JP2021070006A - Organic waste treatment system - Google Patents

Abstract

To provide an organic waste treatment system capable of treating waste without constructing a waste treatment facility, for generating biogas from organic waste with high efficiency, serving as an energy source for power generation, and hardly generating waste by appropriately treating fermentation residues and digestive juices.SOLUTION: An organic waste treatment system includes: a subcritical water treatment device for reducing molecular weight of organic waste; a methane fermentation device for generating biogas from the organic waste reduced in molecular weight by a methanogen; a gas purification device for removing carbon dioxide from the biogas generated by methane fermentation; and a solid-liquid separation device for pressure-floating and separating harmful substances from digestive juices generated by methane fermentation. At least one of these devices is a movable unit, is conveyed to a place where organic waste treatment is performed, assembled and installed at the place, and is then disassembled and carried out.SELECTED DRAWING: Figure 1

Description

The present invention relates to the creation of energy from combustible industrial waste products. Since it can produce electricity, heat, fertilizer and carbon dioxide as methane fermentation products and processed products, it can be used in a wide variety of fields.

To date, the energy consumed by humankind has been financed by burning most of its fossil fuels. All of these methods released carbon dioxide and combustibles into the environment.

Japan has set a reduction target of 26.0% reduction in greenhouse gas emissions in FY2012 by Reiwa 2012 by reducing greenhouse gas emissions and securing absorption in Japan. After that, based on the adoption of the Paris Agreement at COP21, the global warming countermeasure plan was approved by the Cabinet in May 2016.

On the other hand, the Ministry of the Environment changed the "basic policy for comprehensive and systematic promotion of waste reduction and other measures related to its proper treatment" based on the Waste Management Law on January 21, 2016. However, while setting target values from the viewpoint of waste energy utilization, we will promote efforts such as effective utilization of waste as an energy source and utilization of waste energy in the region.

However, in small and medium-sized general waste treatment facilities, the current situation is that the utilization of waste energy is not sufficiently carried out from the viewpoint of not accumulating know-how and cost.

Furthermore, the effects of "population decline" and "declining birthrate and aging population" are also having a great impact on the waste administration of local governments. In other words, it is very difficult to maintain a waste treatment facility of a scale commensurate with the current demographics in the future.

In addition, financial tightness has already become apparent in many local governments, and the initial costs associated with the necessary renewal of waste treatment facilities, future maintenance costs, and the costs required for dismantling and removal are extremely high. For this reason, many local governments have managed to preserve the aging treatment facilities and postpone the problem.

In addition, since the waste currently incinerated by the local government contains a large amount of plastic mixture, it is a factor that damages the furnace due to the calorific value and the generation of toxic gas when simply incinerated.

On the other hand, plastic-based industrial waste has been exported to China, etc., but the import itself was banned because it causes environmental pollution in the importing country itself, but it is not the case at industrial waste treatment facilities in Japan. It is a big social issue because it cannot process the whole amount. Although the local government has no primary responsibility for the treatment of industrial waste, it also has the aspect of being asked for cooperation in the treatment. Furthermore, the treatment of combustible waste containing plastics has become a major social problem on a global scale, leading to an increase in carbon dioxide emissions.

The above-mentioned method for treating industrial waste includes a step of incinerating combustible waste, but instead of this step of incineration, organic waste is used in an anaerobic atmosphere using methanogens. It is possible to use a step (methane fermentation method) of fermenting biogas to produce biogas.

In this methane fermentation method, organic waste is hydrolyzed and acid-fermented by aerobic bacteria, then the organic waste is put into a methane fermentation tank, and new water is added to increase the water content of the organic waste. This is a method for generating biogas from organic waste by adjusting and fermenting an organic substance using a methanogen which is an anaerobic bacterium (see, for example, Patent Documents 1 and 2). The methane gas produced in this way is used as fuel. In addition, the digestive juice and solidified matter obtained from organic waste by the methane fermentation method can be used as an excellent fertilizer because they contain a large amount of nitrogen compounds necessary for plant growth.

However, in the conventional methane fermentation method, the hydrolysis and acid fermentation of organic waste using aerobic bacteria are not sufficient, and the organic waste is not satisfactorily reduced in molecular weight, so that the digestibility of organic matter is very high. There wasn't.

Further, in the conventional methane fermentation method, when the packaged food waste or the food waste contained in the plastic container is used as a raw material, the package or the plastic container is not decomposed or fermented by bacteria, so that the package or the plastic container is decomposed. It is necessary to remove these from fertile organic waste, which causes problems such as inefficiency and increased cost. In addition, food waste contains salt that matches the taste of humans, and this salt concentration may be so high that it adversely affects the growth and fermentation of bacteria.

As a method for solving such a problem, a method using sub-critical water treatment for reducing the molecular weight and volume of organic waste has been developed (see, for example, Patent Document 3). Sub-critical water treatment is a method of solubilizing organic waste by contacting it with liquid sub-critical water under high temperature and high pressure, which is a high temperature below the critical temperature of water and a high pressure above the saturated water vapor pressure. This is a method that can decompose packages and plastic containers that could not be decomposed by the conventional low molecular weight treatment. Therefore, even when the packaged food waste or the food waste contained in the plastic container is reduced in molecular weight, it can be solubilized together with the food waste without removing the package or the plastic container.

Japanese Unexamined Patent Publication No. 50-135279 JP-A-2002-119937 Japanese Unexamined Patent Publication No. 2003-117526 Patent No. 5792450 Patent No. 6327991 Patent No. 6377087 Patent No. 5796136 Patent No. 6120427

However, simply solubilizing organic waste by such sub-critical water treatment does not have a high efficiency of energy generation from organic waste, and has a problem in consideration of practicality. .. Further, in the prior art, there is a practical problem in the treatment of the fermentation residue.

Therefore, the present invention has been made in view of the above circumstances, and biogas is generated from organic waste with high efficiency to be used as an energy source for power generation, and fermentation residue and digestive juice are appropriately treated. It is an object of the present invention to provide an organic waste treatment system that produces almost no waste. Further, the present invention is not fixed to a waste treatment plant, but is housed in a plurality of movable containers or the like, so that the area for treating organic waste can be temporarily treated as needed. The purpose is to provide an organic waste treatment system that can be installed in.

In order to solve the above problems, the present inventors have conducted intensive research on an organic waste treatment system that produces energy and valuable by-products from organic waste by utilizing biomass technology. As a result, the present inventors have conducted intensive research on a raw material for methane fermentation. By reducing the molecular weight of certain organic waste in advance, methane fermentation can be performed with high efficiency, and by selectively separating carbon dioxide from the biogas produced by methane fermentation, a general-purpose natural gas generator can be used. We have invented the organic waste treatment system of the present invention, which enables power generation and further utilizes the obtained carbon dioxide, fermentation residue and digestive juice effectively to generate almost no waste.

Therefore, the organic waste treatment system of the present invention
Sub-critical water treatment equipment that reduces the molecular weight of organic waste,
A methane fermentation device that produces biogas from low-molecular-weight organic waste by methanogens,
A gas refiner that removes carbon dioxide from the biogas produced by methane fermentation,
Equipped with a solid-liquid separation device that pressurizes and floats and separates harmful substances from the digestive juice produced by methane fermentation.
At least one of the sub-critical water treatment device, the methane fermentation device, the gas purification device, and the solid-liquid separation device is a movable unit.
The unit is characterized in that it is transported to a place where organic waste treatment is carried out, assembled and installed there, and then disassembled and carried out.

Further, in the organic waste treatment system of the present invention, it is preferable that the unit is housed in a container. Further, in the organic waste treatment system of the present invention, it is preferable that all of the subcritical water treatment device, the methane fermentation device, the gas purification device, and the solid-liquid separation device are movable units.

The organic waste treatment system of the present invention is a microgrid facility, and waste is generated as needed by dividing the entire system or making a part of the system movable. It can be transported and installed in the place where it is to be used, eliminating the need for separate equipment such as a waste collection vehicle and manpower. The operation of the sub-critical water treatment apparatus (reference numeral 2 in FIG. 1 and the whole in FIG. 2) is a batch process with an operation time of about 2 hours. For this reason, it is possible to patrol the sub-critical water treatment equipment mounted on the vehicle in search of equipment after the methane fermentation equipment. This makes it possible to significantly reduce the initial capital investment.

Further, in the organic waste treatment system of the present invention, it is preferable to provide a desulfurization apparatus for removing sulfide components between the methane fermentation apparatus and the gas purification apparatus. Further, in the organic waste treatment system of the present invention, it is preferable to provide an advanced water treatment device for further separating the solid content from the digestive juice after the solid-liquid separation device.

Further, in the organic waste treatment system of the present invention, the organic waste treated in the methane fermentation apparatus preferably has a water content of 90% or more. Furthermore, in the organic waste treatment system of the present invention, the organic waste treated in the methane fermentation apparatus preferably has a solubilization rate of 50% or more.

In addition, if the plastic cannot be completely separated by this system and remains in the solid-liquid separator, the plastic can be gasified by the carbonization device (residual gasifier) and reused as fuel for the high-pressure boiler. That is, in the present invention, when plastic residue is found in the solid content discharged after the individual liquid separation device, the residual plastic is recovered and a separately installed residual gasification device is provided to generate carbonization gas. However, it is preferable to provide a residual gasifier to be used as fuel in a high-pressure boiler.

According to the organic waste treatment system of the present invention, waste can be treated without constructing a waste treatment plant that requires a high construction cost even in an area where there is little organic waste to be treated. In addition, biogas is generated from organic waste with high efficiency and used as an energy source for power generation, and by appropriately treating fermentation residue and digestive juice, almost no waste is generated and organic waste is disposed of. Can process things. That is, according to the organic waste treatment system of the present invention, energy and valuable resources can be created without adversely affecting the global environment by making full use of biotechnology. Furthermore, by introducing these mechanisms, a small-scale and completely self-contained energy recycling society can be formed.

It is a conceptual diagram which showed the whole flow of the organic waste treatment system of this invention. It is a conceptual diagram which shows one Embodiment of the sub-critical water treatment apparatus in the organic waste treatment system of this invention. It is a conceptual diagram which shows one Embodiment of the methane fermentation apparatus in the organic waste treatment system of this invention. It is a conceptual diagram which shows one Embodiment of the desulfurization apparatus in the organic waste treatment system of this invention. It is a conceptual diagram which shows one Embodiment of the gas purification apparatus in the organic waste treatment system of this invention. It is a conceptual diagram which shows one Embodiment of the solid-liquid separation apparatus in the organic waste treatment system of this invention. It is a conceptual diagram which shows one Embodiment of the advanced water treatment apparatus in the organic waste treatment system of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.

FIG. 1 is a conceptual diagram showing the overall flow of the organic waste treatment system of the present invention. In the organic waste treatment system of the present invention, first, as shown in FIG. 1, the organic waste 1 is put into the sub-critical water treatment apparatus 2 and treated with sub-critical water to treat the properties and shape. Is a uniform methane fermentation raw material. Next, this methane fermentation raw material is transferred to a methane fermentation apparatus 3 and fermented by a methanogen for about 20 days to produce biogas and digestive juice. The generated biogas is purified into a flammable gas by removing the sulfide component by the desulfurization device 4 and further removing carbon dioxide by the gas purification device 5. Since the flammable gas thus obtained has a calorific value equivalent to that of natural gas, it can be supplied as a good energy source for a general-purpose natural gas generator 6.

On the other hand, since the digestive juice produced by methane fermentation contains a fermentation residue, the fermentation residue is separated from the digestive juice by using the solid-liquid separation device 7. Since the separated fermentation residue contains a large amount of organic components in the process of decomposition, this fermentation residue can be effectively used as fertilizer. Further, since the separable component is still dissolved in the separated digestive juice, the advanced water treatment apparatus 8 further separates the solid content from the digestive juice, and the solid content is returned to the solid-liquid separation apparatus 7. Thereby, the digestive juice is treated to a level that meets the wastewater standard. In the organic waste treatment system of the present invention, it is necessary to adjust the water content in the sub-critical water treatment device 2, the methane fermentation device 3 or the solid-liquid separation device 7 to an appropriate range. It is also possible to reuse the digestive juice treated by the advanced water treatment apparatus 8.

As described above, according to the organic waste treatment system of the present invention, biogas is generated from organic waste with high efficiency, the digestive juice is treated until the wastewater standard is satisfied, and the fermentation residue is used as fertilizer. Is possible.

Here, in the organic waste treatment system of the present invention, at least one of a subcritical water treatment device, a methane fermentation device, a gas purification device and a solid-liquid separation device is housed in, for example, a container and is movable. By making it a unit, it becomes possible to share expensive equipment and equipment with a short usage period in multiple areas that require disposal, and the introduction and operation costs of organic waste treatment systems can be significantly reduced. Can be done. Further, in the organic waste treatment system of the present invention, all the devices of the subcritical water treatment device, the methane fermentation device, the gas purification device and the solid-liquid separation device are, for example, movable units housed in a container. This allows these units to be transported, assembled and installed there, for waste treatment, as needed, without the need to build a facility equipped with an organic waste treatment system. Later, it is possible to disassemble and carry out this system. Hereinafter, each step in the organic waste treatment system of the present invention will be described in more detail with reference to FIGS. 2 to 8.

<Sub-critical water treatment equipment>
FIG. 2 is a conceptual diagram showing an embodiment of a sub-critical water treatment device in the organic waste treatment system of the present invention. FIG. 2 shows a state in which the sub-critical water treatment device 2 in the organic waste treatment system of the present invention is housed in the container 11 and loaded on the large vehicle 12. In addition, M in the figure means a motor, and is provided for moving or agitating organic waste in the apparatus. The sub-critical water treatment device 2 in the organic waste treatment system of the present invention housed in the container 11 in this way is separated from other components, and the container 11 can be easily moved together. Further, other components described later can also be housed in the container in the same manner and can be easily moved.

In the organic waste treatment system of the present invention, the organic waste 1 is charged into the sub-critical water treatment apparatus 2 and treated with sub-critical water to reduce the molecular weight of the organic waste 1 before methane fermentation. , It is used as a methane fermentation raw material with uniform properties and shape. Such a methane fermentation raw material makes it possible to satisfactorily generate biogas from the organic waste 1 in an extremely short time. Specifically, the reduction in molecular weight of the organic waste 1 in the present invention is a step of decomposing carbohydrates, proteins, fats and the like into sugars, amino acids, higher fatty acids and the like, respectively. Examples of the sub-critical water treatment apparatus that can be used in the present invention include the apparatus described in Patent Documents 4 to 6.

The sub-critical water treatment in the organic waste treatment system of the present invention is a liquid under high temperature and high pressure (for example, 200 ° C., 20 atm), which is a high temperature below the critical temperature of water and a high pressure above the saturated water vapor pressure. This is a method of reducing the molecular weight of sub-critical water by bringing it into contact with organic matter. Since this sub-critical water has a dielectric constant of 15 to 45, which is equivalent to the dielectric constant of a low-polar solvent, many organic substances can be dissolved, and the ion product is ^10-12 to ^10-11 mol ^2. Since the ratio of separation into hydrogen ions and hydroxide ions is large at / kg ^{2, it has a strong hydrolysis action.} The permittivity of water at room temperature and atmospheric pressure is about 80, and the ion product is ^10-14 mol ² / kg ² at an atmospheric temperature of about 25 ° C.

In addition, subcritical water treatment can also decompose plastics such as polypropylene and polyethylene by the strong hydrolysis action as described above, so that it cannot be hydrolyzed by anaerobic bacteria or aerobic bacteria, paper, vinyl, etc. Plastics, foamed styrol, infectious medical waste, clothing containing chemical fibers, waste food as it is packaged, and the like can also be reduced in molecular weight.

The low molecular weight organic waste in the present invention has a solubilization rate of 50% or more, preferably a solubilization rate of 70% or more, and more preferably a solubilization rate of 85% or more. Here, the solubilization rate is the ratio of the soluble organic matter to the total organic matter used in the methane fermentation, and the higher the value, the lower the molecular weight of the organic matter.

Further, the sub-critical water treatment in the organic waste treatment system of the present invention is a batch treatment due to its nature, but in the present invention, it can be carried out at a ratio of several batches / day. Further, the sub-critical water treatment apparatus 2 in the present invention may be provided with a high-pressure boiler 13 in order to supply high-temperature and high-pressure steam. Further, the water supply to the high-pressure boiler 13 can reuse not only tap water but also digestive juice.

<Methane fermentation equipment>
Next, the organic waste 1 whose molecular weight is reduced by the sub-critical water treatment apparatus 2 as described above is used as a raw material for methane fermentation, and the methane fermentation apparatus 3 performs methane fermentation to generate biogas and digestive juice. .. FIG. 3 is a conceptual diagram showing an embodiment of the methane fermentation apparatus 3 in the organic waste treatment system of the present invention. The methane fermentation apparatus 3 in the present invention is, for example, an apparatus including a processed product storage tank 21, a methane fermentation tank 22, and a digestive juice receiving tank 23 from the upstream side. The organic waste 1 whose molecular weight has been reduced by the sub-critical water treatment apparatus 2 is sent to the methane fermentation tank 22 in a required amount after the water content is adjusted in the treated product storage tank 21. In the figure, M means a motor and is provided to gently agitate organic waste in a methane fermentation tank, and P means a pump to send a mixed solution from each tank. It is provided in.

The treated product storage tank 21 of the methane fermentation apparatus 3 in the present invention contains the organic waste 1 having a low molecular weight in the sub-critical water treatment apparatus 2 and tap water or the digestive juice produced by the previous methane fermentation. This is for preparing a mixed solution by mixing so that the ratio is 90% or more. Further, the processed product storage tank 21 is provided with a powerful stirring means, and the mixed liquid supplied to the methane fermentation tank 22 can be sufficiently mixed.

The organic waste 1 whose molecular weight has been reduced by the sub-critical water treatment apparatus 2 usually has a water content of 20 to 30% when it is put into the treated product storage tank 21. In the present invention, this water content is adjusted to 90% or more by adding tap water or a previously produced digestive juice. General methane fermentation includes wet fermentation for organic waste with a solid content concentration of 6 to 10% (moisture content 90 to 94%) and solid content concentration of 25 to 45% (moisture content 55 to 75%). ), There is a dry fermentation targeting organic waste, but in the present invention, a wet fermentation is used in which the maintenance cost of the apparatus is low and the previously produced digestive juice can be reused.

The previously produced digestive juice is a digestive juice that has been processed and reused in the solid-liquid separation device 7 or the advanced water treatment device 8 described later. Therefore, the digestive juice may contain undigested substances such as methanogens and organic waste. Further, the mixture of the low molecular weight organic waste and the digestive juice mixed and stirred in the processed product storage tank 21 is an organic acid generated during the low molecular weight treatment, collection and storage of the organic waste. The pH tends to be acidic.

Further, in the present invention, since the concentration of the salt contained in the food waste is diluted by water or digestive juice in the processed product storage tank 21, it does not affect the methane fermentation in the methane fermentation tank 22.

Next, the low-molecular-weight organic waste 1 whose water content has been adjusted in this way is continuously supplied to the methane fermentation tank 22 as needed, and methane is generated in the methane fermentation tank 22 over about 20 days. Perform methane fermentation with bacteria. Since the methane fermentation tank 22 of the methane fermentation apparatus 3 in the present invention uses a methanogenic bacterium which is an anaerobic bacterium, the inside of the tank has an anaerobic environment and has a structure having a hermetically sealed structure so that oxygen does not enter from the outside of the tank. It is essential to be there. Therefore, the methane fermentation tank 22 is preferably made of a closed cylindrical steel plate.

Since the methanogenic bacteria are anaerobic bacteria, in the methane fermentation tank 22, the low molecular weight organic waste 1 having an adjusted water content may be gently agitated so that the methane fermentation proceeds uniformly, and violently. Do not stir to disturb the anaerobic environment of the mixture. Immediately after the low molecular weight organic waste 1 having an adjusted water content is supplied to the methane fermentation tank 22, oxygen is contained in the methane fermentation tank 22, so that oxygen is consumed by aerobic bacteria. , Methan fermentation is started after the environment becomes anaerobic.

Further, the methane fermentation tank 22 is provided with a temperature control means for growing the methanogenic bacteria and maintaining the temperature at which the organic matter is methane-fermented, and further provided with a stirring means for gently stirring the contents in the tank. ing. Since the methanogenic bacterium is an anaerobic bacterium, gentle stirring is required so as not to disturb the anaerobic environment in the methane fermenter 22. Specific examples of the stirring means of the methane fermentation tank include those provided with a screw pump in the draft tube, those using a gas lift (non-powered methane fermentation tank), and those having a large stirring diameter.

The methanogen used in the present invention is for medium-temperature fermentation whose decomposition rate increases in a medium-temperature environment (about 35 ° C) even if it is a methanogen for high-temperature fermentation whose decomposition rate increases in a high-temperature environment (about 55 ° C). May be a methanogen. Although the number of types of methanogens for high-temperature fermentation is small and a large amount of energy is required to reach the fermentation temperature, the methane production time is short and the amount of methane produced is large. Therefore, in the present invention, methane production for high-temperature fermentation is performed. It is preferable to use a bacterium.

Further, in the present invention, a pH measuring means or a redox potential measuring means is provided in the methane fermentation tank to measure the pH or redox potential of low molecular weight organic waste having an adjusted water content during methane fermentation. , It is preferable to control the value to an appropriate value. A neutral pH of 7 to 8 is preferable, and if the pH is too low, the growth rate of methanogens will decrease, and the amount of biogas produced will decrease. Therefore, when the pH is too low, the pH is adjusted to 7 to 8 by reducing the supply amount of the raw material that is inclined to acidity. However, if this does not result in neutrality, baking soda is added to the low molecular weight organic waste to control the pH. On the other hand, when the pH is too high, the pH is adjusted to 7 to 8 by increasing the supply amount of the raw material that is inclined to acidity. Further, the redox potential is preferably −0.33 V or less, and if the redox potential is too high, fermentation by methanogens, which are anaerobic bacteria, will not proceed.

By the above-mentioned methane fermentation, biogas can be generated from low molecular weight organic waste with high efficiency of digestibility of 85% or more while reusing the digestive juice to be treated as wastewater. Further, in the present invention, by preparing in advance low molecular weight organic waste having an adjusted water content in the processed product storage tank 21, the digestive juice receiving tank is linked to the end of methane fermentation in the methane fermentation tank 22. The discharge of the digested liquid to 23 and the supply of the mixed liquid from the processed product storage tank 21 may be automated, whereby continuous methane fermentation can be carried out.

In the organic waste treatment system of the present invention, the digestive juice produced in the methane fermentation tank 22 is stored in the digestive juice receiving tank 23 in order to temporarily store the digestive juice applied to the digestive juice treatment described later. You may. The digestive juice at this stage still contains separable organic components and the like, and often does not meet the wastewater standards as it is.

<Desulfurization equipment>
In the present invention, in order to increase the efficiency of power generation, it is preferable to provide a desulfurization apparatus 4 for removing a sulfide component from the biogas obtained by the above-mentioned methane fermentation. Since the biogas produced in the above-mentioned methane fermentation apparatus 3 contains a sulfide component, the inclusion of this sulfide component becomes a problem in the subsequent power generation. FIG. 4 is a conceptual diagram showing an embodiment of the desulfurization apparatus 4 in the organic waste treatment system of the present invention.

The desulfurization apparatus 4 in the present invention is composed of, for example, a cooler 31, a desulfurization tower 32, and a gas holder 33 from the upstream side. In the desulfurization apparatus 4 of the present invention, first, the biogas produced by the methane fermentation apparatus is cooled to room temperature by passing the biogas through the cooler 31. Next, the cooled biogas is guided into the desulfurization tower 32 to remove the sulfurized component. The biogas desulfurized in this way is temporarily stored in the gas holder 33.

<Gas purification equipment>
Biogas produced by methane fermentation usually has a methane concentration in the range of 40 to 70% and contains a high concentration of carbon dioxide, so a special biogas generator is required to generate electricity. .. This type of generator is very expensive due to its narrow sales area and not mass production. Therefore, in the present invention, a natural gas engine that combines a gas engine and a generator by removing carbon dioxide from biogas and converting it into methane-rich gas using a gas purification device provided with a carbon dioxide selective permeation film. Can be used as a power generation facility.

FIG. 5 is a conceptual diagram showing an embodiment of the gas purification apparatus 5 in the organic waste treatment system of the present invention. The gas purification device 5 in the present invention has a function of selectively removing carbon dioxide from the biogas stored in the gas holder 33 in the desulfurization device 4 and supplying the biogas to the generator 42 via the blower 41. have. When surplus biogas is generated, the surplus gas can be safely burned by the gas flare 43 in terms of operation management.

The gas purification apparatus 5 in the present invention has a function of controlling the permeation of carbon dioxide in biogas, and as the carbon dioxide selective permeation membrane, for example, the CO ₂ promoting transport membrane disclosed in Patent Document 7 is used. Can be used. The CO ₂ -facilitated transport membrane has a configured separation function layer contains CO ₂ carrier and CO ₂ hydration catalyst gel film of the hydrophilic polymer. The above-mentioned CO ₂ carrier is composed of carbonates, bicarbonates, and hydroxides of alkali metals such as cesium and rubidium that selectively react with _{CO 2.} The above-mentioned CO ₂ hydration catalysts having a catalytic activity at a temperature above 100 ° C., or are those having a melting point of 200 ° C. or higher, for example, tellurite compound, selenite compound, It is composed of a tellurous acid compound, an orthosilicic acid compound, a molybdic acid compound and the like. Further, as the gel film, a hydrogel is used, and further, a polyvinyl alcohol-polyacrylate copolymer gel film is used.

In such a CO ₂ promoting transport membrane, combustible gas such as methane gas that does not react with _{CO 2 carriers permeates only by the dissolution / diffusion mechanism.} In contrast, CO ₂ in addition to the physical transmission due to dissolution and diffusion mechanism, for transmitting as the reaction product of CO ₂ carrier, permeation rate is accelerated. Therefore, according to this CO _{2 promoting transport membrane, CO 2} having an extremely large separation coefficient as compared with a flammable gas such as methane gas can be selectively separated. Therefore, in the organic waste treatment system of the present invention, it is possible to remove carbon dioxide from the biogas produced by methane fermentation by using the gas purification apparatus 5 provided with _{such a CO 2 promoting transport film.} It is said.

In addition, the carbon dioxide membrane-separated in this way has high purity, and unlike engine exhaust gas used in ordinary trigeneration, it is of good quality and does not contain SOx or NOx, so it is not released to the atmosphere as it is. , It is preferable to effectively utilize it in a plant factory or the like.

<Solid-liquid separator>
Since the digestive juice produced in the methane fermentation apparatus 3 contains a large amount of fermentation residue, it is necessary to separate the fermentation residue from this digestive juice. FIG. 6 is a conceptual diagram showing an embodiment of the solid-liquid separation device 7 in the organic waste treatment system of the present invention. In the figure, M means a motor and is provided to agitate the digestive juice in each tank of the solid-liquid separator, and P means a pump to send the solution from each tank. It is provided.

The solid-liquid separation device 7 in the present invention includes, for example, a sulfuric acid storage tank 51, a dehydration assisted dissolution tank 52, a reaction tank / dehydrator 53, a dehydration filtrate tank 54, an agglutination reaction tank 55, an inorganic flocculant 56, and a pressurized flotation tank. It is composed of 57.

In this solid-liquid separation device 7, the fermentation residue is separated in the first half on the left side of FIG. Specifically, first, the digestive juice after methane fermentation is transferred to the reaction tank / dehydrator 53. At this time, a dehydration aid dissolved in tap water or digestive juice by stirring in the dehydration aid dissolution tank 52 may be added, and if necessary, sulfuric acid stored in the sulfuric acid storage tank 51 may be added for digestion. The pH of the solution may be in an appropriate range. In this reaction tank / dehydrator 53, the digestive juice is appropriately stirred and then the solid content is separated. Further, in this reaction tank / dehydrator 53, it is also possible to separate the solid content again from the digestive juice obtained in the step described later. Since the fermentation residue separated as a solid content contains a large amount of organic components in the process of decomposition, this fermentation residue can be effectively used as fertilizer.

Next, the digestive juice from which the solid content has been separated is temporarily stored in the dehydration filtration tank 54 and then transferred to the agglutination reaction tank 55, where the inorganic flocculant 56 is added to the digestive juice as needed. The pressure levitation process following this process is shown in the latter half on the right side of FIG. As the pressurized flotation tank 57 in the present invention, for example, the pressurized flotation device disclosed in Patent Document 8 can be used.

In the pressurized flotation tank 57 of the present invention, the suspended component or the dissolved component is digested by adhering ultrafine bubbles to the component suspended or dissolved in the digestive juice to reduce the apparent specific gravity. It is a device that floats and separates from. Here, the pressurized flotation tank 57 in the present invention will be described in detail. First, in the pressurized flotation tank 57, the digestive juice is supplied from the agglutination reaction tank 55 on the upstream side. Then, when the digestive juice is stored in the pressurized flotation tank 57 in a predetermined amount or more, the components suspended in the digestive juice are dissolved by sending out ultrafine bubbles to the digestive juice from below. Adhere ultrafine bubbles to the components. The ultrafine bubbles are generated in water by reopening water in which air is pressurized and dissolved under atmospheric pressure, and have a diameter of about 0.3 to 1 nm. Due to the adhesion of the ultrafine bubbles, the suspended component and the dissolved component are floated to the liquid surface and separated from the digestive juice. Since the components floating and separated in this way contain harmful heavy metals, a digestive juice from which harmful heavy metals have been removed can be obtained through this step.

Therefore, the solid-liquid separation device 7 in the organic waste treatment system of the present invention is provided with such a pressurized flotation tank 57, so that harmful heavy metals dissolved in the digestive juice are placed at the interface of ultrafine bubbles. It can be adsorbed and separated. The digestive juice obtained here is further separated in the next advanced water treatment apparatus, and may be reused in the sub-critical water treatment apparatus 2 and the methane fermentation apparatus 3 at this stage.

<Residual gasifier>
In the solid-liquid separator in the organic waste treatment system of the present invention, if the solid content discharged from the reaction tank / dehydrator 53 contains a plastic component in an insufficiently decomposed state, FIG. 2 shows. As shown, they are charged into the residue gasifier 14 connected to the high pressure boiler 13. The dry distillation gas is extracted from the plastic component by the residual gasifier 14, and burned in a high-pressure boiler to utilize heat. This makes it possible to completely eliminate waste outside the organic waste treatment system of the present invention.

<Advanced water treatment equipment>
In the present invention, the digestive juice treated in the solid-liquid separation device 7 as described above is further subjected to membrane separation biological treatment to re-separate the active ingredient contained in the digestive juice and utilize it as fertilizer or the like. FIG. 7 is a conceptual diagram showing an embodiment of an advanced water treatment device 8 in the organic waste treatment system of the present invention. In addition, P in the figure means a pump, and is provided for sending a solution from each tank. The digestive juice sent from the pressurized flotation tank 57 of the solid-liquid separation device 7 is brought into contact with fine bubbles in the aeration tank 61 and the membrane separation tank 62 to remove insoluble components. Next, the digestive juice from which the insoluble component has been removed is temporarily stored in the reverse osmosis raw water tank 63, and then separated into solid content and digestive juice in the reverse osmosis apparatus 64. The solid content separated here is used as fertilizer, and the digestive juice may be disposed of as long as it meets the wastewater standard, but after being stored in the circulating water tank 65, the above-mentioned sub-critical water treatment apparatus 2 , Is sent to the methane fermentation apparatus 3 or the solid-liquid separation apparatus 7 for reuse.

As described above, according to the organic waste treatment system of the present invention, even in an area where there is little organic waste to be treated, the waste can be disposed of without constructing a waste treatment plant that requires a high construction cost. It is possible to process things, and moreover, biogas is generated from organic waste with high efficiency and used as an energy source for power generation, and most of the waste is generated by appropriately treating fermentation residue and digestive juice. Organic waste can be treated without.

1 Organic waste 2 Subcritical water treatment equipment 3 Methane fermentation equipment 4 Desulfurization equipment 5 Gas purification equipment 6 Generator 7 Solid-liquid separation equipment 8 Advanced water treatment equipment 11 Container 12 Large vehicle 13 High-pressure boiler 14 Residual gasifier 21 Treatment Storage tank 22 methane fermentation tank 23 digestive liquid receiving tank 31 cooler 32 desulfurization tower 33 gas holder 41 blower 42 generator 43 gas flare 51 sulfuric acid storage tank 52 dehydration aid dissolution tank 53 reaction tank / dehydrator 54 dehydration filtration tank 55 coagulation reaction tank 56 inorganic Coagulant 57 Pressurized levitation tank 61 Desulfurization tank 62 Membrane separation tank 63 Reverse osmosis raw water tank 64 Reverse osmosis device 65 Circulating water tank

Therefore, the organic waste treatment system of the present invention
Sub-critical water treatment equipment that reduces the molecular weight of organic waste,
A methane fermentation device that produces biogas from low-molecular-weight organic waste by methanogens,
A gas refiner that removes carbon dioxide from the biogas produced by methane fermentation,
Equipped with a solid-liquid separation device that pressurizes and floats and separates harmful substances from the digestive juice produced by methane fermentation.
At least one of the sub-critical water treatment device, the methane fermentation device, the gas purification device, and the solid-liquid separation device is a movable unit.
The unit is transported to a place where organic waste treatment is carried out, where it is assembled and installed, and after that, it is disassembled and carried out .
If plastic residue is found in the solids discharged after the solid-liquid separation device, the residual plastic is recovered, and a separately installed residual gasifier is provided to generate dry distillation gas, which is used as fuel in a high-pressure boiler. It is characterized by being equipped with a residue gasifier to be used.

In addition, if the plastic cannot be completely separated by this system and remains in the solid-liquid separator, the plastic can be gasified by the carbonization device (residual gasifier) and reused as fuel for the high-pressure boiler. That is, in the present invention, when plastic residue is found in the solid content discharged after the solid- liquid separation device, the residual plastic is recovered and a separately installed residual gasification device is provided to generate carbonization gas. However, it is preferable to provide a residual gasifier to be used as fuel in a high-pressure boiler.

Claims (8)

Sub-critical water treatment equipment that reduces the molecular weight of organic waste,
A methane fermentation device that produces biogas from low-molecular-weight organic waste by methanogens,
A gas refiner that removes carbon dioxide from the biogas produced by methane fermentation,
Equipped with a solid-liquid separation device that pressurizes and floats and separates harmful substances from the digestive juice produced by methane fermentation.
At least one of the sub-critical water treatment device, the methane fermentation device, the gas purification device, and the solid-liquid separation device is a movable unit.
An organic waste treatment system characterized in that the unit is transported to a place where organic waste treatment is carried out, assembled and installed there, and then disassembled and carried out. The organic waste treatment system according to claim 1, wherein the unit is housed in a container. The organic waste treatment system according to claim 1 or 2, wherein the subcritical water treatment device, the methane fermentation device, the gas purification device, and the solid-liquid separation device are all movable units. .. The organic waste treatment system according to any one of claims 1 to 3, further comprising a desulfurization apparatus for removing a sulfide component between the methane fermentation apparatus and the gas purification apparatus. The organic waste treatment system according to any one of claims 1 to 4, further comprising an advanced water treatment device for further separating solids from the digestive juice after the solid-liquid separation device. If plastic residue is found in the solids discharged after the individual liquid separation device, the residual plastic is recovered, and a separately installed residual gasifier is provided to generate carbonization gas, which is used as fuel in a high-pressure boiler. The organic waste treatment system according to any one of claims 1 to 5, further comprising a residue gasification device to be used. The organic waste treatment system according to any one of claims 1 to 6, wherein the organic waste treated in the methane fermentation apparatus has a water content of 90% or more. The organic waste treatment system according to any one of claims 1 to 7, wherein the organic waste treated in the methane fermentation apparatus has a solubilization rate of 50% or more.

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