JPH10216465A - Thermal decomposition of waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a long term continuous operation of a carbonizing furnace by allowing a produced gas by thermal decomposition to contact with a water or a solvent containing a radical generation preventing agent and/or a radical capturing agent in the case when a waste constituted mainly by an org. matter is decomposed thermally in a state deficient with oxygen. SOLUTION: In the case when a refuse charged into a refuse box for a combustible substance is decomposed thermally in the carbonizing furnace 1, the refuse is charged into the furnace by interposing a rotary valve 4 after charging the refuse into a hopper 2 and compressing the refuse with a pressing machine 3. Then an inside of the carbonizing furnace 1 is vacuumized by sucking with a blower 15 through a gas discharge port 10 and a piping 13 and heated by energizing to a heater 8 provided at a heating part 7 of a lower part outer wall of the carbonizing furnace 1. In this way, a pyrolysis product gas generated by this method is suck with the blower 15 to introduce the water containing the radical generation preventing agent and/or the radical capturing agent to storage tanks 11 and 12, then a part is cooled and condensed, and a noncondensable gas and low b.p. tar, etc., are burned with a city gas range 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyrolysis method for heating and carbonizing waste mainly composed of organic substances in order to reduce the volume, weight, disinfect and deodorize the waste. More specifically, the present invention relates to a pyrolysis method that eliminates interruption of pyrolysis due to clogging of a pipe due to a tar component in a gas generated by the pyrolysis and an inability to operate a rotating device and enables continuous operation for a long time.

[0002]

2. Description of the Related Art In order to reduce the volume and volume of waste mainly composed of organic matter, burning or carbonizing the waste has been conventionally performed. By the way, in urban areas where the generation of smoke, soot and odor is a problem, especially when installing relatively small organic waste treatment equipment, carbonization furnaces that heat in an oxygen-deficient state are more various than ordinary combustion furnaces. It is advantageous for various reasons.

One of the reasons is that the amount of generated gas is small. In the combustion furnace, the polymer is completely oxidized by oxygen in the air, so the components of the product gas are carbon dioxide, steam,
Residual nitrogen. On the other hand, in a carbonization furnace, a thermal decomposition reaction occurs in an oxygen-deficient atmosphere, so that the polymer is changed into carbide, tar, and gas by cutting and crosslinking of the main chain. For this reason, the amount of generated gas to be processed is much smaller in the carbonization furnace than in the combustion furnace, so that hydrogen chloride and the like in the generated gas can be easily removed by washing with water. Another reason is
Since the waste is thermally decomposed in an oxygen-free state, the amount of dioxin generated is small even if the waste contains a substance containing chlorine or a chlorine compound.

[0004]

By the way, various decomposition products are generated by the thermal decomposition of the waste in the carbonization furnace. When the temperature in the furnace becomes higher than the boiling point, the decomposition products are converted into evaporative gas to form a gas outside the furnace. The high-boiling components are mainly condensed by washing with water and are captured as liquid tar. However, some tar that is not condensed by washing is condensed while moving in the piping and adheres to the inside of the device and the piping. The adhered tar becomes highly viscous over time, and it has been necessary to frequently stop the operation of the pyrolysis furnace and clean it in order to stop the equipment or clog the piping.

In order to solve this problem, a specific device such as a device for charging the gas and electrically separating the gas or an ultrasonic device so as to prevent the diffusion of the tar gas which is hardly condensed by the above-mentioned water washing, is adopted. Methods such as collecting gas and coating equipment or piping with a resin with low tar adhesion such as fluorocarbon resin have been known, but the above equipment is very difficult to install in a small-scale carbonization furnace. However, coating with a fluororesin or the like is not an effective method, and an economical and effective method for preventing tar adhesion is demanded.

The present invention has been made in view of such circumstances, and an object of the present invention is to thermally decompose waste mainly composed of organic substances in a carbonization furnace in an oxygen-deficient state, and to wash the generated gas with water. An object of the present invention is to provide a pyrolysis method that enables long-term continuous operation of a carbonization furnace even when tar or the like that is difficult to be trapped adheres to piping or equipment of the carbonization furnace.

[0007] Many of the conventional techniques are based on the idea that the continuous operation time of a carbonization furnace is extended by preventing tar from adhering to a pipe or the like. By the way, tar generated together with a non-condensable gas when pyrolysis of waste mainly composed of organic matter in a carbonization furnace is often liquid at room temperature, and tar is a mixture of various boiling components.
On the other hand, tar attached to equipment and pipes has high viscosity,
It was often dry to the touch, which was thought to be due to evaporation of the low-boiling components in the tar over time, leaving relatively high-boiling components. The present inventor thought that if the viscosity of the tar is low, it may not hinder continuous operation if the viscosity is low, and pays attention to the fact that waste mainly composed of organic matter contains a lot of plastic. As a result of intensive studies, the present invention has been achieved.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
What is claimed is: 1. A method for thermally decomposing waste mainly composed of organic matter in an oxygen-deficient state, comprising contacting a pyrolysis product gas with water or a solvent containing a radical generation inhibitor and / or a radical scavenger. By using a thermal decomposition method.

[0009]

Next, the present invention will be described in detail with reference to preferred embodiments. In the present invention, volume reduction of waste,
For the purpose of weight reduction, disinfection, deodorization, etc., the carbonization furnace used to thermally decompose the waste in an oxygen-deficient state and carbonize can be any of those conventionally used for the above purpose. There is no particular limitation. As the carbonization furnace, for example, an airtight heat-resistant container (pyrolysis furnace) filled with waste is heated to about 200 to 1500 ° C. with electric power, propane gas, city gas, kerosene or heavy oil from the outside, and generated by thermal decomposition. The gas to be discharged may be discharged by suctioning the gas under its own pressure or by a blower or the like, or may be blown into a hermetic heat-resistant container as a heating source by heating a heated inert gas (nitrogen gas, carbon dioxide gas, etc.).

In the present invention, the waste mainly composed of organic substances can be any of those mainly composed of organic substances, such as garbage from homes and restaurants, paper waste, bento shells, various kinds of waste. Examples include packaging materials, infusion sets from medical institutions, dialysers for dialysis, disposable diapers, fiber products such as gauze, and disposable gloves.

In the present invention, the above-mentioned waste is thermally decomposed in a carbonization furnace and the pyrolysis gas is discharged out of the furnace in exactly the same manner as the conventional pyrolysis method. At the time of thermal decomposition, when the heating temperature is 200 ° C. or less, the amount of generated gas and tar is small, and the effect of implementing the present invention is small. When the heating temperature is 1500 ° C. or more, special heat-resistant carbonizing furnaces are used. Furnace material is required, which is not economical.
The heating temperature varies depending on the components of the waste,
The range of 00-800 degreeC is desirable. For pyrolysis,
It is necessary not to mix oxygen (air) when introducing waste into a high-temperature furnace, and if oxygen is mixed, waste combustion occurs in the furnace and abnormal pressure increase in the furnace causes Cause trouble. Therefore, if the mixing of oxygen can be prevented, the operation of the carbonization furnace can be performed either batchwise or continuously.

A feature of the present invention is that the gas is used to generate radicals for cooling the discharged pyrolysis gas, removing hydrogen chloride in the gas, and condensing and removing high-boiling tar components and the like in the gas. Contacting with water or a solvent containing an inhibitor and / or a radical scavenger. Even when the tar component not condensed due to this contact condenses and adheres to the pipes and the equipment, the increase in the viscosity of the tar with time is suppressed, and the clogging of the pipes and the stop of the equipment are prevented. The method of contact is not particularly limited, and for example, a method of passing the gas through the above-mentioned water or solvent in a spray state or a shower state, a method of introducing (bubbling) the gas into the above-mentioned water or solvent, and the like. Is mentioned.

As the radical generation inhibitor and the radical scavenger used in the present invention, any of compounds capable of suppressing the generation of radicals and compounds capable of reacting with the generated radicals can be used. For example, radical polymerization inhibitors / inhibitors, etc., and radical scavengers, for example, a radical polymerization terminator, an oxidation deterioration inhibitor, etc., and at least one of them is used. Examples of the radical polymerization inhibitor / inhibitor include, for example, diphenylpicrylhydrazyl, tri-p-nitrophenylmethyl, N- (3-N-oxyanilino-1,3-dimethylbutylidene) aniline oxide and the like which are themselves stable. Free radicals, hydroquinone, p-benzoquinone, dichloro-benzoquinone, p-ter-butylcatechol, nitrosobenzene, picric acid, dithiobenzoyl disulfide, copper (II) chloride, iron (II) chloride, sulfur and the like can be mentioned.

Examples of the radical polymerization terminator include a polymerization terminator used in ordinary radical polymerization such as dialkyldithiocarbamate such as sodium dimethyldithiocarbamate, and hydroxylamine sulfate.

Examples of the antioxidant include organic compounds having active hydrogen known as high molecular oxidation stabilizers, for example, phenol compounds and amine compounds. Examples of the phenolic compound include hindered phenols such as 2,6-di-tert-butylphenol, 2,5-di-tert-butylhydroquinone, and 2,6-di-tert-butyl-p-cresol. .
Examples of the amine-based compound include phenyl-α-naphthylamine; p-phenylenediamines such as p-phenylenediamine and N, N′-diphenyl-p-phenylenediamine.

The amount of the above-mentioned radical generation inhibitor and the radical agent scavenger used is in the range of 5 ppm to 5% with respect to water or the solvent. The effect is unchanged and uneconomical even if used beyond. Preferably 10 to 50 ppm
It is.

Preferred among the radical generation suppressing and radical agent scavengers are water-soluble compounds. The water-insoluble one is a soluble solvent thereof, and is used by dissolving it in a solvent that dissolves the tar component. However, a solvent having a low boiling point is not preferred because it evaporates upon contact with a high-temperature pyrolysis gas. It is desirable to use a solvent having a boiling point at least higher than the gas temperature. When a compound having low solubility in water is used, the compound can be dissolved in a hydrophilic soluble solvent and mixed with water before use. In the present invention, after the pyrolysis gas is cooled with water, radical generation is suppressed and / or
Alternatively, it is preferable to bring the radical scavenger into contact with a soluble solvent for the tar in which the radical scavenger is dissolved, since the effect of suppressing the increase in viscosity of the adhered tar with time is further improved.

[0018]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. In Examples and Comparative Examples, refuse dumped in a combustible waste bin was used as waste mainly composed of organic matter, and pyrolyzed in a carbonization furnace described below. This garbage was, as a result of visual inspection, composed of plastic bags, plastic trays and cups, juus boxes, dustpaper, plastic bottles, fruits, leftovers of lunch boxes, and the like.

The above refuse is transferred to a carbonization furnace (with an internal volume of 4) shown in FIG.
(00 liters), and the dust was compressed by a pressing device 3 attached to the hopper in order to help the dust having a small bulk specificity into the furnace, and then put into the furnace via a rotary valve 4. The furnace bottom was previously filled with about 20 liters of sand to prevent the rotary valve 6 from overheating. The amount of dust is 35 kg, which is about 80% of the furnace volume. Next, the gas discharge port 10,
Blower (displacement 0.4m ³ /
Minute: Fuji Electric's ring blower VFC106PN) 1
The pressure was reduced to 75 cm in water column by suction at 5, and the heating was started by energizing the heating heater 8 at 8 KW installed in the heating section 7 on the lower outer wall of the carbonization furnace.

Two tanks connected to a carbonization furnace by a pipe 13 (capacity is 20 liters, filled with 10 liters of water)
11 and 12 are switching valves 1 during continuous operation of the carbonization furnace.
3. Use alternately by 3 to discharge condensed tar from unused tanks. The pyrolysis product gas from the carbonization furnace is sucked by the blower 15 and
The fuel gas is introduced into the tank 11 or 12 via the cooling gas tank 0, where it is cooled and partially condensed, and non-condensable gas and gaseous low-boiling tar are burned in the city gas stove 16.

35 minutes after the start of heating, the temperature in the furnace is 350 ° C.
And control to keep this temperature. One hour after the temperature of the thermometer T reached 350 ° C., the operation of the rotary valves 4 and 6 above and below the furnace was started. The discharge capacity of the upper rotary valve / the discharge capacity of the lower rotary valve is 4 /
It is one. The operation of the upper and lower rotary valves is performed intermittently to avoid mixing of oxygen into the furnace. During operation of the rotary valve, the hopper 2 or the residue receiving tank 5 is closed, and when the hopper 2 is replenished with dust or the residue is discharged from the residue receiving tank 5, the operation of each rotary valve is stopped. The waste treatment capacity of this carbonization furnace is 7 to 10 kg / hr as a pyrolysis residue.

Example 1 Hydroquinone was added and dissolved in water in the tanks 11 and 12 of the carbonization furnace, respectively, and a pyrolysis gas was bubbled therein. Five hours after the start of heating, the operation of the carbonization furnace was stopped, and the next day (about 10 hours later), the operation of the carbonization furnace was similarly performed for five hours. This operation was repeated, and the total operation time reached 50 hours. During this time, no stoppage of the blower and no clogging of the piping were observed.

During the operation period, a part of the tar and water in each tank was removed, the water was replenished, and half of the water was replaced three times, so that the concentration of hydroquinone after the operation was completed was reduced to about 50 ppm in each tank. Diminished. The pH of the water in the tank after the end of each operation during the period is 3 to 7,
When the pH is 5 or less, the pH is adjusted to 6 to 7 with sodium hydroxide.
Was adjusted.

After an operation time of 50 hours, the blower was decomposed and the state of adhesion of tarno was examined. The adhesion of tar was remarkably less than that of Comparative Example 1 described below. I didn't. Some of the adhering tar was dry to the touch, but it was found to be brittle, easily broken by touch and had no stickiness.

Example 2 In this example, the garbage of Example 1 was used in which 15% by weight of an agricultural vinyl chloride resin film was added to the total garbage. The operation of the carbonization furnace was performed in the same manner as in Example 1 except that 500 ppm of iron was dissolved, and the operation was stopped when the total operation time reached 26 hours. During this time, the blower stopped,
No clogging of the piping was observed. Further, the pH of the water in each tank after each operation during the period is 1 to 3,
When the pH was 2 or less, the pH was adjusted to 2 with sodium hydroxide.

After a running time of 26 hours, the blower was disassembled and the state of adhesion of tarno was examined. The adhesion of tar was remarkably less than that of Comparative Example 1 described below. I didn't. Some of the adhering tar was dry to the touch, but it was found to be brittle, easily broken by touch and had no stickiness.

Comparative Example 1 The operation of the carbonizing furnace was stopped in 5 hours in the same manner as in Example 1 except that no hydroquinone was added to the tanks 11 and 12, and the operation was restarted the next day, but the blower did not move.
When the blower was disassembled, a large amount of touch-dried rice cake-like tar adhered to the casing and blades of the blower,
It turned out that the blower did not move. Such an operation was performed five times, and the operation could be continued once for two days, but the other three times required the cleaning of the blower in one day of operation. In the fifth operation, the piping from the tank to the blower was clogged during the operation, the suction by the blower became insufficient, and the operation was stopped because the degree of pressure reduction in the furnace was reduced. The garbage of Example 2 was also thermally decomposed, and the result was the same as above.

[0028]

By using the method of the present invention, in the carbonization treatment of waste mainly composed of organic substances, the adhesion of tar to pipes and the like is reduced, and even if the tar is attached, the attached tar can be removed with time. Viscosity increase is suppressed,
Since the liquid tar is included, the carbonization of the waste can be continuously performed without drying out to the touch, without stopping the equipment or clogging the piping.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a pyrolysis furnace (carbonization furnace) used in Examples.

[Explanation of symbols]

 1: Decomposition furnace (carbonization furnace) 2: Hopper 3: Press device for pushing dusts 4: Rotary valve 5: Residue receiving tank 6: Rotary valve 7: Heating unit 8: Electric heater 9: Dust 10: Gas discharge unit 11: Water washing Tank 12: Rinse tank 13: Switching valve 14: Piping 15: Blower 16: Gas stove T: Thermometer P: Pressure gauge

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10B 53/00

Claims (3)

[Claims] 1. A method for thermally decomposing waste mainly composed of organic matter in an oxygen-deficient state, wherein a produced gas is contacted with water or a solvent containing a radical generation inhibitor and / or a radical scavenger. Thermal decomposition method of waste. 2. The method for thermal decomposition of waste according to claim 1, wherein the produced gas is passed through the water or the solvent. 3. The method of claim 1, wherein the radioactive substance generation inhibitor is capable of inhibiting radical polymerization.
The method for thermal decomposition of waste according to claim 1, wherein the inhibitor is a radical scavenger and / or an antioxidant is a radical polymerization inhibitor.