JP4541245B2 - Dry methane fermentation - Google Patents

Description

  The present invention relates to dry methane fermentation and wet dry combined methane fermentation for methane fermentation of biomass such as organic waste.

  As a method for recovering energy from biomass such as organic waste, there is a method using methane fermentation. Methane fermentation refers to wet methane fermentation performed on liquid biomass in which the ratio of solids (TS concentration) is 10% or less, and solids are, for example, 10% or more, more typically 20% or more. Dry methane fermentation is known in which methane fermentation is performed without adding water to biomass such as organic waste that occupies a high proportion.

  Wet methane fermentation has a long history and many achievements, and is a nearly completed technology, but it has the following problems.

  A. Processing of a large amount of fermentation waste liquid discharged during wet methane fermentation requires a large amount of expenses including initial costs and operation costs. Moreover, in order to accelerate | stimulate fermentation, it is necessary to stir and the stirring energy is also required.

  When the ratio of solids is high, in order to use wet methane fermentation, it is diluted by adding a liquid such as water to form a slurry. However, due to this addition of water, the treatment capacity increases, resulting in poor treatment efficiency. Furthermore, the added liquid must eventually be treated as waste water.

C) Fermentation residue with high water content (about 95%) generated by wet methane fermentation is separated into solid and liquid using a dehydrator, except that it is used as liquid fertilizer, and the liquid is processed at a wastewater treatment plant. , Discharged into nearby rivers and sewers. On the other hand, solids or dehydrated cakes are composted and sold in a composting system, or disposed of in landfills or incineration. When livestock manure containing a lot of persistent organic matter such as rice straw is treated by wet methane fermentation (this is the most common case), there is a limit on the decomposition rate in the fermentation period of about 30 days (40-45% The decomposition rate is the actual state), and the fermentation residue still contains a lot of unfermented organic components. For this reason, the aforementioned dehydrated cake is a biomass rich in organic components. Composting system with aerobic fermentation of organic matter of dehydrated cake, a process of converting into C0 ₂ and H _{2 0,} the process consumes energy rather stirring and turning back the like without any contribution to the energy recovery.

  On the other hand, in dry methane fermentation, the biomass to be fermented can be processed without dilution, so that the processing capacity does not increase, the moisture content of the fermentation residue is low, and the fermentation waste liquid treatment is unnecessary. This makes the entire system easy to handle and simple. Therefore, dry methane fermentation has the advantage that the initial cost can be reduced compared to wet methane fermentation. However, although dry methane fermentation has a track record with technology developed in Europe a few decades ago, it is a future technology that still requires technological development, and various proposals have been made.

  For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2002-320949), in order to prevent inhibition of methane fermentation by ammonia or the like, an organic porous material is mixed with an inorganic porous material and introduced into a methane fermentation tank. A methane fermentation process is disclosed.

  Conventionally, in the methane fermentation method, when processing organic sludge with high nitrogen content such as dehydrated cake of activated sludge, okara, manure, etc., it is known that methane fermentation inhibition will be caused if the ammonia nitrogen concentration is high. ing. In the case of wet methane fermentation, the nitrogen concentration can be lowered relatively easily because it is diluted with water, but in the case of dry methane fermentation, the solid concentration is high, that is, the organic matter concentration is high, so the nitrogen concentration is also high. Therefore, there is a great risk of inhibition of methane fermentation by ammonia nitrogen. For this reason, there are limits to the types of biomass to be processed in dry methane fermentation compared to wet methane fermentation. Patent document 1 is going to solve such a problem.

  In Patent Document 2 (Japanese Patent Laid-Open No. 2003-53309), an organic solid waste is subjected to an anaerobic digestion treatment using anaerobic digested sludge containing some photosynthetic bacteria together with methane-fermenting microorganisms under light irradiation conditions. It is disclosed. The invention of Patent Document 2 also attempts to reduce the ammonia concentration.

  Patent Document 3 (Japanese Patent Application Laid-Open No. 2004-188392) discloses that quick lime is added to an organic waste to perform an alkali reaction step as a pretreatment when the organic waste is processed by dry methane fermentation. Has been. The present invention seeks to promote organic waste volume reduction, solubilization and deammonification.

  Patent Document 4 (Japanese Patent Laid-Open No. 2002-52398) discloses that carbon is mixed with methane fermentation sludge and then carbonized. This invention is intended to efficiently process and reuse fermentation residues.

  Also, apart from methane fermentation, coal was gasified for a long time and was put to practical use, but it was inefficient and was deprived of the market by oil and natural gas. However, triggered by the oil crisis, coal gasification research and development is being carried out around the world with the aim of increasing efficiency. These gasifications are gasifications by chemical reactions under conditions of high temperature and high pressure, and the plant is complicated and dangerous and requires strict operation management. Naturally, the plant becomes large and requires a large amount of construction cost.

Low-grade coal, such as low-rank coal (sub-bituminous coal, lignite, lignite) and peat, is distributed and buried worldwide, but currently it is not used effectively, and its biogasification In fact, research was conducted in the NEDO International Joint Research Proposal Project in 2000, but no results have been obtained.
JP 2002-320949 A JP 2003-53309 A JP 2004-188392 A JP 2002-52398 A JP 2003-19491 A JP 2002-102828 A

  Since organic wastes to be treated for methane fermentation generally have a high moisture content, the energy density is very low. For this reason, it is said that it is economically disadvantageous to implement methane fermentation from the viewpoint of energy recovery. By the way, when comparing dry methane fermentation and wet methane fermentation from the viewpoint of energy recovery, dry methane fermentation does not require treatment of fermentation residues, that is, wastewater treatment that consumes a large amount of energy is unnecessary, so that Compared to this, more energy can be supplied outside the system (outside the plant).

  However, in the conventional dry methane fermentation treatment, energy recovery is not yet fully considered.

  An object of this invention is to provide the dry methane fermentation method which can increase recovery energy rather than the conventional dry methane fermentation method. For this purpose, the amount of biogas generated is increased and the recovery energy is increased by improving the decomposition rate of the fermentation object. Furthermore, the present invention aims to reduce the volume of waste to be treated by improving the decomposition rate.

  In addition, there is a C / N ratio (biodegradable carbon content / biodegradable nitrogen content) as an index for determining fermentation characteristics of methane fermentation, but the amount of biodegradable carbon that is a substrate for methane fermentation is biodegradable nitrogen. If the amount is less than the appropriate amount, the amount of methane generated decreases, and conversely, even if the amount of carbon is more than the appropriate amount, methane fermentation tends to be inhibited. In general, biomass (organic waste, etc.), which is an object of dry methane fermentation treatment, contains a lot of nitrogen, but the present invention adjusts the amount of biodegradable carbon in the fermentation object regardless of the amount of nitrogen. It aims at avoiding methane fermentation inhibition by ammonia nitrogen and optimizing the C / N ratio.

  The present inventor has shown that the organic composition of biomass (organic waste, etc.) is composed of carbohydrates, fats, and proteins, and the retained energy is 16 kJ / g for carbohydrates, 37 kJ / g for fats, and 17 kJ / g for proteins. The retained energy of fat is more than twice that of carbohydrates and proteins, and the amount of biogas generated is 790 ml / g for carbohydrates, 1,250 ml / g for fats, and 704 ml / g for proteins. It was noted that it is 1.5 times more than carbohydrates and proteins.

  Fats and oils are hydrophobic substances, have a strong tendency to form levitating fats and oils in liquids, and are hardly decomposed by microorganisms. For this reason, oils and fats have been conventionally considered difficult to be subjected to methane fermentation treatment, but Patent Document 5 (Japanese Patent Laid-Open No. 2003-19491) discloses organic waste slurries such as garbage as a dispersant for fats and oils. It has been proposed that oil and fat be decomposed by anaerobic microorganisms in a methane fermentation tank having a TS concentration of 3 to 7% in the tank by mixing with the oil and fat and improving the dispersibility of the oil and fat. In Patent Document 6 (Japanese Patent Laid-Open No. 2002-102828), solid organic waste such as garbage and fat-containing waste are mixed in a tempering tank and heated to solubilize the fat. It has been proposed that this liquid mixture be subjected to methane fermentation treatment so that the TS concentration is about 3 to 6% in the methane fermentation tank.

  However, the methods disclosed in these Patent Documents 5 and 6 are intended to treat organic waste containing fats and oils, and are not actively utilizing fats and oils. The treatment method is a conventional wet methane fermentation method.

  Another object of the present invention is to effectively utilize low-grade coal such as low-coalized coal (subbituminous coal, lignite, lignite) and peat, and to obtain biogas from these.

  As a result of earnest research to solve the above problems, the present inventor has found that the object of the present invention can be achieved by actively utilizing fats and oils in the dry methane fermentation method, and has made the present invention. It is.

  That is, the present invention is a method of subjecting a fermentation object to a dry methane fermentation treatment, wherein the fermentation object contains fats and oils, the ratio of the fats and oils to the total amount of the fermentation objects is 3 to 15% by mass, and methane The fermented product from the fermenter is mixed with the fermentation object as seed sludge, the mixture is introduced into the methane fermenter, and the total solid concentration in the methane fermenter is 25% or more. It is a dry methane fermentation method.

  In this case, the fermentation object contains fats and oils and a low water content, and all the fermentation objects and seed sludge may be mixed at one time, or preferably the fats and oils are mixed with the low water content and impregnated. After that, it may be performed in two stages of mixing the oil-impregnated low water-containing substance, other fermentation object and seed sludge.

  In the present invention, the low moisture content includes plant biomass and animal biomass having a moisture content of 15% or less, preferably 10% or less, or low coal content coal (for example, subbituminous coal). Moreover, the low water content substance which already contains fats and oils, such as waste clay, can also be utilized.

  Moreover, in this invention, the fermentation target object may contain fats and oils and peat. When peat or low-coalized coal is used, energy recovery can be measured more efficiently by drying the fermentation residue from the dry methane fermenter to obtain a fuel or cement fired material.

  In addition, the present invention is a method for treating a fermentation object using a wet methane fermentation method and a dry methane fermentation method in combination, and treating the main fermentation object by a wet methane fermentation method, from a wet methane fermentation tank. The fermentation residue for the dry methane fermentation treatment is mainly composed of the dehydrated cake, and further contains fats and oils and a low water content, and the fats and fats are fermented for the dry methane fermentation treatment. The ratio with respect to the total amount of the object is 3 to 15% by mass, the already fermented product from the dry methane fermentation tank is mixed with the fermentation object for the dry methane fermentation treatment as seed sludge, and the mixture is added to the dry methane fermentation tank. Introduced and achieved the object by a wet dry combined methane fermentation method characterized in that the total solid concentration in the dry methane fermentation tank is 25% or more.

  In this case, preferably, the fermentation residue desorption liquid from the wet methane fermentation tank and the fermentation residue from the dry methane fermentation tank are mixed to form liquid fertilizer.

  According to the present invention, the characteristics of fats and oils are positively utilized in the dry methane fermentation method (that is, it does not happen to be in the waste that is the fermentation target, but the total amount of the fermentation target). It is possible to increase the amount of biogas generated by mixing fats and oils in a ratio of 3 to 15% by mass (the amount of energy held by fats and oils is equivalent to that of fats), and the decomposition rate of the fermentation object Can be improved. As a result, an increase in recovered energy can be measured.

  Fats and oils are hydrophobic and form a floating fat mass in the liquid and are not easily decomposed by microorganisms, but the present invention is not wet methane fermentation, and is a dry type in which the total solid concentration in the methane fermentation tank is 25% or more Based on methane fermentation, if the fermentation object is mixed well, the fats and oils do not harden, the fermentation object can be processed efficiently and wastewater treatment is not required. In this case, since the moisture content of oil and fat is zero, it can be added to the fermentation object without increasing the water content.

  Furthermore, according to the present invention, since the decomposition rate in the dry methane fermentation method can be improved, the waste from the dry methane fermentation tank can be reduced.

In the present invention, fats and oils are actively used. However, since the fats and oils have a nitrogen concentration of zero, it is easy to adjust the ratio of total organic carbon and total nitrogen in the dry methane fermentation method. By doing so, methane fermentation inhibition by ammonia nitrogen can be avoided, methane fermentation can be performed smoothly, and a dry methane fermentation system capable of stable operation can be provided. By utilizing the present invention, the spread of dry methane fermentation can be promoted, and as a result, it can contribute to the reduction of greenhouse gases (CO ₂ problem).

  According to the present invention, the fermentation object contains fats and oils and a low water content, and all the fermentation objects and seed sludge may be mixed at once. However, when the oil and fat is mixed with the low water content and impregnated and then mixed in the oil and fat impregnated low water content material, other fermentation object and seed sludge, the fat and oil is impregnated with the low water content material. Since other fermentation objects and seed sludge are mixed in the state, and therefore, the fats and oils are dispersed uniformly throughout the methane fermentation tank, high biodegradability is obtained, which is preferable.

  Conventionally, biodiesel oil has been commonly used as oil and fat as biomass (vegetable oil such as rapeseed and soybeans, discarded cooking oil, etc.). Compared to the production and use of, it is simple and easy, and can contribute to the expansion of biomass energy use.

  Moreover, according to the present invention, low-grade coal such as low-coalized coal (subbituminous coal, lignite, lignite) or peat can be effectively used, and biogas (methane gas) can be obtained. In this case, there is no need for a large-scale plant like conventional coal gasification, the plant according to the present invention is simple, has almost no danger, is easy to manage, and the construction cost of the plant is low. Become.

  It is preferable to prepare in advance a mixture of fats and oils and a low water content as a fermentation auxiliary material. For example, it is preferable to prepare a mixture of sub-bituminous coal (a kind of low-coalized coal) and fats and oils as a fermentation auxiliary material. If it does in this way, the quantity of fermentation auxiliary material which each requires in many methane gas plants can be supplied easily. Therefore, small-scale methane gas plants can be distributed in various locations where biomass targeted for methane fermentation treatment is generated, and the generated biomass and fermentation auxiliary materials in each methane gas plant are introduced into the fermentor together with seed sludge. Therefore, the plant can be operated efficiently without taking time and effort. In addition, since methane gas plants are distributed in various places, it is effective from the viewpoint of energy security.

  By co-fermenting organic waste such as garbage and dewatered sludge from sewage treatment plants with low-grade coal, waste can be treated and low-grade coal can be used simultaneously.

  Low quality coal with a moisture content of 15% or less is easy to pulverize, and the energy required for pulverization is small compared to other biomass. Moreover, since the low-grade coal has a large specific gravity, the capacity of the dry methane fermentation tank can be reduced.

  In addition, when low-grade coal is used in the present invention, when the fermentation residue is dried, a fuel or cement fired material having a large calorific value can be obtained. This is thought to be because a large amount of fixed carbon is contained in the unfermented portion of coal.

Furthermore, when low grade coal is used in the present invention, a biogas having a very low hydrogen sulfide (H ₂ S) concentration can be obtained.

  According to the present invention, by combining the wet methane fermentation method and the dry methane fermentation method, the biomass to be fermented can be treated very efficiently, and the fermentation residue from the wet methane fermentation tank can be treated in the dry methane fermentation. Therefore, the wastewater treatment plant and the dewatering cake composting plant, which are necessary only in the case of the wet methane fermentation method, are unnecessary, and therefore the equipment can be made compact.

  The present invention is a method for subjecting a fermentation object to a dry methane fermentation treatment. The fermentation object in the present invention is not particularly limited as long as it is biomass that can be fermented by methane bacteria. Examples of the main biomass to be processed among fermentation objects include, for example, sludge dewatering cakes generated at sewage treatment plants, activated sludge dewatering cakes generated at wastewater treatment plants such as food factories, and fermentation residues from wet methane fermentation plants. There are dehydrated cakes. In general, these dehydrated cakes are hardly decomposable organic wastes having a high nitrogen concentration, but can be efficiently decomposed by the method of the present invention.

  The fermentation object in this invention contains fats and oils, and the ratio with respect to the whole quantity of the fermentation objects of fats and oils is 3-15 mass%. Fermentation in the methane fermenter does not work well if the proportion of fat is too much or too little. Examples of the fats and oils used in the present invention include vegetable oils obtained from oily plants such as rapeseed and soybeans, animal fats and oils such as fish oils, waste edible oils such as used tempura oil, and wastewaters such as restaurant streets. There are grease scum of grease traps, drainage of splashed oil and fat generated in the exhaust hood of restaurant kitchens, oil and soot of by-products generated in the edible oil refining process, and mineral oil modified to have the same properties as edible oil and fat .

  In the present invention, the already fermented product from the methane fermentation tank is returned as seed sludge, mixed with all the fermentation objects, and introduced into the methane fermentation tank. In addition, the ratio of each fermentation object and seed sludge is determined in advance so that the total solid concentration in the methane fermentation tank is 25% or more. In this case, when a low water content is included as a fermentation object, it is easy to adjust the total solid concentration. Moreover, you may add water if necessary. The ratio of the whole fermentation object and the seed sludge is preferably about 1: 3 to 8.

  The low water content includes organic components capable of methane fermentation, and has a water content of 15% or less, preferably 10% or less. Bituminous coal). Moreover, the low water content substance which already contains fats and oils, such as waste clay, can also be utilized.

  Specifically, for example, rice husks, dried grass cuttings, shredder paper discharged from offices, rice bran, wheat bran and other by-products in the grain refining process, corn cobs, dried foliage, Examples include dried decoction chips, dried rice straw, wheat straw and the like, dried bagasse, dried fermentation residue of dry methane fermentation, dried grass and other herbs. If necessary, these low water content substances may be crushed to an appropriate size that can be fermented, or even finely ground to an appropriate size that can be fermented even if already in a pulverized state. . For example, rice bran, corn cobs, dried foliage, dried rice straw, wheat straw and the like are preferably used after being pulverized.

  Examples of low coal coal with a low water content include sub-bituminous coal, lignite, and lignite. This is finely powdered and used. Moreover, in this invention, although a moisture content is high, peat can also be used. The low-coalized coal and peat are not completely coalified as the anthracite, and contain organic components, so in the present invention, the low-carbonized coal and peat are the organic components of low-carbonized coal and peat. Biomass is generated by methane fermentation of a certain biomass. And it is preferable to dry a residue and to utilize as a fuel or a cement baking material.

  Although only one type of low water content material may be used, a plurality of types may be used in combination. Moreover, the main biomass to be treated, the oil and fat, the low water content and the seed sludge may be mixed together, or the oil and fat may be impregnated in the low water content and then the oil and fat impregnated low water content and the main material. You may mix processing target biomass and seed sludge.

  Low moisture content materials that are already impregnated with fats and oils may be used. For example, activated white clay waste (waste white clay) used for decolorization in the process of refining edible oil, oily plants (such as peanuts) dried and pulverized can be used.

  Moreover, in order to impregnate fats and oils or to adjust moisture, a substance having a moisture content of 15% or less may be used as the fermentation object of the present invention. Examples of such substances include sawdust, organic waste charcoal (charcoal, etc.), thinned wood, dried wood such as driftwood, and crushed woody parts of building waste.

  Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.

FIG. 1 is a process diagram showing an embodiment of the method of the present invention. In this embodiment, the main processing target biomass 11 of the fermentation target 10 is an activated sludge cake. Waste tempura oil was used as the fat 12 in the fermentation object 10. Shredder paper was used as the low water content 13 in the fermentation object 10. First, the oil and fat 12 and the low water content 13 are mixed in the impregnation / mixing device 1, and the low water content (shredder paper) 13 is impregnated with the oil (waste tempura oil) 12. Next, the low water content substance impregnated with fats and oils, the activated sludge cake 11, and the seed sludge which is the already fermented product from a methane fermentation tank are mixed in the mixing apparatus 2. FIG. This mixture is introduced into the dry methane fermenter 3 to generate biogas (main component is methane CH ₄ ) by anaerobic digestion with methane bacteria. In addition, the ratio of each fermentation target object 10 (11, 12, 13) and the ratio with seed sludge are selected so that the total solid concentration in the methane fermentation tank 3 is 25% or more.

The biogas generated in the dry methane fermentation tank 3 is stored in a gas holder in the biogas storage / supply system 4, and is pressurized by a blower or the like, and H ₂ S (hydrogen sulfide) is removed by a desulfurization apparatus. Supplied to the cogeneration system 5. In the cogeneration system 5, electric power is generated by a gas engine or a fuel cell using biogas as fuel, and the exhaust heat generated at the same time is used for heating the methane fermentation tank 3 and heating the drying device 6. Supply as energy.

  On the other hand, most of the already fermented product from the dry methane fermenter 3 is returned to the mixing device 2 as seed sludge, and the portion (residue) that has not been returned as seed sludge is dried by the drying device 6 and is incinerated or landfilled. Is done. In addition, when rice bran etc. are used as the low moisture content 13, it may be dried by the drying apparatus 6 to an appropriate moisture content, and may be used as compost.

FIG. 2 is a flow chart showing another embodiment of the method of the present invention. In this example, garbage was used as the main processing target biomass 11 of the fermentation target 10. Edible oil was used as the fat 12 in the fermentation object 10. Low coal content coal (subbituminous coal) was used as the low water content 13 in the fermentation object 10. First, the subbituminous coal is pulverized to a suitable size that can be fermented by the pulverizer 7. Next, the garbage 11, the edible oil 12, and the finely powdered carbonized subbituminous coal 13 are mixed in the impregnation and mixing apparatus 1. These mixtures (11, 12, 13) and seed sludge, which is already fermented from the methane fermenter, are mixed in the mixing device 2. This mixture is introduced into the dry methane fermenter 3 to generate biogas (main component is methane CH ₄ ) by anaerobic digestion with methane bacteria.

The biogas generated in the dry methane fermentation tank 3 is stored in a gas holder in the biogas storage / supply system 4, is pressurized by a blower, etc., and is supplied to the cogeneration system 5. Although the biogas obtained by the method of the present invention has a low hydrogen sulfide concentration, it is preferably supplied to the cogeneration system 5 after removing H ₂ S (hydrogen sulfide) with a desulfurization apparatus. In the cogeneration system 5, electric power is generated by a gas engine or a fuel cell using biogas as fuel, and the exhaust heat generated at the same time is used for heating the methane fermentation tank 3 and heating the drying device 6. Supply as energy.

  On the other hand, the already fermented product from the dry methane fermenter 3 is mainly returned to the mixing device 2 as seed sludge, and the residue is dried by the drying device 6 until an appropriate water content is obtained, and used as a fuel or cement fired material. To do.

  Further, although subbituminous coal is used in the embodiment shown in FIG. 2, dry peat may be used instead.

  FIG. 3 is a flow chart showing still another embodiment of the method of the present invention. The difference between this embodiment and the method shown in FIG. 1 is that, in the embodiment of FIG. 1, fats and oils 12 and a low water content 13 are used as fermentation objects, but in the embodiment of FIG. The point is that waste white clay already containing oil is used as No. 13. Therefore, the impregnation / mixing device is unnecessary, and the main processing target biomass (activated sludge cake) 11, waste white clay 13 and seed sludge are supplied and mixed directly to the mixing device 2. Moreover, the fermentation residue from the dry-type methane fermenter 3 that has not been returned to the mixing device 2 as seed sludge is dried to an appropriate moisture content by the drying device 6 and used as compost. The other points are the same as those of the embodiment shown in FIG.

  FIG. 4 is a process diagram showing an embodiment of the wet dry combined methane fermentation method of the present invention. The dry methane fermentation method in this example is the same as the method described with reference to FIG. 1, rice husk is used as the low water content 13, pulverized by the pulverizer 8, and then supplied to the impregnation / mixer 1. 1 is different from the embodiment of FIG. 1 only in that it is impregnated with oil and fat and impregnated with fat and oil, and the fermentation residue from the dry methane fermentation tank 3 is used as compost.

On the other hand, the wet methane fermentation method is basically similar to the conventional method, and the fermentation target is not particularly limited as long as it is a biomass that has been conventionally treated by wet methane fermentation. In the illustrated embodiment, livestock manure was used as the biomass 20 to be treated. First, foreign matter such as stones mixed in livestock manure is removed by the foreign matter separation / crushing device 21 and crushed to a suitable size for processing. Next, in order to obtain an appropriate water content for wet methane fermentation, water is injected and diluted (hydrolysis 22). This hydrolyzed livestock manure 20 is introduced into the wet methane fermentation tank 23 to generate biogas (main component is methane CH ₄ ) by anaerobic digestion of methane bacteria. The fermentation residue from the wet methane fermentation tank 23 is solid-liquid separated by the dehydrator 24. The desorbed liquid from the dehydrator 24 is purified by the waste water treatment system 25 to a quality suitable for discharge, and part of it is used as water for hydration 22, and the rest is discharged. On the other hand, the solid content from the dehydrator 24, that is, the dehydrated cake, is used as a main processing target biomass in the dry methane fermentation and is supplied to the mixing device 2 in the dry methane fermentation.

The biogas generated in the wet methane fermentation tank 23 is sent to the biogas storage / supply system 4. The biogas storage and supply system stores the biogas generated in both wet and dry methane fermentation tanks 23 and 3 in a gas holder, increases the pressure with a blower, etc., and removes H ₂ S (hydrogen sulfide) with a desulfurizer. To the cogeneration system 5. In the co-generation system 5, electric power is generated by a gas engine or a fuel cell using biogas as fuel, and exhaust heat generated at the same time is used for heating both the wet and dry fermenters 23 and 3 and the drying device 6. It is supplied as thermal energy for heating.

  FIG. 5 is a process diagram showing another embodiment of the wet dry combined methane fermentation method of the present invention. This embodiment is basically the same as the embodiment shown in FIG. 4, but after the fermentation residue from the wet methane fermentation tank 23 is solid-liquid separated by the dehydrator 24, the effluent is dry methane fermentation. It differs from the fermented residue from the tank 3 in that it is supplied and mixed to the mixing device 9 to form liquid fertilizer.

  As fermentation objects, activated sludge cake 100 g (water content 85%), waste tempura oil 15 g (water content 0%), ground rice bran 15 g (water content 10%), lawn mower 15 g (water content 10%), Shredder paper 15 g (water content 5%) was used. When VS (volatile solid content: the amount lost due to high heat (600 ° C.) in the solid content, which is an indicator of the organic component in the solid content) of each fermentation object was measured in advance, it was 12 for 100 g of activated sludge cake. 8g, 15.0g for waste tempura oil 15g, 10.1g for 15g of chaff, 12.2g for lawn mower 15g, 13.5g for shredder paper 15g, and VS in 160g of the whole fermentation object is 63. It was 6 g.

  The ground rice cake, lawn mower and shredder paper were mixed well with waste tempura oil, and the waste tempura oil was impregnated with these low water content substances. This oil-impregnated low water content material, activated sludge cake and 749 g of seed sludge (water content 70%) were mixed well with a mixer and then packed into a 2 L glass bottle. The total amount charged into the glass bottle was 909 g, and the total water content was 67.5%. This was placed in an incubator (set at 57 ° C.) for 14 days.

  The weight of the glass bottle was measured with an electronic balance every day or every two days. The value obtained by multiplying the difference between the initial weight and the end weight (after 14 days) by 0.9 is defined as the VS decomposition amount (that is, the generated biogas contains water, so the water is assumed to be 0.1). The value obtained by multiplying the measured weight loss value by 0.9 was taken as the actual VS decomposition amount). As a result, the weight was reduced by 56.2 g from the initial weight at the end. Therefore, the decomposition rate by methane bacteria is (0.9 × weight loss value / VS). In this example, it was 0.795, and the organic content was decomposed with high efficiency by about 70% or more and about 80%. Was confirmed.

  In addition, gas generated in a gas bag was appropriately collected, and gas analysis was performed by gas chromatography. The methane gas concentration was also good.

  The same fermentation object as in Example 1 was used in the same amount. The amount of seed sludge was the same as in Example 1.

  In Example 2, unlike Example 1, fats and oils were not impregnated in low-moisture substances (crushed rice cake, lawn mower, shredder paper), but activated sludge cake, waste tempura oil, ground rice cake, lawn mower The fats and oils were directly mixed into the shredder paper and seed sludge. Then, this mixture was filled in a 2 L glass bottle as in Example 1, and placed in an incubator (set at 57 ° C.) for 14 days.

Since the difference between the initial weight and the end weight (after 14 days) is 55.5 g, and the VS in the initial total fermentation target 160 g is 63.6 g as in Example 1, the degradation rate is 0.785. Even when the fats and oils were directly mixed with the fermentation object as in Example 2, it was confirmed that the organic component in the fermentation object was decomposed with high efficiency.
[Comparative Example]
In order to compare with Example 1 and Example 2, the thing which does not use fats and oils as a fermentation target was investigated. Instead of 15 g of fats and oils in Examples 1 and 2, the amount of each low water content was increased by 5 g. That is, as an object to be fermented, 100 g of activated sludge cake (water content 85%), 20 g of ground rice bran (water content 10%), 20 g of lawn mower (20% water content), 20 g of shredder paper (5% water content) Was used. When the VS of each fermentation target was measured in advance, it was 12.8 g for 100 g of activated sludge cake, 13.5 g for 20 g of chaff, 16.2 g for lawn mower 20 g, 18.1 g for shredder paper 20 g, and total fermentation The VS in 160 g of the object was 60.6 g.

  These fermentation objects (activated sludge cake, ground rice cake, lawn mower, shredder paper) and 749 g of seed sludge (water content 70%) were mixed well in a mixer and then packed into a 2 L glass bottle. The total amount charged into the glass bottle was 909 g, and the total water content was 67.5%. As in Example 1, this was placed in an incubator (set at 57 ° C.) for 14 days.

  The difference between the initial weight and the end weight (after 14 days) was 40.4 g, and the VS in the initial fermentation object 160 g was 60.6 g, so the degradation rate was 0.6.

  Therefore, in this comparative example which did not use fats and oils, it was confirmed that the decomposition of the fermentation object was lower than in Example 1 and Example 2.

  100 g of raw garbage (water content 80%), 15 g of edible oil (water content 0%), and 50 g of sub-bituminous coal (water content 5%) were used as fermentation objects. When the VS (volatile solid content: the amount lost by ignition (600 ° C.) in the solid content, which is an indicator of the organic component in the solid content) of each fermentation object was measured in advance, it was 18. It was 15.0 g for 0 g, edible oil 15 g, and 23.8 g for 50 g of subbituminous coal, and VS in 165 g of the entire fermentation target was 56.8 g.

  These garbage, edible oil, and finely powdered sub-bituminous coal were mixed well and then mixed with 852 g of seed sludge (water content 67%) in a mixer and then packed into a 2 L glass bottle. The total amount charged into the glass bottle was 1017 g, and the total water content was 64.2%. This was placed in an incubator (set at 57 ° C.) for 14 days.

  The weight of the glass bottle was measured with an electronic balance every day or every two days. A value obtained by multiplying the difference between the initial weight and the end weight (after 14 days) by 0.9 was defined as the VS decomposition amount. As a result, the weight was reduced by 36.0 g from the initial weight at the end. Therefore, the decomposition rate by methane bacteria is (0.9 × weight loss value / VS), which is 0.570 in this example, and it was confirmed that the organic component was decomposed with high efficiency by about 60%. .

  In addition, gas generated in a gas bag was appropriately collected, and gas analysis was performed by gas chromatography. The methane gas concentration was also good. Moreover, the hydrogen sulfide concentration was very low.

  In Example 3, since subbituminous coal itself may be methane-fermented, for comparison, 50 g of charcoal (water content 10%) was used instead of subbituminous coal. Other fermentation objects (garbage and edible oil) were the same as in Example 3 and used in the same amount. The amount of seed sludge was also the same as in Example 3.

  The VS of each fermentation target was 18.0 g for 100 g of garbage, 15.0 g for edible oil 15 g, and 0 g for 50 g of charcoal, and VS in 165 g of the total fermentation target was 33.0 g.

These fermentation objects (garbage, edible oil, charcoal) and 852 g of seed sludge (water content 67%) were mixed well with a mixer and then packed into a 2 L glass bottle. The total amount charged into the glass bottle was 1017 g, and the total water content was 64.5%. As in Example 3, this was placed in an incubator (set at 57 ° C.) for 14 days.
The difference between the initial weight and the end weight (after 14 days) was 25.8 g.

  In Example 3 using sub-bituminous coal, the weight was reduced by 36.0 g in 14 days, but in Example 4 using charcoal, the weight was reduced only by 25.8 g. In Example 3 and Example 4, because the same amount of garbage, edible oil and seed sludge were used in the same amount, the difference in weight loss between the two was that subbituminous coal contained an organic component capable of methane fermentation. Show.

  Moreover, in Example 4, since VS in 165g of all initial fermentation objects was 33.0g, the decomposition rate by methane bacteria is (0.9 x weight loss value / VS). It was confirmed that the organic component was decomposed with high efficiency as much as about 70%. Since charcoal contains almost no organic component capable of methane fermentation, it was confirmed that other fermentation objects (garbage, edible oil) were efficiently decomposed by using fats and oils.

It is process drawing which shows one Example of the method of this invention. It is process drawing which shows another Example of the method of this invention. It is process drawing which shows another Example of the method of this invention. It is process drawing which shows one Example of the wet dry combined methane fermentation method of this invention. It is process drawing which shows another Example of the wet-dry type combined use methane fermentation method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Impregnation and mixing apparatus 2 Mixing apparatus 3 Dry-type methane fermentation tank 4 Biogas storage and supply system 5 Co-generation system 6 Drying apparatus 7 Fine powder carbonization apparatus 11 Main processing target biomass 12 Oils and fats 13 Low water content 20 Processing in wet methane fermentation method Target biomass 23 Wet methane fermentation tank 24 Dehydrator 25 Wastewater treatment system

Claims (8)

In the method of subjecting a fermentation object to a dry methane fermentation treatment, the fermentation object contains an oil and fat and a low water content having a moisture content of 15% or less, and the ratio of the fat to the total amount of the fermentation object is 3 to 15 mass. The total fermentation object and the already fermented product from the methane fermenter are mixed, the mixture is introduced into the methane fermenter, and the total solid concentration in the methane fermenter is 25% or more. A feature of dry methane fermentation.
In the method of subjecting a fermentation object to a dry methane fermentation treatment, the fermentation object contains an oil and fat and a low water content having a moisture content of 15% or less, and the ratio of the fat to the total amount of the fermentation object is 3 to 15 mass. After the oil and fat is impregnated in the low water content, the oil and fat impregnated low water content material, another fermentation object and the already fermented product from the methane fermenter are mixed, and the mixture is mixed with the methane fermentation. A dry methane fermentation method, which is introduced into a tank and has a total solid concentration of 25% or more in the methane fermentation tank.
In the method of subjecting a fermentation object to a dry methane fermentation treatment, the fermentation object contains oil and fat and subbituminous coal, lignite, or lignite , and the ratio of the fat to the total amount of the fermentation object is 3 to 15% by mass. The fermentation object and the already fermented product from the methane fermentation tank are mixed, the mixture is introduced into the methane fermentation tank, and the total solid concentration in the methane fermentation tank is 25% or more. Dry methane fermentation method.
In the method of subjecting a fermentation object to a dry methane fermentation treatment, the fermentation object contains fats and oils and peat, and the ratio of the fats and oils to the total amount of the fermentation objects is 3 to 15% by mass, and the fermentation object and A dry methane fermentation method characterized by mixing a previously fermented product from a methane fermentation tank, introducing the mixture into the methane fermentation tank, and having a total solid concentration of 25% or more in the methane fermentation tank.
The dry methane fermentation method according to claim 3 or 4, wherein the fermentation residue from the dry methane fermenter is dried to obtain fuel.
The dry methane fermentation method according to claim 3 or 4, wherein the fermentation residue from the dry methane fermenter is dried to obtain a cement fired material.
This is a method of treating a fermentation object using a combination of a wet methane fermentation method and a dry methane fermentation method. The main fermentation object is treated by a wet methane fermentation method, and the fermentation residue from the wet methane fermentation tank is dehydrated. The dehydrated cake, the fermentation object for the dry methane fermentation treatment mainly comprises the dehydrated cake, and further contains fats and oils and a low water content having a water content of 15% or less, for the dry methane fermentation treatment of the fats and oils. The ratio to the total amount of the fermentation object is 3 to 15% by mass, the already fermented product from the dry methane fermentation tank is used as seed sludge and mixed with the fermentation object for dry methane fermentation treatment, and the mixture is mixed with the dry methane fermentation tank The wet dry combined methane fermentation method, wherein the total solid concentration in the dry methane fermentation tank is 25% or more.
The wet dry combined methane fermentation method according to claim 7, wherein the fermentation residue desorption liquid from the wet methane fermentation tank and the fermentation residue from the dry methane fermentation tank are mixed to form liquid fertilizer.

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