JP7258485B2 - Methane fermentation device and methane fermentation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a methane fermentation apparatus and a methane fermentation method for introducing waste containing fermentation-suitable materials such as waste paper into a methane fermentation tank.

In a wet methane fermentation system, for example, separated garbage is stored in a solubilization tank. In the solubilization tank, hydrolysis and acid fermentation (that is, solubilization) of garbage proceed to obtain a slurry containing organic acids. After that, the slurry is sent to a methane fermenter and decomposed by anaerobic microorganisms in the methane fermenter. The biogas produced at this time generally contains about 60 vol% methane and about 40 vol% carbon dioxide, and is useful as an energy source.

From the viewpoint of reducing the volume of waste and increasing the amount of biogas produced, it is desirable to use not only raw garbage but also fermentation suitable materials including solid waste containing organic matter such as paper waste as raw materials. Patent Literature 1 proposes solubilizing organic solid waste while immersing it in a fermentation liquid in a tank and decomposing it into biogas.

On the other hand, Patent Document 2 discloses a sludge treatment system in which a circulation pipe and a pump are provided in a digestion tank for anaerobic digestion of raw sludge. It consists of an upper circulation pipe that opens at the top of the digestion tank, a lower circulation pipe that opens at the bottom of the digestion tank, and a discharge pipe that has a discharge port at the tip and generates a horizontal flow of sludge. It is proposed to be installed outside the digestion tank. Patent Document 2 promotes mixing of sludge in the digestion tank, equalizes the temperature of the sludge, diffuses digestion gas from the sludge, crushes scum on the sludge surface, and deposits sediment, screen residue, etc. in the sludge. intended to prevent

JP 2012-86157 A Japanese Patent Application Laid-Open No. 2007-229600

In a methane fermentation system that produces biogas from solid waste, the amount of biogas produced can be significantly increased, because not only food waste but also fermentation-suitable materials such as paper waste are used as raw materials.

Solid waste includes a variety of unfermentable materials such as plastics, metals, gravel, and egg shells. When solid waste is used as a raw material, materials unsuitable for fermentation are separated from the solid waste by pretreatment, and then the materials unsuitable for fermentation are introduced into the fermenter. Mix into the fermented material. Fermentation unsuitable substances cause various troubles in stirring the contents of the fermenter, extracting work, and the like. For example, blockage of the suction of the agitating pump, an increase in processing work for the extracted contents, a decrease in agitating efficiency of the contents, and the like may occur.

In particular, unsuitable substances that do not float on the surface of the fermentation broth and do not settle at the bottom of the fermentation tank, but that float in the fermentation broth (hereinafter also referred to as floating unsuitable substances) tend to accumulate in the fermentation broth. When the concentration of unsustainable substances in the fermentation broth increases, the probability of blockage failure occurring in pipes and equipment attached to the fermentation tank increases. As a result, it is necessary to frequently remove the fermentation liquid and clean the inside of the fermentation tank, which increases the management cost of the methane fermentation apparatus. In addition, a spare water tank is required for transferring the fermented liquid, which increases the equipment cost.

One aspect of the present invention includes a fermenter containing a fermentation liquid that generates biogas, a separation device for removing unfermented substances floating in the fermentation liquid taken out from the fermenter, and a separator in the separation device. a dehydrator for dehydrating the separated liquid from which unfermentable substances have been removed;
A dehydration route that supplies the separated liquid to the dehydrator, a recovery route that returns the separated liquid to the fermenter, and a supply destination of the separated liquid that is switched between the dehydration route and the recovery route. a filtering unit having a filtering surface for filtering the fermented liquid and having a plurality of slit-like gaps opening to the filtering surface; and a gap self-cleaning unit that conveys the unsuitable substances deposited on the filtration surface, and the switching device is obtained from the state of solid waste remaining on the filtration surface of the separation device. The present invention relates to a methane fermentation apparatus configured to be switchable between the dehydration route and the recovery route based on a determination result as to whether the fermentation of the fermented liquid has been completed or is in the middle of fermentation.

Another aspect of the present invention includes (i) a step of hydrolyzing, acid fermentation, and methane fermentation of a fermentable material in a fermenter containing a fermentation broth to generate biogas, and (ii) the fermenter. (iii) dehydrating the separated liquid from which the unsuitable substances for fermentation have been removed; (iv) removing the separated liquid from the and the step of removing unsuitable substances for fermentation includes introducing the fermented liquid into a filtration surface in which a plurality of slit-shaped gaps open, and allowing the fermented liquid to pass through the plurality of slit-shaped gaps. a step of draining and depositing the unsuitable substances for fermentation on the filtering surface; and a step of collecting the unsuitable substances for fermentation deposited on the filtering surface by a gap self-cleaning part that self-cleans the inside of the slit-shaped gap , The step of dehydrating the separated liquid and the step of returning the separated liquid to the fermenter are combined to determine whether the fermentation of the fermented liquid in the fermenter, which is obtained from the state of the solid waste remaining on the filtration surface, is complete. It relates to a methane fermentation method that switches to either one based on the determination result of whether it is on the way .

According to the methane fermentation apparatus and the methane fermentation method according to the present invention, when producing biogas using solid waste, it becomes easy to manage the concentration of unsuitable floating substances in the fermentation liquid, and the maintenance of the methane fermentation apparatus. Easier to manage.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the structure of an example of the methane fermentation system containing the methane fermentation apparatus which concerns on this invention. FIG. 2 is a schematic diagram of an example of a separation device that removes floating unsuitable matter. FIG. 3 is a schematic diagram of another example of a separation device that removes floating unsuitable matter. 1 is a block diagram showing the configuration of an example of a pretreatment device for separating raw material waste from solid waste; FIG.

In the methane fermentation apparatus according to the embodiment of the present invention, solid waste is introduced into the fermenter as a raw material. In the fermenter, hydrolysis, acid fermentation and methane fermentation of fermentable substances in the solid waste proceed to produce biogas. That is, the methane fermentation apparatus is equipped with a fermenter that accommodates a fermentation liquor that generates biogas and that advances hydrolysis, acid fermentation, and methane fermentation of a fermentation-suitable substance.

The methane fermentation apparatus according to the present embodiment can enable construction of a methane fermentation system that does not include a solubilization tank for promoting acid fermentation of a fermentable substance. In the wet methane fermentation system, a solubilization tank is usually installed to store the sorted garbage and to promote hydrolysis and acid fermentation of the garbage. On the other hand, in the methane fermentation apparatus according to this embodiment, solid waste is introduced into the fermentation tank as a raw material. Solid waste is supplied as raw material waste from which a portion of unfermentable substances have been removed in advance. The raw material waste is mixed with the fermented liquor partially removed from the fermenter. The fluid containing raw material waste thus obtained is introduced into the methane fermenter.

Solid waste contains fermentables and may contain some unfermentables. Solid waste may be, for example, general waste generated by a household. Materials unsuitable for fermentation contained in general waste are sufficiently sorted in advance.
Hereinafter, solid wastes used as raw materials for methane fermentation are referred to as raw material wastes.

A fermented liquid is a liquid obtained through hydrolysis and acid fermentation of a fermentable material, followed by digestive decomposition by fungal cells that promote methane fermentation.

Fermentable matter refers to organic matter that can be decomposed by methane fermentation via hydrolysis and acid fermentation (ie, solubilization). Materials suitable for fermentation include, but are not particularly limited to, raw garbage, waste paper, and biodegradable plastics.

Substances unsuitable for fermentation are materials unsuitable for solubilization, and examples thereof include metals, plastics, minerals, and shellfish. Inappropriate substances for fermentation may be mixed in raw material waste even if they are sufficiently separated in advance. Such substances unsuitable for fermentation are appropriately removed from the apparatus system by separation.

A methane fermentation apparatus according to an embodiment of the present invention includes a fermenter containing a fermentation liquid for generating biogas, a separation device for removing fermentation unsuitable substances floating in the fermentation liquid taken out from the fermenter, and a separation device. and a dehydration route for supplying the separated liquid to the dehydrator. Fermented liquid taken out of the fermenter is sent to a separator through a withdrawal route. The separation device removes unsuitable substances for fermentation (floating unsuitable substances) floating in the fermentation liquid from the fermentation liquid supplied from the extraction route. The separated liquid from which floating impurities have been removed by the separation device is sent to the dehydration device through the dehydration route.

The unsuitable floating matter refers to organic matter that is difficult to digest and decompose even in a fermenter. When the purpose is to remove floating unsuitable substances, as a general rule, no flocculant or the like is added to the fermentation liquid sent to the separator.

The separation device has a filtering surface for filtering the fermented liquid, a filtering part having a plurality of slit-shaped gaps opening to the filtering surface, and a gap for conveying unsuitable substances deposited on the filtering surface by moving in the slit-shaped gaps. and a self-cleaning section.

The methane fermentation method according to the embodiment of the present invention is a method that can be performed, for example, by using the above-described methane fermentation apparatus, and includes (i) hydrolysis of a fermented material in a fermenter containing a fermentation liquid, acid fermentation and (ii) removing the fermented liquid from the fermenter and removing the floating impurities; and (iii) dehydrating the separated liquid from which the floating impurities have been removed. and a step of performing.

The step of removing floating undesired matter includes introducing the fermented liquid into a filtration surface having a plurality of slit-shaped gaps open, draining the fermented liquid through the plurality of slit-shaped gaps, and depositing the unsuitable matter on the filtration surface. and a step of recovering unsuitable matter deposited on the filtering surface by a gap self-cleaning part that self-cleans the inside of the slit-shaped gap. The gap self-cleaning part may have a function of moving within the slit-shaped gap and moving unsuitable matter deposited on the filtering surface to a predetermined position.

Solid waste includes a variety of fermentable and unfermentable materials. The high specific gravity material settles to the bottom of the fermenter. Light specific gravity matters move to the liquid surface and stay as scum (SCUM). Therefore, unsuitable fermentation substances with high specific gravity and low specific gravity can be removed from the fermenter relatively easily. On the other hand, it is difficult to remove floating unsuitable substances in the fermentation broth because they do not stay at specific sites in the fermentation tank. However, when solid waste containing organic matter is used as raw material waste, the amount of floating unsuitable matter in the fermentation liquid tends to increase. Floating contaminants can cause clogging failures in piping and equipment, increasing maintenance frequency.

It is also difficult to separate the floating unsuitables from the fermentable materials, and if the floating unsuitables are removed forcibly, the fermentable unsuitables may also be removed together. As a result, the amount of biogas generated is reduced. In addition, when trying to filter the fermented liquid using a general mesh-type screen, not only the fermented material is removed together, but also the fine fibers contained in the fermented liquid easily cause clogging of the screen. . Therefore, stable operation of the methane fermentation apparatus becomes difficult.

On the other hand, the separation device described above is very effective in removing floating impurities. In addition, unlike a mesh-type screen, the separation device does not excessively remove fermentable substances, and clogging due to fine fibers is less likely to occur.

The filtering section has, for example, a plurality of band-shaped sections extending along the conveying direction of the unsuitable matter. A slit-like gap is formed between adjacent strips. A filtration surface for filtering the fermented liquid is formed by one end surface along the longitudinal direction of the plurality of band-shaped portions and the slit-shaped gap. Fine fibers and the like among fermentation-suitable materials that are less likely to clog pipes and equipment pass through the slit-like gap together with the fermentation liquid. On the other hand, relatively large fermentation unsuitables deposit on the filtration surface, which can cause obstruction of piping and equipment. A member generally called a bar screen, for example, can be used in the filtering section.

The gap self-cleaning unit includes, for example, a plurality of rotating shafts arranged below the filtering unit, and a plurality of disc-shaped rotating bodies fixed to the plurality of rotating shafts and arranged at intervals along the axial direction. Equipped with The plurality of rotating shafts are supported so as to intersect the conveying direction of the unfermentable substances, and are arranged at intervals along the conveying direction. A plurality of discs move vertically in accordance with the rotation of the rotating shaft in each of the slit-like gaps, thereby applying power to the undesired substances deposited on the filtering surface. The fermentation unsuitable material moves along the conveying direction, for example, falls from the end of the filtering section into a predetermined container and is collected. Preferably, the filtering surface is configured to slope upward along the conveying direction.

The methane fermentation apparatus mixes the separated liquid or the fermented liquid supplied from the withdrawal route with waste containing fermentable materials supplied from the outside to obtain a fluid, and also removes unfermentable materials derived from the waste. A mixing section for separating at least a portion and an input route for sending the fluid from the mixing section to the fermenter may be further provided.

The separation device can also be used to check the state of decomposition of the fermentable material in the fermenter. The amount of raw material waste introduced can be controlled during normal operation or at the start-up of fermentation, depending on the state of decomposition of fermentation-suitable substances. Specifically, a partial sampling of the fermented liquid from the fermenter may be sent to a separation device to check the state of the solid waste remaining on the filtration surface. All or part of the fermentable material remaining on the filtration surface may be mixed again with the separated liquid obtained at this time, and the mixture may be re-introduced into the fermenter.

The methane fermentation apparatus may further comprise a recovery route for returning the separated liquid to the fermenter. In this case, the methane fermentation apparatus may be configured so that the supply of the separated liquid to the dehydration route and the supply to the recovery route can be switched at any timing. That is, the methane fermentation apparatus may be configured such that the supply destination of the separated liquid can be switched between the dehydration route and the recovery route.

That is, a methane fermentation method according to another embodiment of the present invention includes a fermenter containing a fermentation liquid that generates biogas, and a separation device that removes unfermented substances floating in the fermentation liquid taken out from the fermenter. , a dehydrator for dehydrating the separated liquid from which unfermented substances have been removed by the separator, a dehydration route for supplying the separated liquid to the dehydrator, and a recovery route for returning the separated liquid to the fermenter, It includes an aspect in which the supply destination can be switched between the dehydration route and the recovery route.

For example, when the fermentation of the fermented liquid in the fermenter is completed, the separated liquid is supplied to the dehydration route, and the fermented liquid is dehydrated and discarded. When the fermented liquid in the fermenter is in the middle of fermentation, the supply destination of the separated liquid can be used as a recovery route to remove unsuitable substances from the fermented liquid and to check the fermentation state. This facilitates management of the state of the fermented liquid in the fermenter and increases the degree of freedom in system operation. Such switching of the supply destination can be performed by a predetermined device such as a valve.

Hereinafter, embodiments of the present invention will be further described with reference to the drawings. However, the following embodiments do not limit the present invention.

FIG. 1 shows an example configuration of a methane fermentation system 10 including a methane fermentation apparatus 100 according to the present invention. The methane fermentation apparatus 100 includes a fermenter 110 containing a fermented liquid L, a mixing section 120 for mixing the fermented liquid L extracted from the fermenter 110 and raw material waste C to obtain a fluid S, and a fermenter 110. A first withdrawal route R11 for sending the fermentation liquid L taken out from the fermenter 120 to the mixing unit 120, and an input route R2 for sending the fluid S from the mixing unit 120 to the fermenter 110.

In addition, the methane fermentation apparatus 100 includes a second withdrawal route R12 for sending the fermentation liquid L extracted from the fermentation tank 110 to the separation apparatus 300, a separation apparatus 300 for removing floating undesired substances from the fermentation liquid L, and a separation apparatus 300 and a dewatering device 180 for dewatering the separated liquid FL.

Furthermore, the methane fermentation apparatus 100 has a circulation route R3 for withdrawing the fermented liquid L from the bottom of the fermenter 110 and then returning it upward. A discharge port 114 for extracting the fermented liquid L is provided below the fermenter 110 . The fermented liquid L is pulled out from the discharge port 114 by the driving force of the first pump (Hydrostar) P1 provided on the circulation route R3 and sent upward. By circulating the fermentation liquid L, the fermentation of the fermentable substances in the fermenter 110 is promoted, and the separation and recovery of the unfermentable substances are facilitated.

The downstream end of the circulation route R3 is bifurcated, and each of the two branches has an upper outlet 111 and a submerged outlet 112 for discharging the fermentation liquid L that has passed through the circulation route R3 into the fermentation tank 110. . Valves V1 and V2 are provided upstream of the upper outlet 111 and upstream of the submerged outlet 112, respectively.

The fermenter 110 is a vertical cylindrical container, and has airtightness so that the inside is maintained in an anaerobic atmosphere. The fermenter 110 may have dead space for unfermentables to settle. The high specific gravity substances that settle in the dead space are appropriately discharged to the outside from the bottom outlet 113 and removed. Bottom outlet 113 preferably has, for example, a scraper or table feeder mechanism.

In FIG. 1, the upstream side of the first extraction route R11 and the second extraction route R12 and the upstream side of the circulation route R3 are configured by common piping. The fermented liquid L is drawn from below the fermenter 110 by the driving force of the first pump P1 provided on the circulation route R3. The first withdrawal route R11 and the second withdrawal route R12 branch from the circulation route R3 at the first branch portion T1.

By opening the valve V3 provided in the fork and the valve V10 provided in the first withdrawal route R11 and closing the valve 11, the fermented liquid L is sent to the mixing section 120 through the first withdrawal route R11. At this time, by checking the state of the fermented liquid L bypass-transferred through the first withdrawal route R11, the decomposition state of the fermentable material in the fermenter 110 can be grasped.

Also, by opening the valve V3 and the valve V11 provided on the second withdrawal route R12, the fermented liquid L is sent to the separator 300 through the second withdrawal route R12. When the fermentation liquid (separated liquid FL) from which the floating undesired substances have been removed by the separation device 300 is present, the valve V5 in front of the mixing section 120 is opened, the valve V7 in front of the storage tank 170 is closed, and the mixing section 120. In this case, the separation device 300 can be used to check the state of digestion and decomposition of the fermentable material in the fermenter 110 .

Although it is difficult to visually confirm the inside of the fermenter 110, according to the mixing unit 120 or the separation device 300, it is possible to clearly grasp the digestion and decomposition state of the appropriate substances in the fermentation liquid, so the raw material waste It becomes easy to control the amount of supply of The separated liquid FL sent to the mixing section 120 can be reused together with the solids separated by the separating device 300 .

Separated liquid FL from which the floating undesired substances have been removed by the separation device 300 is collected in the storage tank 170 by closing the valve V5 in front of the mixing unit 120 and opening the valve V7 in front of the storage tank 170 at another time. be done. After that, the separated liquid FL is sent to the recovery route R5 or the dehydration route R6 at an arbitrary timing. The valve V9 is closed, the valve V8 is opened, and the separated liquid FL passed through the recovery route R5 is returned to the fermenter 110 by the driving force of the pump P3. The valve V8 is closed, the valve V9 is opened, and the separated liquid FL passed through the dehydration route R6 is sent to the dehydrator 180 by the driving force of the pump P3.

When the separated liquid FL is discarded by passing through the dewatering route R6, the separated liquid FL in the storage tank 170 is mixed with a coagulant, and the separated liquid FL containing the coagulant is sent to the dehydrator 180 to separate the dehydrated sludge and the dewatered sludge. The filtrate can be separated and discarded.

The mixing unit 120 mixes the raw material waste C and the fermentation broth L to give the raw material waste C fluidity and improve the dispersibility of the raw material waste C in the fermentation tank 110. . The residence time of the fluid in the mixing section 120 may be less than 0.5 days, such as 3 hours or less, or 2 hours or less, or even 0.5 hours or less. The raw material waste C is mixed and stirred with the fermentation liquid L and/or the separation liquid FL in the mixing unit 120, dispersed in a liquid state or a slurry state, and then introduced or transferred to the fermentation tank 110, which is kept airtight. Hydrolysis and acid fermentation of fermentables in the stream proceed in a fermenter where methane fermentation takes place.

The fluid S in the mixing section 120 is pulled out by the driving force of the second pump P2. Fluid S passes through input route R2 and is returned to fermentor 110 via valve V4. The supply route R2 may be branched on the upstream side of the valve V4, and the branched route may be merged with the circulation route R3 at the second branch portion T2. By opening the valve V6 on the upstream side of the second branch T2, the fluid S joins the circulation route R3 and is discharged from the upper outlet 111 and/or the submerged outlet 112 into the fermentation tank 110. At this time, the circulation of the fermentation liquid L within the fermenter 110 and the supply of the fluid S to the fermenter 110 may be performed in parallel. Such parallel operations may occur continuously over a period of time. The second branch portion T2 may be provided on the downstream side of the circulation route from the first branch portion T1.

When the methane fermentation is performed in batch mode, after the fluid S is introduced into the fermentation tank 110, the valve V3 may be closed until the fermentation is completed.

Methane fermentation system 100 may have a steam inlet that introduces steam into fermentor 110 . Steam is introduced into the fermenter 110 as a heat source for maintaining the interior of the fermenter 110 within an appropriate temperature range of, for example, 50-60°C. Steam also functions as dilution water for controlling the ammonia concentration or organic acid concentration of the fermentation broth L. When solid waste such as waste paper is used, the ammonia concentration in the fermentation liquid is less likely to increase. Therefore, there is no need to add diluent water from the outside, and the amount of fermented liquid in the fermenter is maintained within a proper range for a relatively long period of time. As a method for maintaining the inside of the fermenter 110 within the proper temperature range, a method other than heating with steam may be used.

Fermentable material sent to the fermenter 110 is sequentially hydrolyzed in the limited space within the fermenter 110 . Apart from the fermenter 110, it is not necessary to install a solubilization tank for proceeding with hydrolysis and acid fermentation of the fermentable material. In the methane fermentation apparatus 100, the space required for solubilizing the fermentable material is greatly reduced. Along with this, the number of required equipment and energy consumption are also reduced. As described above, the cost required for constructing and operating the methane fermentation system 10 is reduced.

The amount of fermentation suitable material introduced into the fermenter 110 affects the amount of organic acid in the fermenter 110 . The amount of fermentation suitable material in the fermenter 110 can be adjusted by controlling the amount of the fluid S sent from the mixing section 120 to the fermenter 110 . The organic acid concentration of the fermented liquid L in the fermenter 110 is maintained within an appropriate range by appropriately controlling the amount of the fluid S sent from the mixing section 120 to the fermenter 110 .

Since solid waste containing organic matter containing air is introduced into the mixing section 120, it is difficult to maintain the inside of the mixing section 120 in a good anaerobic atmosphere. However, if the volume of the mixing section 120 is much smaller than the volume of the fermenter 110, the amount of fermented liquid sent to the mixing section 120 and coming into contact with air is limited. If the volume of the mixing section 120 is set to 20% or less of the volume of the fermenter 110, excess fermented liquid L will not be extracted from the fermenter 110, and the fermentation amount will be less likely to decrease. The volume of the mixing section 120 is preferably 20% or less, more preferably 10% or less, of the volume of the fermentation tank 110, for example.

When the fluid S is obtained in the mixing unit 120, the amount of the raw material waste C mixed with 100 parts by mass of the fermentation liquid is preferably 10 to 50 parts by mass, more preferably 10 to 30 parts by mass. Depending on the properties, physical properties, and moisture content of the raw material waste C, it is not necessary to add water from the outside for the purpose of increasing fluidity. By obtaining the fluid S having sufficient fluidity, the rate of occurrence of various problems such as clogging of pipes is reduced. In order to further suppress the clogging of the piping, it is preferable to take measures to increase the flow velocity and to set the piping gradient in the horizontal direction to -45° to +45°. In addition, it is preferable to provide an optional pipe (trap pipe section) for retaining deposits in the pipe.

The fermenter 110 basically has a structure in which the interior is blocked from contact with the atmosphere. Sunlight irradiation to the fermented liquid L also needs to be suppressed. On the other hand, it is also necessary to grasp the internal conditions of the fermenter 110, that is, the generation of scum (SCUM) in the fermenter 110, the concentration of contaminants in the fermentation liquid L, the pH value of the fermentation liquid L, and the like. The mixing unit 120 also functions as a monitoring unit for the fermentation liquid L for grasping the situation.

FIG. 2 shows the configuration of a rotary disc concentrator, which is an example of the separation device 300 . FIG. 3A schematically shows a bird's-eye view of the relationship between the filtering unit 310 and the clearance self-cleaning unit 320 provided in the separation device 300. As shown in FIG. The gap self-cleaning unit 320 includes a plurality of rotating shafts 323 and a plurality of disk-shaped rotating bodies 321 fixed to the rotating shafts 323 and arranged at intervals along the axial direction thereof. FIG. 4B schematically shows the relationship between the filtering section 310 and the gap self-cleaning section 320 as a cross-sectional view along the rotating shaft 323. As shown in FIG.

Filtration section 310 is formed of a plurality of band-shaped portions 315 extending along the conveying direction of unfermented substances, and slit-shaped gaps 312G are formed between adjacent band-shaped portions 315 . The upper end surfaces of the plurality of band-shaped portions 315 form a filtering surface 311S together with the slit-shaped gaps 312G. In FIG. 2(b), the level of the filtering surface 311S is indicated by a dashed line. The plurality of rotating shafts 323 are pivotally supported below the plurality of belt-shaped portions 315 so as to intersect the longitudinal direction of the belt-shaped portions 315 . A plurality of disk-shaped rotating bodies 321 move up and down in accordance with the rotation of the rotating shaft 323 within the slit-shaped gap 312G.

The disk-shaped rotating body 321 is fixed to the rotating shaft 323 at its eccentric position. The disc-shaped rotors 321 adjacent to each other in the axial direction differ in phase by 180 degrees for each disc 321 in vertical motion accompanying rotation of the rotating shaft 323 . Between the adjacent rotating shafts 323, the vertical motion phases of the adjacent disk-shaped rotating bodies 321 are the same. Since all the rotating shafts 323 rotate synchronously in the same direction at the same speed, the states shown on the left and right in the schematic diagram are alternately realized each time the rotating shaft 323 rotates half a turn.

It is generally difficult to separate floating unsuitable substances from fermentation suitable substances in the process of decomposition, but according to the separation device 300, undissolved unsuitable substances that maintain a relatively large size are selected. can be removed. Fermented liquid L is poured from above the filtering section 310 of the separation device 300 toward the inlet side end of the filtering surface 311S. The inlet side end is the rear end in the rotation direction of the gap self-cleaning section 320 . Floating unsuitable matter having a relatively large size does not pass through the gap between the filtering section 310 and the gap self-cleaning section 320 and is trapped on the filtering surface 311S. The trapped unsuitable matter moves forward in the rotational direction on the filtering surface 311S due to the rotation of the gap self-cleaning section 320, and is conveyed toward a predetermined outlet. The separated unsuitable matter is collected as residual sludge RC.

In the separation device 300, since the gap self-cleaning section 320 is constantly moving up and down, the gap between the filtering section 310 and the gap self-cleaning section 320 is less likely to be blocked. On the other hand, if a mesh type screen is used, for example, the mesh is easily clogged.

The fermented liquid L containing small-sized fermentable substances in the middle of decomposition passes through the gap between the gap self-cleaning section 320 and the filtering section 310 and is collected in the storage tank 170 or the mixture 120 as the separated liquid FL.

FIG. 3 shows an example configuration of another separation device 300A.
The filtration unit 310A included in the separation device 300A has substantially the same configuration as the separation device 300 in FIG. A slit-like gap 312AG is formed between the portions 315A. The upper end surfaces of the plurality of band-shaped portions 315A form a filtration surface 311AS together with the slit-shaped gaps 312AG.

The gap self-cleaning part 320A provided in the separation device 300A has a substantially comb-like shape instead of a rotating body. The gap self-cleaning part 320A includes a plurality of claws 321A that are inserted into the respective slit-shaped gaps 312AG from one direction, and a strut 322A that supports the claws 321A. The support pillar 322A is pivotally supported so as to intersect the conveying direction of the unfermentable substances, and moves along the conveying direction as shown in order from FIG. 3(a) to FIG. 3(b). After that, as shown in FIG. 3(c), it has a mechanism to move in the reverse direction under the filtering section 310A and return to the original position. By repeating this revolving motion, unfermentable substances deposited on the filtration surface are scraped off by the plurality of claw portions 321A and collected as residual sludge RC behind the filtration portion 310A.

FIG. 4 shows the configuration of an example of a pretreatment device for sorting raw material waste C. As shown in FIG. The pretreatment device 200 includes a first conveying device 210 that transfers solid waste C1 introduced from the outside, a crusher 220 that crushes the solid waste C1 supplied from the first conveying device 210, and a crusher 220. A second conveying device 230 for transferring the crushed crushed waste C2 and a separator 240 are provided.

The first conveying device 210 is, for example, a belt conveyor, and supplies the solid waste C1 to the crusher 220 after equalizing the amount of the solid waste C1 continuously introduced into the system within a certain period of time. The crusher 220 is, for example, a twin-screw crusher, and crushes solid waste containing large organic substances that are not suitable for hydrolysis into small pieces, and performs pre-shredding treatment so that it has a size suitable for processing in the sorting machine 240. do. The second conveying device 230 is, for example, a belt conveyor, and supplies the crushed waste C2 including crushed solid waste to the sorting machine 240 after equalizing the amount of crushed waste C2 supplied within a certain period of time.

The sorting machine 240 may have any configuration, but has a cylindrical rotating drum made of a perforated sheet such as a mesh having a plurality of holes or punching metal. Crushed waste C2 is introduced into the rotating drum. Among the crushed waste C2, solids smaller than the pore size of the perforated sheet are discharged outside the drum due to the wind force and centrifugal force flowing through the drum. The discharged solids are collected as raw material waste C containing the correct content of fermentable material. Low specific gravity materials such as cloth and plastic sheets and high specific gravity materials such as metals are collected from the rotating drum as NC unsuitable for fermentation.

The above-described embodiment is one aspect of the present invention, and the present invention is not limited by the description, and the specific configuration and control mode of each part can be appropriately changed and designed within the scope of the effects of the present invention. It goes without saying that

10: Methane fermentation system 100: Methane fermentation device 110: Fermentation tank 111: Top outlet 112: Submersible outlet 113: Bottom outlet 114: Discharge port 120: Mixing section 121: Mixing vessel 122: Stirring blade 170: Storage tank 180 : Dewatering device 200: Pretreatment device 210: First conveying device 220: Crusher 230: Second conveying device 240: Sorting machine 300: Separating device 310, 310A: Filtration unit 311S, 311AS: Filtration surface 312G, 312AG: Slit shape Gap 315, 315A: Strip-shaped part 320, 320A: Gap self-cleaning part 321: Disc-shaped rotating body 321A: Claw part 322A: Support part C1: Solid waste C2: Crushed waste C: Raw material waste NC: Fermentation unsuitable material L: Fermentation liquid FL: separation liquid (filtrate)
S: Fluid RC: Residual sludge P1-P3: 1st-3rd pumps R11: 1st withdrawal route R12: 2nd withdrawal route R2: Input route R3: Circulation route R5: Recovery route R6: Dehydration route V1-V11: Valve T1: First branch T2: Second branch

Claims (6)

a fermenter containing a fermented liquid for generating biogas;
a separation device for removing substances unsuitable for fermentation floating in the fermented liquid taken out from the fermenter;
a dehydration device for dehydrating the separated liquid from which the substances unsuitable for fermentation have been removed by the separation device;
a dehydration route that supplies the separated liquid to the dehydrator;
a recovery route for returning the separated liquid to the fermenter;
a switching device for switching the supply destination of the separated liquid between the dehydration route and the recovery route;
and
The separation device is
a filtration unit having a filtration surface for filtering the fermented liquid and having a plurality of slit-like gaps opening to the filtration surface;
a gap self-cleaning unit that moves in the slit-like gap and conveys the unsuitable fermentation material deposited on the filtration surface;
and
The switching device is
The dehydration route and the A methane fermentation apparatus configured to be switchable to either recovery route . 2. The filtering unit according to claim 1, wherein said filtering unit has a plurality of band-shaped portions arranged to extend along the conveying direction of said unfermentable substances, and said slit-shaped gaps are formed between adjacent said band-shaped portions. methane fermentation equipment. The gap self-cleaning section includes a plurality of rotating shafts arranged below the filtering section, and a plurality of discs fixed to the plurality of rotating shafts and arranged at intervals along the axial direction of the rotating shafts. and a rotating body,
The plurality of rotating shafts are axially supported so as to intersect with the conveying direction of the unsuitable substances for fermentation, and are arranged at intervals along the conveying direction of the unsuitable substances for fermentation,
3. The methane fermentation apparatus according to claim 1, wherein said plurality of disc-shaped rotors move up and down in said slit-shaped gap as said rotating shaft rotates. A mixing unit that mixes the separated liquid or the fermentation liquid with a waste material that includes a fermentation suitable material supplied from the outside to obtain a fluid material, and separates at least a part of the fermentation unsuitable material derived from the waste material. and,
The methane fermentation apparatus according to any one of claims 1 to 3, further comprising an input route for sending said fluid from said mixing section to said fermenter. (i) a step of hydrolyzing, acid-fermenting, and methane-fermenting a substance suitable for fermentation in a fermenter containing a fermented liquid to generate biogas;
(ii) removing the fermentation liquid from the fermenter and removing substances unsuitable for fermentation floating in the fermentation liquid;
(iii) a step of dehydrating the separated liquid from which the unsuitable substances for fermentation have been removed;
(iv) returning the separated liquid to the fermenter;
and
The step of removing unsuitable substances for fermentation includes:
a step of introducing the fermented liquid into a filtration surface in which a plurality of slit-shaped gaps are open, draining the fermentation liquid through the plurality of slit-shaped gaps, and depositing the fermentation unsuitable substances on the filtration surface;
a step of recovering the fermentation-improper matter deposited on the filtering surface by a gap self-cleaning part that self-cleans the inside of the slit-shaped gap ,
dehydrating the separated liquid and returning the separated liquid to the fermenter,
A methane fermentation method, wherein switching is performed based on a determination result as to whether the fermentation of the fermented liquid in the fermenter has been completed or is in the middle of fermentation, which is obtained from the state of the solid waste remaining on the filtration surface. sending the separated liquid or the fermented liquid taken out from the fermenter to a mixing section;
A step of mixing the separation liquid or the fermentation liquid with waste containing fermentation-suitable materials in the mixing unit to obtain a fluid and separating at least a part of fermentation-unsuitable materials derived from the waste;
The methane fermentation method according to claim 5, further comprising the step of sending the fluid from the mixing section to the fermenter.

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