Biogas purification system adaptive to solid oxide fuel cell

Abstract

The invention discloses a biogas purification system adaptive to a solid oxide fuel cell. The biogas purification system comprises a treatment system, the solid oxide fuel cell, a catalytic burner, a condenser, an absorption tower, a first gas source, a second gas source and a third gas source, the system comprises a treatment system, a solid oxide fuel cell, a catalytic burner, a condenser, an absorption tower, a first gas source, a second gas source and a third gas source, non-renewable energy sources such as coal and natural gas are replaced by biogas from biomass, impurities such as sulfide, CO2, O2 and water vapor in the biogas can be efficiently removed through multi-stage deep purification, pollution is reduced from the source, and the energy consumption is reduced. And the energy structure can be promoted to be transformed to be low-carbon and clean, and the overall pressure on the ecological environment is reduced.

Description

Technical Field

[0001] This invention relates to the field of energy technology, and in particular to a biogas purification system adapted for solid oxide fuel cells. Background Technology

[0002] In the global wave of energy structure transformation towards clean energy, biogas, as a widely available biomass energy source, has become an important way to reduce dependence on fossil fuels and reduce carbon emissions through its efficient utilization. Biogas is a mixed gas produced by the anaerobic fermentation of organic matter by microorganisms. Its composition and proportion are affected by factors such as the type of raw materials, fermentation process, and fermentation stage. The gas composition and proportion are approximately as follows: methane (CH4, 50-70%), carbon dioxide (CO2, 25-45%), nitrogen (N2, 0-5%), hydrogen (H2, 0-1%), sulfides (0.01-0.5%), and also water vapor (H2O), oxygen (O2), trace amounts of ammonia, volatile organic compounds, etc. (<1%).

[0003] Solid oxide fuel cells (SOFCs), as highly efficient energy conversion devices, can convert the chemical energy of fuel into electrical energy without being limited by the Carnot cycle. SOFCs can use biogas as fuel, but various impurities in biogas (such as sulfides mainly composed of H2S, CO2, O2, and water vapor) are detrimental to the electrochemical reactions of SOFCs. Specifically, H2S can poison and degrade downstream pretreatment catalysts and internal electrode materials; CO2 reduces the calorific value of the fuel and affects the electrochemical performance of the battery; O2 may cause anode material spalling and cracking and interfere with electrochemical equilibrium; and water vapor may reduce the stability of electrolyte materials and affect the precise control of the anode reaction. All of these significantly limit the commercialization of biogas as a fuel for SOFCs.

[0004] Therefore, developing a biogas purification system adapted to SOFC to achieve efficient removal of the aforementioned impurities can not only expand the high-value utilization scenarios of biogas, but also promote the large-scale application of SOFC technology in the field of distributed energy, which has important practical significance and strategic value for building a green energy system.

[0005] CN111029628B discloses a biogas reforming power generation and purification system based on a reversible fuel cell. The system includes a biogas source, a biogas unit connected to the biogas source, a reforming unit connected to the biogas unit, and a fuel cell unit. The biogas unit includes at least a biogas purification component, a methanation component for hydrogenating biogas to produce methanate, and a methane storage device. The inlet of the biogas purification component is connected to the biogas source, the methanation component is connected to the biogas purification component, and the methanation component is connected to the methane storage device. The reforming unit includes a reforming reactor for reforming methane and water vapor to produce hydrogen, with the reformed gas inlet of the reforming reactor connected to the methane storage device. The fuel cell unit includes a reversible fuel cell with SOEC and SOFC modes. This system only involves desulfurization processes and does not disclose specific adsorbents or adsorbent regeneration procedures. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an environmentally friendly and energy-saving biogas purification system adapted to solid oxide fuel cells.

[0007] To achieve the above objectives, the present invention provides a biogas purification system adapted to a solid oxide fuel cell, comprising a processing system, a solid oxide fuel cell, a catalytic burner, a condenser, an absorption tower, a first gas source, a second gas source, and a third gas source. The first gas source is connected to the processing system, and the processing system is connected to the anode and the condenser of the solid oxide fuel cell, respectively. The third gas source is connected to the cathode of the solid oxide fuel cell, and the second gas source is connected to the anode of the solid oxide fuel cell. Both the anode and the cathode of the solid oxide fuel cell are connected to the catalytic burner.

[0008] The beneficial effects of this invention are: achieving multi-stage purification and environmental protection. The system includes a treatment system, a solid oxide fuel cell, a catalytic burner, a condenser, an absorption tower, a first gas source, a second gas source, and a third gas source. It replaces non-renewable energy sources such as coal and natural gas with biogas from biomass sources. Through multi-stage deep purification, it can efficiently remove impurities such as sulfides, CO2, O2, and water vapor from biogas, reducing pollution at the source. This is conducive to promoting the transformation of the energy structure towards low-carbon and clean energy, and reducing the overall pressure on the ecological environment.

[0009] Furthermore, the processing system includes a first processing unit, a second processing unit, and a third processing unit, which are connected in sequence. The first gas source is connected to the first processing unit, and the third processing unit is connected to the anode of the solid oxide fuel cell.

[0010] Furthermore, a first heat exchanger is connected between the first gas source and the first processing unit, a second heat exchanger is connected between the first processing unit and the second processing unit, and a third heat exchanger is connected between the second processing unit and the third processing unit.

[0011] Furthermore, it also includes a steam generator connected to a second guide pipe.

[0012] Furthermore, a first heater is provided on the second guide pipe, and the connection between the steam generator and the second guide pipe is located upstream of the first heater.

[0013] Furthermore, a second heater is connected between the third gas source and the cathode of the solid oxide fuel cell.

[0014] Furthermore, a first guide pipe is connected between the second processing unit and the third heat exchanger, and a three-way valve is installed on the first guide pipe, which is connected to the absorption tower.

[0015] Furthermore, a third guide pipe is connected between the second guide pipe and the first guide pipe, and a fourth regulating valve is provided on the third guide pipe.

[0016] Furthermore, the catalytic burner is connected to an exhaust pipe, and a first regulating valve is provided on the exhaust pipe.

[0017] Furthermore, the discharge pipe is connected to a first return pipe, which is connected to a second heat exchanger, wherein the connection between the first return pipe and the discharge pipe is located upstream of the first regulating valve.

[0018] Furthermore, it also includes a condenser, which is connected to a first delivery pipe and a second delivery pipe. The first delivery pipe is connected to a second heat exchanger, and the second delivery pipe is connected to a third heat exchanger. The third heat exchanger is connected to the outside.

[0019] Furthermore, a fourth guide pipe is connected between the first conveying pipe and the second conveying pipe, and a third regulating valve is provided on the fourth guide pipe.

[0020] Furthermore, a third conveying pipe is connected between the first conveying pipe and the first heat exchanger, and a second regulating valve is provided on the third conveying pipe.

[0021] Furthermore, the solid oxide fuel cell is provided with a first heating wire, and the catalytic burner is provided with a second heating wire. Attached Figure Description

[0022] Figure 1 This is a top view of the overall structure of the present invention.

[0023] Table 1 shows the adsorbent, reaction temperature, regeneration temperature and method for different processing units of the present invention.

[0024] Wherein, 1 is the first processing unit, 2 is the second processing unit, 3 is the third processing unit, 4 is a solid oxide fuel cell, 5 is a catalytic burner, 6 is a condenser, 7 is an absorption tower, 8 is the first heat exchanger, 9 is the second heat exchanger, 10 is the third heat exchanger, 11 is a steam generator, 12 is the first heater, 13 is the second heater, 14 is the first regulating valve, 15 is the second regulating valve, 16 is the third regulating valve, 17 is the fourth regulating valve, 18 is a three-way valve, 19 is the first heating wire, 20 is the second heating wire, 21 is the first gas source, 22 is the second gas source, 23 is the third gas source, 31 is the first guide pipe, 32 is the second guide pipe, 33 is the third guide pipe, 34 is the discharge pipe, 35 is the first return pipe, 36 is the fourth guide pipe, 41 is the first delivery pipe, 42 is the second delivery pipe, and 43 is the third delivery pipe. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] See appendix Figure 1 As shown, a biogas purification system adapted to a solid oxide fuel cell includes a processing system, a solid oxide fuel cell 4, a catalytic burner 5, a condenser 6, an absorption tower 7, a steam generator 11, a first gas source 21, a second gas source 22, and a third gas source 23. The first gas source 21 is connected to the processing system, which is connected to the anode of the solid oxide fuel cell 4. The third gas source 23 is connected to the cathode of the solid oxide fuel cell 4. The second gas source 22 is connected to the anode of the solid oxide fuel cell 4. Both the anode and cathode of the solid oxide fuel cell 4 are connected to the catalytic burner 5.

[0028] In this embodiment, the processing system includes a first processing unit 1, a second processing unit 2, and a third processing unit 3, which are connected in sequence. A first gas source 21 is connected to the first processing unit 1, and the third processing unit 3 is connected to the anode of the solid oxide fuel cell 4. A first heat exchanger 8 is connected between the first gas source 21 and the first processing unit 1, a second heat exchanger 9 is connected between the first processing unit 1 and the second processing unit 2, a third heat exchanger 10 is connected between the anodes of the second processing unit 2 and the third processing unit 3, a second gas source 22 is connected to the anode of the solid oxide fuel cell 4, and both the anode and cathode of the solid oxide fuel cell 4 are connected to a catalytic combustor 5.

[0029] In this embodiment, a second guide pipe 32 is connected between the second gas source 22 and the catalytic burner 5, and a steam generator 11 is connected to the second guide pipe 32; a first heater 12 is provided on the second guide pipe 32, and the connection between the steam generator 11 and the second guide pipe 32 is located upstream of the first heater 12; a second heater 13 is connected between the third gas source 23 and the cathode of the solid oxide fuel cell 4.

[0030] In this embodiment, a first guide pipe 31 is connected between the second processing unit 2 and the third heat exchanger 10. A three-way valve 18 is provided on the first guide pipe 31, and the three-way valve 18 is connected to the absorption tower 7.

[0031] In this embodiment, a third guide pipe 33 is connected between the second guide pipe 32 and the first guide pipe 31, and a fourth regulating valve 17 is provided on the third guide pipe 33.

[0032] In this embodiment, the catalytic burner 5 is connected to a discharge pipe 34, and a first regulating valve 14 is provided on the discharge pipe 34; the discharge pipe 34 is connected to a first return pipe 35, and the first return pipe 35 is connected to a second heat exchanger 9, wherein the connection between the first return pipe 35 and the discharge pipe 34 is located upstream of the first regulating valve 14.

[0033] In this embodiment, the condenser 6 is connected to a first delivery pipe 41 and a second delivery pipe 42. The first delivery pipe 41 is connected to the second heat exchanger 9, and the second delivery pipe 42 is connected to the third heat exchanger 10. The third heat exchanger 10 is connected to the outside.

[0034] In this embodiment, a fourth guide pipe 36 is connected between the first conveying pipe 41 and the second conveying pipe 42, and a third regulating valve 16 is provided on the fourth guide pipe 36; a third conveying pipe 43 is connected between the first conveying pipe 41 and the first heat exchanger 8, and a second regulating valve 15 is provided on the third conveying pipe 43.

[0035] In this embodiment, a first heating wire 19 is provided on the solid oxide fuel cell 4, and a second heating wire 20 is provided on the catalytic burner 5.

[0036] In this embodiment, the first gas source 21 is biogas or air, the second gas source 22 is nitrogen, the third gas source 23 is air, and the steam generator 11 is connected to a water pipe so that the water pipe delivers water to the steam generator 11 to continuously generate water vapor.

[0037] In this embodiment, a heat exchange tube is provided inside the condenser 6, and the heat exchange tube transports cooling water to exchange heat inside the condenser 6.

[0038] In this embodiment, a specific adsorbent, such as Pd / Fe2O3 / activated carbon or Pd / Fe2O3 / Al2O3, is added to the first processing unit 1 to remove oxygen (O2) and most sulfides. A specific adsorbent, such as ZnO / Al2O3 or ZnO-CuO / Al2O3, is added to the second processing unit for fine desulfurization. A specific adsorbent, such as modified 13X molecular sieve, is added to the third processing unit to remove carbon dioxide (CO2) and water vapor. Different adsorbents are adjusted to different temperatures.

[0039] In this embodiment, the specific energy conversion process is as follows: Start-up phase: Ensure that the second regulating valve 15, the third regulating valve 16, and the fourth regulating valve 17 are closed. Open and regulate the first regulating valve 14. The second gas source 22 introduces a certain flow of nitrogen (protective gas), and the third gas source 23 introduces a certain flow of air into the anode and cathode of the solid oxide fuel cell 4, respectively. At the same time, the first heater 12 heats the second gas source 22 to a suitable temperature, the second heater 13 heats the third gas source 23 to a suitable temperature, and the first heating wire 19 heats the solid oxide fuel cell stack 4 to a suitable temperature. The second heating wire 20 heats the catalytic burner to 600-800°C. The anode and cathode of the solid oxide fuel cell 4 deliver the gas to the catalytic burner 5 for combustion to produce exhaust gas. Then, by regulating the first regulating valve 14, a portion of the high-temperature exhaust gas is diverted to the second heat exchanger 9, and then sequentially enters the condenser 6. After being cooled by the condensate in the condenser 6, the exhaust gas enters the third heat exchanger 10 and is finally discharged into the atmosphere.

[0040] Operation phase: On the anode side of the solid oxide fuel cell 4, the N2 gas path is closed, and the second regulating valve 15, the third regulating valve 16, and the fourth regulating valve 17 are closed. The first regulating valve 14 is opened and regulated to start the biogas path. The first gas source 21 inputs a certain flow rate of biogas into the first heat exchanger 8, and then enters the first processing unit 1. In this unit, oxygen O2 and most of the sulfides are removed to complete the first stage of purification. The biogas purified by the first stage is transported to the second heat exchanger 9. At this time, the first return pipe 35 transports part of the high-temperature tail gas into the second heat exchanger 9. The biogas in the second heat exchanger 9 is heated to 150-250℃ by regulating the first regulating valve 14. Then, this part of the biogas enters the second treatment unit 2, where residual sulfides are removed and their concentration is reduced to below 1ppm, thus completing the second stage of purification. The biogas purified by the second stage enters the third heat exchanger 10 through the three-way valve 18. In the third heat exchanger 10, the exhaust gas flowing through the condenser 6 is cooled to room temperature, and then enters the third treatment unit 3, where CO2 and water vapor are removed, completing the third stage of purification. Biogas purified through three stages flows into the anode of the solid oxide fuel cell 4 as anode fuel. In addition, water is vaporized by the steam generator 11, heated to a suitable temperature by the first heater 12, and then flows into the anode of the solid oxide fuel cell 4. It undergoes a rapid water vapor reforming reaction with the anode fuel inside the stack to generate CO and H2. On the cathode side of the solid oxide fuel cell 4, a certain flow rate of air flows into the second heater 13, is heated to the target temperature, and then flows into the cathode of the solid oxide fuel cell 4. The cathode air undergoes an electrochemical reaction with the CO and H2 generated by the anode reforming, and then enters the catalytic combustor 5. The remaining fuel is oxidized into CO2 and H2O here, and finally discharged into the atmosphere or recycled to the second heat exchanger 9.

[0041] Regeneration Stage: After the system in this embodiment has been running for a certain period of time, the adsorbent will gradually approach adsorption saturation, at which point adsorbent regeneration can be performed; adjust to the start-up stage, open and regulate the fourth regulating valve 17, the second regulating valve 15, and the third regulating valve 16, that is, open the N2 gas path. At this time, the N2 gas path acts as a protective gas to prevent the anode material of the fuel cell stack from being oxidized; then switch the three-way valve 18 to the absorption tower 7; the first gas source 21 introduces a certain amount of air, so that the air passes through the first heat exchanger 8, the first processing unit 1, the second heat exchanger 9, and the second processing unit 2 in sequence, and flows into the absorption tower 7; during this process, by regulating the first regulating valve 14, part of the tail gas is diverted to the second heat exchanger 9, thereby heating the second processing unit 2 to the optimal regeneration temperature of 300-400℃, realizing the regeneration of the adsorbent in this unit; By adjusting the second regulating valve 15, a portion of the exhaust gas flowing out of the second heat exchanger 9 flows into the first heat exchanger 8, thereby heating the first processing unit 1 to the optimal regeneration temperature of 150-200℃, thus realizing the regeneration of the adsorbent in the unit. For the other part of the exhaust gas flowing out of the second heat exchanger 9, the proportion of gas that does not flow into the condenser 6 can be adjusted by adjusting the opening of the third regulating valve 16, thereby controlling the temperature of the hot gas flowing into the third heat exchanger 10. Combined with the adjustment of the flow rate of the cold gas flowing into the third heat exchanger 10 by the fourth regulating valve 17, the temperature of the third processing unit 3 can be controlled at the optimal regeneration temperature of 200-250℃, thereby realizing the regeneration of the adsorbent in this unit.

[0042] It is worth noting that all key nodes in the system piping of this embodiment need to be equipped with one-way valves to prevent gas backflow; temperature sensors need to be placed on the outer walls of the three processing units; temperature sensors can be selectively placed at the inlet and outlet of each heat exchanger on the hot and cold sides, so as to better adjust the temperature of the corresponding processing unit by controlling the opening of the corresponding regulating valve.

[0043] This embodiment innovatively couples the waste heat from the exhaust gas generated by the solid oxide fuel cell 4 with the temperature control of the purification unit, achieving efficient cascade utilization of energy and significantly reducing the system's additional energy consumption. During operation, the system generates high-temperature exhaust gas at 800-900℃, which would waste energy if directly emitted. However, this embodiment uses it as the core heat source, controlling the flow rate of the circulating exhaust gas by adjusting the opening of the exhaust gas outlet regulating valve, thereby controlling the temperature of the second processing unit 2 to achieve the optimal adsorption temperature. Simultaneously, during the regeneration phase, by adjusting the opening of the four regulating valves, waste heat can be precisely distributed to the first processing unit 1, the second processing unit 2, and the third processing unit 3, eliminating the need for additional electric or fuel heating devices, further reducing overall system energy consumption, extending the adsorbent's lifespan, and meeting the development requirements of low-carbon energy systems.

[0044] Table 1

[0045] Table 1 above shows the adsorbent, reaction temperature, regeneration temperature and method for different processing units in this embodiment.

[0046] In the above-mentioned processing unit, other adsorbents, not limited to those mentioned in this embodiment, can be used to process gases other than biogas, depending on the actual situation.

[0047] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any person skilled in the art can make more possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, all equivalent changes made based on the concept of the present invention without departing from the scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A biogas purification system adapted to a solid oxide fuel cell, comprising a treatment system, a solid oxide fuel cell (4), a catalytic burner (5), an absorption tower (7), a first gas source (21), a second gas source (22), and a third gas source (23), characterized in that: The first gas source (21) is connected to the processing system, which is connected to the anode of the solid oxide fuel cell (4). The third gas source (23) is connected to the cathode of the solid oxide fuel cell (4). The second gas source (22) is connected to the anode of the solid oxide fuel cell (4). Both the anode and cathode of the solid oxide fuel cell (4) are connected to the catalytic combustor (5).

2. The biogas purification system adapted for solid oxide fuel cells according to claim 1, characterized in that: The processing system includes a first processing unit (1), a second processing unit (2), and a third processing unit (3), which are connected in sequence. The first gas source (21) is connected to the first processing unit (1), and the third processing unit (3) is connected to the anode of the solid oxide fuel cell (4).

3. The biogas purification system adapted for solid oxide fuel cells according to claim 1, characterized in that: A first heat exchanger (8) is connected between the first gas source (21) and the first processing unit (1), a second heat exchanger (9) is connected between the first processing unit (1) and the second processing unit (2), and a third heat exchanger (10) is connected between the anode of the second processing unit (2) and the third processing unit (3).

4. A biogas purification system adapted for solid oxide fuel cells according to claim 1, characterized in that: It also includes a steam generator (11) connected to a second guide pipe (32).

5. A biogas purification system adapted for solid oxide fuel cells according to claim 1, characterized in that: The second guide pipe (32) is provided with a first heater (12), and the connection between the steam generator (11) and the second guide pipe (32) is located upstream of the first heater (12).

6. A biogas purification system adapted for solid oxide fuel cells according to claim 1, characterized in that: A first guide pipe (31) is connected between the second processing unit (2) and the third heat exchanger (10). A three-way valve (18) is provided on the first guide pipe (31), and the three-way valve (18) is connected to the absorption tower (7).

7. A biogas purification system adapted for solid oxide fuel cells according to claim 1, characterized in that: A third guide pipe (33) is connected between the second guide pipe (32) and the first guide pipe (31), and a fourth regulating valve (17) is provided on the third guide pipe (33).

8. A biogas purification system adapted for solid oxide fuel cells according to claim 1, characterized in that: The catalytic burner (5) is connected to a discharge pipe (34), and a first regulating valve (14) is provided on the discharge pipe (34); the discharge pipe (34) is connected to a first return pipe (35), and the first return pipe (35) is connected to a second heat exchanger (9), wherein the connection between the first return pipe (35) and the discharge pipe (34) is located upstream of the first regulating valve (14).

9. A biogas purification system adapted for solid oxide fuel cells according to claim 1, characterized in that: It also includes a condenser (6), which is connected to a first delivery pipe (41) and a second delivery pipe (42). The first delivery pipe (41) is connected to a second heat exchanger (9), and the second delivery pipe (42) is connected to a third heat exchanger (10). The third heat exchanger (10) is connected to the outside.

10. A biogas purification system adapted for solid oxide fuel cells according to claim 1, characterized in that: A fourth guide pipe (36) is connected between the first conveying pipe (41) and the second conveying pipe (42), and a third regulating valve (16) is provided on the fourth guide pipe (36); a third conveying pipe (43) is connected between the first conveying pipe (41) and the first heat exchanger (8), and a second regulating valve (15) is provided on the third conveying pipe (43).

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