Biogas production system

Abstract

The invention relates to a biogas production system. A biogas production system (1) is configured so as to be able to produce biogas (G) using, as a starting material, a waste water-soluble coolant (C) recovered from a machining device for cutting or grinding. A biogas production system (1) is provided with: a plurality of storage tanks (2) configured so as to be able to classify and store a waste water-soluble coolant recovered from a processing device according to the type thereof; a concentration measurement unit (21) configured so as to be able to measure the concentration of the waste water-soluble coolant (C) in each storage tank (2); a mixing device (3) configured so as to be able to produce a coolant mixture (M) containing a plurality of waste water-soluble coolants by mixing the waste water-soluble coolants in each of the storage tanks (2) at a ratio calculated on the basis of the concentrations of the waste water-soluble coolants; and a fermentation device (4) configured so as to be able to produce biogas by fermenting the coolant-mixed liquid (M) supplied from the mixing device (3) using microorganisms.

Description

Technical Field

[0001] The present invention relates to a biogas production system. Background Art

[0002] In recent years, the impact of carbon dioxide emitted by human activities on the global environment has been recognized as a problem. From the perspective of reducing the burden on the global environment, measures toward achieving carbon neutrality are desired. For example, Patent Document 1 describes an organic waste treatment device that processes organic waste and generates methane.

[0003] In addition, when performing machining such as cutting, grinding, and lapping, water-soluble coolants are used for the purpose of reducing the friction between the object to be machined and the tool, cooling the object to be machined, cleaning the object to be machined, etc. In the past, the wastewater-soluble coolants used during machining and discharged from the processing equipment were discarded after being rendered harmless. However, if the organic matter such as mineral oil contained in the wastewater-soluble coolant can be recycled, it is useful for achieving carbon neutrality. Therefore, it is desirable to develop a technology that ferments the organic matter in the wastewater-soluble coolant and recycles it.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-115812

[0005] When fermenting organic waste to produce biogas, it's important to supply the microorganisms with organic waste in a state that facilitates fermentation in order to efficiently produce the biogas. However, the structural composition of the wastewater-soluble coolant discharged from the processing equipment varies depending on the type of mechanical processing. Furthermore, the amount of wastewater-soluble coolant discharged from the processing equipment varies daily, depending on factors such as the processing volume of the processing equipment. Therefore, when fermenting the wastewater-soluble coolant, the microorganisms often cannot cope with fluctuations in the concentration and composition of the wastewater-soluble coolant, making it difficult to stably produce biogas. Summary of the Invention

[0006] The present invention has been made in view of the above-mentioned problems, and aims to provide a biogas production system capable of stably producing biogas from wastewater-soluble coolant used for machining.

[0007] One embodiment of the present invention is a biogas production system configured to produce biogas using wastewater-soluble coolant recovered from a machining process as a raw material, comprising:

[0008] a plurality of storage tanks configured to classify and store the wastewater-soluble coolant recovered from the processing device according to its type;

[0009] a concentration measuring unit configured to measure the concentration of the wastewater-soluble coolant in each of the storage tanks;

[0010] a mixing device configured to prepare a coolant mixture containing a plurality of the wastewater-soluble coolants by mixing the wastewater-soluble coolants in the respective storage tanks at a ratio calculated based on their concentrations; and

[0011] The fermentation device is configured to generate the biogas by fermenting the coolant mixed liquid supplied from the mixing device using microorganisms.

[0012] The biogas production system is configured to classify wastewater-soluble coolants recovered from the processing unit by type and store them in multiple storage tanks. Furthermore, the biogas production system is configured to measure the concentrations of the various wastewater-soluble coolants stored in the storage tanks using a concentration measuring unit, and to mix the various wastewater-soluble coolants in a mixing unit at a ratio corresponding to their concentrations. This allows the coolant mixture, formed from a mixture of multiple types of wastewater-soluble coolants, to be adjusted to a state that is easily fermented by microorganisms within the fermentation unit. Furthermore, by fermenting the coolant mixture in the fermentation unit, biogas can be stably produced.

[0013] As described above, according to the above embodiment, it is possible to provide a biogas production system capable of stably producing biogas from wastewater-soluble coolant used for machining. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is an explanatory diagram showing a schematic configuration of a biogas production system according to the first embodiment.

[0015] Figure 2 This is an explanatory diagram showing a schematic configuration of a biogas production system including a dilution device according to a second embodiment.

[0016] Figure 3 This is an explanatory diagram showing a schematic configuration of a biogas production system according to a third embodiment, which is configured to be able to dilute a coolant mixed liquid using digestive fluid.

[0017] Figure 4 This is an explanatory diagram showing a schematic configuration of a biogas production system including a metal removal device and an inhibitor conversion device according to a fourth embodiment. DETAILED DESCRIPTION

[0018] (Implementation 1)

[0019] Reference Figure 1 The embodiment of the above-mentioned biogas production system will be described. The biogas production system 1 of this embodiment is configured to produce biogas G using the wastewater-soluble coolant C recovered from the processing device as a raw material. Figure 1As shown, the biogas production system 1 includes: a plurality of storage tanks 2 configured to classify and store wastewater-soluble coolants C recovered from processing equipment according to their types; a concentration measuring unit 21 configured to measure the concentration of the wastewater-soluble coolants C within each storage tank 2; a mixing device 3 configured to mix the wastewater-soluble coolants C within each storage tank 2 at a ratio calculated based on their concentrations to produce a coolant mixture M containing multiple wastewater-soluble coolants C; and a fermentation device 4 configured to ferment the coolant mixture M using microorganisms to produce biogas G. The structures of the various components of the biogas production system 1 are described in detail below.

[0020] Biogas production system 1 includes multiple storage tanks 2 for storing wastewater-soluble coolant C recovered from processing equipment. Storage tanks 2 are configured to be located upstream of the equipment that constitutes biogas production system 1 and are capable of supplying wastewater-soluble coolant C to equipment connected downstream of storage tanks 2. For example, storage tanks 2 in this embodiment are configured to be connected to mixing device 3 and are capable of supplying wastewater-soluble coolant C to mixing device 3.

[0021] Wastewater-soluble coolant C, used as a raw material in the biogas production system 1, is recovered from various processing equipment such as cutting, grinding, and lapping equipment. In addition to mineral oil and surfactants contained in the water-soluble coolant used for machining, the wastewater-soluble coolant C may also contain organic matter resulting from deterioration of components in the water-soluble coolant.

[0022] Wastewater-soluble coolants C can be categorized into various types based on their composition, properties, and intended use. For example, wastewater-soluble coolants C can be classified based on their compatibility with water into three types: an emulsified type in which the cutting oil components are dispersed in water; a dissolved type in which the cutting oil components are dissolved in water; and a soluble type, which is an intermediate between the emulsified and dissolved types. Furthermore, wastewater-soluble coolants C can be categorized based on the type of machine tool used. Furthermore, wastewater-soluble coolants C can be classified based on the similarity of their structural components.

[0023] Wastewater-soluble coolants C having various structures are classified by type and stored in storage tanks 2 of the biogas production system 1. The number of storage tanks 2 provided in the biogas production system 1 can be two or more and can be appropriately set based on the desired properties of the wastewater-soluble coolants. For example, the biogas production system 1 of this embodiment is configured to have two storage tanks 2 (2a, 2b), capable of storing different types of wastewater-soluble coolants C (C1, C2) in these storage tanks 2a and 2b.

[0024] The classification method for the wastewater-soluble coolant C stored in the storage tank 2 can be appropriately determined based on the type of wastewater-soluble coolant C recovered from the machine tool. For example, if the wastewater-soluble coolant C recovered from the machine tool can be classified based on the type of compatibility with water, the wastewater-soluble coolant C can be classified based on the type of compatibility with water and stored in each storage tank 2. Alternatively, if the wastewater-soluble coolant C recovered from the machine tool can be classified based on the similarity of its structural components, the wastewater-soluble coolant C can be classified based on the similarity of its structural components and stored in each storage tank 2.

[0025] Each storage tank 2 is provided with a concentration measuring unit 21 configured to measure the concentration of the wastewater-soluble coolant C within the storage tank 2. The concentration measuring unit 21 can take various forms as long as it is configured to measure the concentration of organic matter in the wastewater-soluble coolant C. For example, the concentration measuring unit 21 may be a concentration meter configured to measure the concentration of organic matter in the wastewater-soluble coolant C based on various physical properties of the wastewater-soluble coolant C, such as its refractive index, density, and electrical conductivity.

[0026] The concentration measuring unit 21 preferably includes a COD sensor configured to measure the chemical oxygen demand (COD) of the wastewater-soluble coolant C. Generally, the higher the concentration of organic matter in the wastewater-soluble coolant C, the higher the COD of the wastewater-soluble coolant C. Therefore, by measuring the COD of the wastewater-soluble coolant C, the concentration of organic matter in the wastewater-soluble coolant can be measured. Furthermore, by setting the mixing ratio of the wastewater-soluble coolant C in the mixing device 3 based on the thus-measured concentration of the wastewater-soluble coolant C, the concentration of organic matter in the coolant mixture M can be more accurately controlled. As a result, a coolant mixture M that is more easily fermented can be produced, further improving the efficiency of biogas G production.

[0027] A mixing device 3 is connected downstream of the plurality of storage tanks 2. The mixing device 3 is configured to mix the wastewater-soluble coolants C in the respective storage tanks 2 at a ratio calculated based on their concentrations to produce a coolant mixed liquid M containing the plurality of wastewater-soluble coolants C.

[0028] The mixing device 3 of this embodiment includes a mixing tank 32 configured to mix the wastewater-soluble coolant C stored in each storage tank 2, and a coolant pump 31 configured to deliver the wastewater-soluble coolant C from each storage tank 2 to the mixing tank 32. The coolant pump 31 is configured to adjust the flow rate of the wastewater-soluble coolant C from each storage tank 2 to the mixing tank 32 based on the concentration of the wastewater-soluble coolant C in each storage tank 2 measured by the concentration measuring unit 21, so that the concentration of the coolant mixed liquid M reaches a preset target concentration. The mixing tank 32 is configured to be connected to the fermentation device 4 and can supply the coolant mixed liquid M produced in the mixing tank 32 to the fermentation device 4.

[0029] Furthermore, the specific form of the mixing device 3 is not limited to that of this embodiment. For example, the mixing device 3 may not include the mixing tank 32. In this case, the wastewater-soluble coolant C delivered from the coolant pump 31 is supplied to the fermentation device 4, and the coolant mixed liquid M is prepared and fermented within the fermentation device 4. Furthermore, the mixing ratio of the wastewater-soluble coolant C in the mixing device 3 may be adjusted using various fluid devices such as a flow control valve in addition to the coolant pump 31.

[0030] In this manner, by mixing the wastewater-soluble coolants C classified in advance by type at a ratio corresponding to their concentrations, a coolant mixed liquid M in a state easily fermented by the microorganisms in the fermentation device 4 can be prepared in the mixing tank 32 .

[0031] The target concentration of the coolant mixed liquid M in the mixing device 3 of this embodiment can be appropriately set according to the type and amount of microorganisms used in the fermentation device 4. Furthermore, for example, if the upper and lower limits of the concentration at which the coolant mixed liquid M can be fermented in the fermentation device 4 are known, the target concentration of the coolant mixed liquid M can be set to a concentration between the upper and lower limits of the concentration at which the coolant mixed liquid M can be fermented.

[0032] A fermentation device 4 is connected downstream of the mixing device 3. The fermentation device 4 is configured to ferment the coolant mixed liquid M produced in the mixing device 3 using microorganisms to produce biogas G. The biogas G produced in the fermentation device 4 is collected in a biogas tank 5, which will be described later. Furthermore, the fermentation device 4 has a discharge pipe 41 for discharging the coolant mixed liquid M, i.e., the digestion liquid I, after fermentation by the microorganisms, to the outside of the biogas production system 1. The discharge pipe 41 is configured to discharge the excess digestion liquid I to the outside of the biogas production system 1 when the amount of digestion liquid I in the fermentation device 4 exceeds a predetermined threshold.

[0033] The method of bringing the coolant mixed liquid M into contact with the microorganisms in the fermentation device 4 is not particularly limited. For example, the fermentation device 4 may be configured to bring the coolant mixed liquid M into contact with the microorganisms by directly mixing the coolant mixed liquid M with microorganisms capable of fermenting the coolant mixed liquid M. Alternatively, the fermentation device 4 may be configured to bring the coolant mixed liquid M into contact with the microorganisms by mixing the coolant mixed liquid M with a composition containing microorganisms (e.g., soil or sludge).

[0034] And, as Figure 1 As shown, the fermentation device 4 may also be configured to include a microorganism carrier 42 that supports microorganisms capable of fermenting the coolant mixed liquid M, and to allow the coolant mixed liquid M to contact the microorganism carrier 42. Examples of the carrier include a porous body such as a resin sponge, a tubular body such as a plastic body formed into a tubular shape, and a porous body with a support frame in which a plastic support frame is provided around the porous body.

[0035] The fermentation device 4 may further include a fermentation promoting device for promoting the fermentation of the coolant mixed liquid M. Examples of the fermentation promoting device include a stirring device (not shown) for further improving the contact efficiency between the coolant mixed liquid M and the microorganisms, a temperature regulating device 43 (see FIG. 1 ) for regulating the temperature of the coolant mixed liquid M and increasing the activity of the microorganisms. Figure 1 ), pH adjustment device (omitted from the figure), etc.

[0036] When a temperature adjustment device 43 is provided as in the fermentation apparatus 4 of the present embodiment, the temperature adjustment device may be configured to utilize waste heat generated in the plant to adjust the temperature of the coolant mixed liquid M. In this case, the energy required to operate the biogas production system 1 can be further reduced, and the environmental load during biogas production can be further reduced.

[0037] The biogas G produced by the fermentation device 4 may be a mixture of multiple gases. The types and amounts of gases contained in the biogas G vary depending on the types of substances contained in the coolant mixed liquid M, the types of microorganisms used in the fermentation device 4, and other factors. For example, the biogas G may contain hydrocarbon gases such as methane (CH4), carbon dioxide (CO2), and hydrogen sulfide (H2S). From the perspective of resource availability, the fermentation device 4 is preferably configured to produce biogas G containing methane. To produce such biogas G, it is preferable that the microorganisms used in the fermentation device 4 include methanogens, for example.

[0038] Furthermore, it is more preferable that the microorganisms used in the fermentation device 4 include methanogens and acidogens. The coolant mixture M contains organic matter such as hydrocarbons that constitute mineral oil. It is believed that when methanogens and acidogens are brought into contact with the coolant mixture M in the fermentation device 4, the hydrocarbons and other substances in the wastewater-soluble coolant C are digested by the acidogens, producing fatty acids, hydrogen, and carbon dioxide. Furthermore, it is believed that further digestion of these products by the methanogens allows for more efficient production of methane biogas.

[0039] The fermentation device 4 of this embodiment carries methanogens on the microorganism carriers 42. Thus, the fermentation device 4 is configured to be able to produce biogas G containing methane.

[0040] The biogas production system 1 may also include a biogas tank 5 configured to store biogas. The biogas tank 5 is configured to be located at the most downstream position among the devices constituting the biogas production system 1 and is configured to store biogas G supplied from a device connected upstream of the biogas tank 5. The biogas tank 5 of the biogas production system 1 of this embodiment is configured to be connected to the fermentation device 4 and is configured to store biogas G produced in the fermentation device 4.

[0041] As described above, the biogas production system 1 of this embodiment is configured to classify the wastewater-soluble coolant C recovered from the processing equipment by type and store it in multiple storage tanks 2. Furthermore, the biogas production system 1 is configured to measure the concentrations of the various wastewater-soluble coolants C stored in the storage tanks 2 using the concentration measuring unit 21 and to mix the various wastewater-soluble coolants C in a mixing device 3 at a ratio corresponding to their concentrations. In this way, by mixing the multiple types of wastewater-soluble coolants C to form a coolant mixture M, the coolant mixture M can be adjusted to a state that facilitates fermentation by microorganisms within the fermentation device 4. Furthermore, by fermenting the coolant mixture M in the fermentation device 4, biogas G can be stably produced.

[0042] As described above, according to the above embodiment, it is possible to provide a biogas production system capable of stably producing biogas from wastewater-soluble coolant used for machining.

[0043] (Implementation Method 2)

[0044] In this embodiment, an example of a biogas production system 102 including a dilution device 6 capable of diluting the coolant mixed liquid M will be described. In the reference numerals used in the present embodiment and subsequent embodiments, unless otherwise specified, the same reference numerals as those used in the previously described embodiment denote the same structural members as those of the previously described embodiment.

[0045] like Figure 2As shown, the biogas production system 102 of this embodiment includes: a plurality of storage tanks 2; a concentration measuring unit 21 configured to measure the concentration of the wastewater-soluble coolant C in each storage tank 2; a mixing device 3 configured to mix the wastewater-soluble coolant C in each storage tank 2 to produce a coolant mixed liquid M; and a fermentation device 4 configured to ferment the coolant mixed liquid M. The structures of the storage tanks 2, concentration measuring unit 21, mixing device 3, and fermentation device 4 of the biogas production system 102 are identical to those of the biogas production system 1 of the first embodiment.

[0046] The biogas production system 102 also includes: a dilution device 6, which is configured to supply a dilution liquid D for diluting at least one liquid selected from the group consisting of a wastewater-soluble coolant C and a coolant mixed liquid M; and a second concentration measuring unit 61, which is configured to measure the concentration of the coolant mixed liquid M, and the dilution device 6 is configured to adjust the supply amount of the dilution liquid D based on the concentration of the coolant mixed liquid M.

[0047] The diluting device 6 of this embodiment includes a water pump 62 configured to deliver tap water W as the diluent D to the mixing tank 32. The water pump 62 is configured to supply the tap water W as the diluent D to the mixing tank 32 so that the concentration of the coolant mixed liquid M measured by the second concentration measuring unit 61 reaches a predetermined target concentration.

[0048] The specific form of the diluting device 6 is not limited to that of the present embodiment, and various forms can be adopted as long as the diluting device 6 can dilute the coolant mixed liquid M used for fermentation.

[0049] Although not shown in the figures, for example, the connection destination of the diluting device 6 is not limited to the mixing tank 32. The diluting device 6 can also be connected to the storage tank 2 or the fermentation device 4. More specifically, the diluting device 6 can be configured to be connected to the storage tank 2 instead of the mixing tank 32, so as to supply the diluent D into the storage tank 2. Alternatively, the diluting device 6 can be configured to be connected to both the storage tank 2 and the mixing tank 32, so as to supply the diluent D to either the storage tank 2 or the mixing tank 32. Furthermore, the diluting device 6 can be configured to be connected to the fermentation device 4, so as to supply the diluent D into the fermentation device 4.

[0050] The diluent D used in the dilution device 6 is not limited to tap water W, and may be any liquid having a lower organic matter concentration than the coolant mixed liquid M fermented in the fermentation device 4. For example, the coolant mixed liquid M, i.e., digestive fluid, which has been fermented in the fermentation device 4 and has a reduced organic matter concentration, may be used as the dilution liquid D used in the dilution device 6.

[0051] like Figure 2As shown, the second concentration measuring unit 61 of this embodiment is provided in the mixing tank 32 of the mixing device 3 and is capable of measuring the concentration of the coolant mixed liquid M within the mixing tank 32. The second concentration measuring unit 61 can take various forms as long as it is capable of measuring the concentration of the coolant mixed liquid M. For example, the second concentration measuring unit 61 can be a concentration meter capable of measuring the concentration of the coolant mixed liquid M based on various physical property values ​​of the coolant mixed liquid M, such as the refractive index, density, and electrical conductivity.

[0052] The second concentration measuring unit 61 preferably includes a COD sensor configured to measure the concentration of the coolant mixed liquid M based on the chemical oxygen demand (COD). In this case, the second concentration measuring unit 61 can measure the concentration of the coolant mixed liquid M based on the COD of the coolant mixed liquid M. The diluting device 6 can set the supply amount of the diluent D based on the thus-calculated concentration of the coolant mixed liquid M, thereby producing a coolant mixed liquid M that is more easily fermented. As a result, the production efficiency of biogas G can be further improved.

[0053] By diluting the wastewater-soluble coolant C and / or the coolant mixed solution M with the diluent D, the concentration of the coolant mixed solution M supplied to the fermentation device 4 can be more easily adjusted to a concentration suitable for fermentation.

[0054] (Implementation 3)

[0055] In this embodiment, an example of a biogas production system 103 configured to use the digestion liquid I of the coolant mixed liquid M as the diluent D will be described. Figure 3 As shown, the biogas production system 103 of this embodiment includes: a plurality of storage tanks 2; a concentration measuring unit 21 configured to measure the concentration of the wastewater-soluble coolant C in each storage tank 2; a mixing device 3 configured to mix the wastewater-soluble coolant C in each storage tank 2 to produce a coolant mixed liquid M; and a fermentation device 4 configured to ferment the coolant mixed liquid M. The structures of the storage tanks 2, concentration measuring unit 21, mixing device 3, and fermentation device 4 of the biogas production system 102 are the same as those of the biogas production system 1 of the first embodiment. Furthermore, a second concentration measuring unit 61 is provided in the mixing tank 32 of the mixing device 3, which is configured to measure the concentration of the coolant mixed liquid M. The structure of the second concentration measuring unit 61 is the same as that of the biogas production system 102 of the second embodiment.

[0056] The biogas production system 103 of this embodiment further includes a third concentration measuring unit 63 configured to measure the concentration of the digestion liquid I composed of the coolant mixed liquid M fermented in the fermentation unit 4. Furthermore, the dilution unit 603 of this embodiment is configured to use the digestion liquid I as the dilution liquid D and to adjust the supply amount of the dilution liquid D based on the concentrations of the coolant mixed liquid M and the digestion liquid I.

[0057] More specifically, the diluting device 603 includes a water pump 62 configured to supply tap water W as the diluent D to the mixing tank 32, and a digestive solution pump 64 configured to supply digestive solution I as the diluent to the mixing tank 32. The water pump 62 is configured to supply tap water W as the diluent D to the mixing tank 32 so that the concentration of the coolant mixed solution M measured by the second concentration measuring unit 61 reaches a predetermined target concentration.

[0058] The digestive liquid pump 64 is connected to both the discharge pipe 41 of the fermentation unit 4 and the mixing tank 32, and is capable of supplying at least a portion of the digestive liquid I discharged from the fermentation unit 4 to the discharge pipe 41 to the mixing tank 32 as a diluent D. Furthermore, the digestive liquid pump 64 is configured to adjust the supply amount of the digestive liquid I to the mixing tank 32 so that the concentration of the coolant mixed liquid M reaches a predetermined target concentration based on the concentration of the coolant mixed liquid M measured in the second concentration measuring unit 61 and the concentration of the digestive liquid I measured in the third concentration measuring unit 63.

[0059] The third concentration measuring unit 63 of this embodiment is disposed between the discharge pipe 41 and the digestive solution pump 64 and is capable of measuring the concentration of the digestive solution I flowing from the discharge pipe 41 into the digestive solution pump 64. The third concentration measuring unit 63 can take various forms as long as it is capable of measuring the concentration of the digestive solution I. For example, the third concentration measuring unit 63 may be a concentration meter capable of measuring the concentration of the digestive solution I based on various physical properties of the digestive solution I, such as its refractive index, density, and electrical conductivity.

[0060] The third concentration measuring unit 63 preferably includes a COD sensor configured to measure the concentration of the digestive liquid I based on its chemical oxygen demand. In this case, the third concentration measuring unit 63 can measure the concentration of the digestive liquid I based on its COD. By setting the supply rate of the diluent D based on the thus-calculated concentration of the digestive liquid I, the diluting device 6 can produce a coolant mixed liquid M that is more easily fermented. As a result, the production efficiency of the biogas G can be further improved.

[0061] The biogas production system 103 of this embodiment is configured to reuse at least a portion of the digestive liquid I as diluent D. By reusing at least a portion of the digestive liquid I as diluent D and circulating it through the biogas production system 103, the total amount of digestive liquid I discharged from the biogas production system 103 can be further reduced. This makes it easier to miniaturize the biogas production system 103. Furthermore, in this case, the amount of tap water W used as diluent D can be reduced. Consequently, the environmental impact of operating the biogas production system 103 can be further reduced.

[0062] Furthermore, the biogas production system 103 is configured to utilize both tap water W and digestive fluid I as the diluent D. Therefore, for example, if the fermentation efficiency of the coolant mixed liquid M is insufficient, such as immediately after the biogas production system 103 begins operation, the tap water W can be used to adjust the concentration of the coolant mixed liquid M, thereby rapidly increasing the fermentation efficiency of the coolant mixed liquid M. Furthermore, if the biogas production system 103 is operating stably and the fermentation efficiency of the coolant mixed liquid M is sufficiently high, the digestive fluid I can be used to adjust the concentration of the coolant mixed liquid M.

[0063] (Implementation 4)

[0064] In this embodiment, an example of a biogas production system 104 including a metal removal device 7 and an inhibitor conversion device 8 will be described. Figure 4 As shown, the biogas production system 104 of this embodiment includes: a plurality of storage tanks 2; a concentration measuring unit 21 configured to measure the concentration of the wastewater-soluble coolant C in each storage tank 2; a mixing device 3 configured to mix the wastewater-soluble coolant C in each storage tank 2 to produce a coolant mixed liquid M; and a fermentation device 4 configured to ferment the coolant mixed liquid M. The structures of the storage tanks 2, concentration measuring unit 21, mixing device 3, and fermentation device 4 of the biogas production system 104 are the same as those of the biogas production system 1 of Embodiment 1. Furthermore, a second concentration measuring unit 61 is provided in the mixing tank 32 of the mixing device 3, which is configured to measure the concentration of the coolant mixed liquid M. The structure of the second concentration measuring unit 61 is the same as that of the biogas production system 102 of Embodiment 2.

[0065] The biogas production system 104 also includes a third concentration measuring unit 63 configured to measure the concentration of the digestive fluid I, and a diluting device 604 configured to use tap water W and the digestive fluid I as a diluent D. The structure of the third concentration measuring unit 63 is the same as that of the biogas production system 103 of Embodiment 3. Furthermore, the structure of the diluting device 604 is the same as that of the biogas production system 103 of Embodiment 3, except that the diluting fluid D is supplied to the fermentation device 4 using tap water W and the digestive fluid I, thereby diluting the coolant mixed liquid M within the fermentation device 4.

[0066] The biogas production system 104 of this embodiment further includes a metal removal device 7 , an inhibitor conversion device 8 , a gas separation device 44 , and a methane tank 504 .

[0067] The metal removal device 7 is configured to be arranged upstream of the fermentation device 4, and is capable of removing metal components in the wastewater-soluble coolant C and / or the coolant mixed liquid M. Sometimes, the wastewater-soluble coolant C and the coolant mixed liquid M contain metal powder, cutting chips, etc. generated during mechanical processing as metal components. There is a concern that the above-mentioned metal components will have a negative impact on the fermentation of the coolant mixed liquid M in the fermentation device 4. In contrast, as in the biogas production system 104 of this embodiment, by arranging the metal removal device 7 upstream of the fermentation device 4, the metal components in the wastewater-soluble coolant C and / or the coolant mixed liquid M are removed, and the impact of the metal components on the fermentation of the coolant mixed liquid M can be reduced. As a result, it can be expected that the fermentation of the coolant mixed liquid M in the fermentation device 4 can be carried out more efficiently.

[0068] Specifically, the metal removal device 7 only needs to be disposed on the path of the wastewater-soluble coolant C and the coolant mixed liquid M from the storage tank 2 to the fermentation device 4. For example, the metal removal device 7 of this embodiment is configured to be disposed between the mixing tank 32 and the fermentation device 4, and is capable of removing metal components contained in the coolant mixed liquid M.

[0069] The method for removing metal components in the metal removal device 7 is not particularly limited, and an appropriate method can be adopted depending on the form and properties of the metal components contained in the wastewater-soluble coolant C and the coolant mixed liquid M. For example, the metal removal device 7 may also include a filter 71 for filtering metal components from the wastewater-soluble coolant C and the coolant mixed liquid M. In this case, the metal removal device 7 may include a single filter 71 or multiple filters 71 with different filtering performances. In addition, the filter 71 can use a well-known filter such as a wire mesh filter or a ceramic filter.

[0070] Although not shown, the metal removal device 7 may include a device for separating the metal components by gravity, such as a sedimentation tank for settling the metal components, a device for separating the metal components by centrifugal force, such as a liquid cyclone separator, or a device for separating the metal components by electromagnetic force, such as a magnetic separator. These devices may be used alone or in combination of two or more.

[0071] The inhibitor conversion device 8 is configured to be located upstream of the fermentation device 4 and is capable of converting fermentation inhibitors in the wastewater-soluble coolant C and / or the coolant mixed liquid M into other substances. Sometimes, the wastewater-soluble coolant C and the coolant mixed liquid M contain additives such as surfactants and preservatives, and there is concern that these additives may act as fermentation inhibitors, negatively impacting the fermentation of the coolant mixed liquid M in the fermentation device 4. In contrast, as in the biogas production system 104 of this embodiment, by providing the inhibitor conversion device 8 upstream of the fermentation device 4 and converting the fermentation inhibitors in the wastewater-soluble coolant C and / or the coolant mixed liquid M into other substances, the effects of the fermentation inhibitors on the fermentation of the coolant mixed liquid M can be mitigated. As a result, it is expected that the fermentation of the coolant mixed liquid M in the fermentation device 4 will be performed more efficiently.

[0072] Specifically, the inhibitor conversion device 8 only needs to be disposed on the path of the wastewater-soluble coolant C and the coolant mixed liquid M from the storage tank 2 to the fermentation device 4. For example, the inhibitor conversion device 8 of this embodiment is configured to be disposed between the metal removal device 7 and the fermentation device 4, and is capable of converting the fermentation inhibitor contained in the coolant mixed liquid M into other substances.

[0073] The method for converting fermentation inhibitors into other substances in the inhibitor conversion device 8 is not particularly limited, and an appropriate method can be adopted depending on the type of fermentation inhibitors contained in the wastewater-soluble coolant C and the coolant mixture M. For example, the inhibitor conversion device 8 can be configured to convert fermentation inhibitors into other substances through electrical methods such as electrolysis. Alternatively, the inhibitor conversion device 8 can be configured to convert fermentation inhibitors into other substances using chemical methods such as the addition of an inhibitor treatment agent that reacts with the fermentation inhibitors. Furthermore, the inhibitor conversion device 8 can be configured to convert fermentation inhibitors into other substances using physical methods such as ultrasonic irradiation. The inhibitor conversion device 8 can be configured to implement one of the above methods, or it can be configured to implement a combination of two or more methods.

[0074] When the biogas production system 104 includes a metal removal device 7 and / or an inhibitor conversion device 8, as in this embodiment, the diluting device 603 is preferably configured to supply the diluent D downstream of the metal removal device 7 and the inhibitor conversion device 8. In this case, the concentration of the coolant mixed liquid M can be adjusted to a desired concentration while avoiding an increase in the amount of liquid processed in the metal removal device 7 and the inhibitor conversion device 8. This facilitates miniaturization of the biogas production system 104.

[0075] The gas separation device 44 is connected to the fermentation device 4 and is capable of separating methane and gases other than methane from the biogas G generated in the fermentation device 4. The methane separated in the gas separation device 44 is stored in the methane tank 504.

[0076] The biogas production system 104 including the gas separation device 44 can efficiently produce methane with high availability as a resource. The methane produced in this way can be used for various purposes, such as fuel for power generation, gas material for carburizing heat treatment, and raw materials for compounds.

[0077] Although not shown, the gas separation device 44 may be configured to separate carbon dioxide from the biogas G. In this case, carbon dioxide can be reused as a resource in addition to methane.

[0078] Although specific embodiments of the biogas production system of the present invention have been described above based on Embodiments 1 to 4, the specific embodiments of the biogas production system of the present invention are not limited to the forms shown in the above embodiments, and the structure can be appropriately changed within the scope of the scope of the present invention.

[0079] For example, in Embodiment 2, an example of a biogas production system 102 is shown in which tap water W is used as the diluent D to dilute the coolant mixed liquid M. However, instead of using tap water W as the diluent D, a configuration may be employed in which digestive fluid I is used as the diluent D. In this case, for example, a digestive fluid pump may be connected between the discharge pipe 41 and the mixing tank 32, and a third concentration measuring unit may be provided between the discharge pipe 41 and the digestive fluid pump. The supply amount of the diluent D may be adjusted based on the concentration of the coolant mixed liquid M measured by the second concentration measuring unit and the concentration of the digestive fluid I measured by the third concentration measuring unit.

[0080] Furthermore, for example, while Embodiment 4 illustrates an example of a biogas production system 104 configured to use both tap water W and digestive fluid I as the dilution liquid D, a configuration may also be employed in which only either tap water W or digestive fluid I is used as the dilution liquid D. For example, when only tap water W is used as the dilution liquid D, the third concentration measuring unit 63 and the digestive fluid pump 64 can be removed from the biogas production system 104. Furthermore, when only digestive fluid I is used as the dilution liquid D, the water pump 62 can be removed from the biogas production system 104.

Claims

1. A biogas production system capable of producing biogas using wastewater-soluble coolant recovered from a machining device as a raw material, comprising: a plurality of storage tanks configured to classify and store the wastewater-soluble coolant recovered from the processing device according to its type; a concentration measuring unit configured to measure the concentration of the wastewater-soluble coolant in each of the storage tanks; a mixing device configured to prepare a coolant mixture containing a plurality of the wastewater-soluble coolants by mixing the wastewater-soluble coolants in the respective storage tanks at a ratio calculated based on their concentrations; and The fermentation device is configured to generate the biogas by fermenting the coolant mixed liquid supplied from the mixing device using microorganisms.

2. The biogas production system according to claim 1, wherein: The concentration measuring unit includes a COD sensor configured to measure the chemical oxygen demand of the wastewater-soluble coolant, and is configured to measure the concentration based on the chemical oxygen demand of the wastewater-soluble coolant.

3. The biogas production system according to claim 1 or 2, wherein: The above-mentioned biogas production system also has: a dilution device, which is configured to supply a diluent for diluting at least one liquid selected from the group consisting of the above-mentioned wastewater-soluble coolant and the above-mentioned coolant mixture; and a second concentration measuring unit, which is configured to measure the concentration of the above-mentioned coolant mixture, and the above-mentioned dilution device is configured to adjust the supply amount of the above-mentioned dilution liquid based on the concentration of the above-mentioned coolant mixture.

4. The biogas production system according to claim 3, wherein: The second concentration measuring unit includes a COD sensor configured to measure the chemical oxygen demand of the coolant mixed liquid, and is configured to measure the concentration based on the chemical oxygen demand of the coolant mixed liquid.

5. The biogas production system according to claim 3, wherein: The above-mentioned biogas production system also has a third concentration measuring unit configured to measure the concentration of the digestive fluid composed of the above-mentioned coolant mixed liquid after fermentation in the above-mentioned fermentation device, and the above-mentioned dilution device is configured to use the above-mentioned digestive fluid as the above-mentioned dilution liquid and adjust the supply amount of the above-mentioned dilution liquid based on the concentration of the above-mentioned coolant mixed liquid and the concentration of the above-mentioned digestive fluid.

6. The biogas production system according to claim 5, wherein: The third concentration measuring unit includes a COD sensor configured to measure the chemical oxygen demand of the digestive fluid, and is configured to measure the concentration based on the chemical oxygen demand of the digestive fluid.

7. The biogas production system according to claim 3, wherein: The biogas production system further includes a metal removal device that is disposed upstream of the fermentation device and is configured to remove metal components from the wastewater-soluble coolant and / or the coolant mixed liquid.

8. The biogas production system according to claim 3, wherein: The biogas production system further includes an inhibitor conversion device, which is arranged upstream of the fermentation device and is capable of converting fermentation inhibitors in the wastewater-soluble coolant and / or the coolant mixed liquid into other substances.

9. The biogas production system according to claim 8, wherein: The diluting device is configured to be capable of supplying the diluent downstream of the inhibitor conversion device.

10. The biogas production system according to claim 1 or 2, wherein: The fermentation device is configured to produce biogas containing methane.

11. The biogas production system according to claim 10, wherein: The biogas production system further includes a gas separation device configured to separate methane from the biogas generated in the fermentation device.

12. The biogas production system according to claim 11, wherein: The biogas production system further includes a methane tank configured to store the methane separated by the gas separation device.

13. The biogas production system according to claim 1 or 2, wherein: The above-mentioned machining is cutting or grinding.

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