Method for producing hydrogen from coke oven gas based on electrochemical reduction CO2 technology

Abstract

The invention provides a method for producing hydrogen from coke oven gas based on an electrochemical CO2 reduction technology. The method comprises the steps of gas pretreatment, multi-stage membrane separation, catalytic reaction and electrocatalytic reduction. Particulate matters, tar and moisture are removed through cyclone separation and activated carbon adsorption, and gas purification is ensured by combining MDEA and zinc oxide desulfurization; and the separation of high-purity hydrogen is realized by adopting a multi-stage membrane separation technology. CH4 and CO are efficiently converted through high-temperature and low-temperature water gas conversion and methane steam reforming reaction, and the hydrogen yield is further increased. The electrocatalytic reduction technology is innovatively adopted, CO2 is converted into CO, H2 and HCOOH, and carbon resource circulation is achieved. The method has the characteristics of high efficiency, low consumption and low carbon, and is suitable for deep purification and resource utilization of coke oven gas.

Description

Technical Field

[0001] The present invention relates to the research field of methods for preparing hydrogen by using coke oven gas as a raw material, and in particular to a method for preparing hydrogen by using coke oven gas as a raw material based on multi-stage separation and catalytic technology. Background Art

[0002] Coke oven gas is an important by-product produced in the coking industry. Its main components are hydrogen (H2, 50-60% by volume), methane (CH4, 20-28% by volume), carbon monoxide (CO, 7-10% by volume) and carbon dioxide (CO2, 2-4% by volume), as well as small amounts of other gases, tar and sulfide. Coke oven gas is regarded as a clean energy and chemical raw material with great potential.

[0003] There are significant advantages in producing hydrogen from coke oven gas: First, coke oven gas is a by-product gas in the coking industry, with a wide range of sources and low costs, especially in the steel and chemical industries where resources are abundant. Secondly, its hydrogen content is high, usually reaching more than 50%, with high extraction efficiency, and related technologies are relatively mature. Thirdly, the use of coke oven gas to produce hydrogen can reduce the environmental pollution caused by its direct combustion, achieve efficient utilization of resources, and have significant environmental benefits. Finally, this technology is highly consistent with the development direction of clean energy and can effectively assist carbon reduction strategies. Overall, the production of hydrogen from coke oven gas not only performs well in terms of economy and feasibility, but can also improve the sustainable development level of industry and society through comprehensive resource utilization and pollution reduction.

[0004] The production of hydrogen from coke oven gas mainly faces the following problems: First, coke oven gas contains a variety of impurities, such as hydrogen sulfide, tar, ammonia and cyanide. The presence of these impurities not only corrodes the equipment, but also reduces the efficiency of hydrogen production. Therefore, an efficient purification process is required, but this will increase the complexity of the process and the operating cost. Secondly, in the process of hydrogen separation, the existing adsorption separation, membrane separation or low-temperature separation technology has the problems of high energy consumption and limited efficiency, and needs to be systematically optimized. Thirdly, the hydrogen in coke oven gas is mixed with other combustible gases (such as methane and carbon monoxide). How to improve the purity of hydrogen extraction through highly selective catalysts or advanced separation technologies is a key technical difficulty. In addition, the emission of carbon dioxide and other greenhouse gases accompanying the hydrogen production process also requires technical means to capture and treat in order to meet the requirements of green energy development. Therefore, how to reduce process complexity, improve separation efficiency, reduce energy consumption and reduce environmental impact is the core problem that needs to be solved in the hydrogen production technology from coke oven gas.

[0005] The above problems influence and restrict each other, which seriously hinder the resource utilization of coke oven gas and must be solved comprehensively and systematically. In response to the above problems, this patent proposes a method for preparing hydrogen with coke oven gas as raw material based on multi-stage separation and catalytic technology, aiming to achieve high-purity separation of hydrogen and recycling of carbon resources through deep purification and multi-path efficient conversion of coke oven gas. This process effectively removes impurities through refined pretreatment measures, significantly improves hydrogen production through multi-stage membrane separation technology and catalyst optimization, and at the same time, electrocatalytic reduction technology utilizes CO2 resources to form a closed-loop carbon circulation system, thereby achieving both economic and environmental benefits. This patent not only provides a new solution for the efficient utilization of coke oven gas, but also has broad application prospects and industrial value. Summary of the invention

[0006] In view of the above problems, in order to achieve the purpose of the present invention, the present invention adopts the following technical solutions:

[0007] A method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology, comprising the following three stages: separation of hydrogen from coke oven gas, hydrogen production from coke oven gas, and carbon cycle of coke oven gas:

[0008] Stage 1: Separation of Hydrogen from Coke Oven Gas

[0009] Step 1-1: Removal of particulate matter: First, the coke oven gas passes through a cyclone separator to separate larger particles to the outer wall and discharge them. Secondly, the bag filter dust collector adopts a two-stage series method to control the temperature of the coke oven gas at 100°C to pass through the bag filter dust collector to capture smaller particles.

[0010] Technical description: Both cyclone separators and bag filter dust collectors are used to remove solid particles from the gas to prevent particles from polluting and clogging the membrane system. Tar condenses at low temperatures and blocks the surface of the filter bag, causing pollution, clogging or damage; too high a temperature will damage the filter bag, so the temperature of the coke oven gas is controlled at 100°C. The two-stage series connection of the bag filter significantly improves the removal effect and avoids physical damage to the membrane by particles.

[0011] Step 1-2: Tar removal: The coke oven gas to remove particulate matter is cooled to 60°C and passed through activated carbon.

[0012] Technical description: The purpose of controlling the coke oven gas at 60℃ to pass through the activated carbon is to remove tar and some water, and avoid tar pollution and blockage of the membrane. The activated carbon reacts chemically or adsorbs with the tar molecules to further remove tar, water and ammonia in the gas.

[0013] Step 1-3: Primary desulfurization: The coke oven gas from which tar is removed is subjected to methyldiethanolamine (MDEA) under the condition of 0.1MPa-5MPa to adsorb H2S in the coke oven gas.

[0014] Technical description: Sulfur is the main factor affecting the catalytic conversion of coke oven gas, and it is crucial to adopt an economical and reasonable desulfurization method. The MDEA absorption method can efficiently remove relatively high concentrations of H2S in the gas, and the H2S concentration is reduced to below 10ppm after treatment. The primary desulfurization uses the MDEA absorption method to treat high concentrations of H2S, avoiding premature saturation of adsorbents such as zinc oxide, and increased energy consumption at higher temperatures.

[0015] Step 1-4: Multi-stage membrane hydrogen separation: including primary membrane separation, secondary membrane fine separation and secondary membrane fine separation; primary membrane separation: coke oven gas after primary desulfurization is separated by polyimide (PI) membrane under the conditions of 0.1MPa-3MPa and 30℃-70℃, the gas permeated by PI membrane is primary permeate gas, the primary permeate gas enters secondary membrane fine separation for separation, the PI membrane retentate gas is primary retentate gas, the primary retentate gas enters secondary membrane fine separation for separation; secondary membrane fine separation: primary permeate gas is separated by polyamide (PA) membrane under the conditions of 2MPa-4MPa and 30℃-50℃, the gas permeated by PA membrane is secondary permeate gas 1, secondary permeate gas 1 is high-purity hydrogen Gas, PA membrane retentate gas is secondary retentate gas 2, secondary retentate gas 2 is mixed with primary desulfurized coke oven gas for primary membrane separation; two-stage membrane fine separation: the primary retentate gas is separated by a polyimide membrane under the conditions of 2MPa-4MPa and 30℃-50℃, the second-stage membrane fine separation PI membrane permeate gas is second-stage permeate gas 1, the second-stage permeate gas 1 is mixed with the primary permeate gas for secondary membrane fine separation, the second-stage membrane fine separation PI membrane retentate gas is second-stage retentate gas 2, and the second-stage retentate gas 2 enters the second stage reaction.

[0016] Technical description: In steps 1-4, a variety of hydrogen separation processes are used. Organic membrane separation has a low cost and is the main source of hydrogen. In addition, the concentration of hydrogen in the gas on the retentate side should be reduced as much as possible, which is beneficial to the subsequent improvement of the conversion capacity of CH4 and CO. Primary membrane separation: Permeate side (hydrogen-rich gas): The purity of hydrogen is increased to 60%-90%, and enters the secondary membrane for fine separation and purification of hydrogen. Because the content of H2S in the secondary membrane separation is low; therefore, a polyamide membrane with poor tolerance to H2S but lower cost is used compared to a polyimide membrane.

[0017] Phase 2: Hydrogen production from coke oven gas

[0018] Step 2-1: Secondary desulfurization: The second stage retentate gas 2 is heated to 300°C-450°C and subjected to secondary desulfurization by zinc oxide.

[0019] Technical description: The iron oxide and zinc oxide method can remove low-concentration H2S, ensuring that the H2S concentration drops below 1 ppm, ensuring the smooth progress of the catalytic reaction; the reaction temperature of 300℃-450℃ is close to the temperature required for the high-temperature water-gas shift reaction in step 2-2, avoiding repeated heating.

[0020] Step 2-2: High temperature water gas shift reaction (HWGSR): The gas after secondary desulfurization is subjected to high temperature water gas shift reaction to prepare CO2 and H2, with Fe3O4 as the main catalyst and Cr2O3 as the auxiliary agent, and water vapor is introduced to control the molar ratio of water vapor to carbon to be 1.5:1 to 2:1, pressure: 0.5MPa-3MPa, 300℃-450℃, space velocity of 3000m 3 / (m 3 ×h), the hydrogen generated by the reaction is separated by a palladium alloy membrane, and the gas after removing the hydrogen is marked as HWGSRG.

[0021] Technical description: H2 and CO2 are generated through the water-gas shift reaction (WGSR) CO+H2O→CO2+H2. WGSR is an exothermic reaction, which is more favorable at low temperatures in terms of thermodynamics, but the reaction rate is faster at high temperatures; the high temperature stage mainly focuses on the rate, and the low temperature stage mainly focuses on the balance; therefore, it is divided into high-temperature water-gas shift reaction (HWGSR) and low-temperature water-gas shift reaction (LWGSR). At high temperatures of 300-450℃, CO is rapidly converted, and the conversion rate of CO is increased by increasing the concentration of reactants (H2O) and reducing the concentration of products (H2). Usually, the molar ratio of WGSR water vapor to CO is greater than 2.5:1, so as to improve the conversion rate and avoid carbon deposition; however, excess water vapor will significantly increase the production cost. In step 2-2, the amount of water vapor far exceeds the amount required for this step, and the remaining water vapor is further used as a raw material for methane steam reforming. The water vapor in this step is 300℃-450℃, and the temperature is raised to 700℃-800℃ in the next step on this basis. There is no additional energy consumption in this step. Fe3O4 is the main catalyst and Cr2O3 is the auxiliary agent, which has good high temperature resistance.

[0022] Step 2-3: Methane Steam Reforming (SMR): The gas HWGSRG after the reaction in step 2-2 is heated to 1000m 3 / (m 3 ×h) through Ni / Al2O3 catalyst to carry out methane steam reforming reaction, and the gas after the reaction is marked as SMRG.

[0023] Technical description: The steam reforming reaction of alkane is CH4+H2O→CO+3H2. Nickel-based catalysts have the advantages of low cost, high catalytic efficiency and suitability for industrial operation, but their disadvantages are also very obvious, easy to deposit carbon and sensitive to sulfur. The present invention adopts two processes for desulfurization. Step 2-2 removes the original SMR product (CO) in the gas to improve the CH4 conversion efficiency. The coke oven gas SMR reaction conventionally requires a higher pressure (1MPa-5MPa), which is mainly for the purpose of energy recovery and avoiding carbon deposition. Usually in the coke oven gas SMR reaction, on the one hand, the carbon water is relatively high, and on the other hand, a large amount of hydrogen in the coke oven gas will be converted into water, resulting in a large amount of high-temperature water vapor after the reaction. High pressure can effectively improve the utilization value of steam waste heat. In addition, the coke oven gas has a large volume, which is conducive to reducing equipment investment after compression. However, the SMR reaction is a significant increase in volume, and pressurization is obviously unfavorable to the reaction balance. In order to reduce the problem of decreased conversion rate due to pressurization, it is necessary to increase the conversion temperature, usually 700℃ to 900℃, or even higher; overheating causes catalyst sintering and CH4 cracking to produce carbon deposition. This has led to a vicious circle of mutual constraints between conversion rate and cost, pressure and temperature, carbon-water ratio and carbon deposition. In terms of raw materials for this step: the components of gas HWGSRG are water vapor, CH4 and CO2 generated by high-temperature water-gas shift reaction. Most of the gas in coke oven gas has been separated. The gas volume in this step is small and the equipment investment cost is not high. The generated CO2 can effectively inhibit the formation of carbon deposition. In terms of reaction conditions: low pressure improves conversion rate, 700℃ to 800℃ helps to improve the conversion rate of CH4 and avoid the occurrence of carbon deposition.

[0024] Step 2-4: Low temperature water gas shift reaction (LWGSR): water mist and water vapor are introduced into the SMRG gas obtained in step 2-3, and the molar ratio of water vapor to CO is controlled to be 2:1 to 3:1. The gas temperature is regulated to be 200℃-300℃, and the catalyst is CuO-ZnO-Al2O3; pressure: 0.5MPa-3MPa, and the space velocity is 500-1000m 3 / (m 3 ×h), and the gas after the reaction is marked as LWGSRG.

[0025] Technical description: Convert newly generated CO. In this stage, low temperature, higher water-to-carbon ratio and lower space velocity are used to further improve the conversion rate of the remaining CO. Adding water mist and water vapor in this step can not only increase the concentration of the reactants, but also regulate the reaction temperature.

[0026] Step 2-5: Separation of hydrogen by pressure swing adsorption (PSA): LWGSRG separates H2 by pressure swing adsorption at 25℃-50℃ through two-stage series connection of 5A or 13X molecular sieves, adsorption pressure: 1MPa-3MPa, desorption pressure: 0.1MPa-0.2MPa. The H2 separated by PSA is further purified by secondary membrane separation in step 1-4.

[0027] Technical description: Molecular sieves (such as 5A, 13X) have strong CO2 adsorption capacity and certain selectivity for CO and CH4, and can separate and purify hydrogen. When the adsorbent is close to saturation, the adsorbed CO2 and a small amount of CO and CH4 are released by reducing the pressure. Secondary membrane separation further purifies the hydrogen, and the purity can reach 99.99%, meeting the requirements of high-purity hydrogen.

[0028] Stage 3: Carbon cycle of coke oven gas

[0029] Step 2-5 reduces the pressure to release the adsorbed gas, wherein 5%-95% of the released gas is electrochemically reduced using nickel supramolecular tubes as catalysts at a reaction potential of -1.2 V vs. RHE and an electrolyte of 0.1 M potassium chloride. The generated gas is mainly carbon monoxide and directly enters step 2-2: high-temperature water-gas shift reaction; the remaining released gas is electrochemically reduced using Sn3O(OH)2Cl2 as a catalyst under the same reaction conditions (-1.2 V vs. RHE, 0.1 M KCl). The main products of the reaction are HCOOH and a small amount of gas. The gas composition is mainly H2 and also contains some CO. The gas generated by the reaction directly enters step 2-4: low-temperature water-gas shift reaction.

[0030] Technical description: The gas released by adsorption is mainly CO2. Under specific conditions, nickel supramolecular tubes are used as catalysts to convert CO2 into CO through electrocatalytic reduction reactions. The Faraday efficiency of CO in this reaction is as high as 77.4%, which can efficiently achieve CO2 conversion and promote carbon circulation. The remaining released gas is treated by another electrocatalytic pathway, using Sn3O(OH)3Cl2 as a catalyst. The main products of this reaction are HCOOH and a small amount of gas, in which the gas component is mainly H2 and also contains some CO. HCOOH is not only an important raw material for hydrogen production, but also has the function of carbon fixation, which helps to reduce carbon emissions. Since the gas component produced by the reaction is mainly hydrogen, it is costly and uneconomical to extract hydrogen through palladium alloy membrane separation in the high-temperature water-gas shift reaction. Therefore, these gases are selected to be introduced into steps 2-4: participating in the low-temperature water-gas shift reaction. This can effectively utilize the remaining carbon resources and realize the closed-loop cycle of carbon. Beneficial Effects

[0031] 1. Improve the efficiency of coke oven gas treatment, through the two-stage particulate matter and tar removal process, effectively avoid pollution and blockage, extend the life of the equipment, and ensure the stability and efficiency of subsequent treatment.

[0032] 2. The application of multi-stage membrane separation technology combined with efficient desulfurization process can significantly improve the hydrogen separation purity to 99.99%, achieve low-cost and efficient production, and meet industrial needs.

[0033] 3. Optimize reaction conditions, through reasonable water-carbon ratio and temperature control, combined with efficient catalyst design, significantly improve the conversion rate of CH4 and carbon monoxide, reduce energy consumption and avoid carbon deposition problems.

[0034] 4. Innovatively introduce electrocatalytic reduction technology to convert carbon dioxide into carbon monoxide, hydrogen and HCOOH, forming a carbon resource recycling system, effectively reducing carbon emissions and increasing the output of value-added products.

[0035] 5. The comprehensive design takes into account both environmental protection and economic benefits, and combines refined pretreatment, separation, conversion and circulation processes, which not only improves the hydrogen yield, but also significantly reduces equipment investment and operating costs, achieving the goal of sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a process flow chart of the present invention.

[0037] Figure 2 is the Faradaic efficiency of Sn3O(OH)2Cl2 electrocatalyst for H2 and HCOOH products under constant potential conditions.

[0038] Figure 3 is the Faradaic efficiency of Ni-CNT electrocatalyst for H2 and CO products under constant potential conditions. DETAILED DESCRIPTION

[0039] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0040] Example 1

[0041] A method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology, comprising the following three stages: separation of hydrogen from coke oven gas, hydrogen production from coke oven gas, and carbon circulation of coke oven gas.

[0042] Stage 1: Separation of Hydrogen from Coke Oven Gas

[0043] Step 1-1: Removal of particulate matter: First, the coke oven gas passes through a cyclone separator to separate larger particles to the outer wall and discharge them. Secondly, the bag filter dust collector adopts a two-stage series method to control the temperature of the coke oven gas at 100°C to pass through the bag filter dust collector to capture smaller particles.

[0044] Step 1-2: Tar removal: The coke oven gas to remove particulate matter is cooled to 60°C and passed through activated carbon.

[0045] Step 1-3: Primary desulfurization: The coke oven gas from which tar is removed is subjected to methyldiethanolamine under the condition of 0.1MPa-5MPa to adsorb H2S in the coke oven gas.

[0046] Step 1-4: Multi-stage membrane hydrogen separation: including primary membrane separation, secondary membrane fine separation and secondary membrane fine separation; primary membrane separation: coke oven gas after primary desulfurization is separated by polyimide (PI) membrane under the conditions of 0.1MPa-3MPa and 30℃-70℃, the gas permeated by PI membrane is primary permeate gas, the primary permeate gas enters secondary membrane fine separation for separation, the PI membrane retentate gas is primary retentate gas, the primary retentate gas enters secondary membrane fine separation for separation; secondary membrane fine separation: primary permeate gas is separated by polyamide (PA) membrane under the conditions of 2MPa-4MPa and 30℃-50℃, the gas permeated by PA membrane is secondary permeate gas 1, secondary permeate gas 1 is high-purity hydrogen Gas, PA membrane retentate gas is secondary retentate gas 2, secondary retentate gas 2 is mixed with primary desulfurized coke oven gas for primary membrane separation; two-stage membrane fine separation: the primary retentate gas is separated by a polyimide membrane under the conditions of 2MPa-4MPa and 30℃-50℃, the second-stage membrane fine separation PI membrane permeate gas is second-stage permeate gas 1, the second-stage permeate gas 1 is mixed with the primary permeate gas for secondary membrane fine separation, the second-stage membrane fine separation PI membrane retentate gas is second-stage retentate gas 2, and the second-stage retentate gas 2 enters the second stage reaction.

[0047] Phase 2: Hydrogen production from coke oven gas

[0048] Step 2-1: Secondary desulfurization: The second stage retentate gas 2 is heated to 300°C-450°C and subjected to secondary desulfurization by zinc oxide.

[0049] Step 2-2: High temperature water gas shift reaction (HWGSR): The gas after secondary desulfurization is subjected to high temperature water gas shift reaction to prepare CO2 and H2, with Fe3O4 as the main catalyst and Cr2O3 as the auxiliary agent, and water vapor is introduced to control the molar ratio of water vapor to carbon to be 1.5:1 to 2:1, pressure: 0.5MPa-3MPa, 300℃-450℃, space velocity of 3000m 3 / (m 3 ×h), the hydrogen generated by the reaction is separated by a palladium alloy membrane, and the gas after removing the hydrogen is marked as HWGSRG.

[0050] Step 2-3: Methane Steam Reforming (SMR): The gas HWGSRG after the reaction in step 2-2 is heated to 1000m 3 / (m 3 ×h) through Ni / Al2O3 catalyst to carry out methane steam reforming reaction, and the gas after the reaction is marked as SMRG.

[0051] Step 2-4: Low temperature water gas shift reaction (LWGSR): water mist and water vapor are introduced into the SMRG gas obtained in step 2-3, and the molar ratio of water vapor to CO is controlled to be 2:1 to 3:1. The gas temperature is regulated to be 200℃-300℃, and the catalyst is CuO-ZnO-Al2O3; pressure: 0.5MPa-3MPa, and the space velocity is 500-1000m 3 / (m 3 ×h), and the gas after the reaction is marked as LWGSRG.

[0052] Step 2-5: Separation of hydrogen by pressure swing adsorption (PSA): LWGSRG separates H2 by pressure swing adsorption at 25℃-50℃ through two-stage series connection of 5A or 13X molecular sieves, adsorption pressure: 1MPa-3MPa, desorption pressure: 0.1MPa-0.2MPa. The H2 separated by PSA is further purified by secondary membrane separation in step 1-4.

[0053] Stage 3: Carbon cycle of coke oven gas

[0054] In step 2-5, the pressure is reduced to release the adsorbed gas, wherein 5%-95% of the released gas is electrochemically reduced by using nickel supramolecular tubes as catalysts at a reaction potential of -1.2 V vs. RHE and an electrolyte of 0.1 M potassium chloride. The generated gas is mainly CO and directly enters step 2-2: high-temperature water-gas shift reaction; the remaining released gas is electrochemically reduced by using Sn3O(OH)2Cl2 as a catalyst under the same reaction conditions (-1.2 V vs. RHE, 0.1 M KCl). The main products of the reaction are HCOOH and a small amount of gas. The gas composition is mainly H2 and also contains some CO. The gas generated by the reaction directly enters step 2-4: low-temperature water-gas shift reaction.

[0055] Example 2

[0056] This example is basically the same as the method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology described in Example 1, with the difference being: primary desulfurization in steps 1-3: the coke oven gas from which tar has been removed is adsorbed by methyldiethanolamine at 3MPa to reduce the H2S concentration in the coke oven gas to below 10ppm.

[0057] Technical description: The purpose of controlling MDEA absorption at 3MPa is to ensure that the H2S concentration drops below 10ppm after treatment, and to avoid premature saturation of the adsorbent and increased energy consumption at higher temperatures.

[0058] Example 3

[0059] This example is basically the same as the method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology described in Example 3, except that: in steps 1-4, the multi-stage membrane hydrogen separation includes three parts: primary membrane separation, secondary membrane fine separation and secondary membrane fine separation; primary membrane separation: the coke oven gas after primary desulfurization is separated in 3 MPa, 40 ℃ conditions, separation and purification are carried out through polyimide (PI) membrane, the PI membrane permeate gas is the primary permeate gas, the primary permeate gas enters the secondary membrane fine separation for purification, the PI membrane retentate gas is the primary retentate gas, the primary retentate gas enters the second membrane fine separation for purification; Secondary membrane fine separation: the primary permeate gas is separated and purified by polyamide (PA) membrane under 3MPa, 40 ℃ conditions, the PA membrane permeate gas is the secondary permeate gas 1, the secondary permeate gas 1 is high-purity hydrogen, the PA membrane retentate gas is the secondary retentate gas 2, the secondary retentate gas 2 is mixed with the coke oven gas after primary desulfurization for primary membrane separation; Secondary membrane fine separation: the primary retentate gas is separated and purified by polyimide membrane under 3MPa, 40 ℃ conditions, the second membrane fine separation PI membrane permeate gas is the second permeate gas 1, the second permeate gas 1 is mixed with the primary permeate gas for secondary membrane fine separation, the second membrane fine separation PI membrane retentate gas is the second retentate gas 2, the second retentate gas 2 enters the second stage reaction.

[0060] Technical description: In steps 1-4, a variety of hydrogen separation processes are used to control pressure and temperature in order to achieve efficient separation of hydrogen from CH4 and carbon monoxide, and to ensure that the concentration of hydrogen in the retentate side gas is as low as possible, which is conducive to the subsequent improvement of methane and carbon monoxide conversion capacity.

[0061] Example 4

[0062] This example is basically the same as the method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology described in Example 3, except that: in step 2-1, secondary desulfurization: the second-stage retained gas 2 is heated to 450°C and secondary desulfurization is performed by zinc oxide to reduce the H2S concentration to below 1 ppm.

[0063] Technical description: The zinc oxide method can remove low-concentration H2S, ensuring that the H2S concentration drops below 1 ppm, ensuring the smooth progress of the catalytic reaction; the reaction temperature of 450°C is close to step 2-2 HWGSR, avoiding repeated heating.

[0064] Example 5

[0065] This example is basically the same as the method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology described in Example 4, except that: in step 2-2, high-temperature water-gas shift reaction: the secondary desulfurized gas is subjected to high-temperature water-gas shift reaction to prepare CO2 and H2, with Fe3O4 as the main catalyst and Cr2O3 as an auxiliary agent, and water vapor is introduced to control the molar ratio of water vapor to carbon to be 1.5:1, the pressure is 3MPa, and the space velocity is 3000m 3 / (m 3 ×h), and after the reaction, it is separated by a palladium alloy membrane, and the gas after removing the hydrogen is marked as HWGSRG.

[0066] Technical description: The mass ratio of water vapor to carbon is controlled to 1.5:1 and the pressure is 3MPa. The relatively low water volume can reduce energy consumption, and the higher pressure is conducive to the separation of the generated H2 as soon as possible.

[0067] Example 6

[0068] This example is basically the same as the method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 described in Example 5, except that: in step 2-3, CH4 steam reforming: the gas HWGSRG after the reaction in step 2-2 is heated at 800°C and 0.5MPa at 1000m 3 / (m 3 ×h) through the Ni / Al2O3 catalyst, and the gas after the reaction is marked as SMRG.

[0069] Technical description: In Example 5, the molar ratio of water vapor to carbon is controlled to be 1.5:1, the amount of water is relatively low, and controlling the temperature at 800°C and the pressure at 0.5 MPa helps to improve the conversion rate of CH4.

[0070] Example 7

[0071] This example is basically the same as the method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology described in Example 6, except that: in step 2-4, low-temperature water-gas shift reaction: water mist and water vapor are introduced into the SMRG gas obtained in step 2-3, and the molar ratio of water vapor to CO is controlled to be 3:1. By adjusting the ratio of water mist and water vapor and assisting with the temperature control device, the gas temperature is regulated to 200°C, and the catalyst is CuO-ZnO-Al2O3; pressure: 1MPa, space velocity: 500m 3 / (m 3 ×h), and the gas after the reaction is marked as LWGSRG.

[0072] Technical description: The amount of water vapor and CO is controlled to be 3:1, the gas temperature is 200℃ and the pressure is 1MPa, and the space velocity is 500m 3 / (m 3 ×h) is to further convert the residual carbon monoxide. This stage uses low temperature, low flow rate, and high water-carbon ratio to further improve the conversion rate of the remaining CO.

[0073] Example 8

[0074] This example is basically the same as the method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology described in Example 7, except that: in step 2-5, pressure swing adsorption separation of H2: LWGSRG is performed at 25°C through two stages of 5A or 13X molecular sieves in series to separate hydrogen by pressure swing adsorption, with an adsorption pressure of 3 MPa and a desorption pressure of 0.1 MPa.

[0075] Technical description: The temperature is controlled at 25°C, the adsorption pressure is 3MPa and the desorption pressure is controlled to separate and purify the hydrogen. When the adsorbent is close to saturation, the adsorbed CO2 and a small amount of impurity gases (CO, CH4, etc.) are released by reducing the pressure.

[0076] Example 9

[0077] This example is basically the same as the method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology described in Example 8, except that: the third stage: in the carbon cycle of the coke oven gas, step 2-5 reduces the pressure to release the adsorbed gas, wherein 5% of the released gas is electrochemically reduced by using nickel supramolecular tubes as catalysts at a reaction potential of -1.2 V vs. RHE and an electrolyte of 0.1 M potassium chloride. The generated gas is mainly carbon monoxide and directly enters step 2-2.

[0078] Technical description: 5% of the released gas is mainly solidified by using nickel supramolecular tubes as catalyst.

[0079] Example 10

[0080] This example is basically the same as the method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology described in Example 8, except that: the third stage: in the carbon cycle of the coke oven gas, steps 2-5 reduce the pressure to release the adsorbed gas, 95% of the released gas is released by using nickel supramolecular tubes as catalysts.

[0081] Technical description: 95% of the released gas is recycled mainly by using nickel supramolecular tubes as catalysts.

Claims

1. A method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology, comprising the following three stages: separation of hydrogen from coke oven gas, hydrogen production from coke oven gas, and carbon circulation of coke oven gas; Stage 1: Separation of Hydrogen from Coke Oven Gas Step 1-1: Removal of particles: First, the coke oven gas passes through a cyclone separator to separate larger particles to the outer wall and discharge. Secondly, the bag filter adopts a two-stage series mode to control the temperature of the coke oven gas at 100°C to pass through the bag filter to capture smaller particles. Step 1-2: Remove tar: The coke oven gas with particulate matter removed is cooled to 60°C and passed through activated carbon; Step 1-3: Primary desulfurization: The coke oven gas from which tar is removed is subjected to methyldiethanolamine under the condition of 0.1MPa-5MPa to adsorb H2S in the coke oven gas; Step 1-4 Multi-stage membrane hydrogen separation: including primary membrane separation, secondary membrane fine separation and second-stage membrane fine separation; primary membrane separation: coke oven gas after primary desulfurization is separated by a polyimide membrane under the conditions of 0.1MPa-3MPa and 30℃-70℃, the gas permeated by the polyimide membrane is the primary permeate gas, the primary permeate gas enters the secondary membrane fine separation for further separation, the polyimide membrane retentate gas is the primary retentate gas, the primary retentate gas enters the second-stage membrane fine separation for further separation; secondary membrane fine separation: the primary permeate gas is separated by a polyamide membrane under the conditions of 2MPa-4MPa and 30℃-50℃, the polyamide membrane permeate gas is the secondary permeate gas 1, and the secondary permeate gas 1 is high-purity hydrogen , the polyamide membrane retentate gas is the secondary retentate gas 2, the secondary retentate gas 2 is mixed with the primary desulfurized coke oven gas for primary membrane separation; the second-stage membrane fine separation: the primary retentate gas is separated by the polyimide membrane under the conditions of 2MPa-4MPa and 30℃-50℃, the second-stage membrane fine separation polyimide membrane permeate gas is the second-stage permeate gas 1, the second-stage permeate gas 1 is mixed with the primary permeate gas for secondary membrane fine separation, the second-stage membrane fine separation polyimide membrane retentate gas is the second-stage retentate gas 2, the second-stage retentate gas 2 enters the second stage reaction; Phase 2: Hydrogen production from coke oven gas Step 2-1: Secondary desulfurization: The second stage retentate gas 2 is heated to 300°C-450°C and subjected to secondary desulfurization by zinc oxide; Step 2-2 High-temperature water-gas shift reaction: The gas after secondary desulfurization is subjected to high-temperature water-gas shift reaction to prepare CO2 and H2, with Fe3O4 as the main catalyst and Cr2O3 as the auxiliary agent, and water vapor is introduced to control the molar ratio of water vapor to carbon to be 1.5:1 to 2:1, pressure: 0.5MPa-3MPa, 300℃-450℃, space velocity of 3000m 3 / (m 3 ×h), the hydrogen generated by the reaction is separated by a palladium alloy membrane, and the gas after the hydrogen is removed is marked as HWGSRG; Step 2-3 Methane steam reforming: The gas HWGSRG after the reaction in step 2-2 is heated at 700℃-800℃ and pressure 0.5MPa-1MPa at 1000m 3 / (m 3 ×h) through Ni / Al2O3 catalyst to carry out methane steam reforming reaction, and the gas after the reaction is marked as SMRG; Step 2-4 Low-temperature water-gas shift reaction: water mist and water vapor are introduced into the SMRG gas, the molar ratio of water vapor to CO is controlled to be 2:1 to 3:1, the gas temperature is regulated to be 200°C-300°C, the catalyst is CuO-ZnO-Al2O3; pressure: 0.5MPa-3MPa, space velocity is 500-1000m 3 / (m 3 ×h), the gas after reaction is marked as LWGSRG; Step 2-5: Pressure swing adsorption separation of hydrogen: LWGSRG separates H2 by pressure swing adsorption at 25°C-50°C through two-stage series connection of 5A or 13X molecular sieves, adsorption pressure: 1MPa-3MPa, desorption pressure: 0.1MPa-0.2MPa, and the separated H2 is further purified by secondary membrane separation in step 1-4; Stage 3: Carbon cycle of coke oven gas 5%-95% of the released gas of the adsorbed gas released by reducing the pressure in step 2-5 is electrochemically reduced by using nickel supramolecular tubes as catalysts at a reaction potential of -1.2 V vs. RHE and an electrolyte of 0.1 M potassium chloride. The generated gas directly enters step 2-2: high-temperature water-gas shift reaction; the remaining released gas is electrochemically reduced by using Sn3O(OH)2Cl2 as a catalyst at a reaction potential of -1.2 V vs. RHE and an electrolyte of 0.1 M potassium chloride. The main products of the reaction are HCOOH and a small amount of gas. The gas component is mainly H2 and also contains some CO. The gas generated by the reaction directly enters step 2-4: low-temperature water-gas shift reaction.

2. A method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology as claimed in claim 1, characterized in that: In step 1-3, primary desulfurization: the coke oven gas from which tar is removed is adsorbed by methyldiethanolamine at 3MPa.

3. A method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology as claimed in claim 2, characterized in that: The multi-stage membrane hydrogen separation in step 1-4 includes three parts: primary membrane separation, secondary membrane fine separation and second-stage membrane fine separation; primary membrane separation: the coke oven gas after primary desulfurization is separated and purified by a polyimide membrane under the conditions of 3 MPa and 40°C, the gas permeated by the polyimide membrane is the primary permeate gas, the primary permeate gas enters the secondary membrane fine separation for purification, the polyimide membrane retentate gas is the primary retentate gas, the primary retentate gas enters the second-stage membrane fine separation for purification; Secondary membrane fine separation: the primary permeate gas is separated and purified through a polyamide membrane at 3MPa and 40°C. The gas permeated by the polyamide membrane is the secondary permeate gas 1, which is high-purity hydrogen. The retentate gas of the polyamide membrane is the secondary retentate gas 2, which is mixed with the coke oven gas after primary desulfurization for primary membrane separation; Secondary membrane fine separation: the primary retentate gas is separated and purified through a polyimide membrane at 3MPa and 40°C. The gas permeated by the polyimide membrane of the second-stage membrane fine separation is the second-stage permeate gas 1, which is mixed with the primary permeate gas for secondary membrane fine separation. The retentate gas of the polyimide membrane of the second-stage membrane fine separation is the second-stage retentate gas 2, which enters the second stage reaction.

4. A method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology as claimed in claim 3, characterized in that: Secondary desulfurization in step 2-1: The second stage retentate gas 2 is heated to 450°C and subjected to secondary desulfurization by zinc oxide.

5. A method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology as claimed in claim 4, characterized in that: Step 2-2: High-temperature water-gas shift reaction: The secondary desulfurized gas is subjected to a high-temperature water-gas shift reaction to prepare CO2 and H2, with Fe3O4 as the main catalyst and Cr2O3 as an auxiliary agent, and water vapor is introduced to control the molar ratio of water vapor to carbon to be 1.5:1, the pressure is 3MPa, and the space velocity is 3000m 3 / (m 3 ×h), and after the reaction, it is separated by a palladium alloy membrane, and the gas after removing the hydrogen is marked as HWGSRG.

6. A method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology as claimed in claim 5, characterized in that: In step 2-3, steam reforming of CH4 is carried out by heating the gas HWGSRG after the reaction in step 2-2 at 800°C and 0.5 MPa at a rate of 1000 m 3 / (m 3 ×h) through the Ni / Al2O3 catalyst, and the gas after the reaction is marked as SMRG.

7. A method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology as claimed in claim 6, characterized in that: Low-temperature water-gas shift reaction in step 2-4: water mist and water vapor are introduced into the SMRG gas obtained in step 2-3, and the molar ratio of water vapor to CO is controlled to be 3:

1. The gas temperature is regulated to 200°C by adjusting the ratio of water mist and water vapor and assisting with the temperature control device. The catalyst is CuO-ZnO-Al2O3; pressure: 1MPa, space velocity: 500m 3 / (m 3 ×h), and the gas after the reaction is marked as LWGSRG.

8. A method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology as claimed in claim 7, characterized in that: In step 2-5, H2 is separated by pressure swing adsorption: LWGSRG separates H2 by pressure swing adsorption at 25°C through two stages of 5A or 13X molecular sieves in series, with an adsorption pressure of 3 MPa and a desorption pressure of 0.1 MPa.

9. A method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology as claimed in claim 8, characterized in that: The third stage: in the carbon cycle of coke oven gas, the pressure in step 2-5 is reduced to release the adsorbed gas, of which 5% of the released gas is electrochemically reduced by using nickel supramolecular tubes as catalysts at a reaction potential of -1.2 V vs. RHE and an electrolyte of 0.1 M potassium chloride. The generated gas is mainly carbon monoxide and directly enters step 2-2.

10. A method for producing hydrogen from coke oven gas based on electrochemical reduction of CO2 technology as claimed in claim 8, characterized in that: The third stage: the carbon cycle of coke oven gas in steps 2-5 reduces the pressure to release the adsorbed gas, of which 95% of the released gas is released by using nickel supramolecular tubes as catalysts.

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