JP2005087977A - Organic waste treatment method and organic waste treatment system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic waste treatment method for efficiently treating a fermentation residual liquid being residue left by the methane fermentation treatment of organic waste, and an organic waste treatment system. <P>SOLUTION: The organic waste treatment system is equipped with a methane fermentation apparatus 10 for subjecting organic waste to methane fermentation, a solid-liquid separator 20 for separating the fermentation residual liquid due to methane fermentation into a solid component and a liquid component, a concentrator 30 for concentrating the liquid component to produce a concentrate, a dryer 40 for drying the solid component and the concentrate to obtain dried matter, and a pelletizing device 50 for pelletizing the dried matter. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic waste treatment method and an organic waste treatment system, and more particularly, treatment of organic waste capable of recovering pellets from a fermentation residue produced by methane fermentation treatment of organic waste. It relates to a method and a processing system.

  Methane fermentation treatment (anaerobic digestion) of organic waste such as livestock waste and food waste collects biogas (a gas mainly composed of methane produced by metabolism of anaerobic microorganisms) and recycles energy. Therefore, it is positioned as one of the renewable energy resources along with wind power generation and solar power generation.

  For systems that use methane fermentation and the biogas produced by it, a technology that uses the amount of heat generated by a power generator such as a fuel cell for heating methane fermentation in order to improve the overall energy utilization efficiency of the system Has been proposed (see, for example, Patent Document 1). However, in the system described in Patent Document 1, only a part of the amount of heat generated in the power generation device can be used effectively, and a lot of other heat is released. Can not.

  On the other hand, since the methane fermentation residual liquid produced | generated in a methane fermentation process contains a lot of plant nutrient components, it is composted (aerobic composting) and utilized as a fertilizer. However, when composting the fermentation residual liquid, a relatively large amount of secondary materials are required to adjust the moisture content and the carbon / nitrogen ratio, and the compost yard is a large area, for example, 10 times or more of the methane fermentation part. As a result, many of the benefits of methane fermentation have been diminished.

  In addition, since the fermentation residual liquid has extremely low sedimentation of solids, a large amount of a flocculant is usually required to perform solid-liquid separation. Since the liquid after solid-liquid separation generally has a higher COD (chemical oxygen demand) than BOD (biochemical oxygen demand), it can be purified to a water quality that can be released only by biological treatment. Therefore, after biological treatment, additional treatment such as nitrogen treatment (nitrification denitrification), decolorization treatment, addition of flocculant, membrane filtration is required. Nitrogen treatment uses chemicals such as methanol, decolorization treatment uses ozone, activated carbon, hydrogen peroxide, etc., and the addition of flocculants requires solids treatment after the separation, which increases energy consumption and processing costs. It had become.

  Japanese Patent Application Laid-Open No. 11-333416 discloses a method for treating organic waste that recovers carbonized carbon after agglomerating the digested sludge generated by fermentation of organic waste with an iron-based flocculant and dehydrating it. Has been described. However, the processing of the dehydrated filtrate of the fermentation residue is not fully considered.

  JP 2001-129599 A discloses a mechanically stirred composting apparatus in which surplus sludge and methane fermentation sludge are introduced as a dehydrated cake, carbide is introduced as a moisture adjusting agent, and an easily decomposable organic substance is provided as a heat supply. Is described, a method for treating fermented sludge in which dehydrated cake is composted and reduced in volume is described.

  JP-A-2002-1270 discloses a dehydration step for separating livestock manure into high-concentration wastewater and solids, a fermentation step for generating biogas by mixing garbage with the high-concentration wastewater, A waste disposal method including a step of mixing solid matter of livestock manure and the residue after the generation of biogas, drying and carbonizing is described. However, the processing of the dehydrated filtrate of the fermentation residue is not fully considered.

  Japanese Patent Application Laid-Open No. 2003-103299 describes a processing method for obtaining a carbide by dehydrating a fermentation residual liquid in a methane fermentation process with a dehydrator and carbonizing dehydrated sludge with a carbonization means. However, the processing of the dehydrated filtrate of the fermentation residue is not fully considered.

  Thus, the large processing load of the fermentation residual liquid produced | generated in a methane fermentation process is one of the big factors which hinder the spread of an organic waste processing system.

JP 2000-333101 A JP-A-11-333416 JP 2001-129599 A Japanese Patent Laid-Open No. 2002-1270 JP 2003-103299 A

  Thus, an organic waste treatment system that uses biogas produced by methane fermentation of organic waste can be an effective energy source, but methane fermentation requires processing of the fermentation residue. The energy efficiency of the entire system is greatly reduced. Therefore, there is a need for a technique for efficiently treating a fermentation residue, which is a residue obtained by subjecting organic waste to methane fermentation. Providing this technique is the subject of the present invention.

  In order to solve the above-mentioned problem, the invention of the organic waste processing method according to the first aspect of the present invention includes a methane fermentation step for methane fermentation of organic waste, and a fermentation residual liquid in the methane fermentation step, A solid-liquid separation process for separating the liquid into a liquid and a liquid; a concentration process for concentrating the liquid to obtain a concentrate; a drying process for drying the solid and the concentrate to obtain a dry product; And a pelletizing step using the dried product as pellets.

  In order to reduce the processing cost of the methane fermentation residual liquid, it is most effective to reduce its volume. In this aspect, the fermentation residue is separated into a solid and a liquid in the solid-liquid separation step, and the liquid is concentrated in the concentration step to obtain a concentrate. The solid-liquid separation step can reduce energy consumption in the subsequent concentration step. In addition, in the drying process, the solid content and the concentrate are dried to form a dried product, and this dried product is pelletized in the pelletizing process. Therefore, all of the fermentation residual liquid (that is, water in the concentration process and the drying process) The component excluding the condensed component) can be pelletized. Moreover, while making a fermentation residual liquid into a pellet, while being able to reduce a volume remarkably, a pellet can be utilized as a general fertilizer etc. by special fertilizer, a fertilizer raw material, and component adjustment.

  Moreover, the invention of the organic waste processing method according to the second aspect of the present invention is that, in the first aspect, the concentration step performs concentration using a multi-effect type concentration device. It is characterized by.

  In the multi-effect type concentrator, high concentration is possible with a small amount of heat, so that sufficient concentration can be performed while minimizing energy consumption. In addition, since the reduced pressure multiple effect method enables concentration at a low temperature, the valuable materials are hardly denatured or decomposed, and these can be recovered as pellet components.

  Moreover, the invention of the organic waste processing method according to the third aspect of the present invention is the method of the first aspect or the second aspect, further using the biogas obtained in the methane fermentation step as a fuel. It includes a cogeneration process for recovering electric power, and the heat recovered in the cogeneration process is used as a heat source in the concentration process and / or the drying process.

  The cogeneration process using biogas as fuel can recover heat (for example, steam and hot water) and electric power, but the heat content has not been fully utilized. However, in this aspect, since the heat recovered in the cogeneration process is used as a heat source in the concentration process and / or the drying process, it is possible to efficiently use energy resources in the entire process related to the organic waste treatment system. Can be used effectively. That is, the biogas generated in the methane fermentation process can be effectively used to efficiently generate pellets from the fermentation residual liquid.

  The organic waste treatment method according to the fourth aspect of the present invention is the organic waste treatment method according to any one of the first aspect to the third aspect, further comprising biogas obtained in the methane fermentation step. A heat generation step for generating heat as a fuel is included, and the heat generated in the heat generation step is used as a heat source in the concentration step and / or the drying step.

  The heat generation process using biogas as fuel can generate heat (for example, in the form of steam or hot water). Since this heat is used as a heat source in the concentration step and / or the drying step, it is possible to efficiently use energy in the entire process related to the organic waste treatment system. That is, by effectively using the biogas generated in the methane fermentation process and generating only the necessary amount of heat (for example, steam, hot water) in the concentration process and / or drying process, pellets can be efficiently produced from the fermentation residue. Can be generated.

  Moreover, the invention of the organic waste treatment system according to the fifth aspect of the present invention includes a methane fermentation apparatus for methane fermentation of organic waste, and a fermentation residual liquid from the methane fermentation into a solid content and a liquid content. A solid-liquid separation device for separating; a concentrating device for concentrating the liquid to obtain a concentrate; a drying device for drying the solid and the concentrate to obtain a dried product; and the dried product as a pellet. And a pelletizing device.

  In order to reduce the processing cost of the methane fermentation residual liquid, it is most effective to reduce its volume. In this aspect, the fermentation residue is separated into a solid and a liquid in a solid-liquid separator, and the liquid is concentrated in a concentrator to obtain a concentrate. The solid-liquid separation device can reduce energy consumption in the subsequent concentration device. In addition, the solid content and the concentrate are dried in a drying apparatus to form a dried product, and this dried product is pelletized in the pelletizing apparatus. Therefore, all of the fermentation residual liquid (that is, water in the concentration apparatus and the drying apparatus, etc. The component excluding the condensed component) can be pelletized. Moreover, while making a fermentation residual liquid into a pellet, while being able to reduce a volume remarkably, a pellet can be utilized as a general fertilizer etc. by special fertilizer, a fertilizer raw material, and component adjustment. Moreover, the energy efficiency of the whole system is high, and a pellet can be produced | generated from a fermentation residual liquid with little energy.

  The organic waste treatment system according to the sixth aspect of the present invention is the cogeneration apparatus for recovering heat and power from the biogas obtained by the methane fermentation and / or the fifth aspect. Or a heat generating device that generates heat from the biogas obtained by the methane fermentation, and the heat collected by the cogeneration device and / or the heat generated by the heat generating device is the concentrating device and / or the drying device. It is characterized by comprising heat supply means for supplying to

  This organic waste treatment system is a device for concentrating and / or drying heat generated by a cogeneration device (for example, steam, hot water) and / or heat generated by a heat generation device (for example, steam, hot water). Since the heat supply means for supplying the apparatus is provided, the heat can be effectively used, and the energy efficiency of the entire system can be remarkably increased. Therefore, the treatment system of this embodiment is a system suitable for the treatment of organic waste.

  According to the organic waste processing method and processing system of the present invention, the volume of the fermentation residual liquid produced by methane fermentation can be significantly reduced, and the processing cost can be reduced. In addition, since all of the fermentation residual liquid except the condensed components such as water can be pelletized, it is not necessary to provide a separate facility for processing the liquid after solid-liquid separation, The configuration can be simplified. Moreover, the pellet obtained by processing the methane fermentation residual liquid has high handleability and flowability, and can be used as a general fertilizer by adjusting special fertilizers, fertilizer raw materials, and components, and is useful.

  In addition, the energy efficiency of the entire system can be increased by the cogeneration process and the heat generation process, and the energy resources can be efficiently used.

Hereinafter, the organic waste processing method and the organic waste processing system according to the present invention will be described.
The organic waste processing method according to the present invention includes a methane fermentation step for methane fermentation of organic waste, a solid-liquid separation step for separating the fermentation residual liquid of the methane fermentation step into solids and liquids, A concentration step of concentrating the liquid to obtain a concentrate, a drying step of drying the solid and the concentrate to obtain a dried product, and a pelletizing step of using the dried product as a pellet. It is characterized by.

  Examples of organic waste (biomass) include livestock waste, green farm waste, wastewater treatment sludge, and the like. Here, livestock waste includes livestock manure, carcass, processed products thereof, and more specifically livestock carcasses such as cattle, sheep, goats, chickens, bones separated therefrom, In addition to meat, fat, internal organs, blood, brain, eyeballs, skin, hoofs, horns, etc., for example, bone and meat of animal carcasses represented by meat and bone meal, meat meal, bone meal, blood meal, etc. Also included are dried products obtained by drying blood and the like. In addition to household garbage, the green agricultural waste includes agricultural and industrial waste, food processing waste and the like as industrial waste.

  Further, depending on the state of the organic waste, a crushing / sorting step can be performed as a pretreatment as necessary. The crushing / sorting step can be performed by, for example, fractional crushing and whole quantity crushing as shown below.

  In the case of fractional crushing, a crushing / separating machine is used to collect a portion of the organic waste that can be crushed relatively easily as a slurry together with the liquid. On the other hand, parts that are difficult to crush are collected separately as a lump. The water content of the slurry is about 70 to 98% by weight. The crushing / separating machine crushes organic solids by a shearing force and a pulling force, and a two-axis type or a three-axis type cutter can be used. When animal carcasses such as cattle are used as raw materials, crushing with a triaxial crushing and sorting machine is preferred from the viewpoint of crushing fineness and uniformity. It is preferable to remove mixed plastics, sheets, and the like to be sorted and removed by sorting with a mesh, wind sorting, or the like.

  Further, in the case of crushing the entire amount, for example, a crusher such as a disposer is used to crush all objects. The moisture content is about 60 to 80% by weight as an example, but in the case of a processed product, it can take a wider range.

<Methane fermentation>
Methane fermentation (anaerobic digestion) can be applied to any type of so-called medium temperature type, high temperature type, slurry (wet) type, and dry (dry) type.

  The fermenter is composed of a tank in which air is completely shut off at the subsequent stage even in the case of a fermentation process using a two-tank system so as not to hinder the activity of methane fermentation bacteria that are absolutely anaerobic. A fermenter sets a shape and an operating condition with solid content concentration (usually the range of 7-40 weight%) and fermentation temperature (usually 37 degreeC in medium temperature fermentation, 55 degreeC in high temperature fermentation). Particularly in the present invention, in the case of a raw material with a high water content (up to a solid content concentration of 10% by weight), a wet type complete mixing type fermenter, a raw material with a low water content (a solid content concentration of 30 to 40% by weight) It is preferable to use a dry type plug flow type (extrusion type) fermenter.

  In addition to the recovery means for recovering the produced biogas, the fermenter is preferably provided with a heating means for maintaining the inside of the tank at a temperature suitable for methane fermentation. The biogas recovery means can be provided with a desulfurization apparatus as required. This desulfurization apparatus can remove highly corrosive sulfur compounds (for example, hydrogen sulfide) from biogas. These devices can be used in known configurations. As the heat source of the heating means of the fermenter, for example, the heat recovered in the cogeneration process described later can be used.

  In general methane fermentation, the residence time is about 20 to 30 days for medium temperature fermentation and about 15 days for high temperature fermentation. In the present invention, a raw material with a high water content (solid content concentration is about 10% by weight). In the case of the above), a complete mixing type fermenter is used, and the residence time is about 15 to 20 days for medium temperature methane fermentation bacteria (optimum temperature 37 ° C.), and the residence time for high temperature methane fermentation bacteria (optimum temperature 55 ° C.). Can be shortened to about 10 days, which is shorter than the time required for normal methane fermentation. In the case of a raw material having a low water content (solid content concentration of 30 to 40% by weight), the solid content concentration of the material to be treated is adjusted to 30 to 40% by weight to adjust the hardness to such an extent that an extrusion-type fermenter can be used. About residence time, it can set similarly to the case of high moisture content. If necessary, some organic components can be introduced to adjust the carbon / nitrogen ratio.

  The fermentation residual liquid after methane fermentation differs depending on the type of organic waste. For example, in methane fermentation with a high water content, it is a liquid containing about 90 to 97% by weight of water content and about 3 to 10% by weight of solid content. It contains a large amount of valuable substances such as various amino acids and organic acids derived from the cells of anaerobic microorganisms and their metabolites.

  After the methane fermentation, a pH adjustment step of the fermentation residual liquid can be provided. In order to improve the solid-liquid separation in the subsequent solid-liquid separation process, to recover valuables in the solid content, to reduce the generation of bubbles, and to suppress the generation of droplets, the pH is adjusted, It is preferable to agglomerate valuable materials such as quality and collect them in a solid content to improve solid-liquid separation and to disperse dissolved carbon dioxide. In the pH adjustment, for example, an inorganic acid such as sulfuric acid or hydrochloric acid is added to adjust the pH value of the fermentation residue to 4.5 to 5.5.

<Solid-liquid separation process>
In the solid-liquid separation step, the fermentation residual liquid is separated into a solid content and a liquid content. In order to suppress energy consumption in the subsequent concentration step, solid-liquid separation is performed to separate the solid content from the fermentation residue. For the solid-liquid separation, an apparatus capable of increasing the slurry concentration, such as a centrifuge, a screw press, a decanter, a coagulation sedimentation tank, or a membrane separator, can be used, and can be selected according to the properties of the fermentation residual liquid. The fermentation residual liquid is separated into a solid content having a solid content concentration of about 7 to 20% by weight and a liquid content having a solid content concentration of about 1 to 4% by weight by the solid-liquid separation step.

<Cogeneration process>
In the cogeneration process, heat (for example, steam, warm water) and electric power are generated using biogas obtained by methane fermentation as fuel. Biogas is a gas containing about 50 to 60% by volume of methane, about 40 to 50% by volume of carbon dioxide and other trace components (such as hydrogen sulfide), although it varies depending on the type of organic waste. It can be fully used as an energy source in cogeneration.

  Examples of the device used in the cogeneration process include a steam boiler generator, a micro gas turbine, a fuel cell, a gas engine, or a combination thereof. In this cogeneration process, heat and electric power can be recovered using biogas as fuel. The heat recovered at this stage can be used in the form of steam or hot water as a heat source for the concentrator in the concentration process and / or the drying apparatus in the drying process. In addition, when heat | fever is collect | recovered with warm water (hot water), it can use as a heat source of the heating means of a fermenter, a heat source of the preheating of a process process, etc.

  The electric power obtained in the cogeneration process can also be used in a concentrator in the concentration process and / or a drying apparatus in the drying process. In addition, surplus heat and electric power can be diverted to other uses, and improvement of the energy efficiency of the whole system can be aimed at by combining with a biogas boiler etc.

  Further, it is preferable to provide a heat generation step for generating heat (for example, steam or hot water) using biogas obtained by methane fermentation as fuel. Examples of the heat generation apparatus in the heat generation process include a biogas boiler and a steam boiler. The heat generated in the heat generation process can be used in the form of steam or hot water as a heat source for the concentration apparatus in the concentration process and / or the drying apparatus in the drying process.

<Concentration process>
In the concentration step, by concentrating the liquid component in the solid-liquid separation step, a concentrate having a solid concentration of about 20 to 30% by weight can be generated, and the total amount can be reduced to about 20 to 30%. .

  Concentration can be performed using a known concentrator, but it is preferably performed under reduced pressure using a multi-effect type concentrator. As the multi-effect type concentrating device, a device having a known configuration such as a double-effect can, a triple-effect can, a quadruple-effect can, or a five-effect can can be used. These enable concentration at a relatively low temperature, and can significantly increase energy efficiency in the concentration step. For multiple effect cans, the required heat is about 1/3 (for triple to quadruple effect cans) to 1/4 (for quadruple to fivefold effect cans) compared to a single evaporator can. Can be reduced.

  In the multi-effect system, a steam compressor provided on the steam introduction path connecting each can is also preferable. By forcibly introducing steam with the steam compressor, the fermentation residual liquid in the can is forcibly circulated, further improving the thermal efficiency and improving the concentration efficiency. The condensate produced during the concentration step may contain nitrogen components and the like. However, since these components are in a small amount, they can be processed by simple biological treatment or membrane treatment.

<Drying process>
In the drying step, the mixture of the solid content in the solid-liquid separation step and the concentrate in the concentration step can be dried to a solid content concentration of about 60 to 90% by weight, and the total amount is about 5 to 12%. Volume can be reduced.

  The solid content in the solid-liquid separation step and the concentrate in the concentration step can be mixed in the mixing step, and for example, a solid content concentration of about 15 to 25% by weight can be dried. As a mixing apparatus in the mixing step, for example, a line mixer can be used.

  Although drying can be performed using a known drying apparatus, it is preferably performed using a multi-effect drying apparatus. As a multi-effect drying apparatus, a known apparatus such as a double-effect can or a triple-effect can or a drum dryer system can be used. These enable drying at a relatively low temperature and can significantly increase energy efficiency in the drying process. In the multi-effect can, the required amount of heat can be reduced to about 1/3 to 1/4 as compared with a drying apparatus using a single drying can. The condensate produced in the course of the drying process may contain nitrogen components and the like, but since these components are in a small amount, they can be processed by simple biological treatment or membrane treatment.

<Pelletization process>
In the pelletization step (granulation step), the dried product in the drying step is pelletized to form pellets, and the total amount can be about 5 to 10% of the initial fermentation residual liquid amount. By using pellets, the volume can be remarkably reduced as compared with the fermentation residual liquid, and handling, distribution, long-term storage, durability, and strength can be improved. In addition, it is suitable for machine spraying on fields and the like, and the generation of dust after spraying can be reduced.

  Pelletization can be performed using a known pelletizing apparatus or pelletizer. For example, using a pelletizing apparatus equipped with an extrusion apparatus and a cutter, a dried product is applied to a plate body on which molding holes are formed. It can be made into a pellet by compressing and cutting the molded product extruded from the hole with a predetermined length. The shape of the pellet can be, for example, a cylindrical shape or a prismatic shape, and the cross-sectional shape can be a circle, a star, a triangle, or the like.

  Prior to pelletization, auxiliary materials can be added to the dried product as necessary. Examples of the auxiliary material include a pressure-sensitive adhesive and a component adjusting agent. Examples of the pressure-sensitive adhesive include rice bran and molasses. By adding the pressure-sensitive adhesive, the granulation property and moldability can be improved. An adhesive is added so that it may become about 10 weight% with respect to a dried material. As a component regulator, the chemical | medical agent containing a potassium component, a phosphorus component, etc. can be mentioned, for example, a nutrient component can be adjusted by adding a proper quantity of a component regulator, and it can be set as a general fertilizer. In addition, when adding these subsidiary materials, it is preferable to use the mixing apparatus which mixes a dried material and subsidiary materials.

  After the pelletizing step, a pellet drying step can be provided as necessary. The solid content concentration of the pellets can be reduced to about 85 to 95% by drying, and the corrosion resistance, durability, and strength can be further improved, and the long-term storage property, handleability, and weight reduction are accompanied. Distribution can be further enhanced.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an outline of an organic waste treatment system 101 according to the first embodiment of the present invention. The organic waste treatment system 101 includes a methane fermentation tank 10 as a methane fermentation apparatus, a solid-liquid separation apparatus 20, a concentration apparatus 30, a drying apparatus 40, and a pelletizing apparatus 50 as main components. Furthermore, a steam boiler 70 and a cogeneration device 80 as heat generation devices are provided as devices using biogas as fuel. The configuration and function of each device are as described above.

  As shown in FIG. 1, the organic waste is put into a fermenter 10 and subjected to methane fermentation for a predetermined period under anaerobic conditions. By this methane fermentation, a fermentation residual liquid having a solid concentration of about 5% by weight is generated from the fermenter 10.

  The fermentation residue, which is a residue after methane fermentation, is a liquid having a solid concentration of about 5% by weight, transferred to the pH adjustment tank 15, and adjusted to a pH value of 4.5 to 5.5. The pH adjustment is performed by adding sulfuric acid, hydrochloric acid or the like to the fermentation residual liquid introduced into the pH adjustment tank 15 and sufficiently mixing and stirring the mixture by a stirring means (not shown). By adjusting the pH, valuable substances such as humic substances can be aggregated into solids to improve solid-liquid separation, and carbon dioxide dissolved in the fermentation residual liquid can be diffused to generate bubbles and splashes in the subsequent stage. Can be reduced.

  The fermentation residual liquid after pH adjustment is sent to the solid-liquid separator 20 and separated into a solid content with a solid content concentration of about 15% by weight and a liquid content with a solid content concentration of about 3.5% by weight. The weight ratio of the solid content to the liquid content is about 2: 8 to 4: 6.

  The liquid is sent to the concentrator 30 where it is concentrated to a solid concentration of about 20 to 30% by weight to become a concentrate. The path 71 as the heat supply means from the steam boiler 70 to the concentrating device 30 may be any one that constitutes a normal fluid flow path (for example, a heat insulating pipe), but the heat from the steam boiler 70 is steam. Since it is supplied in the form, it is also possible to provide a steam compressor in the path 71. Moreover, the path | route 81 as a heat supply means from the cogeneration apparatus 80 is connected to the concentration apparatus 30, and the heat component from the cogeneration apparatus 80 is supplied in the form of warm water.

  Here, FIG. 2 shows a configuration of an example of a concentration apparatus that can be suitably used in the present invention. The concentrator 30 is a multi-effect type concentrator, and is composed of a first can 31, a second can 32, and a third can 33, forcibly circulating a fluid in each can (31, 32, 33). This is a triple effect can. The forced circulation method is a method for avoiding evaporation in a heating unit (not shown) and forcibly circulating the inside of the concentration can as a liquid having a saturation temperature. Since the liquid content of the fermentation residual liquid increases as the degree of concentration increases, the fluidity of the concentrated concentrate is secured by adopting the forced circulation method, and scaling within the equipment is performed. Occurrence can be minimized.

  Steam from the steam boiler 70 is mainly introduced into the first can 31 through the path 71a, and liquid from the solid-liquid separator 20 is introduced through the path 21a. The liquid portion of the fermentation residual liquid is introduced into the first can 31 after preheating with steam or hot water in a heating unit (not shown).

  Since the inside of the first can 31 is maintained in a negative pressure state by a decompression device (not shown), the liquid content of the fermentation residual liquid is concentrated at a low temperature. For this reason, the components contained in the concentrate are hardly denatured or decomposed by heat.

  The concentrate concentrated to a predetermined concentration in the first can 31 is transferred to the second can 32 via the path 21b, where it is concentrated in the same manner as in the first can 31, and then the third can be passed through the path 21c. It is sent to the can 33 and is further concentrated in the same manner. Moreover, the vapor | steam discharged | emitted from the 1st can 31 is sent to the 2nd can 32 through the path | route 71b, and the vapor | steam discharged | emitted from the 2nd can 32 is sent to the 3rd can 33 via the path | route 71c. A heating and compressing device (38, 39) is disposed in the path (71b, 71c) through which the steam passes. In this way, the steam (heat) generated in the steam boiler 70 can be repeatedly used as an evaporation heat source in the first can 31, the second can 32, and the third can 33. It is possible to concentrate with one heat quantity, and the energy efficiency is remarkably high. The pressure and temperature in each can are, for example, 20 to 30 kPa, 60 to 70 ° C. for the first can 31, 47 to 70 kPa and 80 to 90 ° C. for the second can 32, about 100 kPa for the third can 33, 100 ° C. or more. It becomes a standard.

  Returning to FIG. 1, the condensate produced in the concentration process of the concentration device 30 can be reused after the nitrogen content is removed by the water treatment device. Examples of the water treatment apparatus include an apparatus that performs nitrification and denitrification by simple biological treatment using an activated sludge method, and a membrane treatment apparatus.

  The concentrate concentrated to a solid concentration of 20 to 30% by weight by the concentrating device 30 is transferred to the drying device 40 via the path 35. In the path 35 through which the concentrate passes, the solid content separated by the solid-liquid separator 20 is introduced, and the concentrate and the solid content are mixed to prepare a mixture having a solid content concentration of about 15 to 25% by weight. In order to sufficiently mix the concentrate and the solid content, it is preferable to provide a line mixer (not shown) as a mixing device in the path 35. In addition, the concentrate (including the mixture with the solid content) can be used as liquid fertilizer as it is, and the valuable material is recovered by processing with a valuable material recovery device (such as a microfiltration membrane) (not shown) as necessary. You can also.

  A mixture of the concentrate and the solid content (hereinafter referred to as “concentrate”) introduced into the drying apparatus 40 is dried to a solid content concentration of about 70 to 90% by weight to become a dry product. The path 72 as the heat supply means from the steam boiler 70 to the drying device 40 may be any one that constitutes a normal fluid flow path (for example, a heat insulating pipe), but the heat from the steam boiler 70 is steam. It is also possible to provide a steam compressor in the path 72 because it is supplied in the form. Moreover, the path | route 82 as a heat supply means from the cogeneration apparatus 80 is connected to the drying apparatus 40, and the heat component from the cogeneration apparatus 80 is supplied in the form of warm water.

  Here, FIG. 3 shows a configuration of an example of a drying apparatus that can be suitably used in the present invention. The drying device 40 is a multi-effect drying device, which includes a first can 41, a second can 42, and a third can 43, and a drum as a rotating body is provided in each can (41, 42, 43). Drum dryer system. As the degree of dryness of the concentrate increases, the viscosity increases and it becomes easy to stick in the apparatus, but this can be suppressed by rotating the drum.

  The steam from the steam boiler 70 is mainly introduced into the first can 41 through the path 72a, and the concentrate is introduced through the path 35a. If necessary, the concentrate can be preheated with steam or hot water in a heating unit (not shown) and then introduced into the first can 41.

  The dried product dried to a predetermined degree in the first can 41 is transferred to the second can 42, where it is dried in the same manner as in the first can 41, and then sent to the third can 43. Dried. Moreover, the vapor | steam discharged | emitted from the 1st can 41 is sent to the 2nd can 42 through the path | route 72b, and the vapor | steam discharged | emitted from the 2nd can 42 is sent to the 3rd can 43 via the path | route 72c. Thus, since the steam (heat) generated in the steam boiler 70 can be repeatedly used as a drying heat source in the first can 41, the second can 42, and the third can 43, it is several minutes compared to the single effect system. It is possible to dry with one heat quantity, and the energy efficiency is remarkably high. In addition, the condensate produced in the drying process of the drying apparatus 40 can be reused after removing nitrogen from the water treatment apparatus.

  Returning to FIG. 1, the dried product is introduced into the pelletizing apparatus 50 and pelletized to become pellets. The shape, length, etc. of the pellet are appropriately changed according to the situation in which it is used. Moreover, if necessary, pellets can be introduced into a drying apparatus (not shown) and further dried to obtain a solid content concentration of about 85 to 95% by weight. The pellets can be used as general fertilizers when special fertilizers, fertilizer raw materials, and component adjustments are performed.

  In this embodiment, the steam recovered by the steam boiler 70 is supplied to the concentrating device 30 and the drying device 40, and the hot water recovered by the cogeneration device 80 is supplied to the concentrating device 30 and the drying device 40, respectively, and used as a heat source. However, the present invention is not limited to this.

  Biogas produced by methane fermentation in the methane fermentation tank 10 is collected by a collecting means (not shown) and sent to the desulfurization apparatus 60. In the desulfurization apparatus 60, sulfur compounds (for example, hydrogen sulfide) contained in the biogas are removed.

  The biogas after desulfurization is divided into two parts, and one is sent to the steam boiler 70 and used as a heat source when generating high-temperature steam. The other biogas is sent to the cogeneration system 80 and used as a heat source when generating heat (hot water) and electric power.

  The heat (steam) collected by the steam boiler 70 is supplied to the concentrating device 30 and the drying device 40 as described above. As described above, the heat (warm water) recovered by the cogeneration apparatus 80 is supplied to the concentrating device 30 and the drying device 40, and is also supplied to the fermenter 10 via a pipe 83 serving as a heat supply means. It is used as a heat source for 10 heating means.

  Next, FIG. 4 is a block diagram showing an outline of the organic waste treatment system 102 according to the second embodiment of the present invention. About the same structure as FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  This organic waste treatment system 102 includes a micro gas turbine 90 instead of the steam boiler 70 and the cogeneration apparatus 80 in the embodiment shown in FIG. 1 as a cogeneration apparatus. In the organic waste treatment system 102 according to the present embodiment, the micro gas turbine 90 generates power using biogas as fuel, and the heat generated in the process of power generation (for example, in the form of hot water) is supplied to the concentration device 30 and the drying device. 40 and the fermenter 10 can be used as a heat source in each apparatus. In addition, piping (91, 92, and 93) as heat supply means from the micro gas turbine 90 is connected to the concentrating device 30, the drying device 40, and the fermenter 10.

  The present invention has been described above with some embodiments. However, the present invention is not limited to the above embodiments, and other embodiments are within the scope of the invention described in the claims. Is also applicable.

  INDUSTRIAL APPLICABILITY The present invention can be used to efficiently treat a fermentation residue produced by subjecting organic waste to methane fermentation and to suitably recover pellets.

BRIEF DESCRIPTION OF THE DRAWINGS Drawing which shows schematic structure of the organic waste processing system which concerns on 1st Embodiment of this invention. The schematic diagram of the triple effect type concentration apparatus which can be utilized for the organic waste processing system of this invention. The schematic diagram of the triple effect type drying apparatus which can be utilized for the organic waste processing system of this invention. Drawing which shows schematic structure of the organic waste processing system which concerns on 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Methane fermenter 15 pH adjustment tank 20 Solid-liquid separator 30 Concentrator 31 First can 32 Second can 33 Third can 40 Drying device 41 First can 42 Second can 43 Third can 50 Pelletizer 60 Desulfurizer 70 Steam boiler 80 Cogeneration system 90 Micro gas turbine

Claims (6)

A methane fermentation process for methane fermentation of organic waste,
A solid-liquid separation process for separating the fermentation residual liquid of the methane fermentation process into a solid content and a liquid content;
A concentration step of concentrating the liquid to obtain a concentrate;
A drying step of drying the solid and the concentrate to obtain a dried product;
And a pelletizing step using the dried product as a pellet. 2. The organic waste treatment method according to claim 1, wherein the concentration step performs concentration using a multi-effect type concentration device. In Claim 1 or Claim 2, further including a cogeneration process which collects heat and electric power by using biogas obtained in said methane fermentation process as fuel,
An organic waste processing method, wherein heat recovered in the cogeneration step is used as a heat source in the concentration step and / or the drying step. The method according to any one of claims 1 to 3, further comprising a heat generation step of generating heat using the biogas obtained in the methane fermentation step as fuel.
A method for treating organic waste, wherein heat generated in the heat generation step is used as a heat source in the concentration step and / or the drying step. A methane fermentation device for methane fermentation of organic waste,
A solid-liquid separation device for separating the fermentation residual liquid from the methane fermentation into a solid content and a liquid content;
A concentrator for concentrating the liquid to obtain a concentrate;
A drying device for drying the solid and the concentrate to obtain a dried product;
An organic waste treatment system comprising: a pelletizing device that uses the dried product as pellets. In claim 5, further comprising a cogeneration device for recovering heat and power from the biogas obtained by the methane fermentation and / or a heat generation device for generating heat from the biogas obtained by the methane fermentation,
Organic waste comprising heat supply means for supplying heat recovered by the cogeneration apparatus and / or heat generated by the heat generation apparatus to the concentration apparatus and / or the drying apparatus Processing system.

Images