Method and apparatus for separating a gaseous mixture containing carbon dioxide

Abstract

Title: Method and apparatus for separating a gaseous mixture containing carbon dioxide. An apparatus for separating a gaseous mixture (1, 5) containing carbon dioxide comprises a compressor (C) for compressing the gaseous mixture, a separation unit by at least one partial condensation stage and / or at least one distillation stage (CC), a line for exiting a CO2-rich liquid (7) from the separation unit, means for sending water (W1, W2) heated (E1, E2) by heat exchange with the gaseous mixture upstream and / or downstream of the compressor to a district heating system (DH),means for sending water heated by heat exchange with the gas mixture upstream and / or downstream of the compressor to an absorption or adsorption (AC) refrigeration unit to produce chilled water and a control means to allow the heated water to be sent to the district heating system or to the refrigeration unit depending on the atmospheric temperature. Single figure.

Description

Title of the invention: Method and apparatus for separating a gaseous mixture containing carbon dioxide

[0001] The present invention relates to a method for separating a gaseous mixture containing carbon dioxide.

[0002] Carbon dioxide capture and storage is one of the only solutions to reduce carbon dioxide emissions from industries, such as steel or cement production.

[0003] A process for separating a gaseous mixture containing carbon dioxide comprising the following steps: a. Compression of the gas mixture in a compressor to a pressure greater than 2 bar abs, preferably greater than 5 bar abs or even greater than 7 bar abs, forming compressed gas b. Introduction of the compressed gas into a permeation, adsorption, or absorption separation unit that produces a CO2-enriched flow at a first pressure and a CO2-depleted flow at a second pressure higher than the first pressure. c. Separation of the CO2-enriched flow, for example by compression and separation by partial condensation and / or distillation to produce a CO2-rich liquid

[0004] is known from EP4102163, US2012 / 111051 and WO06 / 106253.

[0005] It is known from DE10046058, EP2873938 and EP3671085 to recover heat for district heating at a low temperature, typically below 150°C, usually below 100°C, or even below 80°C, from an air compressor of an air separation device.

[0006] With the energy transition, the needs for district heating are increasing and recovering low-temperature heat from a compressor is an interesting solution, particularly in the case of a biomass process which often exports heat.

[0007] The present invention provides for two modes of operation, including a first mode of operation, for example in winter, where the heat of compression is used for district heating and a second mode of operation, for example in summer, which uses the heat of compression for a use other than district heating.

[0008] It is known to use the heat from a hot flow for district heating by passing the hot flow through two heat exchangers in series. The first exchanger uses hot water (or another suitable fluid) to cool the hot flow and the The second heat exchanger uses water to cool the hot flow cooled in the first exchanger to a lower temperature. According to this arrangement, when hot water is unavailable, for example when district heating is not operating, cooling is provided entirely by the second heat exchanger using water.

[0009] It is also known from EP-A-2545335 that the heat of compression can be used to heat water for a boiler in a steam cycle of a power plant.

[0010] The present invention provides for the recovery of hot water during at least a period when district heating is not required by using it as a heat source for an absorption or adsorption water chiller and, with this chiller, supplying cooled water either for a district cooling system or for condensing and / or densifying a high-pressure, CO2-rich flow, or for cooling flue gases containing the CO2 to be captured (for example, just before drying). These last two options make it possible to reduce energy consumption for a liquefier and / or a CO2 capture unit.

[0011] Absorption refrigeration uses a chemical process based on the ability of certain liquids to absorb and desorb a vapor. Two components are used: the volatile component is brought to a boil to form the refrigerant, and the other constitutes the absorbent.

[0012] The most commonly used pairs (binary mixtures) are: • Water + lithium bromide: water being the refrigerant • Ammonia + water: ammonia being the refrigerant

[0013] Just like thermodynamic compression machines, absorption installations have the essential elements of a refrigeration circuit, condenser, expansion valve, evaporator, the only difference is that they also have what is called a boiler or desorber, and an absorber, elements necessary for chemical reactions.

[0014] Adsorption refrigeration relies on the use of a solid adsorbent (e.g., silica gel) and a fluid (e.g., water). The fluid evaporates at a temperature below the wet-bulb temperature of the air to cool the water. The fluid is adsorbed onto a first bed of adsorbent cooled with water to a temperature close to the wet-bulb temperature of the air. A second, parallel bed is regenerated by heating it with hot water. The fluid desorbs at a pressure above the evaporation pressure. It is recondensed with water at a temperature close to the wet-bulb temperature of the air. The liquid fluid is returned to the evaporator. The beds are reversed cyclically.

[0015] The advantage of this type of refrigeration machine is that there are few moving parts, which limits the causes of breakdowns.

[0016] According to one aspect of the invention, a process for separating a gaseous mixture containing carbon dioxide is provided, comprising the following steps: a. Compression of the gas mixture in a compressor up to a pressure greater than 2 bar abs, preferably greater than 5 bar abs or even greater than 7 bar abs b. Separation of the gas mixture or separation of a CO2-enriched flow produced by separating the gas mixture, the separation of the gas mixture or the CO2-enriched flow being carried out at a temperature below 0°C by at least one partial condensation step and / or at least one distillation step and / or at least one washing step and / or at least one solidification step to produce a CO2-rich liquid and / or solid and a CO2-depleted gas, c. Heat recovery from at least a portion of the gas mixture upstream and / or downstream of the compression of the gas mixture in the compressor and

[0017] i. According to a first mode of operation, at least part of the recovered heat is used to heat a fluid in a district heating system, the fluid being preferably heated to a temperature between 60°C and 150°C and

[0018] ii. According to a second mode of operation, at least part of the recovered heat serves as a heat source for an absorption or adsorption refrigeration unit to produce cooled fluid, for example chilled water.

[0019] According to other optional aspects: • the compressed gas mixture is separated in a separation unit by permeation and / or by adsorption and / or by absorption which produces the CO2-enriched flow at a first pressure and a CO2-depleted flow at a second pressure higher than the first pressure. • The process includes recovering heat from at least a portion of the gas mixture upstream of a washing step prior to compression. • according to the second mode of operation at least part of the cooled fluid, for example cooled water is used in an urban cooling system, for example air conditioning. • The first operating mode is used if the atmospheric temperature is below 15°C, or even 10°C, or even below 5°C and / or if the energy demand for the district heating system is greater than the average demand and / or if the atmospheric temperature is below the annual average. • The second operating mode is used if the atmospheric temperature is above 25°C, or even above 30°C and / or if the atmospheric temperature is at least 10°C above the average temperature for the year and / or if the energy demand for the urban cooling system is above a threshold. • according to the second mode of operation, at least part of the cooled fluid, for example cooled water, is used to cool a flow of CO2 or ammonia used as a refrigerant to cool, or even condense, a flow of gaseous CO2 under a pressure of at least 60 bar, or even at least 70 bar. • according to the second mode of operation, at least part of the cooled fluid, for example chilled water, is used to cool at least part of the CO2-rich liquid, for example upstream or downstream of a pumping stage. • the CO2 enriched flow and / or the gas mixture contains water and according to the second mode of operation at least part of the cooled fluid, for example cooled water, produced is used to cool the CO2 enriched flow upstream of an adsorption drying unit upstream of the partial condensation separation and / or distillation and / or washing and / or solidification. • According to the second operating mode, at least a portion of the cooled fluid, for example chilled water, produced is used to cool at least a flow sent to the separation unit where separation by partial condensation and / or distillation and / or washing and / or solidification takes place • Part of the heat recovered during the first mode is used to reheat the CO2-depleted gas upstream of an expansion in a turbine and another part of the heat recovered during the first mode is used for the district heating system, the ratio between the parts being modifiable according to district heating needs. • the gaseous mixture contains at least 10% CO2, at least 20% CO2, at least 30% CO2, at least 40% CO2, at least 50% CO2, at least 60% CO2, at least 70% CO2, at least 80% CO2, at least 90% CO2 on a dry basis, these contents being molar percentages • the gaseous mixture contains at least 10% CO2, at least 20% CO2, at least 30% CO2, at least 40% CO2, at least 50% CO2, at least 60% CO2, at least 70% CO2, at least 80% CO2, at least 90% CO2 and does not contain water, these contents being molar percentages.

[0020] According to another object of the invention, a device for separating a gaseous mixture containing carbon dioxide is provided, comprising a compressor, for compressing the gas mixture, a separation unit by at least one partial condensation step and / or at least one distillation step and / or at least one washing step and / or at least one solidification step, the separation unit comprising means for thermal insulation to operate at a temperature below 0°C, a line for exiting a liquid and / or a CO2-rich solid from the separation unit and a line for exiting a CO2-depleted gas from the separation unit, means for sending water heated by heat exchange with the gas mixture upstream and / or downstream of the compressor to a district heating system,means for sending water heated by heat exchange with the gas mixture upstream and / or downstream of the compressor to an absorption or adsorption chiller to produce chilled water, and a control means to allow the heated water to be sent to the district heating system or to the chiller depending on the atmospheric temperature or the time of year and / or the energy demand for the district heating system and / or the energy demand for a district cooling system.

[0021] The device may include: • a permeation and / or adsorption and / or absorption separation unit to separate the compressed gas mixture and which produces the CO2-enriched flow at a first pressure and a CO2-depleted flow at a second pressure higher than the first pressure. • according to the second mode of operation at least part of the cooled water is used in an urban cooling system, for example air conditioning. • The control means is configured to allow the sending of heated water to the district heating system if the atmospheric temperature is below 15°C, or even 10°C, or even below 5°C and / or if the energy demand for the district heating system is greater than the average demand and / or if the atmospheric temperature is below the annual average. • The control means is configured to allow the heated water to be sent to the refrigeration unit if the atmospheric temperature is above 25°C, or even above 30°C and / or if the atmospheric temperature is at least 10°C above the average temperature for the year and / or if the energy demand for the district cooling system is above a threshold. • The apparatus includes means for sending at least a portion of the cooled water to cool a flow of CO2 or ammonia used as a refrigerant to cool, or even condense, a flow of gaseous CO2 under a pressure of at least 60 bar, or even at least 70 bar. • The apparatus includes means for sending at least a portion of the cooled water to cool at least a portion of the CO2-rich liquid, for example upstream or downstream of a pumping stage. • The apparatus includes an adsorption drying unit upstream of the partial condensation separation and / or distillation and / or washing and / or solidification • The apparatus includes means for sending at least a portion of the cooled water produced to cool the CO2-enriched flow upstream of the drying unit • The apparatus includes means for sending at least a portion of the cooled water produced to cool at least a flow sent to the separation unit where separation by partial condensation and / or distillation and / or washing and / or solidification takes place • The device includes a turbine and means for sending the CO2-depleted gas to expand in the turbine • The device includes means for sending some of the recovered heat to reheat the CO2-depleted gas upstream of an expansion in the turbine • The device includes means for varying the amount of heat sent to reheat the CO2-depleted gas upstream of the turbine.

[0022] The invention will be described in more detail with reference to the figure where

[0023] [Fig-1] represents a method according to the invention schematically.

[0024] A gaseous mixture 1 containing CO2 originates from a source S which may be a steel mill, a cement plant, a combustion unit (possibly using biomass), for example, an oxy-combustion plant, a gasification plant. The gaseous mixture may contain at least 10% CO2, at least 20% CO2, at least 30% CO2, at least 40% CO2, at least 50% CO2, at least 60% CO2, at least 70% CO2, at least 80% CO2, or at least 90% CO2 on a dry basis if the gaseous mixture contains water, all these percentages being molar percentages. The gas mixture may contain methane and / or carbon monoxide and / or hydrogen and / or oxygen and / or nitrogen and / or argon and / or NOx and / or water. The gas mixture 1 may be at a temperature above 60°C, or even above 150°C.The gas mixture 1 can optionally be cooled by a water flow W2 in a heat exchanger E1 and scrubbed in a scrubbing tower Q to remove contaminants. The scrubbed mixture is then compressed in a heat-generating compressor, and this heat is recovered in a heat exchanger E2 to heat a water flow W1 to a temperature between 60 and 150°C. The cooled gas mixture 5 is further cooled in a capture unit. CO2 CC and separated by at least one partial condensation step and / or at least one distillation step and / or at least one washing step and / or at least one solidification step to produce a liquid and / or a CO2-rich solid and a CO2-depleted gas.

[0025] According to a first mode, for example in winter and / or if the atmospheric temperature is below 15°C or even below 10°C, or below 5°C and / or below at least 10°C the average temperature for the year and / or if the energy demand for district heating is above the average demand, for example above at least 20% above the average demand, the flow of heated water W1 is sent to a district heating system DH where it provides heat.

[0026] According to a second mode, for example in summer if the atmospheric temperature is above 25°C, or even above 30°C and / or above by at least 10°C the average temperature for the year and / or if the energy demand for district heating is below the average demand, for example below by at least 20% the average demand and / or if the energy demand for district cooling is above a threshold.

[0027] The heated water flow W1 is no longer sent to the district heating system DH but to an absorption or adsorption chiller AC to produce cooled fluid, for example chilled water H2, H3. The cooled fluid, for example chilled water, can be used for various purposes, for example:

[0028] For district cooling, for example a district cooling system, district air conditioning, DC supplied by the flow H3, of the heated fluid, for example the flow of heated water H4 being returned to the refrigeration unit AC

[0029] To provide cooling to the CO2 capture unit CC, for example, to cool the CO2-rich liquid product 7 upstream of a pumping stage and / or to cool the gas mixture to condense the water it contains upstream of an adsorption drying stage and / or to cool the gas mixture downstream of an adsorption drying stage and / or to provide cooling to a closed or semi-closed refrigeration cycle with CO2 or ammonia and / or to cool the cooling water of the capture unit CC. Here, the fluid flow, for example, water, cooled H2 arrives from the refrigeration unit AC, and the heated fluid Hl, for example, the water Hl heated in the CC unit, is returned to the refrigeration unit AC.

[0030] According to the second mode of operation, at least part of the cooled fluid, for example chilled water, can be used to cool a flow of CO2 or ammonia used as a refrigerant, for example in a circuit, to cool, or even condense, a flow of gaseous CO2 under a pressure of at least 60 bar, or even at least 70 bar, coming for example from a CO2 separation unit by partial condensation and / or liquefaction CC.

[0031] According to the second mode of operation, at least a part of the cooled fluid, for example cooled water, can be used to cool at least a part of the CO2-rich liquid, for example liquid 7, for example upstream of a pumping step or after a pumping step.

[0032] The second mode can be used for example if the atmospheric temperature is above 25°C, or even above 30°C and / or at least 10°C above the average temperature for the year.

[0033] There may be a third mode in which the heated water flow WI is not sent to either the district heating system DH or the absorption chiller.

[0034] Alternatively, the water W1 and / or W2 can always be sent either to the district heating system DH or to the absorption chiller.

[0035] Using cooled fluid, for example chilled water, H2, H3 in warm season to cool the refrigerant or the CO2 produced makes it possible to reduce the increase in the outlet pressure of the CO2 liquefaction cycle and / or to keep it constant, even if the available cooling water becomes warmer.

[0036] Between winter and summer, the air temperature can vary by, for example, 30°C (e.g., 0°C in winter and 30°C in summer). The temperature of the cooling water used to cool a cycle compressor is generally obtained by air cooling. The temperature of the cooled water therefore follows the same variations.

[0037] If, using the invention, the cycle compressor is cooled with a fluid cooled, for example, water cooled by the adsorption or absorption unit according to the invention, the variation in water temperature between summer and winter can be reduced compared to that obtained with water cooled by ambient air. The cooling temperature of the compressor's aftercooler defines the condensation pressure of the cycle fluid. Thus, using a cooled fluid, for example, water from the adsorption or absorption unit in summer, reduces the range of outlet pressures of the cycle compressor.

[0038] With the invention, the condensation temperature of the cycle fluid (CO2) varies by a maximum of 10°C and preferably by a maximum of 7°C between the maximum and minimum temperatures observed for the cycle fluid during the year. This small variation allows for good efficiency at all operating points of the machine.

[0039] The water used to supply heat to the AC refrigeration unit is returned as flow W6 to a pump which distributes the water W1, W2 to the heat exchangers El, E2.

[0040] Thus, the heat from the gas mixture 1 can be recovered upstream of the compressor in the heat exchanger El because the gas mixture 1 is sometimes at a high temperature. In this case, the water W2, heated to a temperature between 60 and 150°C, can be used in place of W1 water or with W1 water. W2 water or a mixture of W1 and W2 can be used exactly as described for W1 above.

[0041] Alternatively, part of the heat recovered during the first mode is used to reheat the CO2-depleted gas produced by the CC capture upstream of an expansion in a turbine and another part of the heat recovered during the first mode is used for district heating DH, the ratio between the parts being modifiable according to district heating needs.

[0042] In a variant of the invention, which is not illustrated, the compressed gas mixture 5 is separated by permeation (at ambient or subambient temperature) and / or by adsorption (TSA or PSA) and / or by absorption (washing with a solvent such as potassium carbonate) or any other suitable means, which produces the CO2-enriched flow at a first pressure and a CO2-depleted flow at a second pressure higher than the first pressure.

[0043] In this case, the mixture 5 is separated, producing a CO2-enriched flow at a first pressure and a CO2-depleted flow at a second pressure higher than the first pressure. It is the CO2-enriched flow (or possibly the CO2-depleted flow), instead of the compressed mixture 5, that is separated in the capture unit CC.

[0044] According to one embodiment, part of the heat recovered during the first mode can be used to reheat the CO2-depleted gas produced by the CC capture or the CO2-depleted flow to the second pressure upstream of an expansion in a turbine to generate electricity or to drive a compressor. Another part of the heat recovered during the first mode is used for district heating (DH), the ratio between the parts being adjustable according to district heating requirements.

[0045] The water flow rates W1, W2 can be sent to the district heating system DH separately, for example at different times or by being mixed.

[0046] The water flow rates W1, W2 can be sent to the AC refrigeration unit separately, for example at different times or by being mixed.

[0047] It will be understood that references to winter and summer here refer to the meteorological seasons. Water W1, W2, W6 may contain glycol or another additive to reduce the risk of freezing.

Claims

1. Demands A process for separating a gaseous mixture (1,5) containing carbon dioxide comprising the following steps: a. Compression of the gas mixture in a compressor (C) to a pressure greater than 2 bar abs, preferably greater than 5 bar abs or even greater than 7 bar abs b. Separation of the mixture or separation of a CO2-enriched flow produced by separating the mixture, the separation of the mixture or the CO2-enriched flow being carried out at a temperature below 0°C by at least one partial condensation step and / or at least one distillation step and / or at least one washing step and / or at least one solidification step (CC) to produce a CO2-rich liquid and / or solid (7) and a CO2-depleted gas, c. Heat recovery (El, E2) from at least a portion of the gas mixture upstream and / or downstream of the compression of the gas mixture in the compressor and i. According to a first mode of operation, at least part of the recovered heat is used to heat a fluid (W1, W2) in a district heating (DH) system, the fluid being preferably heated to a temperature between 60°C and 150°C and ii.According to a second mode of operation, at least part of the recovered heat serves as a heat source for an absorption or adsorption (AC) refrigeration unit to produce a cooled fluid, for example chilled water (H2, H3), in which the first mode of operation is used if the atmospheric temperature is below 15°C, or even 10°C, or even below 5°C and / or if the energy demand for the district heating (DH) system is above the average demand and / or if the atmospheric temperature is below the annual average and / or the second mode of operation is used if the atmospheric temperature is above 25°C, or even above 30°C and / or if the atmospheric temperature is at least 10°C above the average temperature for the year and / or if the energy demand. for the urban cooling (DC) system is above a threshold.

2. A method according to claim 1 wherein the compressed gas mixture (5) is separated in a separation unit by permeation and / or by adsorption and / or by absorption which produces the CO2-enriched flow at a first pressure and a CO2-depleted flow at a second pressure higher than the first pressure.

3. Method according to claim 1 or 2 wherein according to the second mode of operation at least a part of the cooled fluid, for example cooled water, is used in a district cooling (DC) system, for example air conditioning.

4. A method according to any one of the preceding claims wherein, according to the second mode of operation, at least a part of the cooled fluid, for example cooled water (H2, H3), is used to cool a flow of CO2 or ammonia used as a refrigerant to cool, or even condense, a flow of gaseous CO2 (7) under a pressure of at least 60 bar, or even at least 70 bar.

5. A method according to any one of the preceding claims wherein, according to the second mode of operation, at least a part of the cooled fluid, for example chilled water (H2, H3) is used to cool at least a part of the CO2-rich liquid (7), for example upstream or downstream of a pumping stage.

6. A method according to any one of the preceding claims wherein the CO2-enriched flow and / or gas mixture (1,5) contains water and according to the second mode of operation at least a part of the cooled fluid, for example cooled water (H2, H3), produced is used to cool the CO2-enriched flow upstream of an adsorption drying unit upstream of partial condensation separation and / or distillation and / or washing and / or solidification (CC).

7. A method according to any one of the preceding claims wherein, according to the second mode of operation, at least a portion of the cooled fluid, for example, of the produced cooled water (H2, H3), is used to cool at least a flow sent to the separation unit where separation is carried out by partial condensation and / or distillation and / or washing and / or solidification (CC).

8. A method according to any one of the preceding claims, wherein a portion of the heat recovered during the first mode is used to reheat the CO2-depleted gas upstream of an expansion

9. in a turbine and another part of the heat recovered during the first mode is used for the district heating (DH) system, the ratio between the parts being modifiable according to district heating needs. Apparatus for separating a gaseous mixture (1,5) containing carbon dioxide comprising a compressor (C), for compressing the gaseous mixture, a separation unit by at least one partial condensation stage and / or at least one distillation stage and / or at least one washing stage and / or at least one solidification stage (CC), the separation unit comprising means for thermal insulation to operate at a temperature below 0°C, a line for delivering a liquid and / or a CO2-rich solid (7) from the separation unit and a line for delivering a CO2-depleted gas from the separation unit, means for sending water (W1, W2) heated (E1, E2) by heat exchange with the gaseous mixture upstream and / or downstream of the compressor to a district heating system (DH),means for sending water heated by heat exchange with the gas mixture upstream and / or downstream of the compressor to an absorption or adsorption (AC) refrigeration unit to produce chilled water, and a control means to allow the heated water to be sent to the district heating system or to the refrigeration unit as chosen, depending on the atmospheric temperature or the time of year and / or the energy demand for the district heating system and / or the energy demand for a district cooling system.

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