JP4223419B2 - Bioreactor and organic waste energy recovery system using the same - Google Patents

Description

  The present invention relates to a bioreactor and an organic waste energy recovery system using the bioreactor. More specifically, the present invention relates to a bioreactor that is energy-saving and excellent in fermentation ability, and an organic waste energy recovery system using the bioreactor.

A bioreactor using an anaerobic digestion method is known as a method for treating organic waste (for example, human waste, septic tank sludge, and garbage). A typical anaerobic digestion method includes a methane fermentation treatment method. According to the methane fermentation treatment method, biogas (methane is about 65% to 70% and carbon dioxide is about 35% to 30%) is finally generated, and the biogas has a calorific value of about 6,000 kcal / m ³ . Therefore, there is an advantage that it can be recovered as energy.

  Specific examples of the methane fermentation treatment method include a UASB (Upflow Anaerobic Sludge Blanket) method, a fixed bed method, and a floating bed method. For example, when processing garbage using the methane fermentation treatment method, methane fermentation treatment is usually performed after pulverizing and solubilizing the garbage to prepare a stock solution. However, there is a problem with any of the above specific methane fermentation treatment methods because raw garbage contains a high concentration of organic substances and contains a large amount of suspended substances (solid content: SS). There is. Specifically, in the UASB method, when SS enters the bioreactor (methane fermentation tank), the granulated microorganisms flow out of the tank. In the fixed bed method, SS clogs the carrier. In the floating bed method, it takes a long time to decompose high-concentration organic substances, and the bioreactor becomes very large.

  Furthermore, a methane fermenter of a non-powered stirring type has been developed due to the recent increase in awareness of environmental problems. For example, as shown in FIGS. 6A to 6D, a methane fermenter is known in which a stock solution is stirred using the pressure of generated biogas. Specifically, as follows: First, as shown in FIG. 6A, the liquid level A of the main fermentation unit 601 and the upper chamber 602 is constant, and the pressure equalizing valve 603 is closed. . When digestion gas (biogas) is generated in the main fermentation unit 601, as shown in FIG. 6 (b), the liquid level A is lowered by the gas pressure, the stock solution is pushed up from the mixing shaft 604, and the liquid level B is raised. To do. When the digestion gas is sufficiently generated, the liquid level B reaches the highest level C as shown in FIG. Along with this, a certain amount of stock solution is supplied to the center tube 605. Finally, as shown in FIG. 6 (d), when the pressure equalizing valve 603 is opened, the gas pressures of the high pressure phase and the low pressure phase become the same, and the liquid in the upper chamber 602 passes through the center tube 605 to the main fermentation unit 601. It flows in vigorously and mixing and stirring are performed. However, such a fermenter has insufficient stirring efficiency, and as a result, fermentation capacity (biogas generation capacity) is insufficient.

  As described above, there is a strong demand for a bioreactor that is energy-saving and excellent in fermentation ability.

JP 2000-167523 A Japanese Patent Laid-Open No. 2001-998

The present invention has been made in order to solve the above-described conventional problems, and an object of the present invention is a bioreactor that is energy-saving and excellent in fermentation capacity and energy recovery of organic waste using the bioreactor. To provide a system.

  The bioreactor of the present invention comprises a fermenter that forms an anaerobic state by forming a closed space, ferments raw water containing organic waste, and generates biogas by methane fermentation; a main heating unit extending vertically; A heating means for heating the raw water disposed in the fermenter, and having a connecting part arranged to alternately connect the upper end parts and the lower end parts of the main heating part; And a stirring means having a cylindrical shape and disposed so as to pass the main heating part of the heating means through the hollow part.

  In a preferred embodiment, the heating means includes hot water prepared by a solar heater, hot water prepared by a hot water boiler using the biogas as a heat source, or surplus of power generation means that generates electric power using the biogas. It is a hot water pipe using hot water prepared by heat.

  In a preferred embodiment, the inner diameter of the stirring means is 350 to 800% of the inner diameter of the hot water pipe.

  In preferable embodiment, the said stirring means is arrange | positioned at the peripheral part vicinity at least of the said fermenter.

  In a preferred embodiment, the stirring means stirs the raw water without consuming electric power and power by using the biogas and the convection of the raw water as driving sources.

  According to another aspect of the present invention, an organic waste energy recovery system is provided. This system comprises a slurrying means for making organic waste into a slurry; the bioreactor for methane fermentation of the slurry to digest it into biogas and digestive fluid; and a power generation means for generating electric power and heat from the biogas. And a secondary treatment facility for purifying residual organic matter contained in the digested liquid and precipitating surplus sludge as compost material, and heating the bioreactor to an appropriate temperature by heat from the power generation means, A portion of the power from the means drives the slurrying means and the secondary treatment facility to produce power and compost material.

  In a preferred embodiment, the power generation means is a fuel cell.

  In a preferred embodiment, the system further comprises a methane purification facility between the bioreactor and the power generation means.

  According to the present invention, by using a cylindrical stirring means having a heating means in the hollow portion, the generated biogas and convection are used as a driving source, and raw water containing organic waste is efficiently and power-free. Can be stirred. Therefore, it is possible to obtain a bioreactor that is energy saving and excellent in fermentation ability. Furthermore, according to the energy recovery system of the present invention, the bioreactor and the equipment in the system are operated using a part of the electric power and heat obtained by using the generated biogas, so that the electric power and the electric power can be substantially reduced with zero emission. Compost material can be obtained. In addition, according to the present invention, problems such as generation of dioxins and land subsidence in the conventional organic waste processing method do not occur.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments.

  FIG. 1 is a flowchart illustrating an organic waste recovery system according to a preferred embodiment of the present invention. Organic waste (for example, human waste, septic tank sludge, raw garbage) is put into the receiving tank 1 and diluted with dilution water. In the receiving tank 1, foreign matters (typically sand) not related to methane fermentation are removed by precipitation, and therefore the receiving tank 1 is also referred to as a sand settling tank. The organic waste from which the foreign matter has been removed by precipitation is crushed into a slurry by the crusher 2. Any appropriate means can be adopted as the crusher 2. For example, it may be a high-pressure pulverizer that pulverizes organic waste to a predetermined size with a screw cutter or the like and then finely pulverizes it by applying high pressure. It may be a pulverizer that grinds waste into a paste, or a combination thereof. The obtained slurry is temporarily stored in the raw water tank 3. The slurry (raw water) is sent to the bioreactor 4 by a predetermined amount by a slurry pump (not shown).

  FIG. 2 is a schematic cross-sectional view of an essential part for explaining a bioreactor according to a preferred embodiment of the present invention. FIG. 3 is a schematic plan view of the bioreactor of FIG. It should be noted that in FIGS. 2 and 3, a scale different from the actual scale is used for easy understanding. The bioreactor 4 includes a fermenter 41, a heating unit 42, and a stirring unit 43. The fermentation layer 41 forms an anaerobic state by forming a closed space, and methane fermentations the raw water in the tank. The heating means 42 includes a main heating part 44 extending in the vertical direction, and a connecting part 45 arranged so as to alternately connect upper end parts and lower end parts of the main heating part 44. The raw water in the fermentation layer 41 is heated to 35 ° C. to 45 ° C. by the heating means 42. Furthermore, the heating means 42 has a function of preventing the excessive movement of the stirring means 43 in the vertical direction by the connecting portion 45 and keeping it at a predetermined position. The heating means 42 is typically a hot water pipe. The hot water supplied to the pipe is preferably prepared by a solar heater or a hot water boiler. Preferably, the hot water boiler uses biogas generated in the bioreactor as a heat source, as will be described later. Alternatively, the hot water is used by collecting the reaction heat of the power generation means (fuel cell) 7 using biogas with cooling water, as will be described later. By using such hot water, the bioreactor can be operated completely with no power and no power consumption. The hot water pipe can be made of, for example, vinyl chloride resin or stainless steel. In the case of being composed of vinyl chloride resin, the main heating part 44 and the connecting part 45 are bonded with any appropriate adhesive. In the case of stainless steel, the main heating part 44 and the connecting part 45 are welded. The size of the heating means 42 (particularly the length of the main heating unit 44) can be changed according to the size of the fermenter 41. Typically, the length of the main heating unit 44 is 60 to 70% of the depth of the fermenter 41. Furthermore, the internal diameter of the heating means 42 is typically 1 to 2 cm.

  The stirring means 43 is typically a cylinder that defines the hollow portion 46, and is disposed so that the main heating portion 44 of the heating means 42 passes through the hollow portion 46. Therefore, although the stirring means 43 can move up and down along the main heating part 44, the movement is restricted between the upper and lower connecting parts as described above. The cylindrical wall 47 that defines the hollow portion 46 can typically be made of vinyl chloride resin or stainless steel. The length of the stirring means is typically 90 to 98%, preferably 90 to 95% of the length of the main heating unit 44 of the heating means 42. By adopting such a ratio, the stirring means can be moved up and down appropriately, and as a result, the stirring efficiency is improved. Furthermore, the internal diameter of the stirring means 43 is typically 7 to 8 cm. Expressed as a ratio to the inner diameter of the heating means 42, the inner diameter of the stirring means 43 is preferably 350 to 800% of the inner diameter of the heating means 42. By adopting such a ratio, convection of the raw water by the heating means is likely to occur in the hollow portion, and as a result, the stirring efficiency is improved.

  Arbitrary appropriate arrangement | positioning may be employ | adopted for arrangement | positioning of the stirring means 43 in the fermentation layer 41 according to the objective. Typically, as shown in FIG. 3, the agitation means 43 is provided in the vicinity of the peripheral portion of the fermentation layer 41 and the vicinity of the intermediate portion of the fermentation layer (that is, a straight line connecting the center and the outer periphery of the fermenter (with a radius). It can be placed near the midpoint of the straight line). This is because the heating efficiency by the heating means 42 and the stirring efficiency by the stirring means 43 are both excellent. Specific examples of other arrangement methods include a method of evenly arranging the entire fermentation layer when viewed in plan, a method of arranging in a matrix, a method of arranging radially, and a method of arranging in an X shape. .

  Next, the mechanism of stirring by the stirring means 43 will be described. When raw water methane fermentation proceeds in the fermentation layer 41, a large amount of digestion gas (biogas) is generated. The biogas moves upward, but the movement in the lateral direction is restricted by the cylindrical wall 47 of the stirring means 43. Therefore, most of the generated biogas moves upward in the hollow portion 46 of the stirring means 43 exclusively. As a result, the biogas serves as a driving source, and causes the raw water to flow upward in the hollow portion 46. At the same time, since the raw water in the vicinity of the heating means 42 is hotter than the raw water in other places, the raw water in the vicinity of the heating means 42 moves upward and convection occurs. This convection is also restricted from moving in the lateral direction by the cylindrical wall 47 of the stirring means 43, and moves exclusively upward in the hollow portion 46 of the stirring means 43. The raw water moves vigorously in the hollow portion 46 of the stirring means 43 by the synergistic effect of the flow using biogas as the driving source and the flow by convection. The raw water that has moved to the upper part of the fermenter pushes down the raw water that was originally in the upper part of the fermentation layer. The pushed-down raw water moves downward outside the stirring means 43 exclusively. By repeating this, the raw water in the fermenter circulates and agitation is promoted. The produced biogas is sent from the upper transfer pipe (not shown) to the methane purification facility 5, and the digested liquid is discharged from the discharge pipe (not shown) and sent to the secondary treatment facility 8.

As described above, 80 to 90% of the organic substances are decomposed in the bioreactor 4 to become biogas and digestive fluid. For example, when 1 ton of garbage having a CODcr value of about 300 g / L is decomposed in the bioreactor 4, biogas of about 130 Nm ³ is generated. The composition of the generated biogas is typically about 65% to 70% for methane, about 35% to 30% for carbon dioxide, and about 1500 ppm for hydrogen sulfide. When converted to calorific value, it becomes 800,000 kcal. According to the present invention, such energy can be obtained with absolutely no power and no power consumption.

  Referring to FIG. 1 again, the digestive juice is sent to the secondary treatment facility 8 to be purified (details of the secondary treatment of digestive juice will be described later). On the other hand, the biogas is supplied to the methane purification facility 5. Biogas is substantially a mixed gas of methane and carbon dioxide, but the concentration of methane in the biogas can vary greatly depending on the concentration of organic matter in the organic waste. Then, since stable power generation by the power generation means 7 is often difficult, it is necessary to maintain the methane concentration in the biogas supplied to the power generation means 7 preferably at 80% or more (more preferably 90% or more). Because there is. Furthermore, since hydrogen sulfide in the biogas becomes a catalyst poison of the power generation means 7, it is preferable to remove even a trace amount.

  Any appropriate configuration (for example, dry type or wet type) can be adopted as the methane purification facility 5. For example, as shown in FIG. 4, in the wet methane refining facility 50, the biogas is first washed with water in the washing tower 51, and carbon dioxide is absorbed and removed by water. The absorbed carbon dioxide is diffused in the diffusion tower 52 and only water is circulated to the flush tower 51 again. Next, the biogas is passed through the desulfurization tower 53, and desulfurized by washing with an alkaline aqueous solution containing sodium hydroxide. The alkaline wastewater after the desulfurization treatment can be neutralized with hydrochloric acid, for example, and then sent to the secondary treatment facility 8 to be treated together with the digested liquid from the methane fermentation tank 4. The hydrogen sulfide is finally discharged as waste water from the secondary treatment facility 8 as salts (for example, sodium sulfate).

  On the other hand, as shown in FIG. 5, in the dry methane purification facility 55, biogas is first desulfurized through the dry desulfurization tower 56, and then carbon dioxide is absorbed by water in the water washing tower 51. The dry desulfurization tower 56 is typically filled with a desulfurizing agent (for example, iron oxide). The desulfurizing agent is periodically replaced. The operation of the water washing tower 51 is as described in FIG. Carbon dioxide may be adsorbed and removed by a PSA (Pressure swing adsorption) type adsorption tower instead of the water washing tower 57.

  After removing carbon dioxide and hydrogen sulfide from the biogas, other trace impurities (for example, ammonia) may be further removed through an activated carbon adsorption tower (not shown) as necessary.

  The purified biogas is once stored in the gas holder 6 and then supplied to the power generation means 7 as fuel. By passing through the gas holder 6, it is possible to quantitatively supply the biogas to the power generation means 7. Note that the gas holder 6 can be reduced in size or omitted by supplementarily supplying city gas or the like to the power generation means 7 when the biogas is insufficient. City gas can also be used as a backup for biogas shortages.

  The power generation means 7 is preferably a fuel cell. Unlike a conventional gas engine, a fuel cell reacts electrochemically without burning biogas, so that power generation efficiency is as high as 40 to 50%. Moreover, NOx, SOx and soot are hardly contained in the exhaust gas, and it is clean. Furthermore, the amount of carbon dioxide emission is reduced by the amount of power generation efficiency. In addition, there is little noise and vibration.

  Preferably, a hot water boiler 9 is provided as auxiliary equipment. The hot water boiler 9 supplies high temperature water using the biogas as a heat source when the fuel cell 7 is stopped or when the biogas is excessive, and serves as a heating means 42 of the bioreactor 4, a heating heat source, a heat source of an absorption refrigeration machine, or the like. Further, the reaction heat of the fuel cell 7 can be recovered with cooling water and used for such a heat source.

  Part of the electric power obtained by the power generation means 7 can be used to operate the crusher 2 and the secondary treatment facility 8.

  Finally, the secondary processing facility 8 will be described. The digested liquid from the bioreactor 4 is once stored in the digested liquid tank 81 and then dehydrated by the dehydrator 82. The obtained dehydrated cake is subjected to any appropriate treatment (for example, fermentation treatment) as necessary, and finally composted. The dehydrated desorbed liquid is sent to the wastewater treatment facility 83 and purified. In the wastewater treatment facility 83, typically, activated sludge coal treatment using aerobic microorganisms is performed. The purified water is used as dilution water when preparing the slurry (raw water), and the excess purified water is discharged.

  As described above, electric power and compost material can be generated from organic waste with little use of external electric power and power.

  The bioreactor and energy recovery system of the present invention can be used very suitably for the treatment of organic waste (for example, human waste, septic tank sludge, raw garbage). Ultimately, it may form part of a highly preferred biological resource circulation system.

It is a flowchart explaining the collection system of the organic waste by preferable embodiment of this invention. It is a principal part schematic sectional drawing explaining the bioreactor by preferable embodiment of this invention. FIG. 3 is a schematic plan view of the bioreactor of FIG. 2. It is a schematic diagram explaining the methane refinement | purification equipment used for this invention. It is a schematic diagram explaining another methane refinement | purification equipment used for this invention. It is a schematic cross section explaining the conventional methane fermentation tank.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Receiving tank 2 Crusher 3 Raw water tank 4 Bioreactor 5 Methane refining equipment 6 Gas holder 7 Power generation means 8 Secondary treatment facility 41 Fermenter 42 Heating means 43 Stirring means

Claims (8)

A fermenter that creates a closed space to create an anaerobic state, methane ferment raw water containing organic waste, and generate biogas;
It has a main heating part extending in the vertical direction and a connecting part arranged so as to alternately connect the upper end parts and the lower end parts of the main heating part, and is arranged in the fermenter to heat the raw water Heating means to
A bioreactor comprising: a cylindrical shape defining a hollow portion; and stirring means disposed so as to pass the main heating portion of the heating means through the hollow portion. The heating means is hot water prepared by a solar heater, hot water prepared by a hot water boiler using the biogas as a heat source, or hot water prepared by surplus heat of a power generation means that generates electric power using the biogas. The bioreactor according to claim 1, wherein the bioreactor is a hot water pipe. The bioreactor according to claim 2, wherein an inner diameter of the stirring means is 350 to 800% of an inner diameter of the hot water pipe. The bioreactor according to any one of claims 1 to 3, wherein the stirring means is disposed at least in the vicinity of a peripheral portion of the fermenter. The bioreactor according to any one of claims 1 to 4, wherein the stirring unit stirs the raw water without consuming electric power and power by using the biogas and the convection of the raw water as a driving source. A slurrying means for slurrying organic waste;
The bioreactor according to any one of claims 1 to 5, wherein the slurry is subjected to methane fermentation and digested into biogas and digestive fluid.
Power generation means for generating electric power and heat by the biogas;
A secondary treatment facility for purifying residual organic matter contained in the digestive juice and precipitating excess sludge as compost material;
The bioreactor is heated to an appropriate temperature by heat from the power generation means, and the slurrying means and the secondary treatment facility are driven by a part of the power from the power generation means to generate power and compost material. To
Organic waste energy recovery system. The energy recovery system according to claim 6, wherein the power generation means is a fuel cell. The energy recovery system according to claim 6 or 7, further comprising a methane purification facility between the bioreactor and the power generation means.

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