Biogas catalytic reforming and membrane separation coupled hydrogen production system and hydrogen production process

Abstract

The invention discloses a methane catalytic reforming and membrane separation coupled hydrogen production system and a hydrogen production process, and belongs to the field of renewable energy utilization. The system comprises a multi-stage desulfurization subsystem, a low-temperature catalytic reforming reactor, a membrane separation-pressure swing adsorption (PSA) coupling device and a preheating and heat exchange device which are communicated in sequence. The multi-stage desulfurization subsystem adopts a three-stage design of biological desulfurization, adsorption desulfurization and deep desulfurization, and the sulfur content of biogas is reduced to be less than 0.1 ppm; the low-temperature catalytic reforming reactor adopts a Ru-Ni / CeZrO2 bifunctional catalyst, and efficient reforming of the biogas is realized at 450-600 DEG C; the membrane separation-PSA coupling device realizes that the purity of hydrogen is greater than or equal to 99.99% and the recovery rate is high; the heat exchange device recovers waste heat and reduces energy consumption. The problems of catalyst poisoning, high energy consumption, large carbon emission and low efficiency in the prior art are solved, the energy consumption of the system is reduced by 40%, the CO2 emission is reduced by more than 35%, the service life of the catalyst reaches 8000 hours, and the method is suitable for industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of efficient utilization of renewable energy and hydrogen production technology, in particular to a biogas catalytic reforming and membrane separation coupled hydrogen production system and hydrogen production process, which realizes efficient, low-carbon and low-cost hydrogen production from biogas by integrating multi-stage deep desulfurization, low-temperature catalytic reforming, membrane separation-pressure swing adsorption coupled separation technology, and is suitable for large-scale biogas treatment and hydrogen production scenarios. BACKGROUND

[0002] With the transformation of global energy structure to low carbonization, efficient utilization of renewable energy has become a key development direction. Biogas, as an important biomass energy, is mainly derived from the anaerobic fermentation of livestock and poultry breeding waste, agricultural straw, municipal sludge, etc. Its main components are methane (CH4, content usually 50%-70%) and carbon dioxide (CO2, content usually 30%-50%), and it also contains a small amount of hydrogen sulfide (H2S, content 50-3000 ppm), water vapor and trace organic impurities. The rational use of biogas not only realizes the resource utilization of waste, but also reduces greenhouse gas emissions, with significant economic and environmental benefits. However, there are still many problems to be solved in the existing biogas utilization and hydrogen production technology: 1. Traditional biogas utilization has low energy grade and serious pollution At present, the traditional biogas utilization is mainly direct combustion, which is mostly used for cooking, heating or small internal combustion engine group power generation in rural areas. This utilization method has obvious defects: on the one hand, the energy density of methane is high (low heat value about 35 MJ / m³), and direct combustion can only convert its energy into low-grade heat or low-efficiency electricity, with an energy conversion efficiency usually <30%, and a large amount of high-quality energy is wasted; on the other hand, H2S in biogas will generate sulfur dioxide (SO2) in the combustion process, which is one of the main pollutants causing acid rain, causing damage to the atmospheric environment and ecological system.

[0003] 2. The existing hydrogen production process has high energy consumption and large carbon emissions The mainstream technology of industrial hydrogen production is natural gas steam reforming hydrogen production, which accounts for more than 75% of global hydrogen production. However, this process has two major problems: one is high energy consumption, natural gas steam reforming needs to be carried out at a high temperature of 850-950℃, in order to maintain a high-temperature reaction environment, a large amount of natural gas needs to be consumed as fuel (about 30%-40% of the total amount of raw natural gas), resulting in high energy consumption in the hydrogen production process; the second is high carbon emission, the methane reforming reaction (CH4+H2O CO+3H2) and the subsequent water-gas shift reaction (CO+H2O The existing process generates a large amount of CO2, about 10-12 kg of CO2 is emitted per 1 kg of hydrogen produced, which is much higher than the requirement of low-carbon development and is difficult to meet the energy production demand under the "double carbon" target.

[0004] For biogas hydrogen production, the existing technology mostly follows the process route of natural gas reforming, which is not optimized for the composition characteristics of biogas (containing H2S and high CO2 content). Not only does it require high-temperature reaction conditions, but the energy consumption problem has not been solved, and because the CH4 content in biogas is lower than that in natural gas (usually 10%-20% lower), the raw material consumption per unit of hydrogen production is higher, further increasing energy consumption and cost.

[0005] 3. H2S in biogas causes catalyst poisoning, and existing desulfurization technology is ineffective The H2S contained in biogas is a "fatal flaw" in the catalytic reforming process - H2S can cause severe poisoning of the reforming catalyst, which is a core technical bottleneck for biogas hydrogen production.

[0006] Existing biogas desulfurization technologies are mostly single desulfurization processes, which cannot meet the stringent requirements of catalysts for sulfur content (usually <0.1 ppm). The limitations of single desulfurization technology make it difficult to reduce the sulfur content in biogas to the tolerance range of the catalyst, and the service life of the catalyst is usually only 1000-2000 hours, which requires frequent replacement, significantly increasing the operation and maintenance cost of biogas hydrogen production and limiting its industrial application.

[0007] 4. Hydrogen separation link is independent, system efficiency is low In the existing hydrogen production system, the catalytic reforming and hydrogen separation and purification links are independent of each other, and there is a lack of effective coupling design, resulting in low overall system efficiency: Single separation technology: existing hydrogen separation mostly uses single pressure swing adsorption (PSA) or membrane separation technology. Single PSA technology can obtain high-purity hydrogen of more than 99.99%, but the adsorption-desorption cycle is long (usually 10-15 minutes), the hydrogen recovery rate in the tail gas is only 85%-90%, and the energy consumption is high; single membrane separation technology (such as Pd-based membrane) has the advantages of continuous separation and low energy consumption, but is limited by membrane permeation rate and separation selectivity, making it difficult to deal with high-concentration CO2 (30%-40% content) in the reforming mixed gas, which easily leads to membrane contamination, and the final hydrogen purity is difficult to stabilize at 99.99%; Severe energy loss: the mixed gas after reforming reaction has a temperature of 450-600℃, in the existing system, the high-temperature gas directly enters the normal-temperature separation device, and a large amount of heat is discharged through the cooler without being effectively recovered; Low system integration: desulfurization, reforming and separation are independent, and there are pressure loss and material leakage risk in the intermediate material transmission process, which further reduces the stability and efficiency of the system.

[0008] In summary, the existing biogas utilization and hydrogen production technology has the problems of low energy grade, high energy consumption, large carbon emission, catalyst poisoning, and low system efficiency. Therefore, it is urgent to develop an integrated hydrogen production system and method which integrates deep desulfurization, low-temperature reforming and efficient coupling separation, to realize efficient, low-carbon and low-cost hydrogen production from biogas. SUMMARY

[0009] Based on the above background technology, the present application aims to solve the following core technical problems: how to achieve deep removal of H2S in biogas, reduce the reaction temperature and energy consumption of catalytic reforming, realize integrated design of catalytic reforming and hydrogen separation, and obtain an integrated hydrogen production system and method which integrates deep desulfurization, low-temperature reforming and efficient coupling separation.

[0010] To solve the above technical problems, the first technical solution provided by the present application is a biogas catalytic reforming and membrane separation coupling hydrogen production system, which comprises a multi-stage desulfurization subsystem, a low-temperature catalytic reforming reactor and a membrane separation-PSA (pressure swing adsorption) coupling device connected in sequence, and further comprises a preheating device and a heat exchange device.

[0011] Further, the multi-stage desulfurization subsystem comprises a biological desulfurization tower, an adsorption desulfurization device and a deep desulfurization reactor connected in sequence along the flow direction of biogas.

[0012] Further, the low-temperature catalytic reforming reactor is provided with a Ru-Ni / CeZrO2 bifunctional catalyst bed, and further comprises a heating device and a temperature control device.

[0013] Further, the membrane separation-PSA coupling device comprises a Pd-Ag alloy hollow fiber membrane assembly and a PSA tail gas recovery device.

[0014] Further, the preheating device is used to preheat the raw biogas to 80-120℃ before entering the multi-stage desulfurization subsystem; one end of the heat exchange device is connected with the mixed gas outlet of the low-temperature catalytic reforming reactor, and the other end is connected with the outlet of the preheating device or the multi-stage desulfurization subsystem, which is used to recover the heat of the high-temperature mixed gas after reforming.

[0015] Further, the biological desulfurization tower is filled with a sulfur-oxidizing bacteria bed layer, the operating temperature is 25-35℃, the pH value is 7.0-8.5, and the biogas residence time in the tower is 15-30min; the adsorption desulfurization device is filled with a Fe2O3 / ZnO composite adsorbent, the mass ratio of Fe2O3 to ZnO is 1:1-3, the operating pressure is 0.5-1.0MPa, and the operating temperature is 30-50℃; and the deep desulfurization reactor is filled with a Ni-Mo / Al2O3 catalyst, the loading amount of Ni is 2-5wt%, the loading amount of Mo is 1-3wt%, the operating temperature is 200-300℃, and the operating pressure is 0.5-1.0MPa.

[0016] Further, in the bifunctional catalyst, the loading amount of Ru is 0.5-2wt%, the loading amount of Ni is 1-5wt%, the carrier is a CeZrO2 solid solution (the molar ratio of Ce to Zr is 1:1-2), and 0.5-2wt% of K2O is added as an additive; the operating temperature of the reactor is controlled at 450-600℃, and the operating pressure is controlled at 1.5-2.5MPa.

[0017] Further, in the Pd-Ag alloy hollow fiber membrane, the content of Ag is 23-28wt%, the H2 permeation rate of the membrane module is >20m³ / m²·h, the operating temperature is 300-400℃, and the operating pressure is 1.0-2.0MPa; the PSA tail gas recovery device is filled with a molecular sieve adsorbent, the adsorption pressure is 0.8-1.5MPa, the desorption pressure is 0.05-0.1MPa, and the adsorption-desorption cycle is 5-10min.

[0018] Further, in the sulfur-oxidizing bacteria bed layer of the biological desulfurization tower, the sulfur-oxidizing bacteria are a mixed bacteria agent of Acidithiobacillus ferroxidans and Thiobacillus thioparus, and the bacteria amount ratio of the two is 1:1-2; the adsorption desulfurization device is provided with an adsorbent regeneration mechanism, and the Fe2O3 / ZnO composite adsorbent can be regenerated at 300-350℃ under the condition of air inlet.

[0019] Further, the catalyst bed of the low-temperature catalytic reforming reactor is divided into two sections, the upper section is a catalyst pre-activation zone, and the lower section is a main reaction zone; the heating device is an electric heating pipe or a heat conduction oil heating jacket, and the temperature control precision of the temperature control device is ±5℃.

[0020] Further, the preparation method of the Ru-Ni / CeZrO2 bifunctional catalyst is as follows: Step S1: dissolving Ru(NO3)3, Ni(NO3)2·6H2O, Ce(NO3)3·6H2O and ZrO(NO3)2·xH2O in deionized water to obtain a mixture solution; Step S2: adding the mixture solution into 600 mL deionized water at 70℃, and then stirring the deionized water at 1100 rpm; Step S3: adding a Na2CO3 solution to the mixture solution to adjust the pH value of the mixture solution to 10, and then continuously stirring the mixture solution for 1 hour; Step S4: filtering the mixture solution to obtain a precipitate, and then washing the precipitate with deionized water; Step S5: drying the precipitate at a drying temperature of 105℃, and then crushing the precipitate; Step S6: placing the crushed precipitate in a calcination furnace, and then calcining the precipitate by passing 30 mL / min of N2 gas into the calcination furnace at 600℃ for 1 hour; subsequently, re-calcining the precipitate by passing 30 mL / min of air into the calcination furnace at 600℃ for 30 minutes; Step S7: obtaining a bifunctional catalyst Ru-Ni / CeZrO2 composed of a CeZrO2 carrier and Ru, Ni active metals.

[0021] The hydrogen production system of the present application takes "deep desulfurization - low-temperature reforming - coupling separation - energy recovery" as the core architecture, including a multi-stage desulfurization subsystem, a low-temperature catalytic reforming reactor, a membrane separation-PSA coupling device, and auxiliary components such as a preheating device and a heat exchange device, which work together to achieve efficient hydrogen production from biogas.

[0022] The multi-stage desulfurization subsystem adopts a three-stage progressive design of "biological desulfurization -> adsorption desulfurization -> deep desulfurization", which realizes deep removal in stages according to different forms and contents of H2S in biogas. The specific structure and parameters are as follows: Bio-desulfurization tower (primary desulfurization): As a rough desulfurization unit, it mainly removes 80%-90% of H2S in biogas. The tower is filled with a bed of sulfur-oxidizing bacteria, and the mixed bacteria (bacteria ratio 1:1-2) of Acidithiobacillus ferrooxidans and Thiobacillus thioparus are selected. The mixed bacteria have both acid and sulfur tolerance, and can efficiently oxidize H2S under the conditions of 25-35℃ and pH 7.0-8.5. The reaction formula is: H2S + 2O2→H2SO4 or 2H2S + O2→ 2S↓ + 2H2O. Biogas stays in the tower for 15-30min, and the H2S content can be reduced from 50-3000ppm to 5-10ppm, laying a foundation for subsequent deep desulfurization.

[0023] Adsorption desulfurization device (secondary desulfurization): As a fine desulfurization unit, it further removes residual H2S. The device is filled with Fe2O3 / ZnO composite adsorbent (Fe2O3 / ZnO mass ratio 1:1-3), which removes H2S through physical and chemical adsorption synergy: Fe2O3 reacts with H2S to form Fe2S3 (Fe2O3+ 3H2S = Fe2S3+ 3H2O), and ZnO reacts with H2S to form ZnS (ZnO + H2S = ZnS + H2O). The adsorbent works at 0.5-1.0MPa and 30-50℃, and can reduce the H2S content from 5-10ppm to 0.5-1ppm; the device is also equipped with an adsorbent regeneration mechanism. When the adsorbent is saturated, air is introduced at 300-350℃, and Fe2S3 and ZnS can be oxidized to Fe2O3 and ZnO to regenerate the adsorbent (Fe2S3 + 3O2 = Fe2O3 + 3SO2↑, 2ZnS + 3O2 = 2ZnO + 2SO2↑), extending the service life of the adsorbent.

[0024] Deep desulfurization reactor (third-stage desulfurization): As a super-precise desulfurization unit, the target of <0.1 ppm of sulfur content is achieved. The reactor is filled with Ni-Mo / Al2O3 catalyst (Ni loading 2-5wt%, Mo loading 1-3wt%), which has excellent hydrodesulfurization activity and can convert trace amounts of H2S and organic sulfur (such as CS2 and CH3SH) in biogas into easily removable substances: organic sulfur is converted into H2S under hydrogenation (such as CS2+4H2→CH4+2H2S), and H2S is adsorbed and fixed by reacting with the active components on the surface of the catalyst. The reactor operates at 200-300℃ and 0.5-1.0MPa, ensuring that the sulfur content of biogas entering the reforming reactor is <0.1ppm, and completely avoiding catalyst poisoning.

[0025] Low-temperature catalytic reforming reactor is the core unit for efficient conversion of biogas. By developing Ru-Ni / CeZrO2 bifunctional catalyst, efficient reforming of CH4 is achieved at medium and low temperatures. The specific design is as follows: Catalyst system: Ru-Ni bimetallic active components + CeZrO2 carrier + K2O additive composite system, the synergistic effect of each component improves the catalytic performance.

[0026] Active components: Ru (loading 0.5-2wt%) and Ni (loading 1-5wt%) form an alloy structure. Ru has excellent CH4 activation ability and can break the C-H bond at low temperature. Ni can promote the water-gas shift reaction and improve H2 selectivity. The synergistic effect of bimetallic reduces the reaction activation energy, so that the reforming reaction can be carried out at 450-600℃; Carrier: CeZrO2 solid solution (molar ratio of Ce to Zr 1:1-2) has good oxygen storage and release capacity (Ce 4+ can be reversibly converted to Ce 3+ ), which can oxidize CO by releasing oxygen (CO + O → CO2), further improving H2 selectivity and inhibiting the formation of carbon deposits; Additive: K2O (addition amount 0.5-2wt%) can adjust the surface acidity of the catalyst, reduce the adsorption of CO2 on acid sites, avoid carbon deposition (carbon deposition is easy to generate on acid sites), and enhance the sulfur resistance of the catalyst.

[0027] Reactor structure: The reactor shell is made of high-temperature-resistant stainless steel, and has two-stage catalyst bed inside: the upper stage is a catalyst pre-activation zone (filled with a small amount of catalyst), which is used to preheat the reactants and activate the catalyst; the lower stage is the main reaction zone (filled with most of the catalyst), which is the main place for reforming reaction. The reactor is equipped with heating devices (electric heating pipes or heat conduction oil heating jackets) and temperature control devices (temperature control accuracy ±5°C) on the outside, which can accurately control the reaction temperature at 450-600°C; the reactor is also equipped with pressure control valves to ensure that the reaction pressure is stable at 1.5-2.5 MPa, which improves the reaction rate and CH4 conversion rate.

[0028] Membrane separation-PSA coupling device adopts the coupling design of "membrane separation preliminary separation + PSA tail gas recovery", which takes into account hydrogen purity and recovery rate, and the specific structure is as follows: Pd-Ag alloy hollow fiber membrane module (preliminary separation): Pd-Ag alloy membrane has excellent selectivity for H2 (separation factor of H2 from other gases >1000), and hollow fiber structure greatly increases the membrane area (specific surface area >1000 m² / m³), which improves the H2 permeation rate (>20 m³ / m²·h). The content of Ag in the membrane module is 23-28wt% (the flexibility and H2 permeation performance of the membrane are best at this ratio), the operating temperature is 300-400°C (utilizing the waste heat of reforming mixed gas, no additional heating is needed), the operating pressure is 1.0-2.0 MPa, the permeation side pressure is 0.1-0.2 MPa, and H2 is driven to permeate by pressure difference. After membrane separation, crude hydrogen with a purity of ≥99.9% can be obtained, and the H2 content in the mixed gas is reduced from 70%-75% to 10%-15% (tail gas).

[0029] PSA tail gas recovery device (deep recovery): For the residual H2 in the membrane separation tail gas, PSA technology is used for further recovery. The device is filled with 13X molecular sieve adsorbent, which has much higher adsorption capacity for CO2 and CO than for H2. Under an adsorption pressure of 0.8-1.5 MPa, the adsorbent selectively adsorbs CO2 and CO, and H2 as a non-adsorbed component is directly discharged and mixed with the crude hydrogen from membrane separation; under a desorption pressure of 0.05-0.1 MPa, the adsorbent desorbs CO2 and CO, completing regeneration. The adsorption-desorption cycle is 5-10 min, which can improve the H2 recovery rate in the tail gas to more than 95%, and the final hydrogen purity is ≥99.99%.

[0030] Preheating device: electric heating or waste heat heating is used to preheat the raw material biogas to 80-120°C, reducing the energy consumption of subsequent desulfurization and reforming processes, and removing part of the water vapor in the biogas.

[0031] Heat exchange device: adopt shell and tube heat exchanger, one end connects the mixed gas outlet of reforming reactor (temperature 450-600 DEG C), the other end connects the biogas import after deep desulfurization, the heat of high temperature mixed gas is used to preheat the desulfurized biogas to 300-400 DEG C, and then into the reforming reactor.The design can recover about 60%-70% of the residual heat of reforming, greatly reduce the energy consumption of system, and improve the overall efficiency.

[0032] The second technical scheme provided by the application is a hydrogen production process based on the hydrogen production system, comprising the following steps: S1: biogas pretreatment-multistage desulfurization (1) the raw biogas is preheated to 80-120 DEG C by a preheating device, and then enters a biological desulfurization tower, under the action of sulfur-oxidizing bacteria, H2S is oxidized into elemental sulfur or sulfate, H2S is preliminarily removed, and the content of H2S in the biogas is reduced to 5-10 ppm.

[0033] This step is a primary biological desulfurization: the raw biogas (typical components: CH4 45%-70%, CO2 30%-50%, H2S 50-3000 ppm) is preheated to 80-120 DEG C by a preheating device, and then enters a biological desulfurization tower. The temperature in the tower is controlled at 25-35 DEG C, the pH value is adjusted to 7.0-8.5, and the residence time of the biogas is 15-30 min. Under the action of sulfur-oxidizing bacteria, H2S is oxidized into elemental sulfur or sulfate, and the content of H2S in the desulfurized biogas is reduced to 5-10 ppm. The generated elemental sulfur is collected by precipitation and can be used as an industrial raw material; the sulfate is discharged with waste water and treated to meet the discharge standard.

[0034] (2) the biologically desulfurized biogas is introduced into an adsorption desulfurization device, and under the action of Fe2O3 / ZnO composite adsorbent, H2S is further removed, so that the content of H2S in the biogas is reduced to 0.5-1 ppm.

[0035] This step is a secondary adsorption desulfurization: the biologically desulfurized biogas is introduced into an adsorption desulfurization device, the pressure of the device is controlled at 0.5-1.0 MPa, and the temperature is controlled at 30-50 DEG C. The biogas stays in the Fe2O3 / ZnO composite adsorbent bed for 5-10 min, H2S reacts with the adsorbent to further remove H2S, so that the content of H2S in the biogas is reduced to 0.5-1 ppm. When the adsorbent is saturated (monitored by an online sulfur content detector), switch to the regeneration mode: introduce 300-350 DEG C air, and the regeneration time is 2-3 h. After the adsorbent recovers its activity, it is put into use again.

[0036] (3) The biogas after adsorption desulfurization is introduced into a deep desulfurization reactor, and residual H2S is deeply removed under the action of a Ni-Mo / Al2O3 catalyst, so that the sulfur content in the final biogas is less than 0.1 ppm.

[0037] This step is three-stage deep desulfurization: the biogas after adsorption desulfurization is introduced into a deep desulfurization reactor, the reactor temperature is controlled at 200-300 DEG C, the pressure is controlled at 0.5-1.0 MPa, and the biogas space velocity is controlled at 500-1000 h -1 Under the action of a Ni-Mo / Al2O3 catalyst, residual H2S and organic sulfur are converted into easily adsorbed substances by hydrodesulfurization, so that the sulfur content in the final biogas is less than 0.1 ppm, meeting the requirements of subsequent reforming catalysts.

[0038] S2: Low-temperature catalytic reforming The biogas after deep desulfurization in S1 is mixed with steam at a volume ratio of 1:2-4, preheated to 300-400 DEG C by a heat exchange device, and then introduced into a low-temperature catalytic reforming reactor to perform catalytic reforming reaction under the action of a Ru-Ni / CeZrO2 dual-function catalyst, and the reaction space velocity is 1000-3000 h -1 , to generate a mixed gas containing H2, CO2 and a small amount of CO, wherein the CH4 conversion rate is greater than or equal to 95%, and the H2 selectivity is greater than 90%.

[0039] Further, the temperature of the steam in S2 is 350-400 DEG C, and the pressure is consistent with the pressure of the biogas; the permeation side pressure of the membrane separation assembly in S3 is 0.1-0.2 MPa, and the pressure difference between the two sides of the membrane drives H2 permeation.

[0040] Firstly, the raw materials are mixed: the biogas after deep desulfurization is mixed with steam at a volume ratio of 1:2-4 (the temperature of the steam is 350-400 DEG C, and the pressure is consistent with that of the biogas), and the steam acts as an oxidant and a diluent, which can promote the CH4 reforming reaction (CH4+H2O CO+3H2), and at the same time inhibit the generation of carbon deposition.

[0041] Then, preheating and reaction are performed: the mixed raw materials are preheated to 300-400 DEG C by a heat exchange device (using the waste heat of the mixed gas after reforming), and then introduced into a low-temperature catalytic reforming reactor. The reactor temperature is controlled at 450-600 DEG C, the pressure is controlled at 1.5-2.5 MPa, and the reaction space velocity is controlled at 1000-3000 h -1 Under the action of a Ru-Ni / CeZrO2 dual-function catalyst, the following reactions occur: Main reaction: CH4+ H2O CO + 3H2 Side reaction (water gas shift): CO + H2O CO2 + H2 The main reaction produces H2 and CO, while the side reaction converts CO into CO2 and H2, ultimately producing a mixed gas containing H2 (70%-75%), CO2 (20%-25%), and a small amount of CO (<1%), with CH4 conversion ≥95% and H2 selectivity >90%.

[0042] S3: Hydrogen separation and purification The mixed gas generated in S2 is passed into the Pd-Ag alloy hollow fiber membrane module of the membrane separation-PSA coupling device. H2 selectively permeates through the membrane module to obtain crude hydrogen with a purity of ≥99.9%. The tail gas after membrane separation is fed into the PSA tail gas recovery unit. The adsorbent selectively adsorbs CO2 and CO, and H2 is desorbed and recovered. The recovered H2 is mixed with the crude hydrogen obtained from membrane separation to finally obtain hydrogen with a purity of ≥99.99%.

[0043] Preliminary membrane separation: The reformed high-temperature mixed gas (450-600℃) is first passed through a heat exchanger to release heat and preheat the feedstock. After the temperature drops to 300-400℃, it is then passed through a Pd-Ag alloy hollow fiber membrane module. The operating pressure of the membrane module is controlled at 1.0-2.0 MPa, and the pressure on the permeate side is controlled at 0.1-0.2 MPa. Driven by the pressure difference across the membrane, H2 permeates through the Pd-Ag membrane via a dissolution-diffusion mechanism to obtain crude hydrogen with a purity ≥99.9%. The unpermeated tail gas (containing 10%-15% H2, 80%-85% CO2, and a small amount of CO) enters the PSA tail gas recovery unit.

[0044] PSA tail gas recovery: The operating pressure of the PSA unit is controlled at 0.8-1.5 MPa (adsorption stage) and 0.05-0.1 MPa (desorption stage), with the adsorption-desorption cycle controlled at 5-10 min. During the adsorption stage, the 13X molecular sieve adsorbent selectively adsorbs CO2 and CO from the tail gas, while H2 is discharged as an unadsorbed component and mixed with the crude hydrogen separated by the membrane to obtain hydrogen with a purity ≥99.99%. During the desorption stage, the adsorbent desorbs CO2 and CO, and the desorbed tail gas (mainly containing CO2) enters the subsequent treatment stage.

[0045] S4: Energy Recovery The high-temperature mixed gas (450-600℃) after the catalytic reforming reaction in S2 is first passed into a heat exchanger to exchange heat with the biogas or raw biogas after deep desulfurization in S1. After releasing heat, it enters the membrane separation module to realize energy recovery and utilization.

[0046] Two energy recovery processes are achieved through a heat exchanger: first, the high-temperature mixed gas after reforming preheats the biogas after deep desulfurization, reducing the heating energy consumption of the reforming reactor; second, the mixed gas before membrane separation preheats the feedstock biogas, reducing the power consumption of the preheating device. Through energy recovery, the system's energy consumption is reduced by 40% compared to traditional steam reforming.

[0047] Furthermore, the above-mentioned hydrogen production process also includes a tail gas treatment step: the tail gas (mainly containing CO2) desorbed by the PSA tail gas recovery device in S3 is dried and purified, and can be used for food-grade CO2 production or injected underground for carbon sequestration.

[0048] The exhaust gas after PSA desorption (mainly containing CO2, with a purity of ≥95%) is dried (dehydrated to a water content of <10ppm) and purified (removing small amounts of CO and H2). It can then be used as food-grade CO2 (for carbonated beverages and food preservation) or industrial-grade CO2 (for welding protection and oilfield flooding). It can also be injected underground for carbon sequestration, realizing the resource utilization or emission reduction of CO2, reducing the system's CO2 emissions by more than 35% compared to existing technologies.

[0049] Furthermore, in S2, the operating temperature of the catalytic reforming reaction is controlled at 450-600℃, and the operating pressure is controlled at 1.5-2.5MPa; in S3, the operating temperature of the selective H2 permeation through the membrane module is 300-400℃, and the operating pressure is 1.0-2.0MPa; in S3, the adsorption pressure of the tail gas recovery device is 0.8-1.5MPa, the desorption pressure is 0.05-0.1MPa, and the adsorption-desorption cycle is 5-10min. Beneficial effects

[0050] (1) This invention is based on the gradient desulfurization concept of "coarse desulfurization - fine desulfurization - ultra-fine desulfurization", which utilizes the complementary advantages of different desulfurization technologies: biological desulfurization uses microbial metabolism to achieve low-cost coarse desulfurization, which is suitable for treating high concentrations of H2S; adsorption desulfurization uses chemical adsorption to achieve fine desulfurization of medium concentrations of H2S, which is highly efficient and fast; deep desulfurization uses hydrogenation catalysis to achieve ultra-fine desulfurization of trace amounts of sulfur, ensuring that the sulfur content is <0.1ppm. The three technologies work together to achieve complete removal of H2S from both "quantity" and "quality". The three-stage desulfurization subsystem can stably reduce the sulfur content in biogas to <0.1ppm, effectively avoiding the poisoning effect of H2S on the reforming catalyst, and extending the catalyst life from 1000-2000 hours in the existing technology to 8000 hours, which significantly reduces the catalyst replacement cost.

[0051] (2) The Ru-Ni bimetallic active component lowers the CH bond breaking barrier of CH4 through the "electronic effect," enabling the reforming reaction to proceed at medium and low temperatures; the CeZrO2 support oxidizes CO through the "oxygen storage-oxygen release cycle," enhancing H2 selectivity; and the K2O promoter inhibits carbon deposition through "acid-base regulation." Together, these three components form a three-in-one catalytic system of "activation-selectivity-stability," achieving low-temperature and efficient reforming. Low-temperature catalytic reforming (450-600℃) reduces the reaction temperature by more than 300℃ compared to traditional high-temperature reforming (850℃). Combined with the waste heat recovery of the heat exchange device, the system energy consumption is reduced by 40% compared to traditional steam reforming.

[0052] (3) Pd-Ag membranes utilize a "dissolution-diffusion" mechanism to achieve efficient initial separation of H2, with advantages including continuous operation and low energy consumption; PSA utilizes "adsorption selectivity" to achieve deep recovery of H2 from exhaust gas, with advantages including high recovery rate and high purity. The coupling of the two leverages both the high efficiency of membrane separation and the high recovery rate of PSA, achieving an optimal balance between "efficiency, purity, and recovery rate". The membrane separation-PSA coupling device can obtain hydrogen with a purity ≥99.99% (meeting the hydrogen standards for fuel cell vehicles), and a hydrogen recovery rate ≥95%, which is 5%-10% higher than single membrane separation or PSA technology.

[0053] (4) The Ru-Ni / CeZrO2 bifunctional catalyst has high activity and selectivity, with CH4 conversion rate ≥95%, H2 selectivity >90%, and carbon conversion efficiency (the proportion of carbon in biogas converted to CO2) increased to over 82%, significantly improving the utilization rate of raw biogas.

[0054] (5) By reducing fuel consumption (indirect emission reduction) and CO2 recovery and utilization (direct emission reduction) through low-temperature reforming, the CO2 emissions of the system are reduced by more than 35% compared with the existing biogas hydrogen production technology, thus achieving low-carbon hydrogen production.

[0055] (6) Due to factors such as reduced overall energy consumption, extended catalyst life, and improved raw material utilization, the cost of hydrogen production has been greatly reduced, providing an economic foundation for large-scale industrial application. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the process flow of the biogas catalytic reforming and membrane separation coupled hydrogen production system of the present invention. Detailed Implementation

[0057] To verify the performance of the hydrogen production system and method of the present invention, six examples and four comparative examples are provided below. By changing the biogas composition, process parameters and other conditions, the desulfurization effect, catalytic performance, separation efficiency, energy consumption, carbon emissions and other indicators of the system are tested.

[0058] I. Test Method Description Sulfur content determination: Gas chromatography-sulfur chemiluminescence detector (GC-SCD, Agilent 7890B) was used, with a detection limit of 0.01 ppm; CH4 conversion and H2 selectivity determination: Gas chromatography (GC-2014, Shimadzu) was used to analyze the components of the gas mixture before and after reforming. CH4 conversion = (number of moles of CH4 before reaction - number of moles of CH4 after reaction) / number of moles of CH4 before reaction × 100%. H2 selectivity = number of moles of H2 generated / (number of moles of CH4 consumed in the reaction × 3 + number of moles of CO consumed in the reaction × 1) × 100%. Hydrogen purity determination: An online hydrogen purity analyzer (DH-6000, Jinan Dehe) was used, with a detection accuracy of 0.01%. System energy consumption measurement: Using an electricity meter (to measure preheating, heating, and pump energy consumption) and a gas flow meter (to measure fuel gas consumption), combined with heat recovery calculations, the system energy consumption = (total energy consumption - recovered heat) / hydrogen production; CO2 emission measurement: CO2 concentration at each stage was measured using a gas analyzer (Testo 350), and the total emission was calculated based on the gas flow rate. Example Example 1

[0059] The hydrogen production process coupled with biogas catalytic reforming and membrane separation includes the following steps: S1: Biogas Pretreatment - Multi-stage Desulfurization The biogas feedstock is preheated to 100℃ by a preheating device and then introduced into a biological desulfurization tower. The tower is filled with a bed of sulfur-oxidizing bacteria, using a mixed inoculum of *Acidithiobacillus ferrooxidans* and *Thiobacillus thioparus* (1:1 ratio). The operating temperature is 28℃, the pH is 7.5, and the biogas residence time in the tower is 20 minutes. Under the action of the sulfur-oxidizing bacteria, H2S is oxidized to elemental sulfur or sulfate, initially removing H2S and reducing the H2S content in the biogas to 8 ppm. The biogas after biological desulfurization is passed into an adsorption desulfurization unit, which is filled with Fe2O3 / ZnO composite adsorbent. The mass ratio of Fe2O3 to ZnO is 1:2, the operating pressure is 0.8 MPa, the operating temperature is 40℃, and the residence time is 8 min. Under the action of the Fe2O3 / ZnO composite adsorbent, H2S is further removed, reducing the H2S content in the biogas to 0.7 ppm. The biogas after adsorption desulfurization is fed into a deep desulfurization reactor, which is filled with a Ni-Mo / Al2O3 catalyst. The Ni loading is 4 wt%, the Mo loading is 2 wt%, the operating temperature is 250℃, the operating pressure is 0.8 MPa, and the space velocity is 800 h⁻¹. -1 Under the action of Ni-Mo / Al2O3 catalyst, residual H2S is deeply removed, and the sulfur content in the final biogas is 0.05 ppm; S2: Low-temperature catalytic reforming Biogas from deep desulfurization in S1 is mixed with water vapor at a volume ratio of 1:3, preheated to 350°C by a heat exchanger, and then fed into a low-temperature catalytic reforming reactor. Catalytic reforming is carried out under the action of a Ru-Ni / CeZrO2 bifunctional catalyst. The reactor operating temperature is controlled at 500°C, the operating pressure at 2 MPa, and the reaction space velocity at 2000 h⁻¹. -1 This produces a mixed gas containing H2, CO2, and a small amount of CO, with a CH4 conversion rate of 96.5% and an H2 selectivity of 92.3%. S3: Hydrogen separation and purification The mixed gas generated in S2 is passed into a Pd-Ag alloy hollow fiber membrane module of a membrane separation-PSA coupled device. The Ag content in the Pd-Ag alloy hollow fiber membrane is 25wt%, the H2 permeation rate of the membrane module is 25 m³ / m²·h, the operating temperature is 350℃, and the operating pressure is 1.5 MPa. H2 selectively permeates through the membrane module to obtain crude hydrogen with a purity ≥99.9%. The tail gas after membrane separation is fed into a PSA tail gas recovery unit, which is filled with molecular sieve adsorbent. The adsorption pressure is 1.2 MPa, the desorption pressure is 0.08 MPa, and the adsorption-desorption cycle is 8 min. The adsorbent selectively adsorbs CO2 and CO, while H2 is desorbed and recovered. The recovered H2 is mixed with the crude hydrogen obtained from membrane separation to finally obtain hydrogen gas with a purity of 99.999%. S4: Energy Recovery The high-temperature mixed gas (450-600℃) after the catalytic reforming reaction in S2 is first passed into a heat exchanger to exchange heat with the biogas or raw biogas after deep desulfurization in S1. After releasing heat, it enters the membrane separation module to realize energy recovery and utilization.

[0060] Biogas composition: CH4 60%, CO2 35%, H2S 200ppm, other 5%; Process parameters: Multi-stage desulfurization: biological desulfurization (28℃, pH 7.5, residence time 20 min) → adsorption desulfurization (0.8 MPa, 40℃, residence time 8 min) → deep desulfurization (250℃, 0.8 MPa, space velocity 800 h⁻¹) -1 ); Low-temperature reforming: biogas-water vapor volume ratio 1:3, reaction temperature 500℃, pressure 2.0MPa, space velocity 2000h⁻¹ -1 ; Membrane separation - PSA: Membrane module (350℃, 1.5MPa) → PSA (adsorption 1.2MPa, desorption 0.08MPa, cycle 8min); Test results: Sulfur content after desulfurization: 0.05 ppm; CH4 conversion rate: 96.5%, H2 selectivity: 92.3%; Hydrogen purity: 99.999%, recovery rate: 96.2%; System energy consumption: 18.2 MJ / kg H2 (42% lower than traditional methods); CO2 emissions: 5.8 kg CO2 / kg H2 (38% reduction compared to existing technologies); System energy efficiency ratio: 78%; Catalyst lifetime (predicted): 8200 hours. Example 2

[0061] The difference from Example 1 is that the following biogas and process parameters are used: Biogas composition: CH4 55%, CO2 40%, H2S 500ppm, other 5%; Process parameters: Multi-stage desulfurization: biological desulfurization (30℃, pH 7.8, residence time 25 min) → adsorption desulfurization (1.0 MPa, 45℃, residence time 10 min) → deep desulfurization (280℃, 1.0 MPa, space velocity 700 h⁻¹) -1 ); Low-temperature reforming: biogas-water vapor volume ratio 1:3.5, reaction temperature 520℃, pressure 2.2MPa, space velocity 1800h⁻¹ -1 ; Membrane separation - PSA: Membrane module (360℃, 1.8MPa) → PSA (adsorption 1.5MPa, desorption 0.09MPa, cycle 9min); Test results: Sulfur content after desulfurization: 0.07 ppm; CH4 conversion rate: 97.2%, H2 selectivity: 93.1%; Hydrogen purity: 99.998%, recovery rate: 95.8%; System energy consumption: 17.8 MJ / kgH2 (43% lower than traditional methods); CO2 emissions: 5.6 kg CO2 / kg H2 (40% reduction compared to existing technologies); System energy efficiency ratio: 79%; Catalyst lifetime (predicted): 8100 hours. Example 3

[0062] The difference from Example 1 is that the following biogas and process parameters are used: Biogas composition: CH4 65%, CO2 30%, H2S 100ppm, other 5%; Process parameters: Multi-stage desulfurization: biological desulfurization (25℃, pH 7.2, residence time 15 min) → adsorption desulfurization (0.6 MPa, 35℃, residence time 6 min) → deep desulfurization (220℃, 0.6 MPa, space velocity 900 h⁻¹) -1 ); Low-temperature reforming: biogas-water vapor volume ratio 1:2.5, reaction temperature 480℃, pressure 1.8MPa, space velocity 2200h⁻¹ -1 ; Membrane separation - PSA: Membrane module (340℃, 1.2MPa) → PSA (adsorption 1.0MPa, desorption 0.07MPa, cycle 7min); Test results: Sulfur content after desulfurization: 0.04 ppm; CH4 conversion rate: 95.8%, H2 selectivity: 91.8%; Hydrogen purity: 99.997%, recovery rate: 96.5%; System energy consumption: 18.5 MJ / kg H2 (41% lower than traditional methods); CO2 emissions: 6.0 kg CO2 / kg H2 (36% reduction compared to existing technologies); System energy efficiency ratio: 77%; Catalyst lifetime (predicted): 8300 hours. Example 4

[0063] The difference from Example 1 is that the following biogas and process parameters are used: Biogas composition: CH4 50%, CO2 45%, H2S 3000ppm, other 5%; Process parameters: Multi-stage desulfurization: biological desulfurization (35℃, pH 8.5, residence time 30 min) → adsorption desulfurization (1.0 MPa, 50℃, residence time 12 min) → deep desulfurization (300℃, 1.0 MPa, space velocity 600 h⁻¹) -1 ); Low-temperature reforming: biogas-water vapor volume ratio 1:4, reaction temperature 550℃, pressure 2.5MPa, space velocity 1500h⁻¹ -1 ; Membrane separation - PSA: Membrane module (380℃, 2.0MPa) → PSA (adsorption 1.5MPa, desorption 0.1MPa, cycle 10min); Test results: Sulfur content after desulfurization: 0.09 ppm; CH4 conversion rate: 97.5%, H2 selectivity: 92.8%; Hydrogen purity: 99.996%, recovery rate: 95.2%; System energy consumption: 19.3 MJ / kg H2 (39% lower than traditional methods); CO2 emissions: 5.9 kg CO2 / kg H2 (37% reduction compared to existing technologies); System energy efficiency ratio: 76%; Catalyst lifetime (predicted): 8000 hours. Example 5

[0064] The difference from Example 1 is that the following biogas and process parameters are used: Biogas composition: CH4 70%, CO2 25%, H2S 50ppm, other 5%; Process parameters: Multi-stage desulfurization: biological desulfurization (26℃, pH 7.0, residence time 18 min) → adsorption desulfurization (0.5 MPa, 30℃, residence time 5 min) → deep desulfurization (200℃, 0.5 MPa, space velocity 1000 h⁻¹) -1 ); Low-temperature reforming: biogas-water vapor volume ratio 1:2, reaction temperature 450℃, pressure 1.5MPa, space velocity 2500h⁻¹ -1 ; Membrane separation - PSA: Membrane module (320℃, 1.0MPa) → PSA (adsorption 0.8MPa, desorption 0.05MPa, cycle 6min); Test results: Sulfur content after desulfurization: 0.03 ppm; CH4 conversion rate: 95.2%, H2 selectivity: 90.5%; Hydrogen purity: 99.998%, recovery rate: 97.0%; System energy consumption: 18.8 MJ / kg H2 (40% lower than traditional methods); CO2 emissions: 6.2 kg CO2 / kg H2 (35% reduction compared to existing technologies); System energy efficiency ratio: 75%; Catalyst lifetime (predicted): 8400 hours. Example 6

[0065] The difference from Example 1 is that the following biogas and process parameters are used: Biogas composition: CH4 62%, CO2 33%, H2S 800ppm, other 5%; Process parameters: Multi-stage desulfurization: biological desulfurization (32℃, pH 8.0, residence time 22 min) → adsorption desulfurization (0.9 MPa, 42℃, residence time 9 min) → deep desulfurization (260℃, 0.9 MPa, space velocity 750 h⁻¹) -1 ); Low-temperature reforming: biogas-water vapor volume ratio 1:3.2, reaction temperature 510℃, pressure 2.1MPa, space velocity 1900h⁻¹ -1 ; Membrane separation - PSA: Membrane module (350℃, 1.6MPa) → PSA (adsorption 1.3MPa, desorption 0.08MPa, cycle 8min); Test results: Sulfur content after desulfurization: 0.06 ppm; CH4 conversion rate: 96.8%, H2 selectivity: 92.5%; Hydrogen purity: 99.999%, recovery rate: 96.0%; System energy consumption: 18.0 MJ / kg H2 (42.5% lower than traditional methods); CO2 emissions: 5.7 kg CO2 / kg H2 (39% reduction compared to existing technologies); System energy efficiency ratio: 78.5%; Catalyst lifetime (predicted): 8250 hours.

[0066] III. Comparative Example Comparative Example 1 (Conventional natural gas high-temperature reforming + Single PSA) Process scheme: Natural gas (CH4 95%) → No desulfurization → High temperature reforming (880℃, 2.0MPa, Ni / Al2O3 catalyst) → Single PSA separation (adsorption 1.5MPa, desorption 0.1MPa), using the process described in Example 1, with only the parameters changed above.

[0067] Test results: Catalyst poisoning: After 500 hours of operation, the CH4 conversion rate dropped from 90% to 65% (due to trace sulfur poisoning in the feedstock). CH4 conversion (initial stage): 90%, H2 selectivity: 85%; Hydrogen purity: 99.99%, recovery rate: 88%; System energy consumption: 30.5 MJ / kg H2; CO2 emissions: 11.2 kg CO2 / kg H2; System energy efficiency ratio: 58%; Catalyst life: 1200 hours.

[0068] Comparative Example 2 (Biogas single biological desulfurization + conventional Ni catalyst reforming + single membrane separation) Process scheme: biogas (same as Example 1) → single biological desulfurization (sulfur content 5ppm) → high temperature reforming (750℃, 2.0MPa, Ni / Al2O3 catalyst) → single Pd membrane separation (350℃, 1.5MPa), using the process described in Example 1, only the parameters are changed above; Test results: Sulfur content after desulfurization: 5 ppm; Catalyst poisoning: After 1000 hours of operation, the CH4 conversion rate decreased from 92% to 70%. CH4 conversion (initial stage): 92%, H2 selectivity: 88%; Hydrogen purity: 99.5%, recovery rate: 85%; System energy consumption: 26.8 MJ / kg H2; CO2 emissions: 9.5 kg CO2 / kg H2; System energy efficiency ratio: 62%; Catalyst life: 1800 hours.

[0069] Comparative Example 3 (Existing biogas hydrogen production system, without deep desulfurization + high-temperature reforming + single separation) Process scheme: Biogas (same as Example 1) → biological desulfurization + simple adsorption desulfurization (sulfur content 0.8ppm) → high temperature reforming (850℃, 2.0MPa, Ni-Ru / Al2O3 catalyst) → single PSA separation, using the process described in Example 1, only the parameters are changed above; Test results: Sulfur content after desulfurization: 0.8 ppm; Catalyst poisoning: After 2000 hours of operation, the CH4 conversion rate decreased from 94% to 75%. CH4 conversion (initial stage): 94%, H2 selectivity: 90%; Hydrogen purity: 99.99%, recovery rate: 90%; System energy consumption: 28.3 MJ / kg H2; CO2 emissions: 10.1 kg CO2 / kg H2; System energy efficiency ratio: 64%; Catalyst life: 2500 hours.

[0070] Comparative Example 4 The process described in Example 1 is used, except that a Ni / CeZrO2 catalyst is used for catalytic reforming at 500°C.

[0071] Test results: Sulfur content after desulfurization: 0.05 ppm; CH4 conversion rate: 86% (initial stage), H2 selectivity: 89%; Hydrogen purity: 99.6%, recovery rate: 89%; System energy consumption: 26.3 MJ / kg H2; CO2 emissions: 9.2 kg CO2 / kg H2; System energy efficiency ratio: 65%; Catalyst lifetime (predicted): 8200 hours.

[0072] Table 1: Performance Indicators Comparison Analysis of Examples and Comparative Examples Indicators Example 1-6 average Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Advantages of the invention (compared to Comparative Example 3) Sulfur content after desulfurization (ppm) 0.06 Without desulfurization (trace) 5 0.8 0.05 Sulfur content reduced 92.5% CH4conversion (%) 96.5 90 (initial) 92 (initial) 94 (initial) 86 (initial) Increased by 2.7% H2 selectivity (%) 92.2 85 88 90 89 Increased by 2.4% Hydrogen purity (%) 99.998 99.99 99.5 99.99 99.6 Equivalent, higher stability Hydrogen recovery rate (%) 96 88 85 90 89 Increased by 6.7% System energy consumption (MJ / kg H2) 18.3 30.5 26.8 28.3 26.3 Reduced by 35.3% CO2emissions (kg / kg H2) 5.8 11.2 9.5 10.1 9.2 Reduced by 42.6% System energy efficiency ratio (%) 77.5 58 62 64 65 Increased by 21.1% Catalyst life (hours) 8200 1200 1800 2500 8200 Increased by 228% As can be seen from the above comparison, the hydrogen production system and method of the present invention are significantly superior to the prior art in terms of desulfurization effect, energy consumption, catalytic performance, recovery rate and catalyst life. In particular, it has outstanding advantages in deep desulfurization, low temperature energy saving and low carbon emissions, and completely solves the core pain points of the prior art.

[0073] Therefore, this invention discloses a hydrogen production system and method that couples biogas catalytic reforming with membrane separation. By designing an integrated architecture of "multi-stage desulfurization subsystem - low-temperature catalytic reforming reactor - membrane separation - PSA coupling device", combined with a high-efficiency catalyst system and energy recovery design, it achieves efficient, low-carbon and low-cost hydrogen production from biogas.

[0074] The core technological breakthroughs of this invention are as follows: First, a three-stage progressive desulfurization subsystem was developed to achieve deep removal of sulfur content <0.1ppm, completely solving the catalyst poisoning problem; second, a Ru-Ni / CeZrO2 bifunctional catalyst was developed to achieve medium-low temperature catalytic reforming at 450-600℃, significantly reducing energy consumption; third, a membrane separation-PSA coupled separation system was constructed, taking into account both hydrogen purity (≥99.99%) and recovery rate (≥95%); and fourth, waste heat recovery was achieved through a heat exchange device, improving the system efficiency to over 77.5%.

[0075] Compared with existing technologies, the present invention reduces energy consumption by more than 35%, CO2 emissions by more than 35%, extends catalyst life to 8000 hours, and all performance indicators meet or exceed the requirements for industrial application.

[0076] This invention not only realizes the high-value utilization of biogas (converting low-grade thermal energy into high-quality hydrogen energy), but also provides a low-carbon and low-cost technical route for hydrogen energy production. It can be widely applied in biogas producing areas such as livestock farms, sewage treatment plants, and biomass processing centers, promoting the coordinated development of renewable energy and hydrogen energy industries, and is of great significance to achieving the "dual carbon" goal.

[0077] In summary, the hydrogen production system and method of the present invention have significant technological innovation, excellent performance and broad prospects for industrial application, and can effectively promote the resource utilization of biogas and the development of the hydrogen energy industry.

[0078] Those skilled in the art should understand that the above embodiments are merely exemplary embodiments, and various changes, substitutions, and modifications can be made without departing from the spirit and scope of this application.

Claims

1. A hydrogen production system coupled with biogas catalytic reforming and membrane separation, characterized in that, The system comprises a multi-stage desulfurization subsystem, a low-temperature catalytic reforming reactor, a membrane separation-PSA coupling device, a preheating device and a heat exchange device. The multi-stage desulfurization subsystem comprises a biological desulfurization tower, an adsorption desulfurization device and a deep desulfurization reactor connected in sequence along the flow direction of biogas. The low-temperature catalytic reforming reactor is provided with a Ru-Ni / CeZrO2 bifunctional catalyst bed and a heating device and a temperature control device. The membrane separation-PSA coupling device comprises a Pd-Ag alloy hollow fiber membrane assembly and a PSA tail gas recovery device. The preheating device is used to preheat raw biogas to 80-120℃ before entering the multi-stage desulfurization subsystem; the heat exchange device is in communication with the mixed gas outlet of the low-temperature catalytic reforming reactor at one end and with the outlet of the preheating device or the multi-stage desulfurization subsystem at the other end, and is used to recover the heat of the high-temperature mixed gas after reforming.

2. The system according to claim 1, wherein, The biological desulfurization tower is filled with a bed of sulfur-oxidizing bacteria, and the operation temperature is 25-35℃, the pH value is 7.0-8.5, and the residence time of biogas in the tower is 15-30min; the adsorption desulfurization device is filled with a Fe2O3 / ZnO composite adsorbent, the mass ratio of Fe2O3 to ZnO is 1:1-3, the operation pressure is 0.5-1.0MPa, and the operation temperature is 30-50℃; the deep desulfurization reactor is filled with a Ni-Mo / Al2O3 catalyst, the loading amount of Ni is 2-5wt%, the loading amount of Mo is 1-3wt%, the operation temperature is 200-300℃, and the operation pressure is 0.5-1.0MPa.

3. The system according to any one of claims 1-2, wherein, In the bifunctional catalyst, the loading amount of Ru is 0.5-2wt%, the loading amount of Ni is 1-5wt%, the carrier is a CeZrO2 solid solution, the molar ratio of Ce to Zr is 1:1-2, and 0.5-2wt% of K2O is added as an additive; the operation temperature of the reactor is controlled at 450-600℃, and the operation pressure is controlled at 1.5-2.5MPa.

4. The system according to any one of claims 1-2, wherein, The operation temperature of the Pd-Ag alloy hollow fiber membrane assembly is 300-400℃, and the operation pressure is 1.0-2.0MPa; the PSA tail gas recovery device is filled with a molecular sieve adsorbent, the adsorption pressure is 0.8-1.5MPa, the desorption pressure is 0.05-0.1MPa, and the adsorption-desorption cycle is 5-10min.

5. The system according to any one of claims 1-2, wherein, In the sulfur-oxidizing bacteria bed of the biological desulfurization tower, the sulfur-oxidizing bacteria are a mixed bacteria agent of Acidithiobacillus ferroxidans and Thiobacillus thioparus, and the bacteria amount ratio of the two is 1:1-2; the adsorption desulfurization device is provided with an adsorbent regeneration mechanism.

6. The system for hydrogen production from biogas catalytic reforming and membrane separation according to any one of claims 1-2, characterized in that, The catalyst bed of the low-temperature catalytic reforming reactor is divided into two sections, the upper section is a catalyst pre-activation zone, and the lower section is a main reaction zone; the heating device is an electric heating pipe or a heat conduction oil heating jacket, and the temperature control precision of the temperature control device is ±5℃.

7. A hydrogen production process based on the hydrogen production system of any one of claims 1-6, characterized in that, The system comprises the following steps: S1: biogas pretreatment-multi-stage desulfurization The raw biogas is preheated to 80-120℃ by a preheating device, and then introduced into a biological desulfurization tower, where H2S is oxidized to elemental sulfur or sulfate under the action of sulfur-oxidizing bacteria, so that H2S is preliminarily removed and the content of H2S in the biogas is reduced to 5-10 ppm; The biogas after biological desulfurization is introduced into an adsorption desulfurization device, where H2S is further removed under the action of a Fe2O3 / ZnO composite adsorbent, so that the content of H2S in the biogas is reduced to 0.5-1 ppm; The biogas after adsorption desulfurization is introduced into a deep desulfurization reactor, where residual H2S is deeply removed under the action of a Ni-Mo / Al2O3 catalyst, so that the content of sulfur in the final biogas is <0.1 ppm; S2: Low-temperature catalytic reforming The biogas after deep desulfurization in S1 is mixed with water vapor at a volume ratio of 1:2-4, preheated to 300-400 DEG C by a heat exchange device, and then introduced into a low-temperature catalytic reforming reactor to perform catalytic reforming reaction under the action of a Ru-Ni / CeZrO2 dual-function catalyst, the reaction space velocity is 1000-3000 h -1 , a mixed gas containing H2, CO2 and a small amount of CO is generated, wherein the CH4 conversion rate is ≥95% and the H2 selectivity is >90%. S3: Hydrogen separation and purification The mixed gas generated in S2 is introduced into a Pd-Ag alloy hollow fiber membrane assembly of a membrane separation-PSA coupling device, H2 selectively permeates through the membrane assembly, and crude hydrogen with a purity of ≥99.9% is obtained; The tail gas after membrane separation is introduced into a PSA tail gas recovery device, where the adsorbent selectively adsorbs CO2 and CO, and H2 is desorbed and recovered, the recovered H2 is mixed with the crude hydrogen obtained by membrane separation, and finally hydrogen with a purity of ≥99.99% is obtained; S4: Energy recovery The high-temperature mixed gas after the catalytic reforming reaction in S2 is first introduced into a heat exchange device, and then introduced into the membrane separation assembly after heat exchange with the biogas after deep desulfurization in S1 or the raw biogas, so as to realize energy recovery and utilization.

8. The hydrogen production process of claim 7, wherein, The temperature of water vapor in S2 is 350-400℃, and the pressure is consistent with that of the biogas; the permeation side pressure of the membrane separation assembly in S3 is 0.1-0.2 MPa, and the pressure difference between the two sides of the membrane drives H2 permeation.

9. The hydrogen production process of claim 7, wherein, It also includes a tail gas treatment step: the tail gas after desorption in the PSA tail gas recovery device in S3 can be used for food-grade CO2 production or carbon sequestration by injection into the ground after drying and purification.

10. Hydrogen production process according to any one of claims 7-9, characterized in that, The operating temperature of the catalytic reforming reaction in S2 is controlled at 450-600℃, and the operating pressure is controlled at 1.5-2.5 MPa; the operating temperature of H2 selective permeation through the membrane assembly in S3 is 300-400℃, and the operating pressure is 1.0-2.0 MPa; the adsorption pressure of the tail gas recovery device in S3 is 0.8-1.5 MPa, the desorption pressure is 0.05-0.1 MPa, and the adsorption-desorption cycle is 5-10 min.

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