Process system for hydrogen production and co-production of biological natural gas from biological crude synthesis gas

Abstract

The invention relates to the technical field of organic solid waste treatment, in particular to a process system for hydrogen production and co-production of biological natural gas from biological crude synthesis gas, which comprises a purification unit, a hydrocarbon regulation unit, an acid removal unit, a methane upgrading unit, a hydrogen recycling and purifying unit and a methane recycling and purifying unit which are connected in sequence. The purification unit is used for removing impurities through pre-impurity removal, compression, dry-process impurity removal and wet-process desulfurization to produce purified synthesis gas and sulfur; the hydrocarbon adjusting unit is pressurized through a centrifugal compressor and adjusts the hydrogen-carbon ratio; the acid removal unit is used for removing acid gas and organic sulfur; the methane upgrading unit is used for converting CO / CO2 into methane through methanation reaction; and the recycling unit purifies hydrogen through pressure swing adsorption and recycles methane by using a membrane separation technology to produce biogas. The problems of low purity and insufficient raw material utilization rate of the traditional process are solved through the circulation process, the co-production of high-purity hydrogen and biogas is realized, and the additional value of resources is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of organic solid waste treatment, and particularly to a process system for producing hydrogen and associated biomethane from biocrude syngas. Background Art

[0002] In the current energy and environmental protection fields, biocrude syngas, a gas obtained by pyrolysis and gasification of municipal solid waste or biomass raw materials, mainly composed of hydrogen, methane, carbon monoxide, and carbon dioxide, is gradually attracting wide attention. The application of biocrude syngas in the industrial field is still in its infancy, and the industrialization path of hydrogen production from waste is still in the exploration stage. Currently, it is in the research and demonstration stage as a whole.

[0003] Most of the existing biocrude syngas treatment methods focus on combustion power generation and hydrogen production. However, this treatment mode has the problem of relatively low comprehensive utilization rate. Specifically, the high-value components such as methane in biocrude syngas are not fully utilized, and they are not completely extracted and converted into corresponding products.

[0004] Regarding the current deep processing and utilization of biocrude syngas, it is mainly to produce hydrogen with a purity of 99.9 - 99.99% using biocrude syngas as the raw material. For example, in the patent with the application number 202310529013.7 and the name "A Process for Producing Hydrogen by Carbonization and Gasification of Municipal Solid Waste", 99.9% hydrogen can be obtained after a series of processes such as shift conversion, decarbonization, desulfurization, and PSA for the biocrude syngas. However, this method has obvious defects. It only focuses on hydrogen production, does not fully utilize and recover the methane in the biocrude syngas, and the hydrogen in the PSA desorbed gas is not recovered either, resulting in a relatively large loss of hydrogen and an urgent need to improve the overall utilization rate.

[0005] Another example is the patent with the application number 202310485108.3 and the name "An Apparatus and Method for Producing Hydrogen from Municipal Solid Waste and / or Organic Matter". After a series of processes such as desulfurization, shift conversion, and hydrogen purification for the biocrude syngas, 99.99% hydrogen can be obtained. Although this method can produce high-purity hydrogen, it does not explain the hydrogen recovery rate and does not fully utilize and recover the methane in the biocrude syngas either, and the product route is relatively single. Summary of the Invention

[0006] The present invention provides a process system for producing hydrogen and associated biomethane from biocrude syngas. Through this process system, the problems of low hydrogen purity and low raw material utilization efficiency are solved, and the recovery rates of hydrogen and biomethane are improved.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides a process system for producing hydrogen by using bio - crude syngas and co - producing biomethane, which comprises a purification unit, a carbon - hydrogen regulation unit, an acid removal unit, a methane upgrading unit, a unit for recycling and purifying hydrogen, and a unit for recycling and purifying methane, which are connected in series step by step; wherein, the purification unit is used for pre - removing impurities, preliminarily compressing, further removing impurities and desulfurizing the bio - crude syngas entering the process system to obtain purified syngas and by - product sulfur; the carbon - hydrogen regulation unit is used for pressurizing the purified syngas and regulating the contents of hydrogen in the purified syngas and methane in the methane upgrading unit to obtain carbon - hydrogen regulated gas; the acid removal unit is used for removing acidic gases in the carbon - hydrogen regulated gas to obtain acid - removed gas and by - product CO2; the methane upgrading unit is used for carrying out methanation reaction on the acid - removed gas to convert CO and CO2 in the acid - removed gas into methane, and incrementally upgrading the methane in the purified syngas to obtain a mixed gas; the unit for recycling and purifying hydrogen is used for recycling the mixed gas and purifying hydrogen by using a pressure swing adsorption process to obtain product hydrogen and methane recycling gas; the unit for recycling and purifying methane comprises a screw compressor, a circulating membrane separation device and a reciprocating compressor, which are used for pressurizing and separating the methane recycling gas to obtain product biomethane, hydrogen and methane recycling gas, and the hydrogen and methane recycling gas are pressurized by the reciprocating compressor and then returned to the carbon - hydrogen regulation unit or enter the unit for recycling and purifying hydrogen, and the regeneration pressure of the pressure swing adsorption is controlled at 0.02 - 0.05 MPa.

[0008] Further, the purification unit comprises a pre - impurity removal device, a blower, a dry - impurity removal device and a wet desulfurization device which are connected in series step by step: the pre - impurity removal device is used for pre - removing macromolecular hydrocarbon compound impurities in the bio - crude syngas to obtain pre - impurity - removed gas, and the blower is used for preliminarily pressurizing the pre - impurity - removed gas to obtain preliminarily compressed gas; the dry - impurity removal device is used for further removing impurities such as macromolecular hydrocarbon compounds in the preliminarily compressed gas to obtain secondary - impurity - removed gas; the wet desulfurization device is used for removing inorganic sulfur in the secondary - impurity - removed gas to finally obtain purified syngas and by - product sulfur.

[0009] Further, the carbon - hydrogen regulation unit comprises a centrifugal compressor and a hydrogen upgrading device which are connected in series step by step; wherein, the centrifugal compressor is used for secondarily pressurizing the purified syngas to obtain secondarily compressed gas, and the hydrogen upgrading device is used for regulating the content of hydrogen in the secondarily compressed gas and the content of CO required by the methane upgrading unit as required; wherein, the hydrogen upgrading device comprises a detoxification furnace, a humidifier and a conversion furnace which are connected in sequence.

[0010] Further, the acid removal unit includes an acid removal device and a hydrodesulfurization unit connected step by step in sequence; the acid removal device is used to remove hydrogen sulfide, CO2, etc. in the hydrocarbon regulating gas to obtain a by-product CO2, and the hydrodesulfurization unit is used to carry out a hydrogenation reaction on organic sulfur, olefins, etc. in the hydrocarbon regulating gas with hydrogen to convert organic sulfur into inorganic sulfur to obtain acid-removed gas; wherein, the acid removal device includes an absorption tower, a flash tower, a stripping and regeneration tower, and a flash gas decarbonization tower.

[0011] Further, the methane upgrading unit adopts a methanation reactor, and the methanation reactor is used to convert CO and CO2 in the acid-removed gas into methane, and the reaction temperature is 250-450 °C.

[0012] Further, the hydrogen recycling and purification unit includes a raw material gas and a recycled tail gas mixing tank, a hydrogen purification adsorption tower group, and a recycled tail gas mixing tank connected in sequence, and is used to purify hydrogen to obtain product hydrogen and methane recycled gas.

[0013] Further, the process system for producing hydrogen and bio-natural gas by using the bio-crude syngas to produce hydrogen and co-producing bio-natural gas includes the following steps: S1: Pass the bio-crude syngas through a pre-removal device, a blower, a dry removal device, and a wet desulfurization device in sequence to remove macromolecular hydrocarbon compounds and inorganic sulfur impurities to obtain purified syngas and a by-product sulfur; S2: Secondarily pressurize the purified syngas to 1.5-2.5 MPa, and adjust the content of hydrogen and carbon monoxide in the gas through a shift reaction, and control the CO content at the shift outlet to be 0.8%-13.69% to obtain a hydrocarbon regulating gas; S3: Sequentially carry out acid gas removal and hydrodesulfurization on the hydrocarbon regulating gas to remove hydrogen sulfide, CO2, and organic sulfur to obtain acid-removed gas and a by-product CO2; S4: Pass the acid-removed gas into a methanation reactor, and carry out a methanation reaction at 250-450 °C and 1.5-2.0 MPa to convert CO and CO2 into methane to obtain a mixture of hydrogen and methane; S5: Adopt a pressure swing adsorption process to purify hydrogen from the mixture to obtain product hydrogen with a purity ≥99.999% and methane recycled gas rich in methane; S6: Pass the methane recycled gas through a screw compressor, a circulating membrane separation device, and a reciprocating compressor in sequence to separate and obtain product bio-natural gas and hydrogen and methane recycled gas; the hydrogen and methane recycled gas is pressurized to 1.5-2.5 MPa by a reciprocating compressor and then returned to step S2 for hydrocarbon regulation or enters step S5 after pressurization for hydrogen recycling and purification.

[0014] Further, in the step S5, 5A molecular sieve and activated carbon composite adsorbent are used for pressure swing adsorption.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention produces hydrogen with a purity of 99.999% through a purification unit, a hydrocarbon regulation unit, an acid removal unit, a methane upgrading unit, a hydrogen recycling, purification unit, and a methane recycling, purification unit that are connected in sequence. Among them, the purification unit removes macromolecules and impurities in the raw syngas through pre-impurity removal, dry impurity removal, and wet desulfurization to obtain pure syngas and by-product sulfur. The hydrocarbon regulation unit adjusts the composition of the gas as needed through a centrifugal compressor and a hydrogen upgrading process, effectively regulating the production of hydrogen and methane and improving the resource utilization rate. The acid removal unit removes hydrogen sulfide and carbon dioxide to obtain acid-removed gas without organic sulfur. The methane upgrading unit uses an adiabatic methanation process to convert CO and CO2 in the acid-removed gas into methane, improving the yield and quality of methane.

[0016] 2. The hydrogen recycling, purification unit of the present invention obtains high-purity hydrogen and regenerated tail gas rich in methane through a pressure swing adsorption process. The hydrogen recovery rate reaches 96.5%, and the methane recovery rate reaches 98.5%. The methane recycling, purification unit uses membrane separation technology and compressors to separate and purify hydrogen and methane from the regenerated tail gas and reintroduce these gases into the recycling process, further increasing the product yield and conversion rate. The effective components such as hydrogen, methane, and carbon monoxide in the biological raw syngas are fully utilized and recovered, increasing the product added value and reducing energy waste.

[0017] 3. The present invention solves the problems of low hydrogen purity and low raw material utilization efficiency, improves the deep processing and utilization value of biological raw syngas. All of the carbon monoxide, hydrogen, and methane in the biological raw syngas are recovered. Meanwhile, by-product sulfur and carbon dioxide with a purity greater than 98% (V%) are produced. After deep processing, each component in the gas is recovered and corresponding products are obtained, fully exploiting and maximizing the value of biological raw syngas. At the same time, the recovery rates of hydrogen and biomethane are increased, significantly improving the utilization rate of biological raw syngas. Finally, the co-production of high-purity hydrogen and high-value biomethane is realized, greatly improving the economic and environmental benefits of biological raw syngas. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic structural diagram of the process system for producing hydrogen and co-producing biomethane from biological raw syngas in an embodiment of the present invention.

[0019] Figure 2 is a schematic structural diagram of the hydrogen recycling, purification unit in an embodiment of the present invention.

[0020] Explanation of the reference numerals: 1. Purification unit; 2. Hydrocarbon adjustment unit; 3. Acid removal unit; 4. Methane upgrading unit; 5. Hydrogen recycling and purification unit; 6. Methane recycling and purification unit; 7. Pre-impurity removal device; 8. Blower; 9. Dry impurity removal device; 10. Wet desulfurization device; 11. Centrifugal compressor; 12. Hydrogen upgrading device; 13. Acid removal device; 14. Hydrogenation desulfurization device; 15. Screw compressor; 16. Circulating membrane separation device; 17. Reciprocating compressor. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0022] Example 1 like Figure 1 As shown, the present invention provides a process system for preparing high-purity hydrogen from bio-crude synthesis gas and co-producing bio-natural gas, comprising a purification unit 1, a carbon-hydrogen regulating unit 2, an acid removal unit 3, a methane upgrading unit 4, a circulating recovery and purification hydrogen unit 5 and a circulating recovery and purification methane unit 6 which are connected in sequence; wherein the purification unit 1 is used for pre-removing impurities, preliminarily compressing, further removing impurities and desulfurizing the bio-crude synthesis gas entering the process system to obtain purified synthesis gas and by-product sulfur; the carbon-hydrogen regulating unit 2 is used for pressurizing the purified synthesis gas, and adjusting the content of hydrogen in the purified synthesis gas and the content of methane in the methane upgrading unit 4 according to the demand for product high-purity hydrogen and bio-natural gas to obtain carbon-hydrogen regulated gas; the acid removal unit 3 is used for removing acid gases such as hydrogen sulfide and carbon dioxide in the gas after carbon-hydrogen regulation, and hydrogenating and removing organic sulfur. The acid degassing unit 4 is used for methanating the acid degassing, converting CO and CO2 in the acid degassing into methane, and performing incremental upgrading on the methane in the purified synthesis gas to obtain a mixed gas; the circulating recovery and purification hydrogen unit 5 is used for circulating recovery and purifying hydrogen on the mixed gas after the methanation reaction, to obtain product hydrogen and methane circulating recovery gas with a purity of 99.999%; the circulating recovery and purification methane unit 6 is used for compressing the methane circulating recovery gas and separating methane, obtaining biogas (type II) from the product gas, and obtaining product biogas and hydrogen and methane circulating recovery gas from the tail gas, and the hydrogen and methane circulating recovery gas can be returned to the carbon-hydrogen regulating unit 2 for recovery or pressurized by the reciprocating compressor 17 and then enter the circulating recovery and purification hydrogen unit 5 for recovery.

[0023] The purification unit 1 includes a pre-impurity removal device 7, a blower 8, a dry impurity removal device 9, and a wet desulfurization device 10 that are connected step by step in sequence: The pre-impurity removal device 7 is used to pre-remove macromolecular hydrocarbon compound impurities in the crude biogas to obtain pre-removed gas, and the blower 8 is used to preliminarily pressurize the pre-removed gas to obtain preliminarily compressed gas; the dry impurity removal device 9 is used to further remove impurities such as macromolecular hydrocarbon compounds in the preliminarily compressed gas to obtain secondary-removed gas; the wet desulfurization device 10 is used to remove inorganic sulfur in the secondary-removed gas to finally obtain purified syngas and by-product sulfur. Among them, the dry impurity removal device 9 is temperature swing adsorption and can be set in series from 1 to 3 sections, and the wet desulfurization device 10 uses the wet oxidation-reduction method to convert hydrogen sulfide in the removed gas into elemental sulfur to obtain by-product sulfur.

[0024] The carbon-hydrogen regulation unit 2 includes a centrifugal compressor 11 and a hydrogen upgrading device 12 that are connected step by step in sequence; among them, the centrifugal compressor 11 is used to perform secondary pressurization on the purified syngas to obtain secondary compressed gas, and the hydrogen upgrading device 12 is used to adjust the content of hydrogen in the secondary compressed gas and the CO content required by the methane upgrading unit 4 as needed; among them, the hydrogen upgrading device 12 includes main equipment such as a detoxification furnace, a humidifier, a first-stage conversion furnace, and a second-stage conversion furnace. This step realizes for the first time the effective regulation of the production between hydrogen and methane by adjusting the CO content at the conversion outlet.

[0025] The acid removal unit 3 includes an acid removal device 13 and a hydrofining desulfurization device 14 that are connected step by step in sequence; the acid removal device 13 is used to remove acidic gases such as hydrogen sulfide and CO2 in the carbon-hydrogen regulation gas to obtain by-product CO2, and the hydrofining desulfurization device 14 is used to perform a hydrogenation reaction on organic sulfur, olefins, etc. in the carbon-hydrogen regulation gas to convert organic sulfur into inorganic sulfur to obtain acid-removed gas; among them, the acid removal device 13 includes main equipment such as an absorption tower, a flash tower, a stripping and regeneration tower, and a flash gas decarburization tower, and obtains CO2 with a by-product volume percentage ≥ 98%.

[0026] The methane upgrading unit 4 uses a methanation reactor, and the methanation reactor is used to perform an adiabatic methane conversion reaction on CO and CO2 in the acid-removed gas to convert them into methane, and the reaction temperature is 250 - 350 °C. The methane upgrading unit 4 increases and upgrades the methane in the purified syngas to improve the production and quality of biomethane. This step uses the methanation reaction for the first time in the deep processing process of biogas to realize the increase and upgrade of methane.

[0027] As Figure 2As shown in the figure, the hydrogen recycling and purification unit 5 includes a raw material gas and recycled tail gas mixing tank, a hydrogen purification adsorption tower group, and a recycled tail gas mixing tank connected in sequence. The hydrogen recycling and purification unit 5 purifies hydrogen from the gas after methane upgrading, mainly obtaining high-purity hydrogen with a purity of 99.999% and recycled tail gas that can be used for methane recycling through pressure swing adsorption process. Usually, 6 - 10 adsorption towers are required according to the hydrogen production amount and recovery rate requirements, and both vacuum pumping and flushing regeneration methods can be used. To obtain high-purity hydrogen with a purity of 99.999%, the total content of methane and nitrogen in the product hydrogen needs to be less than 10 -6 (volume percentage). Since the removal precision of methane and nitrogen is high, a composite adsorbent combination bed layer mainly composed of 5A molecular sieve and supplemented by activated carbon is required. To improve the utilization efficiency of the adsorbent, the regeneration pressure is preferably controlled at 0.03 MPa. This step realizes for the first time the production of product hydrogen by pressure swing adsorption and the obtaining of recycled methane gas, the raw material for producing biomethane, through the desorbed gas, recycling hydrogen and methane in the effective components of the biogas synthesis gas, and ensuring that there is no loss of hydrogen and methane in this unit, which is one of the important features of this process system.

[0028] The methane recycling and purification unit 6 includes a screw compressor 15, a recycle membrane separation device 16, and a reciprocating compressor 17 connected in sequence step by step; the screw compressor 15 is used to pressurize the recycled methane gas, the recycle membrane separation device 16 is used to separate hydrogen and methane to obtain product biomethane, hydrogen, and recycled methane gas, and the reciprocating compressor 17 is used to pressurize the hydrogen and recycled methane gas. Among them, product biomethane is obtained from the non-permeate gas side of the membrane. The permeate gas rich in hydrogen and methane is pressurized by the reciprocating compressor 17 and then returned to the inlet of the hydrogen recycling and purification unit 5 to recover the hydrogen in the permeate gas. The remaining methane in the permeate gas is compressed by the screw compressor 15 and then enters the recycle membrane separation device 16 again. In this way, the recycled tail gas (i.e., recycled methane gas) generated by the hydrogen recycling and purification unit 5 and the permeate gas (i.e., hydrogen and recycled methane gas) generated by the recycle membrane separation are recycled in the system to increase the production of high-purity hydrogen and biomethane. This step realizes for the first time the recycling of hydrogen and methane in the membrane separation tail gas to increase the production of product hydrogen and biomethane, which is one of the important features of this process system.

[0029] Taking the dry basis conditions of the following raw material bio-syngas as an example, the dry basis conditions of the raw material bio-syngas are shown in Table 1: Table 1 Dry basis conditions of raw material bio-syngas Among them, C in the biogas 6+ contains 200 mg / Nm 3 、total sulfur content of biogas is 5 g / Nm3 .

[0030] Based on the above raw material bio - syngas conditions, in this embodiment, the carbon - hydrogen regulation unit controls to maximize the conversion of CO into hydrogen to obtain the maximum hydrogen production and by - produce bio - natural gas, achieving an annual output of 16,200 tons of 99.999% high - purity hydrogen and 46,000 tons of bio - natural gas.

[0031] The above raw material bio - syngas is purified by using the process system for producing hydrogen and co - producing bio - natural gas from bio - syngas of this embodiment. The specific steps are as follows: The purification unit 1 includes a pre - impurity removal device 7, a blower 8, a dry - method impurity removal device 9, and a wet - method desulfurization device 10. Among them, the pre - impurity removal device 7, the blower 8, the dry - method impurity removal device 9, and the wet - method desulfurization device 10 are connected in sequence. The raw syngas is preliminarily removed of macromolecular hydrocarbon compounds to ≤20mg / Nm 3 by the pre - impurity removal device 7, and then initially pressurized to 40kpa.G by the blower 8 and then enters the temperature - swing adsorption dry - method impurity removal device 9 to remove macromolecular hydrocarbon compounds in the raw syngas to ≤5mg / Nm 3 . Finally, it enters the wet - method desulfurization device 10. The bio - syngas enters from the lower part of the packed desulfurization tower. After the gas is in reverse contact with the PDS desulfurization liquid sprayed from the top of the packing tower, the H2S in it is removed to ≤50mg / Nm 3 , obtaining purified syngas and by - product sulfur.

[0032] The pre - impurity removal device 7 and the blower 8 can be single - unit or multi - unit in parallel combination. The dry - method impurity removal device 9 can adopt one - stage to multi - stage series temperature - swing adsorption to remove impurities such as macromolecular hydrocarbon compounds. In this embodiment, according to the amount of raw syngas, the pre - impurity removal device 7 is one unit, and the blower is two units (one in operation and one in standby). The main equipment for wet - method desulfurization includes: desulfurization tower, regeneration tank, foam storage tank, sulfur melting kettle, etc.

[0033] The hydrocarbon regulation unit 2 includes a centrifugal compressor 11 for secondary pressurization of the purified syngas, and a hydrogen upgrading device 12 for adjusting the hydrogen content in the purified syngas and the CO content required by the subsequent methane upgrading unit 4 as needed. Among them, the centrifugal compressor 11 and the hydrogen upgrading device 12 are connected in sequence. Further, the purified syngas is pressurized in the centrifugal compressor according to the specific application environment of the subsequent process section. In this embodiment, the purified syngas enters the centrifugal compressor and is pressurized to 2.0 MPa. In this embodiment, the purified syngas after the purification unit is relatively clean. Therefore, a centrifugal compressor is selected to pressurize the purified syngas, and there is at least 1 centrifugal compressor. Further, the purified syngas pressurized by the centrifugal compressor during hydrogen upgrading does not need to be cooled by a cooler, and directly enters the raw material gas preheater and is preheated to above 230 °C after multi-step heating, and then enters the deoxidizer for deoxidation and purification. Subsequently, it enters the No. 1 controllable heat transfer shift furnace for the shift reaction, and uses the water heat transfer tube bundle buried in the catalyst bed to by-product 2.3 Mpa.G saturated steam. At the same time, the outlet temperature of the No. 1 controllable heat transfer shift furnace is controlled at about 270 °C by using the pressure of the by-product steam. Subsequently, the gas exits the No. 1 controllable heat transfer shift furnace and goes to the raw material gas preheater to heat the purified syngas, and then enters the No. 2 controllable heat transfer shift furnace for the shift reaction, and uses the water heat transfer tube bundle buried in the catalyst bed to by-product 1.0 Mpa.G saturated steam. At the same time, the outlet temperature of the shift furnace is controlled at about 195 °C by using the pressure of the by-product steam. The shifted gas exiting the controllable heat transfer shift furnace enters the raw material gas preheater to heat the purified syngas, and then enters the shifted gas cooling separator to further cool the gas to about 40 °C. Finally, the shifted gas is sent to the acid removal unit 3.

[0034] In this embodiment, two-stage isothermal conversion is adopted, and the raw material gas is brought to the conversion reaction temperature by using the compression heat and reaction heat, which can ensure a low final outlet temperature, a high CO conversion rate, less total steam consumption, and at the same time, the reaction heat and latent heat by-product 2.3 MPa steam and 1.0 MPa steam. To achieve the maximum hydrogen production, the CO content in the unit outlet gas is controlled at ≤0.8%, and the other components and contents are H2: 51.10%, N2: 1.44%, CH4: 13.66%, CO2: 32.62%, H2O: 0.38%.

[0035] The acid removal unit 3 includes an acid removal device 13 and a hydrodesulfurization device 14. Among them, the acid removal device 13 and the hydrodesulfurization device 14 are connected in sequence. Further, the gas from the hydrocarbon regulation unit 2 is first passed through a desulfurization device to remove H2S in the gas to ≤10 mg / Nm 3, and then enter the wet decarbonization process. The gas enters the lower part of the absorption tower after passing through the raw material gas-liquid separator. The gas is first washed with semi-lean liquid in the lower section of the absorption tower, and part of H2S and CO2 are absorbed. Then it is washed with regenerated lean liquid in the upper section of the absorption tower to remove CO2 in the purified gas to less than 0.1%, and then enters the hydrodesulfurization unit 14. Among them, the adsorbed CO2 is obtained as a by-product CO2 with a purity of 98% through subsequent treatment, which can be used for synthesizing urea and producing industrial-grade or food-grade CO2. Further, the decarbonized gas is heated to about 220 - 250 °C through a gas-gas heat exchanger and a steam heater, enters the first-stage hydrogenation reactor, and the organic sulfur reacts with hydrogen under the action of a cobalt-molybdenum hydrogenation catalyst to convert the organic sulfur into inorganic sulfur. After hydrogenation conversion, a zinc oxide desulfurizer is used to remove the total sulfur content in the shifted gas to less than 0.1 ppm, and then it enters the methane upgrading unit 4.

[0036] In this embodiment, the gas for the hydrogenation reaction is relatively clean and the content of organic sulfur is low. Only one-stage hydrogenation is required. The fine desulfurization tower adopts two towers, which can be in parallel or in series. If necessary, it can also be set as one-stage hydrogenation in series with two-stage hydrogenation.

[0037] The methane upgrading unit 4 includes a methanation reactor, a cooler and a gas-liquid separator. The acid gas removal gas from the hydrodesulfurization unit 14 enters the methanation reactor, and under the action of the catalyst, the reaction of converting CO and CO2 into methane occurs. The methane upgrading outlet gas exchanges heat with the decarbonized gas of the acid removal device to preheat the temperature of the decarbonized gas entering the hydrogenation reactor, and then is cooled to below 40 °C through a cooler and enters the unit 5 for recycling, recovering and purifying hydrogen. In this embodiment, an adiabatic methanation process flow is adopted. The methanation reaction temperature is 250 - 350 °C, and the reaction pressure is 1.75 Mpa.G. The methane content in the gas at the outlet of the methane upgrading unit is about 22.31%, and the hydrogen content is about 75.05%.

[0038] The hydrogen recycling and purification unit 5 includes a raw gas and recycled tail gas mixing tank, a hydrogen purification adsorption tower group, and a recycled tail gas mixing tank, which are connected in sequence. The PSA adopts an 8-tower flushing process, including processes such as adsorption, equal pressure reduction, co-current discharge, counter-current discharge, flushing, equal pressure boosting, and final boosting. Further, the hydrogen-rich gas after methane upgrading has a pressure of about 1.7 Mpa.G. After mixing with the hydrogen and methane recycle gas from the methane recycling and purification unit 6 in the raw gas and recycled tail gas mixing tank, it enters the adsorption tower in the adsorption state from the bottom of the tower. Under the sequential selective adsorption of various adsorbents, the impurities therein are adsorbed, and the unadsorbed hydrogen flows out from the top of the tower as a product, obtaining high-purity hydrogen with a purity greater than 99.999% (CO ≤ 0.2 ppm, CO2 ≤ 2 ppm) and a pressure greater than 1.6 Mpa.G, meeting the hydrogen requirements for fuel cell vehicles. The regenerated tail gas rich in methane (the pressure of the regeneration and re-generation gas is 0.05 - 0.02 MPa) obtained through regeneration steps such as counter-current discharge and flushing is mixed and buffered in the recycled tail gas mixing tank and then sent to the methane recycling and purification unit 6.

[0039] In this example, the composition of the raw gas entering this unit is (H2: 76.24%, N2: 2.22%, CH4: 21.54%). The product hydrogen is high-purity hydrogen of 99.999% (CO ≤ 0.2 ppm, CO2 ≤ 2 ppm) and meets the hydrogen requirements for fuel cell vehicles. A combined adsorption bed layer of activated alumina, silica gel, activated carbon, and 5A molecular sieve is required.

[0040] The methane recycling and purification unit 6 includes a screw compressor 15, a recycle membrane separation device 16, and a reciprocating compressor 17. Among them, the screw compressor 15, the recycle membrane separation device 16, and the reciprocating compressor 17 are connected in sequence. Further, the regenerated tail gas from the hydrogen recycling and purification unit 5 is pressurized to 1.1 Mpa.G by the screw compressor 15 and then enters the recycle membrane separation device 16. First, it is filtered, and then heated to 50 °C and then subjected to recycle membrane separation. Here, H2 and CH4 are separated and purified. The product biomethane with a pressure of 1.0 Mpa.G is obtained on the membrane retentate side, and its CH4 content ≥ 85% vol and H2 content is about 5%. The concentration of H2 on the membrane permeate side can be increased from 36% to more than 79%.

[0041] The hydrogen content in the permeate gas is 79.8% and the methane content is 16.62%, which can be recycled and utilized. The membrane permeate gas rich in hydrogen and methane is pressurized to 1.75 Mpa.G by the reciprocating compressor 17 and then returned to the inlet of the hydrogen recycling and purification unit 5 to recycle hydrogen and methane to increase the production of high-purity hydrogen and biomethane products.

[0042] In this example, the hydrogen recovery rate reaches 96.5% and the methane recovery rate reaches 98.5%, both higher than the recovery rates of existing processes.

[0043] Example 2 Based on the conditions of the raw material bio - syngas mentioned above, different from Example 1, in this example, the CO conversion rate is adjusted in the carbon - hydrogen regulation unit to achieve the optimal ratio of CO and H2 content, and all CO is converted into methane in the methane upgrading unit to increase the production and quality of methane. Through the control of the carbon - hydrogen regulation unit and the methane upgrading unit, the maximum bio - natural gas production is obtained and hydrogen is by - produced, reaching an annual output of 0.11×10^4 tons of 99.999% high - purity hydrogen and 7.7×10^4 tons of bio - natural gas.

[0044] Specifically, the purification unit 1 in this example is the same as that in Example 1. The macromolecular hydrocarbon compounds in the raw syngas are removed to ≤5mg / Nm 3 , and H2S is removed to ≤50mg / Nm 3 , obtaining purified syngas and by - product sulfur.

[0045] In this example, for the carbon - hydrogen regulation unit 2, in order to achieve the maximum bio - natural gas production, the CO content in the outlet gas of the unit is controlled at about 13.69% by adjusting the water - make - up ratio. The other components and their contents are H2: 44.91%, N2: 1.62%, CH4: 15.42%, CO2: 24.05%, H2O: 0.29%.

[0046] The acid removal unit 3 in this example is the same as that in Example 1. The total sulfur content in the shifted gas is removed to less than 0.1ppm by using zinc oxide desulfurizer. The removed CO2 is further processed to obtain by - product CO2 with a purity of 98%, which can be used for synthesizing urea and producing industrial - grade or food - grade CO2.

[0047] In this example, for the methane upgrading unit 4, an adiabatic methanation process is adopted. The methanation reaction temperature is 250 - 450°C, the reaction pressure is 1.75Mpa.G. The methane content in the outlet gas of the methane upgrading unit is about 83.90%, and the hydrogen content is about 11.04%.

[0048] The hydrogen recycling and purification unit 5 adopts a 7 - tower flushing PSA process. Further, the methane - rich gas after methane upgrading has a pressure of about 1.7 Mpa.G. After being mixed with hydrogen and methane recycle gas from the methane recycling and purification unit 6 in the raw gas buffer tank, it enters the adsorption tower that is in the adsorption state from the bottom of the tower. Under the sequential selective adsorption of various adsorbents, non - hydrogen gases such as methane and nitrogen are adsorbed, and the unadsorbed hydrogen flows out from the top of the tower as a product, obtaining high - purity hydrogen with a purity greater than 99.999% (CO ≤ 0.2 ppm, CO2 ≤ 2 ppm) and a pressure greater than 1.6 Mpa.G, meeting the hydrogen requirements for fuel cell vehicles. The regenerated tail gas rich in methane (the pressure of the regeneration and regeneration gas is 0.05 - 0.02 MPa) obtained through regeneration steps such as reverse release and flushing goes to the methane recycling and purification unit 6.

[0049] In this example, the composition of the raw gas entering this unit is (H2: 13.84%, N2: 4.71%, CH4: 81.08%). The product hydrogen is high - purity hydrogen with 99.999% (CO ≤ 0.2 ppm, CO2 ≤ 2 ppm), meeting the hydrogen requirements for fuel cell vehicles. A combined adsorption bed layer of activated alumina, silica gel, activated carbon, and 5A molecular sieve is adopted, with activated carbon as the main component.

[0050] The regenerated tail gas from the hydrogen recycling and purification unit 5 is pressurized to 1.1 Mpa.G by the screw compressor 15 and then enters the circulating membrane separation device 16. First, it is filtered, then heated to 50 °C and subjected to circulating membrane separation. Here, H2 and CH4 are separated and purified. The product biomethane with a pressure of 1.0 Mpa.G and a CH4 content ≥ 94.27% is obtained on the membrane retentate side. The concentration of H2 on the membrane permeate side can be increased from 5.32% to more than 28.61%. The hydrogen content in the permeate gas is 28.61% and the methane content is 64.37%, which can be recycled. The membrane permeate gas rich in hydrogen and methane is pressurized to 1.75 Mpa.G by the reciprocating compressor 17 and then returned to the inlet of the hydrogen recycling and purification unit 5 to recycle hydrogen and methane, so as to increase the output of high - purity hydrogen and biomethane products. This step is an important feature of this process system.

[0051] In this embodiment, the gas volume of the membrane permeate gas rich in hydrogen and methane is half of that in Example 1. The membrane permeate gas rich in hydrogen and methane can also be recycled after being pressurized by the centrifugal compressor 11.

[0052] The beneficial effects of the present invention are as follows: Biological crude syngas is a new green and environment-friendly hydrogen production raw material. The hydrogen produced by this process has a purity of 99.999%. The hydrogen purity and impurity content can simultaneously meet the technical requirements of high-purity hydrogen in Part 2 of Hydrogen - GBT 3634.2 - 2011 and the technical requirements of fuel hydrogen for proton exchange membrane fuel cell vehicles - GB / T 37244 - 2018. The quality and value of hydrogen are higher.

[0053] Biological crude syngas produces biomethane through the associated production of this process system, and its quality meets the technical requirements of Class II biomethane in Biomethane - GB / T41328 - 2022. The effective components such as hydrogen, methane, and carbon monoxide in biological crude syngas are fully utilized and recovered, improving the added value of products and reducing energy waste.

[0054] The regenerated tail gas generated by the hydrogen recycling and purification unit is sent to the methane recycling and purification unit. The permeate gas rich in hydrogen and methane on the permeation side of the recycle membrane separation returns to the inlet of the hydrogen recycling and purification unit 5. In the whole process, the tail gas rich in hydrogen and methane except for the products is recycled and reused. When the purity of the product hydrogen is 99.999% and the quality of methane meets that of Class II biomethane, the hydrogen recovery rate reaches 96.5% and the methane recovery rate reaches 98.5%. The above recovery rates are higher than those of the existing processes. The yields of hydrogen and biomethane are higher, and the effective utilization rate of biological crude syngas is also higher.

[0055] The yields of high-purity hydrogen and biomethane can be adjusted according to the market situation. When the market price of high-purity hydrogen is high, all the carbon monoxide in the crude syngas can be converted into hydrogen in the hydrogen upgrading section of the carbon-hydrogen regulation section to increase the hydrogen yield. When the market price of high-purity hydrogen is low, a small part of the carbon monoxide in the crude syngas can be converted into hydrogen in the carbon-hydrogen regulation section, and most of the remaining carbon monoxide is converted into methane through the methane upgrading section to increase the biomethane yield. The yields of high-purity hydrogen and biomethane can be adjusted according to the market price situation, enhancing the enterprise's anti-risk ability and being more conducive to realizing the industrialization of the utilization of biological crude syngas.

[0056] The value of the deep processing and utilization of biological crude syngas is improved. All the carbon monoxide, hydrogen, and methane in biological crude syngas are recovered. Meanwhile, sulfur and carbon dioxide with a purity greater than 98% (V%) are by-produced. All the components in the gas are recovered after deep processing and corresponding products are obtained, fully exploring and maximizing the value of biological crude syngas.

[0057] In summary, through the cooperation of multiple units and recycling, the present invention first realizes the deep treatment of the raw gas and the regeneration of hydrogen and methane through steps such as purification, hydrocarbon regulation, acid removal, and methane upgrading. Furthermore, high-purity hydrogen is extracted through a purification process and recycled to increase hydrogen production. Still further, biomethane is purified through a circulating membrane separation technology and the output of biomethane is increased through compressor recycling.

[0058] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, may make some changes or modifications to equivalent embodiments by using the disclosed technical content, but any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A process system for hydrogen production and biogas co-production from biological crude synthesis gas, characterized in that, It includes a purification unit (1), a hydrocarbon regulation unit (2), an acid removal unit (3), a methane upgrading unit (4), a unit (5) for recycling, purifying hydrogen, and a unit (6) for recycling, purifying methane, which are connected step by step in sequence; Among them, the purification unit (1) is used for pre - removing impurities, preliminarily compressing, further removing impurities and desulfurizing the biological crude syngas entering the process system to obtain purified syngas and by - product sulfur; the hydrocarbon regulation unit (2) is used for pressurizing the purified syngas and regulating the content of hydrogen in the purified syngas and methane in the methane upgrading unit (4) to obtain hydrocarbon - regulated gas; the acid removal unit (3) is used for removing acidic gases in the hydrocarbon - regulated gas to obtain acid - removed gas and by - product CO2; the methane upgrading unit (4) is used for carrying out methanation reaction on the acid - removed gas to convert CO and CO2 in the acid - removed gas into methane and incrementally upgrading the methane in the purified syngas to obtain a mixed gas; the unit (5) for recycling, purifying hydrogen is used for recycling the mixed gas and purifying hydrogen by pressure swing adsorption process to obtain product hydrogen and methane recycle gas; the unit (6) for recycling, purifying methane includes a screw compressor (15), a recycle membrane separation device (16) and a reciprocating compressor (17), which are used for pressurizing and separating the methane recycle gas to obtain product biomethane, hydrogen and methane recycle gas. The hydrogen and methane recycle gas are pressurized by the reciprocating compressor (17) and then returned to the hydrocarbon regulation unit (2) or enter the unit (5) for recycling, purifying hydrogen, and the pressure swing adsorption regeneration pressure is controlled at 0.02 - 0.05 MPa.

2. The process system for producing hydrogen by biological crude syngas and co-producing biomethane according to claim 1, wherein The purification unit (1) includes a pre - impurity removal device (7), a blower (8), a dry impurity removal device (9) and a wet desulfurization device (10) that are connected step by step in sequence: the pre - impurity removal device (7) is used for pre - removing macromolecular hydrocarbon compound impurities in the biological crude syngas to obtain pre - impurity - removed gas, the blower (8) is used for preliminarily pressurizing the pre - impurity - removed gas to obtain preliminarily compressed gas; the dry impurity removal device (9) is used for further removing macromolecular hydrocarbon compounds in the preliminarily compressed gas to obtain secondary - impurity - removed gas; the wet desulfurization device (10) is used for removing inorganic sulfur in the secondary - impurity - removed gas to finally obtain purified syngas and by - product sulfur.

3. The process system for producing hydrogen by biological crude syngas and co-producing biomethane according to claim 1, characterized in that, The hydrocarbon regulation unit (2) includes a centrifugal compressor (11) and a hydrogen upgrading device (12) that are connected step by step in sequence; among them, the centrifugal compressor (11) is used for secondarily pressurizing the purified syngas to obtain secondarily compressed gas, and the hydrogen upgrading device (12) is used for adjusting the content of hydrogen in the secondarily compressed gas and the content of CO required by the methane upgrading unit (4) as needed; among them, the hydrogen upgrading device (12) includes a detoxification furnace, a humidifier and a conversion furnace connected in sequence.

4. The process system for producing hydrogen by biological crude syngas and co-producing biomethane according to claim 1, characterized in that, The acid removal unit (3) includes an acid removal device (13) and a hydrofining desulfurization device (14) connected in series step by step; the acid removal device (13) is used to remove hydrogen sulfide and CO2 from the hydrocarbon regulating gas to obtain a by-product CO2, and the hydrofining desulfurization device (14) is used to carry out a hydrogenation reaction on the organic sulfur and olefins in the hydrocarbon regulating gas with hydrogen to convert the organic sulfur into inorganic sulfur, obtaining acid removal gas; wherein, the acid removal device (13) includes an absorption tower, a flash tower, a stripping and regeneration tower, and a flash gas decarbonization tower.

5. The process system for hydrogen production by biological crude syngas and coproduction of biomethane according to claim 1, characterized in that, The methane upgrading unit (4) adopts a methanation reactor, and the methanation reactor is used to convert CO and CO2 in the acid removal gas into methane, and the reaction temperature is 250 - 450 °C.

6. The process system for hydrogen production by biological crude syngas and co-production of biomethane according to claim 1, characterized in that, The hydrogen recycling and purification unit (5) includes a raw material gas and recycled tail gas mixing tank, a hydrogen purification adsorption tower group, and a recycled tail gas mixing tank connected in sequence, and is used to purify hydrogen to obtain product hydrogen and methane recycled gas.

7. The process system for hydrogen production and associated production of biomethane from crude biogas synthesis gas according to any one of claims 1-6, characterized in that, Using the process system for hydrogen production and biogas co-production from biological crude syngas to produce hydrogen and biogas co-production, includes the following steps: S1: Pass the biological crude syngas through a pre-removal device (7), a blower (8), a dry removal device (9), and a wet desulfurization device (10) in sequence to remove macromolecular hydrocarbon compounds and inorganic sulfur impurities, obtaining purified syngas and a by-product sulfur. S2: Perform secondary pressurization on the purified syngas to 1.5 - 2.5 MPa, and adjust the content of hydrogen and carbon monoxide in the gas through a shift reaction, controlling the CO content at the shift outlet to be 0.8% - 13.69% to obtain a hydrocarbon regulating gas. S3: Perform acid gas removal and hydrofining desulfurization on the hydrocarbon regulating gas in sequence to remove hydrogen sulfide, CO2, and organic sulfur, obtaining acid removal gas and a by-product CO2. S4: Pass the acid removal gas into a methanation reactor, and carry out a methanation reaction at 250 - 450 °C and 1.5 - 2.0 MPa to convert CO and CO2 into methane, obtaining a mixture of hydrogen and methane. S5: Adopt a pressure swing adsorption process to purify hydrogen from the mixture to obtain product hydrogen with a purity ≥ 99.999% and methane recycled gas rich in methane. S6: Pass the methane recycled gas through a screw compressor (15), a recycle membrane separation device (16), and a reciprocating compressor (17) in sequence to separate product biogas and hydrogen and methane recycled gas; the hydrogen and methane recycled gas is pressurized to 1.5 - 2.5 MPa by the reciprocating compressor (17) and then returned to step S2 for hydrocarbon regulation or enters step S5 after pressurization for hydrogen recycling and purification.

8. The process system for producing hydrogen from biological crude syngas and co-producing biomethane according to claim 7, characterized in that, In the step S5, 5A molecular sieve and activated carbon composite adsorbent are used for pressure swing adsorption.

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