PROCESS FOR CAPTURING CARBON DIOXIDE FROM A SYNTHETIC GAS FLOW RECEIVED FROM A SYNTHETIC GAS PRODUCTION UNIT

Abstract

Title of the invention: METHOD FOR CAPTURING CARBON DIOXIDE FROM A SYNTHESIS GAS STREAM RECEIVED FROM A SYNTHESIS GAS PRODUCTION UNIT A method for capturing carbon dioxide from a synthesis gas stream comprises the following steps: introducing the synthesis gas stream into a pressure-modulated adsorber (PSA) to produce a hydrogen product stream and a waste gas; compressing the PSA waste gas in a compressor, then sending the compressed waste gas to a temperature-toggle adsorber (TSA) to remove water from the waste gas to form a dry gas (32); separating the dry gas in a partial condensation and distillation separation unit to produce at least two streams, which are a liquid (74), which is enriched in CO2 and a waste gas (72), which is depleted in CO2; expand the residual gas (72) in a Joule-Thomson valve (76), thus cooling the residual gas;reheat the expanded residual gas in the heat exchanger (50); heat the residual gas in a regeneration heater (80); and regenerate an adsorbent bed inside the TSA (30) using the expanded and heated gas as the regeneration gas. Fig. 2;

Description

Title of the invention: METHOD FOR CAPTURING CARBON DIOXIDE FROM A SYNTHETIC GAS FLOW RECEIVED FROM A SYNTHETIC GAS PRODUCTION UNIT Scope of the invention

[0001] The present invention relates to a method and apparatus for capturing CO2.

[0002] Context of the invention

[0003] Autothermal reforming (ATR), steam methane reforming (SMR), or partial oxidation (POX) are the main processes for producing syngas, which is a mixture composed primarily of hydrogen and carbon monoxide, although it may also contain methane, carbon dioxide, unreacted water, and other impurities. When high-purity decarbonized hydrogen is the desired product, CO2 capture can be implemented on the residual gas by pressure-modulated adsorption (H2), consisting of a combination of compression, drying, cryogenics, and membrane and / or adsorption separation. This invention relates to improving the efficiency of such processes and reducing the energy intensity for carbon capture.

[0004] [Fig. 1] presents an embodiment of the prior art. The feed flow 2, which includes a syngas stream, is introduced into a pressure-switching adsorber (PSA), which gives a hydrogen product and a PSA waste gas 12. This waste gas 12 is then compressed in the waste gas compressor 20, before being introduced into a temperature-switching adsorber (TSA) 30 in order to remove water from the waste gas 12.

[0005] The resulting dry gas 32 can then be introduced into a cold box 40, which contains a heat exchanger 50, as well as a gas-liquid separator 60 and a distillation column 70. The dry gas 32 is cooled in the heat exchanger 50, in which at least a portion of the dry gas is condensed. This two-phase fluid is then introduced into the gas-liquid separator 60, in which the overhead gas 66 is extracted and reheated in the heat exchanger 50 against the dry gas 32. The liquid stream 62 from the gas-liquid separator 60 is expanded in a valve 64, and then introduced into the distillation column 70, in which the liquid stream 62 is separated into non-condensable overhead gas 72 and a condensed fluid 74.

[0006] The non-condensable gas 72, which is typically at a pressure of more than 10 bar(a), is heated in the heat exchanger 50, and its pressure is reduced in the valve 76 to correspond to the TSA 30, which is typically less than 6 bar(a). Due to From the expansion, the resulting expanded flow must be reheated in the regeneration heater 80 before this gas is used to regenerate the TSA adsorbers.

[0007] This configuration is thermodynamically inefficient. Summary of the invention

[0008] In certain embodiments, the invention proposes to use the cooling effect of the expansion of the non-condensable heads of the distillation column by moving the expansion valve 76 from outside the cold box 40 to the cold end of the heat exchanger 50. Thus, the non-condensable head gas 72 is expanded in the expansion valve before being heated in the heat exchanger 50. This allows the Joule-Thomson expansion cooling to be used in the heat exchanger and to provide additional cooling for the dry gas 32.

[0009] According to one object of the invention, a method for capturing carbon dioxide from a syngas stream received from a syngas production unit is proposed, with the following steps:

[0010] introduce the synthesis gas stream into a pressure-toggle adsorber to produce a hydrogen product stream and a waste gas; compress the waste gas in a compressor, then send the compressed waste gas to a temperature-toggle adsorber to remove water from the waste gas to form a dry gas; separate the dry gas in a partial condensation and distillation separation unit to produce at least two streams, which are a liquid, which is enriched in CO2 and depleted in at least one gas among methane, hydrogen and carbon monoxide relative to the dry gas, and a waste gas, which is depleted in CO2 and enriched in at least one among methane, hydrogen and carbon monoxide relative to the dry gas; expand the waste gas in a Joule-Thomson valve, thus cooling the waste gas; reheat the expanded waste gas in a heat exchanger;heat the residual gas in a regeneration heater; and regenerate an adsorbent bed inside the TSA using the expanded and heated gas as the regeneration gas;

[0011] According to other optional features: • the dry gas contains a component chosen from the list: helium, nitrogen, argon; • the synthesis gas production unit is an autothermal reformer; • The synthesis gas production unit is a methane reformer steam ; • the synthesis gas production unit is a partial oxidation unit; • The residual gas is expanded in the Joule-Thomson valve to a temperature between -15 and -60°C before being reheated in the heat exchanger; and / or • The regeneration gas used to regenerate the temperature-modulated adsorption unit is heated to a temperature between 120 and 250 °C in the regeneration heater (80).

[0012] Brief description of the drawings

[0013] Other features and advantages of the invention will become apparent from, on the one hand, the following description and, on the other hand, several embodiments given by way of illustration and not limitation and with reference to the accompanying schematic drawings, in which:

[0014] [Fig. 1] is a schematic diagram of an embodiment of the prior art.

[0015] [Fig.2] is a schematic diagram of an embodiment of the present invention. Detailed description of the invention

[0016] In [Fig. 2], the Joule-Thomson valve 76 is moved to the cold side of the heat exchanger 50, and consequently, the non-condensable gases 72 can be expanded in the valve 76 before being reheated in the heat exchanger 50. This allows embodiments of the present invention to utilize additional cooling capacity from the expanded gas stream 72 in the heat exchanger 50, while also reducing the heat requirements of the regeneration heater 80, since the resulting gas entering the regeneration heater 80 is at a higher temperature than in [Fig. 1]. Therefore, embodiments of the present invention allow for reduced operating costs compared to processes such as those in [Fig. 1].

Claims

Demands

1. A method for capturing carbon dioxide from a syngas stream received from a syngas production unit, comprising the following steps: • introducing the syngas stream (2) into a pressure-toggle adsorber (PSA) to produce a hydrogen product stream (H2) and a waste gas (12); • compressing the waste gas in a compressor (20), then sending the compressed waste gas to a temperature-toggle adsorber (TSA) (30) to remove water from the waste gas to form a dry gas (32);• separate the dry gas (32) in a separation unit (60) by partial condensation (50) and distillation (70) to produce at least two streams, which are a liquid (74), which is enriched in CO2 and depleted in at least one gas among methane, hydrogen and carbon monoxide relative to the dry gas, and a residual gas (72), which is depleted in CO2 and enriched in at least one among methane, hydrogen and carbon monoxide relative to the dry gas; • expand the residual gas (72) in a Joule-Thomson valve (76), thereby cooling the residual gas; • reheat the expanded residual gas in a heat exchanger (50); • reheat the residual gas in a regeneration heater (80); and • regenerate an adsorbent bed inside the TSA (30) using the expanded and heated gas as the regeneration gas.

2. A method according to claim 1, wherein the dry gas contains a component selected from the list: helium, nitrogen, argon.

3. A method according to claim 1, wherein the syngas production unit is a self-thermal reformer.

4. A method according to claim 1, wherein the synthesis gas production unit is a steam methane reformer.

5. A method according to claim 1, wherein the syngas production unit is a partial oxidation unit.

6. A method according to claim 1, wherein the residual gas is expanded in the Joule-Thomson valve (76) to a temperature between -15 and -60°C before being reheated in the heat exchanger (50).

7. A method according to claim 1, wherein the regeneration gas used to regenerate the temperature-modulated adsorption unit is heated to a temperature between 120 and 250°C in the regeneration heater (80).

Images