Power generating system

Abstract

To provide a power generating system that both saves energy for an entire methane fermentation facility and efficiently captures carbon dioxide from a biogas combustion exhaust gas.SOLUTION: A power generation system 1 includes a methane fermentation apparatus 10 in which organic wastes are decomposed by anaerobic bacteria to generate biogas consisting mainly of methane and carbon dioxide, a power generator 20 with internal combustion engine fueled by biogas, a water electrolysis apparatus 30 that generates hydrogen and oxygen by electrolysis of water using electricity generated by the power generator 20, an exhaust gas discharge line 103 that discharges exhaust gas from the internal combustion engine to the outside, an exhaust gas circulation line 104 that branches off from the exhaust gas discharge line 103 and circulates a portion of the exhaust gas to the air intake of the internal combustion engine, and an exhaust gas cooler 40 which cools the exhaust gas circulated to an intake of an internal combustion engine, and the sludge dryer 60 which dries the fermentation sludge discharged from the methane fermentation apparatus 10 using the heat of the exhaust gas removed in the exhaust gas cooler 40.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power generation system that achieves both energy savings for the entire methane fermentation facility and efficient recovery of carbon dioxide from the combustion exhaust gas of biogas.

Background Art

[0002] Since the combustion exhaust gas of power generation facilities contains a large amount of CO 2 in order to suppress global warming, it is urgent to recover CO 2 from the combustion exhaust gas. Or, efforts have also been made to suppress the generation of CO 2 from the fuel stage by exclusively burning or co-burning fuels such as ammonia that do not contain carbon.

[0003] However, in the separation and recovery of CO 2 from combustion exhaust gas, the higher the CO 2 concentration in the exhaust gas, the more efficient the recovery becomes. However, in general exhaust gas, the CO 2 concentration is as low as several to a dozen vol%, making it difficult to increase the recovery efficiency.

[0004] In this regard, Patent Document 1 discloses a technique of operating a gas engine with biogas generated from a methane fermentation device and oxygen obtained from a co-electrolysis facility, co-electrolyzing CO 2 separated from the combustion exhaust gas and water vapor in a solid oxide type electrolysis device to generate synthesis gas, and producing liquid fuel from the synthesis gas (Figure 2). In addition, as heat recovery from the exhaust heat of an oxygen-blown gas engine, the heated cooling water of the gas engine is used for heating the methane fermentation device.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the exhaust heat of a gas engine is as high as about 300 to 400°C. Using this for heating a methane fermentation apparatus (about 40°C) is not efficient considering the quality of heat. That is, heating the methane fermentation apparatus as a method of utilizing the exhaust heat of a gas engine is over-specification, so there is room for improving the method of utilizing the exhaust heat. By this improvement, carbon dioxide can be recovered from the combustion exhaust gas of biogas with even lower energy.

[0007] The present invention has been made to solve such problems, and an object thereof is to provide a power generation system that achieves both energy saving of the entire methane fermentation facility and efficient recovery of carbon dioxide from the combustion exhaust gas of biogas.

Means for Solving the Problems

[0008] (1) The power generation system according to the present invention includes a methane fermentation apparatus that decomposes organic waste by anaerobic bacteria to generate biogas mainly composed of methane and carbon dioxide, a power generation device equipped with an internal combustion engine using the biogas as fuel, a water electrolysis device that electrolyzes water using the power generated in the power generation device to generate hydrogen and oxygen, an exhaust gas discharge line that discharges the exhaust gas of the internal combustion engine to the outside, an exhaust gas circulation line that branches from the exhaust gas discharge line and circulates a part of the exhaust gas to the intake port of the internal combustion engine, an exhaust gas cooler that cools the exhaust gas circulated to the intake port of the internal combustion engine, and a sludge drying device that uses the heat of the exhaust gas removed in the exhaust gas cooler to dry the fermentation sludge discharged from the methane fermentation apparatus.

[0009] (2) Further, in the above (1), it is characterized in that it is provided with a combustion power generation device that generates power using fuel containing the dried sludge generated in the sludge drying device and supplies the generated power to the water electrolysis device.

[0010] (3) Further, in the above (2), a dried sludge storage tank for temporarily storing the dried sludge generated in the sludge dryer, a dried sludge feeding device for feeding the dried sludge stored in the dried sludge storage device to the combustion power generation device, a power generation fuel storage tank for storing organic power generation fuel, a power generation fuel feeding device for feeding the power generation fuel stored in the power generation fuel storage tank to the combustion power generation device, and a control device for controlling the dried sludge feeding device, the power generation fuel feeding device, and the combustion power generation device. When the power derived from renewable energy supplied to the water electrolysis device is insufficient, the control device preferentially operates the dried sludge feeding device to supply the power generated in the combustion power generation device to the water electrolysis device to compensate for the insufficient amount. When the power derived from renewable energy supplied to the water electrolysis device is sufficient, the control device preferentially operates the power generation fuel feeding device.

[0011] (4) Further, in the above (1), the water electrolysis device is a solid oxide type water electrolysis device, and it is characterized in that it is provided with a dried sludge combustion device that generates steam using the dried sludge generated in the sludge drying device as fuel and supplies the generated steam to the water electrolysis device.

Effect of the Invention

[0012] The present invention can be used as a power generation system that achieves both energy saving of the entire methane fermentation facility and efficient recovery of carbon dioxide from the combustion exhaust gas of biogas.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0014] [Embodiment 1] First, with reference to FIG. 1, the configuration and functions of Embodiment 1 of the present invention will be described. The power generation system 1 according to Embodiment 1 of the present invention includes a methane fermentation device 10, a power generation device 20, a water electrolysis device 30, an exhaust gas cooler 40, a sludge dehydrator 50, and a sludge dryer 60.

[0015] The methane fermentation device 10 is a general vertical cylindrical wet methane fermentation device that decomposes organic substances in a medium temperature (30 to 40°C) environment and generates biogas containing methane and carbon dioxide in an anaerobic atmosphere. The main components of the biogas are generally methane (about 60%) and carbon dioxide (about 40%), and in addition to these, trace components such as hydrogen sulfide are included.

[0016] The methane fermentation device 10 and the power generation device 20 are connected by a biogas supply line 101 which is a pipe. Also, a desulfurization device 15 employing a biological desulfurization method is provided in the biogas supply line 101. The desulfurization device 15 removes hydrogen sulfide contained in the biogas by bringing the biogas into contact with a biofilm formed on the surface of the filler by the power of microorganisms.

[0017] The power generation device 20 uses a gas engine fueled by biogas as a driving device, operates in response to the generation of methane gas, and generates electric power. The water electrolysis device 30 is a PEM (abbreviation for Polymer Electrolyte Membrane) type electrolysis device with a solid polymer as the electrolyte, which decomposes water into hydrogen and oxygen using electricity with water as the raw material. The electricity supplied to the water electrolysis device 30 is provided by the electricity generated by the power generation device 20, and the shortage is compensated by electricity from renewable energy sources such as wind power generation and solar power generation supplied from the power grid.

[0018] The water electrolysis device 30 and the power generation device 20 are connected by an oxygen supply line 102 made of piping, and the oxygen generated in the water electrolysis device 30 is introduced into the power generation device 20 through the oxygen supply line 102. Also, the hydrogen generated in the water electrolysis device 30 is supplied to a user (not shown) through a hydrogen supply line 105 which is a pipe.

[0019] An exhaust gas discharge line 103 made of piping is connected to the power generation device 20, and the exhaust gas generated in the power generation device 20 is discharged to the outside through the exhaust gas discharge line 103.

[0020] An exhaust gas cooler 40, which is a multi-tube heat exchanger using air as an intermediate heat medium, is provided in the exhaust gas discharge line 103. The exhaust gas cooler 40 cools the exhaust gas by heat exchange between the air cooled in a sludge dryer 60 (to be described later) and the exhaust gas of the power generation device 20, and condenses moisture in the process. The condensed moisture is discharged to the outside from a water discharge line 110.

[0021] Downstream of the exhaust gas cooler 40 in the exhaust gas discharge line 103, an exhaust gas circulation line 104 is provided which branches off from the exhaust gas discharge line 103 to circulate the exhaust gas to the power generation device 20. The exhaust gas circulation line 104 circulates the exhaust gas cooled and with its temperature reduced in the exhaust gas cooler 40 to the intake port of the power generation device 20.

[0022] The methane fermentation apparatus 10 is connected to a fermentation sludge supply line 106 constituted by a screw conveyor, and surplus fermentation sludge of the methane fermentation apparatus 10 is supplied to the sludge dehydrator 50 by the rotational force of the screw conveyor.

[0023] The sludge dehydrator 50 is a screw press type dehydrator, and dehydrates by conveying the fermentation sludge with a rotating screw blade and pressing it against an outer cylinder screen, and discharging water from the outer cylinder screen.

[0024] The sludge dehydrator 50 is connected to a dehydrated sludge supply line 107 composed of a general flight conveyor, and supplies the dehydrated sludge accommodated between flights to the sludge dryer 60 by driving a chain on which flights (pusher plates) are installed at equal intervals.

[0025] The sludge dryer 60 is a stirring type indirect heating type sludge dryer, and efficiently heats and dries the dehydrated sludge by introducing high-temperature air reheated in the exhaust gas cooler 40 to a shaft and rotating blades for stirring the dehydrated sludge, and a jacket of the dryer.

[0026] Next, the operation of the power generation system 1 according to the present embodiment will be described. Organic waste crushed in a pretreatment facility (not shown) is introduced into the methane fermentation apparatus 10, and the moisture is adjusted so that the solid content ratio becomes about 10%. The inside of the methane fermentation apparatus 10 is maintained at about 40°C, and the organic matter is decomposed by bacteria, generating methane and carbon dioxide as biogas.

[0027] The biogas generated in the methane fermentation apparatus 10 is supplied to the power generation apparatus 20 through the biogas supply line 101, and hydrogen sulfide is removed by the desulfurization apparatus 15 on the way. The biogas from which hydrogen sulfide has been removed is supplied as fuel to the power generation apparatus 20.

[0028] The water electrolysis device 30 electrolyzes water using the power from the power generation device 20 and, for the shortfall, the power from the power grid. The hydrogen generated at the cathode of the water electrolysis facility 30 by electrolysis is supplied to a user (not shown) through the hydrogen supply line 105. The oxygen generated at the anode of the water electrolysis facility 30 by electrolysis is supplied to the intake port of the power generation device 20 through the oxygen supply line 102.

[0029] The power generation device 20 takes in the biogas supplied through the biogas supply line 101, the exhaust gas supplied through the exhaust gas circulation line 104, and the oxygen supplied through the oxygen supply line 102, and drives a gas engine to generate electricity.

[0030] The exhaust gas of the power generation device 20 flows through the exhaust gas discharge line 103 and is supplied to the exhaust gas cooler 40 to be cooled. The cooled exhaust gas further flows through the exhaust gas discharge line 103 and is discharged to the outside, but on the way, it is diverted to the exhaust gas circulation line 104 and supplied to the inlet of the power generation device 20.

[0031] In the combustion of only biogas and oxygen, where the temperature in the combustion chamber of the gas engine becomes too high, an excessive temperature rise is prevented by mixing the exhaust gas, which is an inert gas. Although the control method will not be described in detail, for example, it is conceivable to adjust the flow rate of the exhaust gas flowing through the exhaust gas circulation line 104 so that the temperature in the combustion chamber becomes constant.

[0032] In the methane fermentation device 10, residues of decomposed organic matter, dead bodies of fungi, etc. accumulate as fermentation sludge. The accumulated fermentation sludge is extracted from the methane fermentation device 10 by the screw conveyor of the fermentation sludge supply line 106 and supplied to the sludge dehydrator 50.

[0033] The fermentation sludge supplied to the sludge dehydrator 50 is dehydrated by a screw press until the moisture content becomes about 70%. The dehydrated sludge is conveyed by the flight conveyor of the dehydrated sludge supply line 107 and supplied to the sludge dryer 60.

[0034] In the sludge dryer 60, the dehydrated sludge is heated and dried using the air heated by the high-temperature exhaust gas in the exhaust gas cooler 40 as an intermediate heat medium. By drying, the moisture content of the dehydrated sludge is reduced to about 10%. Although a large amount of thermal energy is required for sludge drying, energy savings can be achieved by effectively utilizing the exhaust gas of the power generation device 20.

[0035] Due to the above actions, in the power generation system 1, by using the heat quantity of the exhaust gas of the power generation device 20 for sludge drying, it is possible to achieve both cooling of the exhaust gas and drying of the sludge, and minimize the external energy required for each.

[0036] Also, by circulating a part of the cooled exhaust gas to the inlet of the power generation device 20, the proportion of inert gas in the intake air of the power generation device 20 can be increased. Therefore, while preventing an excessive temperature rise in the combustion chamber, power generation using oxygen, which is a by-product of the water electrolysis device 30, can be performed.

[0037] Furthermore, the oxygen generated in the water electrolysis device 30 is introduced into the power generation device 20 as an oxidant for driving the gas engine. By using oxygen as the oxidant instead of air, the nitrogen component, which accounts for about 80% of the air, is reduced, and the exhaust gas components become carbon dioxide and water, generating exhaust gas with a high carbon dioxide concentration and easy carbon dioxide recovery. Also, for example, in a situation where no air is taken in at all and nitrogen is completely exhausted, nitrogen oxides (NOx) are not generated either.

[0038] Also, generally, the water electrolysis device 30 is used for producing hydrogen, and the by-product oxygen can be effectively utilized in the power generation device 20.

[0039] Also, by recirculating the exhaust gas without taking in air into the power generation device 20, the amount of exhaust gas discharged to the outside of the system can be minimized, so the amount of heat carried out can be minimized, and the thermal efficiency of the entire system can be maximized.

[0040] In addition, in the present embodiment, the methane fermentation apparatus 10 has been described as a wet medium-temperature methane fermentation apparatus. However, the methane fermentation apparatus of the present invention may be in the form of a wet high-temperature type, a dry medium-temperature type, or a dry high-temperature type.

[0041] Also, although the drive device of the power generation device 20 has been described as a gas engine, the power generation device of the present invention is not limited to one having a gas engine as the drive device. That is, the power generation device of the present invention may be any internal combustion engine, such as a gas turbine. In addition, the intake of air into the power generation device 20 is not completely excluded, and it may be taken in depending on the design or other circumstances.

[0042] Also, although the water electrolysis device 20 has been described as a PEM type water electrolysis device, the water electrolysis device of the present invention may also be an SOEC (abbreviation for Solid Oxide Electrolyzer Cell) type water electrolysis device or an alkaline water electrolysis device.

[0043] Also, although the exhaust gas cooler 40 has been described as a heat exchanger using air as an intermediate heat medium, other intermediate heat media such as steam, hot water, oil, etc. can also be adopted according to conditions, and it may also be a device that directly dries sludge with exhaust gas without using an intermediate heat medium.

[0044] Also, although it has been described that the water condensed in the exhaust gas cooler 40 is discharged to the outside, it may be made into clean water by neutralization treatment or the like and then circulated to the water electrolysis facility 30. By doing so, the amount of newly used water can be reduced.

[0045] Also, the exhaust gas cooler 40 has been described as cooling the exhaust gas flowing in the exhaust gas discharge line 103 and circulating the cooled exhaust gas to the power generation device 20 via the exhaust gas circulation line 104. In this case, the exhaust gas discharged to the outside will be cooled to the same temperature as the exhaust gas circulated to the power generation device 20. However, there may be cases where it is desired to make the temperature of the exhaust gas discharged to the outside higher than the temperature of the exhaust gas circulated and supplied to the power generation device 20. In such cases, the exhaust gas flowing through the exhaust gas circulation line 104 may be cooled by the exhaust gas cooler 40. In addition, when it is desired to cool the exhaust gas discharged to the outside to a certain extent, the cooled exhaust gas flowing through the exhaust gas circulation line 104 may be used to cool it to the target temperature.

[0046] Also, although the sludge dehydrator 50 has been described as a screw press type dehydrator, it may be of other types such as a multi-disc type, a filter press type, or a belt press type.

[0047] Also, although the sludge dryer 60 has been described as a stirring type indirect heating dryer, it may be a direct heating type, and its mechanism may also be of other types such as a conveyor type or a drum type.

[0048] Also, when the exhaust gas cannot be cooled to room temperature due to design constraints of the sludge dryer 60, the excess heat of the exhaust gas may be used to heat the methane fermentation device 10 or evaporate the waste liquid to cool the exhaust gas to room temperature.

[0049] Also, although the fermented sludge supply line 106 has been described as a screw conveyor, it may be in the form of pipeline pressure feeding by a sludge pump.

[0050] Also, although the dewatered sludge supply line 107 has been described as a flight conveyor, it may be in the form of conveyance by a screw conveyor or pipeline pressure feeding by a pump.

[0051] Also, in the above description, the power has been described as being derived from renewable energy, but the power in the present embodiment and Embodiments 2 and 4 is not necessarily limited to being derived from renewable energy.

[0052] [Embodiment 2] Next, with reference to FIG. 2, the configuration and functions of Embodiment 2 will be described. Components having the same configuration and functions as those in Embodiment 1 are given the same numbers, and the description thereof is omitted. The power generation system 200 according to Embodiment 2 further includes a combustion power generation device 80 and a dried sludge supply line 108 in addition to those shown in Embodiment 1.

[0053] The combustion power generation device 80 is a gasification power generation facility that roasts dry sludge to extract combustible gas, purifies the gas, and supplies it to a gas engine to generate electricity.

[0054] The dry sludge supply line 108 is a screw conveyor that transports the dry sludge generated in the sludge dryer 60 to the combustion power generation device 80.

[0055] Next, the operation of the power generation system 200 according to the present embodiment will be described. The description of the operation similar to that of the first embodiment will be omitted.

[0056] Dry sludge is supplied to the combustion power generation device 80 from the dry sludge supply line 108. The dry sludge input into the combustion power generation device 80 is gasified within the combustion power generation device 80, and the combustion heat of the gas causes a boiler (not shown) to generate steam, and a steam turbine (not shown) to generate electricity. The generated electricity is supplied to the water electrolysis device 30.

[0057] By the above operation, in the power generation system 200, in addition to the effects of the first embodiment, by generating electricity using dry sludge as fuel and supplying the electricity to the water electrolysis device 30, the amount of electricity purchased from the power grid can be reduced, and the operating cost of the power generation system 200 can be reduced.

[0058] Also, since the electricity generated by the combustion power generation device 80 is electricity derived from renewable energy, the proportion of electricity derived from renewable energy supplied to the water electrolysis device 30 can be maintained at a high level.

[0059] In the present embodiment, although the combustion power generation device 80 has been described as a gasification power generation facility, it may also be a power generation facility in the form of a steam boiler.

[0060] Also, the surplus exhaust heat of the combustion power generation device 80 may be used to heat the methane fermentation device 10, added to the heat source of the sludge dryer 60, or used for evaporation of the waste liquid discharged from the methane fermentation device 10 or the sludge dehydrator 50.

[0061] Also, although the dry sludge supply line 108 has been described as a screw conveyor, it may be a batch conveyance means such as a flight conveyor, a belt conveyor, or a crane.

[0062] [Embodiment 3] Next, with reference to FIG. 3, the configuration and functions of Embodiment 3 will be described. Those having the same configuration and functions as in Embodiment 2 are given the same numbers, and the description thereof is omitted. The power generation system 300 according to Embodiment 3 further includes a dry sludge storage tank 70, a power generation fuel storage tank 75, a control device 90, an EMS 95, a dry sludge input line 109, and a power generation fuel input line 111, in addition to those shown in Embodiment 2.

[0063] The dry sludge storage tank 70 is a pit having a general concrete structure and is housed in a building. The dry sludge storage tank 70 temporarily stores the dry sludge conveyed by the dry sludge supply line 108.

[0064] The power generation fuel storage tank 75 is a pit having a general concrete structure and is housed in a building. The power generation fuel storage tank 75 temporarily stores organic power generation fuels such as wood chips, waste, and coal conveyed from a conveyor (not shown).

[0065] The combustion power generation device 80 can use not only the dry sludge 70 but also organic power generation fuels as fuels, and can generate power even with a mixture thereof. A part or all of the power generated by the combustion power generation device 80 using the organic power generation fuel as a fuel does not originate from renewable energy.

[0066] The control device 90 is a general DCS (Distributed Control System), and controls the operating state of the combustion power generation device 80. The EMS 95 is an Energy Management System, and is a system that adjusts the energy supply and demand between the power grid and the power generation system 300.

[0067] The dry sludge input line 109 is a screw conveyor, and inputs the dry sludge stored in the dry sludge storage tank 70 into the combustion power generation device 80. The power generation fuel input line 111 is a screw conveyor, and inputs the power generation fuel stored in the power generation fuel storage tank 75 into the combustion power generation device 80.

[0068] Next, the operation of the power generation system 300 according to the present embodiment will be described. The description of the operations similar to those in Embodiments 1 and 2 will be omitted.

[0069] While the renewable energy power is sufficiently supplied from the power grid, the EMS 95 preferentially operates the power generation fuel input line 111 via the control device 90, generates power with the combustion power generation device 80 using the power generation fuel, and consumes the power within the premises or supplies it to other facilities.

[0070] At this time, the control device 90 reduces the operating rate of the dry sludge input line 109, so the storage amount of dry sludge in the dry sludge storage tank 70 increases.

[0071] On the other hand, when the renewable energy power is not sufficiently supplied from the power grid, such as at night, the EMS 95 preferentially operates the dry sludge input line 109 in order to maintain the supply amount of the renewable energy power to the water electrolysis device 30, and generates power using the dry sludge stored in the dry sludge storage tank 70.

[0072] At this time, the control device 90 reduces the operating rate of the power generation fuel input line 111, so the storage amount of the power generation fuel in the power generation fuel storage tank 75 increases. On the other hand, the dry sludge stored in the dry sludge storage tank 70 is consumed and decreases during the time period when the supply amount of the renewable energy power from the power grid is sufficient.

[0073] Due to the above actions, in the power generation system 300, the dry sludge storage tank 70 and the power generation fuel storage tank 75 store each fuel, and the amount of dry sludge used in the combustion power generation device 80 can be changed according to the supply amount of the renewable energy power from the power grid system. Therefore, the ratio of the power derived from renewable energy supplied to the water electrolysis device 30 can be stably maintained at a high level. That is, the power generation system 300 can stably produce hydrogen derived from renewable energy power.

[0074] [Embodiment 4] Next, with reference to FIG. 4, the configuration and functions of Embodiment 4 will be described. Those having the same configuration and functions as in Embodiment 1 are assigned the same numbers. The power generation system 400 according to Embodiment 4 is obtained by further providing the dry sludge combustion device 85, the water supply line 112, and the steam supply line 113 to the one shown in Embodiment 1.

[0075] The dry sludge combustion device 85 is a boiler that burns the dry sludge supplied from the dry sludge supply line 108 and generates steam with its heat. The water supply line 112 is a pipe that supplies water for generating steam in the dry sludge combustion device 85. The steam supply line 113 is a pipe insulated with heat insulation material that supplies the steam generated in the dry sludge combustion device 85 to the water electrolysis device 30.

[0076] The water electrolysis device 30 in the present embodiment is an SOEC and can efficiently electrolyze water in a high-temperature state.

[0077] Next, the operation of the power generation system 400 according to the present embodiment will be described. The description of the operation similar to that in Embodiment 1 will be omitted.

[0078] The dry sludge combustion device 85 generates steam derived from renewable energy by the heat generated from burning the dry sludge, and the generated steam is supplied to the water electrolysis device 30 through the steam supply line 113.

[0079] In the water electrolysis device 30, by utilizing the heat of high-temperature steam, the power consumption is reduced and steam is efficiently decomposed into hydrogen and oxygen. Since steam is consumed in the water electrolysis device 30, water corresponding to the consumption amount is replenished from the water supply line 112.

[0080] By the above actions, in the power generation system 400, the energy of the dried sludge can be converted into heat derived from renewable energy, and water can be efficiently electrolyzed in the SOEC with that thermal energy, so that the energy consumption of the entire system can be reduced.

[0081] Since the SOEC operates at a high temperature, the generated hydrogen and oxygen are also in a high-temperature state. These waste heats may be used to heat the methane fermentation device 10, evaporate the waste liquid, or added as a heat source for sludge drying.

Industrial Applicability

[0082] The present invention can be used as a power generation system that can easily reduce the emission of greenhouse gases due to the combustion of power generation fuel while achieving energy conservation.

Explanation of Signs

[0083] 1, 200, 300, 400 Power generation system 10 Methane fermentation device 15 Desulfurization device 20 Power generation device 30 Water electrolysis facility 40 Exhaust gas cooler 50 Sludge dehydrator 60 Sludge dryer 70 Dried sludge storage tank 75 Power generation fuel storage tank 80 Combustion power generation device 90 Control device 95 EMS 101 Biogas supply line 102 Oxygen supply line 103 Exhaust gas discharge line 104 Exhaust gas circulation line 105 Hydrogen supply line 106 Fermentation sludge supply line 107 Dewatered sludge supply line 108 Dried sludge supply line 109 Dried sludge input line 110 Water discharge line 111 Power generation fuel input line 112 Water supply line 113 Steam supply line

Claims

1. A methane fermentation apparatus that decomposes organic waste by anaerobic bacteria to generate biogas mainly composed of methane and carbon dioxide, A power generation device equipped with an internal combustion engine using the biogas as fuel, A water electrolysis device that electrolyzes water using the power generated by the power generation device to generate hydrogen and oxygen, An exhaust gas discharge line that discharges the exhaust gas of the internal combustion engine to the outside, An exhaust gas circulation line that branches from the exhaust gas discharge line and circulates a part of the exhaust gas to the intake port of the internal combustion engine, An exhaust gas cooler that cools the exhaust gas circulated to the intake port of the internal combustion engine, A sludge drying device that utilizes the heat of the exhaust gas removed by the exhaust gas cooler to dry the fermentation sludge discharged from the methane fermentation apparatus, characterized in that it comprises a power generation system.

2. A combustion power generation device that generates power using fuel containing the dried sludge generated in the sludge drying device and supplies the generated power to the water electrolysis device, characterized in that the power generation system according to claim 1 is provided.

3. A dried sludge storage tank that temporarily stores the dried sludge generated in the sludge dryer, A dried sludge feeding device that feeds the dried sludge stored in the dried sludge storage device to the combustion power generation device, A power generation fuel storage tank that stores organic power generation fuel, A power generation fuel feeding device that feeds the power generation fuel stored in the power generation fuel storage tank to the combustion power generation device, A control device that controls the dried sludge feeding device, the power generation fuel feeding device, and the combustion power generation device, When the power derived from renewable energy supplied to the water electrolysis device is insufficient, the control device preferentially operates the dried sludge feeding device to supply the power generated by the combustion power generation device to the water electrolysis device to make up for the insufficient portion, and when the power derived from renewable energy supplied to the water electrolysis device is sufficient, the control device preferentially operates the power generation fuel feeding device, characterized in that the power generation system according to claim 2 is provided.

4. The water electrolysis device is a solid oxide type water electrolysis device, A dried sludge combustion device that generates steam using the dried sludge generated in the sludge drying device as fuel and supplies the generated steam to the water electrolysis device, characterized in that the power generation system according to claim 1 is provided.

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