JP2017018921A - Methane fermentation method and methane fermentation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a methane fermentation method and a methane fermentation apparatus which suitably supply heat quantity consumption of a plant with energy other than hot blast generated by directly combusting biogas.SOLUTION: A methane fermentation method includes: a methane fermentation step for performing methane fermentation of fermentation raw material including litter and organic waste in a methane fermentation tank; a solid-liquid separation step for separating methane fermentation residue from digestion liquid produced in the methane fermentation step; a drying step for drying the methane fermentation residue separated in the solid-liquid separation step; and a combustion step for combusting the dried methane fermentation residue obtained by drying the fermentation residue inn the drying step. Therein, combustion discharge gas generated by combusting the dried methane fermentation residue in the combustion step or a heat medium thermally recovered from the combustion discharge gas is used as a heat source for drying the methane fermentation residue in the drying step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a methane fermentation method and a methane fermentation apparatus, and more particularly to a methane fermentation method and a methane fermentation apparatus that are excellent in heat utilization efficiency.

  In Patent Document 1, biogas is produced by methane fermentation of garbage, and the biogas is supplied to a gas generator to produce electric power. At this time, the waste heat of the gas generator is used to heat the methane fermentation tank and dry the dewatered digested sludge. Patent Document 1 states that the dehydrated digested sludge may be dried by hot air generated by directly burning biogas.

Japanese Patent Laid-Open No. 10-316982

  However, it was found that heating the methane fermentation tank and drying the dehydrated digested sludge with the waste heat of the gas generator is difficult depending on the type and properties of the fermentation raw materials, weather conditions, and operating conditions of the equipment. . This is because the amount of heat is insufficient. In particular, when assuming operation in a cold region, a shortage of heat tends to increase.

  In order to make up for such a shortage of heat, when biogas is directly combusted as described in Patent Document 1, the biogas supplied to the gas generator is reduced, and the power produced is reduced. Biogas has a high commercial value and can be used for power generation as well as gas and biogas boilers. Therefore, it is effective to directly burn this to make up for the lack of heat in the methane fermentation process. There are some disadvantages.

  Then, the subject of this invention is providing the methane fermentation method and methane fermentation apparatus which can cover plant consumption calorie | heat amount suitably with energy other than the hot air generated by directly burning biogas.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

(Claim 1)
A methane fermentation process in which fermentation raw materials including bedding and organic waste are methane fermented in a methane fermentation tank;
A solid-liquid separation step for separating the methane fermentation residue from the digestive juice produced in the methane fermentation step;
A drying step of drying the methane fermentation residue separated in the solid-liquid separation step;
A combustion step of burning the dried methane fermentation residue obtained by drying in the drying step,
Combustion exhaust gas generated by burning the dry methane fermentation residue in the combustion step or a heat medium recovered from the combustion exhaust gas is used as a heat source for drying the methane fermentation residue in the drying step. .

(Claim 2)
A combustion exhaust gas generated by burning the dry methane fermentation residue in the combustion process or a heat medium recovered from the combustion exhaust gas is further used as a heat source for heating the methane fermentation tank in the methane fermentation process. The methane fermentation method according to claim 1.

(Claim 3)
A sterilization step of sterilizing the digested liquid from which the methane fermentation residue was separated in the solid-liquid separation step;
A concentration step of concentrating the digested liquid sterilized in the sterilization step, and
Combustion exhaust gas generated by burning the dry methane fermentation residue in the combustion process or a heat medium recovered from the combustion exhaust gas is further used as a heat source for sterilization in the sterilization process and a heat source for concentration in the concentration process. The methane fermentation method according to claim 1 or 2, characterized in that

(Claim 4)
The methane fermentation method according to any one of claims 1 to 3, wherein a part of the dry methane fermentation residue is recovered as a bedding material.

(Claim 5)
A methane fermentation tank for methane fermentation of fermentation raw materials including bedding and organic waste;
A solid-liquid separator for separating the methane fermentation residue from the digested liquid produced in the methane fermentation tank;
A dryer for drying the methane fermentation residue separated by the solid-liquid separator;
A combustion apparatus for burning dry methane fermentation residue obtained by drying with the dryer,
A combustion exhaust gas generated by burning the dry methane fermentation residue in the combustion apparatus, or a pipe for transferring a heat medium recovered from the combustion exhaust gas to the dryer, and the combustion exhaust gas or the heat medium is transferred to the dryer A methane fermentation apparatus characterized in that it is used as a heat source for drying methane fermentation residues.

(Claim 6)
A combustion exhaust gas generated by burning the dry methane fermentation residue in the combustion device or a pipe for transferring a heat medium recovered from the combustion exhaust gas to the methane fermentation tank, further comprising the combustion exhaust gas or the heat medium The methane fermentation apparatus according to claim 5, wherein the methane fermentation apparatus is used as a heat source for heating a methane fermentation tank.

(Claim 7)
A sterilization tank for sterilizing the digested liquid from which the methane fermentation residue is separated by the solid-liquid separator;
A concentration tank for concentrating the digested liquid sterilized in the sterilization tank,
Combustion exhaust gas generated by burning the dry methane fermentation residue in the combustion device or a pipe for transferring a heat medium recovered from the combustion exhaust gas to the sterilization tank and a pipe for transferring to the concentration tank, The methane fermentation apparatus according to claim 5 or 6, wherein the exhaust gas or the heat medium is further used as a heat source for sterilization in the sterilization tank and a heat source for concentration in the concentration tank.

(Claim 8)
The methane fermentation apparatus according to any one of claims 5 to 7, wherein a part of the dry methane fermentation residue is recovered as a bedding material.

  ADVANTAGE OF THE INVENTION According to this invention, the methane fermentation method and methane fermentation apparatus which can cover a plant consumption calorie | heat amount suitably with energy other than the hot air generated by burning biogas directly can be provided.

The figure explaining an example of the methane fermentation apparatus for enforcing the methane fermentation method of this invention The graph which shows the result of an Example and a comparative example (heat balance 1) The graph which shows the result of an Example and a comparative example (heat balance 2) The graph which shows the result of an Example and a comparative example (heat balance 3)

  Below, the form for implementing this invention is demonstrated in detail.

  FIG. 1 is a diagram illustrating an example of a methane fermentation apparatus for carrying out the methane fermentation method of the present invention.

  In FIG. 1, 1 is a digestive juice addition tank, 2 is a first solid-liquid separator, 3 is a crusher, 4 is a mixing tank, 5 is a methane fermentation tank, 6 is a second solid-liquid separator, and 7 is a sterilizer. A tank, 8 is a concentration tank, 9 is a dryer, 10 is a molding machine, 11 is a combustion apparatus, 12 is a biogas storage tank, and 13 is a biogas generator.

  Fermentation raw materials including bedding and organic waste are introduced into the digestive juice addition tank 1. Here, the fermentation raw material is mixed and stirred, and the water content is adjusted. For example, it is preferable to adjust the water content by mixing a digestion liquid or the like described later with the fermentation raw material and stirring.

  As the bedding contained in the fermentation raw material, used bedding that is laid in a breeding space such as livestock is suitable, and it is made of straw made from dried stems of gramineous plants such as rice and wheat. Preferable examples can be given.

  Examples of the organic waste contained in the fermentation raw material include livestock waste, agricultural product residues, food processing residues, and organic sludge.

  Examples of livestock waste include manure from livestock such as cattle, sheep, goats, pigs and horses, and manure from poultry such as laying hens, breeding chickens and broilers.

  Examples of food processing residues include fishery processing residues such as fish scraps and seaweed scraps, meat processing residues including vegetable scraps, fried chicken, etc., bread and ramen scraps, soybeans and starch scraps, and the like.

  Examples of organic sludge include sewage treatment sludge, human waste treatment sludge, septic tank sludge, treatment wastewater treatment sludge generated from food factories, and the like.

  It is particularly preferable that the fermentation raw material contains a bedding in a state where feces such as livestock such as cattle, sheep, goats, pigs and horses, and poultry such as laying hens, breeding chickens and broilers are attached.

  Moreover, it is also preferable that a fermentation raw material contains an energy crop.

  As an energy crop, for example, herbaceous biomass such as Gramineae, Mallowaceae, Cyprinaceae, Brassicaceae, Amaraceae can be preferably exemplified. As grass family biomass, for example, napiergrass, sugarcane, guineagrass, sugarcane, Bermudagrass, perennial ryegrass, sorghum, corn (other than the real part), rice, oat, switchgrass, Giant Miscanthus, Elianthus etc. Can be preferably exemplified. Preferred examples of herbaceous biomass of the mallow family include kenaf and the like. Preferred examples of herbaceous biomass in the family Azoaceae include water hyacinth. Preferred examples of the cruciferous herbaceous biomass include rapeseed. Preferred examples of herbaceous biomass include sugar beet.

  Furthermore, regarding energy crops, “Expectations for Susuki plants as energy crops” (Hokkaido University, Toshihiko Yamada, Journal of the Japanese Society of Grassland Science, 55 (3): 263-269, published date October 2009) can be referred to.

  It is also preferable to use grass for example as an energy crop.

  The fermentation raw material whose moisture has been adjusted is introduced into the first solid-liquid separator 2. Here, it isolate | separates into the solid part containing a litter, and a slurry part.

  The solid content including the bedding is introduced into the crusher 3. Here, the litter is crushed and fragmented. For example, in the case where the fermentation raw material contains a bedding in a state where feces are attached, since the feces are peeled from the bedding by the solid-liquid separation described above, the crushing efficiency of the bedding can be improved.

  The fragmented bedding is introduced into the mixing tank 4 and mixed with the slurry separated by the first solid-liquid separator 2.

  The fermentation raw material passed through the mixing tank 4 is introduced into the methane fermentation tank 5. Here, the fermentation raw material is subjected to methane fermentation to produce a digestive juice. Biogas is generated along with such methane fermentation.

  The temperature of the methane fermentation tank 5 is adjusted to a temperature higher than the outside air, specifically, a temperature range suitable for inhabiting the methanogen. For example, the temperature is maintained in the range of about 32-37 ° C. for medium temperature fermentation, about 52-55 ° C. for high temperature fermentation, and about 60-70 ° C. for ultra high temperature fermentation. As a heat source for heating the methane fermentation tank 5, the amount of heat generated by the combustion device 11 described later can be suitably used.

  The fragmented litter not only suitably contributes to the production of methane gas during methane fermentation, but also can generate sufficient thermal energy by solid-liquid separation, drying and burning of the litter fermentation product.

  The digested liquid after methane fermentation is introduced into the second solid-liquid separator 6. Here, the methane fermentation residue is separated from the digestive juice. The methane fermentation residue contains fermented bedding (sometimes referred to as bedding fermented material).

  A part of the digested liquid separated from the methane fermentation residue by the second solid-liquid separator 6 is returned to the digested liquid addition tank 1 described above, and can be used for adjusting the water content of the fermentation raw material. The remaining digestive juice is preferably sterilized and concentrated as described below from the viewpoint of increasing the added value of liquid fertilizer and the like.

  First, in the sterilization tank 7, it is preferable to heat the digestion liquid and perform sterilization treatment. As a heat source of the sterilization tank 7, the amount of heat generated by the combustion device 11 described later can be suitably used.

  Furthermore, the digestive juice can be introduced into the concentration tank 8. In the concentration tank 8, it is preferable to heat the digested liquid and perform the concentration treatment. As the heat source of the concentration tank 8, the amount of heat generated by the combustion device 11 to be described later can be suitably used.

  The digested liquid that has been subjected to sterilization and concentration treatment as described above can be suitably used as liquid fertilizer and the like because it has good storage stability and nutrients are concentrated.

  On the other hand, the methane fermentation residue obtained by the second solid-liquid separator 6 is introduced into the dryer 9. Here, the moisture contained in the methane fermentation residue is evaporated and dried. By drying in the dryer 9, the water content of the methane fermentation residue is preferably reduced to 70% or less, more preferably 60% or less. By making the water content of the methane fermentation residue 70% or less, self-combustion is possible, and thus combustion in the subsequent combustion apparatus 11 can be stabilized. If the water content is 60% or less, the combustion is further stabilized. Most preferably, the moisture content of the methane fermentation residue is in the range of 50% or more and 60% or less by drying in the dryer 9, whereby the methane fermentation residue after drying (sometimes referred to as dry methane fermentation residue) While stabilizing combustion, the usage-amount of the heat source of the dryer 9 can be suppressed. As the heat source of the dryer 9, the amount of heat generated by the combustion device 11 described later can be suitably used.

  The dry methane fermentation residue obtained by the dryer 9 can also be recovered as a bedding. That is, the dry methane fermentation residue contains a fermented bedding material, and the fermented bedding material can be suitably reused as a bedding material.

  The remaining dry methane fermentation residue obtained by the dryer 9 is introduced into the molding machine 10. Here, the dry methane fermentation residue is formed by compression molding or the like. It is preferable to granulate the dry methane fermentation residue into, for example, pellet fuel. The dry methane fermentation residue containing the fermented bedding is excellent in the function as a fuel. Although the molding machine 10 can be omitted as appropriate, it is preferable to perform molding by the molding machine 10 from the viewpoint of improving the storage stability and handling properties of the dry methane fermentation residue as a fuel.

  The dry methane fermentation residue molded by the molding machine 10 is introduced into the combustion device 11. When omitting the molding machine 10, the dry methane fermentation residue obtained by the dryer 9 may be introduced into the combustion device 11.

  The combustion apparatus 11 may be anything that can burn dry methane fermentation residue, and a biomass boiler, an incinerator, and the like can be preferably exemplified, but is not limited thereto.

  In the combustion apparatus 11, high temperature combustion exhaust gas is produced | generated by burning a dry methane fermentation residue. Further, heat may be recovered from the combustion exhaust gas to a heat medium. As the heat medium, hot water or steam can be preferably exemplified.

  As will be shown later in the examples, the amount of heat of the combustion exhaust gas or heat medium obtained can suitably cover not only the drying of the methane fermentation residue by the dryer 9 but also the amount of heat necessary for heating the methane fermentation tank 5. Further, it was found that even when used as a heat source for heating in the sterilization tank 7 and the concentration tank 8, there is still a surplus. Therefore, it is possible to obtain an effect that can sufficiently cover the amount of heat consumed by the plant without directly burning biogas having a high commercial value.

  In the example of FIG. 1, the combustion exhaust gas or heat medium generated from the combustion device 11 is transferred to the dryer 9 via the pipe L1, transferred to the methane fermentation tank 5 via the pipe L2, and sterilized via the pipe L3. It transfers to the tank 7, and it is made to transfer to the concentration tank 8 via the piping L4. It is not limited to this example, For example, it can also supply to the other calorie | heat amount consumption site | parts in a plant via additional piping.

  It was found that the bedding not only contributes to biogas generation in methane fermentation, but also has high combustion heat after fermentation. Therefore, the bedding fermented product is contained in the dry methane fermentation residue, so that it can be burned to cover the plant consumption heat with a margin. Therefore, the fermented material in the remaining methane fermentation residue remaining as a fuel can be suitably allocated for reuse as a bedding or the like. That is, according to the present invention, it is possible to preserve the surplus of the dry methane fermentation residue containing the fermented bedding, and improve the degree of freedom to set the amount used as fuel and the amount used as bedding, etc. You can also. Moreover, these usage-amounts can also be set according to a season etc. For example, the setting of increasing the amount of fuel used in the winter when the temperature is low can be suitably performed.

  The biogas produced in the methane fermentation tank 5 can be stored in the biogas storage tank 12 after being subjected to a purification treatment such as desulfurization as necessary.

  As described above, biogas has a high commercial value. For example, in addition to power generation, gas and biogas boilers can be used. In the example of FIG. 1, a case is shown where power is generated by introducing biogas from the biogas storage tank 12 to the biogas generator 13. At this time, it is also preferable to recover waste heat from the biogas generator 13. The waste heat from the biogas generator 13 includes the waste heat of the high-temperature exhaust gas exhausted from the biogas generator 13 or the waste heat recovered in the cooling water for cooling the heat generating part of the biogas generator 13. Can be preferably exemplified. It is also preferable that these waste heat is recovered in hot water or the like and used in the plant together with the amount of heat generated by the combustion of the dry methane fermentation residue described above, for example, via the pipe L5 (generator waste heat utilization line) in FIG. It is.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Comparative Example 1)
Using a device similar to the methane fermentation device shown in FIG. 1, a raw material (TS (Total Solids; total evaporation residue) 12%) made of feces and urine without mixing bedding is supplied at a supply rate of 100 t / day. Processed.

Example 1
Using a device similar to the methane fermentation apparatus shown in FIG. 1, a raw material (TS 24%) obtained by mixing 10% by weight of a bedding into manure is supplied at a supply rate of 100 t / day for processing. .

(Example 2)
Using an apparatus similar to the methane fermentation apparatus shown in FIG. 1, the energy crop (TS 85%) is further mixed with the manure mixed with 10% by weight of the bedding (TS 24%). The raw material was supplied and processed at a supply rate of 100 t / day. Here, the supply amount of the manure mixed with bedding is 90 t / day, and the supply amount of the energy crop is 10 t / day.

<Evaluation method and evaluation>
(1) Heat balance 1
In the above Comparative Example 1 and Examples 1 and 2, a graph of the heat balance when "generator waste heat" is considered as the plant generated heat amount and "fermentor heating heat amount" is considered as the plant consumed heat amount It was shown in 2. “Generator waste heat” is waste heat recovered from the biogas generator, and “fermentor heating heat quantity” is a heat quantity necessary for heating the methane fermentation tank.

  From FIG. 2, depending on the composition of raw materials and climatic conditions, the heating heat quantity of the fermenter may not be able to be covered by only the generator waste heat as in Comparative Example 1.

(2) Heat balance 2
In Comparative Example 1 and Examples 1 and 2 described above, “generator waste heat” and “boiler fuel heat amount” are considered as the plant generated heat amount, and “fermentor heating heat amount” and “for dryer” are used as the plant consumed heat amount. A graph of the heat balance in the case of considering “amount of heat” is shown in FIG. “Boiler fuel calorie” is the calorie of the dry methane fermentation residue, and “Dryer calorie” is the calorie necessary for drying the methane fermentation residue. The methane fermentation residue of Example 1 includes a bedding, and the methane fermentation residue of Example 2 includes an energy crop in addition to the bedding. The methane fermentation residue of Comparative Example 1 does not contain bedding or energy crops.

  From FIG. 3, by drying the methane fermentation residue into fuel and using it as a heat source, it is possible to secure the fermenter heating and the heat source for drying under any raw material conditions.

(3) Heat balance 3
In Comparative Example 1 and Examples 1 and 2 above, “generator waste heat” and “boiler fuel heat amount” are taken into account as the plant generated heat amount, and “fermentor heating heat amount” and “for dryer” are used as the plant consumed heat amount. FIG. 4 shows a graph of the heat balance in the case of considering “amount of heat”, “amount of heat for sterilization tank” and “amount of heat for concentration tank”. “The amount of heat for the sterilization tank” is the amount of heat necessary for the heat sterilization of the digestive liquid in the sterilization tank, and “the amount of heat for the concentration tank” is the amount of heat necessary for the heat concentration of the digestion liquid in the concentration tank.

  4, in Examples 1 and 2, it is possible to cover the amount of heat for sterilization and concentration of digestive juice with the amount of heat remaining in the heat balance of FIG. 3. If there is still a surplus of heat, it can be sold as reclaimed bedding to dairy farmers in areas other than this methane fermentation facility by producing more litter.

1: Digestive liquid addition tank 2: First solid-liquid separator 3: Crusher 4: Mixing tank 5: Methane fermentation tank 6: Second solid-liquid separator 7: Sterilization tank 8: Concentration tank 9: Dryer 10 : Molding machine 11: Combustion device 12: Biogas storage tank 13: Biogas generator L1-L5: Piping

Claims (8)

A methane fermentation process in which fermentation raw materials including bedding and organic waste are methane fermented in a methane fermentation tank;
A solid-liquid separation step for separating the methane fermentation residue from the digestive juice produced in the methane fermentation step;
A drying step of drying the methane fermentation residue separated in the solid-liquid separation step;
A combustion step of burning the dried methane fermentation residue obtained by drying in the drying step,
Combustion exhaust gas generated by burning the dry methane fermentation residue in the combustion step or a heat medium recovered from the combustion exhaust gas is used as a heat source for drying the methane fermentation residue in the drying step. .   A combustion exhaust gas generated by burning the dry methane fermentation residue in the combustion process or a heat medium recovered from the combustion exhaust gas is further used as a heat source for heating the methane fermentation tank in the methane fermentation process. The methane fermentation method according to claim 1. A sterilization step of sterilizing the digested liquid from which the methane fermentation residue was separated in the solid-liquid separation step;
A concentration step of concentrating the digested liquid sterilized in the sterilization step, and
Combustion exhaust gas generated by burning the dry methane fermentation residue in the combustion process or a heat medium recovered from the combustion exhaust gas is further used as a heat source for sterilization in the sterilization process and a heat source for concentration in the concentration process. The methane fermentation method according to claim 1 or 2, characterized in that   The methane fermentation method according to any one of claims 1 to 3, wherein a part of the dry methane fermentation residue is recovered as a bedding material. A methane fermentation tank for methane fermentation of fermentation raw materials including bedding and organic waste;
A solid-liquid separator for separating the methane fermentation residue from the digested liquid produced in the methane fermentation tank;
A dryer for drying the methane fermentation residue separated by the solid-liquid separator;
A combustion apparatus for burning dry methane fermentation residue obtained by drying with the dryer,
A combustion exhaust gas generated by burning the dry methane fermentation residue in the combustion apparatus, or a pipe for transferring a heat medium recovered from the combustion exhaust gas to the dryer, and the combustion exhaust gas or the heat medium is transferred to the dryer A methane fermentation apparatus characterized in that it is used as a heat source for drying methane fermentation residues.   A combustion exhaust gas generated by burning the dry methane fermentation residue in the combustion device or a pipe for transferring a heat medium recovered from the combustion exhaust gas to the methane fermentation tank, further comprising the combustion exhaust gas or the heat medium The methane fermentation apparatus according to claim 5, wherein the methane fermentation apparatus is used as a heat source for heating a methane fermentation tank. A sterilization tank for sterilizing the digested liquid from which the methane fermentation residue is separated by the solid-liquid separator;
A concentration tank for concentrating the digested liquid sterilized in the sterilization tank,
Combustion exhaust gas generated by burning the dry methane fermentation residue in the combustion device or a pipe for transferring a heat medium recovered from the combustion exhaust gas to the sterilization tank and a pipe for transferring to the concentration tank, The methane fermentation apparatus according to claim 5 or 6, wherein the exhaust gas or the heat medium is further used as a heat source for sterilization in the sterilization tank and a heat source for concentration in the concentration tank.   The methane fermentation apparatus according to any one of claims 5 to 7, wherein a part of the dry methane fermentation residue is recovered as a bedding material.

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