A process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas

Abstract

The present invention relates to the technical field of organic solid waste treatment, and in particular to a process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas, comprising a purification unit, a carbon-hydrogen regulating unit, an acid removal unit, a methane upgrading unit, a recycling and purification unit for hydrogen, and a recycling and purification unit for methane, which are connected in sequence. The purification unit removes impurities through pre-impurity removal, compression, dry impurity removal, and wet desulfurization to produce purified synthesis gas and sulfur; the carbon-hydrogen regulating unit pressurizes and adjusts the hydrogen-carbon ratio through 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; the recycling unit purifies hydrogen through pressure swing adsorption and recovers methane using membrane separation technology to produce bio-natural gas. The present invention solves the problems of low purity and insufficient raw material utilization in traditional processes through a recycling process, achieves the co-production of high-purity hydrogen and bio-natural gas, and increases the added value of resources.

Description

Technical Field

[0001] The present invention relates to the technical field of organic solid waste treatment, and in particular to a process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas. Background Art

[0002] In the current energy and environmental protection fields, biosyngas, a gas derived from the pyrolysis and gasification of household waste or biomass feedstock, whose main components include hydrogen, methane, carbon monoxide, and carbon dioxide, is gaining widespread attention. Its industrial application is still in its early stages, and the path to industrialized hydrogen production from waste is still being explored, currently at the research and demonstration stage.

[0003] Existing methods for processing crude biogas primarily focus on combustion for power generation and hydrogen production. However, this approach suffers from a relatively low overall utilization rate. Specifically, high-value-added components in the crude biogas, such as methane, are not fully utilized and cannot be fully extracted and converted into relevant products.

[0004] Currently, the deep processing and utilization of crude biogas primarily involves producing hydrogen with a purity of 99.9-99.99%. For example, patent application number 202310529013.7, titled "A Process for Hydrogen Production from Carbonized and Gasified Municipal Waste," describes a process for producing 99.9% hydrogen from crude biogas through a series of steps, including conversion, decarbonization and desulfurization, and PSA. However, this method has significant drawbacks. It focuses solely on hydrogen production, failing to fully utilize and recover the methane in the crude syngas. Furthermore, hydrogen from the PSA desorption gas is not recovered, resulting in significant hydrogen losses. Overall utilization needs to be improved urgently.

[0005] For example, patent application number 202310485108.3, titled "Apparatus and Method for Producing Hydrogen from Domestic Waste and / or Organic Matter," claims that crude biosyngas can produce 99.99% hydrogen through a series of processes, including desulfurization, shift 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 syngas, resulting in a relatively limited product route. Summary of the Invention

[0006] The present invention provides a process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas. The process system solves the problems of low hydrogen purity and low raw material utilization efficiency, and improves the recovery rate of hydrogen and bio-natural gas.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas, comprising a purification unit, a carbon-hydrogen regulating 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; wherein the purification unit is used to perform pre-impurity removal, preliminary compression, further impurity removal and desulfurization on the bio-crude synthesis gas entering the process system to obtain purified synthesis gas and by-product sulfur; the carbon-hydrogen regulating unit is used to pressurize the purified synthesis gas and regulate the content of hydrogen in the purified synthesis gas and the content of methane in the methane upgrading unit to obtain carbon-hydrogen regulated gas; the acid removal unit is used to remove acid gas from the carbon-hydrogen regulated gas to obtain acid degassing and by-product CO2; the methane upgrading unit is used to The acid degassing performs a methanation reaction to convert CO and CO2 in the acid degassing into methane, and the methane in the purified synthesis gas is incrementally upgraded to obtain a mixed gas; the circulating recovery and purification hydrogen unit is used to circulate and recover the mixed gas, and at the same time, a pressure swing adsorption process is used to purify the hydrogen to obtain product hydrogen and methane circulating recovery gas; the circulating recovery and purification methane unit includes a screw compressor, a circulating membrane separation device and a reciprocating compressor, which are used to pressurize and separate the methane circulating recovery gas to obtain product biogas, hydrogen and methane circulating recovery gas. The hydrogen and methane circulating recovery gas are pressurized by the reciprocating compressor and then return to the carbon-hydrogen adjustment unit or enter the circulating recovery and purification hydrogen unit, and the pressure swing adsorption regeneration pressure is controlled at 0.02-0.05MPa.

[0009] Furthermore, the purification unit includes a pre-impurity removal device, a blower, a dry impurity removal device and a wet desulfurization device connected in sequence: the pre-impurity removal device is used to pre-remove impurities such as macromolecular hydrocarbon compounds in the crude biosynthesis gas to obtain pre-impurity-removed gas, and the blower is used to preliminarily pressurize the pre-impurity-removed gas to obtain preliminary compressed gas; the dry impurity removal device is used to further remove impurities such as macromolecular hydrocarbon compounds in the preliminary compressed gas to obtain secondary impurity-removed gas; the wet desulfurization device is used to remove inorganic sulfur in the secondary impurity-removed gas, and finally obtain purified synthesis gas and by-product sulfur.

[0010] Furthermore, the carbon-hydrogen regulation unit includes a centrifugal compressor and a hydrogen upgrading device connected in sequence; wherein, the centrifugal compressor is used to perform secondary pressurization on 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 on demand; wherein, the hydrogen upgrading device includes a detoxification furnace, a humidifier and a conversion furnace connected in sequence.

[0011] Furthermore, the acid degassing unit includes an acid degassing device and a hydrogenation desulfurization device connected in sequence; the acid degassing device is used to remove hydrogen sulfide, CO2, etc. in the hydrocarbon adjustment gas to obtain by-product CO2, and the hydrogenation desulfurization device is used to hydrogenate the organic sulfur, olefins, etc. in the hydrocarbon adjustment gas with hydrogen to convert the organic sulfur into inorganic sulfur to obtain acid degassing; wherein, the acid degassing device includes an absorption tower, a flash tower, a stripping regeneration tower and a flash gas decarbonization tower.

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

[0013] Furthermore, the recycling and purification hydrogen unit includes a raw gas and recycling tail gas mixing tank, a purified hydrogen adsorption tower group and a recycling tail gas mixing tank connected in sequence, which is used to purify hydrogen and obtain product hydrogen and methane recycling recovery gas.

[0014] Furthermore, the process system for producing hydrogen and co-producing bio-natural gas by using the bio-crude synthesis gas comprises the following steps: S1: passing the bio-crude synthesis gas through a pre-impurity removal device, a blower, a dry impurity removal device and a wet desulfurization device in sequence to remove macromolecular hydrocarbon compounds and inorganic sulfur impurities, thereby obtaining purified synthesis gas and by-product sulfur; S2: performing a secondary pressurization on the purified synthesis gas to 1.5-2.5 MPa, and adjusting the hydrogen and carbon monoxide contents in the gas through a shift reaction, controlling the CO content at the shift outlet to 0.8%-13.69%, thereby obtaining a hydrocarbon adjustment gas; S3: performing acid gas removal and hydrodesulfurization on the hydrocarbon adjustment gas in sequence to remove hydrogen sulfide, CO2 and organic sulfur, thereby obtaining acid degassing and by-product CO2; S 4: The degassed acid is passed into a methanation reactor, and a methanation reaction is carried out at 250-450°C and 1.5-2.0 MPa to convert CO and CO2 into methane to obtain a mixed gas containing hydrogen and methane; S5: The mixed gas is purified by a pressure swing adsorption process to obtain hydrogen product with a purity of ≥99.999% and methane-rich methane recycled gas; S6: The methane recycled gas is passed through a screw compressor, a circulating membrane separation device and a reciprocating compressor in sequence to separate the product biogas, hydrogen and methane recycled gas; the hydrogen and methane recycled gas are pressurized to 1.5-2.5 MPa by the reciprocating compressor and then returned to step S2 for carbon-hydrogen adjustment or pressurized and then enter step S5 for recycling and purification of hydrogen.

[0015] Furthermore, in step S5, pressure swing adsorption uses a composite adsorbent of 5A molecular sieve and activated carbon.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention produces hydrogen with a purity of 99.999% by sequentially connecting a purification unit, a hydrocarbon adjustment unit, an acid removal unit, a methane upgrading unit, a hydrogen recycling and purification unit, and a methane recycling and purification unit. The purification unit removes macromolecules and impurities from crude synthesis gas through pre-impurity removal, dry impurity removal, and wet desulfurization to obtain pure synthesis gas and byproduct sulfur. The hydrocarbon adjustment unit adjusts the gas composition on demand through a centrifugal compressor and a hydrogen upgrading process, effectively regulating the production of hydrogen and methane and improving resource utilization. The acid removal unit removes hydrogen sulfide and carbon dioxide to obtain acid degassing free of organic sulfur. The methane upgrading unit uses an adiabatic methanation process to convert CO and CO2 in the acid degassing into methane, thereby improving the production and quality of methane.

[0018] 2. The present invention's circulating hydrogen recovery and purification unit produces high-purity hydrogen and methane-rich regenerated tail gas through a pressure swing adsorption process, with hydrogen recovery rates reaching 96.5% and methane recovery rates reaching 98.5%. The circulating methane recovery and purification unit utilizes membrane separation technology and a compressor to separate and purify hydrogen and methane from the regenerated tail gas and reintroduce these gases into the circulation process, further improving product yield and conversion rate. Effective components such as hydrogen, methane, and carbon monoxide in the crude biosyngas are fully utilized and recovered, increasing product added value and reducing energy waste.

[0019] 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 bio-crude synthesis gas, and recovers all carbon monoxide, hydrogen, and methane in the bio-crude synthesis gas. At the same time, sulfur and carbon dioxide with a purity greater than 98% (V%) are produced as by-products. After deep processing, all components in the gas are recovered and corresponding products are obtained, fully exploring and maximizing the value of bio-crude synthesis gas; at the same time, the recovery rate of hydrogen and bio-natural gas is improved, and the utilization rate of bio-crude synthesis gas is significantly improved, ultimately realizing the co-production of high-purity hydrogen and high-value bio-natural gas, greatly improving the economic and environmental benefits of bio-crude synthesis gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of a process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas in an embodiment of the present invention.

[0021] Figure 2 It is a schematic structural diagram of a hydrogen recycling and purification unit in an embodiment of the present invention.

[0022] Explanation of the accompanying symbols: 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

[0023] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the specific embodiments of this application and the corresponding drawings. Obviously, the embodiments described are only some of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0024] Example 1

[0025] like Figure 1 As shown, the present invention provides a process system for producing 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 recycling and purification hydrogen unit 5 and a recycling and purification methane unit 6 connected in sequence; wherein, the purification unit 1 is used to perform pre-impurity removal, preliminary compression, further impurity removal and desulfurization on 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 to pressurize the purified synthesis gas, and adjust 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 to remove acid gases such as hydrogen sulfide and carbon dioxide in the gas after carbon-hydrogen regulation, and hydrogenate and desulfurize the organic sulfur. The methane upgrading unit 4 is used to perform a methanation reaction on the acid degassing, convert CO and CO2 in the acid degassing into methane, and incrementally upgrade the methane in the purified synthesis gas to obtain a mixed gas; the recycling and purification hydrogen unit 5 is used to recycle and purify the mixed gas after the methanation reaction to obtain product hydrogen and methane recycling gas with a purity of 99.999%; the recycling and purification methane unit 6 is used to compress the methane recycling gas and separate methane, obtain biogas (type II) from the product gas, obtain product biogas and hydrogen and methane recycling gas from the tail gas, and the hydrogen and methane recycling gas can be returned to the carbon-hydrogen adjustment unit 2 for recovery or pressurized by the reciprocating compressor 17 and then enter the recycling and purification hydrogen unit 5 for recovery.

[0026] 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, which are connected in sequence. The pre-impurity removal device 7 is used to pre-impurify the macromolecular hydrocarbon compound impurities in the crude biosyngas to produce pre-impurity-removed gas. The blower 8 is used to initially pressurize the pre-impurity-removed gas to produce primary compressed gas. The dry impurity removal device 9 is used to further remove impurities such as macromolecular hydrocarbon compounds from the primary compressed gas to produce secondary impurity-removed gas. The wet desulfurization device 10 is used to remove inorganic sulfur from the secondary impurity-removed gas, ultimately producing purified synthesis gas and byproduct sulfur. The dry impurity removal device 9 is a temperature swing adsorption device that can be configured as one to three stages in series. The wet desulfurization device 10 uses a wet redox process to convert hydrogen sulfide in the removed gas into elemental sulfur to produce byproduct sulfur.

[0027] The hydrocarbon adjustment unit 2 includes a centrifugal compressor 11 and a hydrogen upgrading device 12, which are connected in sequence. The centrifugal compressor 11 is used to re-pressurize the purified synthesis gas to produce secondary compressed gas, and 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, which are connected in sequence. This step achieves the first effective regulation of hydrogen and methane production by adjusting the CO content at the shift converter outlet.

[0028] The acid removal unit 3 includes an acid removal device 13 and a hydrogenation desulfurization device 14 connected in sequence; the acid removal device 13 is used to remove acid gases such as hydrogen sulfide and CO2 in the hydrocarbon adjustment gas to obtain by-product CO2, and the hydrogenation desulfurization device 14 is used to hydrogenate the organic sulfur, olefins, etc. in the hydrocarbon adjustment gas with hydrogen to convert the organic sulfur into inorganic sulfur to obtain acid degassing; wherein, the acid removal device 13 includes main equipment such as an absorption tower, a flash tower, a steam stripping regeneration tower and a flash gas decarbonization tower to obtain CO2 with a by-product volume percentage of ≥98%.

[0029] The methane upgrading unit 4 utilizes a methanation reactor, which converts CO and CO₂ from the acid degassing into methane through an adiabatic methane conversion reaction at a temperature of 250-350°C. This unit incrementally upgrades the methane in the purified syngas to improve biogas yield and quality. This step marks the first time in the biosyngas deep processing process that a methanation reaction is used to achieve incremental methane upgrading.

[0030] like Figure 2As shown, the recycling and purification hydrogen unit 5 includes a raw gas and recycling tail gas mixing tank, a purified hydrogen adsorption tower group and a recycling tail gas mixing tank connected in sequence. The recycling and purification hydrogen unit 5 purifies the gas after the methane is upgraded, mainly by using a pressure swing adsorption process to obtain high-purity hydrogen with a purity of 99.999% and regenerated tail gas that can be used for methane recycling. According to the hydrogen production and yield requirements, there are usually 6-10 adsorption towers, and both vacuuming and flushing regeneration methods are acceptable. In order 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 methane and nitrogen removal requires the use of a composite adsorbent bed composed primarily of 5A molecular sieve and supplemented with activated carbon. To maximize adsorbent utilization, the regeneration pressure should be controlled at 0.03 MPa. This step, for the first time, utilizes pressure swing adsorption to produce hydrogen product while simultaneously recovering methane recycling gas, the raw material for biogas production, from the desorbed gas. This recycling of hydrogen and methane from the active components of biosyngas eliminates any hydrogen or methane losses within this unit, a key feature of this process system.

[0031] The methane recycling and purification unit 6 comprises a screw compressor 15, a circulating membrane separation unit 16, and a reciprocating compressor 17, connected in series. The screw compressor 15 is used to pressurize the methane recycling gas, the circulating membrane separation unit 16 is used to separate hydrogen and methane to produce product biogas, hydrogen, and methane recycling gas, and the reciprocating compressor 17 is used to pressurize the hydrogen and methane recycling gas. The product biogas 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 then returned to the inlet of the hydrogen recycling and purification unit 5 to recover the hydrogen in the permeate. The remaining methane in the permeate is compressed by the screw compressor 15 and then re-enters the circulating membrane separation unit 16. In this way, the regenerated tail gas (i.e., methane recycling gas) produced by the hydrogen recycling and purification unit 5 and the permeate gas (i.e., hydrogen and methane recycling gas) produced by the circulating membrane separation are recycled within the system, thereby increasing the production of high-purity hydrogen and biogas. This step realizes the recycling and recovery of hydrogen and methane in the membrane separation tail gas for the first time to increase the output of product hydrogen and biogas, which is one of the important features of this process system.

[0032] Taking the following raw material bio-crude syngas dry basis conditions as an example, the raw material bio-crude syngas dry basis conditions are shown in Table 1:

[0033] Table 1 Dry basis conditions of raw bio-crude syngas

[0034]

[0035] Among them, C in biogas 6+Contains 200mg / Nm 3 、Total sulfur content of biogas 5g / Nm 3 .

[0036] Based on the raw biomass syngas conditions in the table above, this embodiment uses a carbon-hydrogen regulating unit to maximize the conversion of CO into hydrogen, thereby maximizing hydrogen production and producing biogas as a by-product, achieving an annual output of 16,200 tons of 99.999% high-purity hydrogen and 46,000 tons of biogas.

[0037] The raw bio-crude synthesis gas is purified by the process system for producing hydrogen from bio-crude synthesis gas and producing bio-natural gas according to this embodiment. The specific steps are as follows:

[0038] 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, wherein the pre-impurity removal device 7, the blower 8, the dry impurity removal device 9 and the wet desulfurization device 10 are sequentially connected. The crude synthesis gas is initially removed from the macromolecular hydrocarbon compounds to ≤20mg / Nm 3 Then, the gas is initially pressurized to 40 kPa.G by the blower 8, and then enters the temperature swing adsorption dry impurity removal device 9 to remove the macromolecular hydrocarbon compounds in the crude synthesis gas to ≤5 mg / Nm 3 Finally, it enters the wet desulfurization device 10. The bio-crude synthesis gas enters from the lower part of the packed desulfurization tower. After the gas contacts the PDS desulfurization liquid sprayed from the top of the packed tower in reverse, the H2S in it is removed to ≤50mg / Nm 3 , obtaining purified synthesis gas and by-product sulfur.

[0039] The pre-impurity removal device 7 and blower 8 can be used singly or in parallel. The dry impurity removal device 9 can utilize one or more series-connected temperature swing adsorption stages to remove impurities such as macromolecular hydrocarbons. In this embodiment, based on the crude syngas volume, one pre-impurity removal device 7 and two blowers are used (one in operation and one in standby). The main wet desulfurization equipment includes a desulfurization tower, regeneration tank, foam storage tank, and sulfur melting kettle.

[0040] The hydrocarbon adjustment unit 2 includes a centrifugal compressor 11 for secondary pressurization of the purified synthesis gas, and a hydrogen upgrading device 12 for adjusting the hydrogen content in the purified synthesis gas and the CO content required by the subsequent methane upgrading unit 4 on demand. The centrifugal compressor 11 and the hydrogen upgrading device 12 are sequentially connected. Furthermore, the purified synthesis gas is pressurized in the centrifugal compressor according to the specific application environment of the subsequent process. In this embodiment, the purified synthesis gas enters the centrifugal compressor and is pressurized to 2.0 MPa. In this embodiment, the purified synthesis gas after passing through the purification unit is relatively clean, so a centrifugal compressor is selected to pressurize the purified synthesis gas, and at least one centrifugal compressor is used. Furthermore, in the hydrogen upgrading process, the purified synthesis gas after being pressurized by the centrifugal compressor does not need to be cooled by the cooler, and directly enters the raw gas preheater for multi-step heating and preheating to above 230°C, then enters the deaerator for deoxygenation and purification, and then enters the No. 1 controllable heat transfer shift furnace for shift reaction, and uses the water heat transfer tube bundle buried in the catalyst bed to produce 2.3Mpa.G saturated steam as a by-product. At the same time, the pressure of the by-product steam is used to control the outlet temperature of the No. 1 controllable heat transfer shift furnace to be about 270°C. Then, the gas leaves the No. 1 controllable heat transfer shift furnace to go to the raw gas preheater for heating and purification of the synthesis gas, and then enters the No. 2 controllable heat transfer shift furnace for shift reaction, and uses the water heat transfer tube bundle buried in the catalyst bed to produce 1.0Mpa.G saturated steam as a by-product. At the same time, the pressure of the by-product steam is used to control the outlet temperature of the shift furnace to be about 195°C. The shifted gas leaving the controllable heat transfer shift furnace enters the raw gas preheater for heating and purification of the synthesis gas, and then enters the shift gas cooling separator to further cool the gas to about 40°C. Finally, the shifted gas is sent to the acid removal unit 3.

[0041] In this embodiment, a two-stage isothermal shift is employed, utilizing the heat of compression and reaction to bring the feed gas to the shift reaction temperature. This ensures a low final outlet temperature, high CO conversion, and minimal total steam consumption. The reaction and latent heat simultaneously generate 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%. The other components and their contents are: H2: 51.10%, N2: 1.44%, CH4: 13.66%, CO2: 32.62%, and H2O: 0.38%.

[0042] The acid removal unit 3 includes an acid removal device 13 and a hydrofining desulfurization device 14, wherein the acid removal device 13 and the hydrofining desulfurization device 14 are connected in sequence. Furthermore, the gas from the carbon and hydrogen adjustment unit 2 is firstly removed by the desulfurization device to remove H2S in the gas to ≤10mg / Nm 3, then enters wet decarbonization. After passing through the feed gas gas-liquid separator, the gas enters the lower section of the absorption tower. The gas is first scrubbed with semi-lean liquid in the lower section of the absorption tower, where some H2S and CO2 are absorbed. The gas is then scrubbed with regenerated lean liquid in the upper section of the absorption tower, removing CO2 from the purified gas to below 0.1%. The gas then enters the hydrodesulfurization unit 14. The adsorbed CO2 undergoes subsequent treatment to produce a 98% pure byproduct CO2, which can be used to synthesize urea and produce industrial or food-grade CO2. The decarbonized gas is then heated to approximately 220-250°C via a gas-to-gas heat exchanger and steam heater before entering the primary hydrogenation reactor. Over a cobalt-molybdenum hydrogenation catalyst, organic sulfur reacts with hydrogen to convert it to inorganic sulfur. After hydroconversion, zinc oxide desulfurizer is used to remove the total sulfur content in the converted gas to less than 0.1 ppm. The gas then enters the methane upgrading unit 4.

[0043] In this embodiment, the gas undergoing hydrogenation is relatively clean and has a low organic sulfur content, so only one stage of hydrogenation is required. Two fine desulfurization towers are used, which can be connected in parallel or in series. If necessary, a one-stage hydrogenation can be connected in series with a two-stage hydrogenation.

[0044] The methane upgrading unit 4 includes a methanation reactor, a cooler, and a gas-liquid separator. Deacidified gas from the hydrodesulfurization unit 14 enters the methanation reactor, where, under the action of a catalyst, CO and CO₂ are converted into methane. The methane upgraded outlet gas exchanges heat with decarbonized gas from the acid removal unit, preheating the decarbonized gas entering the hydrogenation reactor. The gas is then cooled to below 40°C in a cooler before entering the hydrogen recovery and purification unit 5.

[0045] In this embodiment, an adiabatic methanation process is adopted, the methanation reaction temperature is 250-350°C, and the reaction pressure is 1.75 MPa.G. The methane content of the gas at the outlet of the methane upgrading unit is about 22.31%, and the hydrogen content is about 75.05%.

[0046] The hydrogen recycling and purification unit 5 comprises a sequentially connected feed gas and recycled tail gas mixing tank, a hydrogen purification adsorption tower, and a recycled tail gas mixing tank. The PSA utilizes an eight-tower flushing process, including adsorption, pressure equalization and reduction, forward discharge, reverse discharge, flushing, pressure equalization and boosting, and final boosting. The hydrogen-rich gas, after methane upgrading, reaches a pressure of approximately 1.7 MPa.G. After mixing with hydrogen and recycled methane gas from the methane recycling and purification unit 6 in the feed gas and recycled tail gas mixing tank, it enters the adsorption tower at the bottom of the tower, where it is currently in the adsorption state. Through the sequential selective adsorption of multiple adsorbents, impurities are adsorbed, and the unadsorbed hydrogen flows out of the tower as product, resulting in high-purity hydrogen with a purity exceeding 99.999% (CO ≤ 0.2 ppm, CO2 ≤ 2 ppm) and a pressure exceeding 1.6 MPa.G, meeting the hydrogen requirements for fuel cell vehicles. After the regeneration steps of inversion and flushing, the regenerated tail gas rich in methane (the regeneration and regeneration gas pressure is 0.05-0.02MPa) is obtained and mixed and buffered in the circulating tail gas mixing tank before being recycled and purified to the methane unit 6.

[0047] In this example, the composition of the feed gas entering 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. A combined adsorption bed of activated alumina, silica gel, activated carbon, and 5A molecular sieve is required.

[0048] The methane recycling and purification unit 6 includes a screw compressor 15, a circulating membrane separation device 16, and a reciprocating compressor 17, wherein the screw compressor 15, the circulating membrane separation device 16, and the reciprocating compressor 17 are sequentially connected. Furthermore, the regenerated tail gas from the hydrogen recycling and purification unit 5 is pressurized to 1.1 MPa.G by the screw compressor 15 before entering the circulating membrane separation device 16. It is first filtered and then heated to 50°C before undergoing circulating membrane separation, where H2 and CH4 are separated and purified. The membrane retentate gas side produces a 1.0 MPa.G product biogas with a CH4 content of ≥85%vol and an H2 content of approximately 5%. The H2 concentration on the membrane permeate side can be increased from 36% to over 79%.

[0049] The permeate gas contains 79.8% hydrogen and 16.62% methane, which can be recycled. The hydrogen- and methane-rich membrane permeate gas 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. The hydrogen and methane are recycled to increase the production of high-purity hydrogen and biogas products.

[0050] In this example, the hydrogen recovery rate reached 96.5%, and the methane recovery rate reached 98.5%, both of which were higher than the recovery rates of existing processes.

[0051] Example 2

[0052] Based on the aforementioned raw biogas conditions, this example differs from Example 1 in that the CO conversion rate is adjusted in the carbon-hydrogen adjustment unit to achieve an optimal CO-to-H2 ratio, and the methane upgrading unit converts all CO to methane to increase methane production and quality. Through control in the carbon-hydrogen adjustment unit and methane upgrading unit, the maximum biogas production and hydrogen by-product are achieved, resulting in an annual output of 1,100 tons of 99.999% high-purity hydrogen and 77,000 tons of biogas.

[0053] Specifically, the purification unit 1 in this embodiment is the same as that in embodiment 1, and the macromolecular hydrocarbon compounds in the crude synthesis gas are removed to ≤5mg / Nm 3 , H2S is removed to ≤50mg / Nm 3 , obtaining purified synthesis gas and by-product sulfur.

[0054] In this embodiment, in order to achieve the maximum biogas production, the carbon-hydrogen regulation unit 2 controls the CO content in the unit outlet gas to about 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%.

[0055] The acid removal unit 3 in this embodiment is the same as that in Example 1, and uses zinc oxide desulfurizer to remove the total sulfur content in the conversion gas to less than 0.1 ppm. The removed CO2 is subsequently treated to obtain a by-product CO2 with a purity of 98%, which can be used to synthesize urea and produce industrial-grade or food-grade CO2.

[0056] Methane upgrading unit 4 In this embodiment, an adiabatic methanation process is adopted, the methanation reaction temperature is 250-450°C, the reaction pressure is 1.75 MPa.G, and the methane content of the methane upgrading unit outlet gas is about 83.90%, and the hydrogen content is about 11.04%.

[0057] The hydrogen recycling and purification unit 5 utilizes a seven-tower flushing PSA process. Further, the methane-rich gas, after methane upgrading, reaches a pressure of approximately 1.7 MPa.G. It is mixed with hydrogen and recycled methane gas from the methane recycling and purification unit 6 in a feed gas buffer tank before entering the adsorption tower at the bottom of the tower, where it is currently in the adsorption state. Through the sequential selective adsorption of multiple adsorbents, non-hydrogen gases such as methane and nitrogen are adsorbed, while the unadsorbed hydrogen flows out of the tower as the product, resulting in high-purity hydrogen with a purity exceeding 99.999% (CO ≤ 0.2 ppm, CO₂ ≤ 2 ppm) and a pressure exceeding 1.6 MPa.G, meeting the requirements for hydrogen used in fuel cell vehicles. After regeneration steps such as reversal and flushing, the methane-rich regenerated tail gas (regeneration and regeneration gas pressures are 0.05-0.02 MPa) is recycled to the methane recycling and purification unit 6.

[0058] In this example, the raw gas composition entering this 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 and 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.

[0059] The regenerated tail gas from the hydrogen recycling and purification unit 5 is pressurized to 1.1 MPa.G by screw compressor 15 before entering the circulating membrane separation unit 16. It is first filtered and then heated to 50°C before undergoing a circulating membrane separation process, where hydrogen and methane are separated and purified. The membrane retentate gas produces a 1.0 MPa.G product biogas with a CH4 content of ≥94.27%. The hydrogen concentration on the membrane permeate side can be increased from 5.32% to over 28.61%. The permeate gas contains 28.61% hydrogen and 64.37% methane, respectively, and can be recycled. The hydrogen- and methane-rich membrane permeate gas 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, where hydrogen and methane are recycled to increase the yield of high-purity hydrogen and biogas products. This step is a key feature of this process system.

[0060] The amount of membrane permeate gas rich in hydrogen and methane in this embodiment is half of that in embodiment 1. The membrane permeate gas rich in hydrogen and methane can also be recovered after being pressurized by the centrifugal compressor 11 .

[0061] The beneficial effects of the present invention are as follows:

[0062] Biomass syngas is a new green and environmentally friendly raw material for hydrogen production. This process produces hydrogen with a purity of 99.999%. The purity and impurity content of the hydrogen meet the technical requirements for high-purity hydrogen in GBT 3634.2-2011 Hydrogen Part 2 and the technical requirements for hydrogen fuel for proton exchange membrane fuel cell vehicles in GB / T 37244-2018, resulting in higher quality and value of the hydrogen.

[0063] This process system co-generates biogas, producing bionatural gas of a quality that meets the technical requirements for Class II biogas in the Biogas standard GB / T41328-2022. The effective components in the biogas, such as hydrogen, methane, and carbon monoxide, are fully utilized and recovered, increasing product value and reducing energy waste.

[0064] The regenerated tail gas generated by the hydrogen recovery and purification unit is recycled to the methane recovery and purification unit. The permeate gas, rich in hydrogen and methane, from the permeate side of the membrane separation process is then returned to the inlet of the hydrogen recovery and purification unit 5. Throughout this process, all hydrogen- and methane-rich tail gas, except for the product, is recycled and reused. When the product hydrogen purity reaches 99.999% and the methane quality meets Class II biogas standards, the hydrogen recovery rate reaches 96.5% and the methane recovery rate reaches 98.5%, exceeding those of existing processes. This results in higher hydrogen and biogas yields and a more efficient utilization of the crude biosyngas.

[0065] The production of high-purity hydrogen and biogas can be adjusted based on market conditions. When high-purity hydrogen prices are high, the carbon monoxide in the crude syngas can be completely converted into hydrogen in the hydrogen upgrading section of the carbon-hydrogen regulation section to increase hydrogen production. When high-purity hydrogen prices are low, a small portion of the carbon monoxide in the crude syngas can be converted into hydrogen in the carbon-hydrogen regulation section, while the remaining carbon monoxide is converted into methane in the methane upgrading section to increase biogas production. The ability to adjust high-purity hydrogen and biogas production based on market prices enhances the company's risk mitigation capabilities and facilitates the industrialization of crude biogas utilization.

[0066] Improve the deep processing and utilization value of bio-crude synthesis gas. All carbon monoxide, hydrogen and methane in the bio-crude synthesis gas are recovered. At the same time, sulfur and carbon dioxide with a purity greater than 98% (V%) are produced as by-products. After deep processing, each component in the gas is recovered and the corresponding products are obtained, fully exploring and maximizing the value of bio-crude synthesis gas.

[0067] In summary, the present invention utilizes multiple units for cyclic utilization. First, through purification, carbon-hydrogen regulation, acid removal, and methane upgrading, it achieves deep processing of the raw gas and regeneration of hydrogen and methane. Furthermore, through purification processes, high-purity hydrogen is extracted and recycled to increase hydrogen output. Biogas is further purified through circulating membrane separation technology, and recycled through a compressor to increase biogas output.

[0068] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any technician familiar with the present profession can make slight changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications 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 are still within the scope of the technical solution of the present invention.

Claims

1. A process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas, characterized in that: It comprises a purification unit (1), a hydrocarbon adjustment unit (2), an acid removal unit (3), a methane upgrading unit (4), a recycling and purification unit for hydrogen (5), and a recycling and purification unit for methane (6), which are connected in sequence. The purification unit (1) is used to perform pre-impurity removal, preliminary compression, further impurity removal and desulfurization on the bio-crude synthesis gas entering the process system to obtain purified synthesis gas and by-product sulfur; the carbon-hydrogen adjustment unit (2) is used to pressurize the purified synthesis gas and adjust the content of hydrogen in the purified synthesis gas and the content of methane in the methane upgrading unit (4) to obtain carbon-hydrogen regulated gas; the acid removal unit (3) is used to remove acid gas from the carbon-hydrogen regulated gas to obtain acid degassing and by-product CO2; the methane upgrading unit (4) is used to perform a methanation reaction on the acid degassing to convert CO and CO2 in the acid degassing into methane, and to incrementally increase the methane in the purified synthesis gas. The circulating recovery and purification hydrogen unit (5) is used to circulate and recover the mixed gas, and at the same time, purify the hydrogen by a pressure swing adsorption process to obtain product hydrogen and methane circulating recovery gas; the circulating recovery and purification methane unit (6) includes a screw compressor (15), a circulating membrane separation device (16) and a reciprocating compressor (17), which is used to pressurize and separate the methane circulating recovery gas to obtain product biogas, hydrogen and methane circulating recovery gas. The hydrogen and methane circulating recovery gas are pressurized by the reciprocating compressor (17) and then return to the carbon-hydrogen adjustment unit (2) or enter the circulating recovery and purification hydrogen unit (5), and the pressure swing adsorption regeneration pressure is controlled at 0.02-0.05 MPa.

2. The process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas according to claim 1, characterized in that: The purification unit (1) comprises a pre-impurity removal device (7), a blower (8), a dry impurity removal device (9) and a wet desulfurization device (10) which are connected in sequence: the pre-impurity removal device (7) is used to pre-impurify the macromolecular hydrocarbon compound impurities in the crude biosynthesis gas to obtain pre-impurity-removed gas; the blower (8) is used to preliminarily pressurize the pre-impurity-removed gas to obtain a primary compressed gas; the dry impurity removal device (9) is used to further remove the macromolecular hydrocarbon compounds in the primary compressed gas to obtain a secondary impurity-removed gas; the wet desulfurization device (10) is used to remove inorganic sulfur in the secondary impurity-removed gas, and finally obtain purified synthesis gas and by-product sulfur.

3. The process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas according to claim 1, characterized in that: The carbon-hydrogen regulating unit (2) comprises a centrifugal compressor (11) and a hydrogen upgrading device (12) connected in sequence; wherein the centrifugal compressor (11) is used to perform secondary pressurization on the purified synthesis gas to obtain secondary compressed gas, and 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; wherein the hydrogen upgrading device (12) comprises a detoxification furnace, a humidifier and a conversion furnace connected in sequence.

4. The process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas according to claim 1, characterized in that: The acid removal unit (3) comprises an acid removal device (13) and a hydrodesulfurization device (14) which are connected in sequence; the acid removal device (13) is used to remove hydrogen sulfide and CO2 in the hydrocarbon adjustment gas to obtain by-product CO2, and the hydrodesulfurization device (14) is used to hydrogenate the organic sulfur and olefins in the hydrocarbon adjustment gas with hydrogen to convert the organic sulfur into inorganic sulfur to obtain acid degassing; wherein the acid removal device (13) comprises an absorption tower, a flash tower, a stripping regeneration tower and a flash gas decarbonization tower.

5. The process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas according to claim 1, characterized in that: The methane upgrading unit (4) adopts a methanation reactor, which is used to convert CO and CO2 in the acid degassing into methane, and the reaction temperature is 250-450°C.

6. The process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas according to claim 1, characterized in that: The circulating recovery and purification hydrogen unit (5) comprises a raw gas and circulating recovery tail gas mixing tank, a purified hydrogen adsorption tower group and a circulating tail gas mixing tank connected in sequence, and is used to purify hydrogen and obtain product hydrogen and methane circulating recovery gas.

7. The process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas according to any one of claims 1 to 6, characterized in that: The process system for producing hydrogen and co-producing bio-natural gas by using the bio-crude synthesis gas comprises the following steps: S1: The bio-crude synthesis gas is sequentially passed through a pre-impurity removal device (7), a blower (8), a dry impurity removal device (9) and a wet desulfurization device (10) to remove macromolecular hydrocarbon compounds and inorganic sulfur impurities, thereby obtaining purified synthesis gas and by-product sulfur; S2: The purified synthesis gas is pressurized for a second time to 1.5-2.5 MPa, and the hydrogen and carbon monoxide contents in the gas are adjusted by a shift reaction, and the CO content at the shift outlet is controlled to be 0.8%-13.69%, thereby obtaining a hydrocarbon-adjusted gas; S3: sequentially performing acid gas removal and hydrofining desulfurization on the hydrocarbon-adjusted gas to remove hydrogen sulfide, CO2 and organic sulfur to obtain acid degassing and by-product CO2; S4: passing the degassed acid into a methanation reactor, performing a methanation reaction at 250-450° C. and 1.5-2.0 MPa to convert CO and CO2 into methane to obtain a mixed gas containing hydrogen and methane; S5: Purifying the mixed gas with hydrogen using a pressure swing adsorption process to obtain product hydrogen with a purity of ≥99.999% and methane-rich methane recycling gas; S6: The methane recycled gas is sequentially passed through a screw compressor (15), a circulating membrane separation device (16) and a reciprocating compressor (17) to separate the product biogas, hydrogen and methane recycled gas; the hydrogen and methane recycled gas are pressurized to 1.5-2.5 MPa by the reciprocating compressor (17) and then returned to step S2 for carbon-hydrogen adjustment or pressurized and then enter step S5 for recycling and hydrogen purification.

8. The process system for producing hydrogen from bio-crude synthesis gas and co-producing bio-natural gas according to claim 7, characterized in that: In step S5, pressure swing adsorption is performed using a composite adsorbent of 5A molecular sieve and activated carbon.

Images