JP2005230624A - Dry methane fermentation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for adjusting the moisture content of organic waste to be treated and reducing its nitrogen concentration by using dry methane fermentation, and a means therefor. <P>SOLUTION: In a dry methane fermentation system comprising a dry methane fermentation tank 100, and a carbonization system 106, low moisture content organic waste is carbonized at high temperature in the carbonization system 106 to obtain carbonized material as moisture content adjusting material and nitrogen concentration adjusting material. The above carbonized material is mixed with pretreated high moisture content organic waste, and then the mixture is subjected to the dry methane fermentation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a dry methane fermentation method for methane fermentation of organic waste.

  An effective method for recovering resources from organic waste is to use methane fermentation. Methane fermentation is often performed on liquid waste, such as factory effluent, organic effluent, and livestock manure, where the percentage of solid organic matter is, for example, 10% or less. Called fermentation. However, the treatment of wastewater after fermentation discharged in large quantities during wet methane fermentation requires a large amount of expenses including initial costs and operation costs. Moreover, it is necessary to stir slowly in the case of fermentation, and the stirring energy in that case is also required.

  When the ratio of solids is high, in order to use such wet methane fermentation, it is diluted by adding a liquid such as water to form a slurry. However, water is added before the fermentation and the processing volume is increased, so that the processing efficiency is deteriorated. Furthermore, the added liquid must be finally treated as waste water.

  On the other hand, there is a method in which methane fermentation is carried out in a non-immersed state without adding water to waste that occupies a high proportion of solids, for example, 10% or more, more typically 20% or more. is called. In dry methane fermentation, the solid matter in the fermenter can be processed without dilution, so the processing volume does not increase, the moisture content of the fermentation residue is low, and the wastewater treatment after fermentation is unnecessary. Moreover, since methane fermentation is performed in a dry state, the entire system can be easily handled and simplified. Therefore, the cost can be considerably reduced from the wet methane fermentation.

In such a methane fermentation method, when treating organic waste with a high nitrogen content such as manure and garbage, it is known that if the ammonia ion nitrogen concentration is high, methane fermentation inhibition is caused (for example, Non-patent document 1).
Originally written by RESpeece, translated by Saburo Matsui and Masanobu Takashima, “Anaerobic Biotechnology for Industrial Wastewater Treatment”, published by Gihodo, 1999, pages 293-296

In the case of wet methane fermentation, the nitrogen concentration can be reduced relatively easily by diluting with water, but in that case, the amount of waste water is further increased and the cost of waste water treatment is further increased.

  Therefore, an object of the present invention is to provide a method for reducing the nitrogen concentration by using dry methane fermentation, adjusting the water content of the organic waste to be treated, and means therefor.

  The dry methane fermentation method of the present invention includes a step of mixing an organic waste with a carbide to obtain an organic mixture, and a step of subjecting the organic mixture to methane fermentation. It is preferable that the carbide is a carbide carbonized at high temperature. Further, the carbide may be charcoal.

  Furthermore, the dry methane fermentation system of the present invention includes a carbonization system that generates carbides, and a dry methane fermentation tank for methane fermentation of an organic mixture of organic waste and the carbides.

  Furthermore, the moisture content adjusting material and the nitrogen concentration adjusting material of the present invention are a moisture content adjusting material and a nitrogen concentration adjusting material made of carbide for mixing with organic waste subjected to methane fermentation. This carbide is preferably produced by carbonizing organic waste, and more preferably produced by high-temperature carbonization.

  ADVANTAGE OF THE INVENTION According to this invention, the dry water methane fermentation is used, the water content of the organic waste which is a process target is adjusted, and the method of reducing the nitrogen concentration and its means can be provided.

  Hereinafter, a configuration example of a dry methane fermentation system according to the present invention and a dry methane fermentation method using the same will be described. The objects, features, advantages and ideas of the present invention will be apparent to those skilled in the art from the description of the present specification. The embodiments of the present invention described below show preferred embodiments of the present invention, and are shown for illustration or explanation, and the present invention is not limited to them. It will be apparent to those skilled in the art that various modifications and variations can be made based on the description given herein within the spirit and scope of the invention disclosed herein.

== Methane fermentation system ==
As shown in FIG. 1, an embodiment of a dry methane fermentation system according to the present invention includes a dry methane fermentation tank 100, a first organic waste (high water content) pretreatment system 102, and a second organic waste. It includes a pretreatment system 104 and a carbonization system 106, a mixing device 108, a methane gas storage / supply system 110, a cogeneration system 112, and a residue treatment device 114.

  Organic waste with a high water content such as activated sludge cake of sewage generated by waste water treatment, raw garbage from households and manure from farmers is processed by the pretreatment system 102. This system includes a foreign matter sorting device (not shown), a pulverizing device (not shown), and the like. First, non-organic waste such as plastic that cannot be processed by methane fermentation is removed from collected garbage and manure by a foreign matter separation device, and the waste is made up of almost only organic matter. The sorted organic waste is pulverized by a pulverizer into a size suitable for subsequent processing.

  On the other hand, the organic waste having a low water content is pretreated by the pretreatment system 104 in the same manner as the pretreatment system 102. When the organic waste having a low water content is woody waste such as waste wood, driftwood, thinned wood, etc., the pretreatment system 104 may be used as the chip forming device 216, and the wood waste may be formed into chips ( (See FIG. 2). This pre-treated organic waste is carbonized by carbonizing at a high temperature in the carbonization system 106. When carbonized at a low temperature, the pH of the carbide tends to be acidic, and therefore, it is preferable to bake at a high temperature at which the carbide becomes alkaline at least, for example, 700 ° C. or higher. By carbonizing at such a high temperature, there is an advantage that not only the carbide becomes alkaline, but also volatile components such as organic substances remaining in the carbide are reduced and the specific surface area is increased. At this time, the waste heat generated in the carbonization system 106 can also be used as heat energy for heating the dry methane fermentation tank or drying the fermentation residue. The carbide thus generated can be used not only as a dry methane fermentation system but also as a moisture content adjusting material and a nitrogen concentration adjusting material in wet methane fermentation systems and various systems.

  The organic waste crushed by the pretreatment system 102 and the carbide as the moisture content adjusting material and the nitrogen concentration adjusting material are mixed by the mixing device 108. At this time, the methane fermentation residue is also mixed together as seed sludge containing bacteria such as anaerobic bacteria necessary for methane fermentation. The amount of seed sludge is appropriately adjusted according to the properties of organic waste. In addition, although the carbide | carbonized_material used here may be carbonized by the carbonization system 106, it is not restricted to it.

  In this way, the moisture content of organic waste can be adjusted and the nitrogen content can be reduced by using carbides, so this dry methane fermentation system can be used to treat wastewater with high moisture content and high nitrogen content. It becomes possible to treat activated sludge cake, raw garbage, manure, etc. generated in the sewage. Moreover, the pH of the refined mixture can be moderately adjusted by using high-temperature carbonized carbide having an alkaline pH. In addition to the carbide, a moisture content adjusting material such as wheat straw, sawdust, rice bran, pruned branch, and waste paper may be further added and mixed.

  The mixture thus prepared is put into the dry methane fermentation tank 100, and the organic waste is subjected to methane fermentation by the methane fermentation method described later.

  Methane gas generated by methane fermentation is collected and sent to the methane gas storage / supply system 110. The methane gas storage / supply system 110 includes a desulfurization device (not shown), a methane gas storage device (not shown), and the like. In this system, the pressure of methane gas sent from the dry methane fermenter 100 is increased with a blower or the like, hydrogen sulfide is removed using a desulfurization apparatus, and the methane gas storage apparatus stores the methane gas. Alternatively, the collected methane gas may be stored in a methane gas storage device without being desulfurized, but even in that case, pressure increase with a blower or the like and hydrogen sulfide removal with a desulfurization device are performed before using the methane gas.

  The methane gas thus obtained is supplied from the methane gas storage / supply system 110 to the cogeneration system 112 and used as electric energy or heat energy.

  On the other hand, the fermentation residue discharged from the dry methane fermenter 100 is sent to the residue processing device 114, and after drying by a drying device (not shown), it is composted and reused, or is carbonized and processed as carbide. . During this drying, the waste heat generated in the carbonization system 106 or a part of the heat energy generated in the cogeneration system 112 may be used as heat energy for drying. Also, the dried residue may be returned to the carbonization system 106, in which case it will be added to the mixing device 108 as a carbide (see FIG. 3).

  In this system, if charcoal is added as a charcoal during fermentation, charcoal-mixed compost can be obtained, but charcoal improves air permeability and has a soil-improving function. Make things.

  Thus, the dry methane fermentation system of the present invention enables a wide use of organic waste including woody waste.

== Methane fermentation method ==
FIG. 4 is an overall configuration diagram of an example of the dry methane fermenter 100. A sectional view of the wall of the dry methane fermenter is shown in FIG.

  The dry methane fermentation tank 100 of the present embodiment is made of, for example, concrete and has a prismatic shape with a narrowed lower part. As shown in FIG. 5, the concrete wall 301 includes a hot water pipe 302 and a heat insulating material 306. In this embodiment, as shown in FIG. 4, the hot water pipe is divided into two parts 302 and 304 so that fine temperature adjustment can be performed.

  In the present embodiment, a perforated panel 320 is further provided inside the concrete wall 301 in parallel with the wall 301. The perforated panel 320 is made of, for example, stainless steel and has a large number of small holes of 100 to 200 μm. The space between the perforated panel 320 and the concrete wall 301 becomes a gas passage for methane gas generated by methane fermentation in the organic waste 314, and functions so that the methane gas is discharged to the upper space 318 more stably. The methane gas collected in the upper space 318 is discharged to the outside of the fermenter 100 through the discharge port 308. Further, the fermenter 100 is provided with a residue discharge port 310 and a discharge device 312 for adjusting the discharge amount.

  Methane fermentation is performed using the methane fermentation tank 100 having the above configuration. First, the organic mixture 314 of the organic waste, the moisture content adjusting material and the charcoal as the nitrogen concentration adjusting material, and the methane fermentation residue organic mixture 314 as the seed sludge mixed in the mixing device 108 are put into the methane fermentation tank 100. . As the methane fermentation residue as the seed sludge, the fermentation residue discharged from the fermenter 100 itself may be used. The amount of the fermentation residue is appropriately adjusted according to the properties of the organic waste. The charged organic mixture 314 is subjected to acid generation for the first few days. That is, by various facultative anaerobes, carbohydrates such as sugars in organic waste are decomposed into alcohols and low molecular organic acids, fats into fatty acids, proteins into amino acids and the like. Thereafter, methane is produced by methane bacteria from alcohols and organic acids that are degradation products.

  The methane generated in the organic mixture 314 flows into the space 318 above the organic mixture housing 316 through the gap between the organic mixture 314 and the space between the porous panel 320 and the concrete wall 301, and the generated methane itself. The methane gas is transported to the methane gas storage / supply system 110 through the discharge port 308 and collected.

1 is an overall configuration diagram of a dry methane fermentation system according to an embodiment of the present invention. It is a whole block diagram of the dry-type methane fermentation system of different embodiment of this invention. It is a whole block diagram of the dry-type methane fermentation system of further different embodiment of this invention. It is a whole block diagram of the dry-type methane fermentation tank of one Embodiment of this invention. It is sectional drawing of the wall of the dry-type methane fermenter of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Dry methane fermenter 102 Organic waste (high water content) pretreatment system 104 Organic waste (low water content) pretreatment system 106 Carbonization system 108 Mixing device 110 Methane gas storage and supply system 112 Co-generation system 114 Residue Treatment device 216 Wood waste chipping device 301 Concrete wall 302, 304 Hot water pipe 306 Heat insulating material 308 Methane gas discharge port 310 Residue discharge port 312 Discharge device 314 Organic mixture 316 Organic mixture container 318 Space 320 Perforated panel

Claims (6)

Mixing an organic waste with a carbide to obtain an organic mixture;
And a step of methane fermentation of the organic mixture.   The dry methane fermentation method according to claim 1, wherein the carbide is a carbide carbonized at high temperature.   The dry methane fermentation method according to claim 1 or 2, wherein the carbide is charcoal. A carbonization system for producing carbides;
A dry methane fermenter for methane fermentation of an organic mixture of organic waste and the carbide,
A dry methane fermentation system characterized by comprising:   Moisture content adjusting material consisting of carbide for mixing with organic waste to be methane-fermented. Nitrogen concentration adjusting material made of carbide for mixing with organic waste that is methane-fermented.

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