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EP-4739961-A2 - METHOD FOR LIQUEFYING AND/OR SOLIDIFYING A GAS RICH IN CARBON DIOXIDE

EP4739961A2EP 4739961 A2EP4739961 A2EP 4739961A2EP-4739961-A2

Abstract

The invention relates to a device for liquefying a gas rich in carbon dioxide, the device comprising a first heat exchanger (EI), means for sending a low-temperature methane-rich fluid (1) to the first exchanger and means for sending an intermediate fluid (5) to the first heat exchanger in order to cool the intermediate fluid, a compressor (C) connected to the first heat exchanger in order to compress the cooled intermediate fluid, means for sending the compressed intermediate fluid (7) to a second heat exchanger (E2) in order to heat it up, means for separating the reheated intermediate fluid into two parts, means for sending one portion of the intermediate fluid (11) to the first exchanger without passing through a hot end of the second heat exchanger, means for sending another portion (9) of the intermediate fluid to the first exchanger by passing through the hot end of the second heat exchanger, means for sending a flow of carbon dioxide (13) to the second heat exchanger in order to cool the flow, and means for producing a flow of liquid carbon dioxide (17) downstream of the second heat exchanger.

Inventors

  • DUBETTIER-GRENIER, RICHARD
  • Raventos, Martin
  • LECLERC, Mathieu

Assignees

  • L'AIR LIQUIDE, SOCIETE ANONYME POUR L'ETUDE ET L'EXPLOITATION DES PROCEDES GEORGES CLAUDE

Dates

Publication Date
20260513
Application Date
20240614

Claims (15)

  1. Process for liquefying and/or solidifying a gas (13) rich in carbon dioxide in which at least part of the frigories for the liquefaction and/or solidification are provided by a fluid rich in methane (1) at low temperature in which: (a) the methane-rich fluid is a methane-rich liquid, for example liquefied natural gas or methane-rich gas at a temperature below -50°C, the methane-rich fluid cools an intermediate fluid (5) at a pressure between 5 and 40 bara to a first temperature between -30°C and -100°C b) the intermediate fluid is compressed (C, C1) in gaseous form before or after cooling to the first temperature and sent to a heat exchanger (E2) at a second temperature between -30°C and -80°C, preferably between -50°C and -55°C where it heats up by indirect heat exchange with the carbon dioxide-rich gas which at least partially condenses and/or solidifies. (c) the intermediate fluid heated in the heat exchanger is divided into two, a portion (11) of the fluid leaving the heat exchanger at a temperature which differs by at most 10°C from the dew point temperature of the carbon dioxide-rich gas to be at least partially condensed and which is at least 15°C lower than the temperature at which the carbon dioxide-rich gas enters the heat exchanger at a first end thereof, this portion constituting at least 50%, or even at least 70%, of the intermediate fluid entering the heat exchanger and the part constituting at least 50% of the intermediate fluid is not heated in the heat exchanger and (i) is not heated outside the heat exchanger or ii) is heated outside the heat exchanger by cooling a refrigerant (19) and/or the carbon dioxide-rich gas e) another portion of the intermediate fluid (9) heats up to the first end of the heat exchanger and (f) the part constituting at least 50% of the intermediate fluid and the other part are mixed and returned to be cooled by the methane-rich fluid of step (a), the intermediate fluid remaining gaseous during the heat exchange with the methane-rich fluid and the intermediate fluid cycle not including a phase change.
  2. Method according to claim 1 in which at least part of the intermediate fluid compressed and heated in the exchanger is expanded in a turbine (T) to a temperature between -30°C and -80°C, preferably between -50°C and -55°C, and returned to the heat exchanger (E2) to be reheated and divided into two according to step c).
  3. Method according to claim 2 in which intermediate fluid expanded in the turbine (T) is reheated in the heat exchanger (E2), then expanded in another turbine to a temperature between -30°C and -80°C, preferably between -50°C and -55°C, and returned to the heat exchanger to be reheated and divided into two according to step c).
  4. A method according to any preceding claim, wherein the CO2-rich gas (13) is a waste gas from a pressure swing adsorption process producing a gas enriched in hydrogen relative to the gas feeding the adsorption process and the waste gas depleted in hydrogen relative to the gas feeding the adsorption process.
  5. Method according to one of the preceding claims in which the intermediate fluid (9, 11) contains at least 90 mol% of nitrogen or methane or is a mixed refrigerant comprising at least nitrogen, methane and ethane and/or ethylene.
  6. Method according to one of the preceding claims in which the flow rate of intermediate fluid (5) is between 10D/L and 25D/L where D is the flow rate of carbon dioxide-rich gas (13) sent to the heat exchanger (E2) in Nm3/h and L is the number of intermediate fluid flows in the heat exchanger.
  7. Method according to one of the preceding claims in which the carbon dioxide-rich gas is compressed in a compressor (V1, V2, C3, C4, C5) upstream of the heat exchanger having at least two stages and an interstage cooler (E5) cooled either by a/the intermediate fluid portion or by the water (19) which has been cooled by the intermediate fluid portion (11).
  8. A method according to claim 7 wherein an interstage cooler (E5) cooled by a/the intermediate fluid portion (11) to less than -55°C cools a carbon dioxide rich gas to a pressure below 5.1 bar abs.
  9. Method according to one of the preceding claims, in which the carbon dioxide-rich gas (13) is cooled in a cooler (E6) then purified of water (P) upstream of the heat exchanger (E2) and the part of the intermediate fluid (11) is used to cool the carbon dioxide-rich gas.
  10. Method according to one of the preceding claims in which a flow having the same composition (41, 43) as the intermediate fluid is cooled to a temperature between -120°C and -160°C and provides cold to a liquefaction or separation unit (300) operating at a temperature between -120°C and -160°C, for example an air separation apparatus or a hydrogen liquefier (27).
  11. Method according to one of the preceding claims in which a flow having the same composition (41, 43) as the intermediate fluid is cooled to a temperature between -135°C and -155°C and provides cold to a liquefaction or separation unit operating at a temperature between -135°C and -155°C, to solidify a portion of gas (27) rich in liquefied carbon dioxide.
  12. Method according to one of the preceding claims, in which the methane-rich fluid is a methane-rich liquid (1) which is preheated before cooling the intermediate fluid (5) of step a) by heat exchange with at least one other flow of intermediate fluid or glycolated water.
  13. Method according to one of the preceding claims, in which the compression (C, C1) of step b) raises the pressure of the intermediate fluid so that the intermediate fluid which heats up in the heat exchanger (E2) leaves the exchanger and is divided while it is at a pressure substantially equal to that of the fluid upstream of the compression of step b).
  14. Method according to one of the preceding claims in which the intermediate fluid (5) is a gas and is not condensed by heat exchange with the methane-rich fluid (1).
  15. Method according to one of the preceding claims, in which the heat exchanger (E2) is a brazed plate and fin exchanger.

Description

Process for liquefying and/or solidifying a gas rich in carbon dioxide The present invention relates to a method for liquefying and/or solidifying a carbon dioxide-rich gas. The gas that is liquefied is a carbon dioxide-rich gas containing more than 30 mol% carbon dioxide such as a waste gas from a PSA producing a hydrogen-enriched gas or fumes. It is known from “Integrating hydrogen liquefaction with steam methane reforming and CO2 liquefaction processes using techno-economic perspectives” by Lee et al, Energy Conversion and Management 245 (2021) to use the frigories of a vaporization of liquefied natural gas to liquefy CO2 and hydrogen. The present invention provides a method for liquefying and/or solidifying a gas rich in carbon dioxide, i.e. containing at least 30 mol% carbon dioxide, or even at least 50 mol% carbon dioxide, preferably at least 90 mol% carbon dioxide. The gas also contains at least one of the following gases: nitrogen, oxygen, hydrogen, methane, NOx, argon, carbon monoxide. JP H06 63699, US2019151789 and FR2969404 describe the use of an intermediate cycle to transfer the cold from an LNG flow to a CO2 flow to be liquefied. JP H06 63699 published in 1990 describes an ethylene intermediate cycle in which ethylene vaporizes with the heat of the CO2 flow. An object of the invention is to improve the exchange diagram of the process in order to avoid large temperature differences at the hot end of a heat exchanger used to liquefy a CO2-rich gas. To make a process more energy efficient, it is necessary to avoid large temperature differences, especially in the case where the heat exchanger is a brazed plate and fin type exchanger. It is also planned to use an intermediate fluid cycle without phase change to transfer the cold from the natural gas, liquefied or not, to the gas to be liquefied. According to an object of the invention, there is provided a method of liquefaction and/or solidification of a gas rich in carbon dioxide in which at least part of the frigories for the liquefaction and/or solidification are provided by a fluid rich in methane at low temperature characterized in that: (a) the methane-rich fluid is a methane-rich liquid, for example liquefied natural gas or methane-rich gas at a temperature below -50°C, the methane-rich fluid cools an intermediate fluid at a pressure between 5 and 40 bara to a first temperature between -30°C and -100°C (b) the intermediate fluid is compressed into gaseous form before or after cooling to the first temperature and sent to a heat exchanger at a second temperature between -30°C and -80°C, preferably between -50°C and -55°C where it heats up by indirect heat exchange with the carbon dioxide-rich gas which at least partially condenses and/or solidifies. (c) the intermediate fluid heated in the heat exchanger is divided into two, a part of the fluid leaving the heat exchanger at a temperature which differs by not more than 10°C from the dew point temperature of the carbon dioxide-rich gas to be at least partially condensed and which is at least 15°C lower than the temperature at which the carbon dioxide-rich gas enters the heat exchanger at a first end thereof, this part constituting at least 50%, or even at least 70%, of the intermediate fluid entering the heat exchanger and (d) the part constituting at least 50% of the intermediate fluid is not heated in the heat exchanger and (i) is not heated outside the heat exchanger or ii) is heated outside the heat exchanger by cooling a refrigerant and/or the carbon dioxide-rich gas e) another part of the intermediate fluid heats up to the first end of the heat exchanger and (f) the part constituting at least 50% of the intermediate fluid and the other part are mixed and returned to be cooled by the methane-rich fluid of step (a), the intermediate fluid remaining gaseous during the heat exchange with the methane-rich fluid and the intermediate fluid cycle not including a phase change. According to other optional features: at least a portion of the intermediate fluid compressed and heated in the exchanger is expanded in a turbine to a temperature between -30°C and -80°C, preferably between -50°C and -55°C, and returned to the heat exchanger to be reheated and divided into two according to step c). intermediate fluid expanded in the turbine is reheated in the heat exchanger, then expanded in another turbine to a temperature between -30°C and -80°C, preferably between -50°C and -55°C, and returned to the heat exchanger to be reheated and divided into two according to step c). CO2-rich gas is a waste gas from a pressure swing adsorption process producing a hydrogen-enriched gas relative to the gas feeding the adsorption process and the hydrogen-depleted waste gas relative to the gas feeding the adsorption process. the intermediate fluid contains at least 90 mol% nitrogen or methane or is a mixed refrigerant comprising at least nitrogen, methane and ethane and/or ethylene. the intermediate fluid flow rate is be