CONTROL SYSTEM, CONTROL METHOD, AND CONTROL PROGRAM

Abstract

To provide a control system that can perform sign detection of abnormalities of a biogas plant and countermeasures before the situation becomes too late.SOLUTION: In a control system 1 including a fermentation tank 12 to which biomass feedstock is supplied and which generates a biogas by fermentation, a digestive juice retention tank 13 where a digestive juice overflown from the fermentation tank 12 is retained, a gas pack 14 for retention of a biogas generated by fermentation in the fermentation tank 12, and a controller 20, the controller 20 determines whether or not gas generation amount of a biogas is retrieved when a sign of abnormalities of the fermentation tank 12 is detected based on a predetermined determination reference, determines if a state of the digestive juice is retrieved by a third determination reference by measuring pH and / or ORP of the fermentation tank 12 when the gas generation amount of the biogas is decreased, and as a result of the determination, executes a treatment of returning a digestive juice retained in the digestive juice retention tank 13 to the fermentation tank 12 if the pH of the fermentation tank 12 is decreased and / or ORP is elevated.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control system, a control method, and a control program. [Background technology]

[0002] In recent years, biogas plants that generate renewable energy such as methane gas and electricity from biomass materials such as organic waste have been attracting attention.

[0003] Even if the concentration of methanogen metabolic inhibitors produced during the methane fermentation process, the amount of organic waste input, the temperature in the methane fermentation tank, the acid concentration, the pH, etc. are appropriately adjusted, sometimes the activity of methane fermentation in the methane fermentation tank gradually decreases, the methanogens in the methane fermentation tank become inactivated, and the generation of biogas from the methane fermentation tank stops.

[0004] In view of this, a method for restoring a methane fermentation tank in which organic waste is fermented into methane to generate biogas and in which the methanogens for methane fermentation are in an inactivated state has been proposed (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-229136 A Summary of the Invention [Problem to be solved by the invention]

[0006] As in the technology of Patent Document 1, if an abnormality is noticed too late and maintenance is performed after the system has completely stopped, recovery will take a considerable amount of time and be extremely time-consuming.

[0007] The present invention has been made based on the above problem awareness, and an object thereof is to provide a control system capable of detecting signs of abnormality in a biogas plant and taking countermeasures before it is too late.

Means for Solving the Problems

[0008] In the control system of the present embodiment, a fermentation tank in which a biomass raw material is introduced and biogas is generated by fermentation, a digestion liquid storage tank in which the digestion liquid overflowing from the fermentation tank is stored, a gas pack for storing the biogas generated by the fermentation of the fermentation tank, and a control device for controlling the fermentation tank, the digestion liquid storage tank, and the gas pack. In the control system, when the control device detects a sign of abnormality in the fermentation tank based on a predetermined determination criterion, after a certain period of time has elapsed, it determines whether or not the gas generation amount of the biogas has recovered. As a result of the determination, when the gas generation amount of the biogas has decreased, it measures the pH and / or ORP of the fermentation tank and determines whether the state of the digestion liquid has recovered based on a predetermined criterion. As a result of the determination, when the pH of the fermentation tank has decreased and / or the ORP has increased, it is characterized by executing a process of returning the digestion liquid stored in the digestion liquid storage tank to the fermentation tank.

[0009] After returning the digestion liquid stored in the digestion liquid storage tank to the fermentation tank, the control device of the present embodiment may execute a process of notifying that a pH adjuster is to be introduced into the fermentation tank when the gas generation amount of the biogas has not recovered as a result of the determination.

[0010] When the gas generation amount has recovered as a result of the determination, the control device of the present embodiment may execute a process of notifying a manual check of the gas concentration when the gas concentration of the biogas has not recovered and remains decreased as a result of the determination.

[0011] The control method of this embodiment is a control method executed by a control system including a fermenter in which a biomass raw material is introduced and which generates biogas through fermentation, a digestive liquid storage tank in which digestive liquid overflowing from the fermenter is stored, a gas pack in which the biogas generated by fermentation in the fermenter is stored, and a control device for controlling the fermenter, the digestive liquid storage tank, and the gas pack, the control method being characterized in that, when a sign of an abnormality in the fermenter is detected based on a predetermined judgment criterion, it is determined after a certain period of time whether or not the amount of gas generated from the biogas has recovered, and if the result of the judgment shows that the amount of gas generated from the biogas has decreased, the pH and / or ORP of the fermenter is measured to determine whether or not the state of the digestive liquid has recovered based on a predetermined criterion, and if the result of the judgment shows that the pH of the fermenter has decreased and / or the ORP has increased, a process of returning the digestive liquid stored in the digestive liquid storage tank to the fermenter is executed.

[0012] The control program of this embodiment is executed by a control system including a fermenter in which a biomass raw material is introduced and which generates biogas through fermentation, a digestive liquid storage tank in which digestive liquid overflowing from the fermenter is stored, a gas pack in which the biogas generated by fermentation in the fermenter is stored, and a control device for controlling the fermenter, the digestive liquid storage tank, and the gas pack. When a sign of an abnormality in the fermenter is detected based on a predetermined judgment criterion, after a certain period of time, it is determined whether or not the amount of gas generated from the biogas has recovered. If the result of the judgment shows that the amount of gas generated from the biogas has decreased, the pH and / or ORP of the fermenter is measured to determine whether or not the state of the digestive liquid has recovered based on a predetermined criterion. If the result of the judgment shows that the pH of the fermenter has decreased and / or the ORP has increased, a process of returning the digestive liquid stored in the digestive liquid storage tank to the fermenter is executed. Effect of the Invention

[0013] According to the present invention, it is possible to provide a control system that can detect signs of abnormality in a biogas plant and take action before it is too late. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a control system according to an embodiment of the present invention. [Figure 2A] 4 is a flowchart illustrating an example of a control method executed by the control system. [Figure 2B] 4 is a flowchart illustrating an example of a control method executed by the control system. [Figure 2C] 4 is a flowchart illustrating an example of a control method executed by the control system. [Diagram 3] FIG. 4 is a diagram showing an example of a display screen displayed on a display unit of the control system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An embodiment of a control system according to the present invention will be described in detail with reference to Fig. 1. Fig. 1 is a diagram showing an example of the configuration of a control system 1 according to this embodiment. The control system 1 in Fig. 1 is an example of a biogas plant that produces renewable energy such as methane gas and electricity from biomass raw materials such as organic waste. The control system 1 includes an adjustment tank 11, a fermentation tank 12, a digestive liquid storage tank 13, a gas pack 14, an air pump 15, a gas tank 16, and a control device 20.

[0016] The adjustment tank 11 stores the biomass raw material 2 pulverized by the pulverizer and mixed with water once to homogenize it so that the fermentation of methane-producing bacteria can be carried out efficiently. In this embodiment, the biomass raw material 2 to be input is, for example, organic waste. Examples of organic waste include food waste from households, agricultural residues, food waste from food factories, livestock waste, and other waste. Examples of food waste from households include vegetable peels and cuttings, fruit peels, seeds, cuttings, tea and coffee grounds, fish guts and bones, skin, meat bones and fat, leftovers of rice and bread, leftovers of dairy products and moldy foods, cooking oil, used tea bags and filters, etc. Agricultural residues include rice straw and wheat straw, pruned branches and fallen fruits of fruit trees, residues of fruits and vegetables after harvest, stems and leaves, weeds in the fields and grass during weeding, pest-eaten vegetables and fruits without pesticide use, etc. Food factory waste includes defective products during the processing process, residues during the cleaning of the production line, peels and seeds during the processing of fruits and vegetables, bran and husks of grains, cuttings and guts during the processing of fish, etc. Livestock waste includes livestock excrement, feed residues, processing residues such as feathers, bones, and skin, etc. Other waste includes pruned branches and grass of garden trees and lawns, fallen leaves, cuttings of flowers and plants, processing residues of seaweeds and seafood, processing residues of wood and paper, etc.

[0017] The adjustment tank 11 is provided with a water level measuring device 111, a pH measuring device 112, and a stirring device (stirrer) 113. The water level measuring device 111 and the pH measuring device 112 are examples of sensors. The water level measuring device 111 is a water level gauge that measures the water level of the biomass raw material 2 stored in the adjustment tank 11. The pH measuring device 112 measures the pH of the biomass raw material 2 stored in the adjustment tank 11. The measured water level and pH measurement results of the adjustment tank 11 are notified to the control device 20. The stirring device 113 is driven by a drive source (not shown) and stirs the biomass raw material 2 introduced into the adjustment tank 11. By stirring the inside of the adjustment tank 11 with the stirring device 113, the biomass raw material 2 can be homogenized. The biomass raw material 2 stored in the adjustment tank 11 is introduced into the fermentation tank 12.

[0018] The fermenter 12 performs methane fermentation on the biomass raw material 2 input through the adjustment tank 11 using microorganisms (methane-producing bacteria) to generate biogas (methane gas).

[0019] The fermenter 12 is equipped with a water level measuring device 121, a pH measuring device 122, an ORP measuring device 123, a temperature measuring device 124, a pressure measuring device 125, an input amount measuring device 126, and an agitator (agitator) 127. The water level measuring device 121, the pH measuring device 122, the ORP measuring device 123, the temperature measuring device 124, and the pressure measuring device 125 are examples of sensors.

[0020] The water level measuring device 121 is a water level gauge that measures the water level of the biomass raw material 2 stored in the fermenter 12. The water level stored in the fermenter 12 can be grasped based on the measurement results of the water level measuring device 121. The pH measuring device 122 measures the pH of the biomass raw material 2 stored in the fermenter 12. Based on the measurement results of the pH measuring device 122, the state of the methane fermentation performed by the fermenter 12, the state of the microorganisms in the fermenter 12, the acid concentration in the fermenter 12, and the like can be grasped. The acid concentration can be measured in terms of pH or hydrogen ion (H +) can be used. The ORP measuring device 123 measures the oxidation-reduction potential (ORP) of the biomass material 2 stored in the fermenter 12. Based on the measurement results of the ORP measuring device 123, the state of the methane fermentation performed by the fermenter 12, the state of the microorganisms in the fermenter 12, the reduction state in the fermenter 12, and the like can be grasped. The temperature measuring device 124 measures the temperature of the biomass material 2 stored in the fermenter 12. Based on the measurement results of the temperature measuring device 124, the state of the methane fermentation performed by the fermenter 12, the state of the microorganisms in the fermenter 12, the amount of heat in the fermenter 12, and the like can be grasped. The pressure measuring device 125 measures the pressure in the fermenter 12. Based on the measurement results of the pressure measuring device 125, the state of the methane fermentation performed by the fermenter 12, the state of the microorganisms in the fermenter 12, the state of the biomass material 2 in the fermenter 12, and the like can be grasped. Based on the measurement results of the input amount measuring device 126, the amount of the biomass material 2 input into the fermenter 12 is measured. The amount of biomass material 2 being fed into the fermenter 12 can be determined based on the side results of the feed amount measuring device 126. The measured water level, pH, ORP, temperature, pressure, and feed amount of the fermenter 12 are notified to the control device 20.

[0021] The fermenter 12 may also be equipped with a VFA (Volatile Fatty Acids) measuring device (not shown) and an ammonia nitrogen measuring device (not shown). The VFA measuring device measures the volatile fatty acids in the fermenter 12. Based on the measurement results of the VFA measuring device, it is possible to grasp the state of methane fermentation being performed in the fermenter 12, the state of the microorganisms in the fermenter 12, the nutritional state in the fermenter 12, and the like. The ammonia nitrogen measuring device measures ammonium ions (NH 4 + Based on the measurement results of the ammonia nitrogen measuring device, the state of methane fermentation being carried out in the fermenter 12, the state of the microorganisms in the fermenter 12, the nutritional state in the fermenter 12, etc. can be grasped.

[0022] The agitator 127 is driven by a drive source (not shown) and agitates the biomass material 2 introduced into the fermenter 12. By agitating the inside of the fermenter 12 with the agitator 127, the biomass material 2 can be homogenized and the fermentation of the methanogens can be efficiently carried out.

[0023] The inside of the fermenter 12 is set to a predetermined temperature, and is generally set to about 37°C in the case of mesophilic methane fermentation and about 55°C in the case of high-temperature methane fermentation. The temperature inside the fermenter 12 is controlled, for example, to about ±1°C so as not to cause temperature stress to the methanogens. Biogas such as methane generated by fermentation in the fermenter 12 is supplied to a gas pack 14. Digestive liquid overflowing from the fermenter 12 is supplied to a digestive liquid storage tank 13. The digestive liquid is a solid-liquid mixture remaining after the biomass raw material 2, which is organic waste, is decomposed and converted by a process of fermentation (anaerobic digestion) by microorganisms, and contains nutrients such as nitrogen, phosphorus, potassium, and microorganisms (methane-producing bacteria).

[0024] The digestive liquid storage tank 13 stores the digestive liquid that has overflowed from the fermenter 12. The digestive liquid storage tank 13 includes a water level measuring device 131 and an agitator (agitator) 132. The water level measuring device 131 is an example of a sensor. The water level measuring device 131 is a water level gauge that measures the water level of the digestive liquid stored in the digestive liquid storage tank 13. Based on the measurement results of the water level measuring device 131, the amount of digestive liquid that has overflowed into the digestive liquid storage tank 13 can be determined. The water level measuring device 131 also includes a water level switch. When the water level switch is ON, the water level of the digestive liquid is automatically adjusted to a predetermined water level. When the water level switch is OFF, the water level of the digestive liquid is manually adjusted by a maintenance person to a predetermined water level.

[0025] The agitator 132 is driven by a drive source (not shown) and agitates the digestive liquid that has been overflowed into the digestive liquid storage tank 13. By agitating the inside of the digestive liquid storage tank 13 with the agitator 132, the digestive liquid can be homogenized and the fermentation of methanogens can be efficiently carried out.

[0026] The gas pack 14 stores the biogas generated by methane fermentation in the fermenter 12. For example, the gas pack 14 includes a gas holder and can store the biogas in the gas holder. The gas pack 14 can also adjust the pressure of the biogas, adjust the moisture content, and remove impurities. The gas pack 14 includes a concentration measuring device 141, a generation amount measuring device 142, an emission amount measuring device 143, an emergency emission pump 144, and a gas leak detection device 145. The concentration measuring device 141, the generation amount measuring device 142, the emission amount measuring device 143, and the gas leak detection device 145 are examples of sensors.

[0027] The concentration measuring device 141 measures the concentration of biogas such as methane generated by the fermenter 12. Based on the measurement result of the concentration measuring device 141, it is possible to grasp the state of methane fermentation performed by the fermenter 12, the state of the microorganisms in the fermenter 12, the state of the biomass material 2 in the fermenter 12, and the like. The generation amount measuring device 142 measures the generation amount of biogas generated by the fermenter 12. Based on the measurement result of the generation amount measuring device 142, it is possible to grasp the state of methane fermentation performed by the fermenter 12, the state of the microorganisms in the fermenter 12, the state of the biomass material 2 in the fermenter 12, and the like. For example, the generation amount measuring device 142 can measure the generation amount of biogas generated by the fermenter 12 by measuring the relative height of a gas holder provided in the gas pack 14.

[0028] The discharge measurement device 143 measures the discharge amount of biogas that is urgently discharged from the fermenter 12. Such an emergency discharge is performed, for example, when the pressure in the fermenter 12 rises suddenly. The emergency discharge pump 144 discharges the biogas generated in the fermenter 12 under the control of the control device 20. The emergency discharge pump 144 is used when the biogas generated in the fermenter 12 is urgently discharged. Normally, the emergency discharge pump 144 is set to OFF, and is switched to ON when emergency discharge is required. The gas leak detection device 145 detects leakage of biogas from the fermenter 12 or the gas pack 14. Based on the measurement results of the gas leak detection device 145, the state of the fermenter 12, the operation of the fermenter 12, deterioration of the fermenter 12, etc. can be grasped. The measured biogas concentration, generation amount, pressure, and leakage measurement results are notified to the control device 20.

[0029] The air pump 15 compresses the biogas collected by the gas pack 14 and supplies it to the gas tank 16. The air pump 15 is equipped with a sensor that measures the amount of gas generated by the fermenter 12. The gas tank 16 stores the biogas compressed by the air pump 15. The gas tank 16 is equipped with a sensor that measures the pressure of the stored biogas.

[0030] The control device 20 includes a control unit 201, a storage unit 202, a communication unit 203, and a display unit 204. The control unit 201 is a processor (e.g., CPU: Central Processing Unit) that functions as an arithmetic processing device that controls the operation of each device constituting the control system 1. The storage unit 202 is, for example, a memory. This memory is, for example, a ROM (Read Only Memory), which is a read-only semiconductor memory in which a predetermined control program is recorded in advance, or a RAM (Random Access Memory), which is a semiconductor memory that can be written and read at any time and is used as a working memory area as necessary when the processor executes various control programs.

[0031] The communication unit 203 notifies the state of the control system 1 to a mobile terminal (not shown) held by a maintenance person through communication based on the control of the control unit 201. As the state of the control system 1, the measurement results (monitoring results) of each measuring device constituting the fermenter 12, digestive liquid storage tank 13, and gas pack 14 can be reported. As the mobile terminal, a smartphone, a tablet terminal, a notebook PC, or the like can be used. This allows the maintenance person to grasp the fermentation state of the biogas in real time. As a result, even if the amount of biogas generated decreases, a quick response can be made, and stable production can be maintained without delaying the recovery of the generated amount.

[0032] The display unit 204 notifies the maintenance person of the status of the control system 1 by video based on the control of the control unit 201. As the status of the control system 1, the measurement results (monitoring results) of each measuring device constituting the fermenter 12, digestive liquid storage tank 13, and gas pack 14 can be reported. This allows the maintenance person to grasp the fermentation status of the biogas in real time. As a result, even if the amount of biogas generated decreases, a quick response can be made, and stable production can be maintained without delaying the recovery of the generated amount.

[0033] A control method executed by the control system 1 will be described below with reference to Figures 2A, 2B, 2C, and 3. Figures 2A, 2B, and 2C are flowcharts for explaining an example of a control method executed by the control system 1. Figure 3 is a diagram showing an example of a display screen 300 displayed on the display unit 204 of the control system 1.

[0034] The controller 20 detects a sign of an abnormality in the fermenter 12 using the first criteria (control items) (step S11). The first criteria include the following four criteria (A1) to (A4).

[0035] (A1) The pH of the biomass material 2 stored in the fermentation tank 12 is continuously equal to or lower than 7.0. (A2) The amount of biogas generated in the fermenter 12 continues to decrease. (A3) The gas concentration of the biogas generated in the fermenter 12 remains below 50% for a sustained period. (A4) The oxidation-reduction potential (ORP) of the biomass material 2 stored in the fermentation tank 12 is continuously at or above −500 mV.

[0036] The judgment of the judgment criterion (A2) can be made by comparing the relative values ​​of the amount of biogas generated on the day when the same amount of biomass material 2 was input.

[0037] In addition to the above judgment criteria (A1) to (A4), the control device 20 may also add the following two judgment criteria (A5) and (A6) to the first judgment criterion to detect signs of abnormality in the fermenter 12.

[0038] (A5) The amount of volatile fatty acids (VFA) in the fermentation tank 12 fluctuates by 5000 mg / L or more due to the input biomass material 2. (A6) The amount of ammonia nitrogen in the fermenter 12 is 3500 mg / L or more in the case of high-temperature fermentation, and the amount of ammonium ions is 5000 mg / L or more in the case of mesophilic fermentation.

[0039] If none of the criteria (A1) to (A6) are met (step S11: NO), the control device 20 determines that no action is required and continues the fermentation process in the fermenter 12. If at least one of the criteria (A1) to (A6) are met (step S11: YES), the control device 20 detects that there is a sign of an abnormality in the fermenter 12 and automatically stops the dropping of the biomass raw material 2 into the adjustment tank 11 and the fermenter 12 (step S12). This allows for a measure to stop the biogas plant as soon as a sign of an abnormality is detected. As a result, even a person who is not an expert with sufficient knowledge, experience, know-how, etc. of biogas plants can stably operate the biogas plant before it is too late.

[0040] After a certain time has elapsed since the dropping of the biomass raw material 2 was stopped, the control device 20 determines whether the amount of generated biogas has recovered (step S13). The certain time is, for example, 7 to 11 hours. More preferably, the certain time is, for example, 9 hours.

[0041] When the amount of generated biogas recovers after a certain time has elapsed since the dropping of the biomass raw material 2 was stopped (step S13: recovery), the control device 20 determines the gas concentration of the generated biogas (step S14). When the gas concentration of the generated biogas recovers (step S14: recovery), the control device 20 resumes the operation of the control system 1.

[0042] If the gas concentration of the generated biogas does not recover and remains decreased (step S14: decrease), the control device 20 notifies (recommends) the maintainer to manually check the gas concentration (step S15). The notification of manual check can be sent to a mobile terminal (not shown) held by the maintainer through the communication unit 203. The notification of manual check may also be sent by displaying an image through the display unit 204 that is visually recognized by the maintainer. This makes it possible to respond quickly and maintain stable production without delaying the recovery of the generation amount, even if the gas concentration of the biogas does not recover.

[0043] The maintenance person manually detects the gas status based on the second judgment criteria (step S16). The second judgment criteria include the following three judgment criteria (B1) to (B3). The control device 20 may automatically detect the gas status based on the following three judgment criteria (B1) to (B3).

[0044] (B1) When the gas concentration of the biogas generated from the fermenter 12 is measured by a concentration measuring device 141 installed in the gas pack 14 of the control system 1 and by a handheld concentration measuring device not shown, the gas concentration is 50% or less. (B2) When gas-using equipment (generators, hot water boilers, etc.) fails to ignite due to low concentrations of gas. (B3) Even if the fermentation condition recovers and thick gas is produced, the amount of thin gas already present is too large, so the gas concentration in the holder does not increase.

[0045] The handheld concentration measuring device is a measuring device that a maintenance person uses to manually measure the gas concentration of biogas. If none of the conditions among the judgment criteria (B1) to (B3) is met (step S16: normal), the maintenance person detects that the gas condition in the gas holder provided in the gas pack 14 is normal. If it is detected that the gas condition in the gas holder is normal, the control device 20 resumes the operation of the control system 1.

[0046] When at least one of the criteria (B1) to (B3) is satisfied (step S16: abnormality), the maintenance person detects that the gas condition in the gas holder provided in the gas pack 14 is a sign of abnormality. When the maintenance person detects that the gas condition in the gas holder is a sign of abnormality, the maintenance person discharges the dilute gas in the gas holder (step S17).

[0047] The dilute gas in the gas holder can be discharged manually based on the instructions of a maintenance person. The gas in the gas holder can be discharged by driving the emergency discharge pump 144. The gas in the gas holder may also be discharged by driving the air pump 15. Alternatively, the gas may also be discharged by opening a valve (not shown) connected to the gas holder. The dilute gas in the gas holder is discharged manually based on the instructions of a maintenance person, but this is not limited to this, and the control device 20 may automatically discharge the dilute gas. In this way, if a sign of an abnormality in the biogas plant is detected, measures are taken to discharge the dilute gas immediately. As a result, even a person who is not an expert with sufficient knowledge, experience, know-how, etc. of biogas plants can stably operate the biogas plant before it is too late.

[0048] When the amount of generated biogas decreases (step S13: decrease) after a certain time has elapsed since the dropping of the biomass raw material 2 was stopped, the control device 20 detects whether the state of the digestive liquid in the fermenter 12 has recovered based on the third judgment criterion (step S18). The third judgment criterion includes the following two judgment criteria (C1) and (C2).

[0049] (C1) When the pH of fermentation tank 12 is 6.9 or less (C2) When the oxidation-reduction potential (ORP) of the fermentation tank 12 is -500 mV or higher

[0050] If the condition of the digestive liquid in the fermenter 12 has not recovered (step S18: NO), i.e., if neither of the criteria (C1) nor (C2) is satisfied, the control device 20 checks the internal pressure of each layer of the adjustment tank 11, the fermenter 12, and the digestive liquid storage tank 13 (step S19). After checking the internal pressure, the control device 20 checks the outflow of biogas from the water-sealed pot of the fermenter 12 (step S20). The outflow of biogas from the water-sealed pot of the fermenter 12 may be checked by the gas leak detection device 145.

[0051] If the outflow of biogas cannot be confirmed (step S20: NO), the control device 20 detects that the state of the fermenter 12 has recovered. If the control device 20 detects that the state of the fermenter 12 has recovered, the control device 20 resumes the operation of the control system 1.

[0052] If the outflow of biogas is confirmed (step S20: YES), the control device 20 detects that the state of the fermenter 12 has not recovered. If it detects that the state of the fermenter 12 has not recovered, the control device 20 notifies the person maintaining the control system 1 (step S21). This allows the person maintaining the control system 1 to grasp the fermentation state of the biogas in real time. As a result, even if the amount of biogas generated decreases, a delay in recovery can be prevented.

[0053] The maintenance person who has received the notification checks for failures in the measuring devices (sensors) constituting each layer of the adjustment tank 11, the fermentation tank 12, and the digestive liquid storage tank 13 (step S22). After that, the maintenance person performs a first process (step S23). The first process includes the following two processes (D1) and (D2). Therefore, the maintenance person performs at least one of the processes included in the following two processes (D1) and (D2).

[0054] (D1) A process of returning the digestive liquid (biomass raw material 2) stored in the digestive liquid storage tank 13 to the fermentation tank 12 is carried out. (D2) A process of adding seed sludge to the fermentation tank 12 is carried out.

[0055] After performing the above process (D1) or (D2), the control device 20 judges whether the fermenter 12 has recovered (step S24). If the fermenter 12 has recovered (step S24: YES), the operation of the control system 1 is resumed, and if the fermenter 12 has not recovered (step S24: NO), the maintenance person stops the operation of the control system 1.

[0056] When the condition of the digestive liquid in the fermenter 12 is recovered (step S18: YES), that is, when at least one of the criteria (C1) or (C2) is satisfied, the control device 20 performs a process of returning the digestive liquid stored in the digestive liquid storage tank 13 to the fermenter 12 (step S25). The process of returning the digestive liquid stored in the digestive liquid storage tank 13 to the fermenter 12 may be performed by a maintenance person of the control system 1. By returning the digestive liquid from the digestive liquid storage tank 13 to the fermenter 12, methanogens can be added to the fermenter 12. By adding the methanogens to the fermenter 12, fermentation in the fermenter 12 is promoted, and biogas generation can be expected. This makes it possible to detect signs of abnormality in the biogas plant and take measures before it is too late. "It is too late" refers to a state in which the methanogens are inactivated even if measures are taken. As a result, even a person who is not an expert with sufficient knowledge, experience, know-how, etc. of biogas plants can stably operate the biogas plant.

[0057] After returning the digestive liquid, the control device 20 judges whether the amount of generated biogas has recovered after a certain time has elapsed since the dropping of the biomass raw material 2 was stopped (step S26). If the amount of generated biogas has not recovered after a certain time has elapsed since the dropping of the biomass raw material 2 was stopped after returning the digestive liquid (step S26: NO), the control device 20 detects whether the state of the digestive liquid in the fermenter 12 has recovered based on a fourth judgment criterion (step S27). The fourth judgment criterion includes the following two judgment criteria (E1) and (E2).

[0058] (E1) The pH does not recover even after the digestive fluid is returned. (E2) Although there is a temporary recovery, the values ​​worsen within 2 or 3 days after restarting input.

[0059] When at least one of the criteria (E1) or (E2) is satisfied (step S27: YES), the controller 20 detects that the condition of the fermenter 12 has recovered. When the controller 20 detects that the condition of the fermenter 12 has recovered, the controller 20 resumes the operation of the control system 1.

[0060] If neither of the criteria (E1) nor (E2) is satisfied (step S27: NO), the control device 20 notifies (suggests) the maintainer of the control system 1 to add a pH adjuster to the fermenter 12 (step S28). For example, caustic soda (sodium hydroxide) can be added as the pH adjuster. The pH adjuster is not limited to caustic soda, and may be potassium hydroxide, sodium carbonate, potassium carbonate, calcium hydroxide, magnesium hydroxide, or the like. The maintainer adds the pH adjuster to the fermenter 12 based on the notification. As a result, a measure is taken to add a pH adjuster as soon as a sign of an abnormality in the biogas plant is detected. As a result, even a person who is not an expert with sufficient knowledge, experience, know-how, etc. of biogas plants can stably operate the biogas plant before it is too late.

[0061] As a result of adding the pH adjuster to the fermenter 12, the control device 20 judges whether the fermenter 12 has recovered (step S29). Whether the fermenter 12 has recovered is judged based on the above judgment criteria (A1) to (A6).

[0062] If none of the criteria (A1) to (A6) is satisfied (step S29: NO), the controller 20 determines that the condition of the fermenter 12 has recovered. If it is determined that the condition of the fermenter 12 has recovered, the controller 20 resumes the operation of the control system 1.

[0063] If any of the criteria (A1) to (A6) is not satisfied (step S29: YES), the controller 20 determines that the condition of the fermenter 12 has not recovered. If it is determined that the condition of the fermenter 12 has not recovered, the controller 20 notifies the maintainer of the control system 1 (step S30).

[0064] The maintenance person who has received the notification performs the second process (step S31). The second process includes the following two processes (F1) and (F2). The maintenance person performs at least one of the following two processes (F1) and (F2).

[0065] (F1) Adding seed sludge to the fermentation tank 12 (F2) Replacing fermentation tank 12

[0066] The above (F1) treatment is carried out when the methanogens have not been completely killed and the pH is maintained or recovering (pH: 6.5 or higher) despite being low about one day after the addition of caustic soda. This treatment is carried out when the customer strongly wishes that the control system 1 cannot be stopped for a long period of time.

[0067] The seed sludge in (F1) above is sludge that is put into the fermentation tank 12 to promote methane fermentation. Since the seed sludge is rich in microorganisms necessary for methane fermentation, it is expected to improve the balance of microorganisms in the fermentation tank 12 and increase the efficiency of methane fermentation.

[0068] The above-mentioned (F2) treatment is carried out about one day after the addition of caustic soda, except when the (F1) treatment is carried out. By carrying out the above-mentioned (F2) treatment, the fermenter 12 can be returned to its initial state and restarted, and stable operation can be restored.

[0069] After carrying out the above process (F1) or (F2), the control device 20 judges whether the fermenter 12 has recovered (step S32). If the fermenter 12 has recovered (step S32: YES), the operation of the control system 1 is resumed, and if the fermenter 12 has not recovered (step S32: NO), the maintenance person stops the operation of the control system 1.

[0070] 3, the display unit 204 of the control system 1 displays a display screen 300 showing the measurement results of each device constituting the control system 1. On the display screen 300, an adjustment tank screen 301, a fermentation tank screen 302, a digestive liquid storage tank screen 303, a gas pack screen 304, an air pump screen 305, and a gas tank screen 306 are displayed.

[0071] The adjustment tank screen 301 displays the measurement results of the adjustment tank 11. For example, the water level of the adjustment tank 11 and the pH of the adjustment tank 11 are displayed on the adjustment tank screen 301. A maintenance person can easily check the current state of the adjustment tank 11 in real time by visually checking the adjustment tank screen 301. As a result, even if the amount of biogas generation decreases, a delay in recovery can be prevented.

[0072] The fermenter screen 302 displays the measurement results of the fermenter 12. The fermenter screen 302 displays the water level of the fermenter 12, the pH of the fermenter 12, the ORP of the fermenter 12, the temperature of the fermenter 12, the pressure of the fermenter 12, and the ON / OFF state of the agitator 127. By visually checking the fermenter screen 302, a maintenance person can easily check the current state of the biomass raw material 2, digestive liquid, methanogens, and the like stored in the fermenter 12 in real time. As a result, even if the amount of biogas generated decreases, a delay in recovery can be prevented.

[0073] The digestive liquid storage tank screen 303 displays the ON / OFF state of the water level switch of the digestive liquid storage tank 13 and the ON / OFF state of the agitator 132. By visually checking the digestive liquid storage tank screen 303, a maintenance worker can easily check in real time the current state of the digestive liquid stored in the digestive liquid storage tank 13. As a result, even if the amount of biogas generation decreases, a delay in recovery can be prevented.

[0074] The gas pack screen 304 displays the gas concentration in the gas pack 14, the height of the gas holder in the gas pack 14, the amount of biogas urgently discharged from the gas pack 14, the ON / OFF state of the emergency discharge pump 144, and the presence or absence of gas leakage. By visually checking the gas pack screen 304, a maintenance person can easily check the current state of the gas recovered by the gas pack 14 in real time. As a result, even if the amount of biogas generated decreases, a delay in recovery can be prevented.

[0075] The air pump screen 305 displays the amount of gas generated by the fermenter 12. By visually checking the air pump screen 305, a maintenance person can easily check in real time the current state of the gas collected by the gas pack 14. As a result, even if the amount of biogas generated decreases, a delay in recovery can be prevented.

[0076] The gas tank screen 306 displays the pressure of the gas collected in the gas tank 16. By visually checking the gas tank screen 306, a maintenance person can easily check the current state of the gas collected in the gas tank 16 in real time. As a result, even if the amount of biogas generated decreases, a delay in recovery can be prevented.

[0077] Thus, according to this embodiment, when the condition of the digestive fluid in the fermenter 12 is restored, the control device 20 executes a process of returning the digestive fluid stored in the digestive fluid storage tank 13 to the fermenter 12. By returning the digestive fluid from the digestive fluid storage tank 13 to the fermenter 12, methanogens can be added to the fermenter 12. By adding the methanogens to the fermenter 12, fermentation in the fermenter 12 is promoted, and biogas can be expected to be generated. This makes it possible to detect signs of abnormalities in a biogas plant, which was a conventional technical problem, and to take measures before it is too late. As a result, even people who are not experts with sufficient knowledge, experience, know-how, etc. of biogas plants can stably operate the biogas plant.

[0078] The present invention is not limited to the above-described embodiment as it is, and the components can be modified and embodied in the implementation stage without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiment. For example, all the components shown in the above-described embodiment may be appropriately combined. Of course, various modifications and applications are possible without departing from the spirit of the invention. [Explanation of symbols]

[0079] 1: Control system 11:Adjustment tank 12: Fermentation tank 13: Digestive fluid storage tank 14: Gas Pack 15: Air pump 16: Gas tank 20: Control device 111: Water level measuring device 112: pH measuring device 113: Stirring device 121: Water level measuring device 122: pH measuring device 123: ORP measuring device 124: Temperature measuring device 125: Pressure measuring device 126: Input amount measuring device 127: Stirring device 131: Water level measuring device 132: Stirring device 141: Concentration measuring device 142: Generation amount measuring device 143: Discharge amount measuring device 144: Emergency discharge pump 145: Gas leakage detection device 201: Control unit 202: Memory unit 203: Communication unit 204: Display unit

Claims

1. A control system including a fermenter into which a biomass raw material is introduced and which generates a biogas by fermentation, a digestive liquid storage tank in which digestive liquid overflowing from the fermenter is stored, a gas pack in which the biogas generated by fermentation in the fermenter is stored, and a control device for controlling the fermenter, the digestive liquid storage tank, and the gas pack, The control device includes: When one or more of the first condition, the second condition, the third condition, the fourth condition, the fifth condition, or the sixth condition, which indicate a sign of an abnormality in the fermenter, are satisfied, after a certain period of time has elapsed, it is determined whether or not the amount of gas generated from the biogas has recovered; If the result of the determination is that the amount of gas generated from the biogas has decreased, the pH and / or ORP of the fermenter is measured to determine whether the condition of the digestive liquid has been restored according to a predetermined standard; If the pH of the fermenter is decreased and / or the ORP is increased as a result of the determination, the digested liquid stored in the digested liquid storage tank is returned to the fermenter. Execute the process, the first condition represents that the pH of the fermenter is continuously equal to or lower than a first predetermined value; The second condition indicates that the amount of gas generated from the biogas is continuously decreasing, The third condition indicates that the gas concentration of the biogas is continuously equal to or lower than a second predetermined value, The fourth condition indicates that the ORP of the fermenter is continuously equal to or greater than a third predetermined value, The fifth condition represents that the amount of volatile fatty acids in the fermenter fluctuates by a fourth predetermined value or more, The sixth condition represents that the amount of ammonia nitrogen in the fermenter is equal to or greater than a fifth predetermined value.

2. The control device includes: After returning the digestive liquid stored in the digestive liquid storage tank to the fermenter, it is determined whether or not the amount of gas generated from the biogas has recovered; If the result of the determination is that the amount of generated biogas is not recovered, a notification is given to introduce a pH adjuster into the fermentation tank.

2. The control system of claim 1, further comprising: a processor for executing a process.

3. The control device includes: If the result of the determination is that the amount of gas generated has recovered, it is determined whether or not the gas concentration of the biogas has recovered; If the result of the determination is that the gas concentration has not recovered and remains low, a notification is issued to request manual confirmation of the gas concentration.

3. The control system according to claim 1, further comprising: a processor for executing a process.

4. A control method implemented by a control system including a fermenter into which a biomass raw material is introduced and which generates a biogas by fermentation, a digestive liquid storage tank in which digestive liquid overflowing from the fermenter is stored, a gas pack in which the biogas generated by fermentation in the fermenter is stored, and a control device for controlling the fermenter, the digestive liquid storage tank, and the gas pack, When one or more of the first condition, the second condition, the third condition, the fourth condition, the fifth condition, or the sixth condition, which indicate a sign of an abnormality in the fermenter, are satisfied, after a certain period of time has elapsed, it is determined whether or not the amount of gas generated from the biogas has recovered; If the result of the determination is that the amount of gas generated from the biogas has decreased, the pH and / or ORP of the fermenter is measured to determine whether the condition of the digestive liquid has been restored according to a predetermined standard; If the pH of the fermenter is decreased and / or the ORP is increased as a result of the determination, the digested liquid stored in the digested liquid storage tank is returned to the fermenter. Execute the process, the first condition represents that the pH of the fermenter is continuously equal to or lower than a first predetermined value; The second condition indicates that the amount of gas generated from the biogas is continuously decreasing, The third condition indicates that the gas concentration of the biogas is continuously equal to or lower than a second predetermined value, The fourth condition indicates that the ORP of the fermenter is continuously equal to or greater than a third predetermined value, The fifth condition represents that the amount of volatile fatty acids in the fermenter fluctuates by a fourth predetermined value or more, The control method according to claim 1, wherein the sixth condition indicates that the amount of ammonia nitrogen in the fermenter is equal to or greater than a fifth predetermined value.

5. A control program executed by a control system including a fermenter into which a biomass raw material is introduced and which generates a biogas by fermentation, a digestive liquid storage tank for storing digestive liquid overflowing from the fermenter, a gas pack for storing the biogas generated by fermentation in the fermenter, and a control device for controlling the fermenter, the digestive liquid storage tank, and the gas pack, When one or more of the first condition, the second condition, the third condition, the fourth condition, the fifth condition, or the sixth condition, which indicate a sign of an abnormality in the fermenter, are satisfied, after a certain period of time has elapsed, it is determined whether or not the amount of gas generated from the biogas has recovered; If the result of the determination is that the amount of gas generated from the biogas has decreased, the pH and / or ORP of the fermenter is measured to determine whether the condition of the digestive liquid has been restored according to a predetermined standard; If the pH of the fermenter is decreased and / or the ORP is increased as a result of the determination, the digested liquid stored in the digested liquid storage tank is returned to the fermenter. Execute the process, the first condition represents that the pH of the fermenter is continuously equal to or lower than a first predetermined value; The second condition indicates that the amount of gas generated from the biogas is continuously decreasing, The third condition indicates that the gas concentration of the biogas is continuously equal to or lower than a second predetermined value, The fourth condition indicates that the ORP of the fermenter is continuously equal to or greater than a third predetermined value, The fifth condition represents that the amount of volatile fatty acids in the fermenter fluctuates by a fourth predetermined value or more, The sixth condition represents that the amount of ammonia nitrogen in the fermenter is equal to or greater than a fifth predetermined value.

Images