Organic waste treatment system

Abstract

To provide an organic waste treatment system capable of optimizing a supply of hydrogen peroxide in an ozone method.SOLUTION: An organic waste treatment system consists of a digestion facility that anaerobically digests organic waste to produce biogas, and a solubilization facility capable of solubilizing the organic waste and supplies the solubilized waste to the digestion facility. The solubilization system consists of a solubilization tank, a circulation route that circulates the treated material in the solubilization tank and returns it to the solubilization tank, a pressurizing pump that pressurizes the treated material in the circulation route, an ozone supply part that supplies ozone to the treated material in the circulation route, a hydrogen peroxide supply part that supplies hydrogen peroxide to the treated material in the circulation route, a dissolution reaction part installed in the circulation path and promotes solubilization of the object to be treated by at least either turbulent flow or pressurization, and a control part controlling an amount of hydrogen peroxide supplied from the hydrogen peroxide supply part based on the ozone concentration and flow rate supplied from the ozone supply part.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The embodiment relates to an organic waste treatment system. [Background technology]

[0002] Anaerobic digestion has traditionally been one of the methods for treating organic waste such as sludge and industrial wastewater. In anaerobic digestion, the organic matter in the waste is broken down into smaller molecules in a digester tank and converted into biogas, which is primarily composed of methane and carbon dioxide, and is then removed from the treated liquid.

[0003] Anaerobic digestion can also be used to recover energy from waste. Biogas contains about 70% methane, a combustible gas, which can be converted into heat in a gas boiler and used to heat the digester tank, or generated in a gas generator and used at the treatment facility, reducing the amount of electricity purchased by the entire treatment facility. Selling the electricity can also generate direct profits.

[0004] Increasing the amount of biogas increases the amount of energy recovered. Solubilization is a method for increasing biogas. Solubilization breaks down solids in waste into smaller molecules and liquefies them, making it easier for the anaerobic digestion reaction to proceed and contributing to an increase in biogas. One example of a solubilization method is the ozone method. For example, in the conventional ozone method, hydrogen peroxide is added to the sludge at an amount of 100 ppm or less, reducing the amount of ozone added and increasing the amount of biogas generated. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5916971 [Patent Document 2] Patent No. 4339775 [Patent Document 3] Japanese Patent Application Publication No. 2019-25428 Summary of the Invention [Problem to be solved by the invention]

[0006] When adding hydrogen peroxide in the ozone method, if the amount of hydrogen peroxide is less than the appropriate amount, the solubilization effect will be small. On the other hand, if the amount of hydrogen peroxide exceeds the appropriate amount, not only will costs increase, but the solubilization effect will also be reduced. Furthermore, in organic waste treatment systems, the concentration of ozone supplied to the sludge and the flow rate of ozone gas often fluctuate.

[0007] However, in conventional technology, hydrogen peroxide is supplied without taking into consideration fluctuations in the concentration of ozone supplied to the sludge or the flow rate of the ozone gas, and the amount of hydrogen peroxide supplied may not be appropriate, leaving room for improvement.

[0008] Therefore, an object of the present invention is to provide an organic waste treatment system that can optimize the amount of hydrogen peroxide supplied in the ozone method. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the objectives, the organic waste treatment system of the embodiment includes a digestion facility that anaerobically digests the material to be treated, including organic matter, to produce biogas, and a solubilization facility that solubilizes the material to be treated and supplies it to the digestion facility. The solubilization equipment includes a solubilization tank that stores the material to be treated, a circulation path that circulates the material to be treated in the solubilization tank and returns it to the solubilization tank, a pressure pump that pressurizes the material to be treated in the circulation path, an ozone supply unit that supplies ozone to the material to be treated in the circulation path, a hydrogen peroxide supply unit that supplies hydrogen peroxide to the material to be treated in the circulation path, a dissolution reaction unit that is provided in the circulation path and promotes solubilization of the material to be treated by at least one of turbulence and pressurization, an ozone concentration measurement unit that measures the concentration of ozone supplied from the ozone supply unit, an ozone flow rate measurement unit that measures the flow rate of ozone supplied from the ozone supply unit, and a control unit that controls the amount of hydrogen peroxide supplied from the hydrogen peroxide supply unit based on the concentration and flow rate of ozone supplied from the ozone supply unit. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing the overall configuration of a conventional organic waste treatment system. [Figure 2] FIG. 2 is a graph showing the change over time in ozone concentration and ozone gas flow rate in a conventional organic waste treatment system. [Figure 3] FIG. 3 is a diagram showing the overall configuration of the first experimental device in the first embodiment. [Figure 4] FIG. 4 is a diagram showing the overall configuration of the second experimental device in the first embodiment. [Figure 5] FIG. 5 is a diagram showing the overall configuration of the organic waste treatment system in the first embodiment. [Figure 6] FIG. 6 is a diagram showing the overall configuration of an organic waste treatment system in the second embodiment. [Figure 7] FIG. 7 is a diagram showing the overall configuration of an organic waste treatment system according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments (first to third embodiments) of the organic waste treatment system of the present invention will be described. The following exemplary prior art, embodiments, and variations include similar components. Therefore, in the following, similar components will be given common reference numerals, and duplicated explanations will be omitted as appropriate. Parts included in the embodiments and variations can be configured by replacing them with corresponding parts in other embodiments and variations. Furthermore, the configurations, positions, etc. of parts included in the embodiments and variations are the same as those in other embodiments and variations unless otherwise specified.

[0012] (Prior Art) First, to facilitate understanding, a conventional organic waste treatment system will be described. Figure 1 shows the overall configuration of a conventional organic waste treatment system 100. The organic waste treatment system 100 comprises a digestion facility 12 and a solubilization facility 14.

[0013] The digestion facility 12 anaerobically digests organic waste containing organic matter to generate biogas containing methane, and discharges digested sludge after removing the organic matter. The digestion facility 12 has a digestion tank 22.

[0014] The digester 22 receives the solubilized sludge solubilized by the solubilization equipment 14. The digester 22 contains anaerobic microorganisms, which anaerobically digest the solubilized sludge received from the solubilization equipment 14. The digester 22 supplies biogas containing methane to the power generation equipment 90 and the like, and sends the digested sludge to the dehydration equipment 92 and the like.

[0015] The solubilization equipment 14 includes a circulation path 32, a solubilization tank 34, a pressure pump 36, a hydrogen peroxide solution tank 38, a hydrogen peroxide injection pump 40, an ozone generator 42, an ejector 44, and a dissolution reaction section 46.

[0016] The digested sludge in the solubilization tank 34 circulates through the circulation path 32, passing through the pressure pump 36, the ejector 44, and the dissolution reaction section 46 along the way, and then returning to the solubilization tank 34.

[0017] The solubilization tank 34 stores sludge (digested sludge, solubilized sludge). The solubilization tank 34 sends the solubilized sludge to the digestion tank 22.

[0018] The hydrogen peroxide injection pump 40 injects hydrogen peroxide supplied from the hydrogen peroxide solution tank 38 into the sludge pressurized by the pressure pump 36 in the circulation path 32 downstream of the ejector 44 .

[0019] The ozone generator 42 supplies ozone to the sludge flowing through the ejector 44 on the circulation path 32 .

[0020] The dissolution reaction section 46 has a nozzle 50, an inner cylinder 52, and a dissolution reaction tank 54. The nozzle 50 injects the sludge mixed with ozone and hydrogen peroxide sent from the ejector 44 into the dissolution reaction tank 54, thereby promoting the solubilization of the sludge. The dissolution reaction section 46 sends the solubilized sludge to the solubilization tank 34.

[0021] In such a conventional organic waste treatment system 100, the concentration of ozone supplied to the sludge and the flow rate of ozone gas often fluctuate. Figure 2 is a graph showing the time-dependent changes in the ozone concentration and ozone gas flow rate in the conventional organic waste treatment system 100. Even if attempts are made to keep the ozone concentration and ozone gas flow rate constant, they often fluctuate, as shown in Figure 2. However, hydrogen peroxide is supplied without taking into consideration the fluctuations in the ozone concentration and ozone gas flow rate, and the amount of hydrogen peroxide supplied may not be appropriate, leaving room for improvement.

[0022] Therefore, the following describes a technique that can optimize the supply amount of hydrogen peroxide in the ozone method.

[0023] (First embodiment) The first embodiment will be described below. First, a first experiment investigating the relationship between the amount of ozone added and the solubilization rate and the amount of biogas generated will be described with reference to Fig. 3. Next, a second experiment investigating the appropriate range of the amount of hydrogen peroxide added relative to the amount of ozone added will be described with reference to Fig. 4. Next, an organic waste treatment system 10 in the first embodiment will be described with reference to Fig. 5.

[0024] (First experiment) First, the first experiment will be described. Fig. 3 is a diagram showing the overall configuration of a first experimental apparatus 200 in the first embodiment. The first experimental apparatus 200 is installed, for example, in a laboratory. The first experimental apparatus 200 includes a circulation path 32, a solubilization tank 34, a pressure pump 36, an ozone generator 42 (ozone supply unit), an ejector 44, a dissolution reaction unit 46, and a pressure adjustment valve 71. The dissolution reaction unit 46 includes a nozzle 50, an inner cylinder 52, and a dissolution reaction tank 54.

[0025] Using the first experimental equipment 200, an experiment was conducted to solubilize sludge using only ozone addition. Sludge placed in a solubilization tank 34 is sent to a dissolution reaction section 46 by a pressure pump 36, and ozone is sucked in from an ozone generator 42 by an ejector 44 en route. The pressure fluctuations caused by the ozone suction break down sludge flocs (lumps) and turn them into ozone-mixed sludge. The ozone-mixed sludge is sprayed from a nozzle 50 inside the pressurized dissolution reaction section 46, and comes into contact with an inner tube 52 installed inside the dissolution reaction section 46, causing turbulent agitation within the dissolution reaction section 46. This causes the ozone dissolved by the microbubbles to react with the sludge, resulting in solubilization.

[0026] The sludge used was digested sludge (VS 1.5%) from a sewage treatment plant, and the amount of ozone added to the sludge was 0-150 mg / L, which corresponds to an ozone injection rate per VS of sludge of 0-0.01 mg-O3 / mg-VS.

[0027] In the first experimental apparatus 200, the gas-liquid ratio of the ozone gas flow rate and the flow rate of the pressure pump 36 could not be set to exceed 0.08, so the gas-liquid ratio was fixed and the amount of ozone added was adjusted by the treatment time. The ozone addition amount of 0 mg / L means that in the first experimental apparatus 200, oxygen was supplied in a non-discharge state with no voltage applied to the ozone generator 42 in order to obtain effects other than ozone.

[0028] After the experiment, the VSS (loss on ignition of suspended solids) of the sludge samples was analyzed, and the solubilization rate was obtained using equation (1). Solubilization rate [%] = (1 - sludge sample VSS [%] ÷ untreated sludge VSS [%]) × 100...Equation (1)

[0029] Next, a digestion test to determine the amount of gas generated was conducted as follows. Treated sludge sample and digested sludge as seed sludge were placed in a 200 mL vial in a 1:1 ratio, and the gas phase was replaced with nitrogen and sealed. The vial was placed in a thermostatic shaker at 37°C, and the amount of gas generated was measured for over 30 days. From the measured values, the amount of gas generated per sludge sample VS and the gas increase ratio relative to untreated sludge were calculated using equations (2) and (3).

[0030] Gas generation rate [L / g-VS] = Measured gas generation rate (mL) x 10 -3 ÷(sludge sample volume [mL] × VS [%] × 10 -2 )...Equation (2) Gas increase ratio [-] = amount of gas generated from treated liquid [mL] ÷ amount of gas generated from untreated sludge [mL] ...Equation (3)

[0031] [Table 1]

[0032] The experimental results are shown in Table 1. The untreated sludge in A-1 is the sludge before it was put into the first experimental equipment 200. Comparing A-1 and A-2, it was found that by passing the sludge through the first experimental equipment 200, the solubilization rate increased by 9.8 points and the gas increase ratio also increased by 0.07 points, even without supplying ozone. This is thought to be due to the effect that when the sludge is mixed with gas in the ejector 44, which is a pressure fluctuation pipe, the shear force generated by the pressure fluctuation causes the sludge solids to be crushed and broken down into smaller molecules.

[0033] Furthermore, it can be seen from A-2 to A-5 that the greater the amount of ozone supplied, the greater the solubilization of sludge and the amount of gas generated.

[0034] From the above, it was suggested that by crushing the solid matter in the sludge, injecting ozone, and dissolving the microbubbled ozone into the sludge under pressure, a high solubilization rate and an increase in biogas volume could be obtained in proportion to the amount of ozone added, at least when the ozone addition amount is 150 mg / L or less.

[0035] (Second experiment) Next, the second experiment will be described. Figure 4 is a diagram showing the overall configuration of the second experimental device 300 in the first embodiment. The second experimental device 300 is installed in, for example, a laboratory.

[0036] The second experimental apparatus 300 was the first experimental apparatus 200 shown in Figure 3, with the addition of a hydrogen peroxide tank 38 for storing 30% hydrogen peroxide and a hydrogen peroxide injection pump 40 (hydrogen peroxide supply unit). The hydrogen peroxide injection pump 40 injected the hydrogen peroxide into the sludge at a predetermined rate. The experimental results are shown in Table 2.

[0037] [Table 2]

[0038] The untreated sludge in B-1 is the sludge before being placed in the second experimental device 300. In B-2 to B-9, the amount of ozone added was 50 mg / L, and the amount of hydrogen peroxide added was in the range of 0 to 100 ppm.

[0039] The solubilization rate of B-2, which did not contain hydrogen peroxide, was 10.4%, and the gas increase ratio was 1.19. The solubilization rates of B-3 to B-9, which contained hydrogen peroxide at 10 to 100 ppm, ranged from 9.8 to 11.9%, with an average of approximately 10.6%, showing no clear differences. Meanwhile, the gas increase ratio increased up to 30 ppm, from 1.29 at 10 ppm, 1.31 at 20 ppm, and 1.33 at 30 ppm. While the gas increase ratio was higher than that of B-2 at 40 ppm, it began to decrease at 30 ppm, and from 60 ppm onwards, the gas increase ratio was similar to or lower than that of B-2.

[0040] The addition of hydrogen peroxide did not significantly affect the solubilization rate, suggesting that hydrogen peroxide does not completely oxidize and decompose the floating sludge (solids) like ozone does. However, the gas increase ratio increased up to 30 ppm, suggesting that the addition of hydrogen peroxide cleaves the cell walls of the organic matter in the sludge, leaving it floating and easily digestible. Furthermore, the maximum gas increase ratio was achieved at 30 ppm, suggesting that there is an optimum amount of hydrogen peroxide added; below this amount, the solubilization effect is insufficient, while above this amount, the solubilization effect is insufficient and the cost of hydrogen peroxide becomes excessive. Furthermore, the addition of more hydrogen peroxide than the optimum amount is thought to result in a decrease in the solubilization rate and gas increase ratio due to the hydrogen peroxide consuming a large amount of the highly oxidizing hydroxyl radicals (OH) generated by the reaction of ozone with water.

[0041] The amount of aqueous hydrogen peroxide added that results in a larger gas increase ratio than B-2 is 10 to 40 ppm, and it is thought that the optimal amount of aqueous hydrogen peroxide added is around 20 to 30 ppm, where the gas increase ratio is particularly large. From the above, it was suggested that the optimal range of aqueous hydrogen peroxide added is at least 10 to 40 ppm, and more preferably 20 to 30 ppm, for an ozone addition amount of 50 mg / L to sludge.

[0042] (Configuration and operation of organic waste treatment system) Next, the configuration and operation of the organic waste treatment system 10 of this embodiment will be described. Figure 5 is a diagram showing the overall configuration of the organic waste treatment system 10 in the first embodiment. The organic waste treatment system 10 is installed in, for example, a sewage treatment facility.

[0043] The organic waste treatment system 10 removes organic matter contained in sludge (material to be treated), which is organic waste such as sewage sludge, by generating methane and carbon dioxide through anaerobic digestion. The organic waste treatment system 10 recovers and uses the biogas, which is produced by anaerobic digestion and contains approximately 70% methane, as energy. For example, the organic waste treatment system 10 converts the methane contained in the biogas into heat in a gas boiler and uses it to heat the digester tank 22. The organic waste treatment system 10 also uses the methane contained in the biogas to generate electricity in the gas generator of the power generation facility 90, and by using the generated electricity within the organic waste treatment system 10, it is possible to reduce the amount of electricity purchased or to earn profits by selling the electricity.

[0044] The organic waste treatment system 10 includes a digestion facility 12, a solubilization facility 14, and a control device 16 (control unit).

[0045] The digestion facility 12 anaerobically digests sludge containing organic matter to generate biogas containing methane, and discharges digested sludge from which the organic matter has been removed (digested sludge). The digestion facility 12 has a digestion tank 22.

[0046] The digester 22 receives organic waste from the outside and solubilized sludge solubilized by the solubilization equipment 14. The digester 22 contains anaerobic microorganisms, which anaerobically digest the solubilized sludge supplied from the solubilization equipment 14. The anaerobic microorganisms include hydrolytic bacteria, acid-producing bacteria, and methanogens. For example, the digester 22 uses hydrolytic bacteria to decompose high molecular weight organic matter, such as carbohydrates, proteins, and lipids, contained in the organic matter of the sludge, into low molecular weight organic matter. Next, the digester 22 uses acid-producing bacteria to decompose the low molecular weight organic matter into lower fatty acids, such as acetic acid and propionic acid. Furthermore, the digester 22 uses methanogens to decompose the lower fatty acids into methane and carbon dioxide, generating biogas, and the digested sludge, from which some of the organic matter has been removed, is separated from the biogas. The digester 22 supplies biogas containing methane to a power generation facility 90 and the like, and sends digested sludge to a dehydration facility 92 and the like.

[0047] The solubilization equipment 14 solubilizes the digested sludge received from the digestion tank 22 and returns it to the digestion equipment 12. The solubilization equipment 14 includes a circulation path 32, a solubilization tank 34, a pressure pump 36, a hydrogen peroxide solution tank 38, a hydrogen peroxide injection pump 40, an ozone generator 42, an ejector 44, a dissolution reaction section 46, an ozone gas flow meter 61, and an ozone concentration meter 62.

[0048] The circulation path 32 connects the solubilization tank 34, the pressure pump 36, the ejector 44, the dissolution reaction section 46, and the solubilization tank 34. The circulation path 32 circulates the sludge in the solubilization tank 34 through the pressure pump 36, the ejector 44, and the dissolution reaction section 46 in that order, and then returns the sludge to the solubilization tank 34.

[0049] The solubilization tank 34 is connected to the digestion tank 22 and the circulation path 32. The solubilization tank 34 temporarily stores a mixture of digested sludge received from the digestion tank 22 and solubilized sludge received from the dissolution reaction section 46.

[0050] The pressure pump 36 is disposed in the circulation path 32 between the solubilization tank 34 and the ejector 44. The pressure pump 36 pressurizes the sludge in the circulation path 32. That is, the pressure pump 36 pressurizes the sludge in the solubilization tank 34, causes it to flow into the circulation path 32, and sends it to the ejector 44.

[0051] The ozone generator 42 is connected to an ejector 44 on the circulation path 32. The ozone generator 42 generates ozone, which is a gas to be mixed with the sludge. The ozone generator 42 supplies ozone as an oxidizing agent to the sludge flowing through the ejector 44 in the circulation path 32.

[0052] The ejector 44 is disposed in the circulation path 32 between the pressure pump 36 and the dissolution reaction section 46. The ejector 44 is, for example, a pressure fluctuation pipe, which is a type of pump. The ejector 44 sucks in ozone supplied from the ozone generator 42. The ejector 44 mixes the sludge pressurized by the pressure pump 36 with the ozone. The ejector 44 crushes solids in the sludge to lower molecular weights by shearing force generated by pressure fluctuations due to the supply of ozone, and also converts the ozone into microbubbles. The ejector 44 sends the sludge mixed with the microbubbled ozone to the dissolution reaction section 46.

[0053] The hydrogen peroxide tank 38 is connected to the circulation path 32 downstream of the ejector 44 via a hydrogen peroxide injection pump 40. The hydrogen peroxide tank 38 generates hydrogen peroxide to be injected (supplied) into the sludge flowing through the circulation path 32. The hydrogen peroxide tank 38 supplies liquid hydrogen peroxide containing hydrogen peroxide to the sludge as an oxidizing agent.

[0054] The hydrogen peroxide injection pump 40 is connected to the hydrogen peroxide tank 38 and is also connected to the circulation path 32 between the downstream side of the ejector 44 and the upstream side of the dissolution reaction section 46. The hydrogen peroxide injection pump 40 injects hydrogen peroxide as an oxidizing agent supplied from the hydrogen peroxide tank 38 into the sludge in the circulation path 32.

[0055] The dissolution reaction unit 46 is disposed in the circulation path 32 between the ejector 44 and the solubilization tank 34. The dissolution reaction unit 46 promotes sludge solubilization by at least one of turbulence and pressurization. The dissolution reaction unit 46 solubilizes sludge supplied with ozone and hydrogen peroxide on the circulation path 32 and sends the solubilized sludge to the solubilization tank 34. The dissolution reaction unit 46 includes a nozzle 50, an inner cylinder 52, and a dissolution reaction tank 54. The nozzle 50 is disposed in the dissolution reaction tank 54 and connected to the circulation path 32 extending from the ejector 44. The nozzle 50 injects the sludge mixed with ozone and hydrogen peroxide delivered from the ejector 44 into the dissolution reaction tank 54. The inner cylinder 52 is disposed in the dissolution reaction tank 54. The inner cylinder 52 disturbs the flow of the sludge injected into the dissolution reaction tank 54. As a result, the inner tube 52 increases the contact between the microbubbles of ozone and the solids in the sludge, destroying the cell walls of the organic matter in the ozone-mixed sludge with the oxidizing power of ozone and promoting the solubilization of organic matter such as carbohydrates and proteins inside the cells. Also, the contact between the hydrogen peroxide and the solids in the sludge increases, promoting the solubilization of the organic matter. The dissolution reaction tank 54 pressurizes the sludge inside.

[0056] The ozone gas flow meter 61 measures the flow rate of ozone (ozone gas flow rate) supplied from the ozone generator 42 and outputs the measurement result to the control device 16.

[0057] The ozone concentration meter 62 measures the concentration of ozone supplied from the ozone generator 42 and outputs the measurement result to the control device 16 .

[0058] The control device 16 is, for example, a computer having a hardware processor such as a CPU (Central Processing Unit) and storage devices such as RAM (Random Access Memory), ROM (Read Only Memory), SSD (Solid State Drive), and HDD (Hard Disk Drive). The control device 16 controls the organic waste treatment system 10 by reading a control program. Specifically, the control device 16 is connected to the hydrogen peroxide injection pump 40, the ozone gas flow meter 61, and the ozone concentration meter 62 so as to be able to send and receive electrical signals containing data.

[0059] Control device 16 receives the measurement result of the ozone flow rate from ozone gas flow meter 61, and also receives the measurement result of the ozone concentration from ozone concentration meter 62. Control device 16 controls the amount of hydrogen peroxide supplied from hydrogen peroxide injection pump 40 based on the concentration and flow rate of ozone supplied from ozone generator 42. In this case, for example, control device 16 adjusts the amount of hydrogen peroxide solution to be added to 10 to 40 ppm, more preferably 20 to 30 ppm, for an ozone addition amount of 50 mg / L to sludge.

[0060] Next, we will explain the operation related to sludge treatment in the organic waste treatment system 10. First, organic waste is sent to the digestion tank 22. Next, the sludge is digested in the digestion tank 22. Next, the digested sludge is supplied from the digestion tank 22 to the solubilization tank 34. Next, the pressure pump 36 pressurizes the sludge that has been supplied to and stored in the solubilization tank 34, and flows it into the circulation path 32.

[0061] The ejector 44 mixes the pressurized sludge with ozone supplied from the ozone generator 42 and breaks down solid organic matter in the sludge. The hydrogen peroxide injection pump 40 injects hydrogen peroxide supplied from the hydrogen peroxide solution tank 38 into the sludge in the circulation path 32. The dissolution reaction section 46 increases contact between the solid organic matter in the sludge and the ozone and hydrogen peroxide, solubilizing the organic matter, and sends the solubilized sludge to the solubilization tank 34.

[0062] The solubilization tank 34 stores the solubilized sludge, sends a portion to the digestion tank 22, and circulates the remainder within the solubilization equipment 14. The digestion tank 22 anaerobically digests the solubilized sludge to produce biogas containing methane and digested sludge, which is the solubilized sludge from which organic matter has been removed. The digestion tank 22 sends the biogas to a power generation facility 90 or the like, and sends the digested sludge to a dehydration facility 92 or the like.

[0063] In this way, in the organic waste treatment system 10, the digested sludge in the digester 22 is solubilized by repeatedly performing three batch processes: "Step 1: Extracting the digested sludge from the digester 22 to the solubilization tank 34," "Step 2: Solubilizing the digested sludge in the solubilization tank 34 in the solubilization equipment 14," and "Step 3: Returning the solubilized sludge from the solubilization tank 34 to the digester 22." In Step 2, ozone gas is supplied from the ozone generator 42, but as shown in Figure 2, the ozone concentration and ozone gas flow rate are often unstable, especially in the early stages of operation of the ozone generator 42.

[0064] In organic waste treatment system 10, the ozone concentration and ozone gas flow rate of ozone gas generated by ozone generator 42 were measured, and the amount of ozone to be added was calculated from the measured ozone concentration and ozone gas flow rate. The flow rate of hydrogen peroxide solution in hydrogen peroxide injection pump 40 was controlled so that the amount of hydrogen peroxide solution to be added was 20 to 30 ppm for an ozone addition amount of 50 mg / L to the sludge. In this case, the flow rate of hydrogen peroxide solution in hydrogen peroxide injection pump 40 was calculated using equation (4).

[0065] Q H2O2 =R H2O2 ÷R O3 ×(Q O3 ×C O3 ÷60)...Equation (4) The parameters are as follows: Q H2O2 : Hydrogen peroxide injection pump flow rate [mL / min] R H2O2 : Amount of hydrogen peroxide added: 20 [ppm] R O3 :Ozone addition amount 50 [mg / L] Q O3 :Ozone gas flow rate [Nm3 / h] C O3 :Ozone concentration [g / Nm3]

[0066] This allows the amount of hydrogen peroxide solution added to be maintained at an appropriate level relative to the amount of ozone added, and a high gas increase ratio can be maintained through the digestion of the solubilized sludge returned to the digestion tank 22, resulting in a stable increase in the amount of biogas generated.

[0067] Thus, according to the organic waste treatment system 10 of the first embodiment, even if the concentration of ozone supplied to the sludge or the ozone gas flow rate fluctuates and becomes unstable, the control device 16 controls the amount of hydrogen peroxide solution added to the sludge to be 10 to 40 ppm, more preferably 20 to 30 ppm, for an ozone addition amount of 50 mg / L. This optimizes the amount of hydrogen peroxide supplied to the sludge, and promotes sludge solubilization.

[0068] (Second embodiment) Next, a second embodiment will be described. Figure 6 is a diagram showing the overall configuration of an organic waste treatment system 10a in the second embodiment. In the first embodiment, digested sludge in the digester 22 was sent to the solubilization tank 34, and the solubilized sludge solubilized in the solubilization equipment 14 was returned to the digester 22. In the second embodiment, as shown in Figure 6, organic waste is sent to the solubilization tank 34, and the solubilized sludge solubilized in the solubilization equipment 14 is returned to the digester 22. In this second embodiment, the same effects as those in the first embodiment can be achieved.

[0069] (Third embodiment) Next, a third embodiment will be described. Fig. 7 is a diagram showing the overall configuration of an organic waste treatment system 10b in the third embodiment. In the third embodiment, as shown in Fig. 7, the digestion facility 12a includes a primary digestion tank 22a and a secondary digestion tank 22b. The primary digestion tank 22a receives organic waste, performs primary digestion, and sends the digested sludge to the solubilization tank 34. The solubilized sludge solubilized in the solubilization facility 14 is then returned to the secondary digestion tank 22b. Biogas is sent from the primary digestion tank 22a and the secondary digestion tank 22b to the power generation facility 90. Digested sludge is sent from the secondary digestion tank 22b to the dehydration facility 92. This third embodiment can also achieve the same effects as the first embodiment.

[0070] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0071] 10, 10a, 10b...organic waste treatment system, 12, 12a...digestion equipment, 14...solubilization equipment, 16...control device, 22...digestion tank, 22a...primary digestion tank, 22b...secondary digestion tank, 32...circulation path, 34...solubilization tank, 38...hydrogen peroxide water tank, 40...hydrogen peroxide injection pump, 42...ozone generator, 44...ejector, 46...dissolution reaction section, 61...ozone gas flow meter, 62...ozone concentration meter, 90...power generation equipment, 92...dehydration equipment.

Claims

1. a digestion facility that performs anaerobic digestion on a treatment target material containing organic matter to generate biogas; a solubilization facility that solubilizes the material to be treated and supplies the solubilized material to the digestion facility; Equipped with The solubilization equipment comprises: a solubilization tank for storing the material to be treated; a circulation path that circulates the material to be treated in the solubilization tank and returns it to the solubilization tank; a pressure pump that pressurizes the object to be treated in the circulation path; an ozone supply unit that supplies ozone to the object to be treated in the circulation path; a hydrogen peroxide supply unit that supplies hydrogen peroxide to the object to be treated in the circulation path; a dissolution reaction section provided in the circulation path and promoting solubilization of the object to be treated by at least one of turbulence and pressure; an ozone concentration measuring unit that measures the concentration of ozone supplied from the ozone supply unit; an ozone flow rate measuring unit that measures the flow rate of ozone supplied from the ozone supply unit; a control unit that controls the amount of hydrogen peroxide supplied from the hydrogen peroxide supply unit based on the concentration and flow rate of ozone supplied from the ozone supply unit, so that the amount of hydrogen peroxide added to the treatment object is 10 to 40 ppm for an ozone addition amount of 50 mg / L; An organic waste treatment system comprising:

2. The organic waste treatment system of claim 1, wherein the control unit controls the amount of hydrogen peroxide solution supplied from the hydrogen peroxide supply unit based on the concentration and flow rate of ozone supplied from the ozone supply unit so that the amount of hydrogen peroxide solution added is 20 to 30 ppm for an ozone addition amount of 50 mg / L to the treatment target.

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