JP4346035B2 - Continuous dry biomass gasification plant - Google Patents

Description

  The present invention directly and compactly connects the process of anaerobic methane fermentation of biomass such as garbage and organic waste and the process of aerobic fermentation and composting in an environment where the anaerobic fermentation residue is not directly exposed to the atmosphere. Relates to a continuous dry biomass gasification plant.

  Conventionally, the treatment of fluid biological waste such as livestock excreta has been performed by anaerobic fermentation with the help of methane bacteria, and the generated gas has been used as fuel and the fermentation residue as fertilizer. An anaerobic environment is required for methane fermentation, and the environment is realized by a wet method (or water seal type) that blocks oxygen by immersing the material in a large amount of water. In this case, since a mixture of fermentation residue and water is obtained, it is convenient if there is a condition that can be used as liquid fertilizer as it is. However, in an environment where liquid fertilizer is not used, solid-liquid separation operation and water treatment are required.

  On the other hand, a method called dry fermentation is being developed in recent years (see Non-Patent Document 1). This is an anaerobic fermentation process in a wet state with a moisture content of about 60 to 80 wt% without sealing the waste. The advantages of the dry type compared to the wet type are: There is no need to slurry solid biomass, and there is no need for pre-grinding; free from demand for residual liquid, and free from processing for it; solid residue Easily after-treatment when using for composting; generation of hydrogen sulfide of 1,000 ppm or more is extremely low at 10 to 30 ppm in wet process; generation of bad odor is low, and it can withstand installation in densely populated areas, etc. Non-patent document 2).

  However, BioFerm's demonstration plant introduced in Non-Patent Document 1 adopts a batch system in which two box-type fermenters are alternately used, and finishes the introduction and preparation of raw material biomass and methane fermentation. The process of taking out the biomass and composting is a form that relies heavily on manpower, and it seems that there is a problem in odor management.

  As another example, Takuma Co., Ltd. and other companies jointly received a subsidy for the Food Recycling Model Emergency Development Project of the Ministry of Agriculture, Forestry and Fisheries, and is currently implementing a dry solid treatment method mainly for food waste in Kyoto City. There is a recycling facility “Biogas Recycling Facility” (completed in March 2004, 50 t / day) (see Non-Patent Documents 3 and 4).

  In this example, a horizontal plug flow (extrusion flow) fermenter that is mechanically blocked from the outside air is used for anaerobic fermentation at a high solid content (water content: 60 to 85 wt%), and the fermentation residue is dehydrated with a dehydrator. After that, it is subjected to secondary fermentation in the residue yard to complete ripe compost. On the other hand, the dehydrated filtrate is subjected to reuse through a wastewater treatment tank after centrifugation.

  As can be seen in the above examples, most conventional biomass gasification plants require waste liquid treatment of anaerobic fermentation residues, and therefore employ field treatment requiring a large site. Moreover, since the secondary fermentation (aerobic fermentation for composting) of the anaerobic fermentation residue is performed in an atmospheric contact state, the location in the artificially crowded area is restricted due to odor problems.

  Recently, safety issues have emerged regarding this type of garbage disposal machine. It is an explosion and fire accident that occurred at the garbage disposal facility of the monkey food supermarket. The cause is assumed to be the overheating of the treated product due to the blowing of hot air while the stirrer is stopped, and the generation / accumulation / combustion of combustible gas such as hydrogen, carbon monoxide and methane due to this (Non-Patent Document 5) . Therefore, it is highly possible that the accident was caused by operational deficiencies rather than equipment defects.

  However, regarding the cause of the generation of the flammable gas, there is a risk that, in addition to the above causes, a partial mass in which anaerobic fermentation bacteria are active for some reason enters the aerobic fermentation region. This is because methane gas is generated in the anaerobic fermentation portion, oxygen is present in the aerobic fermentation region, and there is a risk that an methane / oxygen mixture with an explosive concentration is generated. Since the accident machine was an aerobic fermentation type, such a risk might have existed while the agitator was stopped. If such a danger is foreseen, it is natural to devise measures to avoid it in the present invention.

  Patent Document 1 below discloses a garbage processing machine in which both anaerobic and aerobic fermenters are provided adjacent to each other so that contents can be easily transferred between the two tanks. In one treatment tank with a stirrer, a technique is disclosed in which an organic substance decomposition treatment in an anaerobic environment and a compost maturation in an aerobic environment are switched. However, the danger of flammable gas generation is not mentioned in any document, and it is considered that it was a potential problem that has not been noticed yet at the time of establishment of the document.

BioFerm GmbH “Solid organic waste dry biogas plant” (Introduction brochure in Japanese) Tatsuo Shinriki “New Dry Biogas System with Water Separation in Germany” Monthly Waste 2002-7, pp70-76 Campo Cycle Plaza Introduction Material Campo Cycle Plaza Co., Ltd. Handouts accompanying the completion of the Campocycle Plaza “Biogas Recycling Facility” About Yamato-shi firefighting headquarters "summary of fire cause investigation to affect AEON Yamato shopping center explosion fire" (March 2, 2005) JP 2003-275718 A Japanese Patent Laid-Open No. 10-36186

  An object of the present invention is to realize an urban biomass gasification plant that can be located in an artificially crowded area, thereby enabling wide-area deployment of a biomass energy plant.

  In order to solve the above-mentioned problems, the present invention is more preferable in a process of anaerobically fermenting biomass such as garbage and recovering methane gas while paying particular attention to safety, and in an environment where anaerobic fermentation residues are not directly exposed to the atmosphere. The following continuous dry biomass gasification plant is provided, which is compactly connected to the process of composting by air fermentation. That is,

  A charging apparatus 1 for pulverizing and mixing raw material biomass and continuously charging it into an anaerobic fermentation tank, and a horizontal cylinder whose body is rotatably supported by support chambers 18 at both ends, mechanically sealed from outside air, and provided with stirring means An anaerobic fermenter 6 composed of a cylindrical rotating body 19, an aerobic fermenter 13 composed of a horizontal cylindrical rotating body 19 whose basic part has the same structure as the anaerobic fermenter and provided with forced aeration means, and anaerobic / aerobic In the anaerobic fermentation tank, an intermediate transfer device 10 for connecting both fermenters in tandem and transferring the anaerobic fermentation residue to the aerobic fermentation tank and a discharge device 16 for continuously discharging the fermentation residue from the aerobic fermentation tank are provided. Continuous dry biomass gasification that decomposes raw material biomass to generate methane gas, supplies the generated gas to the outside and the site, further matures the anaerobic fermentation residue in the aerobic fermentation tank and composts, and supplies the compost to the outside At the plant Thus, in order not to form a partial mass that maintains anaerobic fermentation inside the aerobic fermentation tank 13, the intermediate transfer device 10 continuously transfers the anaerobic fermentation residue into the aerobic fermentation tank 13 at a constant time rate. It is said gasification plant (Claim 1) which is transferred.

  The power generation facility using methane gas is an important accessory facility of this gasification plant, but is outside the scope of the present invention and is not described in claim 1.

  The plant comprises a rubber-like elastic body in which mechanical sealing in both anaerobic and aerobic fermenters is inserted between the cylindrical inner wall surface of the support chamber 18 and the end surface of the horizontal cylindrical rotary body 19. It can be configured to be achieved by the sliding packing 20 (claim 2).

  The plant includes a hollow fixed shaft in which both anaerobic and aerobic fermenters 6 and 13 are horizontally installed between support chambers 18 at both ends along the axis in a horizontal cylindrical rotary body 19. The contents of the tank can be conveyed as a whole from the upstream side to the downstream side of the tank while being stirred by the stirring blades provided on the surface of the fixed shaft and the wall surface of the rotating body.

  In the plant, the aerobic fermenter 13 includes a forced-aeration blower device 14 and a gas combustion type hot air generator 15, and supplies oxygen into the tank by ventilation from the blower device 14 or the hot air generator 15. Evaporation of excess water is promoted, and if necessary, the temperature of the contents of the aerobic fermentation tank 13 can be adjusted, and air and water vapor warmed by fermentation heat in the aerobic fermentation tank 13 are collected, and this air, etc. Is supplied into the hollow fixed shaft of the anaerobic fermenter 6 and, if necessary, the contents of the anaerobic fermenter 6 can be indirectly heated by using the surfaces of the hollow fixed shaft and the fixed stirring blade group as heat transfer surfaces. It may be configured (claim 4).

  The plant may be configured such that air or the like supplied into the hollow fixed shaft of the anaerobic fermenter 6 is discharged to the atmosphere from the end of the hollow fixed shaft through the deodorizing device 3 (Claim 5). .

  The plant can be configured such that the input device 1 has a function of degassing the air contained in the raw material biomass (Claim 6).

  The plant may be configured such that the intermediate transfer device 10 has a function of collecting drain from the anaerobic fermentation residue, and the collected drain is sprayed into the anaerobic fermentation tank (Claim 7).

  According to the first aspect of the present invention, after the raw material biomass is once put into the anaerobic fermenter, the oxygen is blocked by the effect of the mechanically sealed horizontal cylindrical rotary body (about 20 hours). After being decomposed while generating methane gas while remaining in the tank, and further transferred to the aerobic fermentation tank, it is subjected to aerobic fermentation for about 13 days under forced aeration and agitation to become fully matured compost. In the meantime, the influence of air, water and noise on the plant periphery can be minimized.

  In addition, the anaerobic fermentation residue is continuously transferred from the anaerobic fermenter to the aerobic fermenter by the intermediate transfer device under as little time variation as possible. Without forming a lump, it is immediately exposed to an overwhelmingly large amount of aerobic bacteria, and anaerobic fermentation is stopped in a short time to acclimate to aerobic fermentation. Therefore, the danger that the partial lump which continued the anaerobic fermentation will enter and mix in an aerobic fermenter will be prevented, and safety will be ensured.

  With these functions and effects in the invention of claim 1, it becomes possible to develop a biomass gasification plant over a wide area including an artificially crowded area.

  According to the invention of claim 2, the rubber-like elasticity in which the mechanical seal in both the anaerobic and aerobic fermenters is inserted between the cylindrical inner wall surface of the support chamber and the end surface of the horizontal cylindrical rotary body. Because it is achieved by sliding packing consisting of body, it is not necessary to seal the raw biomass, and as a result, dehydration and waste liquid treatment of anaerobic fermentation residues is unnecessary, and field treatment that requires a large site for that is also unnecessary Become.

  According to the invention of claim 3, the action of the feed agitating blade group in which both the anaerobic and aerobic fermenters are arranged on the surface of the hollow fixed shaft and the wall of the rotating body in each horizontal cylindrical rotating body. As a result, the contents slowly move forward while stirring the tank body and the required residence time in the tank is achieved.

  According to invention of Claim 4, since an aerobic fermenter is equipped with the blower for forced ventilation and a gas combustion type | formula hot-air generator, it is surplus simultaneously with oxygen supply in a tank by the ventilation from this blower apparatus or a hot-air generator. The evaporation of moisture can be promoted, and the temperature of the contents of the aerobic fermenter can be adjusted as necessary. Also, air and water vapor heated by fermentation heat in the aerobic fermentation tank are collected, and this air and the like are guided into the hollow fixed shaft of the anaerobic fermenter, and the surfaces of the hollow fixed shaft and the fixed stirring blade group are heated. As the content of the anaerobic fermenter can be indirectly heated, the temperature of the content of the anaerobic fermenter is maintained at an appropriate temperature using waste heat given from the aerobic fermenter while maintaining the anaerobic environment. Can be adjusted to.

  According to invention of Claim 5, the intermediate transfer apparatus installed between both anaerobic and aerobic fermenters has a function which collect | recovers drains from anaerobic fermentation residue, In the collected drains, highly active methane bacteria Is contained in abundantly and returned to the tank through a pipe provided in the anaerobic fermenter, so that the fermentation activity in the anaerobic fermenter is maintained at a high level, which helps to promote the fermentation. It should be noted that drain collection in the intermediate transfer machine is not performed because it is not necessary to settle and separate the filtrate for that purpose.

  According to the invention of claim 6, since the input device has a function of deaerating the air contained in the raw material biomass, the accompanying air accompanying the input of the raw material to the anaerobic fermentation tank is suppressed, and a good anaerobic fermentation environment is achieved. Realized.

  According to the invention of claim 7, since air and water vapor supplied into the hollow fixed shaft of the anaerobic fermenter through the aerobic fermenter are released from the end of the hollow fixed shaft to the atmosphere through the deodorizing device 3. The contents of the aerobic fermenter do not directly touch the outside air, and the odor problem can be minimized.

  Below, an example of design calculation of a continuous dry biomass gasification plant according to the present invention with a garbage disposal capacity of 20 t / day is shown. In addition, the following numerical values assume the steady operation state of this plant, and do not include the unsteady state at the beginning of operation.

  If the moisture content of raw garbage is 70 wt%, anaerobic fermentation period is 20 days, and anaerobic fermentation period is 13 days, anaerobic fermentation residue generation amount = 16.15 t / day (of which solid content is 2.15 t / day, moisture is 14 t / day: water content Rate 86.7 wt%), aerobic fermentation residue (compost) generation amount = 2.52 t / day (of which solid content 1.89 t / day, moisture 0.63 t / day: moisture content 25 wt%). The above 16.15 t / day corresponds to the amount of the anaerobic fermentation residue described as “constant time ratio” in claim 1. It is important for safety to transport this amount as uniformly and continuously as possible.

  Of the solid content 6 t / day and the water content 14 t / day brought from the raw material biomass, the water passes through the anaerobic fermentation tank 6 as it is, and the solid content is converted into gas and reduced to about 2.15 t / day. A small amount of water is separated as drain during the transfer by the intermediate transfer device 10, but this is recovered in the drain tank 11 and returned to the anaerobic fermentation tank 6, so the total water content does not change.

  The 14t / day water passing through the anaerobic fermenter 6 is transferred to the aerobic fermenter 13 as it is, and forced aeration (including hot air by the hot air generator 15) by the forced aeration blower 14 is carried out. Almost all of the input water evaporates due to the heat of fermentation of thermophilic bacteria (50 to 65 ° C.), and the solid content of 2.15 t / day is also slightly reduced by aerobic fermentation. As a result, an aerobic fermentation residue (compost) having a solid content of 1.89 t / day and a residual water content of 0.63 t / day (water content 25 wt%) is obtained. Note that a part of the compost may be returned to the charging device 1 in response to fluctuations in the moisture content of the raw material biomass.

  Water vapor generated in the aerobic fermenter 13 is collected together with air and sent into the hollow fixed shaft of the anaerobic fermenter 6, but passes through it with almost no condensation, and is diffused to the atmosphere through the deodorizing device 3. Is done.

If the basic unit of methane gas generation is 110 m ³ / t, the gas generation rate is 2,200 m ³ / day. Among them, the amount of gas home consumption to moisture evaporation fuel in aerobic within the fermentation tank 13 because there at 137m ³ / day from heat calculation, the surplus gas amount is 2,063m ³ / day. The power generation unit is 1.8 kwh / m ³ , and the amount of power generated by surplus gas is 3,713 kwh / day. Since the power consumption of the facility in the plant is estimated to be about 1,130 kwh, it is possible to perform external power selling by subtracting about 2,582 kwh / day.

The specifications, dimensions, and number of major equipment are as follows. This plant is equipped with three main facilities, three of which are operated in parallel.
(1) Charger capacity = 5 t / h × 3 units (2) Anaerobic fermenter capacity = 678 m ³ = φ3 m × L32 m × 3 units (3) Aerobic fermenter capacity = 103 m ³ = φ2.5 m × L7 m × 3 units (4) Hot air generator capacity = 60,000 kcal / h × 3 units (5) High pressure blower capacity = 5.5 kw × 3 units (6) Sealed intermediate transfer device = φ300 mm × L1.5 m × 3 units (7) Gas holder capacity = 10m ³
(8) Product discharge device = φ300 mm × L1 m × 3 units (9) Weighing bagging device Hopper capacity = 3 m ³

  Since the present invention relates to a continuous dry biomass gasification plant for anaerobic methane fermentation of raw garbage, organic waste, etc., all industries that emit organic waste, especially agriculture, fishery, livestock, food processing, It contributes to the development of many industries such as sales and distribution, and can contribute to the activities of local governments that handle garbage.

It is a conceptual diagram which shows the structure of the continuous dry biomass gasification plant which concerns on this invention. It is a block diagram which shows the process flow of the continuous dry biomass gasification plant which concerns on this invention. It is a figure which shows the sliding packing in both anaerobic and aerobic fermenters.

Explanation of symbols

1: Input device 2: Degassing tank 3: Deodorizing device 4: Vacuum pump 5: Induction fan 6: Anaerobic fermentation tank 7: Gas holder 8: Gas suction blower 9: Gas tank 10: Intermediate transfer device 11: Drain tank 12: Drain pump 13: Aerobic fermenter 14: Forced ventilation blower 15: Hot air generator 16: Separation discharge device 17: Measuring bagging device 18: Support chamber 19: Rotating cylinder 20: Sliding packing

Claims (7)

A horizontal cylindrical rotating machine that pulverizes and mixes raw biomass and continuously feeds it into an anaerobic fermenter, and the barrel is rotatably supported by support chambers at both ends, mechanically sealed from the outside air, and equipped with stirring means An anaerobic fermenter consisting of a torso,
An aerobic fermenter comprising a horizontal cylindrical rotating body that is rotatably supported by support chambers at both ends, mechanically sealed from outside air, and provided with stirring means and forced ventilation means;
It is equipped with an intermediate transfer device that combines anaerobic and aerobic fermenters in tandem and transfers anaerobic fermentation residues to the aerobic fermenters, and a discharge device that continuously discharges the fermentation residues from the aerobic fermenters,
The raw material biomass is decomposed in the anaerobic fermentation tank to generate flammable gas such as methane, and the generated gas is supplied to the outside of the anaerobic fermentation tank .
An anaerobic fermentation residue is further aged in an aerobic fermentation tank, composted , and a continuous dry biomass gasification plant that supplies the composted fermentation residue to the outside,
In order not to form a partial mass that maintains anaerobic fermentation inside the aerobic fermentation tank, the intermediate transfer device continuously transfers the anaerobic fermentation residue into the aerobic fermentation tank at a constant time rate. The gasification plant.   Mechanical sealing in both the anaerobic and aerobic fermenters is achieved by a sliding packing made of a rubber-like elastic body inserted between the cylindrical inner wall surface of the support chamber and the end surface of the horizontal cylindrical rotary body. The gasification plant according to claim 1.   The anaerobic and aerobic fermenters each have a hollow fixed shaft laid between the support chambers at both ends along the axis, respectively, and by stirring blades provided on the surface of the hollow fixed shaft and the wall surface of the rotating body, The gasification plant according to claim 1, wherein the tank contents are conveyed from the upstream to the downstream of the tank as a whole while being stirred. The aerobic fermenter is equipped with a blower device for forced ventilation and a gas-fired hot air generator, and the air from the blower device or hot air generator accelerates the evaporation of excess water at the same time as supplying oxygen into the tank. Depending on the temperature of the aerobic fermenter content can be adjusted,
Collect the air and water vapor warmed by fermentation heat in the aerobic fermenter, supply this air etc. into the hollow fixed shaft of the anaerobic fermenter, and if necessary, the surface of the hollow fixed shaft and the fixed stirring blade group The gasification plant according to claim 3, wherein the contents of the anaerobic fermenter can be indirectly heated with the heat transfer surface as a heat transfer surface.   The gasification plant according to claim 4, wherein the air and water vapor supplied into the hollow fixed shaft of the anaerobic fermenter are discharged from the end thereof to the atmosphere through a deodorizing device.   The gasification plant according to claim 1, wherein the charging device has a function of deaerating air contained in the raw material biomass. The gasification plant according to claim 1, wherein the intermediate transfer device has a function of collecting drain from the anaerobic fermentation residue, and the collected drain is sprayed into the anaerobic fermentation tank.

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