Method and apparatus for recovering solid carbon from biogas

Abstract

To provide: a method for efficiently separating a carbon dioxide gas from a biomethane in a biogas to collect the carbon dioxide gas generated in the utilization of them by using the energy of the biogas; a method for collecting a solid-state carbon by converting the collected carbon dioxide gas into the solid-state carbon suitable for carbon stabilization or industrial utilization; and a biogas-utilization-type solid-state carbon collecting system to which these technical methods are applied.SOLUTION: A gas compressor or a gas blower for supplying a gas to a carbon dioxide separating-collecting system, or a vacuum pump or a suction blower installed on the gas flow channel side of a collected carbon dioxide is driven by directly using the generated power of a fuel battery driven by a separated and collected biomethane or a torque obtained from a gas engine or gas turbine. A solid-state carbon is collected by performing an electrolytic reduction and a carbon precipitation reaction to the separated and collected carbon dioxide gas, by using an electric power and / or cold or hot temperature obtained by using the biomethane.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for converting and recovering solid carbon from biogas generated at sewage treatment facilities, food waste treatment facilities, etc., without emitting carbon dioxide gas, and a biogas-based solid carbon recovery device to which this method is applied. [Background technology]

[0002] In order to curb and reduce carbon dioxide emissions, which is a major cause of global warming, there are high hopes for the use of biomass fuels and negative emission technology, which separates and captures carbon dioxide gas from the exhaust gas generated when using biomass fuels, transports it to an underground storage site, and injects and fixes it.

[0003] Regarding the use of biomass as fuel, the use of biogas, which is made up of 20 to 40 vol% carbon dioxide gas and biomethane through methane fermentation treatment at sewage treatment facilities, food waste treatment facilities, etc., for power generation and heat use in boilers has become widespread. To improve the stability of biogas power generation, a technology has been disclosed (Patent Document 1) in which carbon dioxide gas is separated and recovered from biogas using a separation membrane, and the carbon dioxide gas is supplied to a power generation system as high-purity biomethane gas.

[0004] On the other hand, a technology has been disclosed for separating, capturing, and immobilizing carbon dioxide gas in the exhaust gas generated during biomass combustion, in which biomass is mixed with fuel supplied to existing power generation facilities and burned directly to obtain electricity and thermal energy, and then the carbon dioxide gas in the exhaust gas generated is separated and captured, transported to an underground storage site, and injected and immobilized deep underground (Non-Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2020-165430 [Non-patent literature]

[0006] [Non-Patent Document 1] Toshiba Energy Systems & Solutions Corporation, PR TIMES (October 31, 2020) https: / / prtimes.jp / main / html / rd / p / 000000106.000032322.html DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0007] As described above, the conventional technology of Patent Document 1 improves the stability and efficiency of biogas energy use in sewage treatment facilities, food waste treatment facilities, and the like, and the conventional technology of Non-Patent Document 1 separates, recovers, and fixes carbon dioxide gas generated when biomass resources are used, thereby enabling negative emissions by reducing carbon dioxide gas in the atmosphere through recovery and fixation. However, these technologies have the following five issues.

[0008] First, all conventional technologies are carbon dioxide gas recovery technologies, but they are not technologies for recovering solid carbon that can be easily transported, stored, and used industrially as a raw material for manufacturing carbon materials. As a result, there is an issue that it is not possible to separate and recover the carbon components contained in biogas for fixation, or to effectively use the carbon as a raw material for carbon materials.

[0009] In particular, when negative emissions are achieved by separating, recovering, and immobilizing carbon dioxide gas from biogas, the recovered carbon dioxide gas must be compressed and liquefied before being transported to an underground storage site. This requires a significant amount of energy consumption to transport the carbon dioxide gas and to inject and store it deep underground. If electricity or heat derived from fossil fuels is used for this energy consumption, the net reduction in carbon dioxide emissions will decrease, and there is the issue of increased costs associated with procuring electricity and heat.

[0010] In addition, in some regions, there are no sites near the carbon dioxide gas capture site where carbon dioxide gas can be stored underground stably for the long term, and each storage site has a limit on the amount that can be injected and fixed. Therefore, once the storage amount reaches its limit, even if the carbon dioxide can be transported, it becomes impossible to fix it by underground injection.

[0011] Furthermore, in industrial use of separated and recovered carbon dioxide gas, it is common to compress and cool the recovered carbon dioxide gas and transport and use it as liquefied carbon dioxide. However, when electricity or heat derived from fossil fuels is used in this compression and cooling process, even if carbon-neutral carbon dioxide gas derived from biomass is used, there are issues such as an increase in net carbon dioxide emissions due to the emission of carbon dioxide gas generated in the manufacturing process, as well as higher procurement costs for electricity and heat.

[0012] Furthermore, if there is a high degree of dependence on external sources for the electricity and heat consumed in separating and capturing carbon dioxide gas, there is the issue that power outages in the power grid or disruptions to the fuel supply network can make it difficult to continue separating and capturing carbon dioxide gas. [Means for solving the problem]

[0013] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a method for recovering solid carbon from biogas that is useful for carbon immobilization and as a raw material for carbon materials, and a biogas-utilizing solid carbon recovery system that applies this technology.

[0014] In order to solve the above problem, the invention described in claim 1 is: The carbon dioxide gas contained in the biogas is separated and recovered using the electricity and heat obtained from the use of biogas as fuel, and the recovered carbon dioxide gas is converted into solid carbon and recovered by electrolytic reduction or carbon deposition reaction using the electricity and heat obtained from the use of biogas as fuel.

[0015] The invention described in claim 2 is Claim 1 is characterized in that the method of obtaining electricity or heat from biogas is either fuel cell power generation, gas engine power generation, gas turbine power generation, or biomethane combustion boiler, using biomethane obtained after separating and recovering carbon dioxide from biogas as fuel.

[0016] The invention described in claim 3 is In the method for utilizing biomethane as set forth in claim 2, the power generation efficiency of the power generation system is improved by supplying air or oxygen-enriched air to the fuel cell, or by supplying pure oxygen gas to the gas engine or gas turbine as an oxidant to react with the biomethane fuel, and the power and heat obtained from the utilization of the biomethane are used to cool the exhaust gas emitted during the utilization of the biomethane and remove moisture to separate and recover carbon dioxide gas, and the power and heat obtained from the utilization of the biomethane are used to convert the recovered carbon dioxide gas into solid carbon by electrolytic reduction or carbon deposition reaction, which is then recovered.

[0017] The invention described in claim 4 is The method of obtaining cold energy by using biogas in claim 1 is characterized in that it is a cold energy conversion method using an absorption chiller or adsorption chiller that is driven by the waste heat of exhaust gas generated when power is generated by the power generation method described in claim 2, or a method of obtaining cold energy by a turbo chiller that is driven by supplying electricity obtained by the power generation method described in claim 2.

[0018] The invention described in claim 5 is The method for obtaining heat by using biogas in claim 1 is characterized by heat exchange with high-temperature exhaust gas generated after power generation by the power generation method in claim 2.

[0019] The invention described in claim 6 is The method for separating and recovering carbon dioxide gas from biogas in claim 1 is characterized by being either a chemical absorption method, a physical adsorption method, or a separation membrane method.

[0020] The invention described in claim 7 is The method for recovering solid carbon from carbon dioxide gas in claim 1 is characterized in that a vessel containing high-temperature molten salt heated and maintained using renewable energy electricity obtained by the method of claim 2 is provided with an electrode for supplying the electricity, and while carbon dioxide gas separated and recovered by the method of claim 1 or claim 3 is supplied into the high-temperature molten salt, renewable energy electricity is supplied to the electrode, thereby recovering carbon dioxide gas by electrolytic reduction into solid carbon and carbon monoxide gas.

[0021] The invention described in claim 8 is The method for recovering solid carbon from carbon dioxide gas in claim 1 is characterized in that it utilizes renewable energy electricity obtained by the method in claim 2 and either water purified by condensing and recovering water vapor contained in exhaust gas generated during power generation as in claim 2 or water purified from condensed water obtained in a biogas cooling and dehumidification process, or both, and supplies the carbon dioxide gas separated and recovered by the method in claim 1 or claim 3 to an electrolytic cell, whereby the carbon dioxide gas is recovered by electrolytic reduction to carbon monoxide gas.

[0022] The invention described in claim 9 is The method for recovering solid carbon from carbon dioxide gas in claim 1 is characterized in that the carbon monoxide gas according to claim 7 or claim 8 is supplied to a gas reactor that is heated by renewable energy electricity obtained by the method according to claim 2 and is equipped with a carbon deposition plate containing a catalyst that promotes carbon deposition, thereby precipitating solid carbon, thereby converting the separated and recovered carbon dioxide gas into solid carbon and recovering it.

[0023] The invention described in claim 10 is The carbon deposition plate described in claim 9 is equipped with an ultrasonic vibrator driven by renewable energy electricity obtained by the method described in claim 2, and carbon is deposited while vibrating the carbon deposition plate at high frequency, thereby continuously depositing and recovering carbon while peeling off and removing the carbon deposited on the carbon deposition plate.

[0024] The invention described in claim 11 is The present invention is characterized in that the solid carbon deposited in the molten salt electrolysis apparatus according to claim 7 or the carbon monoxide gas reactor according to claim 9 is continuously discharged by a solid carbon discharge mechanism driven by renewable energy electricity obtained by the method according to claim 2, thereby preventing blockages due to carbon deposition in the molten salt electrolysis apparatus and the gas reactor and continuously recovering solid carbon while maintaining a stable reaction.

[0025] The invention described in claim 12 is The rotational driving force obtained from the combustion energy of biogas is directly used to rotate one or more of a gas compressor, a gas blower, a vacuum pump, or a suction blower, thereby performing one or more of the compression, suction, or air supply of the biogas to be supplied to the carbon dioxide gas separation and recovery device or the separated and recovered carbon dioxide gas.

[0026] The invention described in claim 13 is The carbon dioxide gas separation and recovery method described in claim 6 is characterized in that the temperature of the gas supplied to the carbon dioxide separation and recovery device is controlled by cold heat obtained by the method described in claim 4 or hot heat obtained by the method described in claim 5 so as to achieve the conditions most suitable for operating the separation and recovery device.

[0027] The invention described in claim 14 is The carbon dioxide gas separation and recovery method described in claim 6 is characterized in that the humidity of the gas supplied to the carbon dioxide separation and recovery system is dehumidified by cooling and condensing the supply gas with cold heat obtained by the method described in claim 4 so that the humidity of the gas supplied to the carbon dioxide separation and recovery system is at the most suitable condition for operating the separation and recovery system.

[0028] The invention described in claim 15 is The present invention is characterized by being a biogas-utilizing solid carbon recovery system to which one or more of the methods described in claims 1 to 14 are applied. [Effects of the Invention]

[0029] According to the present invention, it is possible to separate and recover carbon dioxide gas contained in biogas using electricity and heat obtained from renewable energy biogas, and to convert the recovered carbon dioxide gas into solid carbon that can be easily transported, immobilized, and used as a raw material for producing carbon materials.In addition, by covering the energy consumption involved in recovering the solid carbon with renewable energy biomethane, it is possible to increase the net carbon dioxide gas emission suppression effect and carbon dioxide gas reduction effect, and to independently recover carbon, which is the source of carbon dioxide gas in the atmosphere, via biogas, without relying on external fossil fuel procurement or power and heat supplies. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a schematic diagram showing a biogas-utilizing solid carbon recovery system according to a first embodiment of the present invention, which is composed of a carbon dioxide gas separation membrane, a hydrogen ion conductive solid oxide fuel cell power generation system, a molten salt carbon dioxide electrolytic reduction device, and a carbon deposition reactor from carbon monoxide gas. [Figure 2] FIG. 2 is a schematic diagram showing a biogas-utilizing solid carbon recovery system according to a second embodiment of the present invention, which is composed of a carbon dioxide gas separation membrane, a solid oxide fuel cell power generation system, a solid polymer membrane-type carbon dioxide electrolytic reduction device, and a carbon deposition reactor for carbon monoxide gas. [Figure 3] FIG. 10 is a schematic diagram showing a biogas-utilizing solid carbon recovery system according to a third embodiment of the present invention, which is composed of a carbon dioxide gas separation membrane, a power generation system equipped with a gas engine-driven gas compressor, a solid polymer membrane water electrolysis device, a molten salt carbon dioxide electrolytic reduction device, and a carbon monoxide gas carbon dioxide deposition reactor. [Figure 4]FIG. 10 is a schematic diagram showing a biogas-utilizing solid carbon recovery system according to a fourth embodiment of the present invention, which is composed of a carbon dioxide gas adsorption recovery device, a carbon dioxide gas suction compressor driven by a gas turbine generator, a solid polymer membrane water electrolysis device, a molten salt carbon dioxide electrolytic reduction device, and a carbon deposition reactor for carbon monoxide gas. DETAILED DESCRIPTION OF THE INVENTION

[0031] The best mode for carrying out the present invention will be described below with reference to the drawings. The scope of the present invention is defined by the claims and is not limited to the present embodiment.

[0032] (First embodiment)

[0033] First, a biogas-utilizing solid carbon recovery system according to a first embodiment of the present invention will be described with reference to FIG.

[0034] As shown in Figure 1, this system consists of biogas, a mixture of carbon dioxide and biomethane gas, generated in biogas generator 1, such as a digester gas generation tank at a sewage treatment facility or a methane fermentation treatment device for food waste. Impurities contained in the biogas, such as hydrogen sulfide and siloxane, are purified through impurity remover 2, and biogas temperature and humidity adjuster 5 adjusts the temperature and humidity of the supplied biogas based on the measurement results of biogas temperature and humidity meter 4, which measures the temperature and humidity of the biogas supplied to carbon dioxide gas separation membrane module 3, to optimize the carbon dioxide gas separation performance of carbon dioxide gas separation membrane module 3.

[0035] Furthermore, the carbon dioxide gas separated by the separation membrane module 3 is sucked by a vacuum pump 7 that is installed in the carbon dioxide gas flow path and is driven by renewable energy electricity obtained from a hydrogen ion conductive solid oxide fuel cell power generation system 6 that is driven by the biomethane separated by the separation membrane module 3 as fuel.The carbon dioxide gas is then sent to a molten salt electrolytic reduction device 8 that electrolyzes the carbon dioxide gas into solid carbon and carbon monoxide gas by supplying direct current with renewable energy electricity obtained from the power generation system 6 while supplying carbon dioxide gas into a molten salt bath, and a portion of the carbon dioxide gas separated and recovered from the biogas is recovered as solid carbon 9.

[0036] Furthermore, in the molten salt electrolytic reduction device 8, not all of the carbon dioxide gas is electrolytically reduced to solid carbon, and a portion is discharged as carbon monoxide gas. However, this is collected via a carbon monoxide gas recovery pipe 10, and a heated catalyst-based solid carbon deposition recovery device 11 is provided, which causes the carbon monoxide gas to undergo a carbon deposition reaction in a catalytic heating reaction device. As a result, solid carbon is recovered from the carbon monoxide gas as well, and all of the carbon dioxide gas separated and recovered from the biogas using a separation membrane is converted into solid carbon 9 and recovered.

[0037] In the molten salt carbon dioxide electrolysis device 8, calcium chloride is melted and maintained by heating with an electric heater 12 supplied with renewable energy electricity obtained from the power generation system 6 in a container covered with a thermal insulator, and a carbon dioxide gas reduction anode 13 made of a solid electrolyte such as zirconium oxide and a carbon dioxide gas reduction cathode 14 are inserted, which is energized as a cathode while ejecting the separated and recovered carbon dioxide gas as fine bubbles. As renewable energy electricity is supplied while carbon dioxide gas is ejected as fine bubbles into the molten salt, electrolysis occurs in the molten salt, and solid carbon precipitates and floats and accumulates on the surface of the molten salt. At the same time, some of the carbon dioxide gas turns into carbon monoxide gas, which is recovered from a carbon monoxide gas recovery pipe 10 and supplied to the heated catalyst-utilizing solid carbon deposition and recovery device 11.

[0038] Furthermore, the heated catalyst-utilizing solid carbon deposition and recovery device 11 contains catalytic components, such as nickel and iron, used for carbon deposition from carbon monoxide gas. The inner wall of the device is made up of a carbon deposition heating plate 15 equipped with an electric heater, and an ultrasonic vibrator 16 is attached to the outer wall of the device. The heating power of the electric heater and the driving power of the ultrasonic vibrator are provided by renewable energy electricity obtained from the power generation system 6. As a result, the carbon deposition heating plate is heated to a high temperature of 300 to 600°C, which is optimal for carbon deposition from carbon monoxide gas, and solid carbon is continuously deposited on the surface of the carbon deposition heating plate. At the same time, the carbon deposition plate is vibrated by the ultrasonic vibrator, causing the deposited solid carbon to peel off and accumulate at the bottom of the recovery device. This accumulated solid carbon is then transported out of the device by rotating a solid carbon discharge screw plate 17 driven by a motor, making it possible to continuously deposit and recover solid carbon from carbon monoxide gas as well.

[0039] Furthermore, in this system, the mixture of carbon dioxide gas and carbon monoxide gas discharged as anode off-gas from the anode of the power generation system 5 is returned upstream of the temperature and humidity control device 5 using the gas delivery output of a fuel gas blower driven by the electricity of the power generation system 6. This makes it possible to efficiently recover carbon dioxide gas in the exhaust gas generated when generating electricity using biomethane as fuel using the separation membrane module 3, and to return carbon monoxide gas discharged as an unreacted gas from the power generation system 6 and effectively use it as fuel gas for power generation.

[0040] Furthermore, in this system, oxygen gas discharged during the reaction process of the molten salt-based carbon dioxide electrolysis device 8 and the heated catalyst-based solid carbon deposition and recovery device 11 is recovered, mixed with the air supplied to the air electrode side of the power generation system 6, and supplied as oxygen-enriched air to the air electrode of the fuel cell power generation system, thereby activating the reaction in the fuel cell power generation system and improving the efficiency of the power generation system, thereby increasing the amount of renewable energy electricity that can be used for separating and recovering carbon dioxide gas and for converting the recovered carbon dioxide gas into solid carbon.

[0041] Furthermore, in this system, when the temperature of the biogas after impurity removal is heated in the biogas temperature and humidity adjustment device 5, the waste heat of the high-temperature air electrode off-gas discharged from the air electrode of the power generation system 6 is used to heat the biogas via a heat exchanger in the temperature and humidity adjustment device, while when it is necessary to dehumidify and cool the biogas, the cold energy obtained from the turbo chiller 18 driven by renewable energy electricity obtained from the power generation system 6 is used to cool the biogas via a cooling dehumidifier in the temperature and humidity adjustment device through which cooling water circulates, and the biogas is dehumidified by collecting condensed water, thereby In order to optimize the carbon dioxide gas separation performance in the cell, the temperature and humidity of the supply gas are adjusted before being supplied to the separation membrane module, and the exhaust heat of the air electrode off-gas is also used to heat the biogas generator 1. This means that the renewable energy electricity and cold and hot heat obtained from using the biogas are used to recover solid carbon from the biogas, thereby increasing the carbon dioxide emission suppression effect and the atmospheric carbon dioxide recovery reduction effect in solid carbon recovery using this system, and reducing dependence on electricity and heat supply from outside the system, making it possible to recover solid carbon from biogas autonomously.

[0042] With this configuration, it is possible to continuously separate and recover carbon dioxide gas from the biogas generated by the biogas generator, and furthermore, it is possible to convert both the recovered carbon dioxide gas and the carbon dioxide gas generated when the separated biomethane is used as fuel into solid carbon and recover it by utilizing renewable energy electricity and cold and hot heat obtained from using the biomethane as fuel.

[0043] Unlike carbon dioxide gas, which is difficult to transport and fix, the solid carbon obtained by the above-mentioned method is lightweight and easy to transport. In addition, by using it as a raw material for functional materials with long-term carbon fixation, such as carbon fiber, it can be used industrially while fixing carbon for a long period of time. Furthermore, by burying it underground, where oxidation reactions are less likely to occur, it becomes possible to capture carbon dioxide from the atmosphere and fix it as carbon. (Second embodiment)

[0044] Next, a biogas-utilizing solid carbon recovery system according to a second embodiment of the present invention will be described with reference to FIG.

[0045] As shown in FIG. 2 , in the system of the second embodiment, biogas supplied to a carbon dioxide gas separation membrane module 3 from biogas is pressurized and supplied by a biogas compressor 20 driven by power obtained from a solid oxide fuel cell power generation system 19, thereby separating and recovering carbon dioxide gas. The separated and recovered carbon dioxide gas is then supplied to a solid polymer carbon dioxide electrolysis device 21, and further supplied together with pure water obtained by cooling the anode off-gas of the power generation system 19 by a turbo refrigerator and condensing and recovering the water vapor in the anode off-gas and supplying it to a pure water production device 22. The generated power from the power generation system 19 is supplied as a direct current for electrolytic reduction to carbon monoxide gas, and the generated carbon monoxide gas is supplied to a heated catalyst-based solid carbon deposition and recovery device 11, whereby the carbon monoxide is gasified and then solid carbon is precipitated and recovered. This is different from the first embodiment in that point, but other features are the same as those of the first embodiment.

[0046] With this configuration, even if the gas supplied to the separation membrane module needs to be pressurized, it is possible to capture carbon dioxide gas and convert it into solid carbon using renewable energy electricity generated from biomethane. (Third embodiment)

[0047] Next, a biogas-utilizing solid carbon recovery system according to a third embodiment of the present invention will be described with reference to FIG.

[0048] As shown in Figure 3, in the system of the third embodiment, in order to compress and supply biogas to a carbon dioxide gas separation membrane module 4 from biogas, the biogas is pressurized by a gas engine 23 driven by biomethane and a biogas compressor 25 connected to the rotating shaft of the gas engine 23 via a transmission 24, so that the rotational driving force obtained by burning biomethane is directly used to compress and supply the biogas.

[0049] Furthermore, in order to facilitate the recovery of carbon dioxide gas from the exhaust gas of the gas engine by driving the gas engine using oxygen combustion, condensed water discharged when driving the biogas temperature and humidity adjustment device and the absorption chiller 26, which is driven by the exhaust heat of the gas engine, and drain water generated when the biomass fermentation tank is heated with the exhaust gas heat after driving the absorption chiller are purified and supplied to a water electrolysis device 27, which performs water electrolysis. The hydrogen gas obtained from this device is mixed with biomethane gas and effectively used as fuel gas for the gas engine, while pure oxygen gas obtained from the water electrolysis device is supplied as an oxidizing agent.

[0050] Furthermore, when the amount of electricity supplied to the water electrolysis device is insufficient to obtain the amount of pure oxygen gas required to operate the gas engine, the gas engine can be operated stably by using a system that combines solar power generation or wind power generation with storage batteries, or by receiving electricity from the power grid to make up for the shortfall.

[0051] In addition, when recovering carbon dioxide gas from gas engine exhaust gas, the exhaust gas is supplied to an absorption chiller driven by the heat of the exhaust gas to remove heat and cool the exhaust gas, and then the exhaust gas is cooled using the waste heat from heating the biogas generator, and the cold heat obtained by the absorption chiller is used to cool the exhaust gas.The exhaust gas is cooled using renewable energy heat to condense and recover moisture, and carbon dioxide gas is separated and recovered by dehumidification.This is then supplied to an electrolytic reduction device together with the carbon dioxide gas recovered from the separation membrane module, making it possible to recover solid carbon from both the carbon dioxide gas in the biogas and the carbon dioxide gas originating from biomethane. (Fourth embodiment)

[0052] Next, a biogas-utilizing solid carbon recovery system according to a fourth embodiment of the present invention will be described with reference to FIG.

[0053] As shown in Figure 4, the system of the fourth embodiment differs from the third embodiment in that it is configured by an adsorption-type carbon dioxide gas separation and recovery device 28 that uses a carbon dioxide gas adsorbent to separate and recover carbon dioxide gas from biogas, and is equipped with a carbon dioxide gas suction compressor 29 and a fuel gas compression and supply compressor 30, and a gas turbine 31 that operates by sharing a rotary drive shaft with the gas compressor.However, the system is similar to the third embodiment in that the oxygen gas required to drive the gas turbine that performs oxyfuel combustion is supplied by a water electrolysis device, and the hydrogen gas obtained from the water electrolysis device is mixed with biomethane and used as fuel for gas turbine combustion, as well as the configuration for recovering solid carbon from carbon dioxide gas in biogas and gas turbine exhaust gas.

[0054] By using the system described above, facilities that generate biogas can use the energy of the biomethane contained in the biogas to separate and recover carbon dioxide gas contained in the biogas and carbon dioxide gas in the exhaust gas generated when the biomethane is used, and can then recover the recovered carbon dioxide gas as solid carbon. [Industrial Applicability]

[0055] The present invention is not limited to the above-described embodiment. For example, the illustrated embodiment is not limited to the recovery and utilization of solid carbon, and carbon monoxide gas obtained in the process of recovering solid carbon may be recovered and utilized as an industrial raw material gas.

[0056] Furthermore, although the carbon dioxide separation membrane module illustrated in the present invention is a single stage, if a sufficient concentration of carbon dioxide gas cannot be obtained using only this separation membrane module, it is possible to form a multi-stage carbon dioxide separation membrane module by adding a second stage carbon dioxide separation membrane module to the carbon dioxide gas recovery flow path on the permeate gas side of the carbon dioxide separation membrane module to increase the concentration of the recovered carbon dioxide gas, or by combining it with a chemical absorption method in which a carbon dioxide gas absorption liquid is regenerated using heat obtained from the use of biomethane fuel, thereby separating and recovering high concentration carbon dioxide gas.

[0057] As such, the above-described embodiments are merely illustrative, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0058] 1. Biogas generator 2. Biogas impurity removal device 3. Carbon dioxide gas separation membrane module 4. Biogas Temperature and Humidity Meter 5. Biogas temperature and humidity control device 6. Hydrogen-ion conductive solid oxide fuel cell power generation system 7. Vacuum pump 8. Molten salt electrolytic reduction device 9. Solid carbon 10 Carbon monoxide gas recovery pipe 11. Solid carbon deposition recovery device 12 Electric heater 13. Carbon dioxide gas reduction anode electrode 14. Carbon dioxide gas reduction cathode electrode 15 Carbon deposition heating plate 16. Ultrasonic transducer 17. Solid carbon discharge screw plate 18. Turbo Refrigerator 19. Solid oxide fuel cell power generation system 20 Biogas Compressor 21. Solid polymer carbon dioxide electrolysis device 22...Pure water production equipment 23 Gas Engine 24. Transmission 25 Biogas Compressor 26 Absorption chiller 27...Water electrolysis equipment 28. Adsorption-type carbon dioxide gas separation and recovery device 29 Carbon dioxide gas suction compressor 30. Fuel gas compression supply compressor 31. Gas turbine

Claims

1. The method is characterized in that carbon dioxide gas contained in the biogas is separated and recovered using the electricity and heat obtained by using the biogas as fuel, and the recovered carbon dioxide gas is electrolytically reduced using the electricity obtained by using the biogas as fuel to convert it into solid carbon and recovered, or carbon monoxide gas generated by the reduction of the recovered carbon dioxide gas is converted into solid carbon and recovered by a carbon deposition reaction using the electricity obtained by using the biogas as fuel, A biogas-utilizing solid carbon recovery method in which electrolytic reduction or carbon deposition reaction is carried out using electricity obtained by using biogas as fuel, thereby supplying electricity to an apparatus for carrying out electrolytic reduction or carbon deposition reaction.

2. A biogas-utilizing solid carbon recovery method as described in claim 1, characterized in that electricity or heat is obtained from biogas by a fuel cell power generation method, gas engine power generation method, or gas turbine power generation method that generates renewable energy electricity using biomethane obtained after separating and recovering carbon dioxide from biogas as fuel, or a heat generation method that uses a biomethane-fired boiler that uses the biomethane as fuel.

3. A biogas-utilizing solid carbon recovery method as set forth in claim 2, characterized in that the power generation efficiency of a power generation system is improved by supplying air or oxygen-enriched air to a fuel cell, or pure oxygen gas to a gas engine or gas turbine as an oxidant to react with biomethane fuel, and the power and heat obtained from the use of biomethane are used to cool the exhaust gas emitted when using biomethane and remove moisture to separate and recover carbon dioxide gas, and the recovered carbon dioxide gas is converted into solid carbon and recovered by undergoing an electrolytic reduction or carbon deposition reaction using the power and heat obtained from the use of biomethane.

4. A biogas-utilizing solid carbon recovery method as described in claim 2, characterized in that cold energy is obtained by a cold energy conversion method using an absorption refrigerator or adsorption refrigerator driven by the waste heat of exhaust gases generated when electricity is generated by the power generation method, or by a turbo refrigerator driven by supplying electricity obtained by the power generation method, and the obtained cold energy is used to separate and recover carbon dioxide gas contained in the biogas.

5. A biogas-utilizing solid carbon recovery method as described in claim 2, characterized in that warm heat is obtained by heat exchange with high-temperature exhaust gas generated after power generation by the power generation method, and the obtained warm heat is used to separate and recover carbon dioxide gas contained in the biogas.

6. A biogas-utilizing solid carbon recovery method as described in claim 1, characterized in that the method for separating and recovering carbon dioxide gas from biogas is either a chemical absorption method, a physical adsorption method, or a separation membrane method.

7. A biogas-utilizing solid carbon recovery method as described in claim 2, characterized in that an electrode is provided inside a container containing high-temperature molten salt heated and maintained using renewable energy electricity obtained by the power generation method, and the carbon dioxide gas separated and recovered is supplied into the high-temperature molten salt while renewable energy electricity is supplied to the electrode, thereby electrolytically reducing the carbon dioxide gas to solid carbon and carbon monoxide gas and recovering it.

8. A biogas-utilizing solid carbon recovery method as described in claim 2, characterized in that it utilizes renewable energy electricity obtained by the power generation method and either water purified by condensing and recovering water vapor contained in exhaust gas generated during power generation or water purified from condensed water obtained in the biogas cooling and dehumidification process, or both, and supplies the separated and recovered carbon dioxide gas to an electrolytic cell, thereby electrolytically reducing the carbon dioxide gas to carbon monoxide gas and recovering it.

9. A biogas-utilizing solid carbon recovery method as described in claim 7 or claim 8, characterized in that carbon monoxide gas is supplied to a gas reactor that is heated by renewable energy electricity obtained by the power generation method and is equipped with a carbon deposition plate containing a catalyst that promotes carbon deposition, thereby precipitating solid carbon, and thereby converting the separated and recovered carbon dioxide gas into solid carbon and recovering it.

10. A biogas-utilizing solid carbon recovery method as described in claim 9, characterized in that the carbon deposition plate is equipped with an ultrasonic vibrator driven by renewable energy electricity obtained by the power generation method, and carbon is deposited while vibrating the carbon deposition plate at high frequency, thereby continuously depositing and recovering carbon while peeling off and removing the carbon deposited on the carbon deposition plate.

11. A biogas-utilizing solid carbon recovery method as described in claim 9, characterized in that the solid carbon precipitated in the gas reactor is continuously discharged by a solid carbon discharge mechanism driven by renewable energy electricity obtained by the power generation method, preventing blockage due to carbon precipitation in the gas reactor and continuously recovering solid carbon while maintaining a stable reaction.

12. 2. The biogas-utilizing solid carbon recovery method according to claim 1, characterized in that the rotational driving force obtained from the combustion energy of the biogas is directly used to rotationally drive one or more of a gas compressor, a gas blower, a vacuum pump, and a suction blower, thereby performing one or more of compression, suction, and air supply of the biogas to be supplied to a carbon dioxide gas separation and recovery device or the separated and recovered carbon dioxide gas.

13. A biogas-utilizing solid carbon recovery method as described in claim 4, characterized in that gas before carbon dioxide gas is separated and recovered is cooled by the cold heat, and carbon dioxide gas is separated and recovered from the cooled gas.

14. A biogas-utilizing solid carbon recovery method as described in claim 13, characterized in that the gas before carbon dioxide gas is separated and recovered is cooled by the cold heat to condense the moisture contained in the gas and thereby dehumidify it.

15. A biogas-utilizing solid carbon recovery system, characterized in that the method according to any one of claims 1 to 14 is applied.

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