JP2022139541A - Methane fermentation device - Google Patents

Abstract

To provide a methane fermentation device which may use hot water obtained by burning biogas.SOLUTION: A methane fermentation device 10 has: a methane fermentation tank 11 in which organic substances contained in slurry 95, which is obtained by processing wastes, are fermented to generate biogas; and a heating device 13 which heats the methane fermentation tank 11 to facilitate fermentation of the organic substances. The methane fermentation device 10 further includes: a water heater 20 which burns the biogas taken out from the methane fermentation tank 11 to heat water and generate hot water; and a floor heating device 41 which heats an object part with the hot water generated by the water heater 20.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a methane fermentation apparatus that ferments organic matter contained in slurry obtained by treating waste to generate biogas.

An example of a methane fermentation apparatus that produces biogas by fermenting organic matter contained in slurry obtained by treating waste is described in Patent Document 1. The methane fermentation apparatus described in Patent Document 1 includes a garbage slurrying apparatus that pulverizes garbage while heating it with hot water or steam to obtain a heated garbage slurry at a predetermined temperature; Separation tank for sedimentation separation of inorganic solids by retaining heated kitchen waste slurry for a predetermined time, bioreactor for methane fermentation treatment of heated kitchen waste slurry after separation of inorganic solids, and methane gas an energy recovery device for generating electricity and hot water.

JP 2018-176119 A

The inventors of the present application have recognized the problem that the methane fermentation apparatus described in Patent Literature 1 does not consider the specific use of hot water and there is room for improvement.

An object of the present disclosure is to provide a methane fermentation apparatus that can use hot water obtained by burning biogas.

A methane fermentation apparatus of one embodiment comprises a treatment tank for fermenting organic matter contained in slurry obtained by treating waste to generate biogas, and heating the treatment tank to ferment the organic matter. and a heating device for promoting the methane fermentation apparatus, wherein the water heater generates hot water by heating water by burning the biogas taken out from the treatment tank, and the water heater generated by the water heater and a floor heating device for warming a target part with hot water.

According to the methane fermentation apparatus of one embodiment, hot water obtained by burning biogas can be used in a floor heating system.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the outline|summary of a methane fermentation apparatus. It is a block diagram showing a control system of a methane fermentation apparatus. 4 is a flow chart showing an example of control performed in a methane fermentation apparatus; 4 is a flow chart showing another example of control performed in the methane fermentation apparatus;

An embodiment of a methane fermentation apparatus will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an outline of the methane fermentation apparatus 10, and FIG. 2 is a block diagram showing a control system of the methane fermentation apparatus 10. As shown in FIG. The methane fermentation apparatus 10 includes a methane fermentation tank 11, a gas bag 12, a heating device 13, a circulation pump 14, a dehumidifier 15, a desulfurizer 16, a flow meter 17, a blower 18, a pressure gauge 19, a water heater 20, and digestive juice. It has a take-out route 21, a utilization facility 22, waste supply facilities 23A and 23B, and a control circuit 24.

There is a pretreatment step that sends the waste to the methane fermentor 11 . Waste includes food waste (such as food residue), kitchen waste, livestock manure, sewage sludge, and the like. In the pretreatment step, water is added to the waste crushed by the crusher 25 to produce a slurry suitable for methane fermentation. A slurry is a state of fluid in which solid particles are suspended in a liquid such as water. As an example, a slurry can be obtained with a turbidity of about 20 kg of food residue per day and about 20 kg of water per day.

The methane fermentation tank 11 is a bioreactor that performs anaerobic fermentation, that is, methane fermentation. A steel plate, concrete, synthetic resin, or the like can be used as the material of the methane fermentation tank 11 . The carrier is filled inside the methane fermentation tank 11 . The carrier, or fixed bed, is colonized with microorganisms, or methanogens.

The heating device 13 is provided outside the methane fermentation tank 11, specifically below it. The heating device 13 is for heating the slurry 50 in the methane fermentation tank 11 . The heating device 13 may be any one of a hot water heater, a sheathed heater, a ceramic heater, a carbon heater, a halogen heater, an oil heater, a panel heater, and the like. The hot water heater is provided with a thermally conductive pipe in the lower space of the methane fermentation tank 11 and supplies hot water into the pipe to heat the methane fermentation tank 11 . When the heating device 13 is a hot water heater, the heating device 13 has an electric pump 13A for transporting hot water to the piping. The electric pump 13A is powered and driven. If the heating device 13 is any one of a sheathed heater, a ceramic heater, a carbon heater, a halogen heater, an oil heater, a panel heater, etc., power is supplied to any one of them to heat the methane fermentation tank 11. is.

By heating the slurry 50 in the methane fermentation tank 11 with the heating device 13, it is possible to perform high temperature fermentation within the range of 50°C to 55°C, or medium temperature fermentation at around 37°C. Then, inside the methane fermentation tank 11 , the organic matter contained in the slurry 50 is efficiently decomposed, and biogas is generated inside the methane fermentation tank 11 . Biogas mainly contains methane (about 60%), carbon dioxide (about 40%), oxygen, hydrogen, hydrogen sulfide, nitrogen, ammonia, and the like.

The circulation pump 14 is provided in a circulation path 26 connected to the methane fermentation tank 11 . The circulation path 26 is a pipe that connects the lower part inside the methane fermentation tank 11 and the upper part inside the methane fermentation tank 11 . The circulation pump 14 is for stirring the slurry 50 inside the methane fermentation tank 11 . The circulation pump 14 has a suction port 27 , a discharge port 28 and a discharge port 29 , and is driven by an electric motor 30 .

When the circulation pump 14 is driven, the circulation pump 14 sucks the slurry 50 from the lower part of the methane fermentation tank 11 through the suction port 27 and discharges the sucked slurry 50 through the discharge port 28 for methane fermentation. It is sent to the upper part inside the tank 11 . Further, a valve 31 for opening and closing the discharge port 29 is provided. The valve 31 may be either manually operated by an operator or a solenoid valve operated by automatic electrical control.

A valve 32 is provided between the inside of the methane fermentation tank 11 and the suction port 27 of the circulation pump 14 in the circulation path 26 . The valve 32 is a mechanism that opens and closes the circulation path 26 . Valve 32 may be either manually operated by an operator or a solenoid valve actuated by automatic electrical control.

The gas bag 12 is provided so as to cover the methane fermentation tank 11 from above. The gas bag 12 is for containing the biogas generated inside the methane fermentation tank 11 . A gas extraction path 34 is connected to the gas discharge port 33 of the gas bag 12 . A valve 35 is provided between the dehumidifier 15 and the gas outlet 33 in the gas extraction path 34 . The valve 35 may be either a solenoid valve operated manually by an operator or a solenoid valve operated by automatic electrical control.

The dehumidifier 15 is a device that removes moisture contained in the biogas. The dehumidifier 15 includes a means for reducing the temperature of the biogas to condense and remove moisture, a means for passing the biogas through a desiccant to remove moisture, and a means for allowing the biogas to pass through a membrane separator to remove moisture. Any means of removal will do.

The desulfurizer 16 is provided downstream of the dehumidifier 15 in the gas extraction path 34 . Here, "downstream" means downstream in the flow direction of biogas. The desulfurizer 16 is a device that removes hydrogen sulfide contained in the biogas by desulfurizing the biogas. The desulfurizer 16 desulfurizes the hydrogen sulfide concentration to 10 ppm or less, for example. The desulfurizer 16 is, for example, a device that removes hydrogen sulfide by any one of a biological desulfurization method, a dry desulfurization method, and a membrane separation method. The biological desulfurization method removes hydrogen sulfide by the activity of sulfur sulfide bacteria derived from dairy cow manure. The dry desulfurization method removes hydrogen sulfide by adsorbing it on a catalyst such as iron oxide or activated carbon. In the membrane separation method, hydrogen sulfide is adsorbed on an adsorption membrane to remove hydrogen sulfide.

The flow meter 17 is provided downstream of the desulfurizer 16 in the gas extraction path 34 . The flow meter 17 detects the biogas flow rate per unit time. The flow meter 17 may be an ultrasonic flow meter, an electromagnetic flow meter, a Karman vortex flow meter, an impeller flow meter, a differential pressure flow meter, or the like. The flow meter 17 may have a function of outputting a signal corresponding to the detected biogas flow rate.

The blower 18 is provided downstream of the flow meter 17 in the gas extraction path 34 . The blower 18 is a compressor that transports the biogas discharged from the gas discharge port 33 of the gas bag 12 downstream, that is, to the water heater 20 . Blower 18 is driven by electric motor 36 . Blower 18 may be either a turbo compressor or a positive displacement compressor.

A pressure gauge 19 is provided downstream of the blower 18 in the gas extraction path 34 . A pressure gauge 19 measures the pressure of the biogas. The pressure gauge 19 may be of diaphragm type, bellows type, Bourdon tube type, piezoelectric element type, or the like. The pressure gauge 19 may have a function of outputting a signal corresponding to the detected biogas pressure.

The water heater 20 is provided downstream of the blower 18 in the biogas flow direction in the gas extraction path 34 . The water heater 20 is a device that burns transported biogas, transfers the heat to water (such as tap water), and discharges hot water. The hot water heated by the water heater 20 can be supplied to the utilization facility 22 . Moreover, when the heating device 13 is a hot water heater, it is possible to supply the heating device 13 with hot water discharged from the water heater 20 .

A valve 47 is provided between the pressure gauge 19 and the water heater 20 in the gas extraction path 34 . Valve 47 is a three-way valve that distributes biogas in gas extraction path 34 to diesel engine 39 and water heater 20 . The valve 47 may be either a solenoid valve operated manually by an operator or a solenoid valve operated by automatic electrical control.

The facilities 22 to be used include, for example, greenhouses, restaurants, detached houses, housing complexes, factories, and the like. As shown in FIG. 1 , the water heater 20 may be provided in the facility 22 for use, or may be provided at a location different from the facility 22 for use. The utilization facility 22 has a floor heating device 41 that uses hot water and an electrical equipment 42 that uses electric power. When the floor heating device 41 is installed under the floor of a restaurant, a detached house, a collective housing, a factory, or the like, it can heat the floor as a target part. When the floor heating device 41 is embedded in the ground of the greenhouse, it is possible to heat the ground as a target part with hot water. The ground includes soil and dirt.

A user of the floor heating device 41 arbitrarily sets the set temperature and the like. The floor heating device 41 has a communication function, and outputs a signal corresponding to the set temperature and a signal corresponding to operation and stop of the floor heating device 41 . The electrical equipment 42 includes lighting devices, refrigerators, washing machines, personal computers, television receivers, microwave ovens, and the like. A user of the electrical equipment 42 operates the electrical equipment 42 to operate, stop, use time, set temperature, turn on/off, and the like. The electric equipment 42 has a communication function, and the electric equipment 42 outputs a signal according to the user's operation.

The waste supply facility 23A supplies waste generated in the utilization facility 22, such as pruning waste generated during crop cultivation in the greenhouse, leaves removed during harvesting of crops in the greenhouse, garbage, leftover food, etc., to the pretreatment process. is to be sent to The waste supply facility 23A includes trucks, containers, conveyors, transport pipes, and the like. Disposers may be provided in restaurants, detached houses, collective housing, and the like. A disposer is a garbage grinder that is attached to a drain connected to the bottom of a cooking sink. The utilization facility 22 and the methane fermentation tank 11 may be connected by a conveyor, transport pipe, or the like included in the waste supply facility 23A. The waste supply facility 23B is for sending the waste generated in the facility 44 other than the utilization facility 22 to the pretreatment process. The facility 44 can treat garbage with a crusher 25 such as a food processor.

The digestive juice extraction path 21 is connected to the outlet 37 of the methane fermentation tank 11 . A digestive juice extraction path 21 and a circulation path 26 are connected in parallel to the methane fermentation tank 11 . The digestive liquid extraction route 21 is a route for taking out the liquid remaining inside the methane fermentation tank 11 after biogas is generated inside the methane fermentation tank 11, that is, the biogas digestive liquid.
A valve 48 is provided for opening and closing the digestive juice extraction path 21 . The valve 48 may be either manually operated by an operator or a solenoid valve operated by automatic electrical control. About 40 kg of biogas digestate is obtained per day, for example.

The methane fermentation device 10 may have a diesel engine 39 and a generator 38 . A diesel engine 39 has a combustion chamber and a fuel injection valve 49 . The fuel injection valve 49 controls the amount of fuel supplied to the combustion chamber. The fuel injection valve 49 is a solenoid valve whose opening/closing, degree of opening, and open time can be electrically controlled. Biogas is used as fuel to be supplied to the diesel engine 39 , and the torque of the output shaft of the diesel engine 39 rotates the generator 38 . Electric power generated by the generator 38 can be charged to the storage battery 40 via the electric circuit 45 . The storage battery 40 is a secondary battery that can be charged and discharged. As the amount of fuel supplied to the diesel engine 39 is relatively large, the amount of electric power (voltage) generated by the generator 38 is relatively high.

The electric power of the storage battery 40 can be supplied to the electric heater of the heating device 13, supplied to the electric motors 30 and 36, supplied to the electric equipment 42 of the utilization facility 22, and the like. The electric power generated by the generator 38 is supplied to the electric heater of the heating device 13, to the electric motors 30 and 36, and to the electric equipment 42 of the facility 22 without charging the storage battery 40. etc. is also possible.

The control circuit 24 is a computer having an input port, an output port, a central processing circuit, a memory circuit, and the like. The memory circuit stores data and information for controlling the heating device 13, the electric motors 30 and 36, the generator 38, the diesel engine 39, and the like. A signal output from the flow meter 17 , a signal output from the pressure gauge 19 , a signal output from the floor heating device 41 , and the like are input to the control circuit 24 . The control circuit 24 separately controls the temperature of the heating device 13 and the rotation, number of revolutions, and stoppage of the electric motors 30 and 36 based on the input signal, the data stored in the memory circuit, and the information. , the amount of power generated by the generator 38, the amount of biogas supplied to the diesel engine 39, operation, stop, rotation speed during operation, intake air amount, and the like.

If the valves 31, 32, 35, 47, 48 are solenoid valves, the control circuit 24 can control opening and closing of the valves 31, 32, 35, 47, 48 separately. By controlling the electric circuit 45, the control circuit 24 controls the supply destination, supply amount, etc. of the electric power generated by the generator 38. FIG. When the water heater 20 is provided in the facility 22, the operator of the facility 22 operates and stops the water heater 20, sets the temperature, and the like. When the water heater 20 is installed at a location other than the facility 22, the control circuit 24 operates and stops the water heater 20, sets the temperature, and the like.

Next, an operation example of the methane fermentation apparatus 10 will be described. The wastes supplied from the waste supply facilities 23A and 23B are processed into slurry in the pretreatment process and then introduced (supplied) into the methane fermentation tank 11 . The heating device 23 heats the methane fermentation tank 11, anaerobic fermentation, that is, methane fermentation is performed inside the methane fermentation tank 11, and biogas is generated. The biogas is discharged to the gas extraction path 34 through the gas bag 12 and the gas discharge port 33 .

The biogas transported through the gas extraction path 34 by the drive of the blower 18 is dehumidified by the dehumidifier 15 , hydrogen sulfide is removed by the desulfurizer 16 , and then sent to the water heater 20 . In the water heater 20, water is warmed by the heat of the combustion of the biogas, and hot water is discharged from the water heater 20. - 特許庁Therefore, the hot water discharged from the water heater 20 can be used in the floor heating device 41 of the utilization facility 22 . If the heating device 13 is a hot water heater, the hot water discharged from the water heater 20 can be supplied to the heating device 13 .

After biogas is generated inside the methane fermentation tank 11 , the biogas digestive liquid remaining inside the methane fermentation tank 11 is discharged from the digestive liquid extraction path 21 . Since the biogas digestive fluid contains fertilizer components such as nitrogen and potassium, the biogas digestive fluid can be used as a liquid fertilizer. For example, it is possible to spray the biogas digestive liquid into the greenhouse of the utilization facility 22 using a sprinkler or the like.

As described above, according to the methane fermentation apparatus 10 of the present embodiment, it is possible to heat the water with the biogas generated when the waste is heated to make hot water, and use the hot water in the floor heating device 41. .

Furthermore, an example of control performed in the methane fermentation apparatus 10 will be described with reference to the flowchart of FIG. The control example of FIG. 3 sets the target temperature of the heating device 13 based on the set temperature of the floor heating device 41 . The control circuit 24 detects the set temperature of the floor heating device 41 in step S10. If the water heater 20 is installed in a place other than the facility 22, the control circuit 24 sets the target temperature of hot water to be discharged from the water heater 20 based on the set temperature of the floor heating device 41 in step S11. . Specifically, the higher the set temperature of the floor heating device 41 is, the higher the target temperature of the hot water is set.

In step S12, the control circuit 24 determines the target flow rate of biogas transported from the methane fermentation tank 11 to the water heater 20 based on the target temperature of hot water. Specifically, the higher the target temperature of hot water is, the higher the target flow rate of biogas is set. The actual flow rate of biogas transported to water heater 20 varies depending on the amount of biogas produced in methane fermentation tank 11 . Therefore, in step S13, the control circuit 24 sets the target temperature of the heating device 13 based on the target flow rate of the biogas, and ends the control example of FIG. Specifically, the target temperature of the heating device 13 is set relatively high as the target flow rate of the biogas is relatively high. This is because the activation of methanogenic bacteria is accelerated as the temperature rises, and the amount of biogas produced increases.

In addition, the power consumption of the heating device 13 relatively increases as the target temperature is relatively higher. This applies not only when the heating device 13 is a mechanism other than a hot water heater, but also when the heating device 13 is a hot water heater. The reason for this is that the higher the target temperature of the heating device 13, the higher the target flow rate of hot water supplied from the water heater 20 to the hot water heater, and the more the amount of electric power required to drive the electric pump 13A. is.

When the control circuit 24 executes the control example of FIG. The target temperature of the heating device 13 is set based on the target flow rate of the biogas. Therefore, the power consumption of the heating device 13 can be controlled based on the set temperature of the floor heating device 41, and an increase in the power consumption of the heating device 13 can be suppressed.

Furthermore, another control example performed in the methane fermentation apparatus 10 will be described with reference to the flowchart of FIG. In step S20, the control circuit 24 sets the amount of electric power required for the methane fermentation apparatus 10 per predetermined period of time. The required amount of power can be calculated from the power consumption of the electric motors 30 and 36, the power consumption of the heating device 13, the power consumption of the electrical equipment 42, and the like. As the power consumption is relatively high, the amount of power required is relatively high. In step S21, the control circuit 24 sets a target power generation amount that exceeds the required power amount. The target power generation amount is a target value of power generated by the generator 38 per predetermined time. As the required amount of power relatively increases, the target power generation amount relatively increases.

In step S22, the control circuit 24 sets a target amount of biogas supply to the diesel engine 39 per predetermined time based on the target power generation amount. Data for setting a target supply amount (target injection amount) of biogas to the diesel engine 39 per predetermined time based on the target power generation amount is stored in advance in the storage circuit of the control circuit 24 . Specifically, the target amount of biogas to be supplied relatively increases as the target amount of electric power relatively increases.

In step S23, the control circuit 24 controls the fuel injection valve 49 of the diesel engine 39 based on the target biogas supply amount, and ends the control example of FIG. Data for controlling the fuel injection valve 49 of the diesel engine 39 based on the target biogas supply amount is stored in the memory circuit of the control circuit 24 in advance. Specifically, as the target supply amount of biogas is relatively large, the degree of opening of the fuel injection valve 49 is set relatively large, or the time during which the fuel injection valve 49 is opened is relatively large. , and the actual amount of biogas supplied to the diesel engine 39 per predetermined time is relatively large. In this way, when the control circuit 24 executes the control example of FIG. 4, the target amount of biogas supplied to the diesel engine 39 per predetermined time period is determined based on the amount of power required per predetermined time period for the methane fermentation apparatus 10. calculate. Therefore, wasteful consumption of biogas in the diesel engine 39 can be avoided.

An example of the technical meaning of the items described in the present embodiment is as follows. The methane fermentation apparatus 10 is an example of a methane fermentation apparatus, and the methane fermentation tank 11 is an example of a treatment tank. The heating device 13 is an example of a heating device. The heating device 13 can be defined as also serving as a floor heating device. Water heater 20 is an example of a water heater. The utilization facility 22 includes a greenhouse. The floor heating device 41 is an example of a floor heating device. The control circuit 24 is an example of a detection section, a first temperature setting section, a second temperature setting section, a target flow rate setting section, a required electric energy setting section, a target supply amount setting section, and a target electric energy setting section. Diesel engine 39 is an example of a gas engine. Generator 38 is an example of a generator. The circulation pump 14 and the electric motor 30 are an example of a stirring device. The target injection amount of biogas per predetermined time in the fuel injection valve 49 is an example of the target supply amount of biogas to the diesel engine.

The methane fermentation apparatus described in this embodiment is not limited to that described in the embodiment with reference to the drawings. For example, the gas engine may be a gas turbine instead of a diesel engine.

DESCRIPTION OF SYMBOLS 10... Methane fermentation apparatus, 11... Methane fermentation tank, 13... Heating apparatus, 13A... Electric pump, 14... Circulation pump, 20... Water heater, 22... Utilization facility, 24... Control circuit, 30, 36... Electric motor , 38... Generator, 39... Diesel engine, 41... Floor heating device, 49... Fuel injection valve

Claims (5)

a treatment tank for fermenting organic matter contained in slurry obtained by treating waste to generate biogas;
a heating device that promotes fermentation of the organic matter by heating the treatment tank;
In a methane fermentation apparatus having
a water heater that heats water and generates hot water by burning the biogas taken out from the treatment tank;
a floor heating device that warms a target part with hot water generated by the water heater;
A methane fermentation device. In the methane fermentation apparatus according to claim 1,
The floor heating device is buried in the ground of a greenhouse for cultivating crops,
The methane fermentation apparatus, wherein the target part is the ground of the greenhouse. In the methane fermentation apparatus according to claim 1,
The heating device also serves as the floor heating device,
A methane fermentation apparatus, wherein the target part includes the treatment tank. In the methane fermentation apparatus according to claim 1 or 2,
a detection unit that detects the set temperature of the floor heating device;
a first temperature setting unit that sets a target temperature of hot water of the water heater based on the set temperature of the floor heating device;
a target flow rate setting unit that sets a target flow rate of the biogas taken out from the treatment tank based on the target temperature;
a second temperature setting unit that sets a target temperature at which the heating device heats the processing tank based on the target flow rate of the biogas;
A methane fermentation device. In the methane fermentation apparatus according to any one of claims 1 to 4,
The heating device has a configuration in which electric power is supplied to heat the processing bath,
a gas engine that burns the biogas taken out from the treatment tank to generate rotational force;
a generator that converts the rotational force of the gas engine into electric power;
a required power amount setting unit for setting a required power amount including power to be supplied to the heating device;
a target power amount setting unit that sets a target power generation amount of the generator based on the required power amount;
a target supply amount setting unit that sets a target supply amount of the biogas to the gas engine based on the target power generation amount of the generator;
is further provided, a methane fermentation device.

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