A system and method for hydrogen production by depolarized electrolysis of boiler flue gas sulfur dioxide
By using a boiler flue gas sulfur dioxide depolarization electrolysis hydrogen production system, combined with excess ammonia water absorption and depolarization electrolysis, the problems of low desulfurization efficiency, high energy consumption and unstable by-product utilization in existing technologies have been solved, achieving efficient, economical and environmentally friendly flue gas desulfurization and resource recovery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-23
- Publication Date
- 2026-06-23
AI Technical Summary
Existing technologies struggle to achieve efficient recycling of absorbents while maintaining high desulfurization efficiency, and also suffer from problems such as high energy consumption, poor equipment reliability, and unstable utilization of byproducts.
A depolarization electrolysis hydrogen production system using boiler flue gas sulfur dioxide is adopted, including an absorption tower, a diaphragm electrolyzer, and a concentration and crystallization device. After SO2 is absorbed by excess ammonia water, it is depolarized and electrolyzed to generate high-purity ammonium sulfate byproduct, and the anolyte is recycled.
It has improved SO2 absorption efficiency to over 98%, reduced energy consumption for electrolytic hydrogen production by 20%-50%, realized high-value utilization of by-products, and reduced waste liquid discharge and operating costs.
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Figure CN122256989A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of environmental protection technology, specifically to a system and method for depolarizing sulfur dioxide in boiler flue gas to produce hydrogen, which is particularly suitable for the efficient removal and resource recovery of sulfur dioxide in industrial boilers and power plant flue gas. Background Technology
[0002] Sulfur dioxide (SO2) in industrial boiler flue gas is one of the main sources of air pollution in my country, and the development of emission control technologies is of great significance to ecological and environmental protection. Currently, mainstream flue gas desulfurization technologies face the following pressing challenges: (I) Technical bottlenecks of the traditional limestone-gypsum process The contradiction between desulfurization efficiency and resource utilization: the desulfurization efficiency is usually 90%-95%, which is difficult to meet the increasingly stringent ultra-low emission requirements (SO2 emission ≤35mg / Nm³); the calcium-sulfur ratio is as high as 1.03-1.05, the limestone utilization rate is only 70%-80%, and a large amount of low-value gypsum by-products are generated (about 2.7 tons of gypsum / ton of SO2); gypsum stockpiling occupies a large amount of land resources and is prone to secondary pollution, with disposal costs as high as 30-50 yuan / ton.
[0003] The system has high energy consumption and operating costs: electricity consumption accounts for 1%-2% of the total power generation of the power plant, of which the electricity consumption of oxidation fans and circulating pumps accounts for more than 60% of the total electricity consumption of the desulfurization system; a complex wastewater treatment system is required, with 0.5-1.0 tons of wastewater generated per ton of SO2, and the treatment cost is about 50-80 yuan / ton.
[0004] The equipment has significant reliability issues: scaling, clogging, and corrosion are prone to occur inside the absorption tower, and annual maintenance costs account for 2%-3% of the equipment investment; the system has long start-up and shutdown times (≥4 hours), making it difficult to adapt to the frequent start-up and shutdown requirements of peak-shaving units; (II) Technical limitations of conventional ammonia desulfurization Ammonia escape and secondary pollution risks: Ammonia escape concentration is usually 5-20 mg / Nm³, which easily forms PM2.5 precursors (ammonium sulfate aerosol); in order to control ammonia escape, the pH value of the absorbent liquid must be strictly controlled (5.5-6.5), which makes it difficult for SO2 absorption efficiency to exceed 98%.
[0005] Low absorption liquid recycling rate: The absorption liquid recycling rate is only 50%-70%, requiring frequent replenishment of fresh water and ammonia, which increases operating costs; the ammonium sulfite oxidation process consumes a large amount of air, and the power consumption of the oxidation fan accounts for 30%-40% of the total power consumption of the system.
[0006] The quality and profitability of by-products are unstable: the purity of ammonium sulfate products is usually 95%-97%, with high impurity content, and the market price is only 500-700 yuan / ton; the crystallization process requires a large amount of steam (about 0.8-1.2 tons of steam / ton of ammonium sulfate), which increases operating costs.
[0007] (III) Shortcomings of single sulfur dioxide depolarization electrolysis technology Limited SO2 absorption efficiency: Traditional electrolytic desulfurization technology uses acidic anolyte, and the SO2 absorption efficiency is only 85%-90%; the absorption capacity of the absorbent is low, and the absorbent needs to be replaced frequently, which increases operating costs and waste discharge.
[0008] Electrolysis energy consumption still needs optimization: the anodic oxidation reaction potential is relatively high (about 1.23V), and the energy consumption for electrolysis to produce hydrogen is about 45-50kWh / kg H2; the electrode catalytic activity is insufficient, and oxygen evolution side reaction is prone to occur, which reduces current efficiency and product purity.
[0009] (iv) Comprehensive shortcomings of existing technologies Existing technologies have failed to simultaneously address the following core issues: how to achieve efficient recycling of the absorbent while maintaining high desulfurization efficiency (≥98%).
[0010] How to reduce energy consumption in the desulfurization process through electrochemical methods, while simultaneously achieving high-value utilization of by-products, and how to avoid secondary pollution problems such as ammonia escape and wastewater discharge, so as to achieve truly clean desulfurization. Summary of the Invention
[0011] The purpose of this invention is to overcome the defects of the prior art and provide a system and method for depolarizing sulfur dioxide in boiler flue gas to produce hydrogen, in order to achieve the following objectives: 1) improve SO2 absorption efficiency; 2) reduce energy consumption in the electrolysis process; 3) realize the recycling of anolyte and reduce waste liquid discharge; 4) resource utilization of by-products (such as ammonium sulfate fertilizer).
[0012] To achieve the above objectives, the present invention adopts the following technical solution: A system for depolarizing sulfur dioxide from boiler flue gas and electrolyzing it to produce hydrogen includes: Absorption tower: used to introduce boiler flue gas and absorb SO2 by contacting it with ammoniacal anolyte; Diaphragm electrolyzer: includes an anode chamber and a cathode chamber. The anode chamber is connected to an absorption tower, and the cathode chamber is isolated from the anode chamber by a cation exchange membrane. Both the anode and cathode chambers use graphite electrodes. Circulation pump: Used to return a portion of the anolyte after electrolysis to the absorption tower; Concentration and crystallization apparatus: used to concentrate and crystallize the remaining anolyte to obtain ammonium sulfate as a byproduct.
[0013] A further improvement of the present invention is that the graphite electrode adopts a porous structure to increase the reaction surface area and improve the wettability of the electrolyte.
[0014] A further improvement of the present invention is that the ammonium sulfate byproduct obtained by the concentrated crystallization has a purity of ≥99%, which meets the GB / T 535-2020 fertilizer standard.
[0015] A further improvement of the present invention is that the absorption tower adopts a countercurrent contact method.
[0016] A further improvement of the present invention is that the anode and cathode of the diaphragm electrolytic cell can be made of titanium-coated ruthenium or stainless steel electrode materials.
[0017] A method for producing hydrogen from sulfur dioxide in boiler flue gas by depolarization electrolysis, the method employing the aforementioned system for producing hydrogen from sulfur dioxide in boiler flue gas by depolarization electrolysis, includes the following steps: 1) Preparation of ammonia-based anolyte: Add excess ammonia water to the anode chamber of the electrolytic cell to form an alkaline anolyte system, and the molar ratio of excess ammonia water NH3:SO2 ≥ 2:1; 2) Flue gas SO2 absorption: Boiler flue gas is introduced into the ammonia-containing anolyte absorption tower from the boiler flue gas inlet, so that SO2 in the flue gas reacts fully with ammonia in the anolyte; 3) Depolarization electrolysis of sulfur dioxide: The anolyte after absorbing SO2 is sent to the anode chamber of the electrolytic cell for depolarization oxidation reaction. The anode chamber of the electrolytic cell is isolated from the cathode chamber of the electrolytic cell through a cation exchange membrane and undergoes a reduction reaction to generate hydrogen. The hydrogen enters the hydrogen storage device. The anode chamber, cathode chamber and cation exchange membrane of the electrolytic cell constitute the electrolytic cell. The anode of the anode chamber and the cathode of the cathode chamber are referred to as the anode and cathode of the electrolytic cell. Both the anode and cathode of the electrolytic cell are made of graphite electrode material. 4) Anode liquid recycling: Part of the anolyte after electrolysis is returned to the absorption tower to replenish ammonia water and continue to absorb SO2. The remaining part enters the concentration and crystallization device to obtain ammonium sulfate by-products, which are stored in the ammonium sulfate by-product storage device.
[0018] A further improvement of the present invention is that the concentration of the excess ammonia in step 1) is 1% to 15%.
[0019] A further improvement of this invention is that the depolarization oxidation reaction in step 3) includes the oxidation reaction of SO2: SO2 + 2H2O - 2e - = SO4² - + 4H + and SO3² - Oxidation reaction: SO3² - + H2O - 2e - = SO4² - + 2H+ .
[0020] A further improvement of the present invention is that the circulation rate of the anolyte in step 4) is 50%~95%.
[0021] A further improvement of the present invention is that the graphite electrode can undergo surface modification treatment, including doping with nitrogen and boron elements to enhance catalytic activity.
[0022] Compared with the prior art, the present invention has at least the following beneficial technical effects: 1. Comparison Table of Core Technology Advantages
[0023] II. Detailed Analysis of Economic and Technological Advantages 1. Cost-benefit comparison Invention technology: The unit SO2 removal cost is 20%-30% lower than the limestone-gypsum method and 10%-15% lower than the conventional ammonia method. The annual revenue from the byproduct ammonium sulfate can cover 60%-80% of the operating costs, and profitability can be achieved in some high-sulfur conditions. The anolyte recycling rate reaches 70%-90%, reducing fresh water consumption and wastewater treatment costs.
[0024] Traditional limestone-gypsum method: Limestone, a desulfurizing agent, is inexpensive (approximately 80 yuan / ton), but the system consumes a lot of electricity (accounting for 40%-50% of operating costs), and the byproduct gypsum has low market value, with annual revenue only covering 5%-10%. Operating costs require a wastewater treatment system, further increasing investment and operating costs.
[0025] Conventional ammonia process: The cost of the absorbent liquid ammonia is relatively high (about 2,500 yuan / ton), accounting for 50%-60% of the operating cost. The revenue from the byproduct ammonium sulfate can cover 40%-60% of the operating cost. However, ammonia escape is difficult to control, requiring the addition of a tail gas scrubbing system, which increases investment costs.
[0026] 2. Technical Performance Comparison Desulfurization efficiency and stability: This invention employs a combined process of excess ammonia absorption and depolarization electrolysis, achieving a stable SO2 absorption efficiency of over 98%, unaffected by flue gas load fluctuations. The limestone-gypsum desulfurization efficiency is affected by factors such as limestone activity and liquid-to-gas ratio, and often falls below the design value in actual operation. Conventional ammonia desulfurization efficiency can reach 99%, but ammonia escape issues cause fluctuations in actual SO2 emission concentrations.
[0027] Energy consumption and resource utilization: This invention reduces the anode potential by 0.3-0.5V through depolarization electrolysis, resulting in 20%-50% lower energy consumption for hydrogen production compared to traditional methods. The limestone-gypsum method has high power consumption for equipment such as oxidation blowers and circulating pumps, accounting for approximately 1%-2% of the total power generation of the power plant. The conventional ammonia method requires a large amount of steam for ammonium sulfate crystallization and drying, increasing operating costs.
[0028] Equipment maintenance and lifespan: The system of this invention has no scaling or clogging problems, long equipment maintenance cycle, and low annual maintenance cost; the limestone-gypsum method is prone to scaling inside the tower and pipe clogging, with annual maintenance costs accounting for 2%-3% of the investment; the conventional ammonia method has high requirements for equipment corrosion resistance, requires the use of special materials, and increases equipment investment.
[0029] III. Long-term operational value analysis Based on a flue gas treatment capacity of 400,000 Nm³ / h, an SO2 concentration of 2000 mg / Nm³, and an annual operating time of 6800 hours:
[0030] IV. Environmental and Social Benefits Carbon emission reduction contribution: This invention reduces system energy consumption, thereby reducing CO2 emissions by approximately 12,000-18,000 tons annually (calculated based on 0.98 kg CO2 per kWh of electricity). The byproduct ammonium sulfate, used to replace traditional fertilizers, can reduce carbon emissions during fertilizer production by approximately 25,000-35,000 tons per year.
[0031] Water conservation: Compared to the limestone-gypsum process, it saves approximately 120,000 to 180,000 tons of water annually; there is no wastewater discharge, avoiding water pollution and treatment costs.
[0032] Resource recycling: Achieving efficient conversion of SO2 to ammonium sulfate, with a sulfur resource recovery rate of ≥99%. The byproduct ammonium sulfate meets the GB / T 535-2020 fertilizer standard and can be directly used in agricultural production.
[0033] In summary, based on the comparative data above, this invention innovatively proposes a combined technology of "excess ammonia absorption + sulfur dioxide depolarization electrolysis," fundamentally solving the pain points of existing technologies and achieving synergistic optimization of desulfurization efficiency, energy consumption control, resource recovery, and environmental friendliness. This technology increases SO2 absorption efficiency to over 98%, reduces energy consumption for hydrogen production by electrolysis by 20%-50%, achieves an anolyte circulation rate of 70%-90%, and produces ammonium sulfate byproducts with a purity ≥99%, providing a highly efficient, economical, and environmentally friendly new solution for industrial boiler flue gas desulfurization. This invention significantly outperforms traditional limestone-gypsum methods and conventional ammonia methods in terms of economic cost, technical performance, and environmental benefits, possessing greater potential for widespread application. Attached Figure Description
[0034] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0035] Figure 1 This is a structural block diagram of a system for depolarizing sulfur dioxide in boiler flue gas to produce hydrogen by electrolysis, according to the present invention.
[0036] Explanation of reference numerals in the attached figures: 1. Boiler flue gas inlet; 2. Absorption tower; 3. Clean flue gas outlet; 4. Circulating pump; 5. Electrolytic cell anode chamber; 6. Concentration and crystallization device; 7. Ammonium sulfate by-product storage device; 8. Electrolytic cell cathode chamber; 9. Hydrogen storage device; 10. Ammonia water replenishment unit; 11. Cation membrane. Detailed Implementation
[0037] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.
[0038] In the description of this invention, it should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.
[0039] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.
[0040] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.
[0041] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.
[0042] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[0043] Example 1 like Figure 1 As shown, the present invention provides a system for depolarizing sulfur dioxide from boiler flue gas and electrolyzing it to produce hydrogen, comprising: Boiler flue gas inlet 1: Used to introduce boiler flue gas to be treated; Absorption Tower 2: Used to introduce boiler flue gas and contact it with ammonia-containing anolyte to absorb SO2, thereby achieving efficient SO2 absorption; Clean flue gas outlet 3: Emits clean flue gas after desulfurization; Diaphragm-type electrolyzer: includes an anode chamber 5 and a cathode chamber 8. The anode chamber 5 is connected to the absorption tower 2, and the cathode chamber 8 is isolated from the anode chamber 5 by a cation exchange membrane 11. Both the anode chamber 5 and the cathode chamber 8 use graphite electrodes. The cation exchange membrane 11: isolates the anode and cathode chambers, allows cations to pass through, and prevents gas mixing.
[0044] Circulation pump 4: Used to return part of the electrolyzed anolyte to the absorption tower 2; Concentration and crystallization device 6: Used to concentrate and crystallize the remaining anolyte to obtain ammonium sulfate as a byproduct.
[0045] This invention ingeniously couples boiler flue gas desulfurization (especially ammonia-based desulfurization) with water electrolysis for hydrogen production. It replaces the oxygen evolution reaction with an SO2 depolarization reaction at the anode, significantly reducing power consumption for hydrogen production. A concentration and crystallization device 6 is installed at the end of the system to convert the remaining anolyte into ammonium sulfate as a byproduct. A circulation pump 4 circulates the anolyte between the absorption tower 2 and the anode chamber 5 of the electrolytic cell. A cation exchange membrane 11 (such as a proton exchange membrane or cation exchange membrane) separates the anode and cathode chambers, with graphite electrodes on both sides. This invention integrates desulfurization and hydrogen production, eliminating the forced oxidation process of traditional desulfurization and producing both hydrogen and ammonium sulfate as products.
[0046] In this embodiment, the graphite electrode adopts a porous structure to increase the reaction surface area and improve electrolyte wettability.
[0047] In this embodiment, the ammonium sulfate byproduct obtained by concentration and crystallization has a purity of ≥99%, which meets the GB / T 535-2020 fertilizer standard.
[0048] In this embodiment, the absorption tower 2 has a diameter of 1.0~1.5m and a height of 6~8m, and adopts a countercurrent contact method.
[0049] In this embodiment, the anode and cathode of the diaphragm electrolytic cell can be made of titanium-coated ruthenium or stainless steel electrode materials.
[0050] In this embodiment, it also includes: an ammonium sulfate by-product storage device 7: for storing fertilizer-grade ammonium sulfate products; Hydrogen storage tank 9: Stores hydrogen produced by electrolysis; Ammonia replenishment unit 10: Replenishes ammonia to the circulating anolyte to maintain the concentration of the absorbent.
[0051] Example 2 like Figure 1 As shown, the present invention provides a method for producing hydrogen from boiler flue gas sulfur dioxide by depolarization electrolysis. This method uses the boiler flue gas sulfur dioxide depolarization electrolysis hydrogen production system described in Example 1, and includes the following steps: 1) Preparation of ammonia anolyte: Add excess ammonia water to the anode chamber 5 of the electrolytic cell to form an alkaline anolyte system, and the molar ratio of excess ammonia water NH3:SO2≥2:1; 2) Flue gas SO2 absorption: Boiler flue gas is introduced into ammonia anolyte absorption tower 2 from boiler flue gas inlet 1, so that SO2 in the flue gas reacts fully with ammonia in the anolyte; 3) Depolarization electrolysis of sulfur dioxide: The anolyte after absorbing SO2 is sent to the anode chamber 5 of the electrolytic cell for depolarization oxidation reaction. The anode chamber 5 of the electrolytic cell is isolated from the cathode chamber 8 of the electrolytic cell through the cation membrane 11 and undergoes a reduction reaction to generate hydrogen. The hydrogen enters the hydrogen storage device 9. The anode chamber 5, the cathode chamber 8 and the cation membrane 11 of the electrolytic cell constitute the electrolytic cell. The anode of the anode chamber 5 and the cathode of the cathode chamber 8 are referred to as the anode and cathode of the electrolytic cell. Both the anode and cathode of the electrolytic cell are made of graphite electrode material. 4) Anode liquid recycling: Part of the anolyte after electrolysis is returned to the absorption tower 2 to replenish ammonia water and continue to absorb SO2. The remaining part enters the concentration and crystallization device 6 and is concentrated and crystallized to obtain ammonium sulfate by-product, which is stored in the ammonium sulfate by-product storage device 7.
[0052] In this embodiment, the concentration of the excess ammonia in step 1) is 1% to 15%.
[0053] In this embodiment, the depolarization oxidation reaction in step 3) includes the oxidation reaction of SO2: SO2 + 2H2O - 2e - = SO4²- + 4H + and SO3² - Oxidation reaction: SO3² - + H2O - 2e - = SO4² - + 2H + .
[0054] In this embodiment, the circulation rate of the anolyte in step 4) is 50%~95%.
[0055] In this embodiment, the graphite electrode undergoes surface modification treatment, including doping with nitrogen and boron to enhance catalytic activity.
[0056] Furthermore, those skilled in the art can adjust the absorber parameters, electrode doping amount, circulation flow rate, etc., according to actual needs, for example: The diameter of the absorption tower can be adjusted to 1.0~1.5m according to the flue gas flow rate; The doping element in the graphite electrode can be replaced with boron, with a doping amount of 0.3~0.8 wt%. The flow rate of the circulating pump can be adjusted to 35~50 m³ / h according to the absorption efficiency.
[0057] All of the above adjustments fall within the protection scope of this invention.
[0058] Example 3: Flue gas desulfurization system for an industrial boiler 1. Equipment Configuration Absorption tower: Packed tower (1.5m in diameter, 8m in height), using polypropylene packing; Electrolytic cell: Diaphragm electrolytic cell (Anode material: ruthenium-coated titanium; Cathode material: stainless steel; Diaphragm: cation exchange membrane); Auxiliary equipment: circulating pump (flow rate 50 m³ / h), ammonia storage tank (capacity 10 m³), and a concentration crystallizer.
[0059] 2. Operating parameters Anode solution: initial ammonia concentration 5%, circulation rate 35 m³ / h; Flue gas parameters: SO2 concentration 2000 mg / m³, flow rate 1000 m³ / h; Electrolysis parameters: voltage 1.2V, current density 100A / m², electrolysis time 2h.
[0060] 3. Results Desulfurization rate: 98.5%; Energy consumption for hydrogen production by electrolysis: 30 kWh / kg H2 (45 kWh / kg H2 for traditional methods); Byproduct: Ammonium sulfate production of 0.5 t / d (purity 99%, in line with GB / T 535-2020 fertilizer standard).
[0061] 4. Loop Process After absorption, the anolyte is taken from the anode chamber of the electrolytic cell and undergoes electrolytic oxidation. 70% of the anolyte is returned to the absorption tower (ammonia water is added to 5%) and absorption continues. 30% of the anolyte is concentrated and crystallized to produce ammonium sulfate.
[0062] In summary, this invention solves the problems of low efficiency, high energy consumption, and high pollution of traditional desulfurization technologies by integrating excess ammonia absorption with sulfur dioxide depolarization electrolysis. It provides a new, efficient, economical, and environmentally friendly solution for industrial boiler flue gas desulfurization and has broad application prospects.
[0063] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.
[0064] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.
Claims
1. A system for depolarizing sulfur dioxide from boiler flue gas and electrolyzing it to produce hydrogen, characterized in that, include: Absorption tower (2): used to introduce boiler flue gas and absorb SO2 by contacting it with ammonia-containing anolyte; Diaphragm electrolyzer: includes an anode chamber (5) and a cathode chamber (8). The anode chamber (5) is connected to the absorption tower (2), and the cathode chamber (8) is isolated from the anode chamber (5) by a cation membrane (11). Both the anode chamber (5) and the cathode chamber (8) use graphite electrodes. Circulation pump (4): used to return part of the electrolyzed anolyte to the absorption tower (2); Concentration and crystallization device (6): used to concentrate and crystallize the remaining anolyte to obtain ammonium sulfate byproduct.
2. The system for depolarizing sulfur dioxide from boiler flue gas and electrolyzing it to produce hydrogen according to claim 1, characterized in that, The graphite electrode has a porous structure to increase the reaction surface area and improve electrolyte wettability.
3. The system for depolarizing sulfur dioxide from boiler flue gas and electrolyzing it to produce hydrogen according to claim 1, characterized in that, The ammonium sulfate byproduct obtained from the concentration and crystallization has a purity of ≥99%, which meets the GB / T 535-2020 fertilizer standard.
4. The system for depolarizing sulfur dioxide from boiler flue gas and electrolyzing it to produce hydrogen according to claim 1, characterized in that, The absorption tower (2) adopts a countercurrent contact method.
5. A system for depolarizing sulfur dioxide from boiler flue gas and electrolyzing it to produce hydrogen according to claim 1, characterized in that, The anode and cathode of the diaphragm electrolytic cell can be made of titanium-coated ruthenium or stainless steel electrode materials.
6. A method for producing hydrogen by depolarizing sulfur dioxide from boiler flue gas through electrolysis, characterized in that, This method employs the boiler flue gas sulfur dioxide depolarization electrolysis hydrogen production system as described in claim 1, and includes the following steps: 1) Preparation of ammonia anolyte: Add excess ammonia water to the anode chamber (5) of the electrolytic cell to form an alkaline anolyte system, and the molar ratio of excess ammonia water NH3:SO2≥2:1; 2) Flue gas SO2 absorption: Boiler flue gas is introduced into the ammonia anolyte absorption tower (2) from the boiler flue gas inlet (1) so that SO2 in the flue gas reacts fully with ammonia in the anolyte; 3) Depolarization electrolysis of sulfur dioxide: The anolyte after absorbing SO2 is sent into the anode chamber (5) of the electrolytic cell for depolarization oxidation reaction. The anode chamber (5) of the electrolytic cell is isolated from the cathode chamber (8) of the electrolytic cell through the cation membrane (11) and undergoes a reduction reaction to generate hydrogen. The hydrogen enters the hydrogen storage device (9). The anode chamber (5), the cathode chamber (8) and the cation membrane (11) of the electrolytic cell constitute the electrolytic cell. The anode of the anode chamber (5) and the cathode of the cathode chamber (8) of the electrolytic cell are referred to as the anode and cathode of the electrolytic cell. The anode and cathode of the electrolytic cell are both made of graphite electrode material. 4) Anode liquid recycling: Part of the anolyte after electrolysis is returned to the absorption tower (2) and SO2 is absorbed after ammonia water is added. The remaining part enters the concentration and crystallization device (6) and ammonium sulfate by-product is obtained by concentration and crystallization and stored in the ammonium sulfate by-product storage device (7).
7. The method for depolarizing sulfur dioxide in boiler flue gas to produce hydrogen by electrolysis according to claim 6, characterized in that, The concentration of the excess ammonia water mentioned in step 1) is 1%~15%.
8. The method for depolarizing sulfur dioxide in boiler flue gas to produce hydrogen by electrolysis according to claim 6, characterized in that, The depolarization oxidation reaction described in step 3) includes the oxidation of SO2: SO2 + 2H2O - 2e - = SO4² - + 4H + and SO3² - Oxidation reaction: SO3² - + H2O - 2e - = SO4² - + 2H + .
9. A method for producing hydrogen by depolarization electrolysis of sulfur dioxide in boiler flue gas according to claim 6, characterized in that, The circulation rate of the anolyte in step 4) is 50%~95%.
10. A method for producing hydrogen by depolarization electrolysis of sulfur dioxide in boiler flue gas according to claim 6, characterized in that, The graphite electrode can undergo surface modification treatment, including doping with nitrogen and boron to enhance catalytic activity.