A process system for hydrogen production and co-production of bio-natural gas from biological crude synthesis gas

Abstract

This utility model relates to the field of organic solid waste treatment technology, and in particular to a process system for the co-production of hydrogen from biogas crude syngas and biogas, comprising a purification unit, a hydrocarbon regulation unit, an acid removal unit, a methane upgrading unit, a hydrogen recycling and purification unit, and a methane recycling and purification unit connected in sequence. The purification unit removes impurities through pre-removal, compression, dry removal, and wet desulfurization, producing purified syngas and sulfur; the hydrocarbon regulation unit pressurizes and adjusts the hydrogen-to-carbon ratio using a centrifugal compressor; the acid removal unit removes acidic gases and organic sulfur; the methane upgrading unit converts CO / CO2 into methane through a methanation reaction; and the recycling unit purifies hydrogen through pressure swing adsorption and recovers methane using membrane separation technology, producing biogas. This utility model solves the problems of low purity and insufficient raw material utilization in traditional processes through a recycling process, achieving the co-production of high-purity hydrogen and biogas, and increasing the added value of resources.

Description

Technical Field

[0001] This utility model relates to the field of organic solid waste treatment technology, and in particular to a process system for producing hydrogen from biogas crude syngas and co-producing biogas. Background Technology

[0002] In the current energy and environmental protection field, biogas, a gas obtained from the pyrolysis and gasification of municipal solid waste or biomass raw materials, is gradually attracting widespread attention. Its main components include hydrogen, methane, carbon monoxide, and carbon dioxide. However, the industrial application of biogas is still in its early stages, and the industrialization of waste-to-hydrogen production is still in the exploratory phase, currently largely in the research and demonstration stage.

[0003] Existing methods for treating biogas crude are mostly focused on combustion-based power generation and hydrogen production. However, this approach suffers from relatively low overall utilization rates. Specifically, high-value-added components such as methane in the biogas crude are not fully utilized or completely extracted and converted into corresponding products.

[0004] Currently, the deep processing and utilization of biogas crude gas mainly involves using it as a raw material to produce hydrogen with a purity of 99.9%-99.99%. For example, patent application number 202310529013.7, entitled "A Process for Hydrogen Production from Municipal Solid Waste Carbonization Gasification," describes a process where biogas crude gas undergoes a series of steps including conversion, decarbonization and desulfurization, and PSA (Power Separation and Desorption), yielding 99.9% hydrogen. However, this method has significant drawbacks. It focuses solely on hydrogen production, failing to fully utilize and recover methane from the crude syngas, and also neglecting to recover hydrogen from the PSA desorbed gas, resulting in substantial hydrogen loss and an urgent need to improve overall utilization efficiency.

[0005] For example, patent application number 202310485108.3, entitled "An apparatus and method for producing hydrogen from municipal solid waste and / or organic matter," describes a method that produces 99.99% pure hydrogen from crude biosynthetic gas after a series of processes including desulfurization, conversion, and hydrogen purification. While this method can produce high-purity hydrogen, it does not specify the hydrogen recovery rate, nor does it fully utilize and recover the methane in the crude biosynthetic gas, resulting in a relatively limited product pipeline. Utility Model Content

[0006] This invention provides a process system for producing hydrogen from biogas crude syngas and co-producing biogas. This process system solves the problems of low hydrogen purity and low raw material utilization efficiency, and improves the recovery rate of hydrogen and biogas.

[0007] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0008] This invention provides a process system for producing hydrogen from biogas crude syngas and co-producing biogas, comprising a purification unit, a hydrocarbon conditioning unit, an acid removal unit, a methane upgrading unit, a hydrogen recycling and purification unit, and a methane recycling and purification unit connected in sequence. The purification unit is used to pre-remove impurities, perform preliminary compression, further impurity removal, and desulfurization on the biogas crude syngas entering the process system, obtaining purified syngas and sulfur as a byproduct. The hydrocarbon conditioning unit is used to pressurize the purified syngas and adjust the hydrogen content in the purified syngas and the methane content in the methane upgrading unit, obtaining a hydrocarbon conditioning gas. The acid removal unit is used to remove acidic gases from the hydrocarbon conditioning gas. The process involves several steps: first, acid degassing and CO2 as a byproduct are obtained; second, a methane upgrading unit is used to perform a methanation reaction on the acid degassing, converting CO and CO2 in the acid degassing into methane, and incrementally upgrading the methane in the purified synthesis gas to obtain a mixed gas; third, a hydrogen recycling and purification unit is used to recycle and purify hydrogen in the mixed gas to obtain product hydrogen and methane recycling gas; fourth, a methane recycling and purification unit is used to compress and purify the methane recycling gas to obtain product biogas, hydrogen, and methane recycling gas, which are then returned to the hydrocarbon regulation unit for recycling or pressurized before entering the hydrogen recycling and purification unit for recycling.

[0009] Furthermore, the purification unit includes a pre-removal device, a blower, a dry removal device, and a wet desulfurization device connected in sequence: the pre-removal device is used to pre-remove macromolecular hydrocarbon impurities from the biogas crude syngas to obtain pre-removed gas; the blower is used to initially pressurize the pre-removed gas to obtain initially compressed gas; the dry removal device is used to further remove macromolecular hydrocarbons and other impurities from the initially compressed gas to obtain secondary removed gas; the wet desulfurization device is used to remove inorganic sulfur from the secondary removed gas, ultimately obtaining purified syngas and by-product sulfur.

[0010] Furthermore, the hydrocarbon regulation unit includes a centrifugal compressor and a hydrogen upgrading device connected in sequence; wherein, the centrifugal compressor is used to repressurize the purified synthesis gas to obtain secondary compressed gas, and the hydrogen upgrading device is used to adjust the hydrogen content in the secondary compressed gas and the CO content required by the methane upgrading unit as needed; wherein, the hydrogen upgrading device includes a detoxification furnace, a humidifier and a shift converter connected in sequence.

[0011] Furthermore, the acid removal unit includes an acid removal device and a hydrorefining desulfurization device connected in sequence; the acid removal device is used to remove hydrogen sulfide, CO2, etc. from the hydrocarbon conditioning gas to obtain the byproduct CO2, and the hydrorefining desulfurization device is used to react organic sulfur, olefins, etc. in the hydrocarbon conditioning gas with hydrogen to convert organic sulfur into inorganic sulfur, thereby obtaining acid-removed gas; wherein, the acid removal device includes an absorption tower, a flash evaporation tower, a stripping regeneration tower, and a flash decarbonization tower.

[0012] Furthermore, the methane upgrading unit employs a methanation reactor, which is used to convert CO and CO2 in acid degassing into methane at a reaction temperature of 250-450℃.

[0013] Furthermore, the hydrogen recycling and purification unit 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, for purifying hydrogen and obtaining product hydrogen and methane recycled gas.

[0014] Furthermore, the methane recycling and purification unit includes a screw compressor, a circulating membrane separator, and a reciprocating compressor connected in sequence; the screw compressor is used to pressurize the methane recycling gas, the circulating membrane separator is used to separate hydrogen and methane to obtain biomethane, hydrogen, and methane recycling gas, and the reciprocating compressor is used to pressurize the hydrogen and methane recycling gas.

[0015] A method for producing hydrogen from biogas crude syngas and co-producing biogas natural gas is also provided, comprising the following steps:

[0016] S1: The crude biosynthetic gas is passed sequentially through a pre-removal device, a blower, a dry removal device, and a wet desulfurization device to remove macromolecular hydrocarbons and inorganic sulfur impurities, resulting in purified synthetic gas and sulfur by-product.

[0017] S2: The purified synthesis gas is pressurized to 1.5-2.5 MPa for the second time, and the content of hydrogen and carbon monoxide in the gas is adjusted by the shift reaction, and the CO content at the shift outlet is controlled to be 0.8%-13.69%, to obtain hydrocarbon conditioning gas;

[0018] S3: The hydrocarbon conditioning gas is subjected to acid gas removal and hydrogenation desulfurization in sequence to remove hydrogen sulfide, CO2 and organic sulfur, to obtain acid degassing and by-product CO2;

[0019] S4: The acid degassing is introduced into a methanation reactor and a methanation reaction is carried out at 250-450℃ and 1.5-2.0MPa to convert CO and CO2 into methane, resulting in a mixed gas containing hydrogen and methane.

[0020] S5: The mixed gas is purified by pressure swing adsorption to obtain product hydrogen with a purity of ≥99.999% and methane-rich recycled gas.

[0021] S6: The methane recycling gas is sequentially passed through a screw compressor, a circulating membrane separator, and a reciprocating compressor to separate the product biogas, hydrogen, and methane recycling gas. The hydrogen and methane recycling gas are pressurized to 1.5-2.5 MPa by the reciprocating compressor and then returned to step S2 for hydrocarbon adjustment, or pressurized and then entered step S5 for recycling and hydrogen purification.

[0022] Furthermore, in step S5, the pressure swing adsorption uses a composite adsorbent of 5A molecular sieve and activated carbon, and the regeneration pressure is controlled at 0.02-0.05 MPa.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. This invention produces hydrogen with a purity of 99.999% through a series of interconnected purification, hydrocarbon regulation, acid removal, methane upgrading, hydrogen recycling and purification, and methane recycling and purification units. The purification unit removes large molecules and impurities from the crude syngas through pre-removal, dry removal, and wet desulfurization, yielding pure syngas and sulfur as a byproduct. The hydrocarbon regulation unit adjusts the gas composition as needed using a centrifugal compressor and hydrogen upgrading process, effectively regulating hydrogen and methane production and improving resource utilization. The acid removal unit removes hydrogen sulfide and carbon dioxide to obtain acid-desorbed gas free of organic sulfur. The methane upgrading unit uses an adiabatic methanation process to convert CO and CO2 in the acid-desorbed gas into methane, improving both the yield and quality of methane.

[0025] 2. The hydrogen recycling and purification unit of this invention uses pressure swing adsorption (PSA) technology to obtain high-purity hydrogen and methane-rich regeneration tail gas, achieving a hydrogen recovery rate of 96.5% and a methane recovery rate of 98.5%. The methane recycling and purification unit utilizes membrane separation technology and a compressor to separate and purify hydrogen and methane from the regeneration tail gas, then reintroduces these gases into the recycling process, further improving product yield and conversion rate. Effective components such as hydrogen, methane, and carbon monoxide in the biogas are fully utilized and recovered, increasing product added value and reducing energy waste.

[0026] 3. This utility model solves the problems of low hydrogen purity and low raw material utilization efficiency, improves the deep processing and utilization value of biosynthetic gas, and recovers all carbon monoxide, hydrogen, and methane in the biosynthetic gas. At the same time, sulfur and carbon dioxide with a purity greater than 98% (V%) are produced as by-products. All components in the gas are recovered after deep processing to obtain corresponding products, fully exploring and maximizing the value of biosynthetic gas. At the same time, it improves the recovery rate of hydrogen and biomethane, significantly improving the utilization rate of biosynthetic gas, and ultimately realizing the co-production of high-purity hydrogen and high-value biomethane, greatly improving the economic and environmental benefits of biosynthetic gas. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the process system for producing hydrogen from biogas crude syngas and co-producing biogas in an embodiment of this utility model.

[0028] Figure 2 This is a schematic diagram of the structure of the hydrogen recycling and purification unit in this embodiment of the present invention.

[0029] Explanation of reference numerals in the attached diagram: 1. Purification unit; 2. Hydrogen regulation unit; 3. Acid removal unit; 4. Methane upgrading unit; 5. Hydrogen recycling and purification unit; 6. Methane recycling and purification unit; 7. Pre-removal device; 8. Blower; 9. Dry 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 separator; 17. Reciprocating compressor. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] Example 1

[0032] like Figure 1As shown, this utility model provides a process system for producing high-purity hydrogen and co-producing biogas from crude biosynthetic gas, including a purification unit 1, a hydrocarbon regulation unit 2, an acid removal unit 3, a methane upgrading unit 4, a hydrogen recycling and purification unit 5, and a methane recycling and purification unit 6 connected in sequence. The purification unit 1 is used to pre-remove impurities, perform preliminary compression, further remove impurities, and desulfurize the crude biosynthetic gas entering the process system, obtaining purified synthetic gas and sulfur as a byproduct. The hydrocarbon regulation unit 2 is used to pressurize the purified synthetic gas and adjust the hydrogen content in the purified synthetic gas and the methane content in the methane upgrading unit 4 according to the requirements of high-purity hydrogen and biogas, obtaining a hydrocarbon-regulated gas. The acid removal unit 3 is used to remove acidic gases such as hydrogen sulfide and carbon dioxide from the hydrocarbon-regulated gas, and to hydrogenate and convert organic sulfur. The process involves removing CO and CO2 from the acid degas and obtaining acid degassing and CO2 as a byproduct. The methane upgrading unit 4 is used to perform a methanation reaction on the acid degassing, converting CO and CO2 in the acid degassing into methane, and incrementally upgrading the methane in the purified synthesis gas to obtain a mixed gas. The hydrogen recycling and purification unit 5 is used to recycle and purify hydrogen from the mixed gas after the methanation reaction, obtaining product hydrogen with a purity of 99.999% and methane recycling gas. The methane recycling and purification unit 6 is used to compress and separate methane from the methane recycling gas, obtaining biogas (Class II) from the product gas and product biogas, hydrogen, and methane recycling gas from the tail gas. The hydrogen and methane recycling gas can be returned to the hydrocarbon regulation unit 2 for recycling or pressurized by the reciprocating compressor 17 before entering the hydrogen recycling and purification unit 5 for recycling.

[0033] The purification unit 1 includes a pre-removal device 7, a blower 8, a dry removal device 9, and a wet desulfurization device 10 connected in sequence. The pre-removal device 7 is used to pre-remove macromolecular hydrocarbon impurities from the crude biogas to obtain pre-removed gas. The blower 8 is used to initially pressurize the pre-removed gas to obtain initially compressed gas. The dry removal device 9 is used to further remove macromolecular hydrocarbon impurities from the initially compressed gas to obtain secondary removed gas. The wet desulfurization device 10 is used to remove inorganic sulfur from the secondary removed gas, ultimately obtaining purified syngas and by-product sulfur. The dry removal device 9 is a temperature-switching adsorption process and can be configured as one to three stages connected in series. The wet desulfurization device 10 uses a wet oxidation-reduction method to convert hydrogen sulfide in the removed gas into elemental sulfur to obtain by-product sulfur.

[0034] The hydrocarbon regulation unit 2 includes a centrifugal compressor 11 and a hydrogen upgrading device 12 connected in sequence. The centrifugal compressor 11 is used to re-pressurize the purified syngas to obtain a secondary compressed gas. The hydrogen upgrading device 12 is used to adjust the hydrogen content in the secondary compressed gas and the CO content required by the methane upgrading unit 4 as needed. The hydrogen upgrading device 12 includes a detoxification furnace, a humidifier, a first-stage shift converter, and a second-stage shift converter, among other main equipment connected in sequence. This step achieves, for the first time, the effective regulation of hydrogen and methane production by adjusting the CO content at the shift converter outlet.

[0035] The acid removal unit 3 includes an acid removal device 13 and a hydrorefining desulfurization device 14 connected in sequence. The acid removal device 13 is used to remove acidic gases such as hydrogen sulfide and CO2 from the hydrocarbon conditioning gas to obtain the byproduct CO2. The hydrorefining desulfurization device 14 is used to react organic sulfur and olefins in the hydrocarbon conditioning gas with hydrogen to convert organic sulfur into inorganic sulfur, thereby obtaining acid-removed gas. The acid removal device 13 includes main equipment such as an absorption tower, a flash evaporation tower, a stripping regeneration tower, and a flash decarbonization tower, and obtains CO2 with a byproduct volume percentage ≥98%.

[0036] The methane upgrading unit 4 employs a methanation reactor, which is used to convert CO and CO2 from acid degassing into methane via an adiabatic methanation reaction at a temperature of 250-350℃. The methane upgrading unit 4 incrementally upgrades the methane in the purified syngas to increase the yield and quality of biogas. This step marks the first time that methanation has been used in the deep processing of biosyngas to achieve incremental methane upgrading.

[0037] like Figure 2 As shown, 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 the gas after methane upgrading, mainly by using pressure swing adsorption (PSA) to obtain high-purity hydrogen with a purity of 99.999% and regenerated tail gas that can be used for methane recycling. Depending on the hydrogen production and yield requirements, typically 6-10 adsorption towers are used, and both vacuuming and flushing regeneration methods are acceptable. To obtain high-purity hydrogen with a purity of 99.999%, the total content of methane and nitrogen in the product hydrogen must be less than 10%. -6(Volume percentage). High precision in methane and nitrogen removal necessitates the use of a composite adsorbent bed primarily composed of 5A molecular sieves and supplemented by activated carbon. To improve adsorbent utilization efficiency, the regeneration pressure should be controlled at approximately 0.03 MPa. This step is the first to achieve the simultaneous generation of product hydrogen through pressure swing adsorption and the production of biogas feedstock—methane—through desorption. The recycling of hydrogen and methane, the effective components of biosynthetic gas, ensures zero loss of hydrogen and methane in this unit, a key feature of this process system.

[0038] The methane recycling and purification unit 6 includes a screw compressor 15, a circulating membrane separator 16, and a reciprocating compressor 17 connected in sequence. The screw compressor 15 pressurizes the methane recycling gas, the circulating membrane separator 16 separates hydrogen and methane to obtain biomethane, hydrogen, and methane recycling gas, and the reciprocating compressor 17 pressurizes the hydrogen and methane recycling gas. Specifically, biomethane is obtained from the non-permeate side of the membrane. The permeate gas, rich in hydrogen and methane, is pressurized by the reciprocating compressor 17 and returned to the inlet of the hydrogen recycling and purification unit 5 to recover hydrogen from the permeate gas. The remaining methane in the permeate gas is compressed by the screw compressor 15 and re-enters the circulating membrane separator 16. Thus, the regeneration tail gas (i.e., methane recycling gas) generated by the hydrogen recycling and purification unit 5 and the permeate gas (i.e., hydrogen and methane recycling gas) generated by the circulating membrane separator are recycled within the system to increase the production of high-purity hydrogen and biomethane. This step is the first to achieve the recycling and recovery of hydrogen and methane from membrane separation tail gas, thereby increasing the production of hydrogen and biogas, which is one of the important features of this process system.

[0039] Taking the following raw material biogas crude synthesis gas dry basis conditions as an example, the raw material biogas crude synthesis gas dry basis conditions are shown in Table 1:

[0040] Table 1. Raw Material Biomass Crude Synthetic Gas Dry Basis Conditions

[0041] Components <![CDATA[H2]]> CO <![CDATA[CO2]]> <![CDATA[CH4]]> <![CDATA[N2]]> total Vol,% 32.5 39.7 6.8 19 2 100

[0042] Among them, C in biogas 6+ Contains 200mg / Nm 3 Total sulfur content of biogas 5g / Nm 3 .

[0043] Based on the above table of raw material biogas syngas conditions, this embodiment uses a hydrocarbon regulation unit to maximize the conversion of CO into hydrogen, thereby obtaining the maximum hydrogen production and producing biogas as a byproduct, achieving an annual production of 16,200 tons of 99.999% high-purity hydrogen and 46,000 tons of biogas.

[0044] The process system for producing hydrogen from biosynthetic gas and co-producing biogas according to this embodiment is used to purify the above-mentioned raw material, biosynthetic gas. The specific steps are as follows:

[0045] Purification unit 1 includes a pre-removal device 7, a blower 8, a dry removal device 9, and a wet desulfurization device 10, wherein the pre-removal device 7, the blower 8, the dry removal device 9, and the wet desulfurization device 10 are connected in sequence. The crude syngas undergoes preliminary removal of large molecular hydrocarbons to ≤20 mg / Nm³ via the pre-removal device 7. 3 Then, the gas is initially pressurized to 40 kPa·G by blower 8, and then enters the temperature-switching adsorption dry purification device 9 to remove large molecular hydrocarbons from the crude syngas to ≤5 mg / Nm³. 3 Finally, the gas enters the wet desulfurization unit 10. The biomass crude syngas enters from the bottom of the packed desulfurization tower. After the gas comes into countercurrent contact with the PDS desulfurization liquid sprayed down from the top of the packed tower, the H2S in it is removed to ≤50mg / Nm³. 3 The purified syngas and sulfur byproduct are obtained.

[0046] The pre-removal device 7 and blower 8 can be used individually or in parallel. The dry removal device 9 can employ single-stage or multi-stage series temperature-switching adsorption to remove impurities such as macromolecular hydrocarbons. In this embodiment, based on the crude syngas volume, the pre-removal device 7 consists of one unit and two blowers (one operational and one standby). The main equipment for wet desulfurization includes: desulfurization tower, regeneration tank, foam storage tank, and sulfur melting kettle.

[0047] 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. 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. In this embodiment, the purified syngas enters the centrifugal compressor for pressurization 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 at least one centrifugal compressor is used. Furthermore, the purified syngas, after being pressurized by a centrifugal compressor during hydrogen upgrading, does not require a cooler for cooling. It directly enters the feed gas preheater and is preheated to above 230°C through multiple heating steps. Then, it enters the deoxygenator for deoxygenation and purification, followed by a shift reaction in the No. 1 controllable heat transfer converter. A 2.3 MPa·G saturated steam is produced by the water heat transfer tube bundles embedded in the catalyst bed. Simultaneously, the pressure of the by-product steam is used to control the outlet temperature of the No. 1 controllable heat transfer converter at approximately 270°C. The gas then exits the No. 1 controllable heat transfer converter and goes to the feed gas preheater for further heating and purification. It then enters the No. 2 controllable heat transfer converter for another shift reaction. A 1.0 MPa·G saturated steam is produced by the water heat transfer tube bundles embedded in the catalyst bed. Simultaneously, the pressure of the by-product steam is used to control the outlet temperature of the converter at approximately 195°C. The shifted gas exiting the controllable heat transfer converter enters the feed gas preheater for further heating and purification, then enters the shifted gas cooling separator to further cool the gas to approximately 40°C. Finally, the shifted gas is sent to the acid removal unit 3.

[0048] In this embodiment, a two-stage isothermal conversion is employed, utilizing the heat of compression and the heat of reaction to bring the feed gas to the conversion reaction temperature. This ensures a low final outlet temperature, high CO conversion rate, and lower total steam consumption. Simultaneously, the heat of reaction and latent heat produce 2.3 MPa steam and 1.0 MPa steam as byproducts. To achieve maximum hydrogen production, the CO content in the unit outlet gas is controlled to ≤0.8%, with other components and their contents as follows: H2: 51.10%, N2: 1.44%, CH4: 13.66%, CO2: 32.62%, H2O: 0.38%.

[0049] The acid removal unit 3 includes an acid removal device 13 and a hydrorefining desulfurization device 14, wherein the acid removal device 13 and the hydrorefining desulfurization device 14 are connected in sequence. Further, the gas from the hydrocarbon regulation unit 2 first passes through the desulfurization device to remove H2S to ≤10 mg / Nm³. 3The gas then enters the wet decarbonization process. After passing through the raw gas-liquid separator, the gas enters the lower part of the absorption tower. It is first washed with a semi-lean solution in the lower section of the absorption tower, where some H2S and CO2 are absorbed. Then, it is washed with regenerated lean solution in the upper section of the absorption tower to remove CO2 from the purified gas to below 0.1%. The gas then enters the hydrotreating desulfurization unit 14. The adsorbed CO2 is further processed to obtain 98% pure CO2 by-product, which can be used to synthesize urea and produce industrial or food-grade CO2. Further, the decarbonized gas is heated to approximately 220–250°C through a gas-to-gas heat exchanger and a steam heater, and then enters the first-stage hydrogenation reactor. Under the action of a cobalt-molybdenum hydrogenation catalyst, organic sulfur reacts with hydrogen, converting organic sulfur into inorganic sulfur. After hydrogenation conversion, a zinc oxide desulfurizing agent 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.

[0050] In this embodiment, the gas used for the hydrogenation reaction is relatively clean and has a low content of organic sulfur, requiring only a single-stage hydrogenation. The desulfurization tower consists of two towers, which can be paralleled or connected in series. If necessary, it can also be configured as a single-stage hydrogenation followed by a two-stage hydrogenation process.

[0051] The methane upgrading unit 4 includes a methanation reactor, a cooler, and a gas-liquid separator. The deacidified gas from the hydrodesulfurization unit 14 enters the methanation reactor, where CO and CO2 are converted into methane under the action of a catalyst. The methane upgrading outlet gas exchanges heat with the decarbonized gas from the acid removal unit to preheat the temperature of the decarbonized gas entering the hydrodesulfurization reactor. It is then cooled to below 40°C by the cooler before entering the hydrogen recycling and purification unit 5.

[0052] In this embodiment, an adiabatic methanation process is used, with a methanation reaction temperature of 250–350°C and a reaction pressure of 1.75 MPa.G. The methane content in the outlet gas of the methane upgrading unit is approximately 22.31%, and the hydrogen content is approximately 75.05%.

[0053] The hydrogen recycling and purification unit 5 includes a feed gas and recycled tail gas mixing tank, a hydrogen purification adsorption tower group, and a recycled tail gas mixing tank connected in sequence. The PSA adopts an 8-tower flushing process, including adsorption, pressure equalization and depressurization, forward release, reverse release, flushing, pressure equalization and pressurization, and final pressurization. Further, the hydrogen-rich gas after methane upgrading, with a pressure of approximately 1.7 MPa.G, is mixed with hydrogen and methane recycled gas from the methane recycling and purification unit 6 in the feed gas and recycled tail gas mixing tank, and then enters the adsorption tower, which is currently in the adsorption state, from the bottom of the tower. Under the sequential selective adsorption of various adsorbents, impurities are adsorbed, and the unadsorbed hydrogen flows out as a product from the top of the tower, resulting in high-purity hydrogen with a purity greater than 99.999% (CO≤0.2ppm, CO2≤2ppm) and a pressure greater than 1.6 MPa.G, meeting the hydrogen requirements for fuel cell vehicles. After regeneration steps such as reverse discharge and flushing, the methane-rich regenerated tail gas (regeneration and regeneration gas pressure is 0.05-0.02MPa) is mixed and buffered in the circulating tail gas mixing tank before being sent to the recycling and purification unit 6 for methane.

[0054] In this example, the feed gas composition of this unit is (H2: 76.24%, N2: 2.22%, CH4: 21.54%), and the product hydrogen is 99.999% (CO≤0.2ppm, CO2≤2ppm) high-purity hydrogen that meets the hydrogen requirements for fuel cell vehicles. Therefore, a combined adsorption bed of activated alumina, silica gel, activated carbon, and 5A molecular sieve is required.

[0055] The methane recycling and purification unit 6 includes a screw compressor 15, a circulating membrane separator 16, and a reciprocating compressor 17, which are connected in sequence. Further, the regeneration 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 separator 16. After filtration, it is heated to 50°C and subjected to circulating membrane separation, where H2 and CH4 are separated and purified. The sludge side yields 1.0 MPa.G of biomethane, with a CH4 content ≥85% vol and an H2 content of approximately 5%. The H2 concentration on the permeate side can be increased from 36% to over 79%.

[0056] The permeate gas contains 79.8% hydrogen and 16.62% methane, which can be recycled. The membrane permeate gas, rich in hydrogen and methane, is pressurized to 1.75 MPa.G by reciprocating compressor 17, and then returned to the inlet of the hydrogen recycling and purification unit 5 to recycle and recover hydrogen and methane, thereby increasing the production of high-purity hydrogen and biogas.

[0057] In this example, the hydrogen recovery rate reached 96.5% and the methane recovery rate reached 98.5%, both higher than the recovery rates of existing processes.

[0058] Example 2

[0059] Based on the aforementioned raw material biogas crude synthesis conditions, this embodiment differs from Example 1 in that the CO conversion rate is adjusted in the hydrocarbon regulation unit to achieve the optimal CO to H2 content ratio, and all CO is converted into methane in the methane upgrading unit to increase and upgrade methane production. Through the control of the hydrocarbon regulation unit and the methane upgrading unit, the maximum biogas production is obtained with hydrogen as a byproduct, achieving an annual production of 0.11 million tons of 99.999% high-purity hydrogen and 7.7 million tons of biogas.

[0060] Specifically, in this embodiment, purification unit 1 is the same as in embodiment 1, where large molecular hydrocarbons in the crude syngas are removed to ≤5 mg / Nm³. 3 H2S was removed to ≤50 mg / Nm³ 3 The purified syngas and sulfur byproduct are obtained.

[0061] In this embodiment, to achieve maximum biogas production, the CO content in the unit outlet gas is controlled at approximately 13.69% by adjusting the water replenishment ratio. The other components and their contents are: H2: 44.91%, N2: 1.62%, CH4: 15.42%, CO2: 24.05%, and H2O: 0.29%.

[0062] In this embodiment, the acid removal unit 3 is the same as in embodiment 1, using zinc oxide desulfurizing agent to remove the total sulfur content in the shift gas to less than 0.1 ppm. The removed CO2 is then processed to obtain by-product CO2 with a purity of 98%, which can be used to synthesize urea and produce industrial or food-grade CO2.

[0063] In this embodiment, the methane upgrading unit 4 adopts an adiabatic methanation process. The methanation reaction temperature is 250-450°C, the reaction pressure is 1.75 MPa.G, and the methane content in the outlet gas of the methane upgrading unit is about 83.90%, and the hydrogen content is about 11.04%.

[0064] The hydrogen recycling and purification unit 5 employs a 7-tower flushing PSA process. Further, the methane-rich gas, after methane upgrading, with a pressure of approximately 1.7 MPa.G, is mixed with hydrogen and methane recycling gas from the methane recycling and purification unit 6 in a feed gas buffer tank, and then enters the adsorption tower, which is currently in an adsorption state, from the bottom. Under the sequential selective adsorption of various adsorbents, non-hydrogen gases such as methane and nitrogen are adsorbed, while the unadsorbed hydrogen flows out as a product from the top of the tower, yielding high-purity hydrogen with a purity greater than 99.999% (CO≤0.2ppm, CO2≤2ppm) and a pressure greater than 1.6 MPa.G, meeting the hydrogen requirements for fuel cell vehicles. After regeneration steps such as reverse discharge and flushing, the methane-rich regeneration tail gas (regeneration and regeneration gas pressure 0.05-0.02 MPa) is returned to the methane recycling and purification unit 6.

[0065] In this example, the feed gas composition of the unit is (H2: 13.84%, N2: 4.71%, CH4: 81.08%), and the product hydrogen is 99.999% (CO≤0.2ppm, CO2≤2ppm) high-purity hydrogen that meets the hydrogen requirements for fuel cell vehicles. A combined adsorption bed of activated alumina, silica gel, activated carbon, and 5A molecular sieve is used, with activated carbon as the main component.

[0066] The regenerated tail gas from the hydrogen recycling and purification unit 5 is pressurized to 1.1 MPa.G by screw compressor 15 and then enters the circulating membrane separator 16. It is first filtered, then heated to 50°C for circulating membrane separation, where H2 and CH4 are separated and purified. The sludge side yields 1.0 MPa.G of biomethane with a CH4 content ≥94.27%. The H2 concentration on the permeate side can be increased from 5.32% to over 28.61%. The permeate contains 28.61% hydrogen and 64.37% methane, which can be recovered and reused. The hydrogen- and methane-rich permeate is pressurized to 1.75 MPa.G by reciprocating compressor 17 and then returned to the inlet of the hydrogen recycling and purification unit 5 for further hydrogen and methane recycling, thereby increasing the yield of high-purity hydrogen and biomethane. This step is a key feature of this process system.

[0067] In this embodiment, the amount of membrane permeate gas rich in hydrogen and methane is half that in Example 1. The membrane permeate gas rich in hydrogen and methane can also be recovered after being pressurized by centrifugal compressor 11.

[0068] The beneficial effects of this utility model are as follows:

[0069] ① Bio-based crude syngas is a new green and environmentally friendly hydrogen production feedstock. The hydrogen produced by this process has a purity of 99.999%. The purity and impurity content of the hydrogen can simultaneously meet the technical requirements for high-purity hydrogen in GB / T 3634.2-2011 Hydrogen Part 2 and the technical requirements for fuel hydrogen for proton exchange membrane fuel cell vehicles in GB / T 37244-2018, resulting in higher quality and value of hydrogen.

[0070] ② Biogas produced by this process system from crude biogas meets the technical requirements for Class II biogas in GB / T41328-2022 "Biogas". The effective components such as hydrogen, methane, and carbon monoxide in the crude biogas are fully utilized and recovered, increasing product added value and reducing energy waste.

[0071] ③ The regenerated tail gas from the hydrogen recycling and purification unit is then recycled to the methane recycling and purification unit. The hydrogen- and methane-rich permeate gas from the circulating membrane separation permeate side is returned to the inlet of the hydrogen recycling and purification unit 5. Throughout the process, all hydrogen- and methane-rich tail gas, excluding the product, is recycled and reused. With a product hydrogen purity of 99.999% and methane quality meeting the requirements for Class II biogas, the hydrogen recovery rate reaches 96.5%, and the methane recovery rate reaches 98.5%, which are higher than those of existing processes. Hydrogen and biogas production is higher, and the effective utilization rate of the biogas crude syngas is also higher.

[0072] ④ The production of high-purity hydrogen and biogas can be adjusted according to market conditions. 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 hydrocarbon conditioning unit to increase hydrogen production. When the market price of high-purity hydrogen is low, a small portion of the carbon monoxide in the crude syngas can be converted into hydrogen in the hydrocarbon conditioning unit, while the majority of the remaining carbon monoxide is converted into methane in the methane upgrading section to increase biogas production. The production of high-purity hydrogen and biogas can be adjusted according to market prices, enhancing the company's ability to withstand risks and facilitating the industrialization of biogas crude syngas utilization.

[0073] ⑤ Improve the value of deep processing of biogas crude syngas. All carbon monoxide, hydrogen and methane in biogas crude syngas are recovered. At the same time, sulfur and carbon dioxide with a purity of more than 98% (V%) are produced as by-products. All components in the gas are recovered after deep processing and corresponding products are obtained, so as to fully explore and maximize the value of biogas crude syngas.

[0074] In summary, this invention, through the cooperation and recycling of multiple units, firstly achieves deep processing of the raw gas and regeneration of hydrogen and methane through steps such as purification, hydrocarbon adjustment, acid removal, and methane upgrading. Secondly, high-purity hydrogen is extracted through a purification process and recycled to increase hydrogen production. Thirdly, biogas is further purified using circulating membrane separation technology and recycled using a compressor to further increase biogas production.

[0075] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present utility model. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present utility model without departing from the scope of the present utility model shall still fall within the scope of the present utility model.

Claims

1. A process system for hydrogen co-production from bio-raw synthesis gas for bio- natural 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 hydrogen recycling and purification unit (5), and a methane recycling and purification unit (6) connected in sequence. The purification unit (1) is used to pre-remove impurities, perform preliminary compression, further remove impurities, and desulfurize the crude biosynthetic gas entering the process system to obtain purified synthetic gas and by-product sulfur; the hydrocarbon regulation unit (2) is used to pressurize the purified synthetic gas and regulate the hydrogen content in the purified synthetic gas and the methane content in the methane upgrading unit (4) to obtain hydrocarbon regulation gas; the acid removal unit (3) is used to remove acidic gases from the hydrocarbon regulation gas to obtain acid degas and by-product CO2; the methane upgrading unit (4) is used to perform a methanation reaction on the acid degas to remove acid from the gas. CO and CO2 in the gas are converted into methane, and the methane in the purified synthesis gas is incrementally upgraded to obtain a mixed gas; the hydrogen recycling and purification unit (5) is used to recycle and purify hydrogen in the mixed gas to obtain product hydrogen and methane recycling gas; the methane recycling and purification unit (6) is used to compress and purify methane in the methane recycling gas to obtain product biogas, hydrogen and methane recycling gas, and the hydrogen and methane recycling gas are returned to the hydrocarbon regulation unit (2) for recycling or pressurized and then entered the hydrogen recycling and purification unit (5) for recycling.

2. The process system for co-production of hydrogen and bio-SNG from crude syngas according to claim 1, characterized in that, The purification unit (1) includes a pre-removal device (7), a blower (8), a dry removal device (9), and a wet desulfurization device (10) connected in sequence: the pre-removal device (7) is used to remove macromolecular hydrocarbon impurities from the biomass crude synthesis gas to obtain pre-removed gas; the blower (8) is used to initially pressurize the pre-removed gas to obtain initially compressed gas; the dry removal device (9) is used to further remove macromolecular hydrocarbon impurities from the initially compressed gas to obtain secondary removal gas; the wet desulfurization device (10) is used to remove inorganic sulfur from the secondary removal gas, and finally obtain purified synthesis gas and by-product sulfur.

3. The process system for co-production of hydrogen and bio-natural gas from crude syngas according to claim 1, wherein, The hydrocarbon regulation unit (2) includes a centrifugal compressor (11) and a hydrogen upgrading device (12) connected in sequence. The centrifugal compressor (11) is used to pressurize the purified synthesis gas to obtain a secondary compressed gas. The hydrogen upgrading device (12) is used to adjust the hydrogen content in the secondary compressed gas and the CO content required by the methane upgrading unit (4) as needed. The hydrogen upgrading device (12) includes a detoxification furnace, a humidifier and a conversion furnace connected in sequence.

4. The process system for co-production of hydrogen and bio-natural gas from crude syngas according to claim 1, wherein, The acid removal unit (3) includes an acid removal device (13) and a hydrorefining desulfurization device (14) connected in sequence. The acid removal device (13) is used to remove hydrogen sulfide and CO2 from the hydrocarbon conditioning gas to obtain CO2 as a byproduct. The hydrorefining desulfurization device (14) is used to react organic sulfur and olefins in the hydrocarbon conditioning gas with hydrogen to convert organic sulfur into inorganic sulfur and obtain acid-removed gas. The acid removal device (13) includes an absorption tower, a flash tower, a stripping regeneration tower and a flash decarbonization tower.

5. The process system for co-production of hydrogen and bio-natural gas from crude syngas according to claim 1, wherein, The methane upgrading unit (4) adopts a methanation reactor, which is used to convert CO and CO2 in acid degassing into methane, and the reaction temperature is 250-450℃.

6. The process system for co-production of hydrogen and bio-natural gas from crude syngas according to claim 1, wherein, 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, which are used to purify hydrogen and obtain product hydrogen and methane recycled gas.

7. The process system for co-production of hydrogen and bio-natural gas from crude syngas according to claim 1, wherein, The methane recycling and purification unit (6) includes a screw compressor (15), a circulating membrane separator (16), and a reciprocating compressor (17) connected in sequence. The screw compressor (15) is used to pressurize the methane recycling gas, the circulating membrane separator (16) is used to separate hydrogen and methane to obtain biomethane, hydrogen, and methane recycling gas, and the reciprocating compressor (17) is used to pressurize the hydrogen and methane recycling gas.

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