Method and equipment for supplying raw material to methane fermentation tank

Abstract

To provide a technique capable of preventing clogging of a raw material supply path to a methane fermentation tank without using a lubricant or performing complicated pressure control.SOLUTION: Two or more organic wastes having different viscosities or solid concentrations are supplied to a methane fermentation tank 2 via a common supply path 1 in a predetermined order. The predetermined order is as follows: after supplying an organic waste having a viscosity higher than a predetermined value or an organic waste having a highest viscosity or solid concentration among two or more organic wastes having different viscosities or solid concentrations to the methane fermentation tank 2, then, an organic waste other than an organic waste having a viscosity equal to or lower than a predetermined value or the organic waste having the highest viscosity or solid concentration among two or more organic wastes having different viscosities or solid concentrations is supplied to the methane fermentation tank 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and equipment for supplying raw materials to a methane fermentation tank. [Background technology]

[0002] Methane fermentation (anaerobic fermentation) is widely used in the disposal of organic waste such as sludge and biomass generated in wastewater treatment, with the aim of reducing the volume and converting it into energy. Methane fermentation is a technology in which organic waste is decomposed by anaerobic microorganisms and biogas such as methane gas and carbon dioxide is generated by storing organic matter under anaerobic conditions for a certain period of time, and is widely adopted in domestic waste treatment facilities and wastewater treatment facilities. Methane fermentation facilities that perform methane fermentation mainly consist of a methane fermentation tank that stores organic waste and performs methane fermentation, an agitator that mixes and stirs the methane fermentation liquid in the methane fermentation tank, and a heating device that heats the methane fermentation liquid.

[0003] The raw materials for methane fermentation are sewage sludge such as primary sludge and excess sludge, wastewater treatment sludge discharged from water treatment facilities in factories, organic waste such as biomass, and are generally supplied to a methane fermentation tank through piping by a pump. However, if the solid concentration or viscosity of the raw materials is high, the pressure loss in the piping increases, which may make supply difficult. Patent Document 1 discloses a technique for injecting a lubricant between the outer periphery of the transported material and the inner periphery of the pipe. Patent Document 2 discloses a technique for controlling the rotation speed of a thickened sludge transfer pump so that the pressure inside the pipe is within a set range. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-97048 [Patent Document 2] Japanese Patent Application Publication No. 6-296995 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method of Patent Document 1 requires costs for installing the lubricant and the facility for injecting it. In addition, some components in the lubricant may adversely affect the methane fermentation process. The method of Patent Document 2 may require frequent changes in the pump speed to keep the pressure in the pipe within a set range, which may place a strain on the pump.

[0006] An object of the present invention is to provide a technique capable of preventing clogging of a raw material supply path to a methane fermentation tank without using a lubricant or performing complicated pressure control. [Means for solving the problem]

[0007] The method for supplying raw material to a methane fermentation tank disclosed in the present application supplies two or more organic wastes having different viscosities or solid concentrations to a methane fermentation tank in a predetermined order via a common supply path.

[0008] According to the above configuration, by supplying raw materials with different viscosities or solid concentrations to the methane fermentation tank in a predetermined order via the raw material supply path, the raw materials can be supplied to the methane fermentation tank without clogging the raw material supply path without using lubricants or performing complex pressure control. In addition, since multiple raw materials are supplied collectively via a single raw material supply path, the cost of the equipment can be reduced and the burden required for maintenance can be reduced. In addition, by alternately feeding raw materials with different viscosities, pressure loss can be reduced and the pump capacity can be made smaller. Furthermore, since the raw materials are mixed within the supply path and there is no need to install a mixing tank upstream of the methane fermentation tank, the equipment cost can be reduced.

[0009] It is preferable that the predetermined sequence is such that organic wastes having the same viscosity or the same solid matter concentration are not consecutively supplied.

[0010] According to this configuration, since the supply of organic waste of the same viscosity or the same solid concentration is not continuous, the raw material can be supplied to the methane fermentation tank without clogging the raw material supply path and without using lubricants or complex pressure control.

[0011] The predetermined order may be such that, after supplying to the methane fermentation tank an organic waste having a viscosity or solid concentration greater than a predetermined value or having the highest viscosity or solid concentration among two or more organic wastes having different viscosities or solid concentrations, an organic waste other than the organic waste having a viscosity or solid concentration equal to or less than the predetermined value, or having the highest viscosity or solid concentration among two or more organic wastes having different viscosities or solid concentrations, is supplied to the methane fermentation tank.

[0012] According to this configuration, by supplying raw materials with different viscosities or solid concentrations to the methane fermentation tank via the raw material supply path in a predetermined order, the raw materials can be supplied to the methane fermentation tank without clogging the raw material supply path and without using lubricants or complex pressure control.

[0013] The predetermined order is preferably such that, among two or more organic wastes having different viscosities or solid concentrations, the organic waste having the lowest viscosity or solid concentration is supplied first to the methane fermentation tank.

[0014] According to this configuration, when the methane fermentation tank starts operating or when it is restarted after a temporary interruption, the organic waste with the lowest viscosity or solid concentration among two or more organic wastes with different viscosities or solid concentrations is supplied to the methane fermentation tank first, thereby making it possible to supply raw materials to the methane fermentation tank without clogging the raw material supply path and without using lubricants or complex pressure control.

[0015] The equipment for supplying raw material to a methane fermentation tank disclosed in the present application includes a common supply path for supplying two or more organic wastes having different viscosities or solid concentrations to the methane fermentation tank in a predetermined order.

[0016] According to the above configuration, by supplying raw materials with different viscosities or solid concentrations to the methane fermentation tank in a predetermined order via the raw material supply path, the raw materials can be supplied to the methane fermentation tank without clogging the raw material supply path without using lubricants or performing complex pressure control. In addition, since multiple raw materials are supplied collectively via a single raw material supply path, the cost of the equipment can be reduced and the burden required for maintenance can be reduced. In addition, by alternately feeding raw materials with different viscosities or solid concentrations, pressure loss can be reduced and the pump capacity can be made smaller. Furthermore, since the raw materials are mixed within the supply path and there is no need to install a mixing tank upstream of the methane fermentation tank, the equipment cost can be reduced.

[0017] The supply path is preferably a pipe.

[0018] According to the above configuration, the raw material can be pumped through the piping, which reduces the cost and handling effort required to transport the raw material to the methane fermentation tank.

[0019] It is also preferable to provide a switching unit that switches the order in which two or more organic wastes having different viscosities or solid concentrations are supplied to the methane fermentation tank, and a flow rate measuring unit that measures the flow rate of the organic waste flowing through the supply path.

[0020] According to the above configuration, the flow rate measuring unit can monitor adhesion or clogging in the raw material supply path, and if adhesion or clogging occurs, the switching unit can switch the type of organic waste to be supplied to the raw material supply path. Therefore, the raw material can be supplied to the methane fermentation tank without clogging the raw material supply path without using a lubricant or performing complex pressure control. Effect of the Invention

[0021] According to the present invention, a technique can be provided that can supply raw material to a methane fermentation tank without clogging the raw material supply path and without using a lubricant or performing complex pressure control. [Brief description of the drawings]

[0022] [Figure 1] FIG. 2 is a diagram showing a raw material supplying facility to a methane fermenter according to the first embodiment. [Diagram 2] 4 is a flowchart showing a part of a control process in the equipment for supplying raw material to a methane fermenter according to the first embodiment. [Diagram 3] FIG. 11 is a diagram showing a raw material supplying facility to a methane fermenter according to a second embodiment. [Figure 4] 10 is a flowchart showing a part of a control process in the equipment for supplying raw material to a methane fermenter according to the second embodiment. [Diagram 5] FIG. 11 is a diagram showing a raw material supplying facility to a methane fermenter according to a third embodiment. [Figure 6] 10 is a flowchart showing a part of a control process in the equipment for supplying raw material to a methane fermenter according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0024] In the present invention, the organic wastes supplied to the methane fermentation tank include sewage sludge, human waste sludge, agricultural village wastewater sludge, septic tank sludge, food waste (food biomass) such as food waste, lignocellulosic waste such as used paper and waste paper, agricultural residues, and livestock manure. These organic wastes may be treated individually or in combination. In the following, the treatment of primary settling sludge and excess sludge of sewage sludge will be described as examples of organic wastes supplied to the methane fermentation tank.

[0025] First Embodiment A first embodiment of the present invention will be described below. The raw material supply equipment 101 to the methane fermentation tank of this embodiment is a system equipped with a common supply path for supplying two or more organic wastes having different viscosities or solid concentrations to the methane fermentation tank in a predetermined order. As shown in Fig. 1, the raw material supply equipment 101 to the methane fermentation tank 2 is mainly composed of a supply path 1 for supplying primary settling sludge and excess sludge to the methane fermentation tank 2, a primary settling sludge supply path 11 for supplying the primary settling sludge to the supply path 1, and an excess sludge supply path 12 for supplying the excess sludge to the supply path 1.

[0026] (Supply Channel) The supply path 1 is a path for supplying two or more organic wastes having different viscosities or solid concentrations to the methane fermentation tank 2 in a predetermined order. In this embodiment, the primary settling sludge and excess sludge correspond to two organic wastes having different viscosities or solid concentrations. The primary settling sludge corresponds to the organic waste having a viscosity or solid concentration equal to or less than a predetermined value among the two or more organic wastes having different viscosities or solid concentrations, and the excess sludge corresponds to the organic waste having a viscosity or solid concentration greater than a predetermined value among the two or more organic wastes having different viscosities or solid concentrations. Here, the viscosity or solid concentration of the organic waste may be due to temperature or specific gravity. The viscosity is measured by a viscometer for non-Newtonian fluids such as a rotational viscometer (not shown). The predetermined value of the viscosity of the organic waste may be any value between 0.150 and 0.180 Pa·s when the temperature of the organic waste is 20°C, or may be a value obtained by dividing the viscosity of the organic waste on the higher viscosity side by the viscosity of the organic waste on the lower viscosity side, and if the divided value is the predetermined value, it is any value between 1.5 and 10.5. The solid concentration is measured by a densitometer such as an ultrasonic densitometer, a microwave densitometer, or a near-infrared densitometer (not shown), but it is also possible to use a solid concentration calculated from the mass of the remaining solid matter after weighing a predetermined amount of organic waste and evaporating the water. The predetermined value of the solid concentration of the organic waste may be any value between 3.5 and 4.0%, or may be a value obtained by dividing the solid concentration of the organic waste on the higher solid concentration side by the solid concentration of the organic waste on the lower solid concentration side, and if the divided value is the predetermined value, it is any value between 1.1 and 5.0. Upstream of the supply path 1, there are provided a primary sludge supply path 11 for supplying primary sludge from the primary settling tank to the supply path 1, and an excess sludge supply path 12 for supplying excess sludge from the final settling tank to the supply path 1.

[0027] The primary sludge supply path 11 is provided with a valve V1, and the excess sludge supply path 12 is provided with a valve V2. By opening and closing each valve, the supply of raw sludge to the supply path 1 can be switched, and the primary sludge and excess sludge can be sent to the supply path 1 in a predetermined order. Here, the predetermined order means an order in which organic wastes of the same viscosity or the same solid concentration are not continuously supplied, but if the organic wastes have the same viscosity but different solid concentrations, these organic wastes may be continuously supplied. In addition, if the organic wastes have the same solid concentration but different viscosities, these organic wastes may be continuously supplied. The primary sludge and excess sludge may be alternately supplied to the supply path 1 by intermittent operation, or may be alternately supplied by continuous operation. In addition, these alternate supplies may be repeated multiple times, and the primary sludge and excess sludge may be merged on the way and supplied.

[0028] Valves V1 and V2 may switch the supply of raw sludge to supply path 1 by automatic valve switching controlled by controller 6, or may switch the supply of raw sludge to supply path 1 by manually opening and closing the valves.

[0029] The supply path 1 is preferably a pipe. By using the supply path 1 as a pipe, the raw sludge can be transported by a pump 10 disposed in the supply path 1, and the cost and the effort required for transporting the raw sludge to the methane fermentation tank 2 can be reduced.

[0030] The primary sludge is sludge extracted from the primary settling tank. The primary sludge contains a lot of water, and the solid concentration can be concentrated to about 3.8% by gravity concentration. The solid concentration is not particularly limited, but is 2.0 to 5.0%, preferably 3.0 to 4.0%, and more preferably 3.5 to 3.8%.

[0031] The excess sludge is sludge withdrawn from the final settling tank. The excess sludge contains a lot of water like the primary settling sludge, and can be concentrated to a solid concentration of 3.0 to 10.0%, preferably 3.5 to 8.0%, by mechanical thickening.

[0032] The primary sludge and excess sludge are supplied to a methane fermentation tank 2 via a common supply path 1. The solid concentration ratio of the primary sludge and excess sludge supplied is 1.1 to 5.0, preferably 1.1 to 2.5, more preferably 1.3 to 1.7, and most preferably 1.5.

[0033] (Methane fermentation tank) The methane fermentation tank 2 is a tank for subjecting sewage sludge (organic waste) to anaerobic fermentation treatment. The solid concentration (TS: Total Solids) of the raw material supplied to the methane fermentation tank 2 is preferably, for example, 3.0 to 10.0%. The methane fermentation tank 2 is operated at 30 to 45°C for a residence time of about 15 to 30 days in mesophilic fermentation treatment, and at 50 to 60°C for a residence time of about 7 to 20 days in high-temperature fermentation treatment. The methane fermentation tank 2 may be a tank made of steel plates or a tank made of concrete.

[0034] An agitator 5 is attached to the methane fermentation tank 2 to agitate the raw sludge introduced into the methane fermentation tank 2. FIG. 1 shows the agitator 5 that agitates the raw sludge with multiple stages of blades 5b (impellers) that rotate horizontally. The drive source of the agitator 5 is, for example, an electric motor 5a. The agitator 5 is generally disposed in the center of the methane fermentation tank 2 in a plan view. As shown by the arrow D, the flow of sludge in the methane fermentation tank 2 caused by the agitator 5 during normal operation, a downward flow is generated in the center of the methane fermentation tank 2 due to the rotation of the blades 5b during normal operation. This downward flow spreads at the bottom of the methane fermentation tank 2, reverses, and becomes an upward flow. The agitator 5 (blade 5b) may be rotated in the reverse direction. When the agitator 5 is rotated in the reverse direction, the flow of sludge in the methane fermentation tank 2 becomes the opposite flow to that during normal operation. That is, an upward flow is generated in the center of the methane fermentation tank 2, and this upward flow spreads and reverses at the upper part of the methane fermentation tank 2 to become a downward flow. Note that instead of the impeller type agitator 5 as in this embodiment, other types of agitators such as a screw type or a draft tube agitator may be used.

[0035] Digestion gas is generated in the methane fermentation tank 2 by anaerobic fermentation of the sewage sludge. The digestion gas is a gas (biogas) containing 50-60% by volume of methane and approximately 40-50% by volume of carbon dioxide. The generated digestion gas is extracted from the methane fermentation tank 2 and used as fuel for heating the methane fermentation tank 2 or as fuel for power generation equipment (not shown). In other words, by subjecting the raw sludge to anaerobic fermentation treatment, the energy contained in the raw sludge can be recovered as digestion gas (gas energy).

[0036] (controller) The controller 6 includes a CPU, a RAM, and a ROM. The CPU executes information processing based on programs and various data stored in the ROM and the RAM. In this way, the controller 6 realizes each function of a plurality of functional processing units. The controller 6 includes a timing unit 6a and a valve switching control unit 6b as functional processing units. The timing unit 6a measures the cumulative time that each raw sludge is supplied to the methane fermentation tank 2 via the supply path 1. The valve switching control unit 6b controls the opening and closing of the valves V1 and V2. The controller 6 of this embodiment controls the opening and closing of the valves V1 and V2 based on the cumulative time that the raw sludge is supplied to the methane fermentation tank 2 via the supply path 1.

[0037] Hereinafter, specific control of the valves V1 and V2 by the controller 6 will be described with reference to the flowchart of FIG.

[0038] When the control by the controller 6 is started, the controller 6 opens only the valve V1 of the primary sludge supply path 11 among the closed valves V1 and V2 (step 1). When the controller 6 determines that the supply time of the primary sludge having a viscosity equal to or less than the predetermined value V1 to the supply path 1 reaches the predetermined time T1 (step 2: Yes), the controller 6 closes the valve V1 of the primary sludge supply path 11 and opens the valve V2 of the excess sludge supply path 12 to supply the excess sludge having a viscosity greater than the predetermined value V1 to the supply path 1 (step 3). Next, when the controller 6 determines that the supply time of the excess sludge to the supply path 1 reaches the predetermined time T2 (step 4: Yes), the controller 6 opens the valve V1 of the primary sludge supply path 11 and closes the valve V2 of the excess sludge supply path 12 to supply the primary sludge to the supply path 1 (step 5). In the embodiment described, when one valve is operated, the other valve is immediately operated, but the operation of the other valve may be started after a certain time has elapsed since the operation of one valve. Also, in the embodiment described, the opening and closing of each valve is determined using the supply time as an index, but the volumetric flow rate or mass flow rate may be used as an index, and each valve may be operated, for example, when a certain volumetric flow rate of organic waste is supplied.

[0039] Here, the predetermined times T1 and T2 can be set based on the generation rates of the primary sludge and excess sludge, or the hydraulic retention time (HRT) and inner volume of the piping of the methane fermentation tank 2. The predetermined times T1 and T2 may be set to the same time or different times. The predetermined times T1 and T2 may be set to a value of, for example, 5 minutes or more and 2 hours or less, preferably 10 minutes or more and 30 minutes or less.

[0040] In this embodiment, the primary sludge and excess sludge are alternately sent to the supply path 1 on a regular basis, thereby making it possible to prevent solids from adhering to the inside of the supply path 1.

[0041] <Second embodiment> Next, a second embodiment of the present invention will be described. Fig. 3 is a diagram showing a raw material supplying equipment 102 to a methane fermentation tank according to an embodiment of the present invention. The difference from the raw material supplying equipment 101 to a methane fermentation tank of the first embodiment is that this embodiment is provided with a heated excess sludge supplying path 13 branching off from the excess sludge supplying path 12, and a heating device 7 for heating the excess sludge is installed in the heated excess sludge supplying path 13. The same symbols are used for devices common to the raw material supplying equipment 101 to a methane fermentation tank of the first embodiment and the raw material supplying equipment 102 to a methane fermentation tank of the second embodiment.

[0042] (warming device) The heating device 7 is a device for heating the raw sludge. The heating device 7 has a heat exchanger 7a as a heater. The heat exchanger 7a is an indirect heat exchanger that heats the raw sludge. Hot water is supplied to the heat exchanger 7a from a hot water source such as a boiler (not shown). The excess sludge passing through the heated excess sludge supply path 13 is heated by indirect contact with the hot water in the heat exchanger 7a. As the temperature of the excess sludge increases, the viscosity of the excess sludge decreases. The excess sludge is heated to 35 to 70°C, preferably 44 to 70°C. The heated excess sludge is supplied to the methane fermentation tank 2 via the supply path 1. In this embodiment, an indirect heating method using the heat exchanger 7a is adopted, but a direct heating method using an electric heater may also be adopted.

[0043] A valve V3 is installed between the branch point of the excess sludge supply path 12 and the heated excess sludge supply path 13 and the heating device 7. As with the valves V1 and V2, the valve V3 may be switched by automatic control or manually.

[0044] Hereinafter, specific control of the valves V1, V2, and V3 by the controller 6 will be described with reference to the flowchart of FIG.

[0045] When control by the controller 6 is started, the controller 6 opens only the valve V1 of the primary sludge supply path 11 among the closed valves V1, V2, and V3 (step 11). If the controller 6 determines that the supply time of the primary sludge having a viscosity equal to or less than the predetermined value V1 to the supply path 1 reaches the predetermined time T3 (step 12: Yes), the controller 6 closes the valve V1 of the primary sludge supply path 11, closes the valve V2 of the excess sludge supply path 12, and opens the valve V3 of the heated excess sludge supply path 13 to supply heated excess sludge having a viscosity greater than the predetermined value V1 (hereinafter, heated excess sludge) to the supply path 1 (step 13). Next, when it is determined that the supply time of the heated excess sludge to the supply path 1 reaches the predetermined time T4 (step 14: Yes), the valve V1 of the primary sludge supply path 11 is closed, the valve V2 of the excess sludge supply path 12 is opened, and the valve V3 of the heated excess sludge supply path 13 is closed, so that the excess sludge having a viscosity of a predetermined value V1+α or more (hereinafter, non-heated excess sludge) is supplied to the supply path 1 (step 15). Next, when it is determined that the supply time of the non-heated excess sludge to the supply path 1 reaches the predetermined time T5 (step 16: Yes), the valve V1 of the primary sludge supply path 11 is opened, the valve V2 of the excess sludge supply path 12 is closed, and the valve V3 of the heated excess sludge supply path 13 is closed, so that the primary sludge is supplied to the supply path 1 (step 17).

[0046] Here, the predetermined times T3, T4, and T5 can be set based on the generation rates of the primary sludge and excess sludge, or the hydraulic retention time (HRT) and inner volume of the piping of the methane fermentation tank 2. The predetermined times T3, T4, and T5 may be set to the same time, or may be set to different times, or only one of them may be set to a different time. The predetermined times T3, T4, and T5 may be set to a value of, for example, 5 minutes or more and 2 hours or less, preferably 10 minutes or more and 30 minutes or less.

[0047] In this embodiment, the primary settling sludge, heated excess sludge, and non-heated excess sludge are periodically supplied to the supply path 1 in that order, thereby preventing solids from adhering within the supply path 1. The order in which the raw materials are supplied to the supply path 1 is not limited to the above order, and the raw materials may be supplied to the supply path 1 in the order of, for example, primary settling sludge, non-heated excess sludge, and heated excess sludge.

[0048] <Third embodiment> Next, a third embodiment of the present invention will be described. Fig. 5 is a diagram showing equipment 103 for supplying raw material to a methane fermentation tank according to an embodiment of the present invention. The difference from equipment 101 for supplying raw material to a methane fermentation tank of the first embodiment is that a flow rate measuring unit 14 is further provided in the supply path 1. The same symbols are used for devices common to equipment 101 for supplying raw material to a methane fermentation tank of the first embodiment and equipment 103 for supplying raw material to a methane fermentation tank of the third embodiment.

[0049] (Flow measurement section) The flow rate measuring unit 14 is a device that measures the flow rate of the raw sludge passing through the supply path 1. The flow rate measured by the flow rate measuring unit 14 may be a volumetric flow rate or a mass flow rate. The flow meter 14a of the flow rate measuring unit 14 is installed in the supply path 1 downstream of the pump 10, as shown in FIG.

[0050] Volumetric flow rate is the volume of fluid passing through a surface per unit time. Specifically, the volumetric flow rate Q(m 3 / s) is the cross-sectional area of ​​the pipe (supply path 1) in A (m 2), and the average flow velocity is v (m / s), it can be calculated by multiplying the cross-sectional area A and the average flow velocity v, as shown in the following equation (1).

[0051] [Formula 1] TIFF2025030446000002.tif12164

[0052] Mass flow rate is the mass of a fluid passing through a surface per unit time. Specifically, mass flow rate M (Kg / s) is expressed as the density d (Kg / m 3 ), the cross-sectional area of ​​the pipe (supply path 1) is A (m 2 ), and the average flow velocity is v (m / s), it can be calculated by the product of density d, cross-sectional area A, and average flow velocity v, as shown in the following equation (2).

[0053] [Formula 2] TIFF2025030446000003.tif13164

[0054] As described above, the flow rate measured by the flow rate measuring unit 14 may be either a volumetric flow rate or a mass flow rate, but in this embodiment, an example will be described in which the volumetric flow rate is measured by the flow rate measuring unit 14. When the volumetric flow rate Q of the excess sludge passing through the supply path 1 is less than a predetermined value Q1, it is determined that adhesion or clogging has occurred in the supply path 1, and the valve is switched to supply low-viscosity primary settling sludge to the supply path 1. Note that adhesion or clogging in the supply path 1 may be detected by, for example, visual or audible confirmation by an operator other than measurement by the flow meter 14a, and the valve may be switched manually.

[0055] An ultrasonic flow meter, an electromagnetic flow meter, or the like is used as the flow meter 14a of the flow measurement unit 14. In this embodiment, the flow measurement unit 14 and the controller 6 are connected by a cable, and a detection signal from the flow meter is input to the controller 6 via the cable.

[0056] The valve switching control section 6b of the controller 6 may function, for example, as follows, based on the volumetric flow rate measured by the flowmeter 14a.

[0057] Hereinafter, specific control of the valves V1 and V2 by the controller 6 will be described with reference to the flowchart of FIG.

[0058] 6(a), when control by the controller 6 is started, of the closed valves V1 and V2, the controller 6 opens only the valve V1 in the primary sludge supply path 11 (step 21). If the controller 6 determines that the supply time of the primary sludge having a viscosity equal to or less than the predetermined value V1 to the supply path 1 reaches the predetermined time T6 (step 22: Yes), it closes the valve V1 in the primary sludge supply path 11 and opens the valve V2 in the excess sludge supply path 12 to supply the excess sludge having a viscosity greater than the predetermined value V1 to the supply path 1 (step 23). Next, when the controller 6 determines based on the measurement value of the flow rate measuring unit 14 that the volumetric flow rate Q in the excess sludge supply path 1 is less than the predetermined value Q1 (step 24: Yes), it opens the valve V1 in the primary sludge supply path 11 and closes the valve V2 in the excess sludge supply path 12 to supply the primary sludge to the supply path 1 (step 25). Next, when the controller 6 determines based on the measurement value of the flow rate measuring unit 14 that the volumetric flow rate Q in the primary sludge supply path 1 is equal to or greater than the predetermined value Q1 (step 26: Yes), it supplies the primary sludge to the supply path 1 until the supply time reaches the predetermined time T6 (step 21).

[0059] Here, the predetermined time T6 can be set based on the generation rates of the primary sludge and excess sludge, or the hydraulic retention time (HRT) and inner volume of the pipe of the methane fermentation tank 2. The predetermined time T6 may be set to a value of, for example, 5 minutes or more and 2 hours or less, preferably 10 minutes or more and 30 minutes or less.

[0060] In this embodiment, the flow rate measuring unit 14 can monitor adhesion or clogging in the supply path 1 based on the volumetric flow rate of excess sludge flowing through the supply path 1. Therefore, when adhesion or clogging occurs, the raw sludge to be supplied to the supply path 1 can be switched to the primary sludge by opening and closing the valves V1 and V2 (switching unit). As a result, it is possible to prevent blockage in the supply path 1 while reducing the load on the pump 10 of the supply path 1. In this embodiment, the primary sludge is supplied to the supply path 1 until the predetermined time T6 is reached. However, as shown in FIG. 6(b), for example, a predetermined time T7 different from the predetermined time T6 may be set and the primary sludge may be supplied to the supply path 1 until the predetermined time T7 is reached (step 22'), or as shown in FIG. 6(c), a predetermined amount Q2 may be set and the primary sludge may be supplied to the supply path 1 until the predetermined amount Q2 is reached (step 22''). In addition, the processes of the flowcharts shown in FIG. 6(a) to FIG. 6(c) may be performed in combination. The values ​​of the predetermined time T7 and the predetermined amount Q2 are not particularly limited, but it is preferable that the predetermined time T7 is smaller than the predetermined time T6. The predetermined time T7 may be, for example, 5 minutes or more and 2 hours or less, preferably 10 minutes or more and 30 minutes or less.

[0061] (effect) In this embodiment, the method for supplying raw materials to a methane fermentation tank involves supplying primary settling sludge and excess sludge (two or more organic wastes with different viscosities or solid concentrations) to a methane fermentation tank 2 via a common supply path 1 in a predetermined order.

[0062] According to the above-mentioned operating method, the following effects can be obtained.

[0063] By supplying the primary settling sludge and excess sludge (raw materials with different viscosities or solid concentrations) to the methane fermentation tank 2 in a specified order via a common supply path 1, the raw materials can be supplied to the methane fermentation tank 2 without clogging the supply path 1 or without using lubricants or complex pressure control. In addition, since multiple raw materials are supplied to the methane fermentation tank 2 collectively via a single supply path 1, the cost of the equipment can be reduced and the burden of maintenance can be reduced. In addition, by alternately sending the primary settling sludge and excess sludge (raw materials with different viscosities or solid concentrations), the pressure loss can be reduced and the pump capacity can be made smaller. In addition, since the raw materials are mixed within the supply path 1 and there is no need to install a mixing tank upstream of the methane fermentation tank 2, the equipment cost can be reduced.

[0064] In addition, the predetermined order is preferably such that organic wastes of the same viscosity or solid matter concentration are not continuously supplied. According to this, by not continuously supplying organic wastes of the same viscosity or solid matter concentration, the raw material can be supplied to the methane fermentation tank 2 without clogging the raw material supply path without using a lubricant or performing complex pressure control. Note that organic wastes of the same viscosity but different solid matter concentrations may be continuously supplied. In addition, organic wastes of the same solid matter concentration may be continuously supplied if they have different viscosities.

[0065] The predetermined order may be such that, after the excess sludge (organic waste having a viscosity or solid concentration greater than a predetermined value or the highest viscosity or solid concentration) among the primary settling sludge and excess sludge (two or more organic wastes having different viscosities or solid concentrations) is supplied to the methane fermentation tank 2, the primary settling sludge (organic waste other than the organic waste having a viscosity equal to or less than the predetermined value, or the highest viscosity or solid concentration among two or more organic wastes having different viscosities or solid concentrations) is supplied to the methane fermentation tank 2. According to this, by supplying the primary settling sludge and excess sludge (raw materials having different viscosities or solid concentrations) to the methane fermentation tank 2 in the predetermined order via the common supply path 1, the raw materials can be supplied to the methane fermentation tank 2 without clogging the supply path without using a lubricant or performing complex pressure control.

[0066] The predetermined order is preferably such that the primary sludge (organic waste with the lowest viscosity or solid concentration) among the primary sludge and excess sludge (two or more organic wastes with different viscosities or solid concentrations) is supplied first to the methane fermentation tank 2. Here, "first" means when the operation of the methane fermentation tank 2 starts, or when operation is resumed after a temporary halt. According to this, by supplying the primary sludge (organic waste with the lowest viscosity) among the primary sludge and excess sludge (two or more organic wastes with different viscosities or solid concentrations) to the methane fermentation tank 2 first, it is possible to supply the raw material to the methane fermentation tank 2 without clogging the supply path, without using a lubricant or performing complex pressure control.

[0067] The present invention is not limited to the above-described embodiment. The configurations of the above-described embodiment may be appropriately combined, or various modifications may be made to the above-described embodiment. For example, the above-described embodiment may be modified as follows.

[0068] In the above embodiment, an example has been shown in which a heating device for heating the primary sludge is not provided, but a heating device for heating the primary sludge may be provided.

[0069] In the above embodiment, an example has been shown in which a flow rate adjustment valve is not provided as a flow rate adjustment unit that adjusts the flow rate of the supply raw material flowing through the supply path 1, but a flow rate adjustment valve may be provided as a flow rate adjustment unit that adjusts the flow rate of the supply raw material flowing through the supply path 1. In this case, the opening degree of the flow rate adjustment valve may be adjusted by automatic control performed by the controller 6, or may be adjusted manually.

[0070] In the above embodiment, an example was shown in which a concentration meter for measuring the solid concentration of the raw sludge is not provided, but a concentration meter for measuring the solid concentration of the raw sludge may be provided.

[0071] In the explanation of the third embodiment, an example was shown in which a heating device for heating the raw sludge is not provided, but a heating device for heating the raw sludge may be provided. [Industrial Applicability]

[0072] The method and equipment for supplying raw materials to a methane fermentation tank of the present invention can be used to decompose various organic waste materials, such as sewage sludge, sewage sludge, agricultural village wastewater sludge, septic tank sludge, food waste (food biomass) including food waste, construction waste, lignocellulosic waste materials including used and discarded paper, agricultural residues, and livestock manure, and to generate methane using the decomposition products as a raw material. [Explanation of symbols]

[0073] 1: Supply route 2: Methane fermentation tank 6: Controller 6a: Timing section 6b: Valve switching control section 7: Warming device 7a: Heat exchanger 11: Primary sludge supply route 12: Excess sludge supply route 13: Heated excess sludge supply route 14: Flow rate measurement section 14a:Flow meter 101, 102, 103: Raw material supply equipment V1~3: Valve (switching part)

Claims

1. A method for supplying raw material to a methane fermentation tank, comprising supplying two or more organic wastes having different viscosities or solid concentrations to the methane fermentation tank in a predetermined order via a common supply path.

2. 2. The method for supplying a raw material to a methane fermenter according to claim 1, wherein the predetermined order is such that organic wastes having the same viscosity or the same solid matter concentration are not supplied consecutively.

3. 3. The method for supplying raw materials to a methane fermentation tank according to claim 1 or 2, wherein the predetermined order is such that, after supplying to the methane fermentation tank an organic waste having a viscosity or solid concentration greater than a predetermined value or having the highest viscosity or solid concentration among two or more organic wastes having different viscosities or solid concentrations, an organic waste other than the organic waste having a viscosity or solid concentration equal to or less than the predetermined value or having the highest viscosity or solid concentration among two or more organic wastes having different viscosities or solid concentrations is supplied to the methane fermentation tank.

4. 3. The method for supplying raw material to a methane fermentation tank according to claim 1 or 2, wherein the predetermined order is such that, among two or more organic wastes having different viscosities or solid concentrations, an organic waste having the lowest viscosity or solid concentration is supplied to the methane fermentation tank first.

5. A raw material supply facility for a methane fermentation tank, comprising a common supply path for supplying two or more organic wastes having different viscosities or solid concentrations to the methane fermentation tank in a predetermined order.

6. The equipment for supplying raw material to a methane fermentation tank according to claim 5, wherein the supply path is a pipe.

7. A switching unit that switches the order in which two or more organic wastes having different viscosities or solid concentrations are supplied to the methane fermentation tank; a flow rate measuring unit that measures a flow rate of the organic waste flowing through the supply path; The equipment for supplying raw material to a methane fermentation tank according to claim 5 or 6, comprising:

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