A method for producing hydrogen from coke oven gas based on the electrochemical reduction of CO2 technology

Abstract

The present invention provides a method for hydrogen production from coke oven gas based on the electrochemical reduction of CO2 technology. The method includes gas pretreatment, multi-stage membrane separation, catalytic reaction, and electrocatalytic reduction. Particulates, tar, and moisture are removed through cyclone separation and activated carbon adsorption, and MDEA and zinc oxide desulfurization are combined to ensure gas purification; a multi-stage membrane separation technology is used to achieve the separation of high-purity hydrogen. Through high-temperature and low-temperature water gas shift and methane steam reforming reactions, CH4 and CO are efficiently converted to further increase the hydrogen production. The electrocatalytic reduction technology is innovatively adopted to convert CO2 into CO, H2, and HCOOH to achieve carbon resource recycling. The present invention has the characteristics of high efficiency, low consumption, and low carbon, and is applicable to the 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 from coke oven gas, and particularly to a method for preparing hydrogen from coke oven gas based on multi-stage separation and catalytic technology. Background Art

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

[0003] Producing hydrogen from coke oven gas has significant advantages: Firstly, coke oven gas is a by-product gas in the coking industry, with a wide source and low cost, especially rich in resources in the iron and steel and chemical industries. Secondly, its hydrogen content is relatively high, usually reaching more than 50%, with high extraction efficiency, and the related technology has been relatively mature. Thirdly, using coke oven gas to produce hydrogen can reduce the environmental pollution caused by its direct combustion, achieve the efficient utilization of resources, and has significant environmental benefits. Finally, this technology highly conforms to the development direction of clean energy and can effectively contribute to the carbon emission reduction strategy. Generally speaking, producing hydrogen from coke oven gas not only performs outstandingly in terms of economy and feasibility, but also can improve the sustainable development level of industry and society through comprehensive resource utilization and pollution reduction.

[0004] Producing hydrogen from coke oven gas mainly faces the following problems: Firstly, coke oven gas contains various impurities such as hydrogen sulfide, tar, ammonia, and cyanide. The existence of these impurities not only corrodes equipment but also reduces the hydrogen production efficiency. Therefore, an efficient purification process is required, but this will increase the process complexity and operating cost. Secondly, in the hydrogen separation process, the existing adsorption separation, membrane separation, or cryogenic separation technologies all have problems of high energy consumption and limited efficiency, and systematic optimization is needed. Thirdly, hydrogen in coke oven gas is mixed with other combustible gases (such as methane and carbon monoxide). How to improve the hydrogen extraction purity through highly selective catalysts or advanced separation technologies is a key technical difficulty. In addition, the emissions of carbon dioxide and other greenhouse gases accompanying the hydrogen production process also require technical means for capture and treatment to meet the requirements of green energy development. Therefore, how to reduce the process complexity, improve the separation efficiency, reduce energy consumption, and reduce environmental impacts is the core problem that urgently needs to be solved in the coke oven gas hydrogen production technology.

[0005] The above problems interact with and restrict each other, seriously hindering the resource utilization of coke oven gas, and must be comprehensively and systematically solved. In view of the above problems, this patent proposes a method for preparing hydrogen from coke oven gas 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, through electrocatalytic reduction technology, realizes the resource utilization of CO2 and forms a closed-loop carbon cycle system, thus achieving a double improvement in 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 industrialization value. Summary of the Invention

[0006] In view of the above problems, in order to achieve the object 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: hydrogen separation from coke oven gas, hydrogen production from coke oven gas, and carbon cycle of coke oven gas:

[0008] The first stage: hydrogen separation 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 particulate matter to the outer wall and discharge it. Secondly, the bag filter is connected in series in two stages, and the coke oven gas at a temperature of 100 °C is controlled to pass through the bag filter to capture smaller particulate matter.

[0010] Technical description: Both the cyclone separator and the bag filter are used to remove solid particles in the gas to prevent particulate matter from contaminating and blocking the membrane system. Tar condenses at low temperature and blocks the surface of the filter bag, causing pollution, blockage 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: Removal of tar: The coke oven gas from which particulate matter has been removed is cooled to 60 °C and passed through activated carbon.

[0012] Technical description: The purpose of controlling the coke oven gas at 60 °C to pass through activated carbon is to remove tar and part of the moisture, and avoid tar from contaminating and blocking the membrane. The activated carbon reacts chemically or adsorbs with tar molecules to further remove tar, moisture and ammonia in the gas.

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

[0014] Technical description: Sulfur is the main influencing factor in 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-concentration H2S in the gas, and the H2S concentration is reduced to below 10 ppm after treatment. The first-stage desulfurization uses the MDEA absorption method to treat high-concentration H2S, avoiding premature saturation of adsorbents such as zinc oxide and reducing energy consumption caused by relatively high temperatures.

[0015] Steps 1-4: Multi-stage membrane hydrogen separation: It includes three parts: primary membrane separation, secondary membrane fine separation, and second-stage membrane fine separation; Primary membrane separation: After the first-stage desulfurization, the coke oven gas is separated through a polyimide (PI) membrane under the conditions of 0.1 MPa - 3 MPa and 30 °C - 70 °C. The permeate gas of the PI membrane is the primary permeate gas, and the primary permeate gas enters the secondary membrane fine separation for separation. The retentate gas of the PI membrane is the primary retentate gas, and the primary retentate gas enters the second-stage membrane fine separation for separation; Secondary membrane fine separation: The primary permeate gas is separated through a polyamide (PA) membrane under the conditions of 2 MPa - 4 MPa and 30 °C - 50 °C. The permeate gas of the PA membrane is the secondary permeate gas 1, and the secondary permeate gas 1 is high-purity hydrogen. The retentate gas of the PA membrane is the secondary retentate gas 2, and the secondary retentate gas 2 is mixed with the coke oven gas after the first-stage desulfurization for primary membrane separation; Second-stage membrane fine separation: The primary retentate gas is separated through a polyimide membrane under the conditions of 2 MPa - 4 MPa and 30 °C - 50 °C. The permeate gas of the PI membrane in the second-stage membrane fine separation is the second-stage permeate gas 1, and the second-stage permeate gas 1 is mixed with the primary permeate gas for secondary membrane fine separation. The retentate gas of the PI membrane in the second-stage membrane fine separation is the second-stage retentate gas 2, and the second-stage retentate gas 2 enters the second-stage reaction.

[0016] Technical description: In Steps 1-4, multiple hydrogen separation processes are adopted. The organic membrane separation has a lower cost and is the main source of obtaining hydrogen. In addition, reducing the hydrogen concentration in the retentate gas as much as possible is beneficial to improving the conversion ability of CH4 and CO in the subsequent stage. Primary membrane separation: Permeate side (hydrogen-rich gas): The hydrogen purity is increased to 60% - 90%, and it enters the secondary membrane fine separation to purify hydrogen because the content of H2S in the secondary membrane separation is relatively low; Therefore, a polyamide membrane with poor tolerance to H2S but lower cost is used compared to the polyimide membrane.

[0017] Second stage: Hydrogen production from coke oven gas

[0018] Step 2-1: Secondary desulfurization: Heat the second-stage retentate gas 2 to 300 °C - 450 °C and conduct secondary desulfurization through zinc oxide.

[0019] Technical description: The iron oxide and zinc oxide methods can remove low-concentration H2S, ensuring that the H2S concentration is reduced to below 1 ppm to ensure the smooth progress of the catalytic reaction; The reaction temperature of 300 °C - 450 °C 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 a high-temperature water-gas shift reaction to prepare CO2 and H2. Using Fe3O4 as the main catalyst and Cr2O3 as the promoter, steam is introduced, and the molar ratio of steam to carbon is controlled to be 1.5:1 to 2:1, pressure: 0.5 MPa - 3 MPa, 300 °C - 450 °C, and the space velocity is 3000 m 3 / (m 3 ×h). The hydrogen generated by the reaction is separated through a palladium alloy membrane, and the gas after removing the hydrogen therein is marked as HWGSRG.

[0021] Technical description: Through the water-gas shift reaction (WGSR) CO + H2O → CO2 + H2, H2 and CO2 are generated. WGSR is an exothermic reaction, which is more favorable thermodynamically at low temperatures, but the reaction rate is faster at high temperatures; the rate is mainly concerned at the high-temperature stage, and the equilibrium is mainly concerned at the low-temperature stage; therefore, it is divided into high-temperature water-gas shift reaction (HWGSR) and low-temperature water-gas shift reaction (LWGSR). At a high temperature of 300 - 450 °C, CO is rapidly converted, and by increasing the concentration of the reactant (H2O) and decreasing the concentration of the product (H2), the conversion rate of CO is increased. Usually, the molar ratio of steam to CO in WGSR is greater than 2.5:1 to increase the conversion rate and avoid carbon deposition; however, excessive steam will significantly increase the production cost. In Step 2-2, the amount of steam far exceeds the amount required in this step, and the remaining steam is further used as the raw material for steam methane reforming. The steam in this step is at 300 °C - 450 °C, and the temperature is further increased to 700 °C - 800 °C in the next step, and there is no additional energy consumption in this step. Fe3O4 is the main catalyst and Cr2O3 is the promoter, which have good high-temperature resistance.

[0022] Step 2-3: Steam methane reforming (SMR): The gas HWGSRG after the reaction in Step 2-2 is passed through a Ni / Al2O3 catalyst at a space velocity of 1000 m 3 / (m 3 ×h) at 700 °C - 800 °C and a pressure of 0.5 MPa - 1 MPa to carry out the steam methane reforming reaction, and the gas after the reaction is marked as SMRG.

[0023] Technical description: The steam reforming reaction of methane 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, such as easy carbon deposition and sulfur sensitivity. The present invention adopts two processes for desulfurization. Step 2-2 removes the original SMR product (CO) in the gas, improving the CH4 conversion efficiency. The SMR reaction of coke oven gas usually requires a relatively high pressure (1 MPa - 5 MPa), mainly for the purpose of energy recovery and avoiding carbon deposition. In the SMR reaction of coke oven gas, on the one hand, the carbon-to-water ratio 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 volume of coke oven gas is large, and compression is beneficial to reducing equipment investment. However, the SMR reaction is a reaction with a significant increase in volume, and pressurization is significantly disadvantageous to the reaction equilibrium. To reduce the problem of decreased conversion rate caused by pressurization, it is necessary to increase the conversion temperature, usually at 700 °C to 900 °C, or even higher; overheating leads to catalyst sintering and carbon deposition due to CH4 cracking. Thus, a vicious circle of mutual restriction among conversion rate and cost, pressure and temperature, and carbon-to-water ratio and carbon deposition is formed. In terms of raw materials in this step: The gas HWGSRG consists of water vapor, CH4, and CO2 generated by the high-temperature water gas shift reaction. Most of the gases in the coke oven gas have been separated, and the volume of the gas in this step is small, so the equipment investment cost is not large. The generated CO2 can effectively inhibit carbon deposition. In terms of reaction conditions: Low pressure improves the conversion rate, and 700 °C to 800 °C helps to improve the CH4 conversion rate and avoid 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, controlling the molar ratio of water vapor to CO to be 2:1 to 3:1, regulating the gas temperature to 200 °C - 300 °C, and the catalyst is CuO-ZnO-Al2O3; pressure: 0.5 MPa - 3 MPa, and the space velocity is 500 - 1000 m 3 / (m 3 ×h), and the gas after the reaction is marked as LWGSRG.

[0025] Technical description: Converting newly generated CO. In this stage, a low temperature, a relatively high carbon-to-water ratio, and a small 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 reactants but also regulate the reaction temperature.

[0026] Step 2-5: Hydrogen separation by pressure swing adsorption (PSA): LWGSRG separates H2 by pressure swing adsorption through two-stage series-connected 5A or 13X molecular sieves at 25°C - 50°C. Adsorption pressure: 1 MPa - 3 MPa, desorption pressure: 0.1 MPa - 0.2 MPa. The H2 separated by PSA is further purified by the secondary membrane fine separation in Step 1-4.

[0027] Technical description: Molecular sieves (such as 5A, 13X) have strong adsorption capacity for CO2 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. The secondary membrane fine separation further purifies the hydrogen, and the hydrogen purity can reach 99.99%, meeting the requirements of high-purity hydrogen.

[0028] The third stage: Carbon cycle of coke oven gas

[0029] In Step 2-5, the pressure is reduced to release the adsorbed gas. Among the released gas, 5% - 95% is electrochemically reduced under the conditions of using nickel supramolecular tube as a catalyst, reaction potential of -1.2 V vs. RHE, and 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 this reaction are HCOOH and a small amount of gas. The gas composition is mainly H2, and also contains some CO. The generated gas 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, using nickel supramolecular tube as a catalyst, CO2 is converted into CO through an electrocatalytic reduction reaction. The Faraday efficiency of CO in this reaction is as high as 77.4%, which can efficiently realize the conversion of CO2 and promote the carbon cycle. The remaining released gas is treated through another electrocatalytic pathway, using Sn3O(OH)3Cl2 as a catalyst. The main products of this reaction are HCOOH and a small amount of gas. The gas composition 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 composition produced by the reaction is mainly hydrogen, it is costly and uneconomical to extract hydrogen through the palladium alloy membrane separation in the high-temperature water gas shift reaction. Therefore, it is selected to introduce these gases into Step 2-4: Participate in the low-temperature water gas shift reaction. This can effectively utilize the remaining carbon resources and achieve a closed-loop carbon cycle. Beneficial effects

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

[0032] 2. Apply a multi-stage membrane separation technology combined with an efficient desulfurization process to significantly improve the hydrogen separation purity to 99.99%, achieve low-cost and high-efficiency production, and meet industrial requirements.

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

[0034] 4. Innovatively introduce an electrocatalytic reduction process to convert carbon dioxide into carbon monoxide, hydrogen, and HCOOH, form a carbon resource recycling system, effectively reduce carbon emissions, and increase the output of value-added products.

[0035] 5. The comprehensive design takes into account both environmental protection and economic benefits. Combining refined pretreatment, separation, conversion, and recycling processes 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 is the process flow diagram of the present invention.

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

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

[0039] The present invention will be 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 do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all fall within the protection scope of the present invention.

[0040] Example 1

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

[0042] The first stage: hydrogen separation from coke oven gas

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

[0044] Step 1-2: Removal of tar: The coke oven gas after removing particulate matter is cooled to 60 °C and passes through activated carbon.

[0045] Step 1-3: Primary desulfurization: The coke oven gas after removing tar is under the conditions of 0.1 MPa - 5 MPa and passes through methyldiethanolamine to adsorb H2S in the coke oven gas.

[0046] Step 1-4: Multi-stage membrane hydrogen separation: It 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 under the conditions of 0.1 MPa - 3 MPa and 30 °C - 70 °C and passes through a polyimide (PI) membrane for separation. The permeate gas of the PI membrane is the primary permeate gas, and the primary permeate gas enters the secondary membrane fine separation for separation. The retentate gas of the PI membrane is the primary retentate gas, and the primary retentate gas enters the second-stage membrane fine separation for separation; Secondary membrane fine separation: The primary permeate gas is under the conditions of 2 MPa - 4 MPa and 30 °C - 50 °C and passes through a polyamide (PA) membrane for separation. The permeate gas of the PA membrane is the secondary permeate gas 1, and the secondary permeate gas 1 is high-purity hydrogen. The retentate gas of the PA membrane is the secondary retentate gas 2, and the secondary retentate gas 2 is mixed with the coke oven gas after primary desulfurization for primary membrane separation; Second-stage membrane fine separation: The primary retentate gas is under the conditions of 2 MPa - 4 MPa and 30 °C - 50 °C and passes through a polyimide membrane for separation. The permeate gas of the second-stage membrane fine separation PI membrane is the second-stage permeate gas 1, and the second-stage permeate gas 1 is mixed with the primary permeate gas for secondary membrane fine separation. The retentate gas of the second-stage membrane fine separation PI membrane is the second-stage retentate gas 2, and the second-stage retentate gas 2 enters the second-stage reaction.

[0047] Second stage: 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 passes through zinc oxide for secondary desulfurization.

[0049] Step 2-2: High-temperature water gas shift reaction (HWGSR): The gas after secondary desulfurization undergoes a high-temperature water gas shift reaction to prepare CO2 and H2. Using Fe3O4 as the main catalyst and Cr2O3 as the promoter, steam is introduced, and the molar ratio of steam to carbon is controlled at 1.5:1 to 2:1, pressure: 0.5 MPa - 3 MPa, 300 °C - 450 °C, and the space velocity is 3000 m 3 / (m 3 ×h), and the hydrogen generated by the reaction is separated through a palladium alloy membrane. The gas after removing the hydrogen is marked as HWGSRG.

[0050] Step 2-3: Steam methane reforming (SMR): The gas HWGSRG after the reaction in Step 2-2 is passed through a Ni / Al2O3 catalyst at 700 °C - 800 °C and a pressure of 0.5 MPa - 1 MPa with a space velocity of 1000 m 3 / (m 3 ×h) to carry out the steam methane reforming reaction, and the gas after the reaction is labeled as SMRG.

[0051] Step 2-4: Low-temperature water-gas shift reaction (LWGSR): Water mist and steam are introduced into the SMRG gas obtained in Step 2-3, controlling the molar ratio of steam to CO to be 2:1 to 3:1, regulating the gas temperature to 200 °C - 300 °C, with the catalyst being CuO-ZnO-Al2O3; pressure: 0.5 MPa - 3 MPa, and the space velocity being 500 - 1000 m 3 / (m 3 ×h), and the gas after the reaction is labeled as LWGSRG.

[0052] Step 2-5: Pressure swing adsorption (PSA) for hydrogen separation: LWGSRG is passed through two-stage series-connected 5A or 13X molecular sieves at 25 °C - 50 °C for pressure swing adsorption to separate H2, with the adsorption pressure: 1 MPa - 3 MPa and the desorption pressure: 0.1 MPa - 0.2 MPa. The H2 separated by PSA is further purified through the secondary membrane fine separation in Step 1-4.

[0053] The third stage: Carbon cycle of coke oven gas

[0054] In Step 2-5, the pressure is reduced to release the adsorbed gas. Among them, 5% - 95% of the released gas is electrochemically reduced using a nickel supramolecular tube as the catalyst under the conditions of a reaction potential of -1.2 V vs. RHE and an electrolyte of 0.1 M potassium chloride, and 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 using Sn3O(OH)2Cl2 as the catalyst under the same reaction conditions (-1.2 V vs. RHE, 0.1 M KCl). The main products of this reaction are HCOOH and a small amount of gas, with the gas composition mainly being H2 and also containing some CO, and the generated gas 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 the electrochemical reduction of CO2 technology described in Example 1. The difference lies in: in the first-stage desulfurization in steps 1-3, the coke oven gas from which tar has been removed is adsorbed through methyldiethanolamine under the condition of 3 MPa, and the H2S concentration in the coke oven gas is reduced to below 10 ppm.

[0057] Technical note: Controlling the MDEA absorption at 3 MPa is to ensure that the H2S concentration after treatment is reduced to below 10 ppm, 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 the electrochemical reduction of CO2 technology described in Example 3. The difference lies in: in the multi-stage membrane hydrogen separation in steps 1-4, it includes three parts: primary membrane separation, secondary membrane fine separation, and second-stage membrane fine separation; Primary membrane separation: After the first-stage desulfurization, the coke oven gas is separated and purified through a polyimide (PI) membrane under the conditions of 3 MPa and 40 °C. The permeate gas of the PI membrane is the primary permeate gas, and the primary permeate gas enters the secondary membrane fine separation for purification. The retentate gas of the PI membrane is the primary retentate gas, and 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 (PA) membrane under the conditions of 3 MPa and 40 °C. The permeate gas of the PA membrane is the secondary permeate gas 1, and the secondary permeate gas 1 is high-purity hydrogen. The retentate gas of the PA membrane is the secondary retentate gas 2, and the secondary retentate gas 2 is mixed with the coke oven gas after the first-stage desulfurization for primary membrane separation; Second-stage membrane fine separation: The primary retentate gas is separated and purified through a polyimide membrane under the conditions of 3 MPa and 40 °C. The permeate gas of the second-stage membrane fine separation PI membrane is the second-stage permeate gas 1, and the second-stage permeate gas 1 is mixed with the primary permeate gas for secondary membrane fine separation. The retentate gas of the second-stage membrane fine separation PI membrane is the second-stage retentate gas 2, and the second-stage retentate gas 2 enters the second-stage reaction.

[0060] Technical note: In steps 1-4, multiple hydrogen separation processes are adopted, and the pressure and temperature are controlled to achieve the efficient separation of hydrogen from CH4 and carbon monoxide, ensure that the hydrogen concentration in the retentate side gas is as low as possible, and is conducive to improving the conversion ability of methane and carbon monoxide in the subsequent process.

[0061] Example 4

[0062] This example is basically the same as the method for producing hydrogen from coke oven gas based on the electrochemical reduction of CO2 technology described in Example 3. The difference lies in: in the second-stage desulfurization in step 2-1, the second-stage retentate gas 2 is heated to 450 °C and undergoes second-stage desulfurization through zinc oxide, and the H2S concentration is reduced to below 1 ppm.

[0063] Technical description: The zinc oxide method can remove low-concentration H2S, ensuring that the H2S concentration is reduced to below 1 ppm, guaranteeing the smooth progress of the catalytic reaction; the reaction temperature of 450°C is close to that of 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 the electrochemical reduction of CO2 technology described in Example 4, except that: in Step 2-2, the high-temperature water gas shift reaction: the secondary desulfurized gas is subjected to a high-temperature water gas shift reaction to produce CO2 and H2, with Fe3O4 as the main catalyst and Cr2O3 as the promoter, water vapor is introduced, and the molar ratio of water vapor to carbon is controlled at 1.5:1, pressure: 3 MPa, and the space velocity is 3000 m 3 / (m 3 ×h). After the reaction, it is separated through a palladium alloy membrane, and the gas after removing the hydrogen therein is marked as HWGSRG.

[0066] Technical description: Control the molar ratio of water vapor to carbon at 1.5:1 and pressure: 3 MPa. The relatively low water volume can reduce energy consumption. In addition, the higher pressure is conducive to the rapid separation of the generated H2.

[0067] Example 6

[0068] This example is basically the same as the method for producing hydrogen from coke oven gas based on the electrochemical reduction of CO2 technology described in Example 5, except that: in Step 2-3, the steam reforming of CH4: the gas HWGSRG after the reaction in Step 2-2 is passed through a Ni / Al2O3 catalyst at 800°C and a pressure of 0.5 MPa at a space velocity of 1000 m 3 / (m 3 ×h), 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 at 1.5:1, the water volume is relatively low, and controlling the conditions at 800°C and a pressure of 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 the electrochemical reduction of CO2 technology described in Example 6. The differences are as follows: In the low-temperature water-gas shift reaction in Step 2-4: Water mist and steam are introduced into the SMRG gas obtained in Step 2-3. The molar ratio of steam to CO is controlled to be 3:1. By adjusting the ratio of water mist and steam and with the assistance of a temperature control device, the gas temperature is regulated to 200 °C, and the catalyst is CuO-ZnO-Al2O3; the pressure is 1 MPa, and the space velocity is 500 m 3 / (m 3 ×h), and the gas after the reaction is marked as LWGSRG.

[0072] Technical note: Controlling the molar ratio of steam to CO to be 3:1, the gas temperature at 200 °C, the pressure at 1 MPa, and the space velocity at 500 m 3 / (m 3 ×h) is to further convert the residual carbon monoxide. In this stage, a low temperature, low flow rate, and a relatively high water-carbon ratio are used 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 the electrochemical reduction of CO2 technology described in Example 7. The differences are as follows: In the pressure swing adsorption for separating H2 in Step 2-5: LWGSRG undergoes pressure swing adsorption for hydrogen separation through two-stage series-connected 5A or 13X molecular sieves at 25 °C. The adsorption pressure is 3 MPa, and the desorption pressure is 0.1 MPa.

[0075] Technical note: Controlling the temperature at 25 °C, the adsorption pressure at 3 MPa, and the desorption pressure is for the separation and purification of hydrogen. When the adsorbent is close to saturation, the adsorbed CO2 and a small amount of impurity gases (such as 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 the electrochemical reduction of CO2 technology described in Example 8. The differences are as follows: In the third stage: In the carbon cycle of coke oven gas, in Step 2-5, the pressure is reduced to release the adsorbed gas. Among them, 5% of the released gas is electrochemically reduced using a nickel supramolecular tube as a catalyst under the conditions of 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 note: 5% of the released gas uses a nickel supramolecular tube as a catalyst, mainly to achieve carbon solidification.

[0079] Example 10

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

[0081] Technical description: 95% of the released gas uses nickel supramolecular tubes as catalysts, mainly to achieve the carbon cycle.

Claims

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

2. The method for producing hydrogen from coke oven gas based on the electrochemical reduction of CO2 technology according to claim 1, characterized in that: Primary desulfurization in Step 1-3: The coke oven gas removing tar is adsorbed by methyldiethanolamine under the condition of 3 MPa.

3. The method for producing hydrogen from coke oven gas based on the electrochemical reduction of CO2 technology according to claim 2, characterized in that: Multi-stage membrane hydrogen separation in Step 1-4: It 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 through a polyimide membrane under the conditions of 3 MPa and 40 °C. The permeate gas of the polyimide membrane is the primary permeate gas, and the primary permeate gas enters the secondary membrane fine separation for purification. The retentate gas of the polyimide membrane is the primary retentate gas, and 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 under the conditions of 3 MPa and 40 °C. The permeate gas of the polyamide membrane is the secondary permeate gas 1, and the secondary permeate gas 1 is high-purity hydrogen. The retentate gas of the polyamide membrane is the secondary retentate gas 2, and the secondary retentate gas 2 is mixed with the coke oven gas after primary desulfurization for primary membrane separation; Second-stage membrane fine separation: The primary retentate gas is separated and purified through a polyimide membrane under the conditions of 3 MPa and 40 °C. The permeate gas of the polyimide membrane in the second-stage membrane fine separation is the second-stage permeate gas 1, and the second-stage permeate gas 1 is mixed with the primary permeate gas for secondary membrane fine separation. The retentate gas of the polyimide membrane in the second-stage membrane fine separation is the second-stage retentate gas 2, and the second-stage retentate gas 2 enters the second-stage reaction.

4. The method for producing hydrogen from coke oven gas based on the electrochemical reduction of CO2 technology according to claim 3, characterized in that: Secondary desulfurization in Step 2-1: The second-stage retentate gas 2 is heated to 450 °C and undergoes secondary desulfurization through zinc oxide.

5. The method for producing hydrogen from coke oven gas based on the electrochemical reduction of CO2 technology according to claim 4, characterized in that: High-temperature water-gas shift reaction in Step 2-2: The secondary desulfurized gas is subjected to a high-temperature water-gas shift reaction to prepare CO2 and H2. Using Fe3O4 as the main catalyst and Cr2O3 as an auxiliary agent, steam is introduced, and the molar ratio of steam to carbon is controlled at 1.5:1, pressure: 3 MPa, and space velocity is 3000 m 3 / (m 3 ×h). After the reaction, separation is carried out through a palladium alloy membrane, and the gas after removing hydrogen therein is marked as HWGSRG.

6. The method for producing hydrogen from coke oven gas based on the electrochemical reduction of CO2 technology according to claim 5, wherein: CH4 steam reforming in Step 2-3: The gas HWGSRG after the reaction in Step 2-2 is passed through a Ni / Al2O3 catalyst at 800 °C and a pressure of 0.5 MPa with a space velocity of 1000 m 3 / (m 3 ×h), and the gas after the reaction is labeled SMRG.

7. The method for producing hydrogen from coke oven gas by the electrochemical reduction of CO2 technology according to claim 6, characterized in that: Low-temperature water-gas shift reaction in Step 2-4: Water mist and steam are introduced into the SMRG gas obtained in Step 2-3. The molar ratio of steam to CO is controlled to be 3:

1. By adjusting the ratio of water mist and steam and with the assistance of a temperature control device, the gas temperature is regulated to 200 °C, and the catalyst is CuO-ZnO-Al2O3; Pressure: 1 MPa, space velocity is 500 m 3 / (m 3 ×h), and the reacted gas is marked as LWGSRG.

8. The method for producing hydrogen from coke oven gas based on the electrochemical reduction of CO2 technology as claimed in claim 7, characterized in that: Pressure swing adsorption for H2 separation in Step 2-5: LWGSRG undergoes pressure swing adsorption for H2 separation through two-stage series-connected 5A or 13X molecular sieves at 25 °C. Adsorption pressure: 3 MPa, desorption pressure: 0.1 MPa.

9. The method for producing hydrogen from coke oven gas based on the electrochemical reduction of CO2 technology according to claim 8, wherein: The third stage: In the carbon cycle of coke oven gas, in Step 2-5, the pressure is reduced to release the adsorbed gas. Among them, 5% of the released gas is electrochemically reduced using a nickel supramolecular tube as a catalyst 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. The method for producing hydrogen from coke oven gas based on the electrochemical reduction of CO2 technology according to claim 8, characterized in that: The third stage: In the carbon cycle of coke oven gas, in Step 2-5, the pressure is reduced to release the adsorbed gas. Among them, 95% of the released gas uses a nickel supramolecular tube as a catalyst.

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