JP2006218429A - Solid organic waste treatment method and its apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste treatment system which can efficiently treat solid organic waste. <P>SOLUTION: The solid organic waste is subjected to methane fermentation in a methane fermentation tank 5 to obtain a methane fermentation liquid. At least a part of the fermentation liquid is transferred to an ammonia stripping device 6 to stay for 40 minutes or more, and is heated to a temperature of 70 to 90°C to strip ammonia, thereby a liquid from which ammonia has been removed is obtained. The liquid from which ammonia has been removed is returned to a mixing tank 3 installed upstream of the methane fermentation tank 5 through a return line 11. The temperature of solid organic waste after the return of the above liquid becomes suitable for solubilization treatment in an acid fermentation tank 4 and methane fermentation treatment in the methane fermentation tank 5 respectively. Thereby the solid organic waste can be efficiently solubilized in the acid fermentation tank 4, and solid matter in the solid organic waste can be decomposed again. The decomposition efficiency of the solid organic waste can be improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid organic waste processing method and apparatus for processing solid organic waste.

  In recent years, as a method for treating this type of solid organic waste, a method using methane fermentation has attracted attention because energy can be recovered by methane gas generated in the process of methane fermentation of this solid organic waste. ing. When this solid organic waste is subjected to methane fermentation, it is equipped with a methane fermentation tank for methane fermentation. In the preceding stage of this methane fermentation tank, input amount adjustment, input concentration adjustment, or various solid organic wastes are provided. The structure which installs the input adjustment tank which has a capacity | capacitance for about 3 days for the purpose of mixing a thing is known (for example, refer nonpatent literature 1).

  In addition, solid organic waste treatment methods using this type of methane fermentation include a facility for methane fermentation of surplus sludge and garbage generated from human waste treatment facilities. A configuration is also known in which an excess of sludge is directly charged into a methane fermentation tank while being temporarily stored in an installed mixing tank (see, for example, Non-Patent Document 2). Furthermore, as a method for treating solid organic waste using this type of methane fermentation, an acid fermentation tank to be solubilized to increase the treatment efficiency is installed in the front stage of the methane fermentation tank, or this acid fermentation The structure etc. which circulate the fermented liquor fermented in the tank are known (for example, refer nonpatent literature 3).

  In general, raw garbage and the like have a high decomposition rate in methane fermentation, while manure and surplus sludge generated from water treatment facilities have a low decomposition rate. Therefore, surplus sludge generated from water treatment facilities such as manure is solubilized biologically using a treatment time of about several minutes as a guideline at a high temperature of about 70 ° C. to 90 ° C. before methane fermentation. In addition to making the organic sludge such as manure and surplus sludge alkaline, and solubilizing by maintaining the temperature of the organic sludge at 50 to 100 ° C. A configuration (for example, see Patent Document 2) is known.

  When surplus sludge such as manure is subjected to methane fermentation, the optimum temperature of the surplus sludge is about 50 ° C to 60 ° C in the case of high temperature methane fermentation, and 35 ° C to 40 ° C in the case of medium temperature methane fermentation. Degree. Furthermore, when solid organic waste such as manure and surplus sludge is subjected to methane fermentation, ammonia is contained in the methane fermentation liquid after methane fermentation due to decomposition of proteins contained in the solid organic waste. Is generated. And when this ammonia flows into a water area, it becomes one of the causative substances of eutrophication, so it needs to be removed by some treatment.

  And as this removal method of ammonia, the structure which converts ammonia into nitrogen gas by the nitrification denitrification reaction by microorganisms, the structure which transfers ammonia contained in methane fermentation liquid to a gaseous phase part, etc. are known ( For example, see Patent Document 3.) Furthermore, when this ammonia is in a high concentration, it inhibits methane fermentation. Therefore, the ammonia contained in this methane fermentation solution is transferred to the gas phase part in the circulation line of the methane fermentation solution, and this high concentration of ammonia is transferred. The structure etc. which avoid inhibition of the methane fermentation by A is known (for example, refer patent document 4).

As a method for removing ammonia in the methane fermentation broth, the ammonia in the methane fermentation broth is based on the reaction formula: NH ₄ ⁺ + OH ⁻ → NH ₃ + H ₂ O. Thus, ammonium ions (NH4 ⁺ ) in the methane fermentation liquid are diffused as ammonia gas. Furthermore, when the temperature of the methane fermentation broth is increased, the solubility of free ammonia (NH ₃ ) in the methane fermentation broth decreases, so ammonia gas is diffused and the ammonia in the methane fermentation broth is removed. Ammonia stripping treatment to be removed to the phase part is known. In this ammonia stripping treatment, the gas-liquid ratio, which is the ratio of the amount of gas blown to the amount of methane fermentation liquid to be treated, is an important factor that affects the ammonia removal rate. Usually, the value is several thousand times (for example, see Patent Document 5).

Furthermore, as a method for treating the gas containing ammonia generated by the ammonia stripping treatment, a method of decomposing it into nitrogen gas and water using a catalyst (see, for example, Patent Document 6), a direct combustion method, A method of decomposing nitrogen gas and water in combination with a denitration catalyst (for example, see Non-Patent Document 4) is known.
JP-A-10-235317 (page 1-5) Japanese Patent No. 2659895 (pages 1-8) JP-A-11-77024 (Page 1-5) JP 2001-137812 A (page 1-12, FIG. 1) Japanese Patent Laying-Open No. 2004-230338 (page 1-4) JP 2001-9281 A (page 1-9) “Planning and Design Procedure for Sludge Recycling Center and Other Facilities”, National Urban Cleaning Conference, September 25, 2001, p. 273 “Research Report on Promotion of Infrastructure Improvement of Sludge Recycling Centers (2001)”, Waste Research Foundation, August 2002, p. 65 Osamu Mizuno, 3 others, “High-speed food waste treatment using a two-phase methane fermentation system”, Lectures, 37th Annual Meeting of Japan Society on Water Environment, March 6, 2003, p. 409 Technical data Small denitration equipment, [online], Nippon Shokubai Co., Ltd. [Search on January 28, 2005], Internet <URL: http://www.shokubai.co.jp/main/04produc/syohin/kogata. htm>

  As described above, when surplus sludge generated from water treatment facilities such as manure is biologically solubilized by high temperature before methane fermentation and subjected to high-temperature reforming treatment, the surplus sludge before methane fermentation is treated. The temperature of 70 ° C. to 90 ° C. is suitable, and the heating temperature before this methane fermentation is the processing time of this heating when the temperature of the excess sludge before this methane fermentation is about 90 ° C. The standard is about a few minutes.

  However, as described above, the optimum temperature of excess sludge during methane fermentation is about 50 ° C to 60 ° C in the case of high temperature methane fermentation, and about 35 ° C to 40 ° C in the case of medium temperature methane fermentation. Therefore, when the high-temperature reforming treatment is performed before the methane fermentation, it is necessary to cool the excess sludge by allowing it to cool or by providing a heat exchanger to cool it by heat exchange. There is a problem that methane fermentation is not easy.

  This invention is made | formed in view of such a point, and it aims at providing the processing method and apparatus of a solid organic waste which can perform methane fermentation of a solid organic waste efficiently.

  The processing method of the solid organic waste according to claim 1 is a methane fermentation process in which the solid organic waste is subjected to a methane fermentation process to obtain a methane fermentation liquid, and at least a methane fermentation liquid processed in the methane fermentation process. A heating process in which a part is retained for 40 minutes or more and heated to a temperature of 70 ° C. or higher and 90 ° C. or lower, and a return process in which the methane fermentation liquid heated in this heating process is returned to the methane fermentation process. Are provided.

  Then, after solid organic waste is subjected to methane fermentation treatment in the methane fermentation step to obtain a methane fermentation solution, at least a part of the methane fermentation solution is retained for 40 minutes or more in the heating step to be 70 ° C to 90 ° C. After heating to the following temperature, the methane fermentation liquid heated in this heating step is returned to the methane fermentation step in the return step. As a result, by returning the methane fermentation liquid heated in the heating process to the solid organic waste in the return process, the temperature of the solid organic waste becomes a temperature suitable for methane fermentation. Furthermore, the methane fermentation liquid obtained by methane fermentation of the solid organic waste is retained for 40 minutes or more and heated, so that the methane fermentation liquid can be efficiently solubilized, and the solid content in the methane fermentation liquid is reduced. Since it is re-decomposed, the decomposition efficiency of this methane fermentation liquid improves. Therefore, the solid organic waste can be efficiently methane-fermented, and the methane fermentation liquid obtained by methane fermentation of the solid organic waste can be efficiently decomposed, so that the solid organic waste can be efficiently processed.

The solid organic waste treatment method according to claim 2 is the solid organic waste treatment method according to claim 1, wherein the heating step is performed on the heated methane fermentation broth to 1000 kg of the methane fermentation broth. by blowing 200 Nm ³ or more 400 Nm ³ or less air for those wherein ammonia stripping step for removing ammonia in the methane fermentation liquid.

Then, the methane fermentation liquid is warmed is blown with 200 Nm ³ or more 400 Nm ³ or less in air to the methane fermentation liquor 1000 kg, to remove ammonia the methane fermentation liquor with ammonia stripping step. As a result, the ammonia in the methane fermentation broth can be removed as ammonia gas, the anaerobic bacteria in the methane fermentation broth can be sterilized, and the sterilized anaerobic bacteria can be returned in the return process to return the sterilization. The anaerobic bacteria produced are re-degraded and processed. Therefore, the decomposition efficiency of each of the solid organic waste and the methane fermentation liquid can be improved, and the treatment efficiency in the ammonia stripping process can be improved.

  The method for treating solid organic waste according to claim 3 is the method for treating solid organic waste according to claim 2, wherein sodium hydroxide is added to the methane fermentation liquid from which ammonia has been removed in the ammonia stripping step. The solubilizing step for solubilizing the methane fermentation liquor solubilized in the solubilizing step is returned to and mixed with the solid organic waste.

  And when removing ammonia from a methane fermentation liquid at an ammonia stripping process, since carbonate ion is removed from this methane fermentation liquid, the alkalinity of this methane fermentation liquid will reduce. Therefore, after adding sodium hydroxide to the methane fermentation liquid from which ammonia has been removed in the ammonia stripping process and solubilizing it in the solubilization process, this solubilized methane fermentation liquid is returned to the solid organic waste in the return process. Return to the object and mix. As a result, the alkalinity of the methane fermentation liquid can be increased by adding a small amount of sodium hydroxide, and the heating process and the alkali treatment by adding sodium hydroxide are used in combination. Therefore, the decomposition efficiency of the methane fermentation broth can be improved efficiently, and the amount of sludge produced from the methane fermentation broth can be reduced.

  The solid organic waste treatment method according to claim 4 is the gas containing ammonia separated from the methane fermentation liquid in the ammonia stripping step in the solid organic waste treatment method according to claim 2 or 3. Is mixed with methane gas generated in the methane fermentation process and burned.

  And it separated from the methane fermentation liquid by mixing the gas containing ammonia separated from the methane fermentation liquid in the ammonia stripping process with the methane gas generated in the methane fermentation process and burning it in the gas combustion process. Since the methane fermentation liquor can be heated using the combustion heat of methane gas generated in the methane fermentation process together with the combustion heat of ammonia, the energy used in the ammonia stripping process can be used effectively.

  The solid organic waste treatment method according to claim 5 is the solid organic waste treatment method according to any one of claims 1 to 4, wherein the methane fermentation liquid heated in the heating step is solid organic waste. The solid organic waste is mixed at a ratio of 0.5 to 2.0 times by mass with respect to the organic waste.

  And when the methane fermentation liquid heated in the heating step is mixed with the solid organic waste having a mass of less than 0.5 times the solid organic waste in the ammonia stripping step. The ammonia stripping process cannot be performed efficiently. Moreover, when this methane fermentation liquid is mixed with the solid organic waste more than 2.0 times by mass with respect to the solid organic waste, the methane fermentation with respect to the processing amount of the solid organic waste Since the amount of liquid treatment increases, the energy used in the ammonia stripping process is wasted. Therefore, the methane fermentation liquid heated in the heating step is solid organic waste at a ratio of 0.5 to 2.0 times by mass with respect to the solid organic waste in the ammonia stripping step. In addition, the ammonia stripping process can be efficiently performed, and the energy used in the ammonia stripping process can be used efficiently, and the total solid concentration after mixing the solid organic mixture and the methane fermentation liquid can be reduced. Since it becomes a proper value, the processing efficiency of each of these solid organic mixture and methane fermentation liquid can be improved.

  The apparatus for treating solid organic waste according to claim 6 is a methane fermentation means for producing a methane fermentation liquid by subjecting the solid organic waste to a methane fermentation treatment, and at least a methane fermentation liquid treated by the methane fermentation means. A heating means that retains a part for 40 minutes or more and heats it to a temperature of 70 ° C. or higher and 90 ° C. or lower, and a return means that returns the methane fermentation liquid heated by the heating means to the methane fermentation step. Are provided.

  Then, after solid organic waste is subjected to methane fermentation treatment with methane fermentation means to obtain a methane fermentation liquid, at least a part of the methane fermentation liquid is retained for 40 minutes or more by heating means to be 70 ° C. or higher and 90 ° C. or lower. After warming to temperature, the methane fermentation liquid heated by this heating means is returned to the methane fermentation process by the return means. As a result, by returning the methane fermentation liquid heated by the heating means to the solid organic waste by the return means, the temperature of the solid organic waste becomes a temperature suitable for methane fermentation. Furthermore, the methane fermentation liquid obtained by methane fermentation of the solid organic waste is retained for 40 minutes or more and heated, so that the methane fermentation liquid can be efficiently solubilized, and the solid content in the methane fermentation liquid is reduced. Since it is re-decomposed, the decomposition efficiency of this methane fermentation liquid improves. Therefore, the solid organic waste can be efficiently methane-fermented, and the methane fermentation liquid obtained by methane fermentation of the solid organic waste can be efficiently decomposed, so that the solid organic waste can be efficiently processed.

  According to the method for treating solid organic waste according to claim 1, after the solid organic waste is subjected to methane fermentation treatment in the methane fermentation step to obtain a methane fermentation solution, at least a part of the methane fermentation solution is added. By retaining for 40 minutes or more in the temperature step and heating to a temperature not lower than 70 ° C. and not higher than 90 ° C., the methane fermentation liquid heated in this heating step is returned to the methane fermentation step in the return step. The temperature of the solid organic waste after the methane fermentation liquor is returned can be adjusted to a temperature suitable for methane fermentation. Furthermore, the methane fermentation liquid obtained by methane fermentation of the solid organic waste is retained for 40 minutes or more and heated, so that the methane fermentation liquid can be efficiently solubilized and the solid content in the methane fermentation liquid can be reduced. Since it can be re-decomposed, the decomposition efficiency of this methane fermentation liquid can be improved, so this solid organic waste can be efficiently methane fermented, and the methane fermentation liquid obtained by methane fermentation of this solid organic waste can be efficiently decomposed Therefore, this solid organic waste can be treated efficiently.

According to the method for treating solid organic waste according to claim 2, 200 Mm ³ or more and 400 Nm ³ or less of air is blown into the heated methane fermentation broth with respect to 1000 kg of the methane fermentation broth. By removing ammonia in the ammonia stripping process, ammonia in this methane fermentation broth can be removed as ammonia gas, anaerobic bacteria in this methane fermentation broth can be sterilized, and the sterilized anaerobic bacteria Since the sterilized anaerobic bacteria can be re-degraded and processed in the return process, the decomposition efficiency of each of the solid organic waste and the methane fermentation liquid can be improved, and the ammonia stripping process Processing efficiency can be improved.

  According to the method for treating solid organic waste according to claim 3, after adding sodium hydroxide to the methane fermentation liquid from which ammonia has been removed in the ammonia stripping step and solubilizing in the solubilization step, By returning the solubilized methane fermentation broth to solid organic waste in the return step and mixing it, the alkalinity of the methane fermentation broth can be increased by adding a small amount of sodium hydroxide, and the heating step and water Since it can use together with the alkali treatment by addition of sodium oxide, the decomposition efficiency of this methane fermentation broth can be improved efficiently and the amount of sludge produced from this methane fermentation broth can be reduced.

  According to the method for treating solid organic waste according to claim 4, the gas containing ammonia separated from the methane fermentation liquid in the ammonia stripping process is mixed with the methane gas generated in the methane fermentation process to perform gas combustion. Used in the ammonia stripping process because the methane fermentation liquid can be heated using the combustion heat of methane gas generated in the methane fermentation process together with the combustion heat of ammonia separated from the methane fermentation liquid by burning in the process. Energy can be used effectively.

  According to the processing method of the solid organic waste of Claim 5, the methane fermentation liquid heated at the heating process is 0.5 times or more and 2.0 times in mass with respect to solid organic waste. By mixing at the following ratio, the ammonia stripping process can be efficiently performed, and the energy used in this ammonia stripping process can be used efficiently, and the total solids after mixing these solid organic mixture and methane fermentation liquid Since an object concentration can be made into an appropriate value, the processing efficiency of each of these solid organic mixture and methane fermentation liquid can be improved.

  According to the processing apparatus for solid organic waste according to claim 6, after the solid organic waste is subjected to methane fermentation treatment by methane fermentation means to obtain a methane fermentation liquid, at least a part of the methane fermentation liquid is heated. The methane fermentation liquid is retained by the means for 40 minutes or more and heated to a temperature of 70 ° C. or higher and 90 ° C. or lower, and then the methane fermentation liquid heated by the heating means is returned to the methane fermentation process by the return means. The temperature of the solid organic waste after being returned can be adjusted to a temperature suitable for methane fermentation. Furthermore, the methane fermentation liquid obtained by methane fermentation of the solid organic waste is retained for 40 minutes or more and heated, so that the methane fermentation liquid can be efficiently solubilized and the solid content in the methane fermentation liquid can be reduced. Since it can be re-decomposed, the decomposition efficiency of this methane fermentation liquid can be improved, so this solid organic waste can be efficiently methane fermented, and the methane fermentation liquid obtained by methane fermentation of this solid organic waste can be efficiently decomposed Therefore, this solid organic waste can be treated efficiently.

  Hereinafter, the configuration of the first embodiment of the solid organic waste treatment apparatus of the present invention will be described with reference to FIG.

  In FIG. 1, reference numeral 1 denotes a waste treatment system as a solid organic waste treatment apparatus. This waste treatment system 1 is also a solid organic waste treatment system as a waste treatment apparatus. And as solid organic waste processed with this waste processing system 1, it is all the wastes which can be methane-fermented. Specifically, examples of the solid organic waste include garbage, waste, agricultural and fishery waste, food processing waste, sewage, and excess sludge generated in a wastewater treatment facility (not shown).

  And the waste treatment system 1 is provided with the pre-processing means 2 which crushes solid organic waste and removes the foreign material in this solid organic waste. This pretreatment means 2 has, for example, crushing shafts (not shown) having two axes, three axes, or four axes with a tooth width of about 20 mm ± 5 mm. That is, the pretreatment means 2 is a pretreatment step, and crushes solid organic waste such as garbage collected by a collection vehicle (not shown) and is included in the solid organic waste. Remove impurities such as plastics that are not suitable for methane fermentation.

  Furthermore, a mixing tank 3 for treating the solid organic waste pretreated by the pretreatment means 2 is connected to and attached to the pretreatment means 2. The mixing tank 3 is used as an ammonia stripping treatment liquid in which the solid organic waste subjected to the pretreatment step by the pretreatment means 2 is transferred and ammonia removal treatment is performed by an ammonia stripping device 6 described later. The ammonia removal liquid which is the ammonia stripping treatment sludge is transferred. That is, the mixing tank 3 mixes the solid organic waste pretreated by the pretreatment means 2 and the ammonia removal liquid subjected to the ammonia removal treatment by the ammonia stripping device 6 to obtain a predetermined total solid. The concentration is adjusted to a slurry-like liquid organic waste having a total solids (TS concentration) of, for example, about 10 to 15%, more preferably 10% to 13%.

  Further, an acid fermentation tank 4 for treating the liquid organic waste adjusted in the mixing tank 3 is attached to the mixing tank 3. The acid fermenter 4 is a solubilization means for transferring the liquid organic waste adjusted in the mixing tank 3 and solubilizing the liquid organic waste by high-temperature reforming treatment. Specifically, the acid fermenter 4 includes a heat retaining means (not shown) that retains the liquid temperature of the liquid organic waste transferred to and stored in the acid fermenter 4 at a high temperature of, for example, 55 ° C. or more and 60 ° C. or less. Further, a stirring means (not shown) for stirring the liquid organic waste stored in the acid fermentation tank 4 is provided. The acid fermenter 4 retains the liquid organic waste for 1 day or more, more preferably 3 days or more, solubilizes the liquid organic waste to obtain a solubilized liquid.

  Here, in the solid organic waste before the liquid organic waste transferred to the acid fermenter 4, for example, a trace amount necessary for microorganisms such as iron (Fe), nickel (Ni) or cobalt (Co) When the nutrient salt which is an element is insufficient, it is desirable to add these nutrient salts to the acid fermenter 4 by an adding means (not shown).

  Furthermore, a methane fermentation tank 5 as a methane fermentation means for methane fermentation treatment of the solubilized solution solubilized in the acid fermentation tank 4 is attached to the acid fermentation tank 4. The methane fermentation tank 5 is a methane fermentation process in which the solubilized liquid that is solubilized in the acid fermentation tank 4 and stored in the acid fermentation tank 4 is transferred. And this methane fermentation tank 5 is equipped with the temperature adjustment means which is not shown in figure which maintains the liquid temperature of the solubilization liquid transferred to this methane fermentation tank 5 at the temperature suitable for methane fermentation. This temperature adjusting means maintains the liquid temperature of the solubilized liquid at 35 ° C. ± 5 ° C. when the solubilized liquid is subjected to medium temperature methane fermentation in the methane fermenter 5, solubilized in the methane fermenter 5. When the liquid is subjected to high temperature methane fermentation, the liquid temperature of the solubilized liquid is maintained at 55 ° C. ± 5 ° C.

In addition, the methane fermentation tank 5 includes a stirring means (not shown) that stirs the solubilized liquid stored in the methane fermentation tank 5. And in this methane fermentation tank 5, it stirs adjusting the temperature of the solubilization liquid stored in this methane fermentation tank 5, this lysate is fermented by methane fermentation, and fermentation as a methane fermentation processing liquid Use liquid. Furthermore, in this methane fermenter 5, by using the methane fermentation treatment of the solubilized liquid in the methane fermenter 5, the methane fermenter 5 is biochemical mainly composed of methane (CH ₄ ) and carbon dioxide (CO ₂ ). Gas is generated. This biogas is stored in a biogas holder (not shown).

  Further, the methane fermentation tank 5 is provided with an ammonia stripping device 6 which is a heating means as a nitrogen removing device for ammonia stripping the fermentation broth treated in the methane fermentation tank 5. Here, the ammonia stripping device 6 is an ammonia removing device as a nitrogen compound removing device. Further, the methane fermentation tank 5 is provided with a fermentation solution processing means 7 for processing the fermentation solution processed in the methane fermentation tank 5. A part of the fermentation broth treated in the methane fermentation tank 5 is transferred to the ammonia stripping apparatus 6 and the ammonia stripping apparatus 6 and the ammonia stripping apparatus 6. The remaining fermentation liquor that is not transferred to is transferred to the fermentation broth processing means 7.

  Here, the transfer amount of the fermented liquid to this ammonia stripping apparatus 6 is determined by the property of the solid organic waste made into object. Specifically, when the solid organic waste is food waste such as garbage, the solid organic matter to be treated is used from the viewpoint of ensuring fluidity in a reaction tank (not shown) of the ammonia stripping device 6. It is preferable that approximately the same amount of fermentation broth as the waste is transferred to the ammonia stripping device 6.

  On the other hand, the biogas generated in the methane fermentation process in the methane fermentation tank 5 and stored in the biogas holder is used by the gas utilization means 8 as a combustion apparatus after undergoing processes such as desulfurization and siloxane removal as necessary. The Here, the removal of siloxane is removal of siloxane, which is a harmful component contained in biogas. Furthermore, as this gas utilization means 8, equipment used in a normal methane fermentation facility, such as a power generation device such as a gas engine or a gas turbine, or a boiler is used.

The gas utilization means 8 is connected to a methane fermentation tank 5 and an ammonia stripping device 6. Specifically, this gas utilization means 8 is used as a gas combustion stroke in which a gas containing ammonia gas generated in the ammonia stripping device 6 is burned together with biogas generated in the methane fermentation tank 5. Furthermore, when methane gas is burned by this gas utilization means, methane gas is burned by the reaction formula: CH ₄ + 2O ₂ → CO ₂ + H ₂ O.

Further, in the ammonia stripping device 6, when the ammonia stripping process is performed using air in the ammonia stripping device 6, the nitrogen (N ₂ ) is almost 79% from the ammonia stripping device 6, A gas having a composition of 19% oxygen (O ₂ ), 1% ammonia (NH ₃ ), and 1% carbon dioxide (CO ₂ ) is discharged. On the other hand, the concentration of methane gas contained in the biogas generated from the methane fermentation tank 5 is 50% or more and 60% or less. In order to completely burn methane in the biogas generated from the methane fermenter 5, a gas discharged from the ammonia stripping device 6 in an amount of 5 to 6 times the biogas: 1 Nm ³ is required. It becomes.

Here, since the amount of biogas generated from solid organic waste, that is, 1000 kg (1 ton) of methane fermentation liquid as methane fermentation treatment liquid is 60 Nm ³ or more and 180 Nm ³ or less, in order to burn this biogas Requires about 300 Nm ³ or more and 900 Nm ³ or less of gas discharged from the ammonia stripping device 6. Further, the gas-liquid ratio of the ammonia stripper 6 is 200 to 400, the amount of gas generated with the methane fermentation liquid 1 ton treatment is 200 Nm ³ or more 400 Nm ³ or less.

  For this reason, in the quantity of the gas discharged | emitted by the ammonia stripping process in this ammonia stripping apparatus 6, oxygen will run short in order to burn the biogas generated from the methane fermentation tank 5 completely. Therefore, the biogas is completely combusted by the gas utilization means 8 by mixing the air having oxygen that is insufficient for the combustion with the biogas. At this time, if the biogas and the gas discharged from the ammonia stripping device 6 are mixed in advance, the methane concentration after mixing may be 5% to 14%, which is the explosion limit. It is better not to mix gas and gas in advance. Therefore, the gas discharged from the ammonia stripping device 6 is mixed with air and then supplied to the gas utilization means 8, and this gas is not mixed with biogas in advance. Since the explosion limit of ammonia gas is 15% or more and 28% or less, there is no problem even if the gas discharged from the ammonia stripping device 6 is mixed with air in advance.

  Furthermore, the gas utilization means 8 is connected to a catalytic reduction device 9 into which exhaust gas that is a gas burned by the gas utilization means 8 is introduced. This catalytic reduction device 9 processes nitrogen oxides generated by gas combustion in the gas utilization means 8, and exhaust gas discharged from the gas utilization means 8 is introduced. A part of the gas containing ammonia gas generated in the ammonia stripping device 6 is introduced into the catalytic reduction device 9. This catalytic reduction device 9 is necessary after decomposing ammonia as nitrogen oxides contained in the exhaust gas discharged from the gas utilization means 8 into harmless nitrogen, that is, carbon dioxide gas and water, using a catalyst. Release to atmosphere after treatment. That is, this catalytic reduction apparatus uses the catalytic denitration method using ammonia obtained by the ammonia stripping process in the ammonia stripping apparatus 6 to decompose and render harmless the exhaust gas exhausted from the gas utilization means.

  Here, in order to warm the fermented liquor transferred to the ammonia stripping device 6, an indirect heating method via a heat exchanger (not shown) with the gas after combustion in the gas utilization means 8, or this gas utilization means For example, it is possible to use at least a part of the water vapor generated in the ammonia stripping device 6. And in this ammonia stripping apparatus 6, while fermenting the fermented liquid transferred to this ammonia stripping apparatus 6 for 40 minutes or more in a reaction tank, this fermented liquid is heated to the temperature of 70 degreeC or more and 90 degrees C or less. Then, the nitrogen compound in the fermentation liquid is removed and ammonia stripping is performed to obtain an ammonia removing liquid as an ammonia stripping treatment liquid.

  Further, the ammonia stripping device 6 is connected to the mixing tank 3 via a return line 11 as a return means. Then, the ammonia stripping liquid heated by the ammonia stripping by the ammonia stripping device 6 is returned to the mixing tank 3 in the preceding stage from the methane fermentation tank 5 through the return line 11 as a return process. At this time, the ammonia removal liquid heated by the ammonia stripping device 6 is in a ratio of 0.5 to 2.0 times by mass with respect to the solid organic waste transferred to the mixing tank 3. Then, it is returned to the mixing tank 3 and mixed with the solid organic waste in the mixing tank 3.

  Next, the operation of the first embodiment will be described.

  First, when solid organic waste such as excess sludge generated from a water treatment facility is subjected to high-temperature reforming treatment in the previous stage of the methane fermentation tank 5, the temperature of the solid-liquid organic waste is set to 70 ° C. or higher and 90 ° C. In addition, when the temperature of the solid organic waste is 90 ° C., the processing time when the solid organic waste is subjected to the high-temperature reforming treatment is set to about several minutes.

  On the other hand, the optimum temperature of the solid organic waste when the solid organic waste is subjected to methane fermentation in the methane fermentation tank 5 is 50 ° C. when the solid organic waste is subjected to high temperature methane fermentation. When the solid organic waste is subjected to a medium temperature methane fermentation treatment, the temperature is about 35 ° C. or more and 40 ° C. or less. Therefore, when the solid organic waste is subjected to high-temperature reforming treatment in the previous stage of the methane fermentation treatment in the methane fermentation tank 5, the solid organic waste is allowed to cool before being subjected to the methane fermentation treatment, It is necessary to cool by installing a heat exchanger that does not.

  On the other hand, when the methane fermentation liquid obtained by subjecting this solid organic waste to methane fermentation treatment in the methane fermentation tank 5 is returned to the previous stage of the methane fermentation tank 5, methane fermented in the methane fermentation tank 5 is used. When the fermentation broth is heated to a temperature of 70 ° C. or higher and 90 ° C. or lower and subjected to high temperature reforming treatment, the temperature of the solid organic waste is generally about 5 ° C. or higher and 25 ° C. or lower. When the fermentation liquid and the solid organic waste are mixed at a mass ratio of about 1: 1, the temperature of the mixed liquid after the methane fermentation liquid and the solid organic waste are mixed is set to the acid in the subsequent stage. While being suitable for the solubilization process in the fermenter 4, it will be about 35 degreeC or more and 60 degrees C or less suitable for the methane fermentation process in a methane fermenter.

  Furthermore, unlike activated sludge, the microbial flora of the methane fermentation liquid after methane fermentation in the methane fermentation tank 5 is mainly archaebacteria. The archaebacteria generally have many heat-resistant bacteria, and when the methane fermentation solution is targeted, it is not possible to expect an improvement in decomposition efficiency or gas generation amount at a processing time of about several minutes at 90 ° C. Moreover, even if this methane fermentation liquid is heated to 85 degreeC and it is set as the processing time for about 30 minutes, the gas generation amount from this methane fermentation liquid cannot be improved.

  In addition, the thermal reforming treatment for the methane fermentation broth requires a treatment time of about 40 minutes or more, more preferably about 60 minutes to 90 minutes. And in order to improve the gas generation amount from this methane fermentation liquid, this methane fermentation is carried out before the methane fermentation tank 5 which methane-fermented this methane fermentation liquid, without carrying out solid-liquid separation of this methane fermentation liquid. It is preferable to return the liquid. That is, by heat-treating this methane fermentation broth without solid-liquid separation, the solid content in this methane fermentation broth is re-decomposed, and the decomposition efficiency of this methane fermentation broth can be improved.

  Next, the methane fermentation liquid returned to the previous stage from the methane fermentation tank 5 can be heated to a temperature of 70 ° C. or higher and 90 ° C. or lower in the ammonia stripping device 6 before being returned to the mixing tank 3. . Therefore, it is also conceivable that the methane fermentation broth is transferred to the ammonia stripping device 6 and subjected to the ammonia stripping treatment and then returned to the mixing tank 3 through the return line 11. That is, when air is brought into contact with a methane fermentation liquid heated to a temperature of 70 ° C. or higher and 90 ° C. or lower, the solubility of gas generated in the ammonia stripping treatment of the methane fermentation liquid is reduced, and the ammonia in the air Due to the low gas partial pressure, etc., the ammonia in the methane fermentation broth can be transferred to the gas phase side as ammonia gas and removed.

  Furthermore, methanogenic bacteria in this methane fermentation broth are obligate anaerobic bacteria that cannot live in the presence of oxygen. Therefore, by using air when the methane fermentation broth is subjected to ammonia stripping by the ammonia stripping device 6, oxygen contained in the air is brought into contact with the methanogenic bacteria in the methane fermentation broth to generate the methane. Can sterilize bacteria. Further, since the sterilized methanogenic bacteria are returned from the ammonia stripping device 6 to the mixing tank 3 which is a previous process of the methane fermentation tank 5 and re-decomposed, the decomposition efficiency of the entire waste treatment system 1 is improved. It can be improved.

The methane fermentation broth contains ammonium ions (NH4 ⁺ ) and bicarbonate ions (HCO ₃ ⁻ ) at high concentrations. And although the ammonium ion concentration in this methane fermentation liquid changes with properties of solid organic waste, it is generally 1000 mg-N / L or more and 4000 mg-N / L or less in terms of nitrogen. Furthermore, factors relating to the removal rate of the ammonia stripping treatment of the methane fermentation broth by the ammonia stripping device 6 include a residence time of the methane fermentation broth and an aeration method.

And if the gas-liquid ratio of this methane fermentation liquid and air is raised, the ammonia stripping process efficiency in the ammonia stripping apparatus 6 will improve, but as a result, gas with low ammonia concentration will generate | occur | produce in large quantities. This gas treatment is not easy because it is not easy. Further, from the viewpoint of processing a gas containing ammonia generated in the ammonia stripping treatment with ammonia stripping apparatus 6, the amount of air blown against the methane fermentation liquid 1000kg be 200 Nm ³ or more 400 Nm ³ or less preferable.

  Next, the ammonia stripping process in the ammonia stripping device 6 has a high running cost for increasing the temperature of the methane fermentation broth transferred to the ammonia stripping device 6. And in order to collect | recover the energy used for the liquid temperature rise of this methane fermentation liquid, it is common to install the heat exchanger etc. which are not illustrated in the ammonia stripping apparatus 6, In this case, ammonia stripping The apparatus 6 becomes complicated and the initial cost becomes high.

  On the other hand, the ammonia stripping device 6 performs an ammonia stripping process on the methane fermentation liquid returned from the methane fermentation tank 5 to the preceding mixing tank 3 after ammonia stripping by the ammonia stripping apparatus 6. Therefore, the temperature of the solid organic waste after mixing the ammonia removal liquid after being ammonia stripped by the ammonia stripping device 6 becomes a temperature suitable for the fermentation treatment in the acid fermentation tank 4. . That is, the energy used in the ammonia stripping device 6 can be effectively used without using a heat exchanger or the like. For this reason, the number of heat exchangers of the entire waste treatment system 1 can be reduced.

  Furthermore, in the ammonia stripping process in the ammonia stripping apparatus 6, a gas containing ammonia gas is generated, and the treatment of the gas containing ammonia gas is not easy. As a method for treating the ammonia gas in the gas, the catalyst reducing device 9 uses the catalyst to decompose the ammonia gas into carbon dioxide gas and water. At this time, the operating temperature of the catalyst of the catalytic reduction device 9 is 300 ° C. or higher and 400 ° C. or lower. Furthermore, when the ammonia gas is decomposed into carbon dioxide gas and water by the catalytic reduction device 9 only with the heat at the time of self-combustion of ammonia, the concentration of the ammonia gas in the gas containing the ammonia gas is 4% or more. It is necessary to be.

  On the other hand, when the nitrogen concentration of the methane fermentation broth is 1000 mg / L or more and 4000 mg / L or less, and the gas-liquid ratio between the methane fermentation broth and air is 200 or more and 400 or less, the ammonia stripping device 6 performs ammonia stripping treatment. Therefore, the ammonia gas concentration in the gas generated by this ammonia stripping treatment becomes 4% or less, and therefore this gas cannot be treated only with the heat of self-combustion of ammonia.

Therefore, the gas generated by the ammonia stripping process in the ammonia stripping apparatus 6 is generated in the methane fermentation tank 5 by the gas utilization means 8 together with the biogas mainly composed of methane and carbon dioxide. It was set as the structure which carries out a combustion process. Here, the amount of biogas generated from the methane fermentation tank 5 due to the treatment of the solid organic waste depends on the properties of the target solid organic waste, but is about 60 Nm ³ or more per ton of the treatment amount. It is about 180 Nm ³ or less. Furthermore, if the gas-liquid ratio of the methane fermentation liquor and air is lowered and this methane fermentation liquor is subjected to ammonia stripping treatment by the ammonia stripping device 6, the ammonia gas in the gas generated by this ammonia stripping treatment Although the concentration can be increased to 4% or more, the nitrogen removal rate from the methane fermentation liquid is reduced.

  Further, since the gas utilization means 8 combusts the biogas and the ammonia gas generated in the ammonia stripping process in the ammonia stripping device 6, nitrogen oxides derived from the combustion of this ammonia are generated. Then, the nitrogen oxide is decomposed into carbon dioxide gas and water by the catalytic reduction device 9 generated by the ammonia stripping process in the ammonia stripping device 6.

  At this time, since the temperature of the carbon dioxide discharged from the catalytic reduction device 9 is about 350 ° C. or more and 400 ° C. or less, the carbon dioxide is not released into the atmosphere as it is, but from the viewpoint of effective use of heat. Then, heat is recovered from the carbon dioxide gas by a heat exchanger (not shown), and the temperature of the methane fermentation liquid, the solubilizing liquid, or the like is heated with the recovered heat.

  Further, the carbon dioxide gas discharged from the catalytic reduction device 9 and the exhaust gas discharged from the gas utilization means 8 each contain several percent or more oxygen gas. The methanogenic bacteria responsible for methane production when the solubilized liquid is methane-fermented in the methane fermenter 5 are obligately anaerobic bacteria, that is, bacteria that are difficult to survive in the presence of free oxygen. For this reason, when processing solid organic waste alone with the methane fermentation tank 5, it is not possible to effectively use the exhaust gas discharged from the gas utilization means 8 or the carbon dioxide gas discharged from the catalytic reduction device 9. Since it is not easy, it was necessary to recover energy from these exhaust gas or carbon dioxide gas through a heat exchanger.

  On the other hand, the acid fermentation process in the acid fermenter 4 is also possible with facultative anaerobic bacteria. On the other hand, the high temperature reforming step for reforming the solid organic waste at a high temperature is a step of physicochemically treating the solid organic waste, and is not affected by free oxygen. Therefore, the gas discharged from the gas utilization means 8 and the catalytic reduction device 9 is directly introduced into the acid fermentation tank 4 other than the methane fermentation tank 5, the mixing tank 3 or between them through a pipe (not shown). The liquid organic waste in the acid fermentation tank 4 and the solid organic waste in the mixing tank 3 can be heated.

  Since the gas utilization means 8 combusts ammonia together with the biogas, the combustion heat of ammonia can be used in addition to the combustion heat of the biogas. Compared to the case where only the biogas is combusted by this gas utilization means. Therefore, it is possible to construct a rational waste treatment system 1 that can effectively use energy based on the combustion heat of ammonia that has not been conventionally used.

  Furthermore, in the first embodiment, the nitrogen oxides in the exhaust gas discharged from the gas utilization means 8 are decomposed into carbon dioxide and water by the catalytic reduction device 9, but are discharged from the gas utilization means 8. The liquid organic waste in the acid fermentation tank 4 and the solid organic waste in the mixing tank 3 can be heated by directly using the exhaust gas. Specifically, when the exhaust gas discharged from the gas utilization means 8 is directly used, nitrogen oxides contained in the exhaust gas are dissolved in a liquid phase to form nitrous acid and nitric acid.

  For the solid organic waste in the mixing tank 3 and the microorganisms present in the liquid organic waste in the acid fermentation tank 4, solid organic waste is obtained using nitrous acid or bound oxygen of nitric acid. In addition, bacteria that degrade can be further improved in the treatment of the solid organic waste. In the mixing tank 3 or the acid fermentation tank 4, the solid organic waste in the mixing tank 3 or the nitrous acid and nitric acid in the liquid organic waste in the acid fermentation tank 4 are converted into harmless nitrogen gas. it can.

  Further, it is conceivable that the methane fermentation liquid to be subjected to the ammonia stripping treatment by the ammonia stripping apparatus 6 is heated with the high-temperature exhaust gas after being combusted by the gas utilization means 8. When the pressure is high, the ammonia removal efficiency in the ammonia stripping device 6 is lowered, and the adjustment of the gas-liquid ratio between the methane fermentation liquor and the exhaust gas is not easy. It is preferable to use air for the ammonia stripping treatment.

  Next, when methane fermentation is performed in the methane fermentation tank 5 after mixing the methane fermentation liquid and the solid organic waste, the fluidity of the mixed liquid after mixing the methane fermentation liquid and the solid organic waste. Is important, and the total solid concentration (TS concentration) of this mixed solution may be mixed so as to be a ratio of 10% to 15%. Specifically, the mixing ratio of the methane fermentation liquid heated to the mixed liquid and the solid organic waste is preferably in the range of 0.5 to 2.0 in terms of mass ratio.

  That is, when the mixing ratio of the methane fermentation liquid and the solid organic waste in the mixed solution is less than 0.5 by mass, the ammonia removal efficiency of the ammonia stripping process in the ammonia stripping device 6 is low. End up. On the other hand, when the mixing ratio of the methane fermentation liquid and the solid organic waste in the mixed liquid is larger than 2.0 by mass ratio, This is not realistic because the problem of an increase in scale and a problem of loss in the recovery of energy used in the ammonia stripping device 6 occur. As a result, by setting the mixing ratio of the heated methane fermentation broth and solid organic waste in the range of 0.5 to 2.0 in terms of mass ratio, the total solid concentration ( Since the TS concentration can be 10% or more and 15% or less, this mixed solution can be efficiently subjected to methane fermentation in the methane fermentation tank 5.

  As described above, according to the first embodiment, the liquid organic waste that has been solubilized by removing contaminants from the solid organic waste is subjected to methane fermentation in the methane fermentation tank 5 to produce a methane fermentation solution. Then, at least a part of the methane fermentation liquid is retained in the ammonia stripping device 6 for 40 minutes or more, heated to a temperature of 70 ° C. or higher and 90 ° C. or lower and ammonia stripped, and the ammonia removal liquid is returned to the return line 11, the methane fermentation tank 5 was returned to the preceding mixing tank 3. As a result, the ammonia removing liquid heated by the ammonia stripping device 6 is returned to the mixing tank 3 through the return line 11 and mixed with the solid organic waste in the mixing tank 3. The temperature of the solid organic waste is a temperature suitable for each of the solubilization treatment in the acid fermentation tank 4 and the methane fermentation treatment in the methane fermentation tank 5.

  Further, the methane fermentation liquid after the solid organic waste is subjected to methane fermentation is retained in the ammonia stripping device 6 for 40 minutes or more and heated to obtain an ammonia removal liquid, whereby the ammonia removal liquid is mixed. The liquid organic waste thus produced can be efficiently solubilized in the acid fermentation tank 4 and the solid content in the liquid organic waste can be re-decomposed, so that the decomposition efficiency of the methane fermentation liquid can be improved. Therefore, the liquid organic waste that has been solubilized by removing impurities from the solid organic waste can be efficiently methane-fermented in the methane fermentation tank 5, and methane fermentation that has been methane-fermented in this methane fermentation tank 5. Since the liquid can be efficiently decomposed by the ammonia stripping device 6 and the ammonia removal liquid from which ammonia has been removed by this ammonia stripping device can be efficiently decomposed by the acid fermentation tank 4, the solid organic by the waste treatment system 1 The processing efficiency of radioactive waste can be improved.

Further, by blowing 200 Nm ³ or more 400 Nm ³ or less in air to methane fermentation is transported has been warmed methane fermentation liquid 1 tons into ammonia stripper 6 in the methane fermentation tank 5, the methane fermentation liquid The ammonia was removed by an ammonia stripping treatment by the ammonia stripping device 6. As a result, ammonia in the methane fermentation broth can be removed as ammonia gas by the ammonia stripping treatment by the ammonia stripping device 6.

  Further, the anaerobic bacteria in the methane fermentation liquid can be sterilized, and the sterilized anaerobic bacteria are returned to the mixing tank 3 via the return line 11, so that the sterilized anaerobic bacteria are converted into the acid fermentation tank. 4 and methane fermentation tank 5 can be re-decomposed and processed. Therefore, the decomposition efficiency of each of the solid organic waste, the methane fermentation liquid, and the ammonia removal liquid can be improved, and the processing efficiency of the methane fermentation liquid in the ammonia stripping process by the ammonia stripping device 6 can be improved.

  Further, the gas containing ammonia separated from the methane fermentation liquid by the ammonia stripping device 6 is mixed with the methane gas generated by the methane fermentation in the methane fermentation tank 5 and burned by the gas utilization means 8. did. As a result, using the combustion heat of methane gas generated in the methane fermentation tank 5 together with the combustion heat of ammonia separated from the methane fermentation liquid, the methane fermentation liquid transferred to the ammonia stripping device 6 is used. Alternatively, the liquid organic waste transferred to the acid fermentation tank 4 can be heated. For this reason, the energy used in the ammonia stripping process in the ammonia stripping apparatus 6 can be used effectively.

  Further, the methane fermentation liquid heated in the ammonia stripping device 6 is returned to the mixing tank 3 via the return line 11 at a mass ratio of less than 0.5 times the methane fermentation liquid. When mixed with solid organic waste, the ammonia removal efficiency from the methane fermentation solution in the ammonia stripping device 6 becomes low. Therefore, the ammonia stripping device 6 can efficiently perform the ammonia stripping process. I can't do it well. Moreover, when this methane fermentation broth is returned to the mixing tank 3 through the return line 11 at a ratio greater than 0.5 times by mass with respect to the methane fermentation broth and mixed with solid organic waste In this case, the amount of methane fermentation broth is increased with respect to the amount of solid organic waste, and the energy used in the ammonia stripping device 6 is wasted.

  Therefore, the ammonia removal liquid heated by the ammonia stripping device 6 is mixed through the return line 11 at a mass ratio of 0.5 to 2.0 times with respect to the solid organic waste. It was set as the structure made to return to the tank 3 and to mix with a solid organic waste. As a result, the ammonia stripping process in the ammonia stripping apparatus 6 can be efficiently performed, and the total solid concentration of the mixed liquid after mixing the solid organic mixture and the ammonia removing liquid becomes an appropriate value. The processing efficiency of each of these solid organic mixture and ammonia removal liquid can be improved.

  In the first embodiment, the ammonia removal solution subjected to the ammonia stripping treatment by the ammonia stripping device 6 is directly returned to the mixing tank 3 through the return line 11, but the second embodiment shown in FIG. As in the embodiment of the present invention, the ammonia removal solution subjected to the ammonia stripping treatment by the ammonia stripping device 6 is solubilized in the solubilization treatment tank 12 as the solubilization means and then mixed through the return line 11. It can also be returned to 3.

  At this time, solid organic waste such as surplus sludge with little impurities can be directly fed into the methane fermentation tank 5. On the other hand, solid organic waste such as garbage containing foreign substances is transferred to the mixing tank 3 after the pretreatment means 2 removes the foreign substances. Further, in the mixing tank 3, the solubilized sludge solubilized in the solubilizing tank 12 and the solid organic waste from which impurities are removed by the pretreatment means 2 are mixed. Then, the solid organic waste mixed with the solubilized sludge in the mixing tank 3 is transferred to the acid fermentation tank 4.

  Furthermore, since the total solid concentration (TS concentration) of the solid organic waste after removing impurities is about 20% to 15%, stirring is not easy. On the other hand, by mixing solubilized sludge with this solid organic waste, the total solid concentration of the solid organic waste after mixing is a slurry-like liquid organic waste of about 10% to 13%. Therefore, processing in the acid fermentation tank 4 and the methane fermentation tank 5 downstream from the mixing tank 3 becomes easy.

  Further, the ammonia removal liquid from which ammonia has been removed from the methane fermentation liquid by the ammonia stripping apparatus 6 is introduced into the solubilization tank 12 as a solubilization process, and an alkaline substance as a strong alkali. Sodium hydroxide (NaOH) is added. Further, the temperature of the ammonia removing liquid discharged from the ammonia stripping device 6 is about 70 ° C. or higher and 90 ° C. or lower. For this reason, as the solubilization processing tank 12, one having good heat retention is preferable. Further, the treatment time in the solubilization treatment tank 12 needs to be 40 minutes or more in total with the treatment time in the ammonia stripping device 6.

  Here, in the case of the waste treatment system 1 according to the first embodiment, since the alkalinity is lowered by the ammonia stripping treatment in the ammonia stripping device 6, the garbage in the solid organic waste is discarded. It is not necessary to treat the excess sludge separately. On the other hand, as described above, the ammonia stripping solution that has been subjected to the ammonia stripping treatment by the ammonia stripping device 6 is introduced into the solubilization treatment tank 12 and sodium hydroxide is added thereto as a solubilized sludge. In the case where the alkalinity of the acid fermenter is not lowered, it is necessary to directly input the solid organic waste into the methane fermenter 5 in order to prevent foaming in the acid fermenter 3.

  Furthermore, the exhaust gas after being combusted by the gas utilization means 8 is high temperature. For this reason, by introducing at least a part of the exhaust gas into the acid fermentation tank 4 and the mixing tank 3, the solid organic waste in the mixing tank 3 and the liquid organic waste in the acid fermentation tank 4 are added. Can warm. Here, the exhaust gas contains nitrogen oxides generated by combustion. Then, by introducing the exhaust gas into the acid fermentation tank 4 and the mixing tank 3, the nitrogen oxides in the exhaust gas are converted into nitric acid or nitrous acid in the liquid organic waste in the acid fermentation tank 4 and in the mixing tank 3. It dissolves in solid organic waste and is removed from this exhaust gas. Further, the nitric acid or oxygen bonded to the nitrous acid is used for decomposition of the solid organic waste by the microorganisms in the acid fermenter 4, and the nitric acid and nitrous acid are converted into harmless nitrogen gas. . Further, the remainder of the exhaust gas that has not been introduced into the acid fermentation tank 4 and the mixing tank 3 may be introduced into the catalyst reduction device 9 and processed, as in the first embodiment.

  Next, the operation of the second embodiment will be described.

  First, sodium hydroxide is used for the purpose of improving the decomposition efficiency of the methane fermentation treatment of the solubilized liquid in the methane fermentation tank 5 in addition to the ammonia stripping treatment in the ammonia stripping device 6. That is, the decomposition efficiency of the solubilized liquid in the methane fermentation treatment is improved when the pH is higher and the temperature is higher when the solubilized liquid is subjected to methane fermentation in the methane fermentation tank 5.

  Therefore, when ammonia is removed from the methane fermentation liquid by the ammonia stripping treatment by the ammonia stripping device 6, carbonate ions that are paired with the ammonia are removed from the methane fermentation liquid. Will decrease the alkalinity. That is, the decrease in the alkalinity of the methane fermentation broth due to the ammonia stripping process in the ammonia stripping device 6 varies depending on the ammonia removal rate from the methane fermentation broth.

Specifically, 0.1 g / L of ammonia nitrogen corresponds to 0.36 g / L as alkalinity (mg-CaCO ₃ / L) in terms of calcium carbonate (CaCO ₃ ). And since the nitrogen concentration of the methane fermentation liquid before the ammonia stripping process is 1000 mg / L or more and 4000 mg / L or less, the ammonia removal rate by the ammonia stripping process in the ammonia stripping apparatus 6 of this methane fermentation liquid is 60. In the case of%, the alkalinity of the ammonia removal liquid after removing ammonia from the methane fermentation liquid decreases by about 2000 mg / L or more and 8000 mg / L or less.

  Therefore, since the alkalinity of the ammonia removing solution that has been subjected to the ammonia stripping treatment by the ammonia stripping device 6 can be greatly reduced, the pH of the alkali removing solution can be increased by adding a small amount of sodium hydroxide. Further, the temperature of the ammonia removal liquid after the ammonia stripping treatment by the ammonia stripping device 6 is as high as 70 ° C. or higher and 90 ° C. or lower. For this reason, by adding sodium hydroxide to this high-temperature ammonia removal solution and treating it with alkali to make it a solubilized sludge, it is returned to the return line 11 and mixed with the solid organic waste in the mixing tank 3, The solubilization process in the acid fermentation tank 4 subsequent to the mixing tank 3 and the methane fermentation process in the methane fermentation tank 5 can be efficiently decomposed, and the solubilization process in these acid fermentation tanks 4 and the methane fermentation tank 5 The amount of sludge produced by methane fermentation treatment can be reduced.

  Furthermore, a large amount of ammonia is contained in the methane fermentation broth. For this reason, when this methane fermentation broth was subjected to ammonia stripping treatment with the ammonia stripping device 6, a large amount of sodium hydroxide was required to raise the pH of the methane fermentation broth. Further, in the ammonia stripping treatment by the ammonia stripping device 6, the nitrogen removal rate is increased by making the methane fermentation solution alkaline.

  However, when an ammonia stripping treatment is performed with the ammonia stripping device 6 after adding a pH adjusting reagent such as a sodium hydroxide solution to make the methane fermentation solution alkaline, the ammonia stripping treatment may be performed even if the methane fermentation solution is subjected to ammonia stripping treatment. The carbonate ions paired with ammonia are not removed from this methane fermentation broth.

  For this reason, the alkalinity of the ammonia removal liquid after ammonia is removed from this methane fermentation liquid does not fall. Therefore, in order to increase the pH of the ammonia removing liquid by adding sodium hydroxide or the like to the ammonia removing liquid after the ammonia stripping treatment by the ammonia stripping apparatus 6 and adding it, A pH adjusting reagent such as sodium hydroxide is required.

  As described above, according to the second embodiment, the ammonia removal liquid from which ammonia has been removed by the ammonia stripping device 6 is introduced into the solubilization treatment tank 12 and solubilized by adding sodium hydroxide. The solubilized sludge was treated to return the solubilized sludge to the mixing tank 3 through the return line 11 and mixed with the solid organic waste in the mixing tank 3.

  As a result, by adding a small amount of sodium hydroxide, the alkalinity of the ammonia removal solution can be increased to make solubilized sludge, and also by heating by the ammonia stripping device 6 and addition of sodium hydroxide in the solubilization treatment tank 12. Alkaline treatment can be used in combination. Therefore, since the solubilization efficiency of the solid organic waste mixed with this solubilized sludge in the acid fermentation tank 4 and the methane fermentation efficiency in the methane fermentation tank 5 can be improved, the solid organic waste by the waste treatment system 1 can be improved. In addition, the amount of sludge produced from the solid organic waste in the waste treatment system 1 can be reduced.

  Next, Example 1 of the present invention will be described.

  First, a methane fermentation liquid obtained by methane fermentation of solid organic waste in the methane fermentation tank 5 is heated to 85 ° C., and air is aerated, and this methane fermentation liquid is ammonia stripped by the ammonia stripping device 6. Processed. At this time, the residence time of the methane fermentation liquor in the reaction tank of the ammonia stripping device 6 was set to 30 minutes, and the air flow rate into the reaction tank was set to a gas-liquid ratio of 300.

  The air was vented to the reaction tank in two ways. Specifically, in the first aeration method, air was ventilated only in the gas phase part on the reaction tank to remove nitrogen, thereby obtaining treated water 1 as an ammonia removing liquid. In the second aeration method, the gas phase portion on the reaction vessel is vented at a gas / liquid ratio of 250, and air is also introduced into the liquid phase portion, which is a methane fermentation liquid, in the reaction vessel. The treated water 2 as an ammonia removing solution was obtained by aeration with nitrogen.

As a result, as shown in Table 1, the alkalinity, ammonia concentration (NH ₄ -N) and carbonic acid concentration of the methane fermentation liquid, the treated water 1 and the treated water 2 before being subjected to nitrogen removal treatment by the ammonia stripping device 6 Comparing each of (S-IC), it was found that the ammonia stripping treatment by the ammonia stripping device 6 decreased the values of the alkalinity, ammonia concentration, and carbonic acid concentration.

  Next, a second embodiment of the present invention will be described.

  First, while heating the methane fermentation liquid obtained by methane fermentation of the solid organic waste in the methane fermentation tank 5 to 70 ° C., 80 ° C., or 90 ° C., air is passed through each of the methane fermentation liquid. Then, each of these methane fermentation broths was subjected to ammonia stripping treatment by the ammonia stripping device 6. At this time, the residence time of these methane fermentation broths in the reaction tank of the ammonia stripping apparatus 6 was set to 30 minutes, and the air flow rate into the reaction tank was set to a gas-liquid ratio of 300.

  And each of the ammonia removal liquid which carried out the ammonia stripping process of each methane fermentation liquid with this ammonia stripping apparatus 6 and solid organic waste are mixed and mixed in the mixing tank 3 by the ratio of mass ratio 1: 1. From the waste as liquid, these wastes were continuously charged into the acid fermentation tank 4 having a hydraulic residence time of 3 days. Then, the liquid temperature in the acid fermenter 4 was measured when the temperatures of the wastes after mixing were 5 ° C, 10 ° C, 15 ° C, 20 ° C and 25 ° C, respectively.

  As a result, as shown in FIG. 3, the temperature of the waste in the acid fermenter 4 was 38 ° C. or higher and 58 ° C. or lower. Accordingly, the temperature of each waste in the acid fermenter 4 is a temperature suitable for the decomposition of the solid organic waste by the microorganisms in the acid fermenter 4, so that a heat exchanger (not shown) or the like is not used. The energy used in the ammonia stripping process in the ammonia stripping apparatus 6 can be used effectively.

  Next, Embodiment 3 of the present invention will be described.

  First, after adjusting the TS concentration of the excess sludge as solid organic waste generated from the sewage treatment facility to 8%, the acid fermenter 4 having a volume of 3 L and a liquid temperature of 55 ° C., and a volume of 12 L The surplus sludge was used under the condition that the surplus sludge stayed in the methane fermenter 5 was set to 30 days using an experimental apparatus equipped with the methane fermenter 5 having a liquid temperature of 38 ° C. as the waste treatment system 1. Was subjected to methane fermentation treatment in the methane fermentation tank 5. At this time, the experiment system and the control system were continuously tested in the waste treatment system 1.

  In the experimental system, the temperature of the methane fermentation liquid is set to 85 ° C., air is passed through the methane fermentation liquid at a gas-liquid ratio of 300, and the ammonia stripping device 6 performs ammonia stripping treatment. After the ammonia removal liquid after the ammonia stripping treatment is cooled to near room temperature, the ammonia removal liquid is mixed at a mass ratio equal to the excess sludge and then solubilized in the acid fermentation tank 4 and then the methane fermentation tank 5. Methane fermentation. At this time, sodium hydroxide was not added to the methane fermentation liquid and the ammonia removal liquid before and after the ammonia stripping treatment in the ammonia stripping apparatus 6.

  On the other hand, in the control system, the methane fermentation liquid is not subjected to the ammonia stripping treatment in the ammonia stripping device 6, and the methane fermentation liquid is mixed at a mass ratio equal to the excess sludge, and then the acid fermentation tank 4 is used. After solubilization, methane fermentation was carried out in the methane fermentation tank 5.

  As a result, as shown in Table 2, the alkalinity in the acid fermenter 4 was reduced by performing ammonia stripping treatment of the methane fermentation broth with the ammonia stripping device 6 from the analysis result in the steady state. However, even when this methane fermentation broth was subjected to ammonia stripping treatment with the ammonia stripping device 6, there was almost no difference in the decomposition efficiency of the TS concentration of the methane fermentation broth.

  Next, a fourth embodiment of the present invention will be described.

  First, using 10 L of methane fermentation liquor that is methane fermentation sludge generated in the methane fermentation tank 5 in the continuous experiment of the experimental system in Example 3, the liquid temperature of the methane fermentation liquor was set to 85 ° C. Air is passed through the fermentation broth at a gas-liquid ratio of 300, and ammonia stripping is performed in the ammonia stripping device 6 for 30 minutes to obtain an ammonia removal solution. Thereafter, a predetermined amount of the ammonia removal liquid is sampled every 30 minutes while the liquid temperature of the ammonia removal liquid is maintained at 85 ° C., and the heating time is 30 minutes, 60 minutes, 90 minutes, 120 minutes, and 150 minutes. Each ammonia removal solution was used as a sample solution.

  And after the temperature of these sample liquids fell to room temperature vicinity, 40 g of these sample liquids were each extract | collected in the vial bottle. After that, after adding 40 g of the seed sludge to each of these vials using the excess sludge before methane fermentation of the methane fermentation liquid as seed sludge, the tops of these vials are purged with nitrogen gas, The bottle was sealed after expelling the air in the bottle. Further, as a blank test, 80 g of seed sludge was collected in a vial, and then the upper portion of the vial was purged with nitrogen gas, and the air in the vial was expelled and then sealed.

  Thereafter, each of these vials was kept at 38 ° C., then these vials were shaken, seed sludge in these vials was cultured, and the amount of gas generated in these vials was measured.

  As a result, as shown in FIG. 4, in the sample solution with the heating time of 30 minutes, the difference from the blank test was hardly observed. Furthermore, since there is a correlation between the decomposition rate of TS concentration by methane fermentation treatment and the amount of gas generated, there was almost no difference in the decomposition rate of TS concentration between the experimental system in Example 3 and the control system. It was found that this was caused by a short treatment time at the time of the ammonia stripping treatment by the ammonia stripping device 6.

  On the other hand, by heating the methane fermentation broth for 60 minutes during the ammonia stripping treatment, the difference in the amount of gas generated between the methane fermentation broth and the blank test is 30 minutes warming treatment for the methane fermentation broth during the ammonia stripping treatment. It was more than 6 times the case. That is, as shown in FIG. 4, it can be seen that the amount of biogas generated from the methane fermentation solution is rapidly increased by heating the methane fermentation solution for 60 minutes. From this, it was found that the amount of biogas generated during the ammonia stripping process in the ammonia stripping device 6 can be increased by setting the residence time of the methane fermentation solution in the ammonia stripping device 6 to 60 minutes or longer. .

  Next, a fifth embodiment of the present invention will be described.

  First, using 10 L of methane fermentation broth, which is methane fermentation sludge generated in the continuous experiment of the experimental system in Experimental Example 3, the methane fermentation broth was heated to a liquid temperature of 85 ° C. On the other hand, air was aerated at a gas-liquid ratio of 300, and this methane fermentation liquid was subjected to ammonia stripping treatment by the ammonia stripping apparatus 6. As a result, the nitrogen removal rate by the ammonia stripping treatment from this methane fermentation broth was 72%. Furthermore, 1 mol / L sodium hydroxide aqueous solution was titrated with respect to 50 mL of each of the methane fermentation solution and the ammonia removal solution before and after the ammonia stripping, and the change in pH of each of the methane fermentation solution and the ammonia removal solution was measured.

  As a result, as shown in FIG. 5, when comparing the methane fermentation liquid before the ammonia stripping treatment with the ammonia stripping apparatus 6 and the ammonia removal liquid after the ammonia stripping treatment, It was found that the pH can be increased with a lower sodium hydroxide addition rate. Therefore, it has been found that the pH can be efficiently increased with a small sodium hydroxide addition rate by adding sodium hydroxide after ammonia stripping treatment of the methane fermentation liquid to obtain an ammonia removal liquid.

  Next, a sixth embodiment of the present invention will be described.

  First, a predetermined amount of a 1 mol / L sodium hydroxide aqueous solution was added to the ammonia removal liquid generated in Example 5 above, and then the pH was measured and then sealed, and in this state, the ammonia removal liquid was placed at 20 ° C., 55 ° C. and It was made to react for 1 hour, keeping at 80 degreeC each. Thereafter, the ammonia removal liquid reacted in these states was centrifuged, and the chemical oxygen demand (CODcr) of the supernatant was measured. The ratio of CODcr in the supernatant of the ammonia removal solution after the reaction to the total CODcr of the ammonia removal solution before the reaction was calculated as the solubilization rate.

  As a result, as shown in FIG. 6, it was found that the solubilization rate was higher as the pH was higher and the liquid temperature was higher. Therefore, the pH can be increased efficiently with a small sodium hydroxide addition rate, and the temperature of the ammonia removal solution after the ammonia stripping treatment is as high as 70 ° C. or more and 90 ° C. or less. It was found that the ammonia removal solution can be efficiently solubilized by solubilization and the decomposition rate of the ammonia removal solution can be improved.

  Next, a seventh embodiment of the present invention will be described.

  First, after adjusting the TS concentration of the excess sludge as solid organic waste generated from the sewage treatment facility to 8%, the acid fermenter 4 having a volume of 3 L and a liquid temperature of 55 ° C., and a volume of 12 L The surplus sludge was used under the condition that the surplus sludge stayed in the methane fermenter 5 was set to 30 days using an experimental apparatus equipped with the methane fermenter 5 having a liquid temperature of 38 ° C. as the waste treatment system 1. Was treated with methane fermentation.

  The experiment was performed under three conditions. First, in the first experimental condition, the methane fermentation liquid obtained by methane fermentation of the excess sludge is not subjected to the ammonia stripping treatment in the ammonia stripping device 6, and this methane fermentation liquid is mixed at a mass ratio equal to the excess sludge in the mixing tank 3. And then solubilized in the acid fermentation tank 4 and then subjected to methane fermentation in the methane fermentation tank 5 (denoted as untreated in Table 3).

  Next, in the second experimental condition, the temperature of the methane fermentation liquid obtained by methane fermentation of the excess sludge is set to 85 ° C., and air is aerated with the methane fermentation liquid at a gas-liquid ratio of 300 to form an ammonia stripping device. Ammonia stripping treatment is performed at 6 for 60 minutes to obtain an ammonia removal solution. Thereafter, the ammonia removing liquid is kept at a liquid temperature of 85 ° C. for 30 minutes and then cooled to near room temperature. Further, the cooled ammonia removal liquid was mixed in the mixing tank 3 at a mass ratio equal to the excess sludge, solubilized in the acid fermentation tank 4, and then methane-fermented in the methane fermentation tank 5 (90 in Table 3). Notation as minute processing).

  In the third experimental condition, the temperature of the methane fermentation liquid obtained by methane fermentation of surplus sludge is set to 85 ° C., and air is passed through the methane fermentation liquid at a gas-liquid ratio of 300 to form an ammonia stripping device. Ammonia stripping treatment is performed at 6 for 60 minutes to obtain an ammonia removal solution. Thereafter, 2 g / L of sodium hydroxide is added to the ammonia removal liquid in the solubilization treatment tank 12, and then the liquid temperature is kept at 85 ° C. for 30 minutes, followed by cooling to near room temperature. Furthermore, this cooled ammonia removing liquid was mixed in the mixing tank 3 at a mass ratio equal to the excess sludge, solubilized in the acid fermentation tank 4, and then methane-fermented in the methane fermentation tank 5 (water in Table 3). It is expressed as sodium oxide addition treatment).

  As a result, as a result of analyzing the suspended solids concentration (Suspended Solids: SS) in the methane fermenter in the steady state under the first to third experimental conditions, in Example 3 of the above-described 30 minute heating treatment, Although no difference was observed between the experimental system and the control system, as shown in Table 3, it was found that when the heat treatment was performed for 90 minutes, the SS concentration was lower and the decomposition rate was improved compared to the untreated case. . Further, it was found that when sodium hydroxide was added after the stripping treatment, the SS concentration was further lowered and the decomposition rate was improved.

It is explanatory drawing which shows the processing apparatus of the solid organic waste of the 1st Embodiment of this invention. It is explanatory drawing which shows the processing apparatus of the solid organic waste of the 2nd Embodiment of this invention. It is a graph which shows the relationship between the temperature of the waste at the time of the ammonia stripping process in Example 1 of the processing apparatus of the solid organic waste of this invention, and the temperature of an acid fermenter. It is a graph which shows the relationship between the heating time of the waste at the time of the ammonia stripping process in Example 2 of the processing apparatus of the solid organic waste of this invention, and the gas generation amount by methane fermentation. It is a graph which shows the relationship between the sodium hydroxide addition rate before and behind ammonia stripping process in Example 3 of the processing apparatus of the solid organic waste of this invention, and pH. It is a graph which shows the change of the solubilization rate at the time of changing pH and temperature at the time of the ammonia stripping process in Example 3 of the processing apparatus of the solid organic waste of this invention.

Explanation of symbols

1 Waste treatment system as solid organic waste treatment device 5 Methane fermentation tank as methane fermentation means 6 Ammonia stripping device as heating means
11 Return line as return means

Claims (6)

A methane fermentation process in which solid organic waste is treated with methane fermentation to produce methane fermentation liquor,
A heating process in which at least a part of the methane fermentation liquid treated in the methane fermentation process is retained for 40 minutes or more and heated to a temperature of 70 ° C. or higher and 90 ° C. or lower;
A return process for returning the methane fermentation liquid heated in this heating process to the methane fermentation process. Heating process, the methane fermentation liquid is warmed is blown with 200 Nm ³ or more 400 Nm ³ or less in air to the methane fermentation liquor 1000 kg, are ammonia stripping step of removing the ammonia in the methane fermentation liquid The processing method of the solid organic waste of Claim 1 characterized by the above-mentioned. Comprising a solubilization step of adding sodium hydroxide to the methane fermentation broth from which ammonia has been removed in the ammonia stripping step and solubilizing,
The method for treating solid organic waste according to claim 2, wherein the returning step returns the methane fermentation liquid solubilized in the solubilizing step to the solid organic waste and mixes them. The gas combustion process which mixed and combusted the gas containing the ammonia isolate | separated from the methane fermentation liquid in the ammonia stripping process with the methane gas generated in the methane fermentation process was provided. Solid organic waste treatment method. The methane fermentation liquid heated in the heating step is mixed with the solid organic waste at a ratio of 0.5 to 2.0 times by mass with respect to the solid organic waste. The processing method of the solid organic waste in any one of Claim 1 thru | or 4. Methane fermentation means for methane fermentation treatment of solid organic waste to methane fermentation,
A heating means for retaining at least a part of the methane fermentation liquid treated by the methane fermentation means for 40 minutes or more and heating the methane fermentation liquid to a temperature of 70 ° C. or higher and 90 ° C. or lower;
A solid organic waste processing apparatus comprising: a return means for returning the methane fermentation liquid heated by the heating means to the methane fermentation step.

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