Digestion system and heating control method

Abstract

To provide a digestion system and a heating control method for accurately controlling a temperature within a tank.SOLUTION: A system comprises: a first tank that digests surplus sludge; a first pipe that supplies the surplus sludge to the first tank; a first heater that heats the surplus sludge in the first pipe with a fluid; a second tank that stores the surplus sludge before being heated by the first heater and the surplus sludge after being heated by the first heater; a second pipe that circulates the surplus sludge between the first heater and the second tank; and a control device that, on the basis of a temperature of the surplus sludge in the second tank, controls at least one of supply of the surplus sludge to the second pipe and supply of the surplus sludge to the first tank.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a fire extinguishing system and a method for controlling heat. [Background technology]

[0002] In a digestion system having a tank (hereinafter also referred to as a digestion tank) for digesting the material to be treated (for example, organic matter contained in primary sludge and excess sludge), a technology has been proposed that achieves efficient digestion of the material to be treated by maintaining the temperature inside the tank at an appropriate temperature (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special table 2011-516246 publication Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described fire extinguishing system, for example, it is desirable to precisely control the temperature inside the tank so that the temperature inside the tank is maintained at an appropriate temperature. [Means for solving the problem]

[0005] The digestion system of the present disclosure comprises a first tank for digesting excess sludge, a first pipe for supplying the excess sludge to the first tank, a first heater for heating the excess sludge in the first pipe using a fluid, a second tank for storing the excess sludge before being heated by the first heater, the excess sludge before being heated by the first heater, and the excess sludge heated by the first heater, a second pipe for circulating the excess sludge between the first heater and the second tank, and a control device for controlling at least one of the supply of the excess sludge to the second pipe and the supply of the excess sludge to the first tank based on the temperature of the excess sludge in the second tank. [Effects of the Invention]

[0006] The extinguishing system and heating control method disclosed herein make it possible to precisely control the temperature inside the tank. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a processing system 1000 according to the first embodiment. [Figure 2] FIG. 2 is a diagram illustrating the configuration of the temperature adjustment system 100 according to the first embodiment. [Figure 3] FIG. 3 is a diagram illustrating the hardware configuration of the control device 200 in the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating the function of the control device 200 in the first embodiment. [Figure 5] FIG. 5 is a flowchart illustrating the temperature control process in the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating the configuration of a temperature adjustment system 100 in a first modified example. [Figure 7] FIG. 7 is a diagram illustrating the configuration of a temperature adjustment system 100 in a second modified example. [Figure 8] FIG. 8 is a diagram illustrating the configuration of a temperature adjustment system 100 in a third modified example. [Figure 9] FIG. 9 is a diagram illustrating the configuration of a temperature adjustment system 100 in a fourth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, such descriptions should not be interpreted in a limiting sense, and do not limit the subject matter described in the claims. Furthermore, various changes, substitutions, and modifications can be made without departing from the spirit and scope of the present disclosure. Furthermore, different embodiments can be combined as appropriate.

[0009] [Processing system 1000 according to the first embodiment] First, a processing system 1000 according to the first embodiment will be described. Fig. 1 is a diagram illustrating the configuration of the processing system 1000 according to the first embodiment.

[0010] The treatment system 1000 in this embodiment is, for example, a water treatment system that treats liquid such as sewage (hereinafter also referred to as water to be treated).

[0011] 1, the treatment system 1000 includes, for example, a primary sedimentation tank 10, a tank 20 (hereinafter also referred to as a reaction tank 20), a final sedimentation tank 30, a thickening device 40, a thickening device 50, a tank 60 (hereinafter also referred to as a digestion tank 60), a temperature adjustment system 100, and a control device 200. Note that, hereinafter, the treatment system 1000 will also be referred to as a digestion system 1000.

[0012] The primary sedimentation tank 10 separates, for example, organic and other contaminants (e.g., solid organic matter) contained in the water to be treated. The separated contaminants (hereinafter also referred to as primary sludge) are then discharged to a concentration device 40 by, for example, a pump (not shown). The water to be treated after the separation of contaminants by sedimentation is then discharged to a digestion tank 60 by, for example, a pump (not shown).

[0013] The reaction tank 20 is a tank that treats the water to be treated by biological treatment such as the standard activated sludge method. Specifically, the reaction tank 20 decomposes organic matter (e.g., soluble organic matter) contained in the water to be treated, for example, by microorganisms (hereinafter also referred to as activated sludge) propagated in the reaction tank 20. Then, after the organic matter has been decomposed by the activated sludge, the water to be treated is discharged from the reaction tank 20 to the final sedimentation tank 30 by, for example, overflow.

[0014] The final settling tank 30, for example, separates and discharges activated sludge contained in the water to be treated discharged from the reaction tank 20. Then, a part of the settled and separated activated sludge (hereinafter also referred to as excess sludge) is discharged to the thickening device 50, for example, by a pump (not shown). Another part of the settled and separated activated sludge (hereinafter also referred to as returned sludge) is returned to the reaction tank 20, for example, by a pump (not shown). Furthermore, the water to be treated after the activated sludge separation is discharged to a downstream sterilization treatment device (not shown) by, for example, overflow. Thereafter, the sterilization treatment device sterilizes the water to be treated discharged from the final settling tank 30, for example, and releases the sterilized treated water into a river or the like.

[0015] The thickening device 40 thickens, for example, the primary sludge discharged from the primary sedimentation tank 10. The thickened primary sludge is then discharged into the digestion tank 60 by, for example, a pump (not shown). The liquid separated from the primary sludge by thickening is returned to the primary sedimentation tank 10 by, for example, a pump (not shown).

[0016] The thickening device 50 thickens excess sludge discharged from, for example, the final settling tank 30. The thickened excess sludge is then discharged to the digestion tank 60 by, for example, a pump (not shown). Note that the liquid separated from the excess sludge by the thickening is returned to the final settling tank 30 by, for example, a pump (not shown).

[0017] In the digestion tank 60, for example, anaerobic bacteria in the digestion tank 60 anaerobically digest (decompose) organic matter contained in the primary sludge supplied from the thickener 40 and the excess sludge supplied from the thickener 50 through a biological reaction, thereby producing digested sludge. Specifically, the anaerobic bacteria in the digestion tank 60 produce digestion gases such as methane gas (hereinafter simply referred to as digestion gas) during the digestion process. Note that the temperature of the digested sludge (digestion liquid) in the digestion tank 60 is preferably maintained between 35°C and 39°C (hereinafter, this temperature range is also referred to as the optimum temperature) in order to efficiently promote biological reactions and improve the digestion rate.

[0018] The temperature adjustment system 100 adjusts the temperature of excess sludge, for example, before it is supplied to the digestion tank 60. Specifically, the temperature adjustment system 100 heats the excess sludge, for example, before it is supplied to the digestion tank 60. The temperature adjustment system 100 will be described below.

[0019] [Temperature Adjustment System 100 in the First Embodiment] FIG. 2 is a diagram illustrating the configuration of the temperature adjustment system 100 according to the first embodiment.

[0020] As shown in FIG. 2, the temperature adjustment system 100 in this embodiment includes, for example, a heater 110 (hereinafter also referred to as a first heater 110), a storage tank 120, a storage tank 130, a pump P1, a pump P2, and a pump P3.

[0021] The storage tank 120 is a tank that stores excess sludge supplied from the thickening device 50 via, for example, a line L1.

[0022] The pump P1 is provided, for example, in the line L2, and supplies excess sludge supplied from the storage tank 120 to the storage tank . The line L2 is, for example, a pipe that connects the storage tank 120 and the storage tank .

[0023] The storage tank 130 is a tank that stores excess sludge supplied from the storage tank 120 via, for example, a line L2.

[0024] Pump P2 is provided, for example, on line L4, and supplies excess sludge from storage tank 130 to heater 110, and supplies the excess sludge whose temperature has been adjusted by heater 110 to digestion tank 60. Line L4 is, for example, a pipe that sequentially connects storage tank 130, heater 110, and digestion tank 60. Hereinafter, lines L2 and L4 will be collectively referred to simply as the first pipe.

[0025] The heater 110 heats the excess sludge supplied from the storage tank 130 via, for example, a line L4. Specifically, the heater 110 is, for example, a heat exchanger that conditions the excess sludge using a fluid (for example, a fluid such as hot water) circulating through a line L3. The line L3 is, for example, a circulation pipe that connects the heater 110 to a heat source (not shown).

[0026] The heat source for heating the fluid supplied to the heater 110 may be, for example, a heat exchanger that heats the fluid using waste heat from exhaust gas generated in an incinerator (not shown) that incinerates the digested sludge discharged from the digester tank 60. The heat source for heating the fluid supplied to the heater 110 may be, for example, a heat exchanger that heats the fluid using waste heat generated in conjunction with power generation using the digester gas discharged from the digester tank 60. The heat source for heating the fluid supplied to the heater 110 may be, for example, a water heater that heats the fluid using the digester gas discharged from the digester tank 60.

[0027] The pump P3 is provided, for example, on the line L5, and supplies the excess sludge supplied from the heater 110 to the storage tank 130. The line L5 is, for example, a pipe that connects the storage tank 130 to a position on the line L4 between the heater 110 and the pump P2.

[0028] Furthermore, line L5 and a portion of line L4 (the portion from the storage tank 130 to a position between the heater 110 and the pump P2) form a circulation pipe (hereinafter also referred to as the second pipe) that can circulate excess sludge, for example, between the heater 110 and the storage tank 130.

[0029] That is, the treatment system 1000 in this embodiment can, for example, circulate excess sludge supplied from the storage tank 120 via line L2 between the storage tank 130 and the heater 110. Therefore, the treatment system 1000 in this embodiment circulates excess sludge between the heater 110 and the storage tank 130, and repeatedly heats the excess sludge in the heater 110, for example, until the temperature of the excess sludge stored in the storage tank 130 reaches a required temperature.

[0030] As a result, the treatment system 1000 of this embodiment can, for example, stabilize the temperature of the excess sludge supplied to the digestion tank 60. Therefore, the treatment system 1000 of this embodiment can, for example, accurately adjust the temperature of the digested sludge in the digestion tank 60, and can control the temperature of the digested sludge in the digestion tank 60 to maintain it at an appropriate temperature. Therefore, the treatment system 1000 of this embodiment can, for example, suppress a decrease in the digestion rate in the digestion tank 60.

[0031] [Control device 200 in the first embodiment] Next, the control device 200 in the first embodiment will be described. Fig. 3 is a diagram illustrating the hardware configuration of the control device 200 in the first embodiment. Fig. 4 is a diagram illustrating the function of the control device 200 in the first embodiment.

[0032] The control device 200 performs, for example, control of the temperature of the excess sludge supplied to the digestion tank 60 (hereinafter also referred to as temperature adjustment control).

[0033] Specifically, the control device 200 is, for example, an electronic device having an electronic circuit, as shown in Fig. 3. More specifically, the control device 200 is, for example, a computer device having a CPU 201 which is a processor, a memory 202, a communication device 203, and a storage medium 204. Each unit is connected to each other, for example, via a bus 205.

[0034] The storage medium 204 has, for example, a program storage area (not shown) that stores a program 210 for performing temperature adjustment control. The storage medium 204 also has, for example, an information storage area 230 that stores information used when performing temperature adjustment control. The storage medium 204 may be, for example, a hard disk drive (HDD) or a solid state drive (SSD).

[0035] The CPU 201 performs temperature adjustment control by executing a program 210 loaded into the memory 202 from the storage medium 204, for example.

[0036] The communication device 203 accesses an operation terminal (not shown) through which an operator inputs necessary information, for example, via a network (not shown) such as the Internet.

[0037] 4, the control device 200 acquires the temperature (i.e., the temperature of the excess sludge in the storage tank 130) measured by, for example, a thermometer T attached to the storage tank 130. Thereafter, the control device 200 performs temperature adjustment control by using, for example, the acquired temperature.

[0038] The electronic circuitry of the control device 200 may be, for example, a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). The temperature adjustment control may be performed by, for example, the FPGA or the ASIC.

[0039] [Temperature Control Process in the First Embodiment] Next, the temperature control process in the first embodiment will be described. Fig. 5 is a flowchart illustrating the temperature control process in the first embodiment. Note that the following description will be given assuming that the temperature adjustment control is performed automatically by the control device 200, but is not limited to this. Specifically, the temperature adjustment control may be performed manually by an operator, for example.

[0040] The control device 200 waits, for example, until it is time to execute temperature adjustment control (hereinafter also referred to as control execution time). The control execution time may be a regular time such as every minute.

[0041] Then, for example, when the control execution time arrives, the control device 200 acquires the temperature (temperature of the excess sludge in the storage tank 130) measured by the thermometer T (step S1 in FIG. 5).

[0042] Next, the control device 200 determines whether or not the temperature acquired in step S1 satisfies a predetermined condition (hereinafter also simply referred to as the predetermined condition) (step S2 in FIG. 5).

[0043] Note that, although the following description will be given of a case where the control device 200 performs control from step S2 onwards by using the temperature measured by the thermometer T, the present invention is not limited to this. Specifically, the control device 200 may perform control from step S2 onwards by using a temperature measured by another thermometer, for example. Specifically, the control device 200 may perform control from step S2 onwards by using a temperature (the temperature of the excess sludge before it is supplied to the storage tank 130) measured by a thermometer (not shown) provided at a position on the line L2 between the heater 110 and the storage tank 130, for example.

[0044] As a result, for example, if it is determined that the temperature acquired in step S1 satisfies a predetermined condition (YES in step S2 in FIG. 5), the control device 200 adjusts the temperature of the excess sludge in the storage tank 130 (step S3 in FIG. 5).

[0045] On the other hand, for example, if it is determined that the temperature acquired in step S1 does not satisfy the predetermined condition (NO in step S2 in FIG. 5), the control device 200 does not perform step S3.

[0046] Specifically, as shown in Figure 2, when adjusting the temperature of excess sludge supplied from the storage tank 120 via line L2 (heating the excess sludge), the control device 200 controls to open valve V1 located downstream of pump P1 on line L2 and upstream of the storage tank 130, controls to close valve V2 located downstream of pump P2 on line L4 and upstream of the digestion tank 60, and controls to open valve V3 located on line L5.

[0047] That is, in this case, the control device 200 controls, for example, pumps P1 and P3, so that the excess sludge supplied from the storage tank 120 via the storage tank 130 is heated in the heater 110, and further controls so that the excess sludge heated in the heater 110 is supplied to the storage tank 130.

[0048] Then, for example, when a predetermined amount of excess sludge has been stored in the storage tank 130, the control device 200 closes the valve V1, acquires the temperature of the excess sludge stored in the storage tank 130 (the temperature measured by the thermometer T), and determines whether the acquired temperature exceeds a predetermined threshold value (hereinafter simply referred to as the threshold value). The threshold value is, for example, a temperature that can be determined to be necessary as the temperature of the excess sludge to be supplied to the digestion tank 60.

[0049] As a result, for example, if it is determined that the acquired temperature is above the threshold value, the control device 200 determines that the predetermined condition is not satisfied, and performs control to open valve V2 and close valve V3, and also controls pump P2, thereby controlling the excess sludge stored in the storage tank 130 to be supplied to the digester tank 60 via the heater 110. Thereafter, the control device 200 performs control to open valve V1, close valve V2, and open valve V3, and also controls pumps P1 and P3, thereby controlling the supply of new excess sludge from the storage tank 120 to the storage tank 130.

[0050] When the excess sludge stored in the storage tank 130 is supplied to the digestion tank 60, the control device 200 may, for example, reduce the amount of fluid supplied to the heater 110 via line L3. In other words, in this case, the control device 200 may, for example, perform control so that the excess sludge supplied from the storage tank 130 to the digestion tank 60 is not overheated in the heater 110 or is not reheated.

[0051] In addition, the threshold value may be a temperature lower than the temperature required for the excess sludge supplied to the digestion tank 60, for example, taking into account that the excess sludge supplied from the storage tank 130 to the digestion tank 60 is further heated in the heater 110.

[0052] In the following description, the valve V1 is provided in the line L2, and the control device 200 controls the opening and closing of the valve V1, but this is not limiting. Specifically, for example, if a check valve (not shown) is provided in the line L2 downstream of the pump P1 and upstream of the storage tank 130, the valve V1 may not be provided in the line L2.

[0053] Furthermore, the following description will be given assuming that pump P2 is provided in line L2 and pump P3 is provided in line L5, and that control device 200 controls pump P2 and pump P3, but this is not limiting. Specifically, for example, if another pump (not shown) is provided in line L4 downstream of storage tank 130 and upstream of the branch point with line L5 (for example, downstream of storage tank 130 and upstream of heater 110 in line L4), pumps P2 and P3 may not be provided in line L4 and line L5. In this case, control device 200 may control the other pump instead of pump P2 and pump P3, for example.

[0054] On the other hand, for example, when it is determined that the acquired temperature does not exceed the threshold value, the control device 200 determines that the predetermined condition is satisfied, and controls the pump P3 to supply the excess sludge stored in the storage tank 130 to the heater 110. That is, in this case, the control device 200 reheats the excess sludge stored in the storage tank 130 in the heater 110, for example.

[0055] Thereafter, for example, if it is determined that the temperature (temperature measured by thermometer T) of the excess sludge resupplied from heater 110 to storage tank 130 exceeds the threshold value, in other words, if it is determined that the temperature of the excess sludge stored in storage tank 130 by being reheated in heater 110 exceeds the threshold value, the control device 200 controls valve V2 to open and valve V3 to close, and also controls pump P2 so that the excess sludge stored in storage tank 130 is supplied to digestion tank 60 via heater 110.

[0056] On the other hand, for example, if it is determined that the temperature (temperature measured by thermometer T) of the excess sludge supplied again from heater 110 to storage tank 130 still does not exceed the threshold value, in other words, if it is determined that the temperature of the excess sludge stored in storage tank 130 still does not exceed the threshold value despite being heated again in heater 110, the control device 200 repeatedly supplies excess sludge to heater 110 and repeatedly heats the excess sludge in heater 110 until the temperature of the excess sludge supplied from heater 110 to storage tank 130 exceeds the threshold value.

[0057] Thus, the treatment system 1000 of this embodiment includes, for example, a digestion tank 60 (hereinafter also referred to as the first tank) that digests excess sludge, lines L2 and L4 that supply the excess sludge to the digestion tank 60, a heater 110 that heats the excess sludge in line L2 with a fluid, a storage tank 130 (hereinafter also referred to as the second tank) that stores the excess sludge before being heated by the heater 110 and the excess sludge heated by the heater 110, and lines L4 and L5 that circulate the excess sludge between the heater 110 and the storage tank 130. The treatment system 1000 of this embodiment also includes, for example, a control device 200 that controls at least one of the supply of excess sludge to line L4 and the supply of excess sludge to the digestion tank 60 based on the temperature of the excess sludge in the storage tank 130.

[0058] Specifically, in the treatment system 1000 of this embodiment, the heater 110 heats excess sludge supplied from the storage tank 130, for example. Also, in the treatment system 1000 of this embodiment, the line L5 supplies excess sludge heated in the heater 110 to the storage tank 130, for example. Then, in the treatment system 1000 of this embodiment, when the temperature of the excess sludge supplied from the line L5 to the storage tank 130 is below a threshold, the control device 200 controls the treatment system 1000 of this embodiment so that the excess sludge is supplied again from the storage tank 130 to the heater 110, and further so that the excess sludge heated in the heater 110 is supplied again to the line L5. Furthermore, in the treatment system 1000 of this embodiment, for example, when the temperature of the excess sludge supplied from line L5 to the storage tank 130 exceeds a threshold value, the control device 200 controls the storage tank 130 to supply the excess sludge again to the heater 110, and further controls the excess sludge heated in the heater 110 to be supplied to the digestion tank 60.

[0059] That is, the treatment system 1000 in this embodiment can, for example, circulate excess sludge supplied from the storage tank 120 via line L2 between the storage tank 130 and the heater 110. Therefore, the treatment system 1000 in this embodiment circulates excess sludge between the heater 110 and the storage tank 130, and repeatedly heats the excess sludge in the heater 110, for example, until the temperature of the excess sludge stored in the storage tank 130 reaches a required temperature.

[0060] As a result, the treatment system 1000 of this embodiment can, for example, stabilize the temperature of the excess sludge supplied to the digestion tank 60. Therefore, the treatment system 1000 of this embodiment can, for example, accurately adjust the temperature of the digested sludge in the digestion tank 60, and can control the temperature of the digested sludge in the digestion tank 60 to maintain it at an appropriate temperature. Therefore, the treatment system 1000 of this embodiment can, for example, suppress a decrease in the digestion rate in the digestion tank 60.

[0061] The processing system 1000 in this embodiment may include, for example, a plurality of sets of heaters 110, reservoirs 130, pumps P1, P2, P3, lines L2, L4, L5, valves V1, V2, and V3. The control device 200 may perform temperature adjustment control in parallel using each set of equipment. In this case, the control device 200 may perform control such that the execution timings of the temperature adjustment control using each set of equipment are different from each other.

[0062] As a result, the treatment system 1000 in this embodiment is able to perform temperature adjustment control on all excess sludge supplied from the concentrating device 50, even if the amount of excess sludge supplied from the concentrating device 50 (e.g., the amount supplied per unit time) is not constant.

[0063] Furthermore, in the above example, the heater 110 is provided on the line L4, and is a facility downstream of the storage tank 130, but the present invention is not limited to this. Specifically, the heater 110 may be provided on the line L2, for example, and be a facility upstream of the storage tank 130. Furthermore, in the above example, the temperature adjustment system 100 has a line L5 that resupplies the excess sludge supplied from the heater 110 to the storage tank 130 (the storage tank 130 provided upstream of the heater 110), but the present invention is not limited to this. Specifically, the temperature adjustment system 100 may have, for example, a line (not shown) that resupplies the excess sludge stored in the storage tank 130 to the heater 110 (the heater 110 provided upstream of the storage tank 130) instead of the line L5.

[0064] [Temperature adjustment system 100(1) in modified example] Next, a temperature adjustment system 100 in a first modified example will be described. Fig. 6 is a diagram illustrating the configuration of the temperature adjustment system 100 in the first modified example. Below, differences from the temperature adjustment system 100 in the first embodiment will be described.

[0065] 6, the temperature adjustment system 100 in this modification differs from the temperature adjustment system 100 in the first embodiment in that, for example, a heater 110 is provided in a line L6. The line L6 is, for example, a circulation pipe that connects the storage tank 130 and the heater 110. The temperature adjustment system 100 in this modification further includes, for example, a pump P4.

[0066] The pump P4 is provided, for example, on the line L6, and supplies the excess sludge supplied from the heater 110 to the storage tank .

[0067] The second pipe in this modification is different from that in the temperature adjustment system 100 in the first embodiment, and is formed by, for example, a line L6.

[0068] As shown in Figure 6, when adjusting the temperature of excess sludge supplied from storage tank 120 via line L2 (heating the excess sludge), the control device 200 controls to open valve V1, close valve V2, and open valve V4 located between heater 110 and pump P4 on line L6.

[0069] In other words, in this case, the control device 200 controls, for example, pump P1 and pump P4, so that the excess sludge supplied from the storage tank 120 via the storage tank 130 is heated in the heater 110, and further controls so that the excess sludge heated in the heater 110 is supplied to the storage tank 130.

[0070] Then, for example, when a predetermined amount of excess sludge has been stored in the storage tank 130, the control device 200 closes the valve V1 and acquires the temperature of the excess sludge stored in the storage tank 130 (the temperature measured by the thermometer T), and determines whether the acquired temperature exceeds the threshold value.

[0071] As a result, for example, if it is determined that the acquired temperature is above the threshold value, the control device 200 determines that the predetermined condition is not satisfied, and performs control to open valve V2 and close valve V4, and also controls pump P2, thereby controlling the excess sludge stored in the storage tank 130 to be supplied to the digestion tank 60. Thereafter, the control device 200 performs control to open valve V1, close valve V2, and open valve V4, and also controls pumps P1 and P4, thereby controlling the supply of new excess sludge from the storage tank 120 to the storage tank 130.

[0072] On the other hand, for example, when it is determined that the acquired temperature does not exceed the threshold value, the control device 200 determines that the predetermined condition is satisfied, and controls the pump P4 to supply the excess sludge stored in the storage tank 130 to the heater 110. That is, in this case, the control device 200 reheats the excess sludge stored in the storage tank 130 in the heater 110, for example.

[0073] Thereafter, for example, if it is determined that the temperature (temperature measured by thermometer T) of the excess sludge resupplied from heater 110 to storage tank 130 exceeds the threshold value, in other words, if it is determined that the temperature of the excess sludge stored in storage tank 130 by being reheated in heater 110 exceeds the threshold value, the control device 200 controls valve V2 to open and valve V4 to close, and also controls pump P2 so that the excess sludge stored in storage tank 130 is supplied to digestion tank 60 via heater 110.

[0074] On the other hand, for example, if it is determined that the temperature (temperature measured by thermometer T) of the excess sludge supplied again from heater 110 to storage tank 130 still does not exceed the threshold value, in other words, if it is determined that the temperature of the excess sludge stored in storage tank 130 still does not exceed the threshold value despite being heated again in heater 110, the control device 200 repeatedly supplies excess sludge to heater 110 and repeatedly heats the excess sludge in heater 110 until the temperature of the excess sludge supplied from heater 110 to storage tank 130 exceeds the threshold value.

[0075] As described above, in the treatment system 1000 of this modified example, the heater 110 heats excess sludge supplied from the storage tank 130, for example. Furthermore, in the treatment system 1000 of this modified example, the line L6 supplies excess sludge heated in the heater 110 to the storage tank 130, for example. Furthermore, in the treatment system 1000 of this modified example, the control device 200 controls the excess sludge to be resupplied from the storage tank 130 to the line L6, for example, when the temperature of the excess sludge supplied from the line L6 to the storage tank 130 is below a threshold value. Furthermore, in the treatment system 1000 of this modified example, the control device 200 controls the excess sludge to be supplied from the storage tank 130 to the digestion tank 60, for example, when the temperature of the excess sludge supplied from the line L6 to the storage tank 130 is above a threshold value.

[0076] As a result, the treatment system 1000 of this modification can stabilize the temperature of the excess sludge supplied to the digestion tank 60, for example, as in the treatment system 1000 of the first embodiment. Therefore, the treatment system 1000 of this modification can accurately adjust the temperature of the digested sludge in the digestion tank 60, for example, and can control the temperature of the digested sludge in the digestion tank 60 to maintain it at an appropriate temperature. Therefore, the treatment system 1000 of this modification can suppress a decrease in the digestion rate in the digestion tank 60, for example.

[0077] [Temperature adjustment system 100(2) in modified example] Next, a temperature adjustment system 100 in a second modified example will be described. Fig. 7 is a diagram illustrating the configuration of the temperature adjustment system 100 in the second modified example. Below, differences from the temperature adjustment system 100 in the first modified example will be described.

[0078] 7, the temperature adjustment system 100 in this modification differs from the temperature adjustment system 100 in the first modification in that it does not have a pump P1 or a storage tank 130. In the temperature adjustment system 100 in this modification, for example, a line L6 connects the storage tank 120 and the heater 110.

[0079] As shown in Figure 7, when the control device 200 adjusts the temperature of excess sludge supplied from the concentration device 50 via line L1 (heating the excess sludge), it controls to close valve V2 and to open valve V4 located between the heater 110 and pump P4 in line L6.

[0080] That is, in this case, the control device 200 controls, for example, the pump P4, so that the excess sludge supplied from the storage tank 120 is heated in the heater 110, and further controls so that the excess sludge heated in the heater 110 is supplied to the storage tank 120.

[0081] Then, for example, when a predetermined amount of excess sludge is stored in the storage tank 120, the control device 200 acquires the temperature of the excess sludge stored in the storage tank 120 (the temperature measured by the thermometer T) and determines whether the acquired temperature exceeds the threshold value.

[0082] As a result, for example, if it is determined that the acquired temperature exceeds the threshold value, the control device 200 determines that the specified conditions are not met, and controls the valve V2 to open and the valve V4 to close, and also controls the pump P2 so that the excess sludge stored in the storage tank 120 is supplied to the digestion tank 60.

[0083] On the other hand, for example, when it is determined that the acquired temperature does not exceed the threshold value, the control device 200 determines that the predetermined condition is satisfied, and controls the pump P4 to supply the excess sludge stored in the storage tank 120 to the heater 110. That is, in this case, the control device 200 reheats the excess sludge stored in the storage tank 120 in the heater 110, for example.

[0084] As a result, for example, if it is determined that the temperature (temperature measured by thermometer T) of the excess sludge re-supplied from heater 110 to storage tank 120 exceeds the threshold value, in other words, if it is determined that the temperature of the excess sludge stored in storage tank 120 by being reheated in heater 110 exceeds the threshold value, the control device 200 controls valve V2 to open and valve V4 to close, and also controls pump P2 so that the excess sludge stored in storage tank 120 is supplied to digestion tank 60 via heater 110.

[0085] On the other hand, for example, if it is determined that the temperature (temperature measured by thermometer T) of the excess sludge supplied again from heater 110 to storage tank 120 still does not exceed the threshold value, in other words, if it is determined that the temperature of the excess sludge stored in storage tank 120 still does not exceed the threshold value despite being heated again in heater 110, the control device 200 repeatedly supplies excess sludge to heater 110 and repeatedly heats the excess sludge in heater 110 until the temperature of the excess sludge supplied from heater 110 to storage tank 120 exceeds the threshold value.

[0086] As a result, the treatment system 1000 of this modification can stabilize the temperature of the excess sludge supplied to the digestion tank 60, for example, as in the treatment system 1000 of the first embodiment. Therefore, the treatment system 1000 of this modification can accurately adjust the temperature of the digested sludge in the digestion tank 60, for example, and can control the temperature of the digested sludge in the digestion tank 60 to maintain it at an appropriate temperature. Therefore, the treatment system 1000 of this modification can suppress a decrease in the digestion rate in the digestion tank 60, for example.

[0087] [Temperature adjustment system 100(3) in modified example] Next, a temperature adjustment system 100 in a third modified example will be described. Fig. 8 is a diagram illustrating the configuration of the temperature adjustment system 100 in the third modified example. Below, differences from the temperature adjustment system 100 in the second modified example will be described.

[0088] As shown in FIG. 8, the temperature adjustment system 100 in this modification has a heater 140, unlike the temperature adjustment system 100 in the second modification, for example.

[0089] The heater 140 heats the excess sludge supplied from the storage tank 120 via, for example, a line L4. Specifically, the heater 140 is, for example, a heat exchanger that conditions the excess sludge using a fluid (for example, a fluid such as hot water) circulating through a line L7. The line L7 is, for example, a circulation pipe that connects the heater 140 to a heat source (not shown).

[0090] Here, in this modified example, the fluid circulating through the line L3 is a fluid with a lower temperature than the fluid circulating through the line L7, for example.

[0091] That is, in the treatment system 1000 of this modified example, for example, the excess sludge supplied to the storage tank 120 via the line L1 is heated in stages in the heater 110 and the heater 140, respectively.

[0092] As a result, the treatment system 1000 of this embodiment can suppress the heating temperature of the excess sludge in the heater 110. Therefore, the treatment system 1000 of this embodiment can sufficiently heat the excess sludge supplied to the digestion tank 60, even if the inner wall of the storage tank 120 has not been subjected to heat-resistant treatment, for example.

[0093] [Temperature adjustment system 100(4) in modified example] Next, a temperature adjustment system 100 in a fourth modified example will be described. Fig. 9 is a diagram illustrating the configuration of the temperature adjustment system 100 in the fourth modified example. Specifically, Fig. 9 is a diagram illustrating the configuration of the storage tank 130 in the fourth modified example. Below, differences from the temperature adjustment system 100 in the first embodiment will be described.

[0094] The storage tank 130 in this modification has, for example, a discharge pipe 130a that discharges excess sludge from the storage tank 130 at a predetermined height (hereinafter also referred to as a predetermined height). Note that the storage tank 130 may be, for example, a tank that is open at the top.

[0095] 9, the temperature adjustment system 100 in this modified example also has a storage tank 131 provided at a position adjacent to the storage tank 130. Specifically, the storage tank 131 is, for example, a tank that is open at the top and is located at a position where it can receive excess sludge discharged from the discharge pipe 130a of the storage tank 130.

[0096] The pump P2 in this modification supplies excess sludge supplied from the storage tank 131 to the digestion tank 60, for example.

[0097] That is, the excess sludge stored in the storage tank 130 is discharged from the discharge pipe 130a, for example, when the liquid level of the excess sludge in the storage tank 130 exceeds a predetermined height. Then, the excess sludge discharged from the discharge pipe 130a is stored in the storage tank 131, for example, and then supplied to the digestion tank 60 by the pump P2.

[0098] As a result, the temperature adjustment system 100 in this modified example can, for example, maintain a constant liquid level of excess sludge in the storage tank 130. Therefore, the temperature adjustment system 100 in this modified example can, for example, ensure a sufficient residence time in the storage tank 130 of the excess sludge supplied to the storage tank 130 (i.e., reaction time in the storage tank 130).

[0099] Furthermore, the storage tank 130 in this modification is a tank capable of releasing pressure in the line L2, for example. Therefore, the storage tank 130 in this modification is suitable for a case where the heater 110 is provided in the line L2 and the heater 110 is provided in the line L1 (upstream of the storage tank 130). That is, the storage tank 130 in this modification can reduce the discharge pressure of the pump P1 (a pump that supplies excess sludge to the storage tank 130) by releasing the pressure in the line L2, for example. In other words, the temperature adjustment system 100 in this modification can divide the pump pressure required to pump excess sludge to the digestion tank 60 between the pump P1 and another pump (not shown) provided downstream of the storage tank 130, for example. Therefore, the temperature adjustment system 100 in this modification can reduce the size of the pump P1 and the power consumption of the pump P1, for example.

[0100] In this case, the temperature adjustment system 100 in this modification may not have the storage tank 131 provided downstream of the storage tank 130. In this case, the pump P2 may directly supply the excess sludge stored in the storage tank 130 to the digestion tank 60.

[0101] Furthermore, in the treatment system 1000 in the first embodiment, first modified example, second modified example, third modified example, and fourth modified example, the amount of excess sludge supplied to the heater 110 and the heater 140 has been described as being adjusted, for example, by controlling the opening and closing of valves V1, V2, V3, and V4, but this is not limited to this. Specifically, in the treatment system 1000 in the first embodiment, first modified example, second modified example, third modified example, and fourth modified example, the amount of excess sludge and digested sludge supplied to the heater 110 and the heater 140 may be adjusted, for example, by controlling the rotation speed of pumps P1, P2, P3, and P4, etc. [Explanation of symbols]

[0102] 10: Primary sedimentation tank 20: Reaction tank 30: Final settling tank 40: Thickener 50: Concentrator 60: Digestion tank 100: Temperature control system 110: Heater 120: Storage tank 130: Storage tank 130a: Discharge pipe 131: Storage tank 140: heater 200: control device 201:CPU 202:Memory 203: Communication device 204: Storage medium 205: Bus 210: Program 230: Information storage area 1000: Processing system L1: Line L2: Line L3: Line L4: Line L5: Line L6: Line L7: Line P1: Pump P2: Pump P3: Pump P4: Pump T: Thermometer V1: Valve V2: Valve V3: Valve V4: Valve

Claims

1. a first tank for digesting sludge; a first pipe for supplying excess sludge to the first tank; a first heater that heats the excess sludge in the first pipe with a fluid; a second tank that stores the excess sludge before being heated by the first heater and the excess sludge that has been heated by the first heater; a second pipe for circulating the excess sludge between the first heater and the second tank; A digestion system comprising: a control device that controls at least one of the supply of excess sludge to the second piping and the supply of excess sludge to the first tank based on the temperature of the excess sludge in the second tank.

2. The first heater heats the excess sludge supplied from the second tank, the second pipe supplies the excess sludge heated in the first heater to the second tank; The digestion system described in claim 1, wherein the control device controls the supply of excess sludge from the second tank to the first heater when the temperature of the excess sludge supplied from the second piping to the second tank is below a threshold value, and further controls the supply of the excess sludge heated in the first heater to the second piping.

3. The first heater heats the excess sludge supplied from the second tank, the second pipe supplies the excess sludge heated in the first heater to the second tank; The digestion system described in claim 1, wherein the control device controls the excess sludge to be supplied from the second tank to the second piping when the temperature of the excess sludge supplied from the second piping to the second tank is below a threshold value.

4. A heating control method for a digestion system including a first tank for digesting sludge, a first pipe for supplying excess sludge to the first tank, a first heater for heating the excess sludge in the first pipe with a fluid, a second tank for storing at least one of the excess sludge before being heated by the first heater and the excess sludge heated by the first heater, and a second pipe for circulating the excess sludge between the first heater and the second tank, comprising: A heating control method that controls at least one of the supply of the excess sludge to the second piping and the supply of the excess sludge to the first tank based on the temperature of the excess sludge in the second tank.

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