JP7060457B2 - Post-treatment method and equipment for methane fermented liquid - Google Patents

Description

The present invention relates to a post-treatment method and an apparatus for a methane fermentation broth, and more particularly to a post-treatment method and an apparatus for a fermentation broth generated after the methane fermentation treatment of biomass.

From the viewpoint of forming a sound material-cycle society, biomass S containing organic substances such as food waste, high-concentration organic wastewater, excess sludge, and livestock manure is anaerobically decomposed by microorganisms to generate biogas G as an energy source. A methane fermentation treatment technique has been put into practical use (see Patent Document 1 and Non-Patent Document 1). With reference to FIG. 4, the flow of a conventional methane fermentation plant will be described to the extent necessary for understanding the present invention. First, the biomass S to be treated is stored in the raw material tank 1, and after pretreatment such as foreign matter separation, crushing, and dilution as necessary, it is put into the methane fermentation tank (bioreactor) 2 by the raw material pump 1a to methane. It is used for fermentation processing.

The methane fermentation treatment (digestion process of organic matter) in the methane fermentation tank 2 is a complicated reaction process in which various organic substances such as proteins, fatty acids, and lipids are decomposed by the symbiosis of many microorganisms. In the stage, organic substances with large molecular weight are decomposed into low molecular weight alcohols, fatty acids, hydrogen, etc., in the second stage, fatty acids, etc. are oxidatively decomposed into acetic acid, and in the third stage, biogas G is finally generated from acetic acid, hydrogen, etc. Will be done. The illustrated example shows a wet methane fermentation tank 2 for treating biomass S having a relatively low solid matter concentration, but when treating biomass S having a relatively high solid matter concentration, a dry methane fermentation tank is used. It is also possible.

In the methane fermentation tank 2, biogas G is generated, and after the fermentation treatment, a fermentation broth or a fermentation residue (hereinafter, both are collectively referred to as a fermentation broth) F is generated. The fermented liquid F can be recycled as compost (compost), soil conditioner, etc. by post-treatment, or can be detoxified by appropriate wastewater treatment or the like. In the post-treatment step of the illustrated example, first, the fermented liquid F generated in the methane fermentation treatment is sent to the fermented liquid adjusting tank 20 via the inflow path 2a and temporarily stored, and the fermented liquid F in the adjusting tank 20 is solidified by the fermented liquid pump 29. It is sent to a liquid separation device (for example, a dehydrator or the like) 30 to separate the solid phase and the liquid phase. At the time of solid-liquid separation, the flocculant may be added from the flocculant tank 31 by the flocculant pump 31a as shown in the illustrated example. The liquid phase after solid-liquid separation can be temporarily stored in the filtrate tank 32 and sent to a wastewater treatment device (for example, an active sludge treatment device) 34 by a filtrate pump 33 to be detoxified to a predetermined environmental standard value, and detoxified. The fermented liquid F can be discharged into an environment such as a sewer by a drainage pump 35, for example. In addition, the solid phase after solid-liquid separation can be recycled by putting it in an appropriate composting device.

Japanese Unexamined Patent Publication No. 2000-167523 Japanese Unexamined Patent Publication No. 2004-195453

"Biomass Technology Handbook-Knowledge for Introduction and Commercialization-Chapter 3 Methane Fermentation" edited by New Energy Foundation, Ohmsha Co., Ltd., October 25, 2008, pp. 206-447 Incorporated Administrative Agency Agricultural and Food Industry Technology Research Organization Press Release "Development of Phosphorus Reuse Technology Generated in Pig Farming" Published June 18, 2008, Internet <http://www. naro. affrc. go. jp / publicity_report / press / laboratory / nigs / 012887. html> Kazuaki Shimamura et al. "Verification of high-efficiency phosphorus recovery method using a two-tank fluidized bed MAP reactor" Ebara Times No. 206, published in 2005, Internet <https: // www. evara. co. jp / about / technologies / abstract / datail / __icsFiles / afieldfile / 2016/04/25/206_P23_1. pdf>

However, in the conventional methane fermentation treatment, the crystallization component dissolved in the fermentation broth F after the methane fermentation treatment is transferred from the fermenter storage tank 20 surrounded by the dotted line in FIG. 4 to the filtrate pump 33. There is a problem that the crystals that are deposited in the process) may cause blockage inside the treatment tank / piping and affect the operation of the plant. The main crystals that precipitate are when the biomass S to be treated contains crystallization components such as phosphate ion ( ^{PO 4-3-} ₎ , ammonium ion (NH ₄ ⁺ ), and magnesium ion (Mg ²⁺ ). Magnesium ammonium phosphate (MgNH ₄ PO ₄ ; hereinafter referred to as MAP) formed by combining them.

The treatment target of methane fermentation is a complicated buffer solution containing many buffers, and the precipitation of crystals in the post-treatment step occurs due to the overlap of multiple conditions (pressure, temperature, etc.), so the precipitation of crystals such as MAP It is difficult to simply formulate the reaction. However, in the raw material tank 1 of FIG. 4, the acidity is usually maintained at about 4 to 5 by the lactic acid fermentation reaction, and in the methane fermentation tank 2, the pH is usually maintained at about 7.5 by the decomposition reaction into the bioiogas G described above. On the other hand, in the fermented liquid F after being discharged from the methane fermentation tank 2, the dissolved carbon dioxide gas (H ₂ CO ₃ ) is gradually released as carbon dioxide (CO ₂ ). In the post-treatment step, the pH rises to usually be 8 or higher. It is considered that one of the causes of the precipitation of crystals such as MAP in the post-treatment step is such an increase in the pH of the fermentation broth F of 8 or more (alkalination). That is, phosphate ions, ammonium ions, magnesium ions, etc. that form crystals such as MAP are crystallization components that precipitate due to an increase in pH (hereinafter, may be referred to as high pH crystallization components).

In the conventional methane fermentation plant of Biomass S containing high pH crystallization components, crystals such as MAP deposited in the post-treatment process do not lead to blockage of the treatment tank / piping, so that they are regularly or as needed. Cleaning the interior is essential. However, once the operation of the methane fermentation tank 2 is stopped, it takes a long time to restart, so it may be required to clean the post-treatment process without stopping the operation of the methane fermentation tank 2, and the post-treatment process can be performed in a short time. There is a need to develop a technology that can be cleaned without hassle.

The present inventor focused on precipitating high pH crystallization components intensively and efficiently in the pretreatment stage of the post-treatment step of methane fermentation treatment. For example, in the treatment of high-concentration organic wastewater (pig house sewage) generated in the pig farming industry, a technique for recovering phosphoric acid contained in the organic wastewater as MAP has been developed (Patent Document 2, Non-Patent Document 2 to 2). 3). If such a crystal recovery technique can be applied to the post-treatment step of the methane fermentation treatment and the high pH crystallization component can be intensively and efficiently precipitated in the pre-treatment step of the post-treatment step, the post-treatment step of the post-treatment step can be performed. It is expected that the precipitation of crystals in the above process will be kept small and the cleaning work of the entire post-treatment process will be simplified.

Therefore, an object of the present invention is to provide a post-treatment method and an apparatus for a methane fermented liquid that can simplify the cleaning of the post-treatment step.

With reference to the example of FIG. 1 (B) , the post-treatment method of the methane fermentation liquid according to the present invention is a flow of the fermentation liquid adjusting tank 20 in which the fermentation liquid F after the methane fermentation treatment of the biomass S is taken in and temporarily retained. A bottomed chamber 11 (see also FIG. 1 (A)) is provided inside the inlet 21 by partitioning from the surroundings , and the bottomed chamber 11 is exposed to air to provide a high pH crystallizing component (for example, phosphate ion, etc.) in the fermented liquid F. Ammonium ions (ammonium ions, magnesium ions) are precipitated by increasing the pH, and at least a part of the precipitated crystals (for example, MAP) being exposed is attached to the metal frame net 17 which is replaceably settled in the bottomed chamber 11 to precipitate the crystals. The subsequent fermented liquid F is overflowed from the bottomed chamber 11 to the fermented liquid adjusting tank 20 and temporarily retained, and is exposed to air in the fermented liquid adjusting tank 20 to make the unprecipitated high-pH crystallizing component in the fermented liquid F pH. After precipitating by ascending, the fermented liquid F after crystal precipitation is sent to a subsequent post-treatment step.

Further, referring to the embodiment of FIG. 1 (B) , the post-treatment apparatus for the methane fermented liquid according to the present invention takes in the fermented liquid F after the methane fermentation treatment of the biomass S and temporarily retains the fermented liquid adjusting tank 20. A bottomed chamber 11 (see also FIG. 1 (A)) provided inside the inflow port 21 of the fermented liquid adjusting tank 20 so as to be partitioned from the surroundings . An aeration device 15 that precipitates components (for example, phosphate ion, ammonium ion, magnesium ion) by increasing the pH, a metal frame net 17 that is interchangeably set above the aeration device 15 in the bottomed chamber 11, and crystal precipitation. The unprecipitated high-pH crystallization component in the fermented liquid F is aerated in the overflow dam 14 for overflowing the subsequent fermented liquid F from the bottomed chamber 11 to the fermented liquid adjusting tank 20 and in the fermented liquid adjusting tank 20. It is provided with an aeration device 26 for precipitating by increasing the pH .

In a desirable embodiment, as shown in FIG. 1 (B), the fermented liquid adjusting tank 20 is provided with an inclined bottom surface 23, and a precipitation crystal collecting groove 24 is formed at the lower end portion of the inclined bottom surface 23.

In a more desirable embodiment, as shown in FIG. 2B, a pair of fermented liquid adjusting tanks 20a and 20b with a bottomed chamber 11 are provided, and an inflow path 2a of the fermented liquid F after the methane fermentation treatment is provided in the bottomed chamber 11. A switching valve 40 connected to the inflow port 21 of any of the fermented liquid adjusting tanks 20a and 20b is provided.

The post-treatment method and apparatus for the methane fermentation liquid according to the present invention are bottomed by partitioning from the surroundings inside the inflow port 21 of the fermentation liquid adjustment tank 20 in which the fermentation liquid F after the methane fermentation treatment of the biomass S is taken in and temporarily retained. A chamber 11 is provided , and the high pH crystallizing component in the fermented liquid F is precipitated by increasing the pH by aerating from the aeration device 15 in the bottomed chamber 11, and a metal frame net is provided during the aeration in the bottomed chamber 11. 17 is replaceably submerged to adhere at least a part of the precipitated crystals (for example, MAP), and the fermented liquid F after crystal precipitation is overflowed from the bottomed chamber 11 to the fermented liquid adjusting tank 20 and temporarily retained, and the fermented liquid is temporarily retained. After aerating in the adjusting tank 20 to precipitate the unprecipitated high pH crystallization component in the fermented liquid F by increasing the pH, the fermented liquid F after the crystal precipitation is sent to the subsequent post-treatment step, which is advantageous as follows. It has a great effect.

(B) Cleaning work of the entire post-treatment step by intensively precipitating high pH crystallization components in the pre-treatment part of the post-treatment step of methane fermentation treatment and suppressing the precipitation of crystals in the post-treatment step of the post-treatment step to a small size. Can be simplified.
(B) Further, a bottomed chamber 11 for intensively precipitating high pH crystallization components is provided in the pretreatment stage of the post-treatment step of the methane fermentation treatment, and a metal frame for adhering the precipitated crystals inside the bottomed chamber 11. By providing the body net 17, it is possible to avoid blockage of the treatment tank / pipe in the post-treatment step by a simple short-time operation of replacing the bottomed chamber 11 or the frame body net 17 as needed.

(C) If a pair of bottomed chambers 11a and 11b are connected to the inflow path 2a of the fermentation broth F via a switching valve 40, the other bottomed chamber 11b can be cleaned when one bottomed chamber 11a is connected. The post-treatment step can be cleaned without stopping the inflow of the fermented liquid F.
(D) Further, by forming the bottomed chamber 11 as a bottomed small chamber 11 with an overflow weir 14 provided inside the inflow port 21 of the fermentation broth adjusting tank 20 from the surroundings, precipitation of high pH crystallization components is performed. Even if a separate space cannot be secured for the above, the high pH crystallization component can be intensively deposited by utilizing a part of the installation space of the conventional fermentation broth adjusting tank 20.

Hereinafter, embodiments and examples for carrying out the present invention will be described with reference to the accompanying drawings.
It is explanatory drawing of one Example of the post-treatment method of the methane fermentation liquid by this invention. It is explanatory drawing of another Example of the post-treatment method of the methane fermentation liquid by this invention. It is explanatory drawing of an example of an aeration apparatus 15 and a frame net 17 used in this invention. It is explanatory drawing of an example of the post-treatment method of the conventional methane fermentation liquid.

FIG. 1A shows an example of the post-treatment method for the methane fermented liquid according to the present invention. In the post-treatment method of the illustrated example, a precipitation tank 10 is provided between the above-mentioned methane fermentation tank 2 and the fermentation broth adjusting tank 20 with reference to FIG. The fermentation broth F immediately after the methane fermentation treatment generated in the methane fermentation tank 2 is taken into the precipitation tank 10, and the high pH crystallization components in the fermentation broth F are intensively precipitated in the precipitation tank 10, and the fermentation broth F after crystal precipitation F. Is overflowed into the fermented liquid adjusting tank 20 which is a subsequent post-treatment step. By providing the precipitation tank 10 immediately after the methane fermentation tank 2, the high pH crystallization component is intensively precipitated in the pretreatment portion of the post-treatment step, the precipitation of crystals in the post-stage portion of the post-treatment step is suppressed to a small size, and the post-treatment is performed. The cleaning work of the entire process can be simplified. The installation position of the precipitation tank 10 is not limited to immediately after the fermentation tank 2 as shown in the illustrated example, and can be appropriately selected in the pretreatment portion of the post-treatment step.

The precipitation tank 10 of the illustrated example can be exchanged between the bottomed chamber 11 that takes in the fermented liquid F and temporarily retains it, the aeration device 15 provided at the bottom of the bottomed chamber 11, and the fermented liquid F above the aeration device 15. It has a metal frame net 17 sunk in. The bottomed chamber 11 is provided with an intake port 12 connected to the fermented liquid inflow path 2a and an overflow weir 14 connected to the subsequent fermented liquid adjusting tank 20, and the taken-in fermented liquid F is retained for a predetermined time. Can be made to. The capacity of the bottomed chamber 11 can be designed so that the high pH crystallization component in the fermented liquid F stays for a sufficient time according to the intake flow rate of the fermented liquid F, but when it becomes large, it takes time and effort to clean it. Therefore, it is desirable to design in consideration of the labor and time of cleaning.

The aeration device 15 of the illustrated example replaces the carbon dioxide gas (H ₂ CO ₃ ) dissolved in the fermented liquid F with the aeration gas P and expels the high pH crystallization component (phosphate ion, ammonium) in the fermented liquid F. The pH in the bottomed chamber 11 is raised to the extent that ions (ions, magnesium ions) are deposited. An example of the aeration gas P is air, but nitrogen gas or other harmless gas can also be used. As described above, in the conventional methane fermentation treatment, crystals such as MAP are deposited in the post-treatment step in which the fermentation liquid F becomes pH 8 or higher. By raising the temperature to about 9 or more, intensive and efficient precipitation of high pH crystallization components can be promoted in the bottomed chamber 11.

The aeration device 15 can be installed at an appropriate position in the bottomed chamber 11, but is preferably provided at the bottom of the bottomed chamber 11. By providing the aeration device 15 at the bottom of the bottomed chamber 11, the whole fermented liquid F can be aerated while stirring, and the pH of the fermented liquid F inside the bottomed chamber 11 can be raised as a whole. Further, by agitating and aerating the fermented liquid F, the precipitation efficiency of the high pH crystallization component in the fermented liquid F is increased as a whole, and the unprecipitated high amount in the fermented liquid F overflowing from the bottomed chamber 11. The pH crystallization component can be reduced, and the precipitation of crystals in the subsequent post-treatment step can be suppressed to a small level. In the illustrated example, a single aeration device 15 is provided at the bottom of the bottomed chamber 11, but a plurality of aeration devices 15 can be provided at the bottom of the bottomed chamber 11.

In the metal frame net 17 of the illustrated example, crystals such as MAP deposited in the post-treatment step of the conventional methane fermentation treatment adhere to the metal surface of the treatment tank / pipe, and further precipitation progresses and grows on the surface. Therefore, it creates an environment in which crystals precipitate, adhere, and grow above the air diffuser (air bubbles) of the aeration device 15. The frame net 17 can be made of a material in which crystals are likely to adhere and grow depending on the methane fermentation plant to which it is applied, and can be made of, for example, aluminum, stainless steel, or copper. Further, it is desirable that the frame net 17 has a net shape or a cage shape through which the aeration can freely pass so that the contact area of the aeration device 15 with the air diffuser becomes large. Further, since the surface of the frame net 17 is more suitable for the adhesion and growth of crystals than the smooth surface, it is desirable to perform an appropriate rough surface treatment.

The metal frame net 17 of the illustrated example can be fixedly attached to the upper surface of the aeration device 15 with a fixing jig 17a, and can be removed from the aeration device 15 by releasing the fixing jig 17a as needed. .. Some of the crystals precipitated above the aeration device 15 do not adhere to the frame net 17, but some of them precipitate, but most of them adhere to the surface of the frame net 17. Therefore, the precipitated crystals can be recovered by a simple short-time operation of exchanging the frame net 17 as needed, and the cleaning work of the post-treatment step can be simplified. However, fixing the frame net 17 to the aeration device 15 is not essential to the present invention, and the frame net 17 independent of the aeration device 15 may be suspended and sunk above the aeration device 15, for example. (See the aeration device 26 in FIG. 1 (B)).

FIG. 3 shows an example of an aeration device 15 and a metal frame net 17 suitable for the present invention. The aeration device 15 shown in FIGS. 3A and 3B has a hollow tubular air supply tube 15c having an intake port 15a formed at one end and a sealing end 15b at the other end, and the peripheral wall of the air supply tube 15c. A large number of blowout holes 15d are formed in the air. By connecting an aeration hose 16 (see FIG. 1) to the intake port 15a and sending air, air diffusers (air bubbles) can be supplied from a large number of outlet holes 15d on the peripheral wall. Legs for stable seating on the bottom surface of the bottomed chamber 11 are formed on one side of the air supply tube 15c along the central axis direction, and a metal frame net is formed on the other side along the center axis direction. A mounting plate 15e for mounting the 17 is provided. If necessary, the aeration device 15 can include a plurality of air supply tubes 15c, and the pH of the fermented liquid F inside the bottomed chamber 11 can be raised as a whole.

3 (C) and 3 (D) show a state in which the metal frame net 17 is attached to the mounting plate 15e of the above-mentioned aeration device 15 and fixed by the fixing jig 17a. As shown in the illustrated example, the aeration device 15 is seated on the bottom surface of the bottomed chamber 11 in a state where the metal frame net 17 is fixed to the mounting plate 15e, so that the entire frame net 17 is dispersed by the aeration device 15. By intersecting with air (air bubbles), the submerged space of the frame net 17 can be made into an environment in which crystals are likely to precipitate, adhere, and grow. A plurality of aeration devices 15 and a frame net 17 can be provided at the bottom of the bottomed chamber 11, and by providing a plurality of aeration devices 15 and a frame net 17, the entire internal space of the bottomed chamber 11 can be provided. It is possible to create an environment in which crystals are likely to precipitate, adhere, and grow.

As shown in FIG. 1A, the cleaning work of the post-treatment step is simplified by intensively precipitating the high pH crystallization component in the pre-treatment portion of the post-treatment step and replacing the frame net 17 as necessary. Can be transformed into. In FIG. 1A, instead of replacing the frame net 17, a plurality of precipitation tanks 10 are prepared in advance, and the precipitation tanks 10 are replaced as necessary to simplify the cleaning work in the post-treatment step. It is also possible to make it. As described above, most of the crystals precipitated inside the precipitation tank 10 adhere to the surface of the frame net 17, but some of them do not adhere and precipitate at the bottom of the bottomed chamber 11, so that the post-treatment step is blocked. In order to avoid this, it is not enough to replace the frame net 17, and it may be necessary to clean the inside of the bottomed chamber 11. By replacing the precipitation tank 10 itself, the cleaning work in the post-treatment step can be further simplified.

Preferably, as shown in FIG. 2A, the precipitation tank 10 includes a pair of bottomed chambers 11a and 11b. An aeration device 15 and a metal frame net 17 are provided in each of the bottomed chambers 11a and 11b, respectively, and an intake port 12 and an overflow weir 14 are provided. Further, a switching valve 40 (V1, V2) for connecting the inflow path 2a of the fermented liquid to the intake port 12 of either of the bottomed chambers 11a and 11b is provided, and the overflow of either of the bottomed chambers 11a and 11b is provided. A switching valve 40 (V3, V4) for connecting the weir 14 to the subsequent fermentation broth adjusting tank 20 is provided.

In the embodiment of FIG. 2A, for example, the switching valves V1 and V3 are opened (switching valves V2 and V4 are closed) to incorporate the bottomed chamber 11a into the post-treatment step, and the bottomed chamber 11a is contained in the treatment liquid F. Intensive precipitation of high pH crystallization components. After the precipitated crystals are sufficiently deposited on the surface of the frame net 17, the switching valves V1 and V3 are closed (switching valves V2 and V4 are opened) to separate the bottomed chamber 11a from the post-treatment step and the other bottomed. A chamber 11b is incorporated, and the high pH crystallization component in the treatment liquid F is intensively deposited in the other bottomed chamber 11b. The inside of the bottomed chamber 11a can be cleaned in a state of being separated from the post-treatment step.

When the crystals deposited on the surface of the frame net 17 of the bottomed chamber 11b are sufficiently deposited, the switching valves V1 and V3 are opened (switching valves V2 and V4 are closed) to remove the bottomed chamber 11b from the post-treatment step. Upon disconnection, the bottomed chamber 11a is reassembled, and the high pH crystallization component in the treatment liquid F is intensively deposited in the bottomed chamber 11a. By repeating the switching of the bottomed chambers 11a and 11b in this way, the post-treatment step can be easily cleaned while continuously receiving the fermented liquid F without stopping the operation of the methane fermenter 2. It is possible to avoid blockage of the processing tank and piping in the process.

In this way, it is possible to achieve the object of the present invention, "a post-treatment method and apparatus for a methane fermented liquid capable of simplifying cleaning of the post-treatment step".

FIG. 1B is another embodiment of the present invention in which the bottomed chamber 11 of the precipitation tank 10 of FIG. 1A is incorporated inside the inflow port 21 of the fermentation broth adjusting tank 20 which is a subsequent post-treatment step. An example is shown. As described above with reference to FIG. 1 (A), the precipitation tank 10 is installed between the methane fermentation tank 2 and the fermentation broth adjusting tank 20 to concentrate the high pH crystallization components in the fermentation broth F. By precipitating, the precipitation of crystals in the subsequent post-treatment step is suppressed to a small size, but an additional installation space is required as compared with the conventional fermentation broth adjusting tank 20. By incorporating the bottomed chamber 11 of the precipitation tank 10 inside the fermented liquid adjusting tank 20 as shown in FIG. 1 (B), the fermented liquid adjusting tank 20 can be installed even when an additional installation space cannot be secured. A part of the space can be used to concentrate the high pH crystallization component.

In the embodiment of FIG. 1B, a bottomed small room 11 with an overflow weir 14 is provided inside the inflow port 21 of the fermented liquid adjusting tank 20 by partitioning from the surroundings, and the bottomed small room 11 is equipped with an aeration device 15. A metal frame net 17 is arranged to form a precipitation tank 10. The inflow port 21 of the fermented liquid adjusting tank 20 is connected to the fermented liquid inflow path 2a, and the fermented liquid F after the methane fermentation treatment generated in the methane fermentation tank 2 is taken in from the inflow port 21 of the fermented liquid adjusting tank 20. The bottomed small chamber 11 in the illustrated example is an open top type, and the fermented liquid F taken in from the inflow port 21 of the fermented liquid adjusting tank 20 stays in the bottomed small chamber 11 inside the inflow port 21 for a predetermined time. After the high pH crystallization component is intensively deposited in the bottom small chamber 11, it is sent from the overflow dam 14 of the bottom small chamber 11 to the fermentation broth adjusting tank 20. The capacity of the bottomed small chamber 11 can be designed so that the fermented liquid F stays for a sufficient time for the high pH crystallization component to precipitate, but it is desirable that the capacity is such that it can be cleaned in a short time.

Further, in the embodiment of FIG. 1B, the aeration device 26 is also provided in the fermented liquid adjusting tank 20, and the high pH crystallization component in the unprecipitated fermented liquid F in the bottomed small chamber 11 is put into the fermented liquid adjusting tank 20. It is precipitating. That is, the high pH crystallization component in the fermented liquid F is precipitated in the bottomed small chamber 11 as much as possible, but the precipitation is insufficient only by the capacity of the bottomed small chamber 11, and the fermented liquid overflows into the fermented liquid adjusting tank 20. Unprecipitated high pH crystallization components may remain in F. Also in the fermented liquid adjusting tank 20, the fermented liquid F sent out from the outlet 22 of the fermented liquid adjusting tank 20 by raising the pH in the fermented liquid F by the aeration device 26 to promote the precipitation of the high pH crystallization component. It is possible to reduce the unprecipitated high pH crystallization component in the fermenter and suppress the precipitation of crystals in the subsequent post-treatment step of the fermenter adjusting tank 20 to a small value.

Since it is difficult for the aeration device 26 shown in FIG. 1B to be seated on the inclined bottom surface 23 of the fermented liquid adjusting tank 20 described later, the aeration device 26 is suspended from the top surface of the fermented liquid adjusting tank 20 and submerged in the fermented liquid F. There is. Further, in the bottomed small chamber 11, a metal frame net 17 is attached to the aeration device 15 to adhere and grow the precipitated crystals, whereas the aeration of the fermentation broth adjusting tank 20 is unprecipitated in the fermentation broth F. Since the purpose is the supplementary precipitation of the high pH crystallization component of the above, the metal frame net 17 is not attached to the aeration device 26, and the precipitated crystals are precipitated on the bottom surface 23 of the fermentation broth adjusting tank 20. .. However, it is also possible to attach a metal frame net 17 to the aeration device 26 of the fermentation broth adjusting tank 20 to attach and grow the precipitated crystals.

The fermented liquid adjusting tank 20 shown in FIG. 1B has an inclined bottom surface 23, and by installing a damming plate 23a at the lower end portion of the inclined bottom surface 23, the precipitated crystals precipitated at the lower end portion of the bottom surface are provided. The collection groove 24 is formed. As described above, since the precipitated crystals are precipitated in the fermented liquid adjusting tank 20, it may be necessary to appropriately clean the inside of the fermented liquid adjusting tank 20, particularly the entire bottom surface. By inclining the bottom surface 23 as shown in the illustrated example so that the precipitated crystals are collected in the collection groove 24, the precipitated crystals can be collected by cleaning the area around the collection groove 24, which simplifies the cleaning work.・ It is possible to shorten the time.

Preferably, as shown in FIG. 2B, a pair of fermentation broth adjusting tanks 20a and 20b are provided, and bottomed small chambers 11 are incorporated into the adjusting tanks 20a and 20b to form precipitation tanks 10a and 10b, respectively. An aeration device 15 and a metal frame net 17 are provided in the bottomed small chambers 11 of the adjusting tanks 20a and 20b, respectively, and an overflow weir 14 is provided. Further, a switching valve 40 (V1, V2) for connecting the inflow path 2a of the fermented liquid to the inflow port 21 of either one of the fermented liquid adjusting tanks 20a and 20b is provided, and one of the fermented liquid adjusting tanks 20a and 20b is provided. A switching valve 40 (V3, V4) for connecting the outlet 22 to a subsequent post-treatment step (for example, the fermented liquid pump 29 and the solid-liquid separating device 30 in FIG. 4) is provided.

Similar to the case of FIG. 2A described above, in the embodiment of FIG. 2B, for example, the switching valves V1 and V3 are opened (switching valves V2 and V4 are closed), and the fermentation broth adjusting tank 20a is rearranged. Incorporated into the treatment step, the high pH crystallization component in the treatment liquid F was intensively deposited in the bottomed small chamber 11 of the fermented liquid adjusting tank 20a, and further, not in the fermenting liquid adjusting tank 20a outside the bottomed small chamber 11. The high pH crystallization component of the precipitate is supplementarily precipitated. After the crystals are sufficiently precipitated, the switching valves V1 and V3 are closed (switching valves V2 and V4 are opened) to separate the fermented liquid adjusting tank 20a from the post-treatment step and incorporate the other fermented liquid adjusting tank 20b into the other. High pH crystallization components in the treatment liquid F are intensively precipitated in the bottomed small chamber 11 of the fermented liquid adjusting tank 20b, and unprecipitated high pH crystals are further deposited in the fermented liquid adjusting tank 20a outside the bottomed small chamber 11. The crystallization component is supplementarily precipitated.

Further, when crystals are sufficiently precipitated in the fermented liquid adjusting tank 20b, the switching valves V1 and V3 are opened (switching valves V2 and V4 are closed) to separate the fermented liquid adjusting tank 20b from the post-treatment step and to adjust the fermented liquid. The tank 20a is reassembled, and the high pH crystallization component in the treatment liquid F is precipitated in the fermentation broth adjusting tank 20a. By repeating the switching of the fermented liquid adjusting tanks 20a and 20b in this way, even if it takes time to clean the inside of the fermented liquid adjusting tanks 20a and 20b, there is no possibility of affecting the operation of the methane fermentation plant. In addition, the post-treatment process can be easily cleaned while continuously receiving the fermented liquid F without stopping the operation of the methane fermentation tank 2, and it is possible to avoid blockage of the treatment tank and piping in the post-treatment process. Become.

1 ... Raw material tank 1a ... Raw material pump 2 ... Methanogen fermenter (bioreactor) 2a ... Fermentation liquid inflow path 10 ... Precipitation tank (precipitation chamber) 11 ... Bottomed chamber (bottomed small room)
12 ... Intake 14 ... Aeration dam 15 ... Aeration device 15a ... Intake port 15b ... Sealing end 15c ... Air supply pipe 15d ... Blow-out hole 15e ... Mounting plate 16 ... Aeration hose 17 ... Metal frame net 17a ... Fixing jig 20 ... Fermentation liquid adjusting tank 21 ... Inflow port 22 ... Outlet 23 ... Internal bottom surface (inclined bottom surface) 23a ... Dam stop plate 24 ... Collection groove 26 ... Aeration device 27 ... Aeration hose 28 ... Hanging member 29 ... Fermentation liquid pump 30 ... Solid-liquid separation device 31 ... Coagulant tank 31a ... Coagulant pump 32 ... Sulfant tank 33 ... Sulfate pump 34 ... Wastewater treatment device 35 ... Drainage pumps 40, 41 ... Switching valve S ... Biomass F ... Fermented liquid G ... Biogas P … Aeration gas

Claims (4)

A bottomed chamber is provided inside the inlet of the fermented liquid adjustment tank that takes in the fermented liquid after the methane fermentation treatment of biomass and temporarily retains it. The pH crystallization component is precipitated by increasing the pH, and at least a part of the precipitated crystals during aeration is attached to a metal frame network that is replaceably settled in the bottomed chamber, and the fermented liquid after the crystal precipitation is present. It overflows from the bottom chamber to the fermented liquid adjusting tank and temporarily stays there, and is exposed to air in the fermented liquid adjusting tank to precipitate unprecipitated high-pH crystallization components in the fermented liquid by increasing the pH, and then crystallized. A post-treatment method for methane fermented liquid, in which the later fermented liquid is sent to a subsequent post-treatment step. A fermented liquid adjusting tank that takes in the fermented liquid after the methane fermentation treatment of biomass and temporarily retains it, a bottomed chamber provided inside the inlet of the fermented liquid adjusting tank, which is partitioned from the surroundings, and the inside of the bottomed chamber is exposed to air. It has an aeration device that precipitates high pH crystallizing components in the fermented liquid by increasing the pH, a metal frame net that is interchangeably set above the aeration device in the bottomed chamber, and the fermented liquid after the crystal precipitation. Equipped with an overflow dam that overflows from the bottom chamber to the fermentation broth adjustment tank , and an aeration device that aerates the inside of the fermentation broth adjustment tank to precipitate unprecipitated high-pH crystallizing components in the fermentation broth by increasing the pH. A post-treatment device for methane fermented liquid. The apparatus according to claim 2 , wherein the fermented liquid adjusting tank is provided with an inclined bottom surface, and a collecting groove for the precipitated crystals is formed at the lower end of the inclined bottom surface. In the apparatus according to claim 2 or 3 , a pair of fermented liquid adjusting tanks with a bottomed chamber is provided, and the inflow path of the fermented liquid after the methane fermentation treatment is the inflow port of any of the fermented liquid adjusting tanks with a bottomed chamber . A post-treatment device for methane fermented liquid provided with a switching valve connected to.

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