JPH05317839A - Pretreatment for waste incineration utilyzing heat retained in exhaust gas - Google Patents

Abstract

PURPOSE:To enable the efficient incineration of waste contg. moisture at a high ratio by cooling feed air to a specific temp. under a reduced pressure and sublimating and removing the moisture in waste. CONSTITUTION:The pressure in a drying device 1 having an agitating means 3 is maintained under a reduced pressure and the waste having the high moisture content is charged into the device 1 and is agitated. The air fed therein is cooled down to -20 deg.C+ or -5 deg.C to sublimate and remove the frozen moisture. The reduced pressure is easily maintained in the drying device 1 by increasing the discharge quantity of the air than the feed quantity of the air into the device 1 in such a case. The cooling or heating of the air to be fed into the drying device is executed at a low running cost by an absorption type refrigerator operated by utilizing the heat retained in the exhaust gas of waste incineration or by a heat exchange with the exhaust gas. Then, the waste contg. the moisture at the high ratio is efficiently incinerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention efficiently incinerates wastes, particularly wastes containing a large amount of water generated from daily life of ordinary households and food and drink providing businesses such as restaurants. The present invention relates to a pretreatment method for waste incineration, which is a combination of drying, crushing, and separation.

[0002]

2. Description of the Related Art Generally, industrial wastes or wastes for daily life are disposed by coastal landfill or inland landfill and incineration. However, landfilling or the like tends to cause a problem of environmental pollution, or the treatment area becomes narrower with the passage of time, so that the treatment cannot be continued sometime.

In addition, in the case of incineration, not only expensive equipment and its operation require labor and expense, but also odors generated, harmful exhaust gas and smoke, and incineration ash treatment become problems depending on the location conditions. In order to completely incinerate a large amount of raw garbage, it is necessary to improve the capacity of the equipment, and it has been extremely difficult to carry out these economically.

The present inventor has previously proposed an invention relating to a technique for detoxifying the leachate from the incineration ash containing harmful heavy metals, which is generated during the treatment of general and industrial wastes (Japanese Patent Application No. Hei 3).
-96995). In addition, an invention was proposed in which the leaching wastewater containing harmful components generated in the waste treatment area is completely sealed in the area to help prevent pollution of the environment surrounding the treatment area (Japanese Patent Application No. 4-81178).

[0005]

A problem in the technique of the prior invention is how to incinerate waste efficiently and increase its economical efficiency. In particular, kitchen garbage in general households and cooking waste from cafeterias and restaurants often have a water content of up to 90%, so when using an ordinary incinerator, it is necessary to use a large amount of auxiliary fuel together. It was impossible to burn and was very uneconomical.

[0006] Prior to the incineration of waste, there has been proposed an apparatus for performing preliminary heating and drying at a temperature at which the object to be treated does not burn, by utilizing the heat of the waste incineration exhaust gas (Japanese Patent Laid-Open No. 62-62). -22907). However, the above-mentioned device cannot be used for incineration of domestic garbage generated in a large amount.

An object of the present invention is to solve the problems of the prior art and to provide a pretreatment method for efficiently incinerating a waste containing a large amount of water.

[0008]

In order to achieve the above object, the inventors of the present invention have conducted extensive studies and as a result, as a result of drying the pretreatment for waste to be incinerated, cooling under reduced pressure or heating under reduced pressure was performed. The inventors have found that it is effective and have completed the present invention. That is, the gist of the present invention is to maintain the internal pressure of the drying device equipped with a stirring means at a reduced pressure,
A pretreatment for waste incineration, which is characterized in that waste having a large water content is put into the apparatus and stirred, and the supplied air is cooled to −20 ° C. ± 5 ° C. to sublimate and dehydrate frozen water. In the method, or in place of the cooled feed air, the feed air is heated to 80 ° C. ± 10 ° C., and the water content is evaporated and dehydrated. It is in.

In the present invention, in order to maintain the internal pressure of the drying device at a reduced pressure, it is simple to carry out by increasing the amount of discharged air rather than the amount of air introduced into the device. Also,
The cooling or heating of the air sent to the drying device can be carried out at a low operating cost by using an absorption refrigerating machine operated by utilizing the heat retained by the waste incineration exhaust gas or by exchanging heat with the exhaust gas.

[0010]

The structure and operation of the present invention will be described. In the present invention,
Drying performed as a pretreatment for waste incineration is performed by cooling or heating under reduced pressure. As a means for decompressing the inside of the drying device, a general decompression device can be used, of course, but as shown in, for example, Japanese Patent Laid-Open No. 62-106279, the amount of air sent to the outside of the device is more than the amount of air sent into the device. By increasing the amount of discharged air, the inside can be kept under reduced pressure. The feed rate and the exhaust rate are controlled so that it is preferably 800 mmAq to 500 mmAq.

The temperature of the incoming air is reduced under the above-mentioned reduced pressure.
When cooled to 20 ℃ ± 5 ℃, the triple point (4.6T
At orr 0 ° C), the water in the waste freezes, sublimates, and the water in the waste decreases. As the refrigerator for cooling the air fed into the drying chamber, an endothermic type that uses the heat retained in the incinerator exhaust gas is used. In a 55 t / day waste incinerator, a refrigerator using generated exhaust gas can send cold air of -15 ° C with an air flow of 0.7 m ^{3 / s} .

When heating the blown air, a general-purpose heat exchanger is used to exchange heat with the exhaust gas from the incinerator, and hot air of 80 ° C. ± 10 ° C. is fed into the drying device. If the temperature is too high, the ignitable substance in the waste may ignite, and if it is too low,
Not fully dried. The water evaporated from the waste is discharged from the drying device together with the exhaust air, but in the case of raw garbage, it often gives off an offensive odor.

Therefore, if the exhaust gas from the drying device is discharged into the combustion chamber of the incinerator, the offensive odor component is decomposed by heating and does not affect the surrounding environment. Further, when the waste is stirred in the drying device, the water content is separated and flows down to the lower part of the device, but in many cases these do not evaporate. Therefore, this stored wastewater is also incinerated in the incinerator combustion chamber.

[0014]

EXAMPLES Examples of the present invention will be described, but the present invention is not limited thereto. Example 1 100 kg of Chinese cabbage (water content approximately 95%), which is considered to have almost the same moisture content as kitchen garbage, was put into a hopper-type drying device 1 (capacity 100 kg / cycle) having a stirring impeller 3 as shown in FIG. Then, the drying process was performed under the following conditions.

Decompression degree in the dryer 500-800 mmAq Temperature -20 ± 5 ° C Air flow rate 10 m / sec Treatment time 40 minutes ± 10 minutes Stirrer blade rotation speed 15 ± 5 rpm As a result, the water content of Chinese cabbage after treatment is 60-70 % Is dehydrated,
It could be easily incinerated in the incinerator. The results of measuring the dehydrated state are shown in FIGS.

As is apparent from FIGS. 2 and 3, 40-45
It can be seen that the dehydration reaches almost saturation in minutes, and further drying treatment is ineffective. The drying time and the dehydration rate were as shown in Table 1.

[0017]

[Table 1] Time 15 ′ 30 ′ 45 ′ 60 ′ Dewatering and drying 1 time 40% 56% 77% 79% 〃 2 times 35% 60% 74% 76% After drying, the cradle 4 at the bottom of the hopper opens to the left and right. He, (
1 (B)) The dried Chinese cabbage is sent to the sorting device 9 by the belt conveyor 8. Actually, raw garbage is dried instead of Chinese cabbage, and combustible substances and incombustible substances are separated in a separating device. Example 2 Using the same drying apparatus as in Example 1, 100 kg of Chinese cabbage having a water content of about 95% was used and the temperature of the introduced air was set to 80 ° C. ± 10 ° C., except under the same conditions as in Example 1. Was done. The results are shown in Table 2.

[0018]

[Table 2] Time 15 '30' 45 '60' 75 'Dehydration rate 70% 83% 88% 91% 94% Of the wastes that have been separated by drying, vegetable wastes, weeds, etc. are composted. It can also be used as a raw material.

[0019]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, a waste having a large water content, which has been difficult to incinerate in the past, is dried and separated by effectively utilizing the incineration exhaust heat of the waste itself. However, it is possible to incinerate efficiently, and it is extremely large for industrial benefit.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a drying apparatus for carrying out the present invention,
(A) shows the state of drying, and (B) shows the state of taking out the dried waste.

FIG. 2 is a graph illustrating a dehydrated and freeze-dried state of waste.

FIG. 3 is a graph illustrating a dehumidification state of waste.

[Explanation of symbols]

1 ... Waste storage hopper 2 ... Motor 3 ... Rotor blade 4 ... Receiving stand 5 ... Decompression duct 6 ... Air supply duct 7 ... Refrigerating or heated air inlet pipe 8 ... Belt conveyor 9 ... Separation device

Claims (9)

[Claims] 1. A drier equipped with a stirring means is maintained at a reduced pressure, waste having a large water content is charged into the drier, and the supplied air is cooled to −20 ° C. ± 5 ° C. , A pretreatment method for waste incineration, which comprises subliming and dehydrating freezing water. 2. The pretreatment method for waste incineration according to claim 1, wherein the reduced pressure is maintained by making the discharge amount larger than the amount of air fed into the drying device. 3. The pretreatment method for waste incineration according to claim 1 or 2, wherein the incoming air is cooled by an absorption cooling device that uses the heat retained in the exhaust gas from the incinerator. 4. The pretreatment method for incineration of waste according to claim 1, 2 or 3, wherein the dehydrated waste is subjected to a separating means, and the combustible separated is crushed and then dried with warm air and then incinerated. 5. The pretreatment method for waste incineration according to claim 4, wherein the dry air of the crushed combustible material is heated by the exhaust gas from the incinerator. 6. A dryer equipped with a stirring means is maintained at a reduced pressure, a waste having a large water content is charged into the dryer and stirred, and the supplied air is heated to 80 ° C. ± 10 ° C. , A pretreatment method for waste incineration, which comprises evaporating and dehydrating contained water. 7. The waste incineration system according to claim 6, wherein the discharge amount is made larger than the amount of air sent to the drying device to maintain a reduced pressure, and the heating of the input air is performed by heat exchange with exhaust gas from the incinerator. Pretreatment method for. 8. The pretreatment method for incineration of waste according to claim 6 or 7, wherein the dehydrated waste is subjected to a separating means, and the combustible separated is crushed, dried with dry cold air and then incinerated. 9. The pretreatment method for waste incineration according to claim 1, wherein the exhaust gas from the drying device and the generated wastewater are sent to the combustion chamber of the incinerator.