JP2010036161A - Organic waste treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic waste treatment method which can efficiently decompose organic matter, and also does not produce waste water required to be treated. <P>SOLUTION: The organic waste treatment method comprises: a methane fermentation step (a) where organic matter contained in organic waste is subjected to dry type methane fermentation and a solubilization step (b) where the organic matter contained in the organic waste is made low in molecular weight, wherein the waste water is not produced, and the removal amount of aqueous ammonia in the solubilization step (b) is controlled in such a manner that the dry type methane fermentation is made possible in the methane fermentation step (a). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an efficient method for treating organic waste.

  From the viewpoint of the importance of global environmental conservation and energy saving, organic waste discharged from food factories, etc., organic waste discharged from hotels, restaurants, general households, livestock waste, sewage Technology development to recover sludge and other organic waste as methane gas by methane fermentation is being promoted. In order to collect as much methane as possible from organic matter and reduce the amount of final waste, the organic matter decomposition rate is improved. A method has been developed.

  For example, as a method for efficiently performing methane fermentation on organic waste, a method for subjecting organic waste to various pretreatments prior to methane fermentation has been proposed. For example, as a pretreatment for methane fermentation, a method of heat-treating organic waste (see Patent Document 1), a method of decomposing organic waste with an ultrahigh-heat anaerobic bacterium (see Patent Document 2), or under high temperature A method of decomposing organic substances contained in organic waste with methane fermentation sludge (Patent Document 3) is known.

  However, in the methane fermentation of wastes in the prior art, it is essential to treat the water contained in the wastes, and there are problems of water treatment facilities and large power costs.

Today, there is concern about the depletion of natural energy and the limit of waste treatment capacity, and it is strongly desired to put into practical use technology for effective use of energy and reduction of waste. For this reason, it is important to develop a technology for reducing the amount of wastewater in the treatment of organic waste, more efficiently recovering energy from the organic waste, and reducing the amount of waste.
JP 58-41916 A JP 2003-326237 A JP 2006-15331 A

  The present invention has been made in response to such conventional circumstances and recent trends, and an object of the present invention is to provide a method for treating organic waste that can efficiently decompose organic matter and does not generate wastewater that requires treatment. And

  In order to solve the above problems, the present inventors have conducted research, and in the organic waste treatment method including the methane fermentation process and the solubilization process, the water content of the organic waste provided in the methane fermentation process and It was found that organic waste can be treated without producing waste water by adjusting the amount of ammonia water recovered in the solubilization process. Based on this finding, the present inventors have completed the present invention by further research.

That is, the present invention is as follows.
Item 1. A method for treating organic waste, comprising:
Including a methane fermentation step (a) for dry methane fermentation of organic matter contained in organic waste and a solubilization step (b) for reducing the molecular weight of the organic matter,
(1) A required amount of fermentation processed product is extracted from the methane fermentation processed product obtained by the methane fermentation step (a), divided into a first processed product and a second processed product, and the first processed product is separated from the liquid by solid-liquid separation processing. Separating the residue and subjecting the mixture of the liquid and organic waste separated from the first treated product to the methane fermentation step (a) or the solubilization step (b),
(2) subjecting the solubilized product obtained in the solubilization step (b) to the methane fermentation step (a);
(3) subjecting the second treated product to the solubilization step (b);
(4) The solubilization step (b) is a step of heat-treating at 70 ° C. or higher and recovering ammonia water,
And
(5) controlling the amount of ammonia water recovered in the solubilization step (b) so that drainage does not occur and dry methane fermentation is possible in the methane fermentation step (a);
A processing method characterized by the above.
Item 2. A method for treating organic waste, comprising:
Including a methane fermentation step (a) for dry methane fermentation of organic matter contained in organic waste and a solubilization step (b) for reducing the molecular weight of the organic matter,
(1) A required amount of fermentation processed product is extracted from the methane fermentation processed product obtained by the methane fermentation step (a), divided into a first processed product and a second processed product, and the first processed product is separated from the liquid by solid-liquid separation processing. Subjecting the mixture of the liquid separated from the first treated product and the organic waste to the methane fermentation step (a),
(2) subjecting the solubilized product obtained in the solubilization step (b) to the methane fermentation step (a);
(3) subjecting the second treated product to the solubilization step (b);
(4) The solubilization step (b) is a step of heat-treating at 70 ° C. or higher and recovering ammonia water,
And
(5) controlling the amount of ammonia water recovered in the solubilization step (b) so that drainage does not occur and dry methane fermentation is possible in the methane fermentation step (a);
A processing method characterized by the above.
Item 3. Item 1. A method for treating organic waste, comprising:
Including a methane fermentation step (a) for dry methane fermentation of organic matter contained in organic waste and a solubilization step (b) for reducing the molecular weight of the organic matter,
(1) A required amount of fermentation processed product is extracted from the methane fermentation processed product obtained by the methane fermentation step (a), divided into a first processed product and a second processed product, and the first processed product is separated from the liquid by solid-liquid separation processing. Subjecting the mixture of the liquid and organic waste separated from the first treated product to the solubilization step (b),
(2) subjecting the solubilized product obtained in the solubilization step (b) to the methane fermentation step (a);
(3) subjecting the second treated product to the solubilization step (b);
(4) The solubilization step (b) is a step of heat-treating at 70 ° C. or higher and recovering ammonia water,
And
(5) controlling the amount of ammonia water recovered in the solubilization step (b) so that drainage does not occur and dry methane fermentation is possible in the methane fermentation step (a);
A processing method characterized by the above.
Item 4. Item 4. The method according to any one of Items 1 to 3, wherein the ratio of the processed methane fermentation product extracted in the methane fermentation step (a) is 1st processed product: 2nd processed product = 1: 1 to 4.
Item 5. Item 5. The method according to any one of Items 1 to 4, wherein the removal amount of the ammonia water in the solubilization step (b) is controlled by an ammonia stripping method.
Item 6. Item 6. The method according to any one of Items 1 to 5, wherein the organic waste to be fed has a moisture content of 60% or less.
Item 7. The amount of ammonia water collected to prevent drainage is given by the following formula:
W-1.5 × (1-p / 100) Q
(Wherein, Q is the solid weight of the input organic waste, W is the water content of the input organic waste, and p is the methane fermentation efficiency (%))
Item 7. The method according to any one of Items 1 to 6, which is represented by:

  According to the present invention, organic waste can be efficiently processed without discharging wastewater that needs to be processed. According to the treatment method of the present invention, it is not necessary to treat the water contained in the waste, so that no water treatment facility is required, and the power cost can be reduced. In addition, since the residue and aqueous ammonia recovered during the treatment in the treatment method of the present invention can be used as valuable materials such as an incinerator and a denitration liquid for an engine, no waste is generated, and Since the energy required for the treatment method of the present invention can be covered by waste heat generated when the biogas generated during the treatment is used for power generation, it is extremely useful both in terms of environment and cost.

Organic waste The organic waste treated by the method of the present invention is not particularly limited as long as it contains an organic matter, and examples thereof include those derived from animals or plants. Specifically, solid organic waste, semi-solid organic waste, organic waste containing organic matter as an insoluble solid, slurry-like organic waste [hereinafter referred to as “solid organic waste "In some cases. ] Etc. are illustrated. More specifically, examples include straw, raw garbage, dried food waste, food factory waste, sewage sludge, and livestock waste (a mixture of livestock excreta and straw, sawdust, etc.). The organic waste treated by the method of the present invention is a liquid containing organic matter as a soluble component such as concentrated waste liquid (sugar waste, shochu waste liquid, etc.), sewage and organic waste water (beer factory waste water, etc.). It may be a waste liquid having a high concentration of organic matter or a dilute waste liquid. However, since methane fermentation in the method of the present invention is dry methane fermentation, when the water content of organic waste is high, it is adjusted by pretreatment.

  The pH of these organic wastes varies depending on the type and is not particularly limited. Usually, in the case of garbage, the pH is about 5.

  In the method of the present invention, ammonia can be removed, so that organic waste having a high nitrogen content (for example, organic waste containing a lot of protein such as straw and garbage, preferably having a nitrogen content of 0.5% by weight). This is advantageous when processing organic wastes of the above degree.

Whether organic matter is being decomposed smoothly is indicated by changes in VTS (Volatile Total Solids) and VSS (Volatile Suspended Solid) amounts (VSS reduction rate) in each process. It can be judged as.
Hereinafter, the organic waste provided for the method of the present invention may be referred to as input organic waste.

Organic Waste Treatment Method The treatment method of the present invention includes a methane fermentation step (a) and a solubilization step (b) as described in detail below. Each of these steps may be performed first or in a batch format, but it is fermented or decomposed in the supply of input organic waste and in step (a) or step (b). By continuously or intermittently removing and transporting (returning) fermented and decomposed products, step (a) and step (b) are repeated continuously so that the entire system is in a steady state. It is preferable to do this. Thereby, the organic matter decomposition rate as a whole can be improved.

  Furthermore, as described in detail below, the present invention uses the dehydrated filtrate of the methane fermentation residue as raw material dilution water, and in the solubilization step (b), an ammonia recovery device is provided to eliminate wastewater that requires processing. It is characterized by that.

(1) Methane fermentation process (a)
In the methane fermentation step (a), the organic matter contained in the mixture of the organic waste and the liquid separated from the first treated product described later or the organic matter contained in the decomposition product obtained in the step (b) is methane and carbon dioxide. Is broken down into The methane fermentation in this step can be performed in an anaerobic atmosphere using a conventionally known methane fermentation bacterium and methane fermentation tank. Since the methane fermentation in the present invention is dry methane fermentation, the organic waste is introduced into the mixing tank in a nearly solid state with a total solid (TS) concentration of about 20 to 40% by weight, and is put into the fermentation tank. The solid methane sludge having a TS concentration of about 10 to 20% by mass (dry methane sludge) is retained.

  In this step (a), the preparation and maintenance of the anaerobic atmosphere can be performed using carbon dioxide, nitrogen, argon, hydrogen, natural gas, methane, city gas, and the like. Moreover, you may use oxygen removal agents, such as sodium sulfide, as needed.

  The temperature condition at the time of methane fermentation in this step (a) can be appropriately set from a wide temperature range depending on the type of methane fermentation bacteria to be used, and is not particularly limited, but is generally about 20 to 60 ° C. For example, a so-called intermediate temperature of about 35 ° C. or a so-called high temperature of about 55 ° C. may be used. Preferably, it carries out at 50-55 degreeC from a viewpoint of heat exchange with a solubilization tank.

  When the decomposition product obtained in the step (b) described below maintains a high temperature of 80 ° C. or higher, the decomposition product does not significantly adversely affect methane fermentation (for example, 60 ° C. or less). After cooling, it is desirable to supply this to a methane fermenter and to implement this process (a).

  The methane fermentation treatment time in this step (a) varies depending on the type and amount of the degradation product to be provided, the type of methane fermentation bacteria to be used, the fermentation temperature, the fermentation form, etc. 30 days, preferably 10 to 20 days, more preferably 10 to 14 days.

  A necessary amount (appropriate amount) of the fermentation treatment product is extracted from the methane fermentation treatment product generated in the methane fermentation of the present step (a), and is divided into a first treatment product and a second treatment product. The amount to be extracted can be appropriately determined according to various conditions such as the amount of organic waste to be input.

  The first processed product is separated into a liquid and a solid residue by a known solid-liquid separation process. The method of solid-liquid separation is not particularly limited, and known methods such as precipitation separation, membrane separation, and centrifugation can be employed.

  The separated solid residue is treated in various ways. For example, as it is, processing such as compost reduction, composting, composting, agricultural land reduction, disposal, incineration, or the like is performed. In addition, low-temperature waste heat can be effectively used for drying. When the generated methane gas is used in a gas engine, a micro gas turbine, a boiler, or the like, the waste heat can be used for drying.

  Further, the separated liquid is mixed with the input organic waste as a dehydrated filtrate, and is supplied again to the step (a). The amount of this liquid is appropriately determined depending on the water content of the organic waste to be charged, etc. If there is a surplus, the surplus liquid may be transferred to the solubilization step (b) as it is.

  Next, a 2nd processed material is sent to a process (b), and is provided to the following solubilization processes (b).

  By these operations, the solid content is further thoroughly decomposed and the liquid content is efficiently recycled, so that the amount of waste can be further reduced and the amount of methane gas generated can be increased. Is returned to the system, so that the merit of improving the stability of methane fermentation can be obtained.

  The ratio of the above two processed methane fermentation products can be appropriately determined by comprehensively judging the water content of the input organic waste so that wastewater treatment is unnecessary, as will be described later. As a form, it adjusts so that it may become 1st processed material: 2nd processed material = 1: 1-4, for example.

  The methane gas generated in this step (a) can be generated and recovered as exhaust heat energy, and can be used for temperature adjustment in step (b) described later, but it can be used for the ammonia recovery step in step (b). Most preferred.

  The form of methane fermentation in this step (a) is not particularly limited, and may be any known form used in methane fermentation such as a batch type or a fixed bed type.

(2) Solubilization step (b)
In the solubilization process, heat treatment is performed under a temperature condition of 70 ° C. or higher, and the organic matter contained in the organic waste is decomposed by methane fermentation sludge.

  By this step, the organic matter contained in the organic waste is decomposed and solubilized and liquefied. The methane bacteria contained in the methane fermentation sludge cannot grow at 60 ° C. or higher, but there are bacteria that can grow at 60 or more in addition to the methane bacteria in the methane fermentation sludge. In this process, the methane fermentation sludge is a function of bacteria (hereinafter sometimes referred to as solubilized bacteria) that can reduce high molecular organic substances in bacteria that can grow at 60 ° C or higher contained in methane fermentation sludge. Organic substances (carbohydrates, proteins, lipids) that have increased solubility under high-temperature conditions due to the action of enzymes contained in are reduced in molecular weight (for example, sugars, amino acids, peptides, etc.), and some or most of them It seems that organic acids such as propionic acid and butyric acid have been decomposed by acid decomposition, but the details have not been fully elucidated.

  The `` decomposition '' in this step (b) is not limited to low molecular weight to the extent that all organic waste is solubilized, and insolubilized organic matter contained in organic waste is preferable. Means that an insolubilized organic substance of about 20% by weight or more, more preferably about 25% by weight or more is reduced in molecular weight to such an extent that it can be dissolved in water.

  The methane fermentation sludge used in this step (b) is a fermented product obtained by subjecting an organic material to methane fermentation, or a solid content of the fermented product. As the methane fermentation sludge, for example, a methane fermentation processed product (the second processed product) obtained in the methane fermentation step (a) can be used. Moreover, when using the fermented material itself obtained by carrying out methane fermentation of organic substance as methane fermentation sludge, what contains solid content 0.1weight% or more, Preferably 1weight% or more is desirable. In addition, solid content here contains the insolubilization residue in fermented material obtained by methane fermentation, and bacteria, such as methane bacteria and solubilized bacteria.

  In the decomposition by methane fermentation sludge in this step, the temperature condition is not particularly limited as long as the temperature condition is 70 ° C. or higher, but is preferably about 70 to 90 ° C., more preferably about 75 to 85 ° C., and particularly preferably about 80 to 85 ° C. It is. In this step, heavy oil, city gas, electric power, or the like can be used to maintain a predetermined temperature of 70 ° C. or higher. However, since a considerable amount of heat is required to maintain the temperature, heat and power are obtained by using the methane gas generated in the above-mentioned step (a) rather than using heavy oil alone as a power source. It is desirable to make effective use of the generated exhaust heat by using cogeneration means (gas engine, fuel cell, etc.).

  Decomposition of organic matter contained in organic waste by methane fermentation sludge allows organic waste and methane fermentation sludge to coexist in a tank capable of adjusting and maintaining the above temperature conditions (hereinafter referred to as high temperature solubilization tank). It can be performed by holding under conditions.

In order for the organic waste and the methane fermentation sludge to coexist in the high-temperature solubilization tank, for example, the following methods are exemplified: (1) Supply the organic waste to the high-temperature solubilization tank, and separate methane A method of supplying fermented sludge to a high-temperature solubilization tank and mixing organic waste and methane fermentation sludge in the high-temperature solubilization tank, and (2) supplying organic waste to a mixing tank equipped with a mixing means The methane fermentation sludge is supplied to the mixing tank, both are mixed in advance in the mixing tank, and the resulting organic waste / sludge mixture is supplied to the high-temperature solubilization tank. In the case of the latter method (2), by setting the solid content concentration of the organic waste / sludge mixture to 10% by weight or less, the mixture can be supplied to the high-temperature solubilization tank by a small and inexpensive pump. become. In the case of the latter method (2), specifically, this step (b) includes the steps of the following embodiments:
(B-1) Supplying organic waste to the mixing tank
(B-2) supplying methane fermentation sludge to the mixing tank;
(B-3) mixing organic waste and methane fermentation sludge in a mixing tank;
(B-4) supplying the organic waste / sludge mixture obtained in step (B-3) to a high-temperature solubilization tank; and
(B-5) A step of decomposing organic substances contained in organic waste at a temperature of 70 ° C. or higher in a high-temperature solubilization tank.

  The decomposition by methane fermentation sludge in this step (b) can be carried out by allowing the organic waste and methane fermentation sludge to coexist and standing under the above conditions. Can also be carried out with stirring under the above conditions.

  In the decomposition with methane fermentation sludge in this step (b), the ratio of methane fermentation sludge to be used and organic waste to be used in this step depends on the type of methane fermentation sludge and organic waste to be used, decomposition conditions, etc. It can be set accordingly. As an example of these mixing ratios, a ratio of 0.1 to 10 parts by weight of methane fermentation sludge (in terms of solids) is exemplified with respect to 1 part by weight of solids contained in the organic waste.

  The decomposition time by methane fermentation sludge varies depending on the type and amount of methane fermentation sludge to be used and the type and amount of organic waste to be treated and cannot be defined uniformly, but is usually 1 to 10 days, preferably 1 to Examples are 5 days, more preferably 1-2 days.

  Decomposition by the methane fermentation sludge in this step may be performed in either an anaerobic atmosphere or an aerobic atmosphere.

  If this step (b) is performed in an anaerobic atmosphere, gas is generated along with decomposition (solubilization) of the organic matter contained in the organic waste, thereby purging oxygen in the high-temperature solubilization tank. Since the atmosphere is kept anaerobic, a special operation for creating and maintaining the anaerobic atmosphere is not necessarily required. Of course, you may create / maintain anaerobic atmosphere using carbon dioxide, nitrogen, argon, hydrogen, natural gas, methane, city gas, etc., and create anaerobic atmosphere using oxygen remover such as sodium sulfide.・ It may be maintained.

  Furthermore, in this step (b), ammonia and methane fermentation sludge contained in the organic waste are adjusted so that the total amount of water supplied to the methane fermentation step (a) becomes an amount capable of dry methane fermentation. The amount of ammonia recovered by the decomposition by the above is controlled to adjust the water content of the solubilized product.

  It is known that the activity of methane bacteria is inhibited by a high concentration of free ammonia nitrogen, and when the ammonium concentration in methane sludge increases, the methane fermentation activity is significantly inhibited and methane fermentation is stopped. For this reason, in the methane fermentation treatment of organic waste, it is essential to remove ammonia, and it is also necessary to remove unnecessary waste water generated during the treatment outside the system. Therefore, if these are combined and recovered as ammonia water in this step, the ammonia water can be used as a valuable material and unnecessary water is not discharged, which is very efficient.

  In this step (b), since the temperature condition of 70 ° C. or higher is adopted, the ammonia contained in the organic waste and the ammonia generated by the decomposition by the methane fermentation sludge are remarkably easily volatilized (Journal of Hazardous Materials 37 (1994) 191-206). Therefore, in step (b), gas can be blown into the high-temperature solubilization tank, and ammonia can be volatilized and recovered by the ammonia stripping method. The amount of ammonia water to be recovered can be adjusted by adjusting the amount of aeration air in the ammonia stripping device.

For example, 800L of methane fermentation sludge is put into a 1m ³ resinous tank, the temperature is kept at 80 ° C, and stripping gas (anaerobic gas) is blown from the bottom of the tank with an aeration rate of 7.5m ³ / min. Is evaporated, the ammonia concentration in the ammonia stripping gas is 8000 ppm, the moisture is 38%, and the recovered ammonia water amount is 100 L / day.

  Here, a specific embodiment will be described with respect to the amount of ammonia water recovered and the water content of the input organic waste when wastewater treatment is unnecessary.

  The amount of biogas generated when the solid weight of the input organic waste is expressed in Q (tons), the water content in W (tons), and the solid methane fermentation efficiency (biogasification efficiency) (%) as p. Is p / 100 * Q (tons), and the dry weight of the residue is (1-p / 100) Q (tons). Since the fermentation residue is usually transported off-site at a moisture content of about 60%, the amount of water in the fermentation residue is (1-p / 100) Q (1 / 0.4-1) (tons). For this reason, the amount of ammonia water that needs to be recovered in order not to generate wastewater is W-1.5 × (1-p / 100) × Q (tons).

  Here, if p is a general methane fermentation efficiency (80%), the amount of ammonia water that needs to be recovered in order not to generate wastewater is W-0.3Q (tons).

Next, if the temperature of the methane fermentation sludge is 50 ° C, the amount of heat required for ammonia recovery in the ultra-high temperature solubilization tank is
(W-0.3Q) x (50 + 540) / 760 (MWh) (Formula (I))
Can be expressed as

On the other hand, when recovering energy by generating 0.8Q (tons) of biogas generated in this process, the amount of heat that can be recovered as exhaust heat (steam) is
0.8Q x 0.2 (recovery efficiency) x 6.1 (heat quantity per ton of biogas) (MWh) (formula (II))
It becomes.

In order to recover ammonia water so that wastewater treatment is unnecessary using only the waste heat generated in this process, since formula (II)> formula (I),
0.8Q × 02 × 6.1> (W-0.3Q) × [(50 + 540) / 760]
That is, Q / W> 0.63 (formula (III)).

  Since the water content of the input waste is 1 / (1 + Q / W), the water content <61.3% is calculated by substituting Equation (III). For this reason, the dry methane fermentation system that does not require wastewater treatment has a moisture content of 60% or less, and of course it is assumed that no dilution water is used.

  If the amount of ammonia water is adjusted so as to satisfy the above conditions, organic waste can be efficiently treated without producing wasteful discharge or drainage.

  Since the organic matter contained in the organic waste is reduced in molecular weight by this step (b), when the obtained decomposition product is subjected to the methane fermentation treatment, the treatment efficiency is improved.

  The solid organic waste provided in this step (b) is decomposed and solubilized by the decomposition of the organic matter contained in the solid organic waste, so the decomposition product obtained in this step (b) It becomes possible to use for methane fermentation treatment as it is. This solves the problem that organic matter is not sufficiently treated by methane fermentation when the solid organic waste is directly subjected to methane fermentation treatment.

  The decomposition product obtained in this step (b) may be used as it is for the above-mentioned step (a), or may be used for the step (a) in the mixing tank or after being mixed with the input organic waste. .

(3) Transport / supply / discharge process In the case where the methane fermentation step (a) is performed first, the method of the present invention includes adding the organic waste, the liquid separated from the first treated product, and the solubilized product obtained by the solubilizing step (b) to methane. In order to use for fermentation process (a), the process of supplying these to methane fermentation process (a) is included. The supply means may use a conventionally known pump, or may be another means.

  Moreover, the method of this invention includes the process of discharging | emitting the methane fermentation processed material produced | generated in the methane fermentation process (a), and also including the process of collect | recovering the methane gas produced | generated in the methane fermentation process (a). Of the methane fermentation processed product discharged here, the first processed product is subjected to solid-liquid separation processing, the solid is used as compost, etc., and the liquid is conveyed to a mixing tank upstream of the methane fermentation processing tank. After being mixed with the input organic waste, it is again subjected to the methane fermentation process. Since a 2nd processed material is used for a solubilization process, it is conveyed to a high temperature solubilization tank. The amount and ratio of each methane fermentation processed product to be transported is the amount of input organic waste that eliminates the need for wastewater treatment, as described above, considering the processing conditions in steps (a) and (b). What is necessary is just to determine suitably, comprehensively judging moisture content.

  Further, the recovered methane gas is generated and recovered as energy, and can be used for temperature control in the method of the present invention.

2. When the solubilization step (b) is performed first, the method of the present invention is separated from the input organic waste and the methane fermentation treatment product (second treatment product) obtained in step (a) and the first treatment product. In order to use the obtained liquid for the solubilization step (b), a step of supplying them to the step (b) is included. The supply means may use a conventionally known pump, or may be another means.

  Furthermore, when using the second treated product obtained in step (a) as methane fermentation sludge in step (b), the method of the present invention is a step of solubilizing the second treated product obtained in step (a). (b) or a step of conveying it upstream. When transported, the methane fermentation treatment product may be transported directly to the high-temperature solubilization tank for carrying out step (b), and when a mixing tank is provided upstream of the high-temperature solubilization tank, it is transported to the mixing tank. May be. As described above, the amount and ratio of the methane fermentation processed product to be returned in the transporting process may be appropriately determined by comprehensively judging the water content of the input organic waste that does not require wastewater treatment.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples.
Example 1
Artificial garbage was prepared according to the following conditions and methods, and a treatment experiment of the garbage was performed.
<Making artificial garbage>
Cut the following materials into 5mm squares and stir each material well. Weigh so that all types are included at the specified rate in one crushing operation, and crush and mix using a food cutter (10000 rpm, 5 min.). Measure the moisture content and determine the TS (solid weight) (if storing, go to Deep Freezer).

・ Fruits (30%) Apple 2.5%
Orange (skin) 7.5%
Banana (skin) 10%
・ Vegetables (36%) Cabbage 10%
Potato 10%
Carrot 10%
Radish 10%
Chinese cabbage 10%
・ Meat (14%) Minced meat 2.5%
・ Seafood Fish 3.5%
Bone 1.5%
・ Eggs Egg 2.5%
・ Remaining rice (20%) Rice 10%
Bread 2.5%
Noodles 7.5%
The unit “%” is “% by weight”.

<Organic substance processing method>
80 g of dehydrated filtrate was added to 100 g of raw garbage (TS 40%) to make TS 22%, and it was put into a dry methane fermentation apparatus (fermentor volume 3.6 L, operating temperature 55 ° C.) every day.
140 g per day is withdrawn from the methane fermentation tank and transported to an ultra-high temperature solubilization tank (solubilization tank volume 0.09 L, operating temperature 80 ° C.), solubilizing methane fermentation sludge and 3 L / day of gas Ammonia stripping was performed at a flow rate, and the ammonia concentration in the ultra-high temperature solubilization tank was 1500 mg / L. By this operation, 32 g of ammonia water (ammonia concentration 0.5%) could be recovered. The remaining 108 g of lysate was returned to the methane fermenter.

<Result>
Since the biogasification efficiency was improved by the ultra-high temperature solubilization treatment, 40 g of biogas was generated per day from the methane fermentation tank, and 108 g of methane fermentation waste liquid was generated. When this was solid-liquid separated by dehydration, 28 g of fermentation residue (compost) with a water content of 40% was generated and 80 ml of dehydrated filtrate was generated. Did not occur.

  As described above, according to the method of the present invention, wastewater that needs to be treated is not generated by adjusting the amount of ammonia water to be recovered, and it is necessary to recover ammonia water only by waste heat energy from biogas generated during the process. It has been shown that it is possible to provide energy.

Comparative Example 1
Diluted water 80 ml was added to 100 g of raw garbage (TS 40%) to make TS 22%, which was added to a dry methane fermentation apparatus (fermentor volume 3.6 L, operating temperature 55 ° C.) every day.
140 g per day was withdrawn from the methane fermentation tank and transferred to an ultra-high temperature solubilization tank (solubilization tank volume 0.09 L, operating temperature 80 ° C.) to solubilize methane fermentation sludge. Thereafter, the same amount (140 g) of the solubilized liquid was returned to the methane fermentation tank.

  As a result, 40 g of biogas was generated per day, and 147 g of methane fermentation processed product was generated. When this was dehydrated, 28 g of fermentation residue (compost) with a moisture content of 40% was generated and 112 g of waste water was generated.

Reference example 1
Based on the above-described embodiment, assuming an implementation on an actual scale, it is as follows.
100 t of raw garbage per day (TS 40%) is added to 80 m ³ of dehydrated filtrate in the same manner as in the example to make TS 22%, and put into a dry methane fermentation apparatus (55 ° C.).
140t per day is withdrawn from the methane fermentation tank and transported to an ultra-high temperature solubilization tank (solubilization tank volume 90 m ³ , operating temperature 80 ° C.) to solubilize methane fermentation sludge and 3000 m ³ / day of gas Ammonia stripping is performed at a flow rate so that the ammonia concentration in the ultra-high temperature solubilization tank is 1500 mg / L. By this operation, 32t of ammonia water (ammonia concentration 0.5%) can be recovered. The remaining 108 t of solubilized liquid is returned to the methane fermenter.

As a result, 40 t of biogas is generated per day from the methane fermentation tank, and 108 t of methane fermentation waste liquid is generated. When this is solid-liquid separated by dehydration, 28 tons of fermentation residue (compost) with a water content of 40% is generated and 80 m ³ of dehydrated filtrate is generated. There will be no drainage.

FIG. 1 is a schematic diagram of an embodiment. FIG. 2 is a schematic diagram of a comparative example.

Claims (5)

A method for treating organic waste, comprising:
Including a methane fermentation step (a) for dry methane fermentation of organic matter contained in organic waste and a solubilization step (b) for reducing the molecular weight of the organic matter,
(1) A required amount of fermentation processed product is extracted from the methane fermentation processed product obtained by the methane fermentation step (a), divided into a first processed product and a second processed product, and the first processed product is separated from the liquid by solid-liquid separation processing. Separating the residue and subjecting the mixture of the liquid and organic waste separated from the first treated product to the methane fermentation step (a) or the solubilization step (b),
(2) subjecting the solubilized product obtained in the solubilization step (b) to the methane fermentation step (a);
(3) subjecting the second treated product to the solubilization step (b);
(4) The solubilization step (b) is a step of heat-treating at 70 ° C. or higher and recovering ammonia water,
And
(5) controlling the amount of ammonia water recovered in the solubilization step (b) so that drainage does not occur and dry methane fermentation is possible in the methane fermentation step (a);
A processing method characterized by the above. The method according to claim 1, wherein a ratio of the methane fermentation processed product extracted in the methane fermentation step (a) is 1st processed product: 2nd processed product = 1: 1-4. The method according to claim 1 or 2, wherein the amount of ammonia water removed in the solubilization step (b) is controlled by an ammonia stripping method. The method according to any one of claims 1 to 3, wherein the water content of the organic waste to be input is 60% or less. The amount of ammonia water collected to prevent drainage is given by the following formula:
W-1.5 × (1-p / 100) Q
(Wherein, Q is the solid weight of the input organic waste, W is the water content of the input organic waste, and p is the methane fermentation efficiency (%))
The method in any one of Claims 1-4 represented by these.

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