in hydrogen and depleted in carbon dioxide and a flow enriched in carbon dioxide and depleted in hydrogen, a plant CO2 separation unit according to claim 13, means for sending the flow enriched in carbon dioxide to the separation unit by partial condensation and / or distillation as first gas and means for sending fumes from the reforming unit to the separation unit by absorption as second gas.