Method for separating carbon dioxide from synthesis gas
By adsorbing and desorbing the absorption medium on the solid adsorbent, the problems of high carbon dioxide separation energy and equipment complexity in the synthesis gas are solved, and high-efficiency and low-energy consumption are achieved.
Patent Information
- Application Number
- CN202510022157.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-01-08
- Filing Date
- 2025-01-07
- Publication Date
- 2025-07-08
AI Technical Summary
When separating carbon dioxide from syngas, the prior art has problems such as high energy requirements, the need for additional equipment and additives, corrosive media resulting in high equipment material requirements and complex water separation.
The solid adsorbent adsorbent is used to absorb the absorption medium, and the absorption medium in the carbon dioxide product stream is removed on the solid adsorbent through adsorption and desorption steps, and the regeneration of the medium is achieved by circulating the regeneration gas stream to avoid media loss and additional energy input.
It realizes efficient separation and recovery of carbon dioxide, reduces energy consumption and equipment complexity, avoids media loss and corrosion problems, and simplifies the water separation process.
Smart Images
Figure CN120270966A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present invention relates to a method and an apparatus for separating carbon dioxide from a synthesis gas stream comprising at least hydrogen (H2) and carbon dioxide (CO2). BACKGROUND OF THE INVENTION
[0002] In the case of hydrogen production from synthesis gas, carbon dioxide is formed during the reforming of fossil raw materials and in the downstream water gas shift. The resulting synthesis gas mixture, which now contains hydrogen and carbon dioxide as its main components, is then freed of carbon dioxide. The resulting carbon dioxide stream can be further used or sequestered. For further use, depending on the specific application, the stream can be provided in gaseous or liquid form.
[0003] If a liquid carbon dioxide product is required, liquefaction is usually achieved by cooling and compression. This presupposes that the carbon dioxide is substantially free of trace impurities that impair liquefaction and is free of water, thus preventing freezing in the equipment used during cooling below the freezing point of water.
[0004] Physical or chemical absorption methods can be used to remove carbon dioxide from the shifted synthesis gas.
[0005] Absorption media that can be used in physical absorption methods can be solvents such as methanol, N-methyl-2-pyrrolidone, mixtures of dimethyl ethers of polyethylene glycols, and propylene carbonate (4-methyl-1,3-dioxolan-2-one).
[0006] Absorption media that can be used in physical absorption methods can be solvents such as methanol, N-methyl-2-pyrrolidone, mixtures of dimethyl ethers of polyethylene glycols, and propylene carbonate (4-methyl-1,3-dioxolan-2-one).
[0007] Absorption media that can be used in chemical scrubbing operations include, in particular, amines such as monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA), diethylene glycolamine (DGA), or aminomethylpropanol (AMP). The effect of chemical absorption can be enhanced by a promoter such as piperazine (PZ). Ammonia solutions, especially aqueous ammonia solutions, are also known as absorption media for carbon dioxide.
[0008] In the above methods, there are residual amounts of the absorption medium in the carbon dioxide product after desorption from the absorption medium that are intolerable for the liquefaction of carbon dioxide, and these must therefore be removed.
[0009] When using a polar, i.e., water-soluble, absorption medium, it can be removed by washing with water in a separate scrubbing column.
[0010] However, such a configuration has several disadvantages. First, additional auxiliaries are required, namely demineralized water or boiler feed water. Second, an additional column dedicated to the water wash operation is needed. Third, specific components in contact with this medium must be made of stainless steel because carbon dioxide and water form carbonic acid, which is a corrosive medium. Fourth, another system for separating water from carbon dioxide must be integrated into the device. Fifth, the wash water must be thermally separated from the methanol that is removed by distillation in the distillation column that is normally present. Due to the large additional amount of water, this increases the energy requirement of the process.
[0011] Another means of removing the absorption medium is to condense it by providing cooling energy, for example, in a heat exchanger operating with a coolant, and then recycle the absorption medium to the absorption column. The disadvantages of this solution are the high energy demand and the need for additional equipment. Summary of the Invention
[0012] Therefore, generally speaking, the object of the present invention is to overcome at least partially the above-mentioned disadvantages.
[0013] The independent claims contribute to at least partially achieving at least one of the above objects. The dependent claims provide preferred embodiments that contribute to at least partially achieving at least one object. The preferred embodiments of the components of one category according to the present invention are equally preferred for the components of the same name or corresponding components of each other category according to the present invention in relevant cases.
[0014] Terms such as "having", "comprising", or "containing" do not exclude the possible existence of other elements, components, etc. The indefinite article "a" does not exclude the possible existence of a plurality.
[0015] The object of the present invention is achieved at least partially by a method for separating carbon dioxide from a syngas stream containing at least hydrogen (H2) and carbon dioxide (CO2), the method having the following method steps
[0016] (a) Providing an absorption medium;
[0017] (b) Removing carbon dioxide from the syngas stream by absorption to obtain a carbon dioxide-loaded absorption medium and a hydrogen-containing product stream;
[0018] (c) Desorbing carbon dioxide from the loaded absorption medium by a desorption step to obtain a carbon dioxide-lean absorption medium and a carbon dioxide product stream containing the absorption medium;
[0019] (d) Removing the absorption medium from the carbon dioxide product stream containing the absorption medium by adsorbing the absorption medium on a solid adsorbent to obtain a carbon dioxide product stream and an adsorbent loaded with the absorption medium;
[0020] (e) Discharging a first sub-stream of the carbon dioxide product stream from the method;
[0021] (f) Heating a second sub-stream of the carbon dioxide product stream to a desorption temperature to obtain a regeneration gas stream and passing the regeneration gas stream through the loaded adsorbent to obtain a regenerated adsorbent by desorbing the absorption medium from the adsorbent and a regeneration gas stream containing the absorption medium.
[0022] According to the invention, the absorption medium entrained in the carbon dioxide product stream is removed by adsorption on a solid adsorbent. The adsorbent loaded with the absorption medium is then regenerated by means of a heated sub-stream of the carbon dioxide product stream free of the absorption medium. Since the product stream is used as the regeneration stream and can be recycled to the plant as a separate stream together with the desorbed absorption medium, there is no loss of the absorption medium and the carbon dioxide product.
[0023] In one embodiment, the regeneration gas stream containing the absorption medium is thus subsequently returned to the method.
[0024] One preferred embodiment of the method is characterized in that a physical absorption medium is provided in step (a), carbon dioxide is removed by physical absorption at an absorption pressure in step (b), and carbon dioxide is desorbed at a desorption pressure by at least one depressurization step, wherein the desorption pressure is lower than the absorption pressure.
[0025] The physical absorption medium is preferably methanol. In this case, step (a) preferably comprises providing methanol as the physical absorption medium. Carbon dioxide is preferably absorbed in methanol at low temperatures, particularly at cryogenic temperatures, in the absorption device according to step (b). The absorption at the absorption pressure is preferably carried out in the absorption device. Methanol preferably has a temperature below -10 °C or below -20 °C or below -30 °C or below -40 °C before entering the absorption device. Methanol preferably has a temperature above -70 °C or above -60 °C before entering the absorption device.
[0026] The absorption device is configured as, for example, an absorption tower and operates at the absorption pressure. The absorption pressure is an elevated pressure, particularly a pressure significantly higher than the ambient pressure, particularly a pressure greater than 20 bar or greater than 30 bar, for example 20 to 80 bar, preferably 25 to 70 bar, more preferably 35 to 55 bar, more preferably 35 to 45 bar.
[0027] In step (c), desorption is carried out from the absorption medium by reducing the pressure to the desorption pressure, i.e., carbon dioxide is released again. The desorption is preferably carried out in a suitable regeneration device. The regeneration device preferably has a plurality of series-connected flash stages. The flash stages are configured as, for example, flash towers or flash evaporators. "Series-connected" particularly means that the plurality of flash stages are successively connected and in fluid communication with each other, particularly that two directly successive flash stages are in fluid communication. The pressure in any flash stage is lower than the absorption pressure and preferably decreases from flash stage to flash stage in the flow direction of the absorption medium. Thus, the pressure in any downstream flash stage is substantially lower than the pressure in the flash stage upstream of this flash stage.
[0028] A preferred embodiment of the method is characterized in that a chemical absorption medium is provided in step (a), carbon dioxide is removed by chemical absorption at the absorption temperature in step (b), and carbon dioxide is desorbed at the regeneration temperature by at least one heating step in step (c), wherein the regeneration temperature is higher than the absorption temperature.
[0029] The chemical absorption medium is preferably an amine. Available absorption media include one or a mixture of the above-mentioned amines. Carbon dioxide is absorbed in the chemical absorption medium at the absorption temperature, for example, at ambient temperature. Carbon dioxide is desorbed from the chemical absorption medium at the regeneration temperature, which is higher than the absorption temperature. An example is to heat the loaded amine solution at the bottom of the regeneration tower by indirect heat exchange with steam to desorb carbon dioxide from the amine.
[0030] The synthesis gas is preferably produced by reforming or steam reforming of fossil raw materials, or by gasification of carbonaceous solids.
[0031] The raw material is preferably natural gas, another hydrocarbon source of fossil origin, or biomass. Examples of carbonaceous solids are wastes such as municipal solid waste and wood processing waste.
[0032] Examples of reforming methods for producing synthesis gas are autothermal reforming (ATR), partial oxidation (POx), and gasification methods such as fixed-bed gasification, entrained flow gasification, and fluidized-bed gasification.
[0033] The synthesis gas produced as a primary product by reforming, steam reforming, or gasification contains at least hydrogen, carbon monoxide, and carbon dioxide. By means of the water-gas shift, which is preferably carried out downstream, carbon monoxide reacts with water to obtain carbon dioxide and hydrogen. The resulting synthesis gas has hydrogen and carbon dioxide as its main components.
[0034] The hydrogen product stream obtained in step (b) should be considered as a crude hydrogen product and impurities can be removed by further suitable measures. In particular, suitable methods for this purpose include pressure swing adsorption (PSA) and membrane separation using a hydrogen-selective membrane.
[0035] For step (d), the typical amount of the absorption medium relative to the carbon dioxide product stream is from 200 ppmv to 2000 ppmv, in particular from 500 ppmv to 1500 ppmv.
[0036] In a preferred embodiment, in the case of physical absorption, at least one flashing step is provided in a flash column in step (c) and at least a part of the regenerated stream containing the absorption medium is fed into the flash column.
[0037] A "flashing step" herein refers to a pressure reduction step in which the target pressure is always lower than the absorption pressure.
[0038] The regenerated gas stream containing the absorption medium is at an elevated temperature. This enhances the effect related to the desorption or stripping of carbon dioxide in the flash column without any additional energy input. If multiple flash sections are provided, the regenerated gas stream containing the absorption medium can be fed into any desired flash section. The regenerated gas stream containing the absorption medium is preferably at a pressure of 5 bar or lower and is fed into a flash section having a corresponding or lower pressure.
[0039] In a preferred embodiment, in the case of physical absorption, a thermal regeneration step is provided in a thermal regeneration column in step (c) in the flow direction of the absorption medium and at least a part of the regenerated gas stream containing the absorption medium is fed into the thermal regeneration column.
[0040] Such a configuration also enhances the effect related to the desorption or stripping of carbon dioxide in the thermal regeneration column without any additional energy input.
[0041] In a preferred embodiment, the method includes at least one distillation step in a distillation column for thermally removing the water entrained by the syngas from the absorption medium and at least a part of the regenerated gas stream containing the absorption medium is fed into the distillation column.
[0042] In such a configuration, the heat introduced by the recirculation of the regenerated gas stream containing the absorption medium contributes to the thermal separation of the absorption medium from water, preferably the thermal separation of methanol from water. In addition, the regenerated gas stream containing the absorption medium may also contain water. This water may be entrained into the process by the syngas. Therefore, this water is not introduced into the absorption medium circuit, otherwise it may impair the effect of the absorption medium.
[0043] A preferred embodiment of the method comprises heating a second sub-stream of the carbon dioxide product stream to a desorption temperature of 75 °C to 225 °C, preferably 100 °C to 200 °C, more preferably 125 °C to 175 °C.
[0044] In a further preferred embodiment of the method, the proportion of the volume flow rate of the second sub-stream in the volume flow rate of the total stream of the carbon dioxide product stream is in the range of 1% to 25%, preferably in the range of 5% to 20%, more preferably in the range of 10% to 15%.
[0045] In a further embodiment of the method, at least one additional adsorbent may be arranged downstream of the adsorbent, in particular at least one additional adsorbent in at least one fixed bed. The at least one additional adsorbent is arranged to adsorb further impurities present in the syngas. In particular, the at least one additional adsorbent adsorbs and removes at least one of the following components
[0046] - cyanide-containing compounds (in particular hydrogen cyanide),
[0047] - sulfur-containing compounds (in particular hydrogen sulfide, carbon disulfide, mercaptans, carbonyl sulfide, sulfur-containing heteroaromatic compounds such as thiophene), and
[0048] - ammonia.
[0049] More preferably, the absorption medium is adsorbed on the adsorbent due to the molecular sieve effect of the adsorbent.
[0050] The adsorbent is preferably arranged in a fixed bed reactor.
[0051] In an embodiment of the method preferred herein, the method comprises at least two fixed bed reactors, wherein
[0052] i. In a first fixed period of time, the adsorbent in the first fixed bed reactor is loaded, wherein the carbon dioxide product stream containing the absorption medium is passed through it, and the adsorbent in the second fixed bed reactor is regenerated, wherein the regeneration gas stream is passed through it, and
[0053] ii. In a second fixed period of time at least partially following the first period, the adsorbent in the first fixed bed reactor is regenerated, wherein the regeneration gas stream is passed through it, and the adsorbent in the second fixed bed reactor is loaded, wherein the carbon dioxide product stream containing the absorption medium is passed through it.
[0054] It is also possible to remove the absorption medium from the carbon dioxide product stream by means of two or more fixed bed reactors.
[0055] Preferably, a multi-bed arrangement is selected such that at least one fixed bed can be regenerated while the other fixed beds are still in the adsorption mode and removing the absorption medium from the carbon dioxide product stream. At the end of the regeneration, the fixed bed involved is switched back to the adsorption mode, and another fixed bed with partially or fully loaded adsorbent is switched to the regeneration mode.
[0056] In this regard, the terms "loaded" and "regenerated" do not necessarily mean that the respective fixed bed is completely loaded with the absorption medium or completely stripped of the absorption medium.
[0057] A preferred embodiment of the method comprises desorbing the absorption medium from the adsorbent at a pressure lower than the adsorption pressure used in step d) for adsorbing the absorption medium onto the adsorbent.
[0058] The absorption medium is adsorbed onto the solid adsorbent at the adsorption pressure. This adsorption pressure can be the pressure corresponding to the desorption pressure in step (c) in the case of physical absorption, or a higher pressure. In the latter case, compression of the carbon dioxide stream obtained in step (c) is required. To facilitate desorption of the absorption medium from the adsorbent, the pressure is reduced during desorption with the regeneration gas stream compared to the adsorption pressure.
[0059] A preferred embodiment of the method comprises liquefying a first sub-stream of the carbon dioxide product stream by means of at least one cooling step and at least one condensation step.
[0060] In a further preferred embodiment of the method, the adsorbent is also arranged to adsorb water.
[0061] The water is in particular water entrained in the synthesis gas, i.e., water that cannot be completely removed by cooling and condensation before the gas scrubbing operation with the absorption medium.
[0062] In a further preferred embodiment of the method, the method comprises a solid gasifier for gasifying a carbonaceous feedstock to produce synthesis gas, and wherein at least a part of the regeneration gas stream containing the absorption medium is fed into the solid gasifier.
[0063] The solid gasifier is configured to produce synthesis gas from a carbonaceous feedstock. The carbonaceous feedstock is preferably biomass and / or municipal solid waste. The synthesis gas produced by the solid gasifier contains at least hydrogen, carbon monoxide and carbon dioxide. A water gas shift section is particularly connected downstream of the solid gasifier for the reaction of carbon monoxide with water to produce hydrogen and carbon dioxide, thereby obtaining a synthesis gas stream.
[0064] The regeneration gas stream containing the absorption medium can be used in particular to maintain the pressure in the solid gasifier. In addition, the carbon dioxide in the regeneration gas stream can be used as a moderator for the gasification reaction. In this way, for example, it is possible to dispense with the supply of steam as a dedicated moderator.
[0065] The objects of the present invention are also at least partially achieved by a plant for producing hydrogen from a synthesis gas stream comprising at least hydrogen (H 2 ) and carbon dioxide (CO 2 ), the plant having the following plant components (plant components) connected in fluid connection:
[0066] (a) providing means for absorbing the medium;
[0067] (b) means for removing carbon dioxide from said synthesis gas stream by absorption, whereby an absorption medium loaded with carbon dioxide and a product stream comprising hydrogen are obtained;
[0068] (c) means for desorbing carbon dioxide from the loaded absorption medium, whereby an absorption medium depleted in carbon dioxide and a carbon dioxide product stream comprising the absorption medium are obtained;
[0069] (d) means for removing absorption medium from the carbon dioxide product stream comprising the absorption medium, wherein the means comprises at least one fixed bed comprising a solid adsorbent and the absorption medium is removed from the carbon dioxide product stream comprising the absorption medium by adsorbing the absorption medium on the solid adsorbent in the fixed bed, whereby a carbon dioxide product stream and an adsorbent loaded with the absorption medium are obtained;
[0070] (e) means for removing a first substream of the carbon dioxide product stream from the process;
[0071] (f) means for heating a second substream of the carbon dioxide product stream to a desorption temperature, thereby obtaining a regeneration gas stream, and means for passing the regeneration gas stream through the loaded adsorbent, so that adsorbent regenerated by desorbing the absorption medium from the adsorbent and a regeneration gas stream containing the absorption medium are obtained. BRIEF DESCRIPTION OF THE DRAWINGS
[0072] Figure 1 is a highly simplified block flow diagram of a method in one operational embodiment of the present invention. DETAILED DESCRIPTION
[0073] The following operating examples explain the present invention in detail with reference to the accompanying drawings. The operating examples constitute illustrative configurations of the present invention, rather than limiting its scope.
[0074] The figure shows:
[0075] Figure 1 It is a highly simplified block flow chart of the method in an operating embodiment of the present invention.
[0076] The gas stream is shown by a dashed line, while the liquid stream is shown by a solid line. The gas stream may contain a liquid phase, and the liquid stream may contain a gas phase. The arrows indicate the flow direction of the specific stream. In this embodiment, carbon dioxide is removed by physical absorption. The absorption medium is methanol.
[0077] A syngas stream 2 having hydrogen and carbon dioxide as its main components is supplied to an absorption column 4 in the lower region. A methanol stream 7 consisting of regenerated methanol is supplied to the absorption column 4 in the top region. In the absorption column 4 operating at an elevated pressure (e.g., 40 bar), the syngas stream 2 and the methanol stream 7 are conveyed countercurrently. Inside the absorption column 4, the methanol stream has a temperature below -30 °C. The absorption medium (methanol) absorbs carbon dioxide from the syngas stream 2. The hydrogen stream 3 is discharged from the top region of the absorption column 4 and can be sent for further purification, e.g., by pressure swing adsorption (not shown).
[0078] Accordingly, a methanol stream 5 loaded with carbon dioxide is discharged from the bottom of the absorption column 4 and fed into a flash system 6. The flash system 6 may comprise a plurality of flash towers in series (not shown). In the flash system 6, carbon dioxide is desorbed from the methanol stream 5 loaded with carbon dioxide. This provides a regenerated methanol stream 7. At the same time, a carbon dioxide product stream 8 is obtained, which contains approximately 1000 ppmv of methanol. In addition, this stream may contain water. First, the pressure of this carbon dioxide product stream 8 is increased by a compressor 17 to facilitate the subsequent adsorption of methanol and optionally water on an adsorbent. Then, the compressed carbon dioxide product stream 9 containing methanol is cooled to approximately 40 °C by a heat exchanger 15.
[0079] The compressed and cooled methanol-containing carbon dioxide product stream 10 is then fed into a fixed bed reactor system 22 having at least two fixed bed reactors (not shown). In each case, a fixed bed of adsorbent is provided within the fixed bed reactor, which removes methanol and water from the methanol-containing carbon dioxide product stream 10 due to the molecular sieve effect. After the methanol (and any water) has been adsorbed onto the adsorbent, the corresponding fixed bed is regenerated. This is achieved by splitting off a sub-stream 14 from the resulting methanol-free carbon dioxide product stream 12 and heating it to approximately 150 °C by means of a heat exchanger 16. This provides a regeneration gas stream 23, which is passed through the corresponding fixed adsorption bed of the fixed bed reactor system 22. At the same time, another fixed bed reactor of the fixed bed reactor system 22 can be loaded with methanol and any water from the compressed stream 10. During the regeneration by means of the regeneration gas stream 23, the pressure in the corresponding fixed bed is reduced. The methanol-containing regeneration gas stream 11 generated during the regeneration is returned to the flash system 6. Thus, no loss of carbon dioxide and methanol occurs during the entire process of this method. Alternatively or additionally, the regeneration gas stream 11 can be fed into a distillation column (not shown). Thus, any water present in the regeneration gas stream is not entrained into the methanol circuit of the gas scrubbing process.
[0080] A sub-stream 13 of the carbon dioxide product stream is compressed in a compressor 18 and then fed as a compressed, now methanol- and water-free carbon dioxide product stream 19 into a carbon dioxide liquefaction unit 21. In the unit 21, the carbon dioxide is liquefied by means of a plurality of cooling steps and subsequent condensation. The unit 21 can also additionally have a cryogenic distillation step for further purifying the carbon dioxide product stream 19.
[0081] List of reference numerals
[0082] 1 Method
[0083] 2 Syngas stream
[0084] 3 Hydrogen stream
[0085] 4 Absorption column
[0086] 5 Methanol stream loaded with carbon dioxide
[0087] 6 Flash system
[0088] 7 Regenerated methanol stream
[0089] 8 Methanol-containing carbon dioxide product stream
[0090] 9 Methanol-containing carbon dioxide product stream (compressed)
[0091] 10 Methanol-containing carbon dioxide product stream (compressed, cooled)
[0092] 11 Methanol-containing regenerated gas stream
[0093] 12 Carbon dioxide product stream (whole stream, excluding methanol)
[0094] 13 Carbon dioxide product stream (first sub-stream)
[0095] 14 Carbon dioxide product stream (second sub-stream)
[0096] 15, 16 Heat exchangers
[0097] 17, 18 Compressors
[0098] 19 Carbon dioxide product stream (first sub-stream, compressed)
[0099] 20 Carbon dioxide product stream (liquefied)
[0100] 21 Carbon dioxide liquefaction unit
[0101] 22 Fixed bed reactor system
[0102] 23 Regenerated gas stream
Claims
1. A method (1) for separating carbon dioxide from a synthesis gas stream (2) comprising at least hydrogen (H2) and carbon dioxide (CO2), the method having the following method steps (a) providing an absorption medium; (b) removing carbon dioxide from the synthesis gas stream (2) by absorption to obtain a carbon dioxide-loaded absorption medium (5) and a hydrogen-containing product stream (3); (c) desorbing carbon dioxide from the loaded absorption medium (5) by a desorption step to obtain a carbon dioxide-lean absorption medium (7) and a carbon dioxide product stream (8) containing the absorption medium; (d) removing the absorption medium from the carbon dioxide product stream (8) containing the absorption medium by adsorbing the absorption medium on a solid adsorbent to obtain a carbon dioxide product stream (12) and an adsorbent loaded with the absorption medium; (e) discharging a first sub-stream (13) of the carbon dioxide product stream (12) from the method; (f) heating a second sub-stream (14) of the carbon dioxide product stream to a desorption temperature to obtain a regeneration gas stream (23), and passing the regeneration gas stream (23) through the loaded adsorbent to obtain an adsorbent regenerated by desorbing the absorption medium from the adsorbent and a regeneration gas stream (11) containing the absorption medium.
2. The method according to claim 1, wherein a physical absorption medium is provided in step (a), carbon dioxide is removed by physical absorption at an absorption pressure in step (b), and carbon dioxide is desorbed at a desorption pressure by at least one depressurization step in step (c), wherein the desorption pressure is lower than the absorption pressure.
3. The method according to claim 1, wherein a chemical absorption medium is provided in step (a), carbon dioxide is removed by chemical absorption at an absorption temperature in step (b), and carbon dioxide is desorbed at a regeneration temperature by at least one heating step in step (c), wherein the regeneration temperature is higher than the absorption temperature.
4. The method according to claim 1 or 2, wherein at least one flash step in a flash column is provided in step (c), and at least a part of the regeneration gas stream (11) containing the absorption medium is fed into the flash column.
5. The method according to any one of claims 1, 2 and 4, wherein a thermal regeneration step in a thermal regeneration column is provided downstream of step (c) in the flow direction of the absorption medium, and at least a part of the regeneration gas stream (11) containing the absorption medium is fed into the thermal regeneration column.
6. The method according to any one of the preceding claims, wherein the method comprises at least one distillation step in a distillation column for thermally removing water entrained in the synthesis gas from the absorption medium, and at least a part of the regeneration gas stream (11) containing the absorption medium is fed into the distillation column.
7. The method according to any one of the preceding claims, wherein the second sub-stream (14) of the carbon dioxide product stream (12) is heated to a desorption temperature of 75 °C to 225 °C, preferably 100 °C to 200 °C, more preferably 125 °C to 175 °C.
8. The method according to any one of the preceding claims, wherein the proportion of the volume flow rate of the second sub-stream (14) in the volume flow rate of the total stream (12) of the carbon dioxide product stream is in the range of 1% to 25%, preferably in the range of 5% to 20%, and more preferably in the range of 10% to 15%.
9. The method according to any one of the preceding claims, wherein the absorption medium is adsorbed on the adsorbent due to the molecular sieve effect of the adsorbent.
10. The method according to any one of the preceding claims, wherein the adsorbent is arranged in a fixed bed reactor.
11. The method according to claim 10, wherein the method comprises at least two fixed bed reactors, wherein i. During a first fixed time period, the adsorbent in the first fixed bed reactor is loaded, wherein a carbon dioxide product stream containing an absorption medium is passed therethrough, and the adsorbent in the second fixed bed reactor is regenerated, wherein a regeneration gas stream is passed therethrough, and ii. In a second fixed time period following the first time period, the adsorbent in the first fixed bed reactor is regenerated, wherein a regeneration gas stream is passed therethrough, and the adsorbent in the second fixed bed reactor is loaded, wherein the carbon dioxide product stream containing the absorption medium is passed therethrough.
12. The method according to any one of the preceding claims, wherein the absorption medium is desorbed from the adsorbent at a pressure lower than the adsorption pressure used in step d) for adsorbing the absorption medium on the adsorbent.
13. The method according to any one of the preceding claims, wherein the first sub-stream of the carbon dioxide product stream is liquefied by at least one cooling step and at least one condensation step.
14. The method according to any one of the preceding claims, wherein the adsorbent is also arranged to adsorb water.
15. The method according to any one of the preceding claims, wherein the method comprises a solid gasifier for gasifying a carbonaceous feedstock to produce syngas, and wherein at least a part of the regeneration gas stream (11) containing the absorption medium is fed into the solid gasifier.
16. A device for producing hydrogen from a syngas stream comprising at least hydrogen (H2) and carbon dioxide (CO2), having the following device components connected in fluid communication: (a) Means for providing an absorption medium; (b) Means for removing carbon dioxide from the syngas stream by absorption, whereby a carbon dioxide-loaded absorption medium and a hydrogen-containing product stream can be obtained; (c) Means for desorbing carbon dioxide from the loaded absorption medium, whereby a carbon dioxide-lean absorption medium and a carbon dioxide product stream containing the absorption medium can be obtained; (d) Means for removing the absorption medium from the carbon dioxide product stream containing the absorption medium, wherein the means comprises at least one fixed bed containing a solid adsorbent and removes the absorption medium from the carbon dioxide product stream containing the absorption medium by adsorbing the absorption medium on the solid adsorbent in the fixed bed, whereby a carbon dioxide product stream and an adsorbent loaded with the absorption medium can be obtained; (e) Means for discharging a first sub-stream of the carbon dioxide product stream from the method; (f) means for heating a second sub-stream of the carbon dioxide product stream to a desorption temperature, whereby a regeneration gas stream can be obtained, and means for passing the regeneration gas stream through the loaded adsorbent, so that an adsorbent regenerated by desorbing the absorption medium from the adsorbent and a regeneration gas stream containing the absorption medium can be obtained.