Method and apparatus for generating a hydrogen-rich combustible gas

Abstract

Title of the invention: Method and apparatus for generating a hydrogen-rich combustible gas. An apparatus for producing hydrogen and combustible gas includes means for dividing a flow of gas containing hydrogen and CO2 to form a first and a second portion (P1, P2), a membrane separation unit (M), means for sending the first portion of the heated gas to the membrane separation unit, generating a permeate (P) enriched in H2 and depleted in CO2 relative to the heated gas and containing at least 90 mol% or even at least 95 mol% hydrogen and a residue (R) enriched in CO2 and depleted in hydrogen relative to the heated gas, means for sending the permeate to a combustible gas network, means for mixing the residue with the second portion of the heated gas which is not separated in the membrane separation unit, a pre-separation adsorption (PSA) unit.means for sending the mixture to the adsorption separation unit, generating a gas (H) enriched in hydrogen and depleted in CO2 relative to the heated gas and a residual gas (O) enriched in CO2 and depleted in hydrogen relative to the heated gas, a CO2 capture unit (CC), means for sending the residual gas to separate in the capture unit to generate a stream rich in pure CO2, a gas rich in hydrogen and a gas poor in CO2 and hydrogen, means for sending the hydrogen-rich gas to separate by adsorption in the adsorption unit and means for sending the gas poor in CO2 and hydrogen (RES) to the combustible gas network mixed with the permeate. FIG. 1,

Description

Title of the invention: Method and apparatus for generating a hydrogen-rich combustible gas

[0001] The present invention relates to a method and apparatus for generating a combustible gas rich in hydrogen.

[0002] This document describes an invention that may relate to a steam reforming hydrogen production unit (often referred to by the English acronym SMR) equipped with a cryogenic CO2 capture unit on the residual gas of an adsorption unit referred to by the acronym PSA which processes a gas from steam reforming, the PSA also producing a hydrogen-rich gas by separating the synthesis gas by pressure-switching adsorption.

[0003] Most of the hydrogen is produced by the steam reforming process, in which natural gas is reformed in the presence of steam to produce a hydrogen-rich synthesis gas, which is then purified and separated by a PSA unit. The residual gases from this PSA are then used as fuel, with natural gas added to preheat the feedstock and provide the heat of reaction.

[0004] The waste gases from the PSA are rich in H2 and CO2, and a CO2 capture unit can therefore be advantageously added to process this gas. A separation process by partial condensation and / or distillation and / or solidification makes it possible to capture the CO2 for production or sequestration, and to recover a large part of the hydrogen. This process therefore has several consequences for the steam reforming process: • Hydrogen production is increased by approximately 15% • CO2 emissions are reduced by approximately 60% • The consumption of natural gas used as fuel increases

[0005] In most cases, it is advantageous to produce more hydrogen. However, there may be times when it is not possible to sell the additional hydrogen production, or when reducing emissions by only 60% is insufficient.

[0006] The invention aims to provide a solution to at least one of these specific problems.

[0007] The principle of the invention is to cleverly produce a hydrogen-rich gas that can be used as fuel, in order to reduce hydrogen production while minimizing CO2 emissions from steam reforming.

[0008] The process includes an upstream treatment step of the PSA, allowing the reduction of the water content and possibly at least one alcohol content of the synthesis gas. By adding a membrane separation unit between this unit and the PSA, a hydrogen-rich permeate (e.g. >95 mol%) can be generated which can be used as a fuel gas.

[0009] In the dew point control unit, the gas is cooled to condense the water and possibly at least one alcohol, which are separated before the gas is reheated. The gas going to the membrane separation unit is therefore desaturated.

[0010] Only a first portion of the heated gas is sent to the membrane separation unit. The membrane separation unit generates a low-pressure permeate (for example, 2 bar) enriched in the most permeating elements, in practice hydrogen (>95 mol% hydrogen). The residue is optionally cooled before being mixed with the second portion of the heated gas that was not treated in the membrane separation unit.

[0011] To meet the fuel requirements of the SMR, it is not necessary to process all the synthesis gas in the membrane separation unit.

[0012] This system has several advantages: • At the cost of reduced hydrogen production, it allows for a reduction in the need for natural gas used as fuel, or its complete replacement, and therefore also a reduction in CO2 emissions. For an equivalent furnace load, the emission reduction can increase from approximately 60% with a CO2 capture unit using partial condensation and distillation to approximately 75% with the addition of the membrane unit. The natural gas supplement can be replaced if a reliable and stable hydrogen source is available, such as a network supplied by other sources. • Due to the reduction in the H2 content of the gas feeding the PSA, the residual is enriched in CO2. This reduces the size of the CO2 capture unit by partial condensation and / or distillation and / or solidification and increases its efficiency. • When CO2 is commercially utilized, for example for the food market, it is possible to modulate hydrogen production independently of CO2 production by adjusting the flow rate of the second portion of the gas which is not sent to the membrane separation unit but goes directly to adsorption separation. • A large part (e.g. about 80%) of the water present in the gas is removed in the membrane separation unit, which further desaturates the gas sent to the PSA adsorption unit with water and limits the risks of condensation and the drying requirements in the capture drying unit.

[0013] According to one object of the invention, a process for producing hydrogen and combustible gas is provided in which: a. A flow of gas containing hydrogen, CO2 and water, and possibly carbon monoxide and / or nitrogen, is cooled to condense the water it contains and produce a gas with a reduced water content, which is then possibly reheated. b. The possibly heated gas is divided to form a first portion and a second portion; the first portion of the heated gas is sent to a membrane separation unit, generating a permeate enriched in H2 and depleted in CO2 compared to the heated gas and containing at least 90 mol% or even at least 95 mol% hydrogen, and a residue enriched in CO2 and depleted in hydrogen compared to the heated gas. c. The permeate is sent to a combustible gas network d. The residue is mixed with the second portion of the reheated gas that is not separated in the membrane separation unit, then the mixture is sent to an adsorption separation unit, generating a gas enriched in hydrogen and depleted in CO2 compared to the reheated gas and a residual gas enriched in CO2 and depleted in hydrogen compared to the reheated gas and e. The waste gas is separated at a temperature below -50°C by partial condensation and / or distillation and / or solidification in a CO2 capture unit to generate a CO2-rich stream, a hydrogen-rich gas which is separated by adsorption in the adsorption unit and a CO2- and hydrogen-poor gas which is also returned to the combustible gas network mixed with the permeate.

[0014] According to other optional aspects: • The first portion of the gas, possibly heated, sent to the membrane separation unit is preheated • The residue is cooled upstream of the adsorption unit • The residue is cooled before being mixed with the second portion • The second portion of the gas, possibly heated, sent to the adsorption separation unit, is not heated between the division of the two portions and the adsorption separation unit. • The gas flow originates from a steam reforming unit associated with a combustion unit, which provides heat for the steam reforming unit, and the combustible gas network supplies the combustion unit with fuel • All fuel sent to the combustion unit comes from the CO2 capture unit and the membrane separation unit • Natural gas is also sent to the combustion unit as fuel • A flow of hydrogen from an external source, for example a hydrogen distribution network, is also sent to the combustion unit as fuel • The first portion of the heated gas contains water, and the permeate of the membrane unit contains more water than the first portion of the heated gas. • The hydrogen-enriched gas from the capture unit is sent to separate in the adsorption separation unit, preferably without having been compressed between the capture unit and the adsorption separation unit • the permeate contains at least 95 mol% hydrogen • The permeate is produced or exits the membrane unit at between 1.7 and 3 bars • A CO2-rich stream contains at least 90% mol CO2, at least 95% mol CO2, or at least 99% mol CO2 • a hydrogen-rich gas contains at least 90% mol H2, at least 95% mol H2, or even at least 99% mol H2 • a gas low in CO2 and hydrogen contains less than 90% mol CO2, less than 60% mol CO2 or less than 40% mol CO2 • a gas low in CO2 and hydrogen contains less than 90% mol H2, less than 60% mol H2, or less than 40% mol H2 • the proportions of the two portions.

[0015] According to another object of the invention, an apparatus for the production of hydrogen and combustible gas is provided, comprising means for cooling a flow of gas containing hydrogen, CO2 and water, and optionally carbon monoxide and / or nitrogen, to condense the water it contains and produce a gas with a reduced water content, optionally means for heating the gas with a reduced water content, means for dividing the optionally heated gas to form a first portion and a second portion, a membrane separation unit, means for sending the first portion of the heated gas to the membrane separation unit, generating a permeate enriched in H2 and depleted in CO2 with respect to the optionally heated gas and containing at least 90 mol% or even at least 95 mol% hydrogen, and a residue enriched in CO2 and depleted in hydrogen with respect to the optionally heated gas.means for sending the permeate to a combustible gas network, means for mixing the residue with the second portion of the possibly reheated gas that is not separated in the membrane separation unit, an adsorption separation unit, means for sending the mixture to the adsorption separation unit, generating a gas enriched in hydrogen and depleted in CO2 compared to the possibly heated gas and a residual gas enriched in CO2 and depleted in hydrogen compared to the possibly heated gas, a CO2 capture unit, means for sending the residual gas to separate in the capture unit at a temperature below -50°C by partial condensation and / or distillation and / or solidification to generate a stream rich in pure CO2, a gas rich in hydrogen and a gas poor in CO2 and hydrogen, means for sending the gas rich in hydrogen to separate by adsorption in the adsorption unit and means for sending the gas poor in CO2 and hydrogen to the combustible gas network mixed with the permeate.

[0016] According to one object of the invention, an integrated process for the production of synthesis gas, hydrogen, and combustible gas is provided, in which: a. A flow of syngas is produced by a steam reforming unit associated with a combustion unit that produces heat for the steam reforming unit. b. A flow of gas containing hydrogen, CO2 and water, and possibly carbon monoxide and / or nitrogen, consisting of synthesis gas, treated to reduce its carbon monoxide content, is cooled to condense the water it contains and produce a gas with a reduced water content, which is then possibly reheated. c. The possibly heated gas is divided to form a first portion and a second portion; the first portion of the heated gas is sent to a membrane separation unit, generating a permeate enriched in H2 and depleted in CO2 compared to the possibly heated gas and containing at least 90 mol% or even at least 95 mol% hydrogen, and a residue enriched in CO2 and depleted in hydrogen compared to the possibly heated gas. d. The permeate is sent to a combustible gas network e. The residue is mixed with the second portion of the possibly heated gas that is not separated in the membrane separation unit, then the mixture is sent to an adsorption separation unit, generating a gas enriched in hydrogen and depleted in CO2 compared to the possibly heated gas and a residual gas enriched in CO2 and depleted in hydrogen compared to the possibly heated gas f. The waste gas is separated at a temperature below -50°C by partial condensation and / or distillation and / or solidification in a CO2 capture unit to generate a CO2-rich stream, a hydrogen-rich gas which is separated by adsorption in the adsorption unit, and a CO2-poor gas. CO2 and hydrogen, which is also returned to the combustible gas network mixed with the permeate and g. The combustible gas from the network is sent to the combustion unit with natural gas and / or hydrogen from at least one external source.

[0017] The invention will be described in more detail with reference to the figure:

[0018] [Fig-1] schematically represents a method according to the invention.

[0019] In [Fig.1], we see a water condensation unit E, a membrane separation unit M, a pressure-switching adsorption separation unit PSA and a CO2 capture unit by partial condensation and / or distillation and / or solidification CC.

[0020] In a process for producing hydrogen HG and combustible gas F, a flow of gas containing hydrogen, carbon monoxide, and water, and optionally carbon monoxide and / or nitrogen and / or at least one alcohol, is cooled by a heat exchanger and then cooled by a chiller RI using cooling water CW to condense water W and optionally at least one alcohol it contains.

[0021] After separation of the water W in a separator S, a gas with reduced water content is produced which is then optionally heated in the heat exchanger E against the gas flow upstream of the cooler RL

[0022] The optionally heated gas is divided into two to form a first portion and a second portion. The first portion PI of the optionally heated gas before division with P2 is optionally heated by a heater H supplied with water HW, then is sent to a membrane separation unit, generating a permeate P enriched in H2 and preferably in water and depleted in CO2 compared to the optionally heated gas and containing at least 90 mol% or even at least 95 mol% of hydrogen and a residue R enriched in CO2 and depleted in hydrogen and preferably in water compared to the optionally heated gas.

[0023] The permeate P is sent to a combustible gas network F at a pressure between 1.7 and 3 bars.

[0024] The residue R is cooled by a cooler R2 and then mixed with the second portion P2 of the possibly heated gas which is not separated in the membrane separation unit M and then the mixture is sent to an adsorption separation unit PSA, generating a gas HG enriched in hydrogen and depleted in CO2 compared to the possibly heated gas and a residual gas O enriched in CO2 and depleted in hydrogen compared to the possibly heated gas.

[0025] The residual gas O is compressed, purified into water, cooled and then separated at a temperature below -50°C by partial condensation and / or distillation and / or solidification in a CO2 capture unit to generate a CO2-rich stream pure, a hydrogen-rich gas HRG which is possibly compressed and separated by adsorption in the PSA adsorption unit and a CO2 and hydrogen-poor RES gas which is also returned to the combustible gas network mixed with the permeate P.

[0026] Sending hydrogen-rich gas HRG from the CC capture unit after compression as PSA feed gas, for example, makes it possible to increase the proportion of hydrogen sent to the fuel gas network F and therefore the decarbonization rate.

[0027] Examples of the CC CO2 capture unit are described in FR2877939, FR2904780, EP2227309, FR2993187, FR3141077 and FR3144927 and are adapted to separate a mixture containing carbon dioxide, hydrogen and possibly nitrogen and / or carbon monoxide.

[0028] The fuel gas network F can supply a combustion unit (called a "furnace") associated with a steam reforming unit, which produces the heat required for steam reforming. Steam reforming produces the flow of gas to be separated according to the invention, first forming a synthesis gas whose carbon monoxide is converted into carbon dioxide by a shift process.

[0029] The combustion unit can also be supplied by a flow of natural gas but in reduced quantity, thanks to the supply of fuel from the capture unit and the membrane separation unit.

[0030] The combustion unit can also be supplied with a flow of gaseous hydrogen from an external source, such as, for example, a hydrogen distribution network. This hydrogen can replace at least part of the natural gas. Supplying hydrogen from a reliable and readily available source (for example, a hydrogen distribution network) makes it possible to achieve a decarbonization rate exceeding 95% or even 98%.

Claims

Demands

1. A process for producing hydrogen and combustible gas in which: a. A flow of gas containing hydrogen, CO2 and water, and possibly carbon monoxide and / or nitrogen, is cooled (E) to condense the water (W) it contains and produce a gas with a reduced water content, which is then possibly reheated (E) b. The possibly heated gas is divided to form a first portion (PI) and a second portion (P2). The first portion of the heated gas is sent to a membrane separation unit (M), generating a permeate (P) enriched in H2 and depleted in CO2 compared to the heated gas and containing at least 90 mol% or even at least 95 mol% hydrogen, and a residue (R) enriched in CO2 and depleted in hydrogen compared to the heated gas. c. The permeate is sent to a combustible gas network (F). d. The residue is mixed with the second portion of the possibly reheated gas that is not separated in the membrane separation unit, then the mixture is sent to a power-suppression adsorption (PSA) unit, generating a gas (HG) enriched in hydrogen and depleted in CO2 compared to the possibly reheated gas, and a residual gas (O) enriched in CO2 and depleted in hydrogen compared to the possibly reheated gas. e. The residual gas is separated at a temperature below -50°C by partial condensation and / or distillation and / or solidification in a CO2 capture unit (CC) to generate a CO2-rich stream (CO2), a hydrogen-rich gas (HRG) which is separated by adsorption in the adsorption unit and a CO2- and hydrogen-poor gas (RES) which is also returned to the network (F) of combustible gas mixed with the permeate.

2. The method according to claim 1, wherein the first portion (PI) of the optionally heated gas sent to the membrane separation unit (M) is preheated (H), then the residue (R) is cooled (R2) while the second portion (P2) of the gas possibly heated sent to the adsorption separation unit (PSA) is not heated between the division of the two portions and the adsorption separation unit.

3. A method according to claim 1 or 2 wherein the gas flow originates from a steam reforming unit associated with a combustion unit which provides heat for the steam reforming unit and the combustible gas network (F) supplies the combustion unit with fuel.

4. A method according to claim 3 wherein all the fuel (F) sent to the combustion unit comes from the CO2 capture unit (CC) and the membrane separation unit (M).

5. A method according to claim 3 wherein natural gas is also sent to the combustion unit as fuel.

6. A method according to claim 3 or 5 wherein a flow of hydrogen from an external source, for example a hydrogen distribution network, is also sent to the combustion unit as fuel.

7. A process according to any one of the preceding claims wherein the first portion (PI) of the heated gas contains water and the permeate (P) of the membrane unit (M) contains more water than the first portion of the heated gas.

8. A method according to any one of the preceding claims wherein the hydrogen-enriched gas (HRG) from the capture unit (CC) is sent to separate in the adsorption separation unit (PSA), preferably without having been compressed between the capture unit and the adsorption separation unit.

9. A method according to any one of the preceding claims wherein the permeate (P) exits the membrane unit (M) at between 1.7 and 3 bars.

10. Apparatus for the production of hydrogen and combustible gas comprising means (E) for cooling a flow of gas containing hydrogen, CO2, and water, and optionally carbon monoxide and / or nitrogen, to condense the water contained therein and produce a gas with a reduced water content, optionally means for heating the gas with a reduced water content, means for dividing the optionally heated gas to form a first portion (P1) and a second portion (P2), a membrane separation unit (M), means for sending the first portion of the optionally heated gas to the unit membrane separation, generating a permeate (P) enriched in H2 and depleted in CO2 relative to the heated gas and containing at least 90 mol% or even at least 95 mol% hydrogen and a residue (R) enriched in CO2 and depleted in hydrogen relative to the possibly heated gas, means for sending the permeate to a combustible gas network (F), means for mixing the residue with the second portion of the possibly heated gas which is not separated in the membrane separation unit, an adsorption separation unit (PSA), means for sending the mixture to the adsorption separation unit, generating a gas (H) enriched in hydrogen and depleted in CO2 relative to the heated gas and a residual gas (O) enriched in CO2 and depleted in hydrogen relative to the heated gas, a CO2 capture unit (CC),means for sending the residual gas to separate in the capture unit at a temperature below -50°C by partial condensation and / or distillation and / or solidification to generate a stream rich in pure CO2, a hydrogen-rich gas (HRG) and a gas (RES) low in CO2 and hydrogen; means for sending the hydrogen-rich gas to separate by adsorption in the adsorption unit; and means for sending the gas low in CO2 and hydrogen to the combustible gas network mixed with the permeate.

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