METHOD FOR OPERATING METHANE FERMENTATION TREATMENT APPARATUS AND METHANE FERMENTATION TREATMENT APPARATUS

Abstract

To provide a technology capable of preventing blockage of the sludge supply path in a methane fermentation treatment apparatus.SOLUTION: A method of operating a methane fermentation treatment apparatus 101 for methane fermentation treatment of organic waste includes a withdrawal process for withdrawing methane fermentation liquid in a methane fermentation tank 1, a heating process for heating at least a part of the withdrawn methane fermentation liquid, a return process for returning at least a part of the heated methane fermentation liquid to the methane fermentation tank 1, and a merging process for merging the organic with at least a part of the heated methane fermentation liquid, and at least a part of the mixture of the organic waste and the heated methane fermentation liquid obtained in the merging process is returned to the methane fermentation tank 1 by the return process.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for operating a methane fermentation treatment apparatus and a methane fermentation treatment apparatus. [Background technology]

[0002] Methane fermentation (anaerobic fermentation) is widely used to dispose of organic waste, such as sludge generated in wastewater treatment and biomass, in order to reduce its volume and convert it into energy. Organic waste, which is the raw material for methane fermentation, is generally supplied to a methane fermentation tank using a pump, but if the solid concentration is high, there is a risk that the supply pipes will become clogged or the pump capacity will be insufficient to transport the waste.

[0003] For example, Patent Document 1 discloses a method for suppressing clogging of an input sludge pipe by organic sludge for a long period of time by heating the input sludge pipe that supplies organic sludge to a methane fermentation tank. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-181362 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method of Patent Document 1 requires the use of equipment for heating the input sludge pipe, such as a multi-pipe input sludge pipe in which organic sludge is supplied to the inner pipe and hot water is supplied between the inner and outer pipes. This complicates the equipment configuration, potentially increasing equipment costs and construction time. Furthermore, the need to heat the input sludge pipe may increase fuel and electricity consumption. Another possible method is to inject water into the pipe when it becomes clogged, but this may reduce the solids concentration and shorten the hydraulic retention time in the downstream methane fermentation tank. Furthermore, if the solids concentration of organic waste is automatically measured and used for operational control, the injection of water may cause a sudden change in concentration, potentially adversely affecting operational control.

[0006] An object of the present invention is to provide a technique capable of preventing clogging of a sludge supply path in a methane fermentation treatment device. [Means for solving the problem]

[0007] The method of operating a methane fermentation treatment device disclosed in the present application is a method of operating a methane fermentation treatment device that subjects organic waste to methane fermentation, and includes an extraction step of extracting a methane fermentation liquid from a methane fermentation tank, a heating step of heating at least a portion of the extracted methane fermentation liquid, a return step of returning at least a portion of the heated methane fermentation liquid to the methane fermentation tank, and a confluence step of merging the organic waste with at least a portion of the heated methane fermentation liquid, wherein at least a portion of the mixture of the organic waste and the heated methane fermentation liquid obtained in the confluence step is returned to the methane fermentation tank in the return step.

[0008] According to the above configuration, the methane fermentation liquid extracted from the methane fermentation tank in the extraction step is heated by a heating device such as a heat exchanger in the heating step, and the heated methane fermentation liquid is returned to the methane fermentation tank in the return step. In this circulation path, the organic waste is merged with the heated methane fermentation liquid downstream of the heat exchanger, thereby preventing clogging inside the heat exchanger. Furthermore, by utilizing the discharge pressure of the pump in the circulation path, clogging of the piping can be prevented and mixing of the supplied organic waste and methane fermentation liquid can be promoted within the circulation path. Furthermore, since water injection to unclog the supply path is not required, a sudden change in the concentration of solids in the treated liquid does not occur, which prevents a decrease in the hydraulic retention time of the downstream methane fermentation tank and prevents adverse effects on operation control.

[0009] The method may further include a concentration measurement step of measuring the solids concentration of the organic waste, and if the solids concentration of the organic waste measured in the concentration measurement step is equal to or greater than a predetermined value, the organic waste may be supplied to the confluence step, and if the solids concentration of the organic waste measured in the concentration measurement step is less than the predetermined value, the organic waste may be supplied directly to the methane fermentation tank.

[0010] According to this configuration, the solids concentration of the organic waste is measured in the concentration measurement process, and the supply destination of the organic waste is switched based on the solids concentration.When the solids concentration is such that clogging is unlikely to occur, the organic waste is supplied without passing through the circulation path.This reduces the load on the pump in the circulation path while preventing clogging in the sludge supply path and the circulation path, and allows the organic waste to be supplied to the methane fermentation tank.

[0011] When the solids concentration of the organic waste measured in the concentration measurement step remains at or above a predetermined value for a period of time that is longer than a predetermined period of time, at least a portion of the methane fermentation liquid extracted from the methane fermentation tank may be supplied to the methane fermentation tank via a path through which the organic waste is directly supplied to the methane fermentation tank.

[0012] According to this configuration, at least a portion of the methane fermentation liquid periodically extracted from the methane fermentation tank is directly supplied to the methane fermentation tank via a pathway through which organic waste is directly supplied to the methane fermentation tank, thereby preventing solids from adhering within the pathway.

[0013] The methane fermentation treatment device disclosed in the present application is a methane fermentation treatment device that performs methane fermentation treatment on organic waste, and includes a methane fermentation tank that performs methane fermentation treatment on the organic waste, an extraction means that extracts methane fermentation liquid from the methane fermentation tank, a heating means that heats at least a portion of the methane fermentation liquid extracted by the extraction means, a downstream return path that includes a return path that returns at least a portion of the methane fermentation liquid heated by the heating means to the methane fermentation tank, a first supply path that supplies the organic waste to the downstream return path, and a supply unit that is configured to supply the organic waste in the first supply path into the downstream return path, and the supply unit is located downstream of the heating means.

[0014] According to the above configuration, the methane fermentation liquid extracted from the methane fermentation tank is heated by a heating device such as a heat exchanger, and the heated methane fermentation liquid is returned to the methane fermentation tank via a downstream return path. In this circulation path, the organic waste is merged with the heated methane fermentation liquid in a supply section located downstream of the heat exchanger, thereby preventing clogging inside the heat exchanger. Furthermore, by utilizing the discharge pressure of the pump in the circulation path, clogging of the piping can be prevented and mixing of the supplied organic waste and methane fermentation liquid can be promoted within the circulation path. Furthermore, since water injection to unclog the supply path is not required, a sudden change in the concentration of solids in the treated liquid does not occur, which prevents a decrease in the hydraulic retention time of the downstream methane fermentation tank and prevents adverse effects on operation control.

[0015] The system may also include a concentration measuring means provided in the first supply path for measuring the solid concentration of the organic waste, and a second supply path branching off from between the concentration measuring means and the supply section and connected to a methane fermentation tank.

[0016] According to the above configuration, the concentration measuring means measures the solids concentration of the organic waste, and the supply destination of the organic waste is switched based on the solids concentration. When the solids concentration is such that clogging is unlikely to occur, the organic waste is supplied without passing through the circulation path. This reduces the load on the pump in the circulation path while preventing clogging in the sludge supply path and the circulation path, and allows the organic waste to be supplied to the methane fermentation tank.

[0017] Furthermore, if the solids concentration of the organic waste measured by the concentration measuring means is equal to or greater than a predetermined value, the organic waste may be supplied to the supply section via the first supply path, and if the solids concentration of the organic waste measured by the concentration measuring means is less than a predetermined value, the organic waste may be supplied directly to the methane fermentation tank via the second supply path.

[0018] According to the above configuration, the concentration measuring means measures the solids concentration of the organic waste, and the supply destination of the organic waste is switched based on the solids concentration. When the solids concentration is such that clogging is unlikely to occur, the organic waste is supplied without passing through the circulation path. This reduces the load on the pump in the circulation path while preventing clogging in the sludge supply path and the circulation path, and allows the organic waste to be supplied to the methane fermentation tank.

[0019] Furthermore, when the solid matter concentration of the organic waste measured by the concentration measuring means remains at or above a predetermined value for a period of time that is longer than a predetermined period of time, at least a portion of the methane fermentation liquid extracted from the methane fermentation tank may be supplied to the methane fermentation tank via the second supply path.

[0020] According to the above configuration, at least a portion of the methane fermentation liquid periodically extracted from the methane fermentation tank is directly supplied to the methane fermentation tank via the second supply path, thereby preventing solids from adhering within the second supply path.

[0021] In addition, the first supply path and the second supply path may be provided with at least one valve for switching the supply path of the organic waste, and a valve control device may be provided that automatically controls the opening and closing of the at least one valve based on the solid concentration of the organic waste measured by the concentration measurement means.

[0022] According to the above configuration, the concentration measuring means measures the solids concentration of the organic waste, and based on the solids concentration, the valve control device switches the supply destination of the organic waste by opening and closing a valve installed in the supply path.When the solids concentration is such that clogging is unlikely to occur, the organic waste is supplied without passing through the circulation path.This reduces the load on the pump in the circulation path while preventing clogging in the sludge supply path and the circulation path, and allows the organic waste to be supplied to the methane fermentation tank. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide a technique that can prevent clogging of a sludge supply path in a methane fermentation treatment device. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a diagram showing a methane fermentation treatment apparatus according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a diagram showing a methane fermentation treatment apparatus according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0026] The organic waste to be treated in the treatment method of the present invention includes sewage sludge, human waste sludge, agricultural village wastewater sludge, septic tank sludge, food waste (food biomass) such as kitchen garbage, lignocellulosic waste such as used paper and waste paper, agricultural residues, and livestock manure. These organic wastes may be treated individually or in combination. The treatment of sewage sludge will be described below as an example of the treatment target.

[0027] Fig. 1 is a diagram showing a methane fermentation treatment apparatus 101 according to a first embodiment of the present invention. As shown in Fig. 1, the methane fermentation treatment apparatus is mainly composed of a digester 1 as a methane fermenter.

[0028] (digestion tank) The digester 1 is a tank for subjecting sewage sludge (organic waste) to anaerobic fermentation treatment. The solids concentration (TS: Total Solids) of the raw sludge supplied to the digester 1 is preferably, for example, 3.0 to 10.0%. The digester 1 is operated at 30 to 45°C for a retention time of approximately 15 to 30 days in mesophilic fermentation treatment, and at 50 to 60°C for a retention time of approximately 7 to 20 days in thermophilic fermentation treatment. When the sewage sludge is fermented in the digester 1, the solids concentration of the digested sludge (methane fermentation treatment liquid) becomes approximately half of the solids concentration of the supplied raw sludge due to the decomposition action of methane fermentation bacteria. The digester 1 may be a tank made of steel plates or a tank made of concrete.

[0029] An agitator 5 is attached to the digester 1 to agitate the sewage sludge introduced into the digester 1. FIG. 1 shows the agitator 5 agitating the sludge with multiple stages of blades 5a (impellers) that rotate horizontally. The agitator 5 is driven by, for example, an electric motor 5b. The agitator 5 is generally disposed in the center of the digester 1 in a plan view. As shown by arrow D, the flow of sludge in the digester 1 caused by the agitator 5 during normal operation causes a downward flow in the center of the digester 1 due to the rotation of the blades 5a. This downward flow spreads at the bottom of the digester 1, reverses, and becomes an upward flow. Note that the agitator 5 (blade 5a) may be rotated in the reverse direction. When the agitator 5 is rotated in the reverse direction, the flow of sludge in the digester 1 is opposite to that during normal operation. That is, an upward flow is generated in the center of the digester 1, and this upward flow spreads at the top of the digester 1, reverses, and becomes a downward flow. Instead of the impeller type agitator 5 of this embodiment, other types of agitators such as a screw type or draft tube agitator may be used.

[0030] Digestion gas is generated in the digester tank 1 by anaerobic fermentation of the sewage sludge. The digestion gas is a gas (biogas) consisting of 50-60% by volume of methane and approximately 40-50% by volume of carbon dioxide. The generated digestion gas is extracted from the digester tank 1 and used as fuel for heating the digester tank 1 or as fuel for power generation equipment (not shown). In other words, by subjecting the sewage sludge to anaerobic fermentation treatment, the energy contained in the sewage sludge can be recovered as digestion gas (gas energy).

[0031] (pulling device and pulling process) The extraction device 2 (extraction means) is a device for extracting digested sludge (methane fermentation liquid) from the digestion tank 1 and supplying it to the downstream heating device 3. The extraction process is a process in which the digested sludge (methane fermentation liquid) is extracted from the digestion tank 1 and supplied to the heating process. The extraction device 2 has an extraction pipe 2a with a suction port located on the side of the digestion tank 1, and a pump 15 disposed on the extraction pipe 2a.

[0032] (Heating device, heating process) The heating device 3 (heating means) is a device for heating the digested sludge (methane fermentation liquid) extracted from the digester 1 by the extraction device 2. The heating process is a process for heating the digested sludge (methane fermentation liquid) extracted from the digester 1 in the extraction process. The heating device 3 has a heat exchanger 3a as a heater. The heat exchanger 3a is an indirect heat exchanger that heats the digested sludge. Hot water is supplied to the heat exchanger 3a from a hot water source such as a boiler (not shown). The digested sludge (methane fermentation liquid) extracted from the digester 1 by driving the pump 15 is heated by indirect contact with the hot water in the heat exchanger 3a, and then returned from the upper part of the digester 1 to the digester 1 via a downstream return path 4 that connects the heat exchanger 3a with the upper and lower parts of the digester 1.

[0033] (Supply section and joining process) The supply section 8 is a section where the first supply path 11 and the downstream return path 4 are connected so that the sewage sludge supplied from the storage tank 20 via the first supply path 11 (sludge supply path 10) and the digested sludge heated by the heating device 3 are combined. The combining step is a step in which the sewage sludge supplied from the storage tank 20 via the first supply path 11 and the digested sludge heated in the heating step are combined. In the supply section 8 (combining step), the combined mixture of the sewage sludge and the heated digested sludge is supplied into the digestion tank 1 from the top of the digestion tank 1 via the downstream return path 4. The location of the supply unit 8 is not particularly limited as long as it can connect the first supply path 11 to the downstream return path 4. However, because clogging is likely to occur at the vertically long portion of the downstream return path 4, it is preferable to provide the supply unit 8 at the connection between the heating device 3 and the downstream return path 4 or near the connection (specifically, within 5.0 m downstream of the connection toward the circulation path). To prevent clogging of the first supply path 11 with sludge, the pump 16 is preferably provided in the first supply path 11 so that the discharge side of the pump 16 is directly connected to the supply unit 8 or so that the distance between the discharge side of the pump 16 and the supply unit 8 is within 5.0 m. With this configuration, clogging does not occur in the first supply path 11 even when the solid concentration of the sewage sludge is high, and a mixture of sewage sludge and heated digested sludge can be supplied all the way to the top of the digester tank 1.

[0034] (Return route and return process) The return path is composed of an upstream return path (extraction device 2) and a downstream return path 4. The upstream return path is a return path located upstream of the heating device 3, and is provided with an extraction pipe 2a that extracts the methane fermentation liquid from the methane fermentation tank 1. The downstream return path 4 is a return path located downstream of the heating device 3, and is provided with a supply pipe 4a. The downstream return path 4 is a path that supplies the mixture of sewage sludge and heated digested sludge that has been combined in the supply unit 8 to the digester 1 from the top of the digester 1. The return process is a process in which the mixture of sewage sludge and heated digested sludge that has been combined in the combining process is supplied to the digester 1 from the top of the digester 1. As described above, the downstream return path 4 is provided downstream of the supply unit 8, and the mixture of sewage sludge and heated digested sludge is supplied to the digester 1 via the downstream return path 4 by the discharge pressure of pump 15 and / or pump 16. In this embodiment, the mixture of sewage sludge and heated digested sludge is supplied to the digestion tank 1 from the top of the digestion tank 1, but this is not limited to supplying it from the top, and it may also be supplied from the bottom or middle of the digestion tank 1.

[0035] 2 is a diagram showing a methane fermentation treatment apparatus 102 according to a second embodiment of the present invention. The methane fermentation treatment apparatus 102 differs from the methane fermentation treatment apparatus 101 of the first embodiment in that the methane fermentation treatment apparatus 102 of the second embodiment further includes a second sludge supply path 10 (hereinafter referred to as second supply path 12) branching off from a first sludge supply path 10 (hereinafter referred to as first supply path 11), a connecting path 13 branching off from the methane fermentation liquid withdrawal pipe 2a and connecting to the second supply path 12, and a concentration meter 7 that measures the solids concentration of sewage sludge (organic waste). The same symbols are used to refer to devices that are common between the methane fermentation treatment apparatus 101 of the first embodiment and the methane fermentation treatment apparatus 102 of the second embodiment.

[0036] The methane fermentation treatment device 102 is equipped with a second supply path 12 that directly supplies sewage sludge (organic waste) to the digester 1. The second supply path 12 branches off from the first supply path 11, and its downstream end is directly connected to the digester 1. Here, direct supply means that the sewage sludge (organic waste) is supplied to the digester 1 via the second supply path 12 without being supplied to the supply unit 8. The methane fermentation treatment device 102 also has a connecting path 13 that branches off from the methane fermentation liquid withdrawal pipe 2a and connects to the second supply path 12. The first supply path 11, the second supply path 12, and the connecting path 13 are provided with valves (on-off valves) V1, V2, V3, and V4, respectively. These valves V1 to V4 may be switched by automatically controlling the valve switching to switch the supply destination of the sewage sludge (organic waste) or methane fermentation liquid, or may be switched by manually opening and closing the valves to switch the supply destination of the sewage sludge (organic waste) or methane fermentation liquid.

[0037] (Densitometer and density measurement process) The concentration meter 7 (concentration measuring means) is a device that measures the solids concentration of the sewage sludge (organic waste) discharged from the storage tank 20 by operation of the pump 16. The concentration measuring process is a process that measures the solids concentration of the sewage sludge (organic waste) discharged from the storage tank 20 by operation of the pump 16. The concentration meter 7 may be installed in the first supply path 11 between the pump 16 and the supply unit 8 as shown in FIG. 2, or may be installed inside the storage tank 20 (not shown). Furthermore, the solids concentration of the sewage sludge (organic waste) may be measured manually (such as by collecting and weighing the sludge and calculating the solids concentration from the difference in mass before and after drying) in addition to measurement by the concentration meter 7.

[0038] The concentration meter 7 may be an ultrasonic concentration meter, a microwave concentration meter, a near-infrared concentration meter, or the like. In this embodiment, an inline type concentration meter 7 is used as an example, and the entire amount of sludge passes through the concentration meter 7. The concentration meter 7 and the controller 6 are connected by a cable, and the detection signal from the concentration meter 7 is input to the controller 6 via the cable.

[0039] The controller 6 may function as a valve control unit based on the measurement value of the concentration meter 7, for example, as follows. When the solids concentration of the sewage sludge measured by the concentration meter 7 is equal to or higher than a predetermined value, the controller 6 opens valves V1 and V2 installed in the first supply path 11 to supply the sewage sludge to the supply unit 8. When the solids concentration of the sewage sludge measured by the concentration meter 7 is lower than the predetermined value, the controller 6 closes valve V2 and opens valve V3 installed in the second supply path 12 to supply the sewage sludge directly to the digester 1. By controlling the opening and closing of the valves installed in each supply path based on the solids concentration of the sewage sludge and switching the supply destination of the sewage sludge, the sewage sludge is supplied without passing through the circulation path when the solids concentration is low enough to prevent clogging. This reduces the load on the pumps in the circulation path and prevents clogging in the sludge supply path and circulation path, allowing the sewage sludge to be supplied to the digester 1.

[0040] The predetermined solids concentration of the sewage sludge supplied to the digester tank 1 may be set appropriately, taking into account the properties of the sewage sludge. A preferable range is, for example, 3.0 to 10.0%. Furthermore, the predetermined solids concentration may be set to 1.05 to 1.5 times, preferably 1.1 to 1.3 times, the design concentration of the material to be conveyed, which was determined when the specifications of the pump 16 were selected. For example, if the design concentration is 8.0%, the predetermined value may be set within the range of 8.4 to 12.0%, preferably 8.8 to 10.4%. Furthermore, multiple predetermined values ​​may be set. For example, a first and second predetermined value may be set. When the first predetermined value is greater than the second predetermined value, the sewage sludge is supplied to the supply unit 8 when the first predetermined value is equal to or greater than the first predetermined value, and when the second predetermined value is equal to or less than the second predetermined value, the sewage sludge is supplied directly to the digester tank 1 without being supplied to the supply unit 8.

[0041] The controller 6 may be configured to control the following: when it determines that the solids concentration measured by the concentration meter 7 continues to be equal to or higher than a predetermined value for a predetermined period of time, the controller 6 closes valves V1 and V2 and opens valve V3 and valve V4 installed in the connecting path 13 to supply at least a portion of the methane fermentation liquor withdrawn from the methane fermentation tank 1 to the methane fermentation tank 1 via the second supply path 12. By periodically supplying at least a portion of the methane fermentation liquor withdrawn from the methane fermentation tank 1 from the connecting path 13 to the digester 1 via the second supply path 12, it is possible to prevent solids from adhering to the second supply path 12. Here, the predetermined period of time can be set to, for example, 24 hours, 48 ​​hours, or one or two weeks. However, if the specified time is set too long, solids will adhere to the second supply path 12, so it is preferable to supply at least a portion of the methane fermentation liquid extracted from the methane fermentation tank 1 to the digester 1 (methane fermenter) via the connecting path 13 and the second supply path 12 about once a week.

[0042] In the above embodiment, the controller 6 includes a so-called computer, including a CPU (Central Processing Unit), an EEPROM (Electrically Erasable and Programmable Read Only Memory) that rewritably stores programs executed by the CPU and data used in these programs, and a RAM (Random Access Memory) that temporarily stores data when the programs are executed. The above-mentioned functional units of the controller 6 are constructed by the cooperation of these hardware and the programs in the EEPROM. In other words, the programs cause the computers included in the methane fermentation treatment device 102 to execute the processes included in the various programs, thereby controlling the operation of the methane fermentation treatment device 102. In this way, the processes and operations of the methane fermentation treatment device 102 can be replaced by programs or operating methods of the methane fermentation treatment device. The number of computers included in the controller 6 is not limited to one, and functions may be distributed across multiple computers. That is, multiple controllers may be used. The control performed by the controller 6 (e.g., changing operating conditions) may be performed manually by an operator without using the controller 6 or without providing the controller 6 at all. Furthermore, the solid concentration of the supplied sludge may be measured manually by an operator, etc. That is, the operator may control each valve based on the value of the measuring instrument.

[0043] (effect) The operating method of the methane fermentation treatment device of this embodiment includes an extraction process for extracting digested sludge (methane fermentation liquid) from the digester 1 (methane fermenter), a heating process for heating the extracted digested sludge (methane fermentation liquid), a return process for returning the heated digested sludge (methane fermentation liquid) to the digester 1 (methane fermenter), and a confluence process for merging sewage sludge (organic waste) with the heated digested sludge (methane fermentation liquid), and the mixture of sewage sludge (organic waste) and heated digested sludge (methane fermentation liquid) obtained in the confluence process is returned to the digester 1 (methane fermenter) in the return process.

[0044] The above-described operating method provides the following effects.

[0045] In a circulation path in which the digested sludge (methane fermentation liquid) extracted from the digester 1 (methane fermenter) in the extraction process is heated and the heated digested sludge (methane fermentation liquid) in the heating process is returned to the digester 1 (methane fermenter) in the return process, clogging inside the heat exchanger 3a can be prevented by merging the sewage sludge (organic waste) with the heated digested sludge (methane fermentation liquid) downstream of the heat exchanger 3a. Note that if the sewage sludge (organic waste) is merged with the digested sludge (methane fermentation liquid) upstream of the heat exchanger 3a and passed through the heat exchanger 3a, organic waste such as sewage sludge contains hair, which can cause pipe clogging, and there is a risk that the hair will become entangled inside the heat exchanger 3a, causing clogging, in a spiral-type or other heat exchanger where the raw material flow path is narrow. Furthermore, organic waste such as agricultural crop residues may contain fibrous materials such as stems and leaves, and in this case as well, if the organic waste and the methane fermentation liquid extracted from the methane fermentation tank are combined upstream of the heat exchanger 3a and passed through the heat exchanger 3a, there is a risk of blockages occurring inside the heat exchanger 3a.

[0046] In addition, in the circulation path where the digested sludge (methane fermentation liquid) extracted from the digester 1 (methane fermenter) in the extraction process is heated and the heated digested sludge (methane fermentation liquid) in the heating process is returned to the digester 1 (methane fermenter) in the return process, clogging of the supply pipe can be prevented by utilizing the discharge pressure of the pump in the circulation path, and mixing of the supplied sludge and methane fermentation liquid can be promoted within the circulation path. Furthermore, since there is no need to inject water to unblock the sludge supply path 10, there is no sudden change in the solids concentration in the treated liquid, which prevents a decrease in the hydraulic retention time in the downstream digester 1 (methane fermenter) and prevents adverse effects on operation control.

[0047] Preferably, the method further includes a concentration measurement step for measuring the solids concentration of the sewage sludge (organic waste), and if the solids concentration of the sewage sludge (organic waste) measured in the concentration measurement step is equal to or greater than a predetermined value, the sewage sludge (organic waste) is supplied to the confluence step, and if the solids concentration of the sewage sludge (organic waste) measured in the concentration measurement step is less than the predetermined value, the sewage sludge (organic waste) is supplied directly to the digester 1 (methane fermenter). In this way, by switching the supply destination depending on the solids concentration of the sewage sludge (organic waste), the sewage sludge (organic waste) is supplied without passing through the circulation path when the solids concentration is low enough to prevent clogging, thereby reducing the load on the pump 15 in the circulation path and preventing clogging in the sludge supply path and the circulation path, and the sewage sludge (organic waste) can be supplied to the digester 1 (methane fermenter).

[0048] When the solids concentration of the sewage sludge (organic waste) measured in the concentration measurement step remains at or above a predetermined value for a predetermined period of time or longer, it is preferable to supply at least a portion of the methane fermentation liquid extracted from the methane fermentation tank to the digester 1 (methane fermenter) via the second supply path 12. By periodically supplying the methane fermentation liquid to the digester 1 (methane fermenter) via the second supply path 12, it is possible to prevent solids from adhering to the second supply path 12.

[0049] The present invention is not limited to the above-described embodiment. The configurations of the above-described embodiment can be appropriately combined, and various modifications can be made to the above-described embodiment. For example, the above-described embodiment can be modified as follows.

[0050] In the description of the first embodiment, an example was shown in which the densitometer 7 and the concentration measurement process were not provided, but the densitometer 7 and the concentration measurement process may be provided.

[0051] In the description of the first embodiment, an example was shown in which no branch was provided between the extraction device 2 and the heat exchanger 3a (upstream side of the heat exchanger) or between the heat exchanger 3a and the methane fermentation tank 1 (downstream side of the heat exchanger), but a separate branch path may be provided to send the methane fermentation liquid to other equipment.

[0052] In the above embodiment, an example was shown in which a solid-liquid separator for separating organic waste into solids and liquids was not provided, but a solid-liquid separator may be provided upstream of the storage tank 20. Furthermore, in the second embodiment, an example was shown in which, when the solid concentration of the organic waste measured by the concentration meter 7 remains at or above a predetermined value for a predetermined period of time or longer, at least a portion of the methane fermentation liquid extracted from the methane fermentation tank 1 is supplied to the methane fermentation tank 1 via the second supply path 12. However, when the solid concentration of the organic waste measured by the concentration meter 7 remains at or above a predetermined value for a predetermined period of time or longer, the solid concentration of the organic waste may be adjusted by a solid-liquid separator provided upstream of the storage tank 20 so that the solid concentration is less than the predetermined value, and the organic waste after the concentration adjustment may be supplied directly to the methane fermentation tank 1 via the second supply path 12. [Industrial Applicability]

[0053] The method for operating a methane fermentation treatment device and the methane fermentation treatment device of the present invention can be used to decompose and treat various organic wastes, such as sewage sludge, human waste sludge, agricultural village wastewater sludge, septic tank sludge, food waste (food biomass) including raw garbage, construction waste, lignocellulosic wastes such as used paper and discarded paper, agricultural residues, and livestock manure, and to generate methane using the decomposed products as a raw material. [Explanation of symbols]

[0054] 1: Digestion tank (methane fermentation tank) 2: Extraction device (upstream return route) 3:Heating device (heating means) 4: Downstream return route 7: Densitometer (concentration measurement means) 8: Supply section 11: First supply route 12: Second supply route 101, 102: Methane fermentation treatment equipment V1~4: Valve

Claims

1. A method for operating a methane fermentation treatment apparatus that treats organic waste by methane fermentation, comprising: an extraction step of extracting the methane fermentation liquid from the methane fermentation tank; a heating step of heating at least a portion of the extracted methane fermentation liquid; a returning step of returning at least a portion of the heated methane fermentation liquid to the methane fermenter; a combining step of combining the organic waste with at least a portion of the heated methane fermentation liquid; Equipped with At least a portion of the mixture of the organic waste and the heated methane fermentation liquid obtained in the joining step is returned to the methane fermentation tank in the returning step; Further comprising a concentration measuring step of measuring a solid concentration of the organic waste, If the solid matter concentration of the organic waste measured in the concentration measuring step is equal to or greater than a predetermined value, the organic waste is supplied to the joining step; If the solid concentration of the organic waste measured in the concentration measuring step is less than a predetermined value, the organic waste is directly supplied to the methane fermentation tank. A method for operating a methane fermentation treatment device.

2. The method for operating a methane fermentation treatment apparatus according to claim 1, When the period during which the solid matter concentration of the organic waste measured in the concentration measurement step is equal to or higher than a predetermined value continues for a predetermined period or longer, at least a portion of the methane fermentation liquid extracted from the methane fermentation tank is supplied to the methane fermentation tank via a path through which the organic waste is directly supplied to the methane fermentation tank. A method for operating a methane fermentation treatment device.

3. A methane fermentation treatment apparatus for treating organic waste through methane fermentation, a methane fermentation tank for subjecting the organic waste to methane fermentation treatment; an extraction means for extracting a methane fermentation liquid from the methane fermentation tank; a heating means for heating at least a portion of the methane fermentation liquid extracted by the extraction means; a downstream return path including a return path for returning at least a portion of the methane fermentation liquid heated by the heating means to the methane fermentation tank; a first supply path that supplies the organic waste to the downstream return path; a supply unit configured to supply the organic waste in the first supply path into the downstream return path; Equipped with the supply unit is located downstream of the heating means, a concentration measuring means provided in the first supply path for measuring the solid concentration of the organic waste; a second supply path branching off from between the concentration measuring means and the supply unit and connected to the methane fermentation tank; Equipped with Methane fermentation treatment equipment.

4. The methane fermentation treatment device according to claim 3, When the solid matter concentration of the organic waste measured by the concentration measuring means is equal to or greater than a predetermined value, the organic waste is supplied to the supply unit via the first supply path, When the solid matter concentration of the organic waste measured by the concentration measuring means is less than a predetermined value, the organic waste is directly supplied to the methane fermentation tank via the second supply path. Methane fermentation treatment equipment.

5. The methane fermentation treatment device according to claim 4, When the solid matter concentration of the organic waste measured by the concentration measuring means remains at or above a predetermined value for a predetermined period of time or longer, at least a portion of the methane fermentation liquid extracted from the methane fermentation tank is supplied to the methane fermentation tank via the second supply path. Methane fermentation treatment equipment.

6. The methane fermentation treatment device according to any one of claims 3 to 5, the first supply path and the second supply path are provided with at least one valve for switching the supply path of the organic waste, and a valve control device is provided that automatically controls opening and closing of the at least one valve based on the solid matter concentration of the organic waste measured by the concentration measurement means; Methane fermentation treatment equipment.

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