Methanation treatment method and methanation treatment facility

Abstract

To prevent blockage of a piping by removing components that causes blockage in the piping for supplying organic wastes into a methane fermentation tank, without causing complexity of equipment constitution and cost increase.SOLUTION: A methane fermentation processing method has, as organic wastes, first organic waste C1 and second organic waste C2, and involves a heating process to heat the second organic waste C2, a first supply process to supply the first organic waste C1 which has not undergone the heating process to the methane fermentation tank 31, a second supply process to supply the second organic waste C2 which has undergone the heating process to the methane fermentation tank 31, and a third supply process to supply the second organic waste C2 which has undergone the heating process into the first supply piping 42 that supplies the first organic waste C1 to the methane fermentation tank 31.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a methane fermentation treatment method for producing biogas by subjecting organic waste to methane fermentation treatment, and a methane fermentation treatment facility.

Background Art

[0002] For example, in the disposal of organic waste such as sludge and biomass generated in wastewater treatment, methane fermentation (anaerobic fermentation) is widely carried out for the purpose of volume reduction and energy conversion. Methane fermentation is a technology in which organic waste is stored under anaerobic conditions for a certain period of time, and the organic waste is decomposed by the action of anaerobic microorganisms to generate biogas such as methane gas and carbon dioxide, and is widely adopted in domestic waste treatment facilities and wastewater treatment facilities.

[0003] A methane fermentation facility for carrying out methane fermentation mainly includes a methane fermentation tank for storing organic waste and carrying out methane fermentation, a stirrer for stirring the methane fermentation liquid in the methane fermentation tank, and a heating device for heating the methane fermentation liquid.

[0004] For example, when subjecting primary sedimentation sludge in sewage sludge to methane fermentation treatment, components that cause blockage of the pipe such as calcium stearate may accumulate in the pipe for supplying the primary sedimentation sludge to the methane fermentation tank, and blockage of the pipe may occur. Therefore, conventionally, when blockage occurs in the pipe, it is known to clean the inside of the pipe (see, for example, Patent Documents 1 and 2).

[0005] In Patent Document 1, the inside of the pipe is cleaned by supplying a cleaning liquid such as a strong acid such as hydrochloric acid or a solvent obtained by mixing methanol and chloroform into the pipe. In Patent Document 2, a coagulation sedimentation device for separating the water to be treated into sludge and treated water is provided, and a fluid is extracted from the coagulation sedimentation device, and the extracted fluid is supplied as cleaning water to the pipe through which the sludge flows to clean the inside of the pipe.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In Patent Document 1, since a storage and supply facility such as a cleaning liquid storage section, a cleaning liquid supply line, a delivery pump, and a valve body is provided to supply the cleaning liquid into the pipe, a storage and supply facility must be provided, which leads to complication of the facility configuration and cost increase. Further, when the cleaning liquid is a strong acid, it is necessary to take measures so as not to have an adverse effect on the environment, and in this regard as well, there is a possibility of causing complication of the facility configuration and cost increase.

[0008] In Patent Document 2, the water to be treated is limited to one having good separability that decomposes into sludge and treated water, and there is a possibility that it cannot be applied when subjecting primary sedimentation sludge to methane fermentation treatment. Further, when the temperature of the fluid extracted from the coagulation sedimentation device is, for example, around room temperature, even if the fluid is simply supplied into the pipe, there is a possibility that components causing blockage cannot be removed.

[0009] In view of this situation, the main problem of the present invention is to remove components that cause blockage in the pipe for supplying organic waste to the methane fermentation tank without causing complication of the facility configuration and cost increase, and to prevent blockage of the pipe, and to provide a methane fermentation treatment method and methane fermentation treatment equipment.

Means for Solving the Problems

[0010] The first characteristic configuration of the present invention is in a methane fermentation treatment method for producing biogas by subjecting organic waste to methane fermentation treatment in a methane fermentation tank, wherein the organic waste has a first organic waste and a second organic waste, a heating step of heating the second organic waste, A first supply step of supplying the first organic waste that has not undergone the heating step to the methane fermentation tank; A second supply step of supplying the second organic waste that has undergone the heating step to the methane fermentation tank; A third supply step of supplying the second organic waste that has undergone the heating step into a first supply pipe for supplying the first organic waste to the methane fermentation tank.

[0011] According to this configuration, in the second supply step, since the second organic waste heated through the heating step is supplied to the methane fermentation tank, the second organic waste can be heated and solubilized, and then methane fermentation treatment can be performed in the methane fermentation tank, thereby improving the recovery efficiency of biogas.

[0012] In the third supply step, since the first supply pipe is supplied with the second organic waste originally used for supplying to the methane fermentation tank, for example, there is no need to newly provide storage supply equipment for storing a cleaning liquid and supplying it to the first supply pipe, and the first supply pipe can be cleaned without causing complication of the equipment configuration and cost increase.

[0013] Moreover, in the third supply step, since the second organic waste heated through the heating step is supplied into the first supply pipe, components that cause blockage can be melted by the heated second organic waste. Therefore, components that cause blockage can be appropriately removed, and blockage of the first supply pipe can be prevented.

[0014] A second characteristic configuration of the present invention is that in the third supply step, the second organic waste is supplied to the first supply pipe in a form of flowing the second organic waste in the flow direction of the first organic waste in the first supply pipe.

[0015] According to this configuration, since the second organic waste is circulated in the flow direction of the first organic waste in the first supply pipe, in the first supply pipe, the second organic waste may be circulated in the same manner as the first organic waste. Therefore, the facilities for circulating the first organic waste can be used as they are, and the simplification of the facility configuration and the reduction of costs can be achieved.

[0016] The third characteristic configuration of the present invention is that in the third supply step, the second organic waste is supplied to the first supply pipe in a form in which the second organic waste is circulated in a direction opposite to the flow direction of the first organic waste in the first supply pipe.

[0017] According to this configuration, since the second organic waste is circulated in a direction opposite to the flow direction of the first organic waste in the first supply pipe, for example, even if a component that causes blockage is generated at the upstream part of the first supply pipe, the second organic waste can be circulated to the location where the component is generated, and the component can be appropriately removed.

[0018] The fourth characteristic configuration of the present invention is that in the first supply step, the first organic waste, which is a solid phase component obtained by supplying the water to be treated to the primary sedimentation tank for solid-liquid separation, is supplied to the methane fermentation tank. In the third supply step, the second organic waste that has flowed through the first supply pipe is supplied to the primary sedimentation tank.

[0019] According to this configuration, since the primary sedimentation tank is provided to supply the first organic waste to the methane fermentation tank, the second organic waste that has flowed through the first supply pipe is supplied to the originally provided primary sedimentation tank. Thereby, it is not necessary to newly provide facilities for disposing of the second organic waste that has flowed through the first supply pipe, and the simplification of the facility configuration and the reduction of costs can be achieved, and the second organic waste supplied to the primary sedimentation tank can be used as a raw material for methane fermentation.

[0020] The fifth characteristic configuration of the present invention is that the third supply step is executed every time a set time elapses.

[0021] According to this configuration, since the third supply step is executed every time the set time elapses, the first supply pipe is repeatedly cleaned, preventing the accumulation of components that cause blockage, and appropriately preventing blockage of the first supply pipe.

[0022] The sixth characteristic configuration of the present invention is that a first supply device for supplying the first organic waste to the methane fermentation tank is provided. A third supply step execution timing determination step is performed to determine the execution timing of the third supply step based on the operating state of the first supply device, the flow rate of the first organic waste in the first supply pipe, or the pipe internal pressure in the first supply pipe.

[0023] In the process of supplying the first organic waste to the methane fermentation tank, if some clogging occurs, the operating state of the first supply device changes, the flow rate of the first organic waste decreases, or the pipe internal pressure in the first supply pipe increases, and the flow rate and pipe internal pressure also change.

[0024] Therefore, according to this configuration, in the third supply step execution timing determination step, the execution timing of the third supply step is determined based on the operating state of the first supply device, the flow rate of the first organic waste in the first supply pipe, or the pipe internal pressure of the first supply pipe. Thereby, since the third supply step can be executed at an appropriate timing, blockage of the first supply pipe can be appropriately prevented without executing the third supply step unnecessarily.

[0025] The seventh characteristic configuration of the present invention is in a methane fermentation treatment facility that produces biogas by subjecting organic waste to methane fermentation treatment in a methane fermentation tank. The organic waste includes a first organic waste and a second organic waste. A heating unit for heating the second organic waste. A first supply unit having at least a first supply pipe for supplying the first organic waste that has not passed through the heating unit to the methane fermentation tank, A second supply unit having at least a second supply pipe for supplying the second organic waste that has passed through the heating unit to the methane fermentation tank, A third supply unit having at least a third supply pipe for supplying the second organic waste that has passed through the heating unit from inside the second supply pipe into the first supply pipe. The present configuration lies in this point.

[0026] According to this configuration, in the second supply unit, since the second organic waste heated through the heating unit is supplied to the methane fermentation tank, the second organic waste can be heated and solubilized, and then methane fermentation treatment can be performed in the methane fermentation tank, thereby increasing the recovery efficiency of biogas.

[0027] In the third supply unit, since the first supply pipe is supplied with the second organic waste originally for supplying to the methane fermentation tank, for example, there is no need to newly provide a storage supply facility for storing a cleaning liquid and supplying it to the first supply pipe like a cleaning liquid, and the first supply pipe can be cleaned without causing complication of the equipment configuration and cost increase.

[0028] Moreover, in the third supply unit, since the second organic waste heated through the heating unit is supplied into the first supply pipe, components that cause blockage can be melted by the heated second organic waste. Therefore, components that cause blockage can be appropriately removed, and blockage of the first supply pipe can be prevented.

Brief Description of the Drawings

[0029]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0030] An embodiment of a wastewater treatment facility applying the methane fermentation treatment method and methane fermentation treatment equipment according to the present invention will be described with reference to the drawings.

[0031] 〔First Embodiment〕 This wastewater treatment facility 1 is a facility for treating organic wastewater such as sewage and wastewater containing organic substances. As shown in FIG. 1, it is provided with a sewage treatment system 2 and a sludge treatment system 3 (corresponding to methane fermentation treatment equipment) for subjecting organic waste to methane fermentation treatment (anaerobic digestion treatment).

[0032] The sewage treatment system 2 is provided with a primary sedimentation tank 21, a biological treatment tank 22, and a final sedimentation tank 23 in the flow direction of the raw water A1 of the organic wastewater. The raw water A1 first flows into the primary sedimentation tank 21, and suspended solids, solids, etc. that are likely to precipitate in the primary sedimentation tank 21 are removed by sedimentation. Next, in the biological treatment tank 22, organic substances and other dirt in the raw water A1 are decomposed and removed by the action of microorganisms. Finally, activated sludge is sedimented in the final sedimentation tank 23, and the clarified supernatant water is discharged as treated water A2.

[0033] The raw sludge removed by sedimentation in the primary sedimentation tank 21 is sent as primary sediment sludge B1 to a first concentration device 24 (for example, a mechanical concentration device such as a screw concentrator, a centrifugal concentrator, or a flotation concentrator, or a gravity concentration device such as a gravity thickening tank) and concentrated to a solid concentration of about 2 to 10%. A part of the activated sludge removed by sedimentation in the final sedimentation tank 23 is returned to the biological treatment tank 22 as returned sludge B2, and the remaining excess sludge B3 is sent to a second concentration device 25 (for example, a mechanical concentration device such as a screw concentrator, a centrifugal concentrator, or a flotation concentrator) and concentrated to a solid concentration of about 2 to 10%.

[0034] The sludge treatment system 3 receives the organic wastes C1 and C2 from the sewage treatment system 2, and performs methane fermentation on the organic wastes C1 and C2 to produce methane gas. The organic wastes include a first organic waste C1 and a second organic waste C2 that is more difficult to decompose than the first organic waste C1. The sludge treatment system 3 receives the primary sludge B1, which is a solid phase obtained by supplying the raw water A1 of the organic wastewater to the primary sedimentation tank 21 for solid-liquid separation, as the first organic waste C1, and receives the excess sludge B3, which is a part of the activated sludge obtained in the final sedimentation tank 23, as the second organic waste C2.

[0035] In this way, the organic wastes from the sewage treatment system 2 are supplied to the sludge treatment system 3 in a state of being divided into a first organic waste C1 and a second organic waste C2. The volume ratio of the first organic waste C1 to the second organic waste C2 is not particularly limited and may be set as appropriate. For example, C1:C2 = 1.5:1, and it is preferable that the first organic waste C1 is more than the second organic waste C2.

[0036] The sludge treatment system 3 includes a methane fermentation tank 31, a first supply unit 41 having a first supply pipe 42 for supplying the first organic waste C1 to the methane fermentation tank 31, and a second supply unit 51 having a second supply pipe 52 for supplying the second organic waste C2 to the methane fermentation tank 31.

[0037] The second organic waste C2 is more difficult to decompose than the first organic waste C1. The reason is that the excess sludge B3, which is the second organic waste C2, contains a large amount of microorganisms, and the microorganisms have strong cell walls, and the organic components inside the cells are surrounded by the cell walls.

[0038] Therefore, the first supply unit 41 supplies the first organic waste C1 that has not passed through the heating unit to the methane fermentation tank 31 through the first supply pipe 42, while the second supply unit 51 supplies the second organic waste C2 that has passed through the heating unit 57 to the methane fermentation tank 31 through the second supply pipe 52. As a result, in the second supply unit 51, the second organic waste C2 is preheated and warmed in the heating unit 57 during the supply to the methane fermentation tank 31, thereby destroying the cell wall and making the gasification in the methane fermentation tank 31 easier in a state where the internal organic components have flowed out.

[0039] The first supply pipe 42 in the first supply unit 41 is arranged in a state of connecting the first concentration device 24 and the methane fermentation tank 31. In the middle part of the first supply pipe 42, a first supply pump 43 (corresponding to the first supply device), which is a pump P for transporting the first organic waste C1 to the methane fermentation tank 31, is provided. The first supply pump 43 is arranged at the most upstream part in the flow direction of the first organic waste C1 in the first supply pipe 42.

[0040] The second supply pipe 52 in the second supply unit 51 is arranged in a state of connecting the second concentration device 25 and the methane fermentation tank 31. In the middle part of the second supply pipe 52, a second supply pump 53, a constant temperature tank 54, and a third supply pump 55 are provided in order from the upstream side in the flow direction of the second organic waste C2. A heating pipe 56 for supplying the second organic waste C2 from the third supply pump 55 of the second supply pipe 52 to the constant temperature tank 54 is provided, and a heating unit 57 is arranged in the middle part of the heating pipe 56.

[0041] The second supply pump 53 is a pump P for transporting the second organic waste C2 to the methane fermentation tank 31, and the third supply pump 55 is a pump P for supplying the second organic waste C2 to the heating unit 57. The heating unit 57 is composed of a heat exchange unit that exchanges heat between a heating medium supplied from a heat source (not shown) and the second organic waste C2 to heat the second organic waste C2. The heating unit 57 may be any device that can heat the second organic waste C2, and is not limited to the heat exchange unit.

[0042] The constant temperature bath 54 maintains and retains the temperature of the second organic waste C2 heated by the heating unit 57. Here, the target temperature when heating the second organic waste C2 in the heating unit 57 may be set to a value between, for example, 65°C and 75°C, or may be set within a range without setting to a single point temperature so that it is between, for example, 70°C and 75°C. Preferably, it is 70°C. Also, regarding the residence time in the constant temperature bath 54, it may be set to a value between 20 minutes and 40 minutes, or may be set within a range without setting to a single point time so that it is between, for example, 30 minutes and 40 minutes. Preferably, it is 30 minutes.

[0043] In the methane fermentation tank 31, the first organic waste C1 supplied through the first supply pipe 42 and the second organic waste C2 supplied through the second supply pipe 52 are received, and methane fermentation treatment (anaerobic digestion treatment) is performed by the action of anaerobic bacteria such as acid-producing bacteria and methane-producing bacteria. The methane fermentation tank 31 is equipped with a heating device for heating the methane fermentation liquid in the methane fermentation tank 31 and a stirrer for stirring the methane fermentation liquid in the methane fermentation tank 31, although not shown in the figure. Heat insulating materials or the like can be disposed on the outer wall portion of the methane fermentation tank 31 or the like to prevent the temperature of the methane fermentation liquid in the methane fermentation tank 31 from decreasing.

[0044] Regarding the predetermined range of the appropriate temperature in the methane fermentation treatment in the methane fermentation tank 31, when performing methane fermentation treatment at medium temperature, for example, a temperature range of 30°C to 45°C can be set as the predetermined range of the appropriate temperature, and when performing methane fermentation treatment at high temperature, for example, a temperature range of 50°C to 60°C can be set as the predetermined range of the appropriate temperature.

[0045] As a methane fermentation treatment method, for the first organic waste C1, a first supply step is performed in which the first organic waste C1 is supplied to the methane fermentation tank 31 by the first supply unit 41 without going through a heating step. On the other hand, for the second organic waste C2, a heating step is performed in which the second organic waste C2 is heated by the heating unit 57, and a second supply step is performed in which the second organic waste C2 that has gone through the heating step is supplied to the methane fermentation tank 31 by the second supply unit 51. By preheating and warming the second organic waste C2, the cell wall is broken and the internal organic components flow out, thereby solubilizing the second organic waste C2. Therefore, after solubilizing the second organic waste C2, which is more difficult to decompose than the first organic waste C1, methane fermentation treatment can be performed in the methane fermentation tank 31, and the recovery efficiency of biogas can be improved.

[0046] The primary sludge B1, which is the first organic waste C1, contains components that cause blockage of pipes such as calcium stearate. Therefore, in the first supply pipe 42 that supplies the first organic waste C1 to the methane fermentation tank 31, components such as calcium stearate may accumulate, resulting in pipe blockage.

[0047] Therefore, a cleaning configuration for cleaning the first supply pipe 42 is provided. Hereinafter, this cleaning configuration will be described.

[0048] As shown in FIG. 1, for the second organic waste C2 that has passed through the heating unit 57, not only is it supplied to the methane fermentation tank 31 by the second supply pipe 52, but the second organic waste C2 that has passed through the heating unit 57 is also supplied from the second supply pipe 52 into the first supply pipe 42. A third supply unit 61 having a first-direction third supply pipe 62 (corresponding to the third supply pipe) is provided.

[0049] The third supply pipe 62 for the first direction is arranged in a state of connecting a part between the third supply pump 55 and the methane fermentation tank 31 in the second supply pipe 52 and a part corresponding to the upstream end, such as the vicinity of the first supply pump 43 in the first supply pipe 42. An on-off valve 63 for interrupting the flow of the second organic waste C2 in the third supply pipe 62 for the first direction is arranged at an intermediate part of the third supply pipe 62 for the first direction.

[0050] As shown in Fig. 1(A), with the on-off valve 63 in the closed state, by performing each of the first supply step, the heating step, and the second supply step, as shown by the thick line in Fig. 1(A), the first organic waste C1 is supplied to the methane fermentation tank 31 through the first supply pipe 42, and the second organic waste C2 is supplied to the methane fermentation tank 31 through the second supply pipe 52, and methane fermentation treatment is performed in the methane fermentation tank 31.

[0051] As shown in Fig. 1(B), the heating step is continuously performed, with the on-off valve 63 in the open state, a third supply step is performed in which the second organic waste C2 heated through the heating step is supplied from inside the second supply pipe 52 into the first supply pipe 42 through the third supply pipe 62 for the first direction of the third supply section 61. In this third supply step, by supplying the second organic waste C2 to a part corresponding to the upstream end of the first supply pipe 42 through the third supply pipe 62 for the first direction, with the flow direction of the first organic waste C1 in the first supply pipe 42 being the first direction, the second organic waste C2 is supplied to the first supply pipe 42 in a form of flowing the second organic waste C2 in that first direction.

[0052] By performing this third supply step, even if components that cause blockage remain in the first supply pipe 42, as shown by the thick line in Fig. 1(B), the second organic waste C2 heated by the heating unit 57 can be supplied from the second supply pipe 52 into the first supply pipe 42, and the components that cause blockage can be melted and removed by the heated second organic waste C2. Since the connection location of the third supply pipe 62 for the first direction in the first supply pipe 42 corresponds to the upstream end portion, the second organic waste C2 supplied to the upstream end portion is passed through to the methane fermentation tank 31 in the same manner as the first organic waste C1. Therefore, it is possible to remove the components that cause blockage over substantially the entire length of the first supply pipe 42 and prevent blockage of the pipe from occurring.

[0053] In the sludge treatment system 3, usually, as shown in Fig. 1(A), each step of the first supply step, the heating step, and the second supply step is performed with the first on-off valve 63 in the closed state, and at a preferable timing for cleaning the first supply pipe 42, as shown in Fig. 1(B), the first on-off valve 63 is switched to the open state and the third supply step is performed.

[0054] For example, the third supply step is executed, for example, once a day or once every two days each time the set time elapses. At this time, regarding the set time, not only a fixed time can be set, but different times can be set according to various conditions. For example, since the flow rate of the first organic waste C1, which is the primary sedimentation sludge B1, varies according to the inflow rate of the raw water A1 of the organic wastewater flowing into the primary sedimentation tank 21 of the sewage treatment system 2, the set time can be changed and set according to the inflow rate of the raw water A1 of the organic wastewater. For example, the set time can be sequentially changed and set to 2 hours, 8 hours, 2 hours, 12 hours, etc. in such a form that the set time is shortened as the inflow rate of the raw water A1 of the organic wastewater increases.

[0055] Also, in winter or the like, as the outside air temperature drops, the temperature of the first organic waste C1 also drops, creating a situation where components that cause blockages are likely to accumulate. Therefore, in winter, the set time can be set shorter, and in summer or the like, the set time can be set longer, and the set time can be changed according to the season. Thus, since it is considered that blockages in the pipes are likely to occur due to the temperature drop of the first organic waste C1, for example, by arranging a heat insulating material or the like around the first supply pipe 42, the temperature drop of the first organic waste C1 can be suppressed.

[0056] Furthermore, instead of using time, a third process execution timing determination process can be performed to determine the execution timing of the third supply process based on various conditions. In the process of supplying the first organic waste C1 to the methane fermentation tank 31, if some clogging occurs, the discharge pressure of the first supply pump 43 decreases and its operating state changes, and at the same time, the flow rate of the first organic waste C1 decreases, or the internal pressure of the first supply pipe 42 increases, resulting in changes in the flow rate and the internal pressure of the pipe.

[0057] Therefore, in the third supply process execution timing determination process, the execution timing of the third supply process is determined based on the operating state of the first supply pump 43, the flow rate of the first organic waste C1 in the first supply pipe 42, or the internal pressure of the first supply pipe 42.

[0058] Regarding the operating state of the first supply pump 43, for example, various information from the first supply pump 43 can be acquired by a management device or a control device of the sludge treatment system 3 or the like, so that the operating state of the first supply pump 43 can be acquired. For example, when the management device or the control device detects a predetermined change state such as a decrease in the discharge pressure based on the acquired operating state of the first supply pump 43, it can be determined that this is the execution timing of the third supply process.

[0059] Here, the first supply pump 43 is omitted, and a solenoid valve (corresponding to the first supply device) is arranged upstream of the first supply pipe 42. By adjusting the opening degree of the solenoid valve using the conveying force of the pump attached to the primary sedimentation tank 21 or the like, the first organic waste C1 can also be supplied to the methane fermentation tank 31 through the first supply pipe 42. In this case, the opening degree state of the solenoid valve will change according to the clogging condition during the supply process of the first organic waste C1 to the methane fermentation tank 31. Therefore, in the third supply process execution timing determination step, instead of the operating state of the first supply pump 43, the opening degree state of the solenoid valve can be acquired to determine the execution timing for executing the third supply process.

[0060] Regarding the flow rate of the first organic waste C1 in the first supply pipe 42, for example, a flow meter or the like is installed in the first supply pipe 42, and the management device or the control device can acquire the flow rate of the first organic waste C1 by obtaining the detection information of the flow meter. For example, when the flow rate of the first organic waste C1 acquired by the management device or the control device drops below the set flow rate, it can be determined that this is the execution timing for executing the third supply process. For example, the set flow rate can be set to 0.8 times that during normal operation, where normal operation means a state where there is no excessive or insufficient inflow of the object to be treated and the supply device is operating at its rated capacity. At this time, the stop condition for the third supply process can be set such that the flow rate of the first organic waste C1 becomes equal to that during normal operation.

[0061] Regarding the internal pipe pressure of the first supply pipe 42, a pressure gauge or the like is installed in the first supply pipe 42, and the management device or the control device can acquire the internal pipe pressure of the first supply pipe 42 by obtaining the detection information of the pressure gauge. For example, when the internal pipe pressure of the first supply pipe 42 acquired by the management device or the control device rises above the set pressure, it can be determined that this is the execution timing for executing the third supply process. For example, the set pressure can be set to 1.3 times that during normal operation. At this time, the stop condition for the third supply process can be set such that the internal pipe pressure of the first supply pipe 42 becomes equal to that during normal operation.

[0062] In this way, by performing the third supply process execution timing determination process, when it is determined that it is the execution timing to execute the third supply process, the management device or the control device can switch the first on-off valve 63 to the open state and automatically perform the third supply process.

[0063] Regarding the third supply process, when the stop condition is satisfied, the third supply process is stopped, and as shown in Fig. 1(A), the first on-off valve 63 is switched to the closed state, and each of the first supply process, the heating process, and the second supply process can be performed.

[0064] Regarding the stop condition, for example, the stop condition can be set based on the elapsed time since the start of the third supply process. Also, the operating state of the first supply pump 43 is such that the state where the discharge pressure has decreased has been eliminated, the flow rate of the first organic waste C1 in the first supply pipe 42 has recovered to a flow rate greater than the set flow rate, the pipe internal pressure of the first supply pipe 42 has recovered to a pressure lower than the set pressure, etc. can also be set as the stop condition. In this way, for the stop condition, various conditions that can determine that the blockage of the first supply pipe 42 has been eliminated can be set.

[0065] In Fig. 1(B), the first on-off valve 63 is disposed only in the first-direction third supply pipe 62, and no on-off valve is disposed at a downstream portion of the connection portion of the first-direction third supply pipe 62 in the second supply pipe 52. Therefore, a part of the second organic waste C2 in the second supply pipe 52 is supplied to the first supply pipe 42 through the first-direction third supply pipe 62. Although the thick line is omitted in Fig. 1(B), the remaining part of the second organic waste C2 flows through the second supply pipe 52 as it is and is supplied to the methane fermentation tank 31.

[0066] In Fig. 1(B), an on-off valve is also disposed at a downstream portion of the connection portion of the first-direction third supply pipe 62 in the second supply pipe 52. In the third supply process, by closing the on-off valve, all of the second organic waste C2 in the second supply pipe 52 can be supplied to the first supply pipe 42 through the first-direction third supply pipe 62.

[0067] In performing the third supply step, the thick line in Fig. 1(B) shows a case where the operation of the first supply pump 43 is stopped to stop the first supply step and the third supply step is executed. Not limited to this, the third supply step can also be executed while continuing the operation of the first supply pump 43 and continuing the first supply step. In this case, in the first supply pipe 42, the first organic waste C1 and the second organic waste C2 are mixed, and the mixture is supplied to the methane fermentation tank 31.

[0068] 〔Second Embodiment〕 This second embodiment is another embodiment of the flow direction of the second organic waste C2 in the third supply step in the first embodiment. Regarding other configurations and the like, since they are the same as those in the first embodiment, the same reference numerals and the like are used, and the description thereof is omitted.

[0069] In the first embodiment, as shown by the thick line in Fig. 1(B), in the third supply step, the second organic waste C2 is supplied to a portion corresponding to the upstream end of the first supply pipe 42 by the third supply pipe 62 for the first direction, so that the flow direction of the first organic waste C1 in the first supply pipe 42 is the first direction, and the second organic waste C2 is caused to flow in the first direction, and the second organic waste C2 is supplied to the first supply pipe 42.

[0070] On the other hand, in the second embodiment, as shown by the thick line in Fig. 2(B), in the third supply step, the second organic waste C2 is supplied to a portion corresponding to the downstream end of the first supply pipe 42 by the third supply pipe 64 for the second direction (corresponding to the third supply pipe), so that the opposite direction of the flow direction of the first organic waste C1 in the first supply pipe 42 is the second direction, and the second organic waste C2 is caused to flow in the second direction, and the second organic waste C2 is supplied to the first supply pipe 42.

[0071] As shown in FIG. 2, the third supply pipe 64 for the second direction in the second embodiment replaces the third supply pipe 62 for the first direction in the first embodiment, and is disposed in a state of connecting a portion between the third supply pump 55 and the methane fermentation tank 31 in the second supply pipe 52 and a portion corresponding to the downstream end of the first supply pipe 42. A second on-off valve 65 for interrupting the flow of the second organic waste C2 in the third supply pipe 64 for the second direction is disposed at an intermediate portion of the third supply pipe 64 for the second direction.

[0072] As shown in FIG. 2(A), with the second on-off valve 65 in the closed state, by performing each of the first supply step, the heating step, and the second supply step, as shown by the thick line in FIG. 2(A), the first organic waste C1 is supplied to the methane fermentation tank 31 through the first supply pipe 42, and the second organic waste C2 is supplied to the methane fermentation tank 31 through the second supply pipe 52, and methane fermentation treatment is performed in the methane fermentation tank 31.

[0073] As shown in FIG. 2(B), the heating step is continuously performed, the second on-off valve 65 is opened, and a third supply step is performed in which the second organic waste C2 heated through the heating step in the third supply pipe 64 for the second direction of the third supply unit 61 is supplied from the inside of the second supply pipe 52 into the first supply pipe 42. In this third supply step, by supplying the second organic waste C2 to a portion corresponding to the downstream end of the first supply pipe 42 through the third supply pipe 64 for the second direction, with the direction opposite to the flow direction of the first organic waste C1 in the first supply pipe 42 as the second direction, the second organic waste C2 is supplied to the first supply pipe 42 in a form of flowing in the second direction.

[0074] Since the connection point of the third supply pipe 64 for the second direction in the first supply pipe 42 is a portion corresponding to the downstream end, the second organic waste C2 supplied to the downstream end is made to flow over substantially the entire length of the first supply pipe 42 in the second direction. Therefore, components causing blockage can be removed over substantially the entire length of the first supply pipe 42, and occurrence of pipe blockage can be prevented.

[0075] Thus, since the second organic waste C2 is circulated in the second direction in the first supply pipe 42, for example, as shown in Fig. 2(B), by disposing the discharge part 66 near the front of the first supply pump 43 in the second direction, the components causing the removed blockage can be discharged to the outside of the first supply pipe 42 together with the second organic waste C2.

[0076] Also, as shown in Fig. 2(B), a return pipe 67 branching from near the front of the first supply pump 43 in the second direction is disposed in the first supply pipe 42, and the return pipe 67 is connected to the first sedimentation tank 21 and the first concentration device 24 first. A third on-off valve 68 for interrupting the flow of the second organic waste C2 in the return pipe 67 is disposed at an intermediate part of the return pipe 67. Thereby, in the third supply step, with the third on-off valve 68 in the open state, the second organic waste C2 supplied to the first supply pipe 42 can be supplied to the first sedimentation tank 21 and the first concentration device 24.

[0077] Incidentally, by disposing on-off valves at the connection part with the first sedimentation tank 21 and the connection part with the first concentration device 24 in the return pipe 67, it is also possible to select whether to supply the second organic waste C2 supplied to the first supply pipe 42 to the first sedimentation tank 21 or to the first concentration device 24. Also, since the first concentration device 24 can be omitted, when the first concentration device 24 is omitted, with the third on-off valve 68 in the open state, the second organic waste C2 supplied to the first supply pipe 42 can be supplied to the first sedimentation tank 21.

[0078] Also in the second embodiment, as in the first embodiment, usually, as shown in Fig. 2(A), with the second on-off valve 65 in the closed state, each step of the first supply step, the heating step, and the second supply step is performed, and at a preferable timing for cleaning the first supply pipe 42, as shown in Fig. 2(B), the second on-off valve 65 is switched to the open state to perform the third supply step. The timing for performing the third supply step is the same as that in the first embodiment, so the description thereof is omitted.

[0079] 〔Third Embodiment〕 In this third embodiment, similar to the second embodiment, it is another embodiment of the flow direction of the second organic waste C2 in the third supply step. However, the flow direction of the second organic waste C2 is not set to a fixed direction, but can be switched between a first direction and a second direction. Regarding other configurations and the like, since they are the same as those in the first embodiment, the same reference numerals and the like are used, and the description thereof is omitted.

[0080] In the third embodiment, as shown in FIG. 1, in addition to the third supply pipe 62 for the first direction, as shown by the dotted line in FIG. 1, a third supply pipe 64 for the second direction is provided. In the third supply step, by opening the first on-off valve 63 of the third supply pipe 62 for the first direction, the flow direction of the first organic waste C1 in the first supply pipe 42 is set to the first direction, and the second organic waste C2 can be made to flow in that first direction. Conversely, by opening the second on-off valve 65 of the third supply pipe 64 for the second direction, the opposite direction of the flow direction of the first organic waste C1 in the first supply pipe 42 is set to the second direction, and the second organic waste C2 can be made to flow in that second direction. Therefore, by switching between the state where the first on-off valve 63 is open and the state where the second on-off valve 65 is open, the flow direction of the second organic waste C2 in the first supply pipe 42 in the third supply step can be switched between the first direction and the second direction.

[0081] For example, in the third supply step performed at a certain timing, the first on-off valve 63 is opened to set the flow direction of the second organic waste C2 in the first supply pipe 42 to the first direction. In the third supply step performed at the next timing, the second on-off valve 65 is opened to set the flow direction of the second organic waste C2 in the first supply pipe 42 to the second direction. Each time the third supply step is performed, the flow direction of the second organic waste C2 in the first supply pipe 42 can be switched between the first direction and the second direction.

[0082] Also, at the beginning of the third supply process, the first on-off valve 63 is opened, and the flow direction of the second organic waste C2 in the first supply pipe 42 is set to the first direction. During the third supply process, the second on-off valve 65 can be opened to switch the flow direction of the second organic waste C2 in the first supply pipe 42 to the second direction. Conversely, at the beginning of the third supply process, the flow direction of the second organic waste C2 in the first supply pipe 42 can be set to the second direction, and during the third supply process, the flow direction of the second organic waste C2 in the first supply pipe 42 can be switched to the first direction. Thus, during the execution of the third supply process, the flow direction of the second organic waste C2 in the first supply pipe 42 can be switched between the first direction and the second direction.

[0083] 〔Another Embodiment〕 Another embodiment of the present invention will be described. Note that the configurations of the embodiments described below are not limited to being applied individually, and can also be applied in combination with the configurations of other embodiments.

[0084] (1) In the above embodiment, the first organic waste C1 is the primary sediment sludge B1, and the second organic waste C2, which is more difficult to decompose than the first organic waste C1, is the excess sludge B3. However, what the first organic waste and the second organic waste are can be appropriately changed. For example, the first organic waste can be food waste such as vegetable scraps, and the second organic waste can be oxidation ditch sludge, woody or plant-based biomass such as thinned wood and rice straw.

[0085] (2) In the above embodiment, the heating pipe 56 is connected to the second supply pipe 52, and the heating part 57 is disposed at an intermediate part of the heating pipe 56. However, for example, the heating pipe 56 can be omitted, and at an intermediate part of the second supply pipe 52, the heating part 57 and the constant temperature tank 54 can be disposed in this order from the upstream side in the flow direction of the second organic waste C2. Thus, the heating part 57 only needs to be able to heat the second organic waste C2 flowing through the second supply pipe 52, and the installation location thereof can be appropriately changed.

Explanation of Reference Numerals

[0086] 3 Sludge treatment system (methanation treatment facility) 21 Primary sedimentation tank 31 Methanation tank 41 First supply section 42 First supply pipe 53 First supply pump (first supply device) 51 Second supply section 52 Second supply pipe 57 Heating section 61 Third supply section 62 Third supply pipe for the first direction (third supply pipe) 64 Third supply pipe for the second direction (third supply pipe) C1 First organic waste C2 Second organic waste

Claims

1. In a methane fermentation treatment method for producing biogas by subjecting organic waste to methane fermentation in a methane fermentation tank, the organic waste includes a first organic waste and a second organic waste, a heating step of heating the second organic waste, a first supply step having a first supply pipe connected to the methane fermentation tank, and supplying the first organic waste that has not undergone the heating step to the methane fermentation tank through the first supply pipe, a second supply step having a second supply pipe connected to the methane fermentation tank, and supplying the second organic waste that has undergone the heating step to the methane fermentation tank through the second supply pipe, and a third supply step having a third supply pipe branched from the second supply pipe and connected to the first supply pipe, and supplying the second organic waste that has undergone the heating step from inside the second supply pipe into the first supply pipe through the third supply pipe. A methane fermentation treatment method.

2. The methane fermentation treatment method according to claim 1, wherein in the third supply step, the second organic waste is supplied to the first supply pipe in a form in which the second organic waste flows in the flow direction of the first organic waste in the first supply pipe.

3. A first supply pump for supplying the first organic waste to the methane fermentation tank is disposed at an intermediate portion of the first supply pipe, The methane fermentation treatment method according to claim 2, wherein the third supply pipe is connected to the first supply pipe in the vicinity of the first supply pump.

4. In a methane fermentation treatment method for producing biogas by subjecting organic waste to methane fermentation in a methane fermentation tank, the organic waste includes a first organic waste and a second organic waste, a heating step of heating the second organic waste, a first supply step of supplying the first organic waste that has not undergone the heating step to the methane fermentation tank, a second supply step of supplying the second organic waste that has undergone the heating step to the methane fermentation tank, and a third supply step of supplying the second organic waste that has undergone the heating step into the first supply pipe for supplying the first organic waste to the methane fermentation tank, The methane fermentation treatment method, wherein in the third supply step, the second organic waste is supplied to the first supply pipe in a form in which the second organic waste flows in a direction opposite to the flow direction of the first organic waste in the first supply pipe.

5. In the first supply step, the first organic waste, which is the solid phase obtained by supplying the water to be treated to a primary sedimentation tank for solid-liquid separation, is supplied to the methane fermentation tank. The methane fermentation treatment method according to claim 4, wherein in the third supply step, the second organic waste that has flowed through the first supply pipe is supplied to the primary sedimentation tank.

6. The methane fermentation treatment method according to claim 1, wherein the third supply step is executed every time a set time elapses.

7. A first supply device for supplying the first organic waste to the methane fermentation tank is provided. The methane fermentation treatment method according to claim 1, wherein a third supply step execution timing determination step is performed to determine the execution timing of the third supply step based on the operating state of the first supply device, the flow rate of the first organic waste in the first supply pipe, or the pipe internal pressure.

8. In a methane fermentation treatment facility for producing biogas by subjecting organic waste to methane fermentation in a methane fermentation tank, the organic waste includes a first organic waste and a second organic waste. A heating unit for heating the second organic waste. A first supply unit having a first supply pipe connected to the methane fermentation tank, and supplying the first organic waste that has not passed through the heating unit to the methane fermentation tank through the first supply pipe. A second supply unit having a second supply pipe connected to the methane fermentation tank, and supplying the second organic waste that has passed through the heating unit to the methane fermentation tank through the second supply pipe. A methane fermentation treatment facility provided with a third supply pipe branched from the second supply pipe and connected to the first supply pipe, and a third supply unit for supplying the second organic waste that has passed through the heating unit from the inside of the second supply pipe into the first supply pipe through the third supply pipe.

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