Biogas production system and method for producing sludge

Abstract

To provide a biogas production apparatus that enables production of biogas from waste water-soluble coolant used in machining, and a method for producing sludge suitable for fermentation of the waste coolant.SOLUTION: A biogas production system 1 produces biogas using a waste water-soluble coolant C that is recovered from a machining device performing machining. The biogas production system 1 has: a coolant storage tank 2 in which the waste water-soluble coolant C is stored; a fermentation product collection device 3 that collects a fermentation product F generated in the coolant storage tank 2 by microorganisms in the waste water-soluble coolant C; an acclimation tank 4 that generates sludge M containing microorganisms by acclimating microorganisms in an acclimation solution A containing the waste water-soluble coolant C and the fermentation product F collected by the fermentation product collection device 3; and a fermentation device 5 that produces biogas G by fermenting the waste water-soluble coolant C through contact between the sludge M and the waste water-soluble coolant C.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a biogas production system and a method for producing sludge.

Background Art

[0002] In recent years, the magnitude of the impact of carbon dioxide emitted by human activities on the global environment has been regarded as a problem, and efforts towards achieving 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 apparatus that treats organic waste to produce methane.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when performing machining such as cutting, grinding, and polishing, a water-soluble coolant is used for the purpose of reducing friction between the workpiece and the tool, cooling the workpiece, washing, etc. Conventionally, the waste water-soluble coolant used during machining and discharged from the machining apparatus has been discarded after being detoxified. However, if the organic substances such as mineral oil contained in the waste water-soluble coolant can be recycled again, it is useful for achieving carbon neutrality. Therefore, the development of a technology for recycling the organic substances in the waste water-soluble coolant is desired.

[0005] The present invention has been made in view of such problems, and aims to provide a biogas production apparatus capable of producing biogas from waste water-soluble coolant used in machining and a method for producing sludge suitable for the fermentation of waste coolant.

Means for Solving the Problems

[0006] One aspect of the present invention is a biogas production system for producing biogas using waste water-soluble coolant recovered from a processing apparatus that performs machining, a coolant storage tank for storing the waste water-soluble coolant, a product collection device for collecting fermentation products generated in the coolant storage tank by microorganisms in the waste water-soluble coolant, a domestication tank for generating sludge containing the microorganisms by domesticating the microorganisms in the domestication liquid containing the waste water-soluble coolant and the fermentation products collected by the product collection device, and a fermentation device for generating biogas by fermenting the waste water-soluble coolant by bringing the sludge into contact with the waste water-soluble coolant.

[0007] Another aspect of the present invention is a method for producing sludge used for fermenting waste water-soluble coolant, recovering waste water-soluble coolant from a processing apparatus that performs machining, generating fermentation products by fermenting the waste water-soluble coolant by microorganisms in the waste water-soluble coolant, and producing the sludge by domesticating the microorganisms in the domestication liquid containing the fermentation products and the waste water-soluble coolant.

Advantages of the Invention

[0008] The biogas production system has a coolant storage tank configured to be able to generate fermentation products of waste water-soluble coolant in the coolant storage tank. The fermentation products in the coolant storage tank contain microorganisms suitable for fermenting the waste water-soluble coolant. Therefore, by collecting the fermentation products with the product collection device and domesticating the microorganisms in the domestication liquid containing the fermentation products in the domestication tank, the microorganisms suitable for fermenting the waste water-soluble coolant can be propagated, and sludge containing such microorganisms at a high concentration can be efficiently generated.

[0009] Further, the biogas production system can quickly adjust the environment in the fermentation device to an environment suitable for the fermentation of the waste water-soluble coolant by putting the sludge thus obtained into the fermentation device and bringing it into contact with the waste water-soluble coolant in the fermentation device. As a result, the fermentation efficiency of the waste water-soluble coolant can be quickly improved, and biogas can be efficiently produced from the waste water-soluble coolant.

[0010] Also, in the method for producing the sludge, after recovering the waste water-soluble coolant from the processing device, the waste water-soluble coolant is fermented to produce a fermentation product. Then, by using this fermentation product to domesticate microorganisms, sludge suitable for the fermentation of the waste water-soluble coolant can be efficiently produced.

[0011] As described above, according to the above aspect, it is possible to provide a biogas production device capable of producing biogas from the waste water-soluble coolant used in machining and a method for producing sludge suitable for the fermentation of waste coolant.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0013] (Embodiment 1) An embodiment of the biogas production system will be described with reference to FIGS. 1 and 2. The biogas production system 1 of this embodiment is configured to be able to produce biogas G using waste water-soluble coolant C recovered from a processing device that performs machining. As shown in FIG. 1, it has a coolant storage tank 2, a product collection device 3, an acclimation tank 4, and a fermentation device 5.

[0014] The waste water-soluble coolant C used in the biogas production system 1 is recovered from various processing devices such as a cutting device, a grinding device, and a polishing device. The waste water-soluble coolant C may contain, in addition to mineral oil and surfactant contained in the water-soluble coolant for machining, organic substances in which the components in the water-soluble coolant have deteriorated. The biogas production system 1 can use waste water-soluble coolant C such as an emulsion-type waste water-soluble coolant in which a cutting oil component is dispersed in water, a solution-type waste water-soluble coolant in which a cutting oil component is dissolved in water, and a soluble-type waste water-soluble coolant which is an intermediate form between the emulsion type and the solution type. Further, the waste water-soluble coolant C may contain machining chips such as cutting chips, grinding chips, and polishing powder discharged from the processing device.

[0015] The coolant storage tank 2 is configured to be able to store the waste water-soluble coolant C recovered from the processing device. The mode of recovering the waste water-soluble coolant C from the processing device is not particularly limited and can take various modes. For example, the coolant storage tank 2 and the processing device are connected via a coolant collection pipe 21, and the waste water-soluble coolant C discharged from the processing device is directly allowed to flow into the coolant storage tank 2, whereby the waste water-soluble coolant C discharged from the processing device can be recovered. In this case, one processing device may be connected to one coolant storage tank 2, or a plurality of processing devices may be connected.

[0016] Further, for example, after collecting the waste water-soluble coolant C discharged from each processing device into a recovery container, the waste water-soluble coolant C in the recovery container can be recovered by flowing it into the coolant storage tank 2.

[0017] The waste water-soluble coolant C usually contains microorganisms capable of fermenting the waste water-soluble coolant C. Therefore, by storing the waste water-soluble coolant C in the coolant storage tank 2, the waste water-soluble coolant C can be fermented in the coolant storage tank 2, and fermentation products F such as floating substances called scum Sc and precipitates called sludge Sl can be generated in the coolant storage tank 2.

[0018] The waste water-soluble coolant C in the coolant storage tank 2 preferably contains machining chips having conductivity generated in the processing device. The machining chips having conductivity have an effect of further promoting the fermentation of the waste water-soluble coolant C in the coolant storage tank 2. Therefore, in this case, the fermentation product F can be generated more easily.

[0019] The fermentation product F in the coolant storage tank 2 is collected by the product collection device 3. The specific form of the product collection device 3 is not particularly limited and can take various forms. For example, the product collection device 3 of the present embodiment connects the inside of the coolant storage tank 2 and the domestication tank 4, and has a product collection pipe 31 for guiding the scum Sc and / or sludge Sl in the coolant storage tank 2 to the domestication tank 4, and a product collection pump 32 disposed on the path of the product collection pipe 31 for sending the fermentation product F in the coolant storage tank 2 to the domestication tank 4. The biogas production system 1 of the present embodiment can directly guide the scum Sc and sludge Sl in the coolant storage tank 2 to the domestication tank 4 through the product collection pipe 31 and use them for the domestication of microorganisms in the domestication tank 4.

[0020] Also, although not shown in the figures, the product collection device 3 may have a dehydration unit that generates a dehydrated cake by dehydrating, for example, scum Sc and sludge Sl in the coolant storage tank 2 after collecting them. The dehydrated cake thus obtained contains microorganisms that can ferment the waste water-soluble coolant C in the same manner as scum Sc and sludge Sl. Therefore, the dehydrated cake can be used for culturing microorganisms in the culturing tank 4 in the same manner as scum Sc and sludge Sl.

[0021] When conductive processing scraps are contained in the coolant storage tank 2, the fermentation product F may contain conductors such as processing scraps and digested products of processing scraps by microorganisms in the waste water-soluble coolant C. These conductors have the effect of promoting the fermentation of the waste water-soluble coolant C in the coolant storage tank 2 and the culturing of microorganisms in the culturing tank 4. On the other hand, if the size of the conductors contained in the fermentation product F is excessively large, it may be difficult to stir the culture solution A in the culturing tank 4. From the viewpoint of more easily avoiding such problems, it is preferable that the product collection device 3 has a processing scrap separation unit 33 that separates the fermentation product F and the processing scraps.

[0022] The specific form of the processing scrap separation unit 33 can take various forms. For example, the processing scrap separation unit 33 may be a filter such as a wire mesh, punching metal, expanded metal, or wedge wire screen.

[0023] Also, it is preferable that the processing scrap separation unit 33 is configured to be able to separate processing scraps having a maximum length of 1 mm or more, for example. In this case, while avoiding the entry of excessively large processing scraps into the culturing tank 4, relatively small processing scraps and their digested products can enter the culturing tank 4. Thereby, the culturing of microorganisms in the culturing tank 4 can be further promoted. Note that the aforementioned "maximum length" refers to the maximum value of the length of the processing scraps when the lengths of the processing scraps are measured in various directions.

[0024] The acclimation tank 4 is configured to be able to acclimate the microorganisms in the acclimation liquid A containing the fermentation product F collected by the product collection device 3 and the waste water-soluble coolant C. The fermentation product F generated in the coolant storage tank 2 contains microorganisms suitable for the fermentation of the waste water-soluble coolant C at a relatively high concentration. By acclimating such microorganisms in the acclimation liquid A, it is possible to further grow the microorganisms suitable for the fermentation of the waste water-soluble coolant C and generate sludge M containing high-concentration microorganisms.

[0025] The method of acclimating microorganisms in the acclimation tank 4 can take various forms. For example, the acclimation tank 4 of this embodiment is connected to the coolant storage tank 2 via the product collection pipe 31 as described above. Further, the acclimation tank 4 is connected to the coolant storage tank 2 via the coolant collection pipe 21 that collects the waste water-soluble coolant C in the coolant storage tank 2. Therefore, by mixing the fermentation product F flowing in from the product collection pipe 31 and the waste water-soluble coolant C flowing in from the coolant collection pipe 21 in the acclimation tank 4, the acclimation liquid A can be prepared. Then, by fermenting the acclimation liquid A in the acclimation tank 4 under an anaerobic atmosphere, the microorganisms in the acclimation liquid A can be acclimated to generate sludge M.

[0026] The acclimation tank 4 may have a stirring device 41 for stirring the acclimation liquid A. By using the stirring device 41 to stir the acclimation liquid A in the acclimation tank 4, the fermentation of the acclimation liquid A can be further promoted and the time required for acclimation can be further shortened. Also, although not shown in the figure, the acclimation tank 4 may have a temperature control device for adjusting the temperature of the acclimation liquid A. By using the temperature control device to adjust the temperature of the acclimation liquid A in the acclimation tank 4 to a temperature suitable for fermentation, the fermentation of the acclimation liquid A can be further promoted and the time required for acclimation can be further shortened.

[0027] Although not shown in the drawings, when the cultivation tank 4 is separated from the coolant storage tank 2, for example, by mixing the fermentation product F such as the dehydrated cake collected by the product collection device 3 and the waste water-soluble coolant C in the cultivation tank 4, the cultivation liquid A can be prepared. Then, by fermenting the cultivation liquid A in the cultivation tank 4 under an anaerobic atmosphere, the microorganisms in the cultivation liquid A can be cultivated to generate the sludge M.

[0028] It is preferable that the cultivation liquid A in the cultivation tank 4 contains a conductor. In this case, the cultivation of microorganisms in the cultivation tank 4 can be further promoted, and the sludge M containing a high concentration of microorganisms can be more easily generated. Examples of the conductor contained in the cultivation liquid A include conductive processing scraps generated in the processing device and their digested products. The maximum length of the conductor is preferably less than 1 mm. In this case, the cultivation liquid A in the cultivation tank 4 can be more easily stirred.

[0029] The sludge M generated in the cultivation tank 4 contains a high concentration of microorganisms suitable for the fermentation of the waste water-soluble coolant C. Therefore, by introducing the sludge M in the cultivation tank 4 into the fermentation device 5, the environment in the fermentation device 5 can be quickly adjusted to an environment suitable for the fermentation of the waste water-soluble coolant C.

[0030] The method of introducing the sludge M in the cultivation tank 4 into the fermentation device 5 is not particularly limited and can take various forms. For example, the cultivation tank 4 of this embodiment has a sludge delivery section 42 that guides the sludge M from the cultivation tank 4 to the fermentation device 5. The sludge delivery section 42 has, for example, a sludge delivery pipe 421 that connects the cultivation tank 4 and the fermentation device 5, and a sludge delivery pump 422 that is arranged on the path of the sludge delivery pipe 421 and delivers the sludge M in the cultivation tank 4 to the fermentation device 5. Therefore, the biogas production system 1 of this embodiment can directly guide the sludge M in the cultivation tank 4 to the fermentation device 5 through the sludge delivery pipe 421 and use it for the fermentation of the waste water-soluble coolant C in the fermentation device 5.

[0031] Although not shown in the figure, the biogas production system 1 may have, for example, a sludge tank that is connected to the fermentation device 5 and stores the sludge M. In this case, the sludge M in the acclimation tank 4 is temporarily stored in the sludge tank, and the sludge in the sludge tank is supplied to the fermentation device 5 as needed, so that the sludge M can be used for the fermentation of the waste water-soluble coolant C in the fermentation tank 51.

[0032] The biogas production system 1 may have a conductor separation unit 43 that separates the sludge M generated in the acclimation tank 4 from the conductor. For example, the biogas production system 1 of the present embodiment has a conductor separation unit 43 between the sludge delivery pump 422 and the fermentation device 5 on the path of the sludge delivery pipe 421. When the conductor is contained in the acclimation liquid A, the conductor may be contained in the sludge M generated in the acclimation tank 4. These conductors have the effect of promoting the fermentation of the waste water-soluble coolant C in the fermentation device 5. On the other hand, if the size of the conductor contained in the sludge M is excessively large, it may hinder the flow of the waste water-soluble coolant C in the fermentation device 5. Therefore, even when the sludge M contains a conductor, by separating the sludge M from the conductor by the conductor separation unit 43 and then supplying the sludge M to the fermentation device 5, such problems can be more easily avoided.

[0033] The specific form of the conductor separation unit 43 can take various forms. For example, the conductor separation unit 43 may be a filter such as a wire mesh, punching metal, expanded metal, or wedge wire screen.

[0034] The conductor separation unit 43 is preferably configured to be able to separate, for example, a conductor having a maximum length of 10 μm or more. In this case, while avoiding the entry of an excessively large conductor into the fermentation device 5, a relatively small conductor can be allowed to enter the fermentation device 5. Thereby, the fermentation of the waste water-soluble coolant C in the fermentation device 5 can be further promoted. The "maximum length" described above refers to the maximum value of the length of the conductor when the length of the conductor is measured in various directions.

[0035] The specific configuration of the fermentation device 5 in the biogas production system 1 is not particularly limited and can take various forms. From the perspective of more efficiently fermenting the waste water-soluble coolant C, the fermentation device 5 is preferably a down-flow hanging sponge (DHS) reactor.

[0036] That is, as shown in FIG. 2, the fermentation device 5 includes a fermentation tank 51, a plurality of sludge carriers 52 disposed in the fermentation tank 51 and configured to be capable of carrying the sludge M, a coolant discharge section 54 that discharges the waste water-soluble coolant C outside the fermentation device 5 after it has come into contact with the sludge carrier 52. In FIG. 1, for the sake of simplicity, the fermentation device 5 is described in a simplified manner.

[0037] Since the fermentation device 5 configured as a DHS reactor has a large number of sludge carriers 52 in the fermentation tank 51, a large amount of sludge M can be carried on these sludge carriers 52. Therefore, by fermenting the waste water-soluble coolant C using the fermentation device 5, the waste water-soluble coolant C and the microorganisms in the sludge M can be sufficiently brought into contact, and the fermentation of the waste water-soluble coolant C can be carried out more efficiently.

[0038] The shape and size of the fermentation tank 51 in the fermentation device 5 can take various forms. For example, the shape of the fermentation tank 51 in the fermentation device 5 of this embodiment is a cylindrical shape with a diameter of 2 m. Also, the height of the fermentation tank 51 is 2 m.

[0039] A partition plate 56 is provided in the fermentation tank 51 to partition its internal space 55 into an upper space 551 and a lower space 552. The partition plate 56 is configured such that the waste water-soluble coolant C and the sludge M can flow through it.

[0040] The sludge carrier 52 is placed on the partition plate 56 in the upper space 551 of the fermentation tank 51. As the sludge carrier 52, for example, a porous body such as a resin sponge, a cylindrical body such as plastic formed into a cylindrical shape, a porous body with a plastic frame provided around the porous body, etc. can be used. Specifically, the sludge carrier 52 of this embodiment is a porous body with a plastic frame provided around a resin sponge.

[0041] The sludge M generated in the domestication tank 4 is carried on the sludge carrier 52. As described above, the sludge M contains a high concentration of microorganisms suitable for the fermentation of the waste water-soluble coolant C. Therefore, by bringing the sludge M into contact with the waste water-soluble coolant C, the microorganisms in the sludge M digest the organic matter in the waste water-soluble coolant C, and biogas G is generated.

[0042] The composition of the biogas G produced in the biogas production system 1 varies depending on the types of microorganisms in the sludge M and the environment during fermentation. For example, if the domestication of microorganisms is carried out in an anaerobic atmosphere, sludge M containing methane-producing bacteria such as Methanobacterium and Methanosarcina can be produced. Therefore, by fermenting the waste water-soluble coolant C using the sludge M containing methane-producing bacteria, biogas G containing methane can be obtained.

[0043] The coolant spraying unit 53 is configured to be able to spray the waste water-soluble coolant C onto the sludge carrier 52. The waste water-soluble coolant C sprayed from the coolant spraying unit 53 may be supplied from the coolant storage tank 2. Also, the waste water-soluble coolant C sprayed from the coolant spraying unit 53 may be supplied from a device different from the coolant storage tank 2. For example, the coolant spraying unit 53 of this embodiment is connected to the coolant sampling pipe 21 and is configured to be able to receive the supply of the waste water-soluble coolant C from the coolant storage tank 2 as shown in FIG. 1.

[0044] The specific form of the coolant spraying unit 53 is not particularly limited and can take various forms. For example, the coolant spraying unit 53 of this embodiment is arranged above the sludge carrier 52 as shown in FIG. 2, and is configured to spray the waste water-soluble coolant C from above the sludge carrier 52. In this way, by arranging the coolant spraying unit 53 above the sludge carrier 52, the waste water-soluble coolant C can be easily sprayed over the entire sludge carrier 52 in the fermentation tank 51, and the fermentation of the waste water-soluble coolant C can be carried out more efficiently.

[0045] Although not shown in the figure, the coolant spraying unit 53 may be arranged along the side surface in the upper space 551 of the fermentation tank 51 and may be configured to spray the waste water-soluble coolant C from the side of the sludge carrier 52.

[0046] As the coolant spraying unit 53, for example, a sprinkler nozzle configured to be able to spray the waste water-soluble coolant C into the fermentation tank 51, a water spray pipe provided with small holes for discharging the waste water-soluble coolant C, etc. can be used.

[0047] The fermentation tank 51 may be provided with a gas outlet 57 for guiding the biogas G generated by the fermentation of the waste water-soluble coolant C to the outside of the fermentation tank 51. For example, the gas outlet 57 of this embodiment is provided at the upper end of the fermentation tank 51.

[0048] The biogas G led out from the gas outlet 57 is used for various purposes according to its composition. For example, the biogas G containing methane can be used for various purposes. For example, the biogas G containing methane is used as fuel for a generator, etc. Also, methane purified from the biogas G may be used as a raw material for C1 chemistry, for example.

[0049] In the biogas production system 1 of this embodiment, the biogas G led out from the gas outlet 57 is separated into methane and other components in the gas separation unit 61 shown in FIG. 1. Then, the methane separated in the gas separation unit 61 is stored in the methane tank 6.

[0050] As shown in FIG. 2, the lower space 552 is provided with a coolant discharge pipe 541 that opens into the lower space 552, and a coolant discharge section 54 is provided to discharge the waste water-soluble coolant C and sludge M stored in the lower space 552 to the outside of the fermentation device 5. The specific form of the coolant discharge section 54 is not particularly limited and can take various forms. For example, in the coolant discharge section 54 of this embodiment, the coolant discharge pipe 541 protrudes from the side surface of the fermentation tank 51 into the lower space 552 and opens into the lower space 552. The coolant discharge pipe 541 is configured to be able to extract the waste water-soluble coolant C and sludge M stored in the lower space 552 from the lower space 552 and guide them to the outside of the fermentation device 5.

[0051] The method of introducing the sludge M into the fermentation device 5 can take various forms. For example, the fermentation device 5 of this embodiment has a sludge spraying section 58 that sprays the sludge M onto the sludge carrier 52. The sludge spraying section 58 is configured to be able to spray the sludge M into the fermentation tank 51 at a desired timing. By spraying the sludge M into the fermentation tank 51 by the sludge spraying section 58, the fermentation efficiency of the waste water-soluble coolant C in the fermentation tank 51 can be improved. Examples of the timing for spraying the sludge M include when the operation of the fermentation device 5 is started, or when the amount of microorganisms in the fermentation tank 51 decreases and the production amount of biogas G decreases.

[0052] The specific form of the sludge spraying section 58 is not particularly limited. For example, in this embodiment, the sludge spraying section 58 is arranged above the sludge carrier 52. Also, as shown in FIG. 1, the sludge spraying section 58 is connected to the sludge delivery pipe 421 and is configured to be able to spray the sludge M that has passed through the conductor separation section 43 onto the sludge carrier 52. As the sludge spraying section 58, a sprinkler nozzle configured to be able to spray the sludge M into the upper space 551 of the fermentation tank 51, a water sprinkling pipe provided with small holes for discharging the sludge M, etc. can be used.

[0053] The biogas production system 1 of this embodiment has a coolant storage tank 2, and in the coolant storage tank 2, it is configured to be able to ferment the waste water-soluble coolant C recovered from the processing device to generate a fermentation product F. The fermentation product F thus obtained contains microorganisms suitable for the fermentation of the waste water-soluble coolant C. Therefore, by collecting the fermentation product F with the product collection device 3 and culturing the microorganisms in the culture solution A containing the fermentation product F in the culture tank 4, microorganisms suitable for the fermentation of the waste water-soluble coolant C can be propagated, and sludge M containing such microorganisms at a high concentration can be efficiently generated.

[0054] Also, the biogas production system 1 inputs the sludge M thus obtained into the fermentation device 5 and brings it into contact with the waste water-soluble coolant C in the fermentation device 5, so that the environment in the fermentation device 5 can be quickly adjusted to an environment suitable for the fermentation of the waste water-soluble coolant C. As a result, the fermentation efficiency of the waste water-soluble coolant C can be quickly improved, and biogas G can be efficiently produced from the waste water-soluble coolant C.

[0055] Also, from another perspective, the biogas production system 1 of this embodiment can also be used in a method for producing sludge M used for the fermentation of the waste water-soluble coolant C. That is, when producing sludge M using the biogas production system 1, first, the waste water-soluble coolant C is recovered from a processing device that performs machining. This waste water-soluble coolant C is stored in the coolant storage tank 2, and the waste water-soluble coolant C is fermented by the microorganisms in the waste water-soluble coolant C to generate a fermentation product F. Then, a culture solution A containing the fermentation product F and the waste water-soluble coolant C is prepared in the culture tank 4, and sludge M can be generated by culturing the microorganisms in the culture solution A.

[0056] The sludge M thus obtained may be directly sent from the domestication tank 4 to the fermentation device 5. Although not shown in the figure, the sludge M can also be taken out from the domestication tank 4, dehydrated, and stored in the form of a dehydrated cake. In this case, if necessary, after mixing the dehydrated cake with water or the like and then supplying it to the fermentation device 5, the inside of the fermentation device 5 can be adjusted to an environment suitable for the fermentation of the waste water-soluble coolant C.

[0057] In the method for producing the sludge, after recovering the waste water-soluble coolant C from the processing device, the waste water-soluble coolant C is fermented to produce a fermentation product F. Then, by domestication of microorganisms using this fermentation product F, sludge M suitable for the fermentation of the waste water-soluble coolant C can be efficiently produced.

[0058] In the method for producing the sludge, it is preferable to recover the processing scraps together with the waste water-soluble coolant C from the processing device and ferment the waste water-soluble coolant C to produce a fermentation product F containing microorganisms and processing scraps. As described above, the processing scraps having conductivity have the effect of further promoting the fermentation of the waste water-soluble coolant C. Therefore, in this case, the fermentation product F can be more easily produced.

[0059] (Embodiment 2) In this embodiment, an example of a biogas production system equipped with a carrier input unit for inputting a microorganism carrier into a fermentation tank will be described. Among the reference numerals used after Embodiment 2, the same reference numerals as those used in the previous embodiments represent the same components and the like as the components in the previous embodiments unless otherwise specified.

[0060] As shown in FIG. of the biogas production system 102 of this embodiment, a coolant storage tank 2, a product collection device 3, a processing scrap separation unit 33, a domestication tank 4, a sludge delivery unit 42, a conductor separation unit 43, a fermentation device 502, a gas separation unit 61, and a methane tank 6. The configuration of the parts other than the fermentation device 5 in the biogas production system 102 of this embodiment is the same as the configuration of the corresponding parts in the biogas production system 1 of Embodiment 1.

[0061] As shown in FIG. 3, the fermentation device 502 includes a fermentation tank 51 and a partition plate 56 that divides the internal space 55 of the fermentation tank 51 into an upper space 551 and a lower space 552. In the upper space 551 of the fermentation tank 51, a sludge carrier 52, a coolant spraying section 53, a gas outlet section 57, and a sludge spraying section 58 are provided. Further, a coolant discharge section 54 is provided in the lower space 552 of the fermentation tank 51. The configurations of these parts in the fermentation device 502 of the present embodiment are the same as those of the corresponding parts in the fermentation device 5 of the first embodiment. In FIG. 3, for convenience, the fermentation device 502 is described in a simplified manner.

[0062] Further, the fermentation device 502 of the present embodiment has a carrier charging section 59 for charging the sludge carrier 52 into the fermentation tank 51. The carrier charging section 59 is configured to be able to charge the sludge carrier 52 into the fermentation tank 51 at a desired timing. The specific configuration of the carrier charging section 59 can take various forms. For example, the carrier charging section 59 of the present embodiment has a carrier holding section 591 for holding the sludge carrier 52 and a carrier charging pipe 592 for guiding the sludge carrier 52 in the carrier holding section 591 to the upper space 551 of the fermentation tank 51. Further, the carrier charging pipe 592 opens to the top wall of the upper space 551 of the fermentation tank 51 and is configured to drop the sludge carrier 52 from above the sludge spraying section 58 and charge it into the upper space 551.

[0063] The fermentation device 502 of the present embodiment has a sludge spraying section 58 and a carrier charging section 59. Thus, by providing the carrier charging section 59 together with the sludge spraying section 58, the charging of the sludge carrier 52 and the spraying of the sludge M can be performed alternately. Therefore, the fermentation device 502 of the present embodiment can easily attach the sludge M to the sludge carrier 52 located below the fermentation tank 51, for example, when preparing to ferment the waste water-soluble coolant C. As a result, the environment inside the fermentation device 5 can be adjusted more quickly to an environment suitable for the fermentation of the waste water-soluble coolant C. In addition, the biogas production system 102 of the present embodiment can achieve the same operational effects as the biogas production system 1 of the first embodiment.

[0064] (Embodiment 3) In this embodiment, an example of a biogas production system equipped with a sludge adhesion device that adheres sludge to a microbial carrier will be described. As shown in Figure 4, the biogas production system 103 of this embodiment includes a coolant storage tank 2, a product collection device 3, a processing waste separation section 33, an acclimation tank 4, a sludge discharge section 42, a conductor separation section 43, a fermentation device 502, a gas separation section 61, and a methane tank 6.

[0065] The fermenter 502 also includes a fermenter 51 and a partition plate 56 that divides the internal space 55 of the fermenter 51 into an upper space 551 and a lower space 552. The upper space 551 of the fermenter 51 is provided with a sludge carrier 52, a coolant sprayer 53, a gas outlet 57, and a sludge sprayer 58. The lower space 552 of the fermenter 51 is provided with a coolant discharge unit 54. The fermenter 502 also includes a carrier feed unit 59 that feeds the sludge carrier 52 into the fermenter 51. The configurations of these components in the biogas production system 103 of this embodiment are similar to the configurations of the corresponding components in the biogas production system 102 of the second embodiment. For convenience, the fermenter 502 is shown in a simplified form in FIG. 4.

[0066] The biogas production system 103 of this embodiment also has a sludge adhesion device 7 that causes sludge M to adhere to the sludge carrier 52. The sludge adhesion device 7 is configured to mix the sludge M produced in the acclimation tank 4 with the sludge carrier 52 and cause the sludge M to adhere to the sludge carrier 52. The specific embodiment of the sludge adhesion device 7 is not particularly limited, and various embodiments are possible. For example, the sludge adhesion device 7 may be an agitator configured to be able to mix the sludge M with the sludge carrier 52.

[0067] The sludge carrier 52 mixed with the sludge M by the sludge adhesion device 7 is supplied to the carrier input section 59. Then, the sludge carrier 52 in the carrier input section 59 is put into the fermentation tank 51 at a desired timing. In this way, by putting the sludge carrier 52 into the fermentation tank 51 after preliminarily adhering the sludge M to the sludge carrier 52 in the sludge adhesion device 7, the fermentation tank 51 can be filled with the sludge carrier 52 to which the sludge M adheres over the entire tank. As a result, the environment in the fermentation device 502 can be adjusted more promptly to an environment suitable for the fermentation of the waste water-soluble coolant C. In addition, the biogas production system 103 of the present embodiment can exhibit the same operational effects as the biogas production system 102 of the second embodiment.

[0068] As described above, the aspects of the biogas production system and the sludge production method have been described based on the first to third embodiments. However, the specific aspects of the biogas production system and the sludge production method according to the present invention are not limited to the above-described respective embodiments, and can be applied to various embodiments without departing from the gist thereof.

Explanation of Reference Numerals

[0069] 1, 102, 103 Biogas production system 2 Coolant storage tank 3 Product collection device 4 Acclimation tank 5, 502 Fermentation device A Acclimation liquid C Waste water-soluble coolant F Fermentation product G Biogas M Sludge

Claims

1. A biogas production system for producing biogas using waste water-soluble coolant recovered from a processing apparatus that performs machining, comprising: a coolant storage tank for storing the waste water-soluble coolant; a product collection device for collecting fermentation products generated in the coolant storage tank by microorganisms in the waste water-soluble coolant; a domestication tank for generating sludge containing the microorganisms by domestication of the microorganisms in the domestication liquid containing the waste water-soluble coolant and the fermentation products collected by the product collection device; a fermentation device for fermenting the waste water-soluble coolant to generate biogas by bringing the sludge into contact with the waste water-soluble coolant. A biogas production system.

2. The biogas production system according to claim 1, wherein the domestication liquid contains a conductor.

3. The biogas production system according to claim 2, wherein the biogas production system has a conductor separation unit for separating the sludge generated in the domestication tank from the conductor.

4. The biogas production system according to claim 1, wherein the waste water-soluble coolant in the coolant storage tank contains machining chips having conductivity generated in the processing apparatus.

5. The biogas production system according to claim 4, wherein the product collection device has a machining chip separation unit for separating the fermentation products from the machining chips.

6. The fermentation device includes: a fermentation tank; a plurality of microorganism carriers disposed in the fermentation tank and configured to be capable of supporting the sludge; a coolant spraying unit for spraying the waste water-soluble coolant onto the microorganism carriers; a coolant discharge unit for discharging the waste water-soluble coolant after contacting the microorganism carriers to the outside of the fermentation device. The biogas production system according to any one of claims 1 to 5.

7. The fermentation device according to claim 6, further comprising a sludge spraying unit for spraying the sludge onto the microorganism carriers.

8. The fermentation device according to claim 7, further comprising a carrier input unit for inputting the microorganism carriers into the fermentation tank.

9. The biogas production system has a sludge adhesion device for adhering the sludge to the microbial carrier, and the fermentation device has a carrier input section for inputting the microbial carrier with the sludge adhered thereto into the fermentation tank. The biogas production system according to claim 8.

10. The biogas production system according to claim 1, wherein the fermentation device is configured to generate the biogas containing methane.

11. A method for producing sludge used for fermentation of waste water-soluble coolant, recovering waste water-soluble coolant from a processing device that performs machining, generating a fermentation product by fermenting the waste water-soluble coolant by microorganisms in the waste water-soluble coolant, producing the sludge by domestication of microorganisms in the domestication liquid containing the fermentation product and the waste water-soluble coolant. A method for producing sludge.

12. The method for producing sludge according to claim 11, wherein machining chips are recovered together with the waste water-soluble coolant from the processing device, and the waste water-soluble coolant is fermented to generate the fermentation product containing the microorganisms and the machining chips.

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