JP2012213768A - Anaerobic digestion treatment apparatus and digestion accelerated procedure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anaerobic digestion treatment apparatus that improves the contact efficiency between the solid content of undecomposition and a cell, and promotes the digestion under an anaerobic condition, and to provide a digestion accelerated procedure.SOLUTION: The anaerobic digestion treatment apparatus includes: a methane fermentation tank 31 that performs an anaerobic digestion treatment of an organic raw material; a solid-liquid separator 32 that solid-liquid separates a digestive sludge; a supply route 33 that supplies the digestive sludge of the methane fermentation tank 31 to the solid-liquid separator 32; and a sending back route 34 that supplies the concentration digestion sludge of the solid-liquid separator 32 to the methane fermentation tank 31, and includes a swirl flow generator 45 that forms a swirl flow that turns around the center of the methane fermentation tank 31 by a plane view, wherein the sending back route 34 opens to the center neighborhood of the swirl flow, and sends back the concentration digestion sludge of the solid-liquid separator 31 to the region near the tank bottom of the methane fermentation tank 31.

Description

  The present invention relates to an anaerobic digestion treatment apparatus that digests organic waste under anaerobic conditions, and relates to a technique for promoting digestion.

  Conventionally, as this type of technology, there is one described in Patent Document 1. This is an organic waste introduced into the fermenter and digested under anaerobic conditions to recover methane gas. A fermentation inhibitor containing decomposition products produced by anaerobic digestion in the fermenter. The concentration is determined by actually measuring the digested sludge in the fermenter, and the moisture content of the digested sludge in the fermenter that is undergoing anaerobic digestion is adjusted based on the concentration of this fermentation inhibitor so as not to exceed the upper limit concentration. The value controls the concentration of the fermentation inhibitor.

  In order to reduce the moisture content of the digested sludge, the organic waste is concentrated or added undiluted, and a part of the digested sludge is separated into solid and liquid by solid-liquid separation means, and the filtrate is removed from the system. Pulling out or both.

  In order to increase the moisture content of digested sludge, a part of the digested sludge is solid-liquid separated by solid-liquid separation means, the filtrate is drawn out of the system, and diluted water not containing the fermentation inhibitor is supplied. Is done by.

JP 2000-70908 A

  By the way, organic wastes with high water content such as garbage and high-concentration organic wastewater containing organic substances at a higher concentration than general organic wastewater, such as palm oil production wastewater (hereinafter referred to as POME). ), When processing starch processing wastewater such as tapioca and potato, molasses refining wastewater (molasses), biomass ethanol distillation residue, etc., for example, when anaerobic digestion using POME as raw material, methane fermentation proceeds and biogas is generated .

  In order for methane fermentation to proceed efficiently in an anaerobic digester, it is necessary for the raw material and the cells to come into uniform contact in the methane fermenter. However, when the methane fermentation tank becomes large, it cannot be guaranteed that all raw materials come into contact with the bacterial cells, and undecomposed solids and bacterial aggregates in the raw material liquid in the tank settle to the bottom of the tank. In some cases, in order to achieve uniform contact between the raw material and the cells in the large-capacity tank region, a large-scale stirring device for stirring the entire tank is required.

  The present invention solves the above-described problems, and provides an anaerobic digestion treatment apparatus and a digestion promotion method that promotes digestion under anaerobic conditions by increasing the contact efficiency between undegraded solids and bacterial cells. For the purpose.

  In order to solve the above problems, an anaerobic digestion treatment apparatus of the present invention comprises an anaerobic digestion tank for anaerobic digestion treatment of organic raw materials, a solid-liquid separation apparatus for solid-liquid separation of digested sludge, and an anaerobic digestion tank. An anaerobic digestion treatment apparatus comprising a supply path for supplying digested sludge to a solid-liquid separator and a return path for supplying concentrated digested sludge of the solid-liquid separator to an anaerobic digester, wherein The recirculation flow generating device that forms a swirling flow swirling around the center of the digestive digestion tank, and one end of the return path is opened near the center of the swirling flow, and the concentrated digested sludge of the solid-liquid separation device Is returned to the tank bottom in the anaerobic digestion tank.

In the anaerobic digestion processing apparatus of the present invention, the swirling flow generating device is arranged near the inner wall surface of the anaerobic digestion tank, and discharges the digested sludge flow.
In the anaerobic digestion processing apparatus of the present invention, the return path is characterized by opening toward the bottom of the anaerobic digestion tank.

  In the anaerobic digestion treatment apparatus of the present invention, the solid-liquid separation device has a solid-liquid separation tank for storing the digested sludge, and a membrane separation apparatus that is immersed in the digested sludge in the solid-liquid separation tank. And

  The digestion promotion method of the present invention supplies the digested sludge in the anaerobic digester to the solid-liquid separator when the organic raw material is anaerobically digested in the anaerobic digester, and in the digested sludge by the solid-liquid separator The digested sludge is concentrated by taking out a part of the liquid, and a swirling flow of the digested sludge swirling around the center of the anaerobic digester is formed in a plan view in the anaerobic digester by a swirling flow generator. In the vicinity of the center of the swirl flow and in the region near the bottom of the anaerobic digester, the digestion promoting region is used, and solids having sedimentation in the digested sludge are collected in the digestion promoting region by the swirl flow, and solid-liquid separation is performed. Concentrated digested sludge, which is digested sludge concentrated by an apparatus, is supplied to the digestion promoting region, and undegraded raw material components of solids are digested by microorganisms in the concentrated digested sludge.

  As described above, according to the present invention, the digested sludge is swirled as a swirling flow in an anaerobic digester (methane fermentation tank), so that an undecomposed raw material is used as a digestion promoting region at the center of the bottom of the anaerobic digester. It is possible to form a region where sedimentary solid components including components are likely to accumulate. By supplying concentrated digested sludge with increased microbial (bacterial cell) concentration in a solid-liquid separation device to the place where undegraded raw material components of solid matter are gathered or gathered in this digestion promotion area, The frequency of contact between raw material components and microorganisms increases, and the undecomposed raw material components are rapidly decomposed.

  Concentrated digested sludge has a higher specific gravity and viscosity than the digested sludge in the methane fermentation tank, so by supplying the concentrated digested sludge to the digestion-promoting region, the sedimentary solids that accumulate in the digestion-promoting region It is possible to make it rise more efficiently and to disperse sedimentary solids with concentrated digested sludge efficiently.

The schematic diagram of the anaerobic digestion processing apparatus which shows embodiment of this invention Top view of the anaerobic digester of the same anaerobic digester The schematic diagram of the anaerobic digestion processing apparatus which shows other embodiment of this invention. Schematic diagram of a sedimentation tank showing another embodiment of the present invention The top view of the anaerobic digester which shows other embodiment of this invention. The schematic diagram of the anaerobic digestion processing apparatus which shows other embodiment of this invention. The schematic diagram of the anaerobic digestion processing apparatus which shows other embodiment of this invention. The schematic diagram of the anaerobic digestion processing apparatus which shows other embodiment of this invention. The flow sheet figure which shows the whole structure of the anaerobic digestion processing apparatus of this invention

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 9, the anaerobic digestion processing facility includes a receiving unit 10, a storage unit 20, and an anaerobic digestion processing unit 30.
The receiving unit 10 includes a screen 11 that removes floating substances such as residue and sand contained in the inflowing organic raw material 1, a removed material pit 12 that collects the removed material separated by the screen 11, and a removed material pit 12. A pit pump 13 that discharges the removed material, a supply tank 14 into which the organic raw material 1 that has passed through the screen 11 flows, and a transfer pump 15 that transfers the organic raw material 1 in the supply tank 14 to the storage unit 20 are provided.

  The storage unit 20 includes a storage tank 21 that stores the organic raw material 1 sent by the transfer pump 15, a stirring device 22 that is provided inside the storage tank 21 and stirs the organic raw material 1, and a storage tank 21. A supply pump 23 for supplying the organic raw material 1 to the anaerobic digestion processing unit 30 is provided.

  The anaerobic digestion processing unit 30 includes a methane fermentation tank 31 as an anaerobic digestion tank for anaerobic digestion treatment of organic raw materials, a sealed solid-liquid separation apparatus 32 for solid-liquid separation of digested sludge, and a methane fermentation tank 31. A supply path 33 for supplying the digested sludge inside the solid-liquid separator 32 through the overflow tank 354 and a return path 34 for supplying the concentrated digested sludge of the solid-liquid separator 32 to the methane fermentation tank 31. ing.

The overflow tank 354 is necessary for adjusting and maintaining the liquid level in the solid-liquid separator 32 when the liquid level in the solid-liquid separator 32 is lower than the liquid level in the methane fermentation tank 31.
The solid-liquid separation device 32 includes a solid-liquid separation tank 321 that stores digested sludge, a plurality of membrane separation apparatuses 35 that are immersed in the digested sludge in the tank of the solid-liquid separation tank 321, and each membrane separation apparatus 35. The air diffuser 36 is disposed below the air diffuser 36. Although there are various types of membrane separation devices 35, in this embodiment, the membrane separation device 35 has a plurality of membrane cartridges (not shown) arranged in parallel, and the upward flow between the membrane cartridges. Has a road. A biogas supply path 37 is connected to the air diffuser 36. The biogas supply path 37 has a base end side communicating with the tank upper space of the solid-liquid separator 32, and a mist separator 38 interposed in the middle of the path and A blower 39 is provided, and the tip side communicates with the air diffuser 36.

  A permeate flow path 40 is connected to the secondary side of the membrane separation apparatus 35, and the permeate flow path 40 is connected to the secondary side of each membrane separation apparatus 35 at the base end side, and is interposed in the middle of the path. A suction pump 41 is provided, and the tip side communicates with the permeate pit 42. The permeate pit 42 has a pit discharge pump 43. The return path 34 has a sludge return pump 44 that is connected to the downstream side of the solid-liquid separation tank 321 on the base end side, and is interposed in the middle of the path, and has a tip side near the center of the methane fermentation tank 31 and toward the bottom of the tank. The concentrated digested sludge in the solid-liquid separation tank 321 is returned to the tank bottom vicinity region of the methane fermentation tank 31.

  As shown in FIGS. 1 and 2, the methane fermentation tank 31 has a plurality of swirling flow generators 45 arranged near the inner wall surface of the tank, and the swirling flow generating apparatus 45 discharges the digested sludge flow at a predetermined flow rate. It has a rotary blade 451 and forms a swirl flow swirling around the center of the circular methane fermentation tank 31 in plan view. Therefore, the rotation axis direction of the rotary blade 451 is directed so as to deviate from the center of the methane fermentation tank 31.

In the methane fermentation tank 31, a gas holder 46 is connected to the upper space of the tank. In addition, in FIG. 1, the structure of the anaerobic digestion process part 30 is displayed simply.
Hereinafter, the operation of the above configuration will be described. In the receiving unit 10, the screen 11 removes suspended substances such as residue and sand contained in the organic raw material 1 flowing into the system, and stores the organic raw material 1 that has passed through the screen 11 in the supply tank 14. The organic raw material 1 in the supply tank 14 is transferred to the storage unit 20 by the transfer pump 15.

  In the storage unit 20, the organic raw material 1 sent by the transfer pump 15 is stored in the storage tank 21, and the organic raw material 1 is stirred by the stirring device 22 provided inside the storage tank 21. The organic raw material 1 is supplied to the anaerobic digestion processing unit 30 by the supply pump 23.

  In the anaerobic digestion processing unit 30, the organic raw material 1 sent by the supply pump 23 is guided to the methane fermentation tank 31, the organic raw material 1 is anaerobically digested, and the generated biogas is stored in the gas holder 46. .

  In this anaerobic digestion treatment, the digested sludge inside the methane fermentation tank 31 is supplied to the solid-liquid separation device 32 through the overflow tank 354 disposed adjacent to the methane fermentation tank 31 and the supply path 33 that follows the overflow tank 354. The separation sludge is subjected to solid-liquid separation in the separation device 32, and the concentrated digested sludge of the solid-liquid separation device 32 is supplied to the methane fermentation tank 31 through the return path 34 by the sludge return pump 43. The operation in the methane fermentation tank 31 will be described later.

  In the solid-liquid separator 32, the digested sludge in the tank of the solid-liquid separator 321 is converted into a plurality of membranes while the biogas is diffused from each aerator 36 as a membrane surface cleaning gas toward each membrane separator 35. The permeate separated by the separation device 35 and permeated to the secondary side of the membrane separation device 35 is taken out through the permeate flow path 40 by the suction pump 41 and stored in the permeate pit 42, and then the system is removed by the pit discharge pump 43. Take it out.

  The biogas staying in the tank upper space of the solid-liquid separator 32 is taken out through the biogas supply path 37, separated from the mist by the mist separator 38, and then supplied to the diffuser 36 by the blower 39.

  In the methane fermentation tank 31, the swirling flow generator 45 discharges the digested sludge flow along the inner wall surface of the tank at a predetermined flow rate to form a swirling flow that swirls around the center of the methane fermentation tank 31 in plan view. The concentrated digested sludge of the solid-liquid separator 32 is returned from the opening of the return path 34 to the vicinity of the center of the methane fermentation tank 31, that is, the vicinity of the center of the swirl flow and the vicinity of the tank bottom of the methane fermentation tank 31.

  In this way, by turning the digested sludge as a swirl flow inside the methane fermentation tank 31, sedimentary solids containing undecomposed raw material components are accumulated as a digestion promoting region in the center of the bottom of the methane fermentation tank 31. An easy region can be formed. In this digestion promotion area, solid undegraded raw material components are collected, and concentrated digested sludge having a higher microorganism (bacterial cell) concentration is supplied by the solid-liquid separation device 32, so that the frequency of contact between the undegraded raw material components and the microorganisms is increased. And undecomposed raw material components are rapidly decomposed.

  In addition, since the concentrated digested sludge has a specific gravity and viscosity larger than the digested sludge in the methane fermentation tank 31, by supplying the concentrated digested sludge to the digestion promoting area, the sedimentary solid content accumulated in the digestion promoting area can be obtained by the concentrated digested sludge. It is possible to make it rise more efficiently and to disperse sedimentary solids with concentrated digested sludge efficiently.

  In the above-described embodiment, the solid-liquid separation device 32 includes the solid-liquid separation tank 321 and the membrane separation device 35. As shown in FIG. 3, an external pressure type membrane separation device 352 of the total filtration type is used. Is also possible. In this case, a pressure pump 331 is provided in the middle of the supply path 33.

  Moreover, in above-mentioned embodiment, although the front-end | tip opening of the return path 34 is opening toward the tank bottom face of the methane fermentation tank 31, as shown in FIG. You may make it open to a horizontal direction along the tank bottom face, or to open in several directions.

Further, as shown in FIG. 5, the opening at the front end of the return path 34 may be opened in one direction along the bottom surface of the methane fermentation tank 31 in the horizontal direction.
Further, as shown in FIG. 6, the opening at the front end of the return path 34 may be opened upward from the bottom surface of the methane fermentation tank 31.

  Further, as shown in FIG. 7, the solid-liquid separation device 32 can adopt a sedimentation separation method using a precipitation tank 353, and various solid-liquid separation devices 32 can be adopted. .

  Further, as shown in FIG. 8, as the swirling flow generator 45, an external flow path 311 is provided in the methane fermentation tank 31, and the tip of the external flow path 311 is opened near the inner wall surface of the methane fermentation tank 31. At the same time, a discharge pump 312 can be provided in the external flow path 311.

  In this configuration, the digested sludge in the methane fermentation tank 31 is sucked into the external flow path 311, and the digested sludge is discharged from the front end opening of the external flow path 311 along the tank inner wall surface at a predetermined speed by the discharge pump 312. As the swirl flow generator 45, various devices can be adopted.

DESCRIPTION OF SYMBOLS 10 Receiving part 20 Storage part 30 Anaerobic digestion process part 1 Organic raw material 11 Screen 12 Removal thing pit 13 Pit pump 14 Supply tank 15 Transfer pump 21 Storage tank 22 Stirrer 23 Supply pump 31 Methane fermentation tank 32 Solid-liquid separator 33 Supply path 34 Return path 35 Membrane separator 36 Air diffuser 37 Biogas supply path 38 Mist separator 39 Blower 40 Permeate flow path 41 Suction pump 42 Permeate pit 43 Pit discharge pump 44 Sludge return pump 45 Swirl flow generator 46 Gas Holder 311 External channel 312 Discharge pump 321 Solid-liquid separation tank 331 Pressure feed pump 352 Membrane separation device 353 Settling tank 354 Overflow tank 451 Rotating blade

Claims (5)

Anaerobic digester for anaerobic digestion of organic raw materials, solid-liquid separator for solid-liquid separation of digested sludge, supply path for supplying digested sludge in anaerobic digester to solid-liquid separator, and solid-liquid An anaerobic digestion treatment device comprising a return path for supplying the concentrated digested sludge of the separation device to the anaerobic digestion tank,
A swirl flow generating device that forms a swirl flow swirling around the center of the anaerobic digester in plan view, the return path having one end opened near the center of the swirl flow, and the solid-liquid separation An anaerobic digestion treatment apparatus, wherein the concentrated digested sludge of the apparatus is returned to the bottom of the anaerobic digestion tank.   2. The anaerobic digestion apparatus according to claim 1, wherein the swirl flow generator is disposed near the inner wall surface of the anaerobic digester and discharges a digested sludge stream.   The anaerobic digestion processing apparatus according to claim 1, wherein the return path opens toward the bottom of the anaerobic digestion tank.   The solid-liquid separator has a solid-liquid separation tank for storing digested sludge, and a membrane separator arranged to be immersed in the digested sludge in the solid-liquid separation tank. Anaerobic digester.   When anaerobic digestion treatment is performed on organic raw materials in an anaerobic digestion tank, the digested sludge in the anaerobic digestion tank is supplied to the solid-liquid separator and a part of the liquid in the digested sludge is taken out by the solid-liquid separator. In order to concentrate the digested sludge, a swirling flow of digested sludge swirling around the center of the anaerobic digestion tank in a plan view in the anaerobic digestion tank by a swirling flow generator, in the vicinity of the center of the swirling flow, In the anaerobic digestion tank, the area near the bottom of the tank is used as a digestion promoting area, and the solid content having sedimentation in the digested sludge is collected in the digestion promoting area by the swirl flow and concentrated by the solid-liquid separator. A digestion promoting method characterized by supplying a certain concentrated digested sludge to a digestion promoting region and digesting undegraded raw material components of solids by microorganisms in the concentrated digested sludge.

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