JP2019084508A - Methane fermentation system and methane fermentation method - Google Patents

Abstract

To provide a methane fermentation system and a methane fermentation method which can achieve both stable discharge of residues and fermentation foreign matters and circulation of the residues necessary for fermentation by reducing fluctuation of concentration of the fermentation foreign matters such as plastics, soil, and metals contained in an object to be fermented and fluctuation of solid matter concentration in a fermenter.SOLUTION: A methane fermentation system includes; a fermenter main body 1 having a laterally-long cylindrical shape; a supply port 2 arranged on one end side in a longitudinal direction of the fermenter main body 1; an upper discharge port 3 arranged on an upper part of the other end side in the longitudinal direction of the fermenter main body 1; a lower discharge port 4 arranged on a lower part of the other end side in the longitudinal direction of the fermenter main body 1; an intermediate discharge port 7 arranged on an intermediate part between the upper discharge port 3 and the lower discharge port 4; and a return passage 8 for drawing residues from the intermediate discharge port 7 and returning the same to the fermenter main body 1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a methane fermentation system in which a dry horizontal fermenter for treating combustible waste (general waste) and the like is installed and a methane fermentation method using the dry horizontal fermenter.

  Conventionally, as shown in FIG. 2, the horizontally long cylindrical fermenter main body 1, the supply port 2 provided on one end side in the longitudinal direction of the fermenter main body 1, and the other end side in the longitudinal direction of the fermenter main body 1 Upper exhaust port 3 and lower exhaust port 4 provided in upper and lower portions, stirring paddle 5 provided in the inside of fermenter main body 1, and gas exhaust port 6 provided in the upper part of peripheral surface of fermenter main body 1 Dry horizontal fermenters are known.

  This type of dry horizontal fermenter is used for dry methane fermentation, and is a so-called plug flow (push flow) method, and the combustible waste G pushed from the supply port 2 using the positive displacement piston pump P1 is the supply port 2 It is forced to flow toward the upper outlet 3 and the lower outlet 4 and is fermented in the middle of being flushed to generate methane gas, and the residue is discharged from the upper outlet 3 and the lower outlet 4 using the positive displacement piston pump P2 As a result, the inside of the pipe is pumped. The generated methane gas is recovered through the gas outlet 6 and used as fuel for a gas generator or the like. The residue discharged from the upper discharge port 3 and the lower discharge port 4 is a foreign substance (fermented foreign substance, ie, plastic, which does not contribute to fermentation contained in the combustible waste in the residue (fermentation residue) after fermentation of the combustible waste Species, earth and sand, metals) may be included.

  The solid concentration in the fermenter is maintained as high as 15 to 40%, and in the plug flow mass transfer, the separation of foreign matter in the fermenter (floating of plastics, sedimentation of sediments and metals) is basically Depending on the specific gravity, the upper discharge port 3 tends to discharge plastics and the lower discharge port 4 tends to discharge earth and sand and metals.

  In addition, a part of the residue from the upper outlet 3 and the lower outlet 4 is returned to the supply port 2 through the return path 11 and circulated as a microorganism (methane bacteria) necessary for the continuation of methane fermentation. The circulation amount is required to be about 20 to 30% of the fermentation residue discharge amount.

Japanese Patent Application Publication No. 2009-502455

  However, the fermented residue from the fermenter is discharged together with the foreign matter from both the upper and lower discharge ports, and its piping has a piping structure in which the residue discharge and the residue circulation are partially used (the both branches along the way) The piping structure is branched at point D).

  In the case of a fermentation target with relatively few foreign substances such as food residue, it was possible to operate without problems in equipment that combines residue discharge and residue circulation, but when using combustible waste as a fermentation target, fermented foreign matter such as soil, metal, etc. However, it contaminates the object to be fermented to a large extent and also contaminates the residue discharged from the fermenter.

  Normally, the solid concentration is maintained at 15 to 40% in the fermenter of dry methane fermentation, and separation of foreign matter does not occur in the tank, but particularly when various combustible wastes are to be fermented Due to the fluctuation of the property, although it is temporary, there is a possibility that an increase in the amount of foreign matter input or a decrease in solid concentration in the fermenter may occur.

  In addition, when separation of foreign matter occurs in the fermenter, foreign matter mixed in the residue causes transfer inhibition.

  Furthermore, it is possible to circulate the foreign matter that does not need to be circulated, and the concentration of the foreign matter in the fermenter progresses, which is a factor that inhibits stable fermentation.

  Therefore, according to the present invention, in methane fermentation in which a dry horizontal fermenter is installed for combustible waste (general waste) and the like, fluctuation of concentration of fermentation foreign matter such as plastics, earth and sand and metals contained in the fermentation object and A main object of the present invention is to provide a methane fermentation system and a methane fermentation method capable of reducing fluctuations in solid concentration in a fermenter and achieving both stable residue and foreign matter discharge and circulation of the residue necessary for fermentation. Do.

  In order to achieve the above object, a methane fermentation system according to the present invention comprises a horizontally long cylindrical fermenter main body, a supply port provided on one longitudinal end side of the fermenter main body, and a longitudinal length of the fermenter main body In the upper outlet provided in the upper part on the other end side of the direction, the lower outlet provided in the lower part on the other end side in the longitudinal direction of the fermenter body, and an intermediate part between the upper outlet and the lower outlet An intermediate outlet provided, and a return path for withdrawing the residue from the intermediate outlet and returning it to the body of the fermenter.

  Further, the methane fermentation method according to the present invention comprises the steps of: supplying an object to be fermented from a supply port at one longitudinal end side of the horizontally long cylindrical fermenter main body; and pushing out the object to be fermented in the fermenter main body And discharging the residue of the lower layer portion in the fermenter main body from the lower discharge port on the other end side in the longitudinal direction of the fermenter main body, and the fermentation from the upper discharge port on the other end side in the longitudinal direction of the fermenter main body. The process of discharging the residue of the upper layer part in a tank main body, The process of withdrawing the residue from the intermediate | middle discharge port provided in the intermediate part of the said upper discharge port and the said lower discharge port and returning it to the said fermenter main body.

  According to the present invention, the residue is withdrawn from the intermediate discharge port assumed to be low in fermented foreign matter and returned to the body of the fermenter, and circulation of the residue prevents the circulation of the fermented foreign matter, thereby preventing foreign matter in the fermenter Deposition amount can be reduced.

It is a schematic block diagram which shows one Embodiment of the methane fermentation system which concerns on this invention by a partial cross section. It is a schematic block diagram which shows the conventional methane fermentation system in a partial cross section.

  An embodiment of the present invention is described below with reference to FIG. The same or similar component parts are denoted by the same reference numerals throughout the drawings and all embodiments including the prior art.

  The methane fermentation system according to the present invention, as schematically shown in FIG. 1, includes a horizontally long cylindrical fermenter main body 1 and a supply port 2 provided on a side wall 1 a on one end side in the longitudinal direction of the fermenter main body 1. And an upper outlet 3 provided at an upper portion of the side wall 1b at the other end in the longitudinal direction of the fermenter main body 1 and a lower outlet 4 provided at a lower part of the side wall 1b at the other end in the longitudinal direction of the fermenter main body 1 And an intermediate outlet 7 provided at an intermediate portion between the upper outlet 3 and the lower outlet 4 and a residue (fermentation residue and fermented foreign matter) from the intermediate outlet 7 to be returned to the fermenter main body 1 A return path 8, a stirring paddle 5 provided inside the fermenter main body 1, and a gas vent 6 provided on the upper part of the fermenter main body 1 are provided.

  Although the fermenter main body 1 is carrying out the shape which closed the both ends of the cylindrical wall 1c by a pair of side wall 1a, 1b in the example of illustration, if it is a laterally long cylindrical shape, it may not be cylindrical.

  Although the supply port 2 is provided in the side wall 1a which closes one end of the fermenter main body 1 in the example of illustration, it can also be provided in the circumferential wall 1c between both ends. The lower discharge port 4 and the upper discharge port 3 are also provided in the side wall 1 b closing the other end of the fermenter main body 1 in the illustrated example, but may be provided in the circumferential wall 1 c between both ends. The upper discharge port 3 is provided above the middle height of the fermenter main body 1. The lower discharge port 4 is provided in the vicinity of the bottom below the middle of the fermenter main body 1.

  In the illustrated example, the return path 8 connects one end of the pipe to the intermediate discharge port 7 and connects the other end of the pipe to the pipe 9 connected to the supply port 2. The other end of the piping of the return path 8 may be connected to a portion where the residue extracted from the fermenter main body 1 can be returned into the fermenter main body 1, for example, a return port at one end of the fermenter main body 1 (Not shown) may be provided and connected thereto. A piston pump P3 is connected to the return path 8, and the residue discharged from the intermediate discharge port 7 is returned through the return path 8 by the piston pump P3. The return amount (circulation amount) of the return path 8 is controlled by the number of operations of the piston pump P3.

  By switching the valves V1 and V2, the discharge from the upper discharge port 3 and the discharge from the lower discharge port 4 are switched. The valve V3 is used to open and close the return path 8.

  As described above, depending on the specific gravity of the fermented foreign matter, plastic is easily discharged from the upper discharge port 3 at the upper part of the fermenter main body 1, and the sediment from the lower discharge port 4 at the lower part of the fermenter main body 1 And metals tend to be discharged easily. Therefore, the residue discharged from the middle discharge port 7 in the middle part between the upper discharge port 3 and the lower discharge port 4 is contained in the fermentation as compared to the residue discharged from the upper discharge port 3 and the lower discharge port 4 There is a tendency for foreign matter to decrease.

  Therefore, the ratio of the foreign matter in the residue returned by the return path 8 does not exceed the ratio of the foreign matter in the whole residue in the fermenter, and even if the return is repeated to circulate the residue in the fermenter There is no progress in the concentration of the fermentation foreign matter.

  Further, by preferentially discharging the fermented foreign matter such as plastics, earth and sand, metal and the like from the upper outlet 3 and the lower outlet 4, the amount of foreign matter deposited in the fermenter decreases, and the fermentation efficiency increases.

  Furthermore, the piping of the discharge system 10 is simplified by separating the piping of the discharge system 10 of the lower discharge port 4 and the upper discharge port 3 from the piping of the circulation system by the return route 8, and the transfer inhibition factor due to fermentation foreign matter Is eliminated.

  According to the methane fermentation system having the above configuration, a line for discharging the residue in the fermenter and a line for circulating the residue in the fermenter are separately provided, and the residue of the intermediate layer with a relatively small amount of foreign matter is extracted By returning to the body of the fermenter, it is possible to prevent the circulation of the foreign matter that should not be circulated, and to reduce the amount of foreign matter that does not contribute to the fermentation in the fermenter.

Reference Signs List 1 fermenter body 2 supply port 3 upper outlet 4 lower outlet 5 stirring paddle 6 gas vent 7 intermediate outlet 8 return path

Claims (2)

  A horizontal tubular fermenter body, a supply port provided on one end side in the longitudinal direction of the fermenter body, an upper discharge port provided on the upper end on the other end side in the longitudinal direction of the fermenter body, A lower outlet provided at the lower end on the other end side in the longitudinal direction of the fermenter body, an intermediate outlet provided at an intermediate portion between the upper outlet and the lower outlet, and a residue drawn from the intermediate outlet And a return path for returning to the body of the fermenter. Supplying an object to be fermented from a supply port at one longitudinal end of the horizontal tubular fermenter body, pushing out the object to be fermented in the fermenter body, and the other end in the longitudinal direction of the fermenter body Discharging the residue of the lower layer in the fermenter main body from the lower outlet on the side, and discharging the residue of the upper layer in the fermenter main body from the upper outlet on the other end side in the longitudinal direction of the fermenter main body A process for methane fermentation comprising the steps of: extracting a residue from an intermediate outlet provided at an intermediate portion between the upper outlet and the lower outlet and returning the residue to the body of the fermenter.