JP2005169329A - Treatment method for organic waste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for realizing an improvement in treatment efficiency and reduction in the caloric value required for heating in a solubilization step, while realizing improvement in the methane recovery rate and volume reduction in the discharge amount of waste sludge generated by anaerobic treatment to the outside of the system, when various kinds of organic waste such as various kinds of organic sludge and solid organic waste are anaerobically treated. <P>SOLUTION: This treatment method for organic waste is at least provided with (1) a first solubilization step for solubilizing sludge like organic waste at the temperature range of 100-150°C, (2) a first solid/liquid separation step for solid/liquid separating the solubilized sludge solubilized in the first solubilization step, (3) a second solubilization step for solubilizing separated sludge separated in the first solid/liquid separation step at the temperature range of 160-230°C, (4) a second solid/liquid separation step for solid/liquid separating the solubilized sludge solubilized in the second solubilization step, and (5) an anaerobic treatment step for anaerobically treating the separated liquid separated in the first solid/liquid separation step and second solid/liquid separation step. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a method for recovering methane gas by anaerobically treating organic waste, and more specifically, reducing the volume of excess sludge generated from anaerobic treatment and reducing the amount of methane gas recovered. It is related with the processing method of the organic waste which aims at improvement.

  Conventionally, as a method of treating organic sludge generated from water treatment facilities that treat sewage, human waste, and various industrial wastewater, the biological matter of anaerobic microorganisms such as methane bacteria is treated by anaerobic treatment of organic matter in organic sludge. An anaerobic treatment method is generally performed in which digestion gas (hereinafter simply referred to as methane gas) mainly containing methane or carbon dioxide gas is generated by the action, and methane gas is effectively used as fuel. In the anaerobic treatment method, a method of reducing the volume of excess sludge generated by the anaerobic treatment is also performed.

  As a conventional method for reducing the volume of sludge and performing anaerobic treatment, it is easy to supply organic sludge from the sludge supply path 54 to the anaerobic tank 50 and to make the supplied sludge anaerobic in the anaerobic tank 50 in FIG. A first anaerobic treatment step for almost terminating the reaction of the degradable organic component, and the digested sludge decomposed (anaerobic treatment) in the first anaerobic treatment step from the digested sludge circulation path 55 to a solid-liquid separator ( A solubilization process in which the concentrated sludge is supplied to the concentrating device 52) and concentrated by a solid-liquid separator, and the concentrated sludge is supplied from the concentrated sludge circulation path 57 to the solubilizing device 51 and solubilized at 100 to 180 ° C. From the second anaerobic treatment step in which the solubilized sludge solubilized in the process is circulated and supplied from the solubilized sludge supply path 58 to the anaerobic tank 50 or a separate anaerobic tank for decomposition (anaerobic treatment). An organic sludge treatment method is disclosed And has (see Patent Document 1).

Moreover, the sludge mixed solution is led from the organic matter removing tank (anaerobic tank 50) for biologically treating the organic wastewater to the sludge heating tank (solubilization tank 51), and the sludge mixed solution is heated at a temperature of 50 ° C. When heating at 120 ° C. to change the sludge into a biologically degradable form, the mixture is then returned to the organic matter removal tank 50 where the sludge is biologically treated to reduce the volume. 3 discloses a method in which a heat exchanger 53 is provided in the digested sludge circulation path 59 between the organic matter removing tank 50 and the sludge heating tank 51 described with a one-dot chain line in FIG. 3 (see Patent Document 2).
JP-A-1-224100 JP 2002-248500 A

  The problem to be solved is that, in the conventional technology, in the method of solubilizing anaerobic sludge and again anaerobically treating it, it is possible to reduce the volume of excess sludge to be discharged. In the solubilization process, the processing efficiency is low and the processing takes time, so the solubilization tank becomes large and the amount of heat required for heating increases, and it is possible depending on the decomposition conditions of difficult-to-decompose organic matter. When solubilized, organic substances with good decomposability are decomposed more than necessary, and the methane gas recovery rate is lowered. In particular, when organic wastes of different properties are treated in the same temperature condition in a single solubilization step, the treatment efficiency is further reduced, the solubilization treatment tank becomes excessive, and the amount of heat necessary for heating is also increased. It is a point to be increased.

  The present invention is a generic term for various organic sludges generated from water treatment facilities for treating sewage, human waste and various industrial wastewaters, and sludge-like organic wastes such as livestock manure (hereinafter referred to as the organic sludges and organic wastes). Or anaerobic treatment of various organic wastes such as garbage, pruned branches and fishery / agricultural wastes (hereinafter collectively referred to as solid organic wastes) Providing methods to improve the recovery of methane gas and reduce the volume of excess sludge generated by anaerobic treatment, as well as to improve the treatment efficiency and the amount of heat required for heating in the solubilization process It was made for the purpose.

  The gist of the present invention for achieving the above object is that, in the invention according to claim 1, in the method for anaerobically treating organic waste, (i) sludge-like organic waste is heated to a temperature of 100 to 150. A first solubilization step for solubilization treatment in the range of ° C., (b) a first solid-liquid separation step for solid-liquid separation of the solubilized sludge solubilized in the first solubilization step, and (c) the first A second solubilization process in which the separated sludge separated in the one-solid-liquid separation process is solubilized in a temperature range of 160 to 230 ° C., and (d) the solubilized sludge solubilized in the second solubilization process is solidified. A second solid-liquid separation step for liquid separation, and (e) an anaerobic treatment step for anaerobically treating the separation liquid separated in the first solid-liquid separation step and the second solid-liquid separation step. This is a method for treating organic waste.

  The invention according to claim 2 is a first solubilization method in which an organic waste is subjected to an anaerobic treatment in which (a) the sludge-like organic waste is solubilized in a temperature range of 100 to 150 ° C. (B) a first solid-liquid separation step for solid-liquid separation of the solubilized sludge solubilized in the first solubilization step, and (c) crushing solid organic waste to form a mud Waste crushing step, (d) the sludge separated in the first solid-liquid separation step and the crushing waste crushed in the waste crushing step in a temperature range of 160 to 230 ° C. A second solubilization step, (e) a second solid-liquid separation step for solid-liquid separation of the solubilized sludge solubilized in the second solubilization step, (f) the first solid-liquid separation step and the above At least an anaerobic treatment step for anaerobically treating the separation liquid separated in the second solid-liquid separation step is provided. Which is a method of treating organic waste characterized.

  Further, the invention according to claim 3 is the method for treating organic waste according to claim 1 or claim 2, wherein sludge-like organic waste and solubilized sludge to be supplied to the first solubilization step are used. Organic provided with a second heat exchange step for heat exchange between the separated sludge supplied to the first heat exchange step and the second solubilization step for heat exchange or the crushed waste crushed in the waste crushing step and the solubilized sludge This is a treatment method for radioactive waste.

  The invention according to claim 4 is an anaerobic treatment tank in which the anaerobic treatment step in the organic waste treatment method according to any one of claims 1 to 3 is an anaerobic treatment tank. Organic, which is an upflow anaerobic treatment process in which the liquid to be treated flows upward through the self-granulated sludge bed of microorganisms formed inside, and the organic matter in the liquid to be treated is decomposed by the biological action of microorganisms. This is a waste disposal method.

  In the above-described configuration, the anaerobic treatment step causes the liquid to be treated to flow upward in the self-granulating sludge bed of microorganisms formed in the anaerobic treatment tank, and the organic matter in the liquid to be treated is caused by the biological action of the microorganisms. An upflow anaerobic treatment device that decomposes and separates into three phases of product gas, treatment liquid, and solid content at the top is preferable because it can be treated with a high concentration sludge load and the treatment time can be shortened. Any treatment apparatus such as a normal anaerobic tank, a two-tank anaerobic treatment apparatus provided with an acid fermentation tank, or a biological carrier treatment apparatus filled with a microorganism carrier to form a fixed bed or a fluidized bed may be used.

  Moreover, the sludge solubilization conditions in the solubilization step are performed in the first solubilization step with a treatment temperature of 100 to 150 ° C., preferably 120 to 140 ° C., and 5 to 60 minutes above the saturated water vapor pressure. Moreover, in a 2nd solubilization process, process temperature 160-230 degreeC, Preferably it is 180-230 degreeC, and it hold | maintains for 5 to 60 minutes above saturated water vapor pressure. The solids concentration of the supplied sludge is preferably 2 to 10 wt%, and when the pH is pre-adjusted with alkali before the solubilization step, it is adjusted to pH 8 or higher, preferably pH 9.5 or higher. Furthermore, the heating in the solubilization step is performed by a direct heating method using steam injection, combustion furnace circulation, or the like, or an indirect heating method using a heat exchanger or the like, with the heat of combustion of methane gas generated in the anaerobic treatment step.

  Moreover, as a solid-liquid separation device for solubilized sludge such as a first solid-liquid separation step and a second solid-liquid separation step, a centrifugal separator, various filters, a membrane separation device, a precipitation tank, or the like can be mainly used. . The water content of the separated sludge is adjusted to 98 wt% or less, preferably 96 to 90 wt%.

  In addition, as a waste crushing device that crushes solid organic waste that is not sludge, the mechanical type that crushes the object to be treated with a fixed blade at high speed or crushes with a high-speed rotary blade A crusher, a grinding stone mill, or the like is used, and when there is little water in the organic waste, a wet crushing device that mixes and crushes water is used. The organic waste is preferably crushed to 1 mm or less and sludged.

  The present invention provides a solubilization step for solubilizing at a high temperature, thereby reducing the molecular weight of proteins, lipids and cellulose, and the amount of waste sludge generated by anaerobic treatment of the solubilized sludge having a low molecular weight. Can be drastically reduced, and the waste sludge disposal cost can be greatly reduced and the load on the environment can be reduced. Moreover, since many organic substances can be decomposed and converted into methane gas in a short time in the anaerobic treatment step, the amount of methane gas generated per unit organic waste amount can be increased.

  In addition, by providing the high-temperature solubilization process in two stages with different processing temperatures, it is possible to prevent the decomposition of the organic substance with good decomposability more than necessary and to gasify it. The power cost can be reduced and the apparatus can be downsized.

  In addition, sludge that has been heat-treated at a high temperature can be easily separated into solid and liquid, so that solid-liquid separation can be performed efficiently. By returning only the separated liquid phase to the anaerobic process, the ash content in the digested sludge can be reduced. In addition, by solubilizing in two stages, most of the residual sludge discharged from the second solid-liquid separation step also becomes ash and organic matter that is difficult to biodegrade. Decomposed organic matter can be separated and discarded, and the amount of discharged sludge can be made extremely small.

  In the invention described in Item 2, solid organic waste containing a large amount of organic sludge and cellulose fibers which are difficult to be anaerobically treated is solubilized by a process suitable for the properties of the waste. There is also an effect that the apparatus can be more efficiently reduced in the solubilization process.

  In the invention described in item 3, since heat recovery is achieved by the heat exchange process, the amount of heating heat in the solubilization process in a high temperature state can be reduced, and the amount of heat that cannot be recovered by heat exchange is also added to the anaerobic tank. It is also used for heating purposes and has the effect of reducing operating costs.

  Further, in the invention described in item 4, by using the upward flow anaerobic treatment step as the anaerobic treatment step, the treatment can be performed with a high concentration sludge load, and the treatment time can be shortened. Anaerobic treatment.

  Providing a method for improving the recovery efficiency of methane gas and reducing the amount of excess sludge generated by anaerobic treatment outside the system, as well as improving the treatment efficiency and reducing the amount of heat required for heating in the solubilization process The object was achieved by providing a high temperature solubilization step in two stages.

  FIG. 1 is a system diagram of an organic waste anaerobic treatment method according to an embodiment of the present invention. In the figure, 1 is a first possible solubilizing treatment of sludge-like organic waste to be treated at a high temperature. 1 is a first solubilization tank which is a solubilization process, and 2 is a temperature higher than that of the first solubilization tank 1 for separating sludge obtained by solid-liquid separation of the solubilized sludge solubilized in the first solubilization tank 1. It is the 2nd solubilization tank which is the 2nd solubilization process which solubilizes in the state of this.

  No. 3 forms a self-granulated sludge bed of microorganisms in the anaerobic treatment tank, and the separated liquid obtained by solid-liquid separation of the solubilized sludge solubilized in the first solubilization tank 1 and the second solubilized liquid The separated liquid obtained by solid-liquid separation of the solubilized sludge solubilized in the tank 2 is passed upward, and the organic matter in the separated liquid is decomposed by the biological action of microorganisms forming self-granulating sludge. Upstream anaerobic treatment device (hereinafter referred to as UASB device) that converts to methane gas and separates and processes the product gas, treatment liquid, and solids with a three-phase separation member provided at the top of the anaerobic treatment tank It is said).

  Moreover, 4 is the 1st heat exchange of the 1st heat exchange process which heat-exchanges the sludge-like organic waste and the solubilized sludge solubilized in the 1st solubilization tank 1, and collect | recovers the calorie | heat amount of solubilized sludge. 5 is a heat treatment of the separated sludge obtained by solid-liquid separation of the solubilized sludge solubilized in the first solubilization tank 1 and the solubilized sludge solubilized in the second solubilization tank 2. It is the 2nd heat exchanger of the 2nd heat exchange process which exchanges and collect | recovers the calorie | heat amount of solubilized sludge. The first and second heat exchangers 4 and 5 are preferably arranged because heat recovery can reduce the amount of heating heat in the solubilization process in a high temperature state. Not necessary.

  Reference numeral 6 denotes a first solid-liquid separation device in a first solid-liquid separation step for solid-liquid separation of the solubilized sludge solubilized in the first solubilization tank 1, and 7 denotes a second solubilization tank 2. It is the 2nd solid-liquid separation apparatus of the 2nd solid-liquid separation process of carrying out solid-liquid separation of the solubilized solubilized sludge.

  Next, waste organic sludge (hereinafter referred to as sludge) such as surplus sludge, initial settling sludge, septic tank sludge, human waste sludge, livestock manure, and crushed raw garbage (disposer sludge), which is the organic waste, is treated. The processing method to do is explained in full detail below. In FIG. 1, the sludge is supplied to the first heat exchanger 4 from the sludge supply path 20, exchanges heat with the solubilized sludge from the first solubilization tank 1, and is heated to a predetermined temperature to be first solubilized tank 1. To be supplied. In addition, it is also possible to process the sludge which made the solid organic waste into the mud with the processing apparatus outside the system.

  The sludge supplied to the first solubilization tank 1 is maintained at a treatment temperature of 100 to 150 ° C., preferably 120 to 140 ° C. and a saturated water vapor pressure or more for 5 to 60 minutes, so that proteins, lipids and cellulose in the sludge are retained. Refractory substances such as are efficiently reduced in molecular weight and solubilized. Moreover, 2-10 wt% of the solid substance concentration of the sludge supplied is preferable. Moreover, when pre-adjusting pH with an alkali before a solubilization process, it adjusts to pH 8 or more, Preferably it is pH 9.5 or more. Furthermore, the sludge is heated in the first solubilization tank 1 by supplying methane gas generated in the UASB device 3 to a combustion device (not shown) and using the combustion heat, the sludge is directly injected by steam injection or combustion furnace circulation. It is performed by an appropriate method such as a heating method or an indirect heating method of heating by heat exchange using a heat medium.

  The solubilized sludge solubilized in the first solubilization tank 1 is supplied to the first solid-liquid separator 6 and separated into sludge and liquid which are solid contents. The separated separated sludge is supplied to the second heat exchanger 5 from the separated sludge supply path 22, exchanges heat with the solubilized sludge from the second solubilization tank 2, and is heated to a predetermined temperature to be second solubilized tank. 2 is supplied. Further, the separation liquid is supplied to the UASB apparatus 3 from the separation liquid supply path 24.

  The sludge supplied to the second solubilization tank 2 is solubilized in the first solubilization tank by being maintained at a treatment temperature of 160 to 230 ° C., preferably 180 to 230 ° C. for 5 to 60 minutes above the saturated water vapor pressure. Refractory substances such as cellulose fibers that have not been treated are solubilized by being treated under higher temperature solubilization conditions. In addition, the heating of the sludge in the 2nd solubilization tank 2 is performed by the method similar to the 1st solubilization tank 1. FIG. The separated sludge is adjusted to a moisture content of 98 wt% or less, preferably 96 to 90 wt%.

  The solubilized sludge solubilized in the second solubilization tank 2 is supplied to the second solid-liquid separator 7 and separated into sludge and liquid which are solid contents. The separated separated sludge is discharged out of the system as excess sludge from the separated sludge discharge path 26, and is disposed of by a sludge treatment device such as a composting treatment device (not shown) or landfill. Further, the separation liquid is supplied to the UASB apparatus 3 from the separation liquid supply path 25.

  By allowing the separated liquid supplied to the UASB apparatus 3 to flow upward, the organic matter in the separated liquid is decomposed by the biological action of microorganisms that form self-granulating sludge and converted into methane gas. A three-phase separation member provided at the upper part of the gas treatment tank is separated into three phases of product gas, treatment liquid, and solid content, and the generated methane gas is supplied from a methane gas discharge path 28 to a gas holder (not shown) and then as necessary. It is desulfurized and used as a heating fuel, power generation fuel, fuel cell fuel, and the like.

  The processing liquid processed by the UASB apparatus 3 is extracted from the processing liquid extraction path 27 and, if necessary, processed by a wastewater treatment apparatus such as an activated sludge treatment apparatus or a dephosphorization apparatus (not shown). The sludge generated and discharged is concentrated in a sedimentation tank and recycled as organic waste.

  For the purpose of providing a more efficient and miniaturized method in the solubilization process, organic sludge and solid organic waste that contains a large amount of cellulose fibers that are difficult to be anaerobically treated are suitable for the properties of the waste. It was achieved by solubilizing in the process.

  FIG. 2 is a system diagram of another embodiment of the present invention, and members having the same functions as those in FIG. Further, detailed description thereof will be omitted, and members different from those in FIG. 1 will be described.

  8 is a crushing device for the waste crushing process that crushes solid organic waste such as food waste, pruned branches and fishery / agricultural wastes into sludge. A wet crushing device that mixes and crushes is used.

  Solid organic waste is supplied to the crushing device 8 from the solid waste supply path 20b, and the organic waste is crushed to 1 mm or less, and supplied as crushed sludge to the high-temperature second solubilization tank 2 from the crushed sludge supply path 29. And solubilized. In addition, the crushed waste crushed in the waste crushing step is not directly supplied to the second solubilization tank, but is secondly passed through the second heat exchanger 5 as shown in the two-dot chain line in FIG. Heat exchange with the solubilized sludge solubilized in the solubilization tank 2 and heating to a predetermined temperature may be followed by supplying to the second solubilization tank 2. The sludge-like organic waste is supplied to the first heat exchanger 4 from the sludge supply path 20a, exchanges heat with the solubilized sludge from the first solubilization tank 1, and is heated to a predetermined temperature for the first possibility. It is supplied to the solubilization tank 1 and solubilized. In addition, the process conditions in the 2nd solubilization tank 2, the process in a back | latter stage apparatus, and the process of the sludge supplied to the 1st solubilization tank 1 are performed by the same operation as the method demonstrated based on the said FIG.

  Various organic sludge generated from water treatment facilities that treat sewage, human waste, and various industrial wastewater, mud organic waste such as livestock manure, or various organic materials such as garbage, pruned branches, fishery and agricultural waste When anaerobic waste is anaerobically treated, it is necessary to improve the recovery of methane gas, reduce the volume of excess sludge generated by anaerobic treatment, and improve the treatment efficiency and heating in the solubilization process. The amount of heat can be reduced, and methane gas can be efficiently recovered from organic waste and effectively used as fuel gas.

Systematic diagram of organic waste anaerobic treatment method of one embodiment of the present invention (Example 1) System diagram of an organic waste anaerobic treatment method of another embodiment of the present invention (Example 2) System diagram of conventional anaerobic treatment method for organic waste

Explanation of symbols

1: First solubilization tank (first solubilization step)
2: Second solubilization tank (second solubilization step)
3: UASB device (anaerobic treatment process)
4: First heat exchanger (first heat exchange process)
5: Second heat exchanger (second heat exchange step)
6: First solid-liquid separation device (first solid-liquid separation step)
7: Second solid-liquid separation device (second solid-liquid separation step)
8: Crushing device (waste crushing process)

Claims (4)

In the method of anaerobically treating organic waste, at least the following steps are provided.
(A) a first solubilization step of solubilizing sludge-like organic waste in a temperature range of 100 to 150 ° C;
(B) a first solid-liquid separation step for solid-liquid separation of the solubilized sludge solubilized in the first solubilization step;
(C) a second solubilization step of solubilizing the separated sludge separated in the first solid-liquid separation step in a temperature range of 160 to 230 ° C;
(D) a second solid-liquid separation step for solid-liquid separation of the solubilized sludge solubilized in the second solubilization step;
(E) an anaerobic treatment step for anaerobically treating the separated liquid separated in the first solid-liquid separation step and the second solid-liquid separation step; In the method of anaerobically treating organic waste, at least the following steps are provided.
(A) a first solubilization step of solubilizing sludge-like organic waste in a temperature range of 100 to 150 ° C;
(B) a first solid-liquid separation step for solid-liquid separation of the solubilized sludge solubilized in the first solubilization step;
(C) a waste crushing step in which solid organic waste is crushed and sludged;
(D) a second solubilization step of solubilizing the separated sludge separated in the first solid-liquid separation step and the crushed waste crushed in the waste crushing step in a temperature range of 160 to 230 ° C;
(E) a second solid-liquid separation step for solid-liquid separation of the solubilized sludge solubilized in the second solubilization step;
(F) Anaerobic treatment step for anaerobically treating the separated liquid separated in the first solid-liquid separation step and the second solid-liquid separation step   Crushed by the sludge-like organic waste to be supplied to the first solubilization process and the separated sludge to be supplied to the second solubilization process or waste crushing process to exchange heat between the solubilized sludge and the second solubilization process The processing method of the organic waste of Claim 1 or Claim 2 which provided the 2nd heat exchange process which heat-exchanges waste and solubilized sludge, respectively. The anaerobic treatment process allows the liquid to be treated to flow upward through the self-granulating sludge bed of microorganisms formed in the anaerobic treatment tank, and decomposes the organic matter in the liquid to be treated by the biological action of the microorganisms. 4. The method for treating organic waste according to claim 1, wherein the organic waste is a counter-current anaerobic treatment step.