An apparatus and method for generating power using biogas in a solid oxide fuel cell

Abstract

The application discloses a device and method for generating electricity by using biogas in a solid oxide fuel cell, which comprises an anode gas conveying pipeline connected with an anode gas inlet of the solid oxide fuel cell, a cathode gas conveying pipeline connected with a cathode gas inlet of the solid oxide fuel cell, a biogas blower arranged on the anode gas conveying pipeline and used for pressurizing anode gas, a desulfurization device arranged on the anode gas conveying pipeline and used for removing sulfur impurities, a pre-reformer arranged on the anode gas conveying pipeline and used for adjusting gas composition, and a gas heat exchanger arranged on the anode gas conveying pipeline and used for heating gas, an air blower arranged on the cathode gas conveying pipeline and used for pressurizing cathode gas, and an air preheater arranged on the cathode gas conveying pipeline and used for heating air. The device and method provided by the application can improve biogas power generation efficiency and efficiently utilize biogas resources.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of solid oxide fuel cell, and particularly relates to a device and method for generating electricity by using marsh gas in solid oxide fuel cell. BACKGROUND

[0002] Marsh gas is a combustible gas produced by organic matter under anaerobic environment, suitable temperature and pH value through microbial fermentation. It is named because it was first discovered in marshes. Marsh gas belongs to secondary energy and is renewable energy. In addition to direct combustion for cooking, drying agricultural and sideline products, heating, lighting and gas welding, marsh gas can also be used as fuel for internal combustion engine and for producing chemical raw materials such as methanol, formaldehyde and carbon tetrachloride. The slurry and sediment discharged after fermentation by marsh gas device contain rich nutrients and can be used as fertilizer and feed.

[0003] The composition of marsh gas varies greatly due to the influence of factors such as types of organic matter, environmental conditions and types of microorganisms. The composition of conventional marsh gas is shown in Table 1.

[0004] Table 1 Typical marsh gas composition

[0005]

[0006] Methane, the main component of marsh gas, is an ideal gaseous fuel. It is colorless and odorless and can be burned after mixing with appropriate amount of air. The calorific value of pure methane is 35900 kJ / m 3 , and the calorific value of marsh gas is about 20800-23600 kJ / m 3 . That is, 1 m 3 of marsh gas can produce heat equivalent to 0.7 kg of anthracite coal after complete combustion. Compared with other fuel gases, marsh gas has better anti-explosion performance, and power generation with marsh gas has the advantages of creating benefits, energy saving, safety and environmental protection, etc. It is a good clean fuel. 3

[0007] In recent years, with the development of China's economy, the demand for energy is increasing. However, China's dependence on foreign oil has exceeded 70%, and the dependence on foreign natural gas has exceeded 40%. The current situation of dependence on foreign countries cannot meet the most basic energy security needs. By 2025, renewable energy will account for more than 50% of China's total installed power generation capacity. However, there are problems such as the intermittency of wind energy and solar energy and the uneven distribution of wind energy and solar energy resources in China. Therefore, developing distributed power generation technology to improve energy utilization efficiency will become a new trend in the future.

[0008] Solid oxide fuel cell (SOFC) is a new generation of clean and efficient power generation technology. Through electrochemical reaction, chemical energy is directly converted into electrical energy. In the process of energy conversion, there is no combustion and mechanical movement, and the energy conversion efficiency is high. The power generation efficiency of SOFC can reach 50% to 70%, and the waste heat is high, and the power generation efficiency can exceed 80% combined with cogeneration. SOFC is not only high in power generation efficiency, but also wide in fuel selectivity, and natural gas, oil gas, biogas, hydrogen, coal gas and methanol can be used as raw materials. Therefore, SOFC is considered as a very promising fuel cell.

[0009] At present, biogas power generation mainly adopts single fuel biogas generator set and dual fuel biogas-diesel generator set, but these traditional power generation methods convert chemical energy into heat energy and mechanical energy and then into electrical energy. At present, the power generation efficiency of gas turbine in advanced countries exceeds 40%, and that in China is slightly more than 30%; the power generation efficiency of gas internal combustion engine power generation device is 30%-50%; the power generation efficiency of steam turbine is about 20%. As can be seen, the low power generation efficiency of internal combustion engine and gas turbine causes the problem of energy utilization waste. With the progress of technology, the power generation efficiency of internal combustion engine and gas turbine has been improved, but the trend is to increase first and then tend to be stable with the increase of scale, which is more suitable for large power station. However, large-scale centralized power generation faces problems such as high cost, large occupation and power distribution loss. The output power of SOFC is flexible, the power generation efficiency is high, and can reach more than 65%, which is very suitable for distributed energy, and is the future national development direction. Moreover, the power generation efficiency of SOFC cogeneration combined power generation technology is much higher than that of gas turbine combined use, about 70%-90%. In view of the power generation efficiency and output power, SOFC and SOFC cogeneration power generation technology have obvious advantages. SUMMARY

[0010] In view of the problems in the prior art biogas power generation, the present application provides a device and method for generating power by using biogas in solid oxide fuel cell, which improves the biogas power generation efficiency and efficiently utilizes the biogas resources. In addition, the method for providing the water-carbon ratio and temperature required in biogas reforming is improved. The existing SOFC system mostly adopts steam generator to directly adjust the water-carbon ratio, while the present application adopts the method of anode tail gas circulation, and in addition to using steam generator to supplement water during the initial period of driving, subsequent operation meets the demand of water-carbon ratio without external water. On the other hand, the present application adopts the method of radiation to heat the reformer and the gas before reforming, which reduces the use of heat exchanger, optimizes the volume and cost of the equipment.

[0011] According to the first embodiment of the present application, there is provided a device for generating electricity by using biogas in a solid oxide fuel cell, which comprises an anode gas delivery pipe connected to an anode gas inlet of a solid oxide fuel cell stack, a cathode gas delivery pipe connected to a cathode gas inlet of the solid oxide fuel cell stack, the anode gas delivery pipe being provided with, in sequence along the delivery direction of the anode gas, a biogas blower for pressurizing the anode gas, a desulfurization device for removing sulfur impurities, a pre-reformer for adjusting the composition of the gas, a gas-fired heat exchanger for heating the gas, the cathode gas delivery pipe being provided with, in sequence along the delivery direction of the cathode gas, an air blower for pressurizing the cathode gas, an air preheater for heating the air, a steam feed pipe connected to the inlet of the pre-reformer or a water feed pipe connected to the inlet of the pre-reformer via a steam generator.

[0012] Further, the anode tail gas output pipe of the solid oxide fuel cell stack is divided into a first branch pipe and a second branch pipe after heat exchange in the gas-fired heat exchanger, the first branch pipe is connected to the anode tail gas inlet of the combustor, the second branch pipe is connected to the gas inlet of the pre-reformer via a temperature-resistant circulating device, the cathode tail gas output pipe of the solid oxide fuel cell stack is connected to the cathode tail gas inlet of the combustor, the cathode tail gas is combusted with the anode tail gas in the combustor to generate heat, and the combustion tail gas output pipe of the combustor is connected to the outside of the system after the air preheater and the tail gas heat recovery device (high-temperature medium passage) in sequence.

[0013] Further, the gas-fired heat exchanger is one of a plate-and-shell heat exchanger or a plate-and-fin heat exchanger, preferably, the low-temperature medium passage inlet of the gas-fired heat exchanger is connected to the anode gas delivery pipe, and the high-temperature medium passage outlet is connected to the first branch pipe and the second branch pipe via pipes respectively.

[0014] Further, the pre-reformer is a tubular reactor, for example, a tube filled with catalyst, then the anode gas delivery pipe is connected to the tube inlet, and the outlet of the pre-reformer is connected to the anode inlet of the solid oxide fuel cell stack via the gas-fired heat exchanger, the temperature of the pre-reformer is maintained by heat radiation generated by the solid oxide fuel cell stack and the combustor.

[0015] Further, the air preheater is one of a plate-and-shell heat exchanger or a plate-and-fin heat exchanger, the combustion tail gas output pipe of the combustor is connected to the high-temperature medium passage inlet of the air preheater, and the cathode gas delivery pipe after the air blower is connected to the low-temperature medium passage inlet of the air preheater.

[0016] Further, the tail gas heat recovery device is one of a plate-and-shell heat exchanger or a plate-and-fin heat exchanger, the high-temperature medium passage outlet of the air preheater is connected to the high-temperature medium passage inlet of the tail gas heat recovery device, the low-temperature medium passage inlet of the tail gas heat recovery device is connected to the cold water input pipe, the low-temperature medium passage outlet is connected to the hot water output pipe, and the tail gas heat recovery device recovers the heat of the combustion tail gas to heat the domestic water.

[0017] Further, the temperature resistant circulating device is one of a temperature resistant circulating blower or a Venturi tube. The second branch of the anode tail gas output pipeline is connected to the inlet of the reformer after the temperature resistant circulating device and the anode gas pipeline after the desulfurization device; the first branch of the anode tail gas output pipeline is connected to the inlet of the burner after heat exchange, so that a part of the anode tail gas is mixed with the fuel stream from outside and enters the reformer after the circulating device; the rest of the anode tail gas enters the burner to burn and release heat. The temperature resistant circulating device is used to recycle the unused fuel and water vapor to the reformer to adjust the water-carbon ratio in the reforming process, improve the utilization rate of fuel, and avoid the problem of carbon deposition in the reformer and prevent thermal cracking of the fuel cell.

[0018] Further, the radiant heating part is applied to pre-reformer and gas heating before reforming, and the structure of the solid oxide fuel cell stack, the burner and the pre-reformer is annular, wherein the pre-reformer is an arc-shaped body, the burner is located inside the pre-reformer, and the solid oxide fuel cell stack is located outside the pre-reformer, i.e. the pre-reformer and part of the inlet pipeline (i.e. the part of the anode gas pipeline between the outlet of the desulfurization device and the inlet of the pre-reformer close to the inlet of the pre-reformer) are located between the solid oxide fuel cell stack and the burner, preferably, the distance between the solid oxide fuel cell stack and the pre-reformer is generally 0.2-1.0 m, preferably 0.2 m-0.5 m, preferably 0.3 m-0.4 m, and the distance between the pre-reformer and the burner is generally 0.2-0.8 m, preferably 0.2 m-0.4 m, preferably 0.25 m-0.35 m; the distance between the solid oxide fuel cell stack and the burner is 0.3-1.2 m, preferably 0.4-0.9 m, preferably 0.55-0.75 m.

[0019] Preferably, the outer wall of the pre-reformer and part of the inlet pipeline is made of a material with good heat absorption effect (such as metal material such as steel or copper) to collect and conduct heat.

[0020] Preferably, an outer cover is provided outside the overall structure of the solid oxide fuel cell stack, the pre-reformer and part of the inlet pipeline, and the burner, which is preferably made of heat-insulating material and is in a sealed state to prevent heat loss.

[0021] The desulfurization device, the pre-reformer, etc. can use those known in the art.

[0022] The cathode feed gas is provided by a fuel supply unit. The biogas is de-dusted and fed into a desulphurization unit R102 via a blower C101. The fuel gas required for power generation is obtained by desulphurization at ambient temperature (sulphur content is as low as 0.1 ppm or less). The fuel gas is mixed with a portion of the anode exhaust gas from the anode of the solid oxide fuel cell stack (i.e. "recycle gas"), preheated by radiation of heat generated by the solid oxide fuel cell stack and the combustor A101, and fed into a pre-reformer. The heat generated by the solid oxide fuel cell stack and the combustor is used to maintain the required temperature (e.g. 400-500°C) for the reforming. The pre-reformed gas is fed into the anode of the solid oxide fuel cell stack after being heated to a temperature of 600-750°C (e.g. about 700°C) by a gas heat exchanger.

[0023] The steam generator is a movable device. Its main function is to adjust the steam to carbon ratio of the fuel gas during the initial start-up of the system. If the steam to carbon ratio is too low, the pre-reforming catalyst will coke. If the steam to carbon ratio is too high, the pre-reforming will be very safe, but the cell voltage will drop and the anode degradation rate will increase.

[0024] According to a second embodiment of the present application, there is provided a method of generating power from biogas using the above-described apparatus, the method comprising:

[0025] (1) The biogas is de-dusted and pressurized to 3-10 kPa (further 4-8 kPa, e.g. about 6 kPa) by a biogas blower, and then fed into a desulphurization unit. The fuel gas required for power generation is obtained by desulphurization at ambient temperature (sulphur content is as low as 0.1 ppm or less). The fuel gas is preheated to 200-350°C (further 250-320°C, e.g. about 300°C) by radiation of heat from the solid oxide fuel cell stack and / or the combustor. Steam is fed into the system by a steam generator at the beginning of the reaction, and then mixed with recycle gas (a portion of the anode exhaust gas from the anode of the solid oxide fuel cell stack). The volume ratio of the fuel gas to the recycle gas can be 0.3-1.5:1, preferably 0.4-1.2:1. The steam to carbon ratio is adjusted to 1.5-3:1 (further 1.8-2.5:1, preferably about 2:1), and then the gas is fed into a pre-reformer. The reforming temperature is maintained by radiation of heat from the solid oxide fuel cell stack and the combustor. The temperature is 350-500°C (further 420-480°C, e.g. about 450°C). The pre-reformer is packed with a catalyst comprising nickel and lanthanum. The main components of the catalyst are Ni: 16-19%, and La: 2-5%. The pre-reformed gas is heated to 600-750°C (further 650-710°C, e.g. about 700°C) by a gas heat exchanger, and then fed into the anode of the solid oxide fuel cell stack.

[0026] (2) Air is compressed by an air blower to 3-10 kPa (preferably 6 kPa) and fed into an air preheater, and the high-temperature gas after being combusted by a combustor is preheated to 600-750 °C (further 650-720 °C, for example about 700 °C) and then fed into the cathode of the solid oxide fuel cell stack, and the air and the fuel gas at the anode inside the solid oxide fuel cell stack undergo electrochemical reaction. The volume ratio of the air to the pre-reformer outlet gas is 7-12: 1, further 8-11: 1, and more further 9-10: 1, for example the volume ratio of the air to the pre-reformer outlet gas at 700 °C is 9: 1.

[0027] (3) The anode tail gas output from the anode of the solid oxide fuel cell stack has a pressure of about 1-5 kPa (further 2-4 kPa, for example about 3 kPa) and a temperature of 700-800 °C (further 730-770 °C, for example about 760 °C), and the gas is cooled to 450-650 °C (further 500-600 °C, preferably 550 °C) by a gas heat exchanger and then divided into two parts, 20%-60% by volume (preferably 25-55% by volume, 30-50% by volume, 35-45% by volume or 40% by volume) of the anode tail gas is mixed with the fuel gas after being circulated by a temperature-resistant circulating device, and the remaining part of the anode tail gas is mixed with the cathode tail gas (generally about 700-850 °C, further 720-800 °C, for example about 760 °C, and the pressure is 1-6 kPa, for example about 3 kPa) and fed into the combustor for combustion, and the combustor outlet temperature is 700-1000 °C (further 750-900 °C, for example about 850 °C), and the combustion tail gas output from the combustor is cooled to 100-200 °C (further 120-180 °C, for example about 130-150 °C) by transferring heat to the air in the air preheater, and then the heat is recovered by a tail gas heat recovery device, and the temperature is reduced to 40-60 °C (further 45-55 °C, for example about 50 °C), and then the gas is discharged from the system by a pipeline.

[0028] Further, the composition of the biogas in step (1) is the general composition in the art, which is CH4: 50-70%, further 55-67% or 58-65%, for example 62%, CO2: 30-45%, further 33-40% or 35-39%, for example about 37%, N2: 0.1-2%, further 0.2-1.5% or 0.3-0.8%, for example about 0.5%, CO: 0.1-2%, further 0.2-1.5% or 0.3-0.8%, for example about 0.4%, other components: 0.01-0.5%, for example about 0.1%; the unit is mol%.

[0029] Further, the gas composition after pre-reforming in step (1) is CH4: 10.6-25%, further 12-20% or 15-19%, for example about 17.37%, H2: 12-26%, further 15-22% or 16-19%, for example 17.24%, CO2: 15-30%, further 18-24% or 19-23%, for example about 22.77%, N2: 0.15-0.42%, further 0.20-0.35% or 0.21-0.30%, for example about 0.21%, CO: 0.5-2.3%, further 0.6-2.0 or 0.8-1.5%, for example about 1.23%, H2O: 30-56%, further 35-48% or 38-43%, for example about 41.18%, in mol%.

[0030] Further, the anode off-gas composition in step (3) is CH4: 3.2-4.5%, further 3.5-4% or 3.6-3.9%, H2: 3.0-5.0%, further 3.6-4.2% or 3.8-4.0%, CO2: 18-32%, further 20-30% or 22-28%, N2: 0.10-0.40%, further 0.15-0.2% or 0.16-0.19%, CO: 1.5-5.0%, further 2-3% or 2.2-2.8%, H2O: 55-72%, further 60-70% or 62-68%, in mol%;

[0031] The cathode off-gas composition is O2: 10-27%, further 15-22% or 16-20%, for example about 18.82%, N2: 73-90%, further 75-85% or 78-82%, for example about 81.18%, in mol%.

[0032] Further, the combustion off-gas composition in step (3) is CO2: 2.0-5.0%, further 2.2-3.5% or 2.5-3%, for example about 2.72%, N2: 60-82%, further 70-80% or 72-78%, for example about 74.75%, H2O: 3-10.0%, further 4-6.5% or 4.2-6.2%, for example about 6.05%, O2: 12-25%, further 15-20% or 16-19%, for example about 16.48%, in mol%.

[0033] Further, the reaction temperature of the solid oxide fuel cell group is 700-800 DEG C; the pressure resistance of the solid oxide fuel cell group is small, and the operation environment is low pressure, and the inlet pressure of the cathode gas and the anode gas of the solid oxide fuel cell group is 1-5 kPa; in addition, due to the special design structure and operation condition of the solid oxide fuel cell, the fuel utilization rate is 75%-85%, and the utilization rate is too high, which can make the anode of the battery in a high oxidation environment, and the service life of the anode of the battery is damaged; and when the utilization rate is too low, the power generation efficiency is reduced, and the air-fuel ratio is designed to be 20-50 according to the system heat balance.

[0034] In the present application, "optionally" means with or without subsequent operation.

[0035] The beneficial effects of the present application are:

[0036] The device of the present application efficiently, stably and cleanly utilizes the CH4 rich in biogas, realizes efficient and clean utilization of energy, and makes the resources rational. Meanwhile, the whole process is simple, the cost of fixed equipment is reduced, the low pressure operation condition reduces the requirement for the pressure resistance of the reactor, and indirectly reduces the investment cost. The water supplement of the present application is recycled water generated by the system, and only part of the water needs to be added at the initial stage, and the whole system is balanced at the later stage. The present application adopts the method of radiation heating, and the structure is simple, space is saved, and the heat recovery can be better realized. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 Fig. 1 is a schematic diagram of a device for generating electricity by using biogas in a solid oxide fuel cell according to the present application.

[0038] Figure 2 Fig. 2 is a configuration diagram of a solid oxide fuel cell group, a burner and a pre-reformer, wherein Figure 2 Fig. 2(a) is a front view, and Fig. 2(b) is a top view.

[0039] Reference signs:

[0040] L1- anode gas delivery pipe, L2- anode tail gas output pipe, L3- first branch pipe, L4- second branch pipe, L5- cathode gas delivery pipe, L6- cathode tail gas output pipe, L7- combustion tail gas output pipe, L8- domestic cold water input pipe, L9- domestic hot water output pipe.

[0041] C101- biogas blower, R102- desulfurization device, E102- fuel gas heat exchanger, R101- pre-reformer, C102- air blower, SOFC- solid oxide fuel cell group, C103- temperature-resistant circulating device, A101- burner, E101- air preheater, E103- tail gas heat recovery device, A102- steam generator. DETAILED DESCRIPTION

[0042] The application is further illustrated by the following figures and examples.

[0043] As Figure 1 shown, the application provides a device for power generation by biogas in solid oxide fuel cell group SOFC, which comprises anode gas delivery pipeline L1 connected with anode gas inlet of solid oxide fuel cell group SOFC, cathode gas delivery pipeline L5 connected with cathode gas inlet of solid oxide fuel cell group, biogas blower C101 for pressurizing anode gas, desulfurization device R102 for removing sulfur impurities, pre-reformer R101 for adjusting gas composition, gas heat exchanger E102 for heating gas, arranged in sequence along the delivery direction of anode gas on anode gas delivery pipeline L1, air blower C102 for pressurizing cathode gas, air preheater E101 for heating air, arranged in sequence along the delivery direction of cathode gas on cathode gas delivery pipeline L5.

[0044] Anode tail gas output pipeline L2 of solid oxide fuel cell group SOFC is divided into first branch pipeline L3 and second branch pipeline L4 after cooling by gas heat exchanger, second branch pipeline L4 is connected with gas inlet of pre-reformer R101 after passing through temperature-resistant circulating device C103, first branch pipeline L3 is connected with anode tail gas inlet of combustor A101, cathode tail gas output pipeline L6 of solid oxide fuel cell group SOFC is connected with cathode tail gas inlet of combustor A101, cathode tail gas and anode tail gas (for example, the volume ratio of cathode tail gas to anode tail gas is 5-7:1, further about 6:1) are combusted in combustor A101 (for example, the combustion temperature is 800-900℃, further about 850℃) to produce heat, combustion tail gas output pipeline L7 of combustor A101 is output to the outside of the system in sequence after passing through air preheater E101 and tail gas heat recovery device E103, preferably, second branch pipeline L4 is connected with gas inlet of pre-reformer R101 after passing through temperature-resistant circulating device C103 and merging with anode gas delivery pipeline L1, steam feeding pipeline is connected with inlet of pre-reformer R101 or water feeding pipeline is connected with inlet of pre-reformer R101 through steam generator A102.

[0045] Gas heat exchanger E102 is one of plate-and-shell heat exchanger or plate-and-fin heat exchanger, the inlet of low-temperature medium channel is connected with anode gas delivery pipeline, the outlet of high-temperature medium channel is connected with first branch pipeline L3 and second branch pipeline L4 through pipeline.

[0046] The pre-reformer R101 is a tubular reactor, the inside of which is filled with catalyst, and the anode gas delivery pipe is connected to the inlet of the tube side. The gas after the pre-reformer is heated by the gas heat exchanger E102 and then enters the anode of the solid oxide fuel cell stack SOFC. The temperature of the pre-reforming is maintained by the heat radiation generated by the solid oxide fuel cell stack SOFC and the burner A101.

[0047] The air pre-heater E101 is one of a plate and shell heat exchanger or a plate and fin heat exchanger. The combustion tail gas output pipe L7 of the burner A101 is connected to the high temperature medium channel inlet of the air pre-heater E101, and the cathode gas delivery pipe L5 is connected to the low temperature medium channel inlet of the air pre-heater E101.

[0048] The tail gas heat recovery device E103 is one of a plate and shell heat exchanger or a plate and fin heat exchanger. The combustion tail gas output pipe L7 of the burner is connected to the high temperature medium inlet of the tail gas heat recovery device E103, the low temperature medium inlet of the tail gas heat recovery device E103 is connected to the domestic cold water input pipe L8, and the low temperature medium outlet is connected to the domestic hot water output pipe L9. The tail gas heat recovery device E103 recovers the heat of the combustion tail gas to heat domestic water.

[0049] The temperature resistant circulating device C103 is one of a temperature resistant circulating blower or a Venturi tube, which is used to circulate the anode tail gas to the pre-reformer R101.

[0050] As shown in Figure 2 The solid oxide fuel cell stack SOFC, the burner A101 and the pre-reformer R101 are arranged in a ring shape. The pre-reformer R101 is an arc-shaped body, the burner A101 is located inside the pre-reformer, and the solid oxide fuel cell stack SOFC is located outside the pre-reformer. The pre-reformer and part of the inlet pipe (i.e. the part of the anode gas delivery pipe between the outlet of the desulfurization device and the inlet of the pre-reformer) are located between the solid oxide fuel cell stack and the burner. Preferably, the distance between the solid oxide fuel cell stack and the pre-reformer is generally 0.2-0.5m, preferably 0.3-0.4m, and the distance between the pre-reformer and the burner is generally 0.2-0.4m, preferably 0.25-0.35m. The distance between the solid oxide fuel cell stack and the burner is 0.4-0.9m, preferably 0.55-0.75m. The outer wall of the pre-reformer and part of the inlet pipe is preferably made of a material with good heat absorption effect (such as a metal material such as steel or copper) to collect and conduct heat.

[0051] An outer cover, preferably made of thermal insulation material, and preferably in a sealed state, is provided outside the solid oxide fuel cell stack, the pre-reformer and its partial inlet pipe, and the burner monolithic structure, for thermal insulation and preventing heat loss to the outside. The reforming temperature and gas temperature can then be adjusted by changing the distance between the components.

[0052] Example 1

[0053] (1) Biogas (composition: CH4: 62%, CO2: 37%, N2: 0.5%, CO: 0.4%, others: 0.1%; unit in mol%) after dust removal is pressurized by a biogas blower to 6 kPa, and then enters a desulfurization device along a pipeline, and a fuel gas (sulfur content as low as 0.1 ppm or less) required for power generation is obtained by normal temperature desulfurization. The fuel gas is preheated to about 300°C along a pipeline by radiation, and water is supplemented to a water-carbon ratio of 2:1 by a steam generator at the beginning of the reaction, and then mixed with a circulating gas (part of the anode tail gas output from the solid oxide fuel cell stack, and the volume ratio of the fuel gas to the circulating gas from the desulfurization device is about 0.64:1), and then enters a pre-reformer for reforming. The pre-reformer and its partial inlet pipe are arranged between the solid oxide fuel cell stack and the burner, and the radiation heat generated by the solid oxide fuel cell stack and the burner is used to maintain the reforming temperature at about 450°C. The catalyst filled in the reformer is a nickel-based catalyst, and the main components are Ni: about 18%, and La: about 2%. After the pre-reforming of the gas (including CH4: 17.37%, H2: 17.24%, CO2: 22.77%, N2: 0.21%, CO: 1.23%, H2O: 41.18%), the gas is heated to about 700°C by a gas heat exchanger, and then enters the anode of the solid oxide fuel cell stack;

[0054] (2) Air is pressurized by an air blower to 6 kPa, and then enters an air preheater, and is preheated to 700°C by the high-temperature gas after combustion of the burner, and then enters the cathode of the solid oxide fuel cell stack. The air and the pre-reforming outlet gas have a volume ratio of about 9:1, and the air and the fuel gas of the anode in the solid oxide fuel cell stack undergo an electrochemical reaction.

[0055] (3) The anode off-gas (pressure 3 kPa, temperature 760 °C, including CH4: 3.72%, H2: 3.98%, CO2: 27.15%, N2: 0.16%, CO: 2.15%, H2O: 62.84%) output from the anode of the solid oxide fuel cell stack is cooled to 550 °C by a gas heat exchanger and then divided into two parts, one part is mixed with fuel gas after being treated by a temperature-resistant circulating device, and the other part of the anode off-gas is mixed with the cathode off-gas (including: O2: 18.82%, N2: 81.18%, the pressure of the cathode off-gas is 3 kPa, and the temperature is 760 °C) and then sent into a combustor for combustion, the temperature of the outlet of the combustor is 850 °C, the combustion off-gas (including CO2: 2.72%, N2: 74.72%, H2O: 6.05%, O2: 16.51%) output from the combustor is cooled to 150 °C by an air preheater to transfer heat to air, and then the heat is recovered by a tail gas heat recovery device, and the temperature is reduced to 50 °C and then discharged from the system by a pipeline.

[0056] The reaction temperature of the solid oxide fuel cell stack is 760 °C; the inlet pressures of the cathode gas and the anode gas of the solid oxide fuel cell stack are 4 kPa respectively; the fuel utilization rate of the solid oxide fuel cell is 85%, and the air-fuel ratio is designed to be 40 according to the heat balance of the system.

[0057] Example 2

[0058] (1) The biogas (composition: CH4: 64.5%, CO2: 34.5%, N2: 0.43%, CO: 0.5%, and other: 0.07%, unit: mol%) is pressurized to 8 kPa by a biogas blower after being dedusted, and then enters a desulfurization device along a pipeline to obtain fuel gas (sulfur content is as low as 0.8 ppm or less) required for power generation by normal temperature desulfurization. The fuel gas is preheated to about 320 °C along a pipeline by radiation, and the water carbon ratio is supplemented to 1.5:1 by a steam generator at the beginning of the reaction, and then mixed with circulating gas (part of the anode off-gas output from the anode of the solid oxide fuel cell stack, and the volume ratio of the fuel gas to the circulating gas is about 0.56:1) after the subsequent, and then enters a pre-reformer for reforming. The radiant heat generated by the solid oxide fuel cell stack and the combustor is used to maintain the reforming temperature at 400 °C. The catalyst filled in the pre-reformer is a nickel-based catalyst, and the main components are Ni: 17% and La: 3%. The pre-reformed gas (including CH4: 19.4%, H2: 16.71%, CO2: 20.4%, N2: 0.21%, CO: 1.20%, H2O: 42.08%) is heated to about 700 °C by a gas heat exchanger, and then enters the anode of the solid oxide fuel cell stack.

[0059] (2) air is pressurized by 8kPa by an air blower, and is sent into an air preheater, and is preheated to 700 DEG C by high-temperature gas combusted by a burner, and is sent into a cathode of a solid oxide fuel cell group, and air and fuel gas at the outlet of a pre-reformer are electrochemically reacted in the solid oxide fuel cell group, and the volume ratio of air to the gas at the outlet of the pre-reformer is about 10:1;

[0060] (3) anode tail gas (pressure 6kPa, temperature 760 DEG C, including CH4: 3.95%, H2: 4.05%, CO2: 26.03%, N2: 0.52%, CO: 2.45%, H2O: 63.0%) output from the anode of the solid oxide fuel cell group is cooled to 570 DEG C by a gas heat exchanger, and is divided into two parts, one part is mixed with fuel gas after passing through temperature-resistant circulating equipment, and the other part of the anode tail gas is mixed with cathode tail gas (including O2: 15.56%, N2: 84.44%, pressure 5kPa, temperature 760 DEG C) to be combusted in a burner, the outlet temperature of the burner is 830 DEG C, and combustion tail gas (including CO2: 2.62%, N2: 74.83%, H2O: 7.05%, O2: 15.50%) output from the burner is cooled to 130 DEG C by transferring heat to air in an air preheater, and is cooled to 45 DEG C by heat recovery in a tail gas heat recovery device, and is discharged from the system.

[0061] The reaction temperature of the solid oxide fuel cell group is 760 DEG C, the inlet pressure of cathode gas and anode gas of the solid oxide fuel cell group is 6kPa respectively, the fuel utilization rate of the solid oxide fuel cell group is 85%, and the air-fuel ratio is 35 according to the design of system heat balance.

[0062] The biogas SOFC power generation process can efficiently, stably and cleanly utilize the rich methane in the biogas, the oxidant at the cathode side of the solid oxide fuel cell directly comes from the atmosphere without pretreatment, the process is simple, the recycling of the anode tail gas greatly reduces the consumption of water, the energy is reasonably utilized, the purpose of energy saving is achieved, the pressure requirement of the equipment is low, and the fixed equipment cost is also reduced. The whole system recycles heat, basically achieves "zero loss", and the overall efficiency of fuel utilization is further improved.

[0063] The above merely describes the preferred embodiments of the present application, and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application can have various changes and modifications. Any change, modification, replacement, integration and parameter change of the embodiments within the spirit and principle of the present application, which can realize the same function without departing from the principle and spirit of the present application, falls within the protection scope of the present application.

Claims

1. An apparatus for generating electricity using biogas in a solid oxide fuel cell, characterized by comprising: It includes an anode gas delivery pipe (L1) connected with an anode gas inlet of a solid oxide fuel cell group (SOFC), a cathode gas delivery pipe (L5) connected with a cathode gas inlet of the solid oxide fuel cell group, the anode gas delivery pipe (L1) is sequentially provided with a marsh gas blower (C101) for pressurizing the anode gas, a desulfurization device (R102) for removing sulfur impurities, a pre-reformer (R101) for adjusting the gas composition, and a fuel gas heat exchanger (E102) for heating the gas along the delivery direction of the anode gas, the cathode gas delivery pipe (L5) is sequentially provided with an air blower (C102) for pressurizing the cathode gas and an air preheater (E101) for heating the air along the delivery direction of the cathode gas, a steam feeding pipe is connected with the inlet of the pre-reformer (R101) or a water feeding pipe is connected with the inlet of the pre-reformer (R101) through a steam generator; an anode tail gas output pipe (L2) of the solid oxide fuel cell group (SOFC) is divided into a first branch pipe (L3) and a second branch pipe (L4) after heat exchange through the fuel gas heat exchanger (E102), the first branch pipe (L3) is connected with the gas inlet of the pre-reformer (R101) through a temperature-resistant circulating device (C103), the second branch pipe (L4) is connected with the anode tail gas inlet of a burner (A101), a cathode tail gas output pipe (L6) of the solid oxide fuel cell group (SOFC) is connected with the cathode tail gas inlet of the burner (A101), the cathode tail gas and the anode tail gas are combusted in the burner (A101) to produce heat, a combustion tail gas output pipe (L7) of the burner (A101) is sequentially connected with the air preheater (E101) and a tail gas heat recovery device (E103) and then outputs to the outside of the system, wherein the fuel gas heat exchanger (E102) is a plate-and-shell or plate-and-fin heat exchanger. The solid oxide fuel cell group, the burner and the pre-reformer are annularly distributed, wherein the pre-reformer is an arc-shaped body, the burner is located inside the pre-reformer, and the solid oxide fuel cell group is located outside the pre-reformer, i.e. the pre-reformer and part of the inlet pipe thereof are located between the solid oxide fuel cell group and the burner, The distance between the solid oxide fuel cell group and the pre-reformer is 0.2m-0.5m, the distance between the pre-reformer and the burner is 0.2m-0.4m, and the distance between the solid oxide fuel cell group and the burner is 0.4-0.9m.

2. The apparatus for power generation using biogas in a solid oxide fuel cell according to claim 1, wherein The low-temperature medium channel inlet of the fuel gas heat exchanger (E102) is connected with the anode gas delivery pipe (L1) out of the pre-reformer (R101), and the high-temperature medium channel outlet is connected with the first branch pipe (L3) and the second branch pipe (L4) through pipes.

3. The apparatus for power generation using biogas in a solid oxide fuel cell according to claim 1, wherein The pre-reformer (R101) is a tubular reactor, the tube is filled with catalyst, the anode gas delivery pipe (L1) is connected with the tube inlet, and the outlet of the pre-reformer (R101) is connected with the anode inlet of the solid oxide fuel cell group (SOFC) through the fuel gas heat exchanger (E102).

4. The apparatus for power generation using biogas in a solid oxide fuel cell according to any one of claims 1 to 3, characterized by, The air preheater (E101) is one of plate shell or plate fin heat exchanger, the combustion tail gas output pipeline (L7) of the burner (A101) is connected with the high temperature medium passage inlet of the air preheater (E101), and the cathode gas conveying pipeline (L5) after the air blower (C102) is connected with the low temperature medium passage inlet of the air preheater (E101).

5. The apparatus for power generation using biogas in a solid oxide fuel cell according to claim 1, wherein The tail gas heat recovery device (E103) is one of plate shell or plate fin heat exchanger, the combustion tail gas output pipeline (L7) after the air preheater (E101) is connected with the high temperature medium passage inlet of the tail gas heat recovery device (E103), the low temperature medium passage inlet of the tail gas heat recovery device (E103) is connected with the domestic cold water input pipeline (L8), and the low temperature medium passage outlet is connected with the domestic hot water output pipeline (L9).

6. The apparatus for power generation using biogas in a solid oxide fuel cell according to claim 1, wherein The temperature resistant circulating device (C103) is one of temperature resistant circulating blower or Venturi tube, the second branch pipe (L4) of the anode tail gas output pipeline (L2) is connected with the anode gas conveying pipeline (L1) after the desulfurization device (R102) after the temperature resistant circulating device (C103), and then the inlet of the reformer (R101) is connected; the first branch pipe (L3) of the anode tail gas output pipeline (L2) is connected with the inlet of the burner (A101).

7. The apparatus for power generation using biogas in a solid oxide fuel cell according to claim 1, wherein The distance between the solid oxide fuel cell group and the pre-reformer is 0.3-0.4m, the distance between the pre-reformer and the burner is 0.25-0.35m, and the distance between the solid oxide fuel cell group and the burner is 0.55-0.75m.

8. The apparatus for power generation using biogas in a solid oxide fuel cell according to claim 1, wherein The outer wall of the pre-reformer and part of the inlet pipeline is made of easy heat absorbing material to collect and conduct heat.

9. The apparatus for power generation using biogas in a solid oxide fuel cell according to claim 1, wherein An outer cover is arranged outside the solid oxide fuel cell group, the pre-reformer and part of the inlet pipeline, and the burner, which is made of heat insulation material and is in a sealed state, and is used for heat preservation to prevent heat loss.

10. A method for biogas power generation by using the device according to any one of claims 1-9, which comprises: (1) the biogas is pressurized after dust removal, enters the desulfurization device to obtain fuel gas required for power generation, the fuel gas is preheated by radiation from the solid oxide fuel cell group and / or the burner, water vapor is fed at the beginning of the reaction, and then the water carbon ratio is adjusted to 1.5-3:1 by mixing with the circulating gas, the circulating gas is part of the anode tail gas output from the anode of the solid oxide fuel cell group, the volume ratio of the fuel gas to the circulating gas after the desulfurization device is 0.3-1.5:1, and then the pre-reformer is reformed, the heat generated by the solid oxide fuel cell group and the burner is used to maintain the reforming temperature by radiation, and the gas obtained by the pre-reforming is heated and then enters the anode of the solid oxide fuel cell group; (2) the air is compressed by the air blower, preheated by the air preheater, and then sent to the cathode of the solid oxide fuel cell group, and the air and the fuel gas of the anode in the solid oxide fuel cell group occur electrochemical reaction. (3) the anode tail gas output from the anode of the solid oxide fuel cell stack is divided into two parts after heat exchange, one part is mixed with the fuel gas after passing through the temperature-resistant circulating device, and the other part of the anode tail gas is mixed with the cathode tail gas and sent into the combustor for combustion, the combustion tail gas output from the combustor is sequentially guided out of the system after being cooled by the air preheater and the tail gas heat recovery device and is exhausted, wherein the fuel utilization rate of the solid oxide fuel cell is 75% to 85%.

11. The method of claim 10, wherein, In step (1), the volume ratio of the fuel gas output from the desulfurization device to the circulating gas is 0.4-1.2:1; and / or, the water-carbon ratio is adjusted to be 1.8-2.5:

1.

12. The method of claim 11, wherein, In step (1), the water-carbon ratio is adjusted to be 2:

1.

13. The method according to any one of claims 10-12, characterized in that, In step (1), the fuel gas is preheated to 200-350℃ by radiation preheating; and / or the volume ratio of the fuel gas output from the desulfurization device to the circulating gas is 0.3-1.5:1; and / or the reforming temperature in the pre-reformer is 350-500℃; and / or the pre-reformed gas includes CH4: 10.6-25%, H2: 12-26%, CO2: 15-30%, N2: 0.15-0.42%, CO: 0.5-2.3%, H2O: 30-56% in terms of mol%.

14. The method of claim 13, wherein, In step (1), the fuel gas is preheated to 300℃ by radiation preheating; and / or the volume ratio of the fuel gas output from the desulfurization device to the circulating gas is 0.64:1; and / or the reforming temperature in the pre-reformer is 450℃; and / or the pre-reformed gas includes CH4: 12-20%, H2: 15-22%, CO2: 18-24%, N2: 0.20-0.35%, CO: 0.6-2.0%, H2O: 35-48% in terms of mol%.

15. The method of claim 14, wherein, In step (1), the pre-reformed gas includes CH4: 15-19%, H2: 16-19%, CO2: 19-23%, N2: 0.21-0.30%, CO: 0.8-1.5%, H2O: 38-43% in terms of mol%.

16. The method of any one of claims 10-12, wherein, In step (2), the air is pressurized by 3-10 kPa by an air blower; and / or the air is preheated to 600-800℃ by an air preheater and then enters the cathode of the solid oxide fuel cell stack; and / or the volume ratio of the air to the pre-reformer outlet gas is 7-12:

1.

17. The method of claim 16, wherein, In step (2), the volume ratio of the air to the pre-reformer outlet gas is 8-11:

1.

18. The method of claim 17, wherein, In step (2), the volume ratio of the air to the pre-reformer outlet gas is 9-10:

1.

19. The method of any one of claims 10-12, wherein, In step (3), the outlet temperature of the combustor is 700-1000℃; and / or the combustion tail gas is cooled to 100-200℃ by the air preheater; and / or the tail gas heat recovery device cools the combustion tail gas to 40-60℃; and / or the anode tail gas includes CH4: 3.2-4.5%, H2: 3.0-5.0%, CO2: 18-32%, N2: 0.10-0.40%, CO: 1.5-5.0%, H2O: 55-72%; and / or the cathode tail gas includes O2: 10-27%, N2: 73-90%; and / or The combustion tail gas comprises CO2: 2.0-5.0%, N2: 60-82%, H2O: 3-10.0%, O2: 12-25%.

20. The method of claim 19, wherein, In step (3): the anode tail gas comprises CH4: 3.5-4%, H2: 3.6-4.2%, CO2: 20-30%, N2: 0.15-0.2%, CO: 2-3%, H2O: 60-70%; and / or The cathode tail gas comprises O2: 15-22%, N2: 75-85%; and / or The combustion tail gas comprises CO2: 2.2-3.5%, N2: 70-80%, H2O: 4-6.5%, O2: 15-20%.

21. The method of claim 20, wherein, In step (3): the anode tail gas comprises CH4: 3.6-3.9%, H2: 3.8-4.0%, CO2: 22-28%, N2: 0.16-0.19%, CO: 2.2-2.8%, H2O: 62-68%; and / or The cathode tail gas comprises O2: 16-20%, N2: 78-82%; and / or The combustion tail gas comprises CO2: 2.5-3%, N2: 72-78%, H2O: 4.2-6.2%, O2: 16-19%.

22. The method of any one of claims 10-12, wherein, The inlet pressure of the cathode gas and the anode gas of the solid oxide fuel cell stack is 1-5 kPa, respectively.

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