Biogas production system

Abstract

A biogas production system (1) is configured so as to be capable of producing a biogas (G) using, as raw material, waste water-soluble coolants (C) recovered from a machining device which performs cutting or grinding. The biogas production system (1) comprises: a plurality of storage tanks (2) configured so as to be capable of respectively storing the waste water-soluble coolants (C) recovered from the machining device by sorting the coolants by type; concentration measuring units (21) configured so as to be capable of respectively measuring the concentration of the waste water-soluble coolants (C) in the storage tanks (2); a mixing device (3) configured so as to be capable of preparing a coolant mixture (M) containing the plurality of waste water-soluble coolants (C) by mixing the waste water-soluble coolants (C) in the storage tanks (2) at ratios calculated on the basis of the concentration thereof; and a fermentation device (4) configured so as to be capable of producing the biogas (G) by using microorganisms to ferment the coolant mixture (M) supplied from the mixing device (3).

Description

Biogas Production System

[0001] The present disclosure relates to a biogas production system.

[0002] In recent years, the impact of carbon dioxide emissions from human activities on the global environment has become a concern, and efforts to achieve carbon neutrality are desired from the perspective of reducing the burden on the global environment. For example, Patent Document 1 describes an organic waste treatment device that treats organic waste to produce methane.

[0003] Furthermore, water-soluble coolants are used during machining processes such as cutting, grinding, and polishing to reduce friction between the workpiece and the tool, and to cool and clean the workpiece. Conventionally, waste water-soluble coolants used during machining and discharged from the processing equipment are disposed of after being rendered harmless. However, if the organic matter contained in waste water-soluble coolants, such as mineral oil, could be recycled, this would be useful for achieving carbon neutrality. Therefore, there is a need for the development of technology to ferment and recycle the organic matter in waste water-soluble coolants.

[0004] JP 2012-115812 A

[0005] When producing biogas by fermenting organic waste, it is important to supply microorganisms with organic waste in a state that is easy to ferment in order to efficiently produce biogas. However, the components of waste water-soluble coolant discharged from processing equipment vary depending on the type of machining. Furthermore, the amount of waste water-soluble coolant discharged from processing equipment also changes daily depending on factors such as the amount of processing performed on the equipment. Therefore, when attempting to ferment waste water-soluble coolant, microorganisms may not be able to adapt to fluctuations in the concentration and components of the waste water-soluble coolant, making it difficult to consistently produce biogas.

[0006] The present disclosure has been made in consideration of such problems, and aims to provide a biogas production system that can stably produce biogas from waste water-soluble coolant used in machining.

[0007] One aspect of the present disclosure is a biogas production system configured to be capable of producing biogas using waste water-soluble coolant recovered from processing equipment that performs mechanical processing as a raw material, the biogas production system having: a plurality of storage tanks configured to be able to separate and store the waste water-soluble coolant recovered from the processing equipment by type; a concentration measurement unit configured to be able to measure the concentration of the waste water-soluble coolant in each of the storage tanks; a mixing device configured to be able to prepare a coolant mixture containing a plurality of the waste water-soluble coolants by mixing the waste water-soluble coolants in each of the storage tanks in a ratio calculated based on the concentrations; and a fermentation device configured to be able to generate the biogas by fermenting the coolant mixture supplied from the mixing device using microorganisms.

[0008] The biogas production system is configured to separate and store waste water-soluble coolant recovered from processing equipment in multiple storage tanks. The biogas production system is also configured to measure the concentrations of various types of waste water-soluble coolant stored in the storage tanks using a concentration measuring unit, and to mix the various types of waste water-soluble coolant in a mixing device in a ratio corresponding to these concentrations. By mixing multiple types of waste water-soluble coolant to form a coolant mixture in this way, the coolant mixture can be adjusted to a state that is easy for microorganisms in the fermentation device to ferment. Then, by fermenting this coolant mixture in the fermentation device, biogas can be generated stably.

[0009] As described above, according to the above-described aspect, a biogas production system can be provided that can stably produce biogas from waste water-soluble coolant used in machining.

[0010] Fig. 1 is an explanatory diagram showing a schematic configuration of a biogas production system in Embodiment 1. Fig. 2 is an explanatory diagram showing a schematic configuration of a biogas production system equipped with a dilution device in Embodiment 2. Fig. 3 is an explanatory diagram showing a schematic configuration of a biogas production system configured to be able to dilute a coolant mixture using digested liquid in Embodiment 3. Fig. 4 is an explanatory diagram showing a schematic configuration of a biogas production system equipped with a metal removal device and an inhibitor conversion device in Embodiment 4.

[0011] (Embodiment 1) An embodiment of the biogas production system will be described with reference to FIG. 1 . The biogas production system 1 of this embodiment is configured to produce biogas G using waste water-soluble coolant C recovered from a processing device as a raw material. As shown in FIG. 1 , the biogas production system 1 includes a plurality of storage tanks 2 configured to separate and store the waste water-soluble coolant C recovered from the processing device by type; a concentration measurement unit 21 configured to measure the concentration of the waste water-soluble coolant C in each storage tank 2; a mixer 3 configured to prepare a coolant mixture M containing the plurality of waste water-soluble coolants C by mixing the waste water-soluble coolants C in each storage tank 2 at a ratio calculated based on the concentrations; and a fermenter 4 configured to produce biogas G by fermenting the coolant mixture M using microorganisms. The configuration of each component of the biogas production system 1 will be described in detail below.

[0012] The biogas production system 1 has a plurality of storage tanks 2 for storing the waste water-soluble coolant C recovered from the processing equipment. The storage tank 2 is provided at the most upstream position among the devices constituting the biogas production system 1, and is configured to be able to supply the waste water-soluble coolant C to devices connected downstream of the storage tank 2. For example, in this embodiment, the storage tank 2 is connected to a mixer 3, and is configured to be able to supply the waste water-soluble coolant C to the mixer 3.

[0013] The waste water-soluble coolant C used as a raw material in the biogas production system 1 is collected from various processing equipment such as cutting equipment, grinding equipment, and polishing equipment. The waste water-soluble coolant C may contain mineral oil and surfactants contained in water-soluble coolants for machining, as well as organic matter resulting from altered components of the water-soluble coolant.

[0014] Waste water-soluble coolant C can be classified into various types depending on its composition, properties, applications, etc. For example, waste water-soluble coolant C can be classified into three types depending on its compatibility with water: emulsion type in which cutting oil components are dispersed in water, solution type in which cutting oil components are dissolved in water, and soluble type, which is an intermediate form between the emulsion type and the solution type. Waste water-soluble coolant C can also be classified by the type of machine tool used. Furthermore, waste water-soluble coolant C can also be classified by the similarity of its constituent components.

[0015] The water-soluble waste coolant C having various compositions as described above is separated by type and stored in the storage tanks 2 of the biogas production system 1. The number of storage tanks 2 provided in the biogas production system 1 may be two or more, and can be set appropriately depending on the desired manner of separating the water-soluble waste coolant. For example, the biogas production system 1 of this embodiment has two storage tanks 2 (2a, 2b), and is configured to be able to store different types of water-soluble waste coolant C (C1, C2) in these storage tanks 2a, 2b.

[0016] The method of separating the waste water-soluble coolant C stored in the storage tanks 2 may be set appropriately depending on the type of waste water-soluble coolant C recovered from the machine tool. For example, if the waste water-soluble coolant C recovered from the machine tool can be separated into types based on its compatibility with water as described above, the waste water-soluble coolant C can be separated into types based on its compatibility with water and stored in each storage tank 2. Furthermore, if the waste water-soluble coolant C recovered from the machine tool can be separated into types based on the similarity of its constituent components, the waste water-soluble coolant C can be separated into types based on the similarity of the constituent components and stored in each storage tank 2.

[0017] Each storage tank 2 is provided with a concentration measuring unit 21 configured to be able to measure the concentration of the waste water-soluble coolant C in the storage tank 2. The concentration measuring unit 21 can take various forms as long as it is configured to be able to measure the concentration of organic matter in the waste water-soluble coolant C. For example, the concentration measuring unit 21 may be a concentration meter configured to be able to measure the concentration of organic matter in the waste water-soluble coolant C based on various physical property values ​​of the waste water-soluble coolant C, such as the refractive index, density, and conductivity.

[0018] The concentration measurement unit 21 preferably includes a COD sensor configured to measure the chemical oxygen demand (i.e., COD) of the waste water-soluble coolant C. The COD of the waste water-soluble coolant C typically increases with the concentration of organic matter in the waste water-soluble coolant C. Therefore, by measuring the COD of the waste water-soluble coolant C, the concentration of organic matter in the waste water-soluble coolant can be measured. By setting the mixing ratio of the waste water-soluble coolant C in the mixer 3 based on the concentration of the waste water-soluble coolant C measured in this manner, 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 prepared, thereby further improving the efficiency of biogas G production.

[0019] A mixer 3 is connected downstream of the multiple storage tanks 2. The mixer 3 is configured to mix the waste water-soluble coolant C in each storage tank 2 at a ratio calculated based on the concentration of the waste water-soluble coolant C, thereby preparing a coolant mixture M containing multiple waste water-soluble coolants C.

[0020] The mixing device 3 of this embodiment includes a mixing tank 32 configured to be able to mix the waste water-soluble coolant C stored in each storage tank 2, and a coolant pump 31 that pumps the waste water-soluble coolant C from each storage tank 2 to the mixing tank 32. The coolant pump 31 is configured to be able to adjust the flow rate of the waste water-soluble coolant C from each storage tank 2 to the mixing tank 32 based on the concentration of the waste water-soluble coolant C in each storage tank 2 measured by the concentration measuring unit 21, so that the concentration of the coolant mixture M becomes a predetermined target concentration. The mixing tank 32 is connected to the fermentation device 4, and is configured to be able to supply the coolant mixture M prepared in the mixing tank 32 to the fermentation device 4.

[0021] The specific configuration of the mixer 3 is not limited to this embodiment. For example, the mixer 3 does not need to have the mixing tank 32. In this case, the water-soluble waste coolant C delivered from the coolant pump 31 may be supplied to the fermenter 4, and the coolant mixture M may be prepared and fermented in the fermenter 4. In addition to the coolant pump 31, various fluid devices such as a flow control valve may be used to adjust the mixing ratio of the water-soluble waste coolant C in the mixer 3.

[0022] In this way, by mixing the waste water-soluble coolant C, which has been separated into types in advance, in a ratio according to its concentration, a coolant mixture M can be prepared in the mixing tank 32 in a state that is easy for the microorganisms in the fermentation device 4 to ferment.

[0023] The target concentration of the coolant mixture M in the mixing device 3 of this embodiment may be set as appropriate depending on 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 mixture M can be fermented in the fermentation device 4 are known, the target concentration of the coolant mixture M may be set to a concentration between the upper and lower limits of the concentration at which the coolant mixture M can be fermented.

[0024] A fermentation device 4 is connected downstream of the mixer 3. The fermentation device 4 is configured to ferment the coolant mixed liquid M prepared in the mixer 3 with microorganisms to generate biogas G. The biogas G generated in the fermentation device 4 is collected in a biogas tank 5, which will be described later. The fermentation device 4 also has a drain pipe 41 that discharges digested liquid I, which is the coolant mixed liquid M after fermentation by the microorganisms, to the outside of the biogas production system 1. The drain pipe 41 is configured to discharge excess digested liquid I to the outside of the biogas production system 1 when the amount of digested liquid I in the fermentation device 4 exceeds a predetermined threshold.

[0025] There are no particular limitations on the manner in which the coolant mixture M is brought into contact with the microorganisms in the fermentation apparatus 4. For example, the fermentation apparatus 4 may be configured to bring the coolant mixture M into contact with the microorganisms by directly mixing the coolant mixture M with the microorganisms capable of fermenting the coolant mixture M. Alternatively, the fermentation apparatus 4 may be configured to bring the coolant mixture M into contact with the microorganisms by mixing the coolant mixture M with a composition containing the microorganisms (e.g., soil or sludge).

[0026] 1, the fermentation apparatus 4 may have a microorganism carrier 42 in which microorganisms capable of fermenting the coolant mixture M are supported, and may be configured to allow contact between the coolant mixture M and the microorganism carrier 42. As the carrier, for example, a porous body such as a resin sponge, a cylindrical body such as a plastic formed into a cylindrical shape, or a porous body with a support frame in which a plastic support frame is provided around the porous body can be used.

[0027] The fermentation apparatus 4 may further include a fermentation promoter for promoting fermentation of the coolant mixture M. Examples of the fermentation promoter include a stirrer (not shown) for further improving the contact efficiency between the coolant mixture M and the microorganisms, a temperature regulator 43 (see FIG. 1 ) for adjusting the temperature of the coolant mixture M to increase the activity of the microorganisms, and a pH regulator (not shown).

[0028] When the temperature adjustment device 43 is provided as in the fermentation device 4 of this embodiment, the temperature adjustment device may be configured to be able to adjust the temperature of the coolant mixture M by utilizing waste heat generated in a factory, for example. In this case, the energy required to operate the biogas production system 1 can be further reduced, and the environmental load when producing biogas can be further reduced.

[0029] The biogas G generated from the fermentation device 4 may be a mixture of multiple types of gases. The types and amounts of gases contained in the biogas G vary depending on the types of substances contained in the coolant mixture M and the types of microorganisms used in the fermentation device 4. For example, the biogas G contains methane (CH ４ ) and carbon dioxide (CO ２ ), hydrogen sulfide (H ２ From the viewpoint of usefulness as a resource, the fermentation device 4 is preferably configured to be capable of generating biogas G containing methane. In order to generate such biogas G, it is preferable that the microorganisms used in the fermentation device 4 include, for example, methanogens.

[0030] It is more preferable that the microorganisms used in the fermentation device 4 include methanogens and acid-producing bacteria. The coolant mixture M contains organic matter such as hydrocarbons that make up mineral oil. When the methanogens and acid-producing bacteria are brought into contact with the coolant mixture M in the fermentation device 4, it is believed that the hydrocarbons and other substances in the waste water-soluble coolant C are digested by the acid-producing bacteria, producing fatty acids, hydrogen, and carbon dioxide. It is believed that these products are then further digested by the methanogens, making it possible to more efficiently generate biogas containing methane.

[0031] Methane bacteria are carried on the microorganism carriers 42 in the fermentation device 4 of this embodiment. As a result, the fermentation device 4 is configured to be able to generate biogas G containing methane.

[0032] The biogas production system 1 may have a biogas tank 5 configured to be able to store biogas. The biogas tank 5 is provided at the most downstream position among the devices constituting the biogas production system 1, and is configured to be able to store biogas G supplied from devices connected upstream of the biogas tank 5. The biogas tank 5 in the biogas production system 1 of this embodiment is connected to the fermentation device 4, and is configured to be able to store the biogas G produced in the fermentation device 4.

[0033] As described above, the biogas production system 1 of this embodiment is configured to be able to separate and store the waste water-soluble coolant C recovered from the processing equipment in multiple storage tanks 2 according to its type. The biogas production system 1 is also configured to measure the concentrations of the various types of waste water-soluble coolant C stored in the storage tanks 2 using the concentration measuring unit 21, and to mix the various types of waste water-soluble coolant C in the mixer 3 in a ratio corresponding to the concentrations. By mixing multiple types of waste water-soluble coolant C to form a coolant mixture M in this way, the coolant mixture M can be adjusted to a state that is easy for the microorganisms in the fermenter 4 to ferment. Then, by fermenting the coolant mixture M in the fermenter 4, biogas G can be stably generated.

[0034] As described above, according to the above-described aspect, a biogas production system can be provided that can stably produce biogas from waste water-soluble coolant used in machining.

[0035] (Embodiment 2) In this embodiment, an example of a biogas production system 102 having a dilution device 6 configured to be able to dilute the coolant mixture M will be described. Note that, among the symbols used in this embodiment and subsequent embodiments, the same symbols as those used in the previous embodiments represent the same components as those in the previous embodiments unless otherwise specified.

[0036] 2 , the biogas production system 102 of this embodiment includes a plurality of storage tanks 2, a concentration measurement unit 21 configured to be able to measure the concentration of the waste water-soluble coolant C in each storage tank 2, a mixer 3 configured to be able to mix the waste water-soluble coolant C in each storage tank 2 to prepare a coolant mixture M, and a fermenter 4 configured to be able to ferment the coolant mixture M. The configurations of the storage tanks 2, the concentration measurement unit 21, the mixer 3, and the fermenter 4 in the biogas production system 102 are the same as the configurations of the respective units in the biogas production system 1 of the first embodiment.

[0037] The biogas production system 102 further includes a dilution device 6 configured to be capable of supplying a diluting liquid D for diluting at least one liquid selected from the group consisting of waste water-soluble coolant C and coolant mixed liquid M, and a second concentration measuring unit 61 configured to be capable of measuring the concentration of the coolant mixed liquid M, and the dilution device 6 is configured to be capable of adjusting the supply amount of diluting liquid D based on the concentration of the coolant mixed liquid M.

[0038] The dilution device 6 of this embodiment has a water pump 62 configured to be able to deliver tap water W as the dilution liquid D to the mixing tank 32. The water pump 62 is configured to be able to supply tap water W as the dilution liquid D into the mixing tank 32 so that the concentration of the coolant mixture M measured by the second concentration measuring unit 61 becomes a predetermined target concentration.

[0039] The specific form of the dilution device 6 is not limited to this embodiment, and various forms are possible as long as it is configured to be able to dilute the coolant mixture M used for fermentation.

[0040] Although not shown in the figure, for example, the connection destination of the dilution device 6 is not limited to the mixing tank 32, and the dilution device 6 can also be connected to the storage tank 2 or the fermentation device 4. More specifically, the dilution device 6 may be connected to the storage tank 2 instead of the mixing tank 32 and configured to be able to supply the diluent into the storage tank 2. The dilution device 6 may also be connected to both the storage tank 2 and the mixing tank 32 and configured to be able to supply the diluent D to any of the storage tank 2 and the mixing tank 32. Furthermore, the dilution device 6 may also be connected to the fermentation device 4 and configured to be able to supply the diluent D into the fermentation device 4.

[0041] Furthermore, the diluting liquid D used in the diluting device 6 is not limited to tap water W, but may be any liquid having a lower concentration of organic matter than the coolant mixed liquid M fermented in the fermenting device 4. For example, the diluting liquid D used in the diluting device 6 may be digested liquid, which is the coolant mixed liquid M after it has been fermented in the fermenting device 4 and the organic matter concentration has been reduced.

[0042] 2 , the second concentration measuring unit 61 of this embodiment is provided in the mixing tank 32 of the mixing device 3 and is configured to be able to measure the concentration of the coolant mixture M in the mixing tank 32. The second concentration measuring unit 61 can take various forms as long as it is configured to be able to measure the concentration of the coolant mixture M. For example, the second concentration measuring unit 61 may be a concentration meter configured to be able to measure the concentration of the coolant mixture M based on various physical property values ​​of the coolant mixture M, such as the refractive index, density, and conductivity.

[0043] The second concentration measuring unit 61 preferably has a COD sensor configured to be able to measure the concentration based on the chemical oxygen demand of the coolant mixture M. In this case, the second concentration measuring unit 61 can measure the concentration of the coolant mixture M based on the COD of the coolant mixture M. The dilution device 6 can prepare a coolant mixture M that is more easily fermented by setting the supply amount of diluent D based on the concentration of the coolant mixture M determined in this manner. As a result, the production efficiency of the biogas G can be further improved.

[0044] In this way, by diluting the water-soluble waste coolant C and / or the coolant mixture M with the diluent D, the concentration of the coolant mixture M supplied to the fermentation device 4 can be more easily adjusted to a concentration suitable for fermentation. This allows for more stable production of biogas G.

[0045] Third Embodiment In this embodiment, an example of a biogas production system 103 configured to be able to use the digested liquid I of the coolant mixture M as the diluent D will be described. As shown in FIG. 3 , the biogas production system 103 of this embodiment includes a plurality of storage tanks 2, a concentration measurement unit 21 configured to measure the concentration of the waste water-soluble coolant C in each storage tank 2, a mixer 3 configured to mix the waste water-soluble coolant C in each storage tank 2 to prepare the coolant mixture M, and a fermenter 4 configured to ferment the coolant mixture M. The configurations of the storage tanks 2, the concentration measurement unit 21, the mixer 3, and the fermenter 4 in the biogas production system 102 are the same as those of the biogas production system 1 of the first embodiment. Furthermore, the mixing tank 32 of the mixer 3 is provided with a second concentration measurement unit 61 configured to be able to measure the concentration of the coolant mixture M. The configuration of the second concentration measurement unit 61 is the same as that of the biogas production system 102 of the second embodiment.

[0046] The biogas production system 103 of this embodiment further includes a third concentration measurement unit 63 configured to be able to measure the concentration of the digested liquid I made of the coolant mixed liquid M fermented in the fermentation device 4. The dilution device 603 of this embodiment uses the digested liquid I as a diluent D and is configured to be able to adjust the supply amount of the diluent D based on the concentrations of the coolant mixed liquid M and the digested liquid I.

[0047] More specifically, the dilution device 603 has a water pump 62 configured to be able to supply tap water W as the diluent D to the mixing tank 32, and a digestive fluid pump 64 configured to be able to supply digestive fluid I as the diluent to the mixing tank 32. The water pump 62 is configured to be able to supply tap water W as the diluent D into the mixing tank 32 so that the concentration of the coolant mixture M measured by the second concentration measuring unit 61 becomes a predetermined target concentration.

[0048] The digestive fluid pump 64 is connected to both the drain pipe 41 of the fermentation apparatus 4 and the mixing tank 32, and is configured to supply at least a portion of the digestive fluid I discharged from the fermentation apparatus 4 to the drain pipe 41 to the mixing tank 32 as a dilution fluid D. The digestive fluid pump 64 is also configured to adjust the amount of digestive fluid I supplied to the mixing tank 32 based on the concentration of the coolant mixture M measured by the second concentration measuring unit 61 and the concentration of the digestive fluid I measured by the third concentration measuring unit 63, so that the concentration of the coolant mixture M becomes a predetermined target concentration.

[0049] The third concentration measuring unit 63 in this embodiment is provided between the drain pipe 41 and the digestive fluid pump 64, and is configured to be able to measure the concentration of the digestive fluid I flowing from the drain pipe 41 into the digestive fluid pump 64. The third concentration measuring unit 63 can take various forms as long as it is configured to be able to measure the concentration of the digestive fluid I. For example, the third concentration measuring unit 63 may be a concentration meter configured to be able to measure the concentration of the digestive fluid I based on various physical property values ​​of the digestive fluid I, such as the refractive index, density, and conductivity.

[0050] The third concentration measuring unit 63 preferably has a COD sensor configured to be able to measure the concentration based on the chemical oxygen demand of the digested liquid I. In this case, the third concentration measuring unit 63 can measure the concentration of the digested liquid I based on the COD of the digested liquid I. The dilution device 6 sets the supply amount of the diluent D based on the concentration of the digested liquid I determined in this manner, thereby making it possible to prepare a coolant mixed liquid M that is more easily fermented. As a result, the production efficiency of the biogas G can be further improved.

[0051] The biogas production system 103 of this embodiment is configured so that at least a portion of the digested liquid I can be used as the diluent D. By reusing at least a portion of the digested liquid I as the diluent D and circulating it through the biogas production system 103 in this way, the total amount of digested liquid I discharged from the biogas production system 103 can be further reduced. This makes it easier to make the biogas production system 103 more compact. Furthermore, in this case, the amount of tap water W used as the diluent D can also be reduced. This makes it possible to further reduce the environmental impact caused by the operation of the biogas production system 103.

[0052] The biogas production system 103 is also configured to be able to use both tap water W and digested liquid I as the diluent D. Therefore, for example, when the fermentation efficiency of the coolant mixture M is not sufficiently high immediately after the biogas production system 103 begins operation, the tap water W can be used to adjust the concentration of the coolant mixture M, thereby enabling the fermentation efficiency of the coolant mixture M to be quickly increased. Furthermore, when the biogas production system 103 is in steady operation and the fermentation efficiency of the coolant mixture M is sufficiently high, the digested liquid I can be used to adjust the concentration of the coolant mixture M.

[0053] (Embodiment 4) 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. As shown in FIG. 4 , the biogas production system 104 of this embodiment includes a plurality of storage tanks 2, a concentration measurement unit 21 configured to measure the concentration of the waste water-soluble coolant C in each storage tank 2, a mixer 3 configured to mix the waste water-soluble coolant C in each storage tank 2 to prepare a coolant mixture M, and a fermenter 4 configured to ferment the coolant mixture M. The configurations of the storage tanks 2, the concentration measurement unit 21, the mixer 3, and the fermenter 4 in the biogas production system 104 are the same as those of the biogas production system 1 of embodiment 1. In addition, the mixing tank 32 of the mixer 3 is provided with a second concentration measurement unit 61 configured to measure the concentration of the coolant mixture M. The configuration of the second concentration measurement unit 61 is the same as that of the biogas production system 102 of embodiment 2.

[0054] The biogas production system 104 also has a third concentration measurement unit 63 configured to be able to measure the concentration of the digested liquid I, and a dilution device 604 configured to be able to use tap water W and the digested liquid I as the dilution liquid D. The configuration of the third concentration measurement unit 63 is the same as that of the biogas production system 103 of embodiment 3. The configuration of the dilution device 604 is the same as that of the dilution device 603 in the biogas production system 103 of embodiment 3, except that the dilution device 604 is configured to supply tap water W and the digested liquid I as the dilution liquid D to the fermentation device 4 and dilute the coolant mixed liquid M in the fermentation device 4.

[0055] 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 .

[0056] The metal removal device 7 is disposed upstream of the fermentation device 4 and is configured to remove metal components from the waste water-soluble coolant C and / or the coolant mixture M. The waste water-soluble coolant C and the coolant mixture M may contain metal components such as metal powder and cuttings generated during machining. These metal components may adversely affect the fermentation of the coolant mixture M in the fermentation device 4. In response to this, by providing the metal removal device 7 upstream of the fermentation device 4 and removing the metal components from the waste water-soluble coolant C and / or the coolant mixture M as in the biogas production system 104 of this embodiment, the impact of the metal components on the fermentation of the coolant mixture M can be reduced. As a result, it is expected that the fermentation of the coolant mixture M in the fermentation device 4 can be performed more efficiently.

[0057] Specifically, the metal removal device 7 may be disposed on the path of the waste water-soluble coolant C and the coolant mixture M from the storage tank 2 to the fermentation device 4. For example, the metal removal device 7 of this embodiment is disposed between the mixing tank 32 and the fermentation device 4, and is configured to be able to remove metal components contained in the coolant mixture M.

[0058] 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 waste water-soluble coolant C and the coolant mixture M. For example, the metal removal device 7 may have a filter 71 that filters out metal components from the waste water-soluble coolant C and the coolant mixture M. In this case, the metal removal device 7 may have a single filter 71 or multiple types of filters 71 with different filtering performances. Furthermore, the filter 71 may be a known filter such as a mesh filter or a ceramic filter.

[0059] Although not shown, the metal removal device 7 may also include a device that separates metal components by utilizing gravity, such as a settling tank for precipitating metal components, a device that separates metal components by utilizing centrifugal force, such as a liquid cyclone, or a device that separates metal components by utilizing electromagnetic force, such as a magnetic separator. These devices may be used alone, or two or more of these devices may be used in combination.

[0060] The inhibitor conversion device 8 is disposed upstream of the fermenter 4 and is configured to convert fermentation inhibitors in the waste water-soluble coolant C and / or the coolant mixture M into other substances. The waste water-soluble coolant C and the coolant mixture M may contain additives such as surfactants and preservatives, which may act as fermentation inhibitors that adversely affect the fermentation of the coolant mixture M in the fermenter 4. In response to this, as in the biogas production system 104 of this embodiment, the inhibitor conversion device 8 is provided upstream of the fermenter 4 and converts the fermentation inhibitors in the waste water-soluble coolant C and / or the coolant mixture M into other substances, thereby reducing the impact of the fermentation inhibitors on the fermentation of the coolant mixture M. As a result, it is expected that the fermentation of the coolant mixture M in the fermenter 4 will be more efficient.

[0061] Specifically, the inhibitor conversion device 8 may be disposed on the path of the waste water-soluble coolant C and the coolant mixture M from the storage tank 2 to the fermenter 4. For example, the inhibitor conversion device 8 of this embodiment is disposed between the metal removal device 7 and the fermenter 4, and is configured to be able to convert fermentation inhibitors contained in the coolant mixture M into other substances.

[0062] In the inhibitor conversion device 8, the method for converting fermentation inhibitors into other substances is not particularly limited, and an appropriate method can be adopted depending on the type of fermentation inhibitor contained in the waste water-soluble coolant C and the coolant mixture M. For example, the inhibitor conversion device 8 may be configured to convert fermentation inhibitors into other substances using an electrical method such as electrolysis. Alternatively, the inhibitor conversion device 8 may be configured to convert fermentation inhibitors into other substances using a chemical method such as adding an inhibitor treatment agent that reacts with the fermentation inhibitor. Furthermore, the inhibitor conversion device 8 may be configured to convert fermentation inhibitors into other substances using a physical method such as ultrasonic irradiation. The inhibitor conversion device 8 may be configured to perform one of these methods, or to perform a combination of two or more methods.

[0063] When the biogas production system 104 includes the metal removal device 7 and / or the inhibitor conversion device 8, as in this embodiment, the dilution device 603 is preferably configured to be able to supply the dilution liquid D downstream of the metal removal device 7 and the inhibitor conversion device 8. In this case, the concentration of the coolant mixture M can be adjusted to a desired concentration while avoiding an increase in the amount of liquid to be treated in the metal removal device 7 and the inhibitor conversion device 8. This makes it easier to make the biogas production system 104 more compact.

[0064] The gas separation device 44 is connected to the fermentation device 4 and is configured to be able to separate methane and gases other than methane from the biogas G produced in the fermentation device 4. The methane separated in the gas separation device 44 is stored in a methane tank 504.

[0065] The biogas production system 104 equipped with the gas separation device 44 can efficiently produce methane, which is a highly useful resource. The methane produced in this way can be used for a variety of purposes, such as fuel for power generation, gas material for carburizing heat treatment, and raw material for chemical compounds.

[0066] Although not shown in the figure, the gas separation device 44 may be configured to separate carbon dioxide from the biogas G. In this case, in addition to methane, carbon dioxide can be reused as a resource.

[0067] Specific aspects of the biogas production system according to the present disclosure have been described above based on embodiments 1 to 4, but the specific aspects of the biogas production system according to the present disclosure are not limited to the aspects shown in the above-mentioned embodiments, and the configuration can be changed as appropriate within the scope that does not detract from the spirit of the present disclosure.

[0068] For example, in the second embodiment, an example of the biogas production system 102 is shown that is configured to be able to dilute the coolant mixture M with tap water W as the diluent D, but instead of using tap water W as the diluent D, it is also possible to adopt a configuration that uses the digestive fluid I as the diluent D. In this case, for example, a digestive fluid pump may be connected between the drain pipe 41 and the mixing tank 32, and a third concentration measurement unit may be provided between the drain pipe 41 and the digestive fluid pump, and the amount of diluent D supplied may be adjusted based on the concentration of the coolant mixture M measured by the second concentration measurement unit and the concentration of the digestive fluid I measured by the third concentration measurement unit.

[0069] Furthermore, for example, in the fourth embodiment, an example of the biogas production system 104 is shown that is configured to be able to use both tap water W and digested liquid I as the diluent D, but it is also possible to configure it to use only either tap water W or digested liquid I as the diluent D. For example, when only tap water W is used as the diluent D, the third concentration measurement unit 63 and the digested liquid pump 64 can be removed from the biogas production system 104. For example, when only digested liquid I is used as the diluent D, the water pump 62 can be removed from the biogas production system 104.

Claims

1. A biogas production system configured to be able to produce biogas using waste water-soluble coolant recovered from a processing device that performs machining, a plurality of storage tanks configured to be able to separate and store the waste water-soluble coolant recovered from the processing device by type; a concentration measuring unit configured to be able to measure the concentration of the waste water-soluble coolant in each of the storage tanks; a mixing device configured to prepare a coolant mixture containing a plurality of the water-soluble waste coolants by mixing the water-soluble waste coolants in the storage tanks at a ratio calculated based on the concentrations of the water-soluble waste coolants; a fermentation device configured to generate the biogas by fermenting the coolant mixture supplied from the mixing device using microorganisms; a dilution device configured to be able to supply a diluting liquid to at least one liquid selected from the group consisting of the waste water-soluble coolant and the coolant mixture; a second concentration measuring unit configured to be able to measure the concentration of the coolant mixture, The biogas production system, wherein the dilution device is configured to be able to adjust the supply amount of the diluted liquid based on the concentration of the coolant mixed liquid.

2. 2. The biogas production system according to claim 1, wherein the concentration measurement unit has a COD sensor configured to measure the chemical oxygen demand of the waste water-soluble coolant and is configured to measure the concentration based on the chemical oxygen demand of the waste water-soluble coolant.

3. 3. The biogas production system according to claim 1, wherein the second concentration measurement unit has a COD sensor configured to be able to measure the chemical oxygen demand of the coolant mixture and is configured to be able to measure the concentration based on the chemical oxygen demand of the coolant mixture.

4. 3. The biogas production system according to claim 1 or 2, further comprising a third concentration measuring unit configured to be able to measure the concentration of a digestive liquid consisting of the coolant mixed liquid fermented in the fermentation apparatus, and the dilution device is configured to use the digestive liquid as the diluting liquid and to be able to adjust the supply amount of the diluting liquid based on the concentration of the coolant mixed liquid and the concentration of the digestive liquid.

5. 5. The biogas production system according to claim 4, wherein the third concentration measurement unit has a COD sensor configured to be able to measure the chemical oxygen demand of the digestive liquid and is configured to be able to measure the concentration based on the chemical oxygen demand of the digestive liquid.

6. 3. The biogas production system according to claim 1, further comprising a metal removal device arranged upstream of the fermentation device and configured to remove metal components from the water-soluble waste coolant and / or the coolant mixture.

7. 3. The biogas production system according to claim 1, further comprising an inhibitor conversion device arranged upstream of the fermentation device and configured to convert fermentation inhibitors in the waste water-soluble coolant and / or the coolant mixture into other substances.

8. The biogas production system according to claim 7 , wherein the dilution device is configured to be able to supply the diluted liquid downstream of the inhibitor conversion device.

9. The biogas production system according to any one of claims 1 to 8, wherein the fermentation apparatus is configured to be capable of generating biogas containing methane.

10. The biogas production system according to claim 9 , further comprising a gas separation device configured to separate methane from the biogas produced in the fermentation device.

11. The biogas production system according to claim 10, further comprising a methane tank configured to store the methane separated in the gas separation device.

12. The biogas production system according to any one of claims 1 to 11, wherein the machining is cutting or grinding.

13. (delete)