JPH11290827A - Method for heating organic waste in fermentation tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heat organic waste of a specified TS concentration in a fermentation tank containing fermenting microorganisms uniformly by a method in which the waste is agitated by circulating over a circulating channel installed outside the tank and heated by frictional heat generated by the agitation. SOLUTION: In an anaerobic fermentation tank 1 for methane fermenting organic waste (sludge) 9, a digestion gas discharge pipe 2 is opened in the ceiling part, and a digested sludge discharge pipe 3 is opened in the bottom part. A sludge circulating pipe 4 is installed outside the tank 1, and a circulation pump device 5 is fitted to the circulating pipe 4. A thermometer such as a thermocouple 7 is fitted to the outlet side of the pump device 5, and the rotational speed of the device 5 is controlled by a controller 8 on the basis of temperature data from the thermo-couple 7. The TS concentration of sludge 9 in the tank 1 is adjusted at 1.5-7%, the sludge 9 is agitated uniformly by being circulated between the tank 1 and the circulating pipe 4 and heated uniformly by the frictional heat of the agitation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for heating organic waste in a fermenter for performing high-concentration fermentation.

[0002]

2. Description of the Related Art Conventionally, organic waste has been recycled. For example, Japanese Patent Application Laid-Open No. Hei 9-201699 discloses that human waste, septic tank sludge, sewage sludge, agricultural sludge, livestock manure, garbage and foods are disclosed. Organic waste with different properties and concentrations, such as waste, is treated in the same system to collect useful substances,
A method for recycling is disclosed.

This method is as shown in FIG. 3. In this method, human waste, septic tank sludge, agricultural sludge, sewage sludge, and livestock manure are removed in a removing step # 31, and a solid-liquid separation step # 3 is performed.
In 2, the liquid waste 31 and the dewatered sludge 32 are separated,
The liquid waste 31 is subjected to BOD decomposition and denitrification as necessary in the biological treatment step # 33, and suspended matter is removed in the solid-liquid separation step # 34. COD, pigment components, iron and manganese are removed in the advanced treatment step # 35. Heavy metals such as are removed and disinfected for effluent or reused water.

On the other hand, garbage and food waste are crushed in a crushing / separating step # 36, plastic bags and trays are separated, and then mixed with the above-mentioned dewatered sludge 32.
In the anaerobic fermentation step # 37, methane fermentation is performed, and the generated methane gas 33 is collected and used in the form of electricity or heat in the power generation step # 38 and the like, and the digested sludge 34 is converted into dehydrated sludge 35 in the dehydration step # 39. And sent to the composting process # 40, etc. to collect it as fertilizer, solid fuel or dry sludge.
3 to be processed.

[0005]

Generally, in order to ferment organic matter, it is necessary to prepare an environment suitable for the growth of microorganisms.
In addition, it is necessary to bring the microorganisms and the fermentation target into sufficient contact.For this purpose, the fermentation target is crushed, and in some cases, is solubilized and reduced in molecular weight by a method such as alkali, ozone, or heating. The fermenter is put into the fermenter, and is stirred and mixed by a gas stirring means such as a pump device and a blower, and the fermenter is heated by a warming device such as hot water or a heater so that the temperature does not decrease due to heat radiation or the like. .

In this regard, in the case of performing high-concentration fermentation as in the above-described anaerobic fermentation step # 37, the organic waste to be fermented has a high viscosity and requires a large amount of energy for stirring. The apparatus is not employed as inefficient and often employs gas agitation means.

However, when a heating device is provided outside the fermentation tank, such as by installing a heater along the outer periphery of the fermentation tank, a temperature gradient is generated unless stirring and mixing is performed with sufficient stirring power, and a temperature gradient near the heating apparatus is generated. Only organic waste raises the temperature and causes adhesion to the tank wall.

An object of the present invention is to solve the above-mentioned problem, and it is an object of the present invention to uniformly heat a high-concentration organic waste.

[0009]

In order to solve the above-mentioned problems, a method for heating organic waste in a fermenter according to claim 1 of the present invention provides a method for heating a TS concentration in a fermenter containing fermentation microorganisms. 1.5 to 7% of organic waste is stirred and mixed by being circulated by a circulation pump device through a circulation channel provided outside the tank in communication with the fermentation tank, and frictional heat generated by the stirring and mixing is generated. It is intended to be heated in.

According to a second aspect of the present invention, there is provided a method for heating organic waste in a fermenter, wherein the temperature of the organic waste on the discharge port side of the circulation pump device in the circulation flow path is measured, and the measured temperature value and a predetermined temperature are measured. And the amount of frictional heat generated is increased or decreased by inverter control of the circulating pump device based on the difference from the fermentation temperature, and the temperature of the organic waste in the fermenter is adjusted to the fermentation temperature.

According to a third aspect of the present invention, there is provided a method for heating organic waste in a fermenter, wherein the organic waste is supplied to a suction port side of a circulation pump device. As the circulating pump device, a cutter pump, a screw pump, or another type in which the impeller rotates in the flow path in the machine is used, and the organic waste can be stirred and mixed while being sheared by the impeller. This is preferable because it can be heated by frictional heat generated in the portion. Although the heating efficiency is lower than these, a type having no impeller such as a single-shaft screw pump can also be used.

According to the structure of the first aspect of the present invention, the circulation pump device for circulating the organic waste inside and outside the fermenter necessarily has a large capacity and exerts a strong circulation stirring force. In addition, sewage sludge and septic tank sludge with relatively low concentration, as well as high-viscosity garbage and livestock manure are also mixed and mixed, and the organic waste can be heated by the frictional heat at that time, and the solid content is reduced. The fermentation efficiency can be increased by solubilizing efficiently.

At this time, in order to stir and mix the organic waste almost uniformly, it is appropriate that the circulation amount is 3 to 5 times / h of the fermenter capacity, and the circulation amount is used to radiate heat from the fermenter. In order to obtain the calorific value of the organic waste (and the endothermic reaction component), it is appropriate that the organic waste has a TS concentration of 1.5 to 7%, so that a plurality of types of organic wastes having different properties are included in this range. The concentration of the organic waste is adjusted by mixing the waste, or solubilizing it to some extent as a pretreatment, or diluting with water.

At this time, it is necessary to set a predetermined fermentation temperature suitable for the growth of microorganisms, and to adjust the temperature of the organic waste in the tank to the fermentation temperature.
According to the configuration described above, the temperature of the organic waste on the discharge port side that returns to the inside of the tank is fed back to the circulation pump device so as to increase or decrease the amount of frictional heat. Can be easily adjusted.

According to the third aspect of the present invention, the organic waste is charged into the suction port side of the circulation pump device so that the charged organic waste is mixed with the organic waste in the circulation channel. Then, it can be sufficiently brought into contact with microorganisms contained therein and quickly heated, and solubilization of solids can be promoted to increase fermentation efficiency.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, an anaerobic fermenter 1 for methane fermenting organic waste (hereinafter referred to as sludge) has a heat insulating structure, a digestion gas extraction pipe 2 is opened to the top, and a digestion sludge extraction pipe 3 is provided. Open to the bottom.

Outside the fermenter 1, a sludge circulation pipe 4 communicating with a lower part inside the tank and an upper part inside the tank is provided, and a circulation pump device 5 having an impeller is interposed in the sludge circulation pipe 4. At the same time, a sludge supply pipe 6 is opened on the suction port side of the circulation pump device 5. At the upper end of the sludge circulation pipe 4, a nozzle 4a opened toward the sludge surface in the tank is attached.

A thermometer such as a thermocouple 7 for measuring the temperature of the sludge in the sludge circulation pipe 4 is provided on the discharge port side of the circulation pump device 5 in the sludge circulation pipe 4. And a control device 8 for controlling the rotation speed of the circulation pump device 5 based on the temperature data from the thermocouple 7.

The operation of the above configuration will be described. The sludge 9 containing methane bacteria and the like inside the fermenter 1 is adjusted to a TS concentration of 1.5 to 7%, and is continuously connected to the inside of the fermenter 1 and the sludge circulation pipe 4 by the circulation pump device 5. Circulates uniformly, whereby the mixture is homogeneously stirred and mixed, and is uniformly heated by frictional heat at that time.

In this state, when raw sludge is fed into the sludge circulation pipe 4 through the sludge supply pipe 6, the fed raw sludge is taken into the internal flow path of the circulation pump device 5 and sheared by the impeller. While being mixed with the sludge 9 in the flow path, the mixture is sufficiently brought into contact with the microorganisms contained therein, and the temperature is quickly raised due to frictional heat generated particularly at the impeller.

The temperature of the sludge 9 mixed with the raw sludge is measured by the thermocouple 7 at the discharge port side of the circulation pump device 5, and the measured temperature value is sent to the control device 8. Predetermined fermentation temperature 37 ° C suitable for growth of methane bacteria, etc.
When the temperature is lower than (or 55 ° C.), the rotation speed of the circulation pump device 5 is increased by the control device 8 to increase the generation of frictional heat. When the temperature is higher than a predetermined fermentation temperature, the rotation of the circulation pump device 5 is controlled by the control device 8. The number is reduced, and the generation of frictional heat is reduced, whereby the sludge 9 which has reached almost the fermentation temperature returns to the inside of the fermenter 1. At this time, the sludge 9 is ejected into the tank through the nozzle 4a, whereby the scum formed on the sludge surface in the tank is destroyed.

Thus, the sludge 9 in the fermenter 1 is
The mixture is homogeneously stirred and mixed, and comes into sufficient contact with the microorganisms, and is evenly heated to a predetermined fermentation temperature. By crushing the scum, the stirring and mixing effect is not hindered, and an increase in the organic acid concentration may be prevented. , Solubilize it efficiently and perform methane fermentation to generate a large amount of digestive gas rich in methane. The generated digestive gas passes through the digestive gas extraction pipe 2,
The digested sludge is collected through the digested sludge discharge pipe 3.

As described above, in the fermenter having a capacity of 20 m ³ , the sludge having a TS concentration of 3 to 4% is supplied to the cutter pump (1 m ³ / min = 3 times / h, the amount of circulation, and the pump power is 5.5 k).
(W, pump efficiency 25%), the Joule heat generated when circulating is calculated as follows.

5.5 kW × ((100−25) / 100) ×
860 kcal / kWh × 24 h / d = 85140 kcal / d This calorific value matches the heat release and endothermic reaction (actually measured values) of the following fermenter.

20 m ³ × 4 ° C./d=80,000 kcal / d From the above, it can be seen that by circulating the organic waste as described above, the heat radiation and the endothermic reaction in the reaction tank can be compensated.

However, when the power for generating the required amount of heat cannot be used, an external heating device such as hot water is used in combination. Conversely, when the sludge temperature rises excessively and it becomes necessary to reduce the circulation amount to, for example, 1/10, the operation time is reduced to 1/10 while maintaining the circulation flow rate (that is, intermittent operation is performed).
By doing so, the stirring effect can be ensured.

As described above, the use of the circulating pump device, which has been conventionally difficult to adopt because of large energy loss, allows the sludge in the fermenter to be homogeneously stirred and mixed to sufficiently contact microorganisms, and Temperature and fermentation temperature, organic components such as methane gas can be recovered at a high rate. Objects can be prevented from adhering to the tank wall.

As shown in FIG. 2, the same effect can be obtained even if the circulating pump device 5 is located inside the fermenter 1. When organic wastes such as food waste and food waste are subjected to methane fermentation, mixing with foreign organic wastes such as human waste and sewage sludge will increase the methane recovery rate. It is preferable to roughly crush with a coarse crusher such as a crusher and then compress and crush with a compression crusher at a high pressure of 200 to 250 kg / cm ² .

According to this method, the organic wastes and the plastics accompanying the organic wastes have a particle diameter of 20 to 20 in a uniaxial crusher.
After being coarsely crushed to 100 mm or less, the crushed material is compressed and crushed by a compression crusher at a high pressure, and has a particle size of 1 corresponding to the diameter of the crushing discharge hole.
Fine particle crushed material of ~ 2 mm or less, and non-crushable residue
It is automatically classified as unsuitable for fermentation such as plastics, metals, stones and sand.

Since the separated crushed material is finely divided and the cell membrane is partially destroyed, the biodegradability of the crushed material becomes extremely large. In addition, the organic waste that has been removed by being adhered to the unsuitable fermentation material may be included in the crushed material, and the recovery rate of organic components such as methane gas becomes extremely high.

A part of the digested sludge is concentrated by a dehydrator or a filtration membrane disposed inside and outside the tank and returned (residual) to the fermentation tank to increase the concentration of methane bacteria, and to remove human waste and sewage sludge. If fermentation difficult organic waste is solubilized, for example, by maintaining it at about 70 to 80 ° C. for 3 days, the fermentation efficiency is further increased.

In the above description, an anaerobic fermenter for performing methane fermentation has been described as an example. However, organic waste can be advantageously heated similarly in other fermenters.

[0033]

As described above, according to the present invention, the organic waste in the fermenter can be heated uniformly while stirring and mixing homogeneously only by the circulation pump device. Organic components such as methane gas can be recovered.

The temperature of the organic waste in the fermenter can be easily adjusted by inverter control of the circulation pump device. By injecting the organic waste into the vicinity of the suction port of the circulation pump device, the injected organic waste is brought into sufficient contact with the microorganisms contained in the organic waste in the circulation flow path, and quickly. It can be heated and can promote solubilization and fermentation of the input organic waste.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an anaerobic fermenter in which a method for heating organic waste according to a first embodiment of the present invention is performed.

FIG. 2 is an explanatory diagram showing a schematic configuration of an anaerobic fermenter in which an organic waste heating method according to a second embodiment of the present invention is performed.

FIG. 3 is a flowchart showing a conventional organic waste treatment flow.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fermenter 4 Sludge circulation pipe 5 Circulation pump device 6 Sludge supply pipe 7 Thermocouple 8 Control device 9 Sludge (organic waste)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiyuki Shibata 2-47, Shishitsuhigashi 1-chome, Naniwa-ku, Osaka-shi, Osaka (72) Inventor Yoshiharu Fujii 4-11 Minamisenba, Chuo-ku, Osaka-shi, Osaka −20 Kubota Environmental Service Co., Ltd.

Claims (3)

[Claims] An organic waste containing a fermentation microorganism and having a TS concentration of 1.5 to 7% in a fermentation tank is circulated by a circulation pump device through a circulation flow path provided outside the tank in communication with the fermentation tank. A method of heating organic waste in a fermenter, wherein the mixture is stirred and mixed, and heated by frictional heat generated by the stirring and mixing. 2. The temperature of organic waste on the discharge port side of the circulation pump device in the circulation flow path is measured, and the circulation pump device is subjected to inverter control based on the difference between the measured temperature value and a predetermined fermentation temperature, and friction is measured. The method for heating organic waste in a fermenter according to claim 1, wherein the amount of heat generated is increased or decreased to adjust the temperature of the organic waste in the fermenter to the fermentation temperature. 3. The method for heating organic waste in a fermenter according to claim 1, wherein the organic waste is introduced into the suction port side of the circulation pump device.