JPH11217461A - Process for thermally decomposing chlorine-containing thermoplastic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for thermally decomposing a chlorine-containing thermoplastic resin, which comprises mixing the resin with a powdery or particulate solid substance, thermally decomposing the mixture in a reactor, removing chlorine, discharging the thermal decomposition residue from the reactor and incinerating the residue in an incinerator without increasing the amount of ash produced from incineration. SOLUTION: A chlorine-containing thermoplastic resin and ash produced from an incinerator as a powdery or particulate solid substance are fed into a reactor 1 and thermally decomposed therein to form a mixture containing a substantially chlorine-free thermal decomposition residue and incineration ash and a gas containing hydrogen chloride. The mixture and the gas are discharged from the reactor 1, and the discharged thermal decomposition residue is incinerated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a chlorinated thermoplastic resin or a crushed product of plastics containing the chlorine-containing thermoplastic resin, such as a vinyl chloride resin or the like. (Collectively referred to as resin) is heated and melted and thermally decomposed.

[0002]

2. Description of the Related Art In order to treat waste plastics, the waste plastics is heated and melted to reduce the volume so that it can be handled easily, and then used as a solid fuel or heated. Conventionally, there has been known a method of converting into a raw material for producing liquid fuel or activated carbon by further pyrolyzing after melting.

[0003] In particular, in the case of a chlorine-containing thermoplastic resin containing chlorine and generating harmful gases such as hydrogen chloride and dioxin when burned as it is, such as polyvinyl chloride, this is thermally decomposed, It is necessary to remove chlorine as hydrogen chloride under controlled conditions, and the residue after the removal of chlorine, that is, pyrolysis products, can be used as it is as a safe fuel or as a raw material for other useful products can do.

[0004] When the chlorine-containing thermoplastic resin is heated and its temperature is raised in sequence, it begins to melt when it reaches a certain temperature. Then, as the melting temperature increases, thermal decomposition starts, the thermoplastic resin becomes low molecular, and gaseous low molecular hydrocarbons and other decomposition gases are generated. When thermal decomposition is further advanced at a high temperature, the dehydrogenation reaction starts to occur violently,
As a result of the progress of the polycondensation reaction, precipitation of a carbonaceous substance, so-called coking, occurs.

[0005] The temperature at which the series of reactions such as the melting, pyrolysis and coking processes starts depends on the type of the chlorine-containing thermoplastic resin, but depends on the type of the pyrolysis product to be used. Controlling when to stop the reaction is important in production technology.

For example, when the waste plastics is a thermoplastic resin of a type not containing chlorine, and only a solid fuel is a main target product, the volume of the thermoplastic resin is reduced by simply melting, and cooling is performed. It may be solidified. However, in the case of a chlorine-containing resin such as polyvinyl chloride, it is necessary to remove the chlorine component even if the purpose is to use the product as a solid fuel. It is necessary to raise the temperature of polyvinyl chloride to a temperature (200 to 400 ° C.) at which hydrogen chloride is generated as hydrogen chloride. On the other hand, when various fuel oils are used as final products, it is necessary to maintain the reaction temperature at which the yield of the liquid product is the highest.

Generally, it is not easy to smooth the temperature distribution in a reactor because the thermal conductivity of molten plastics is low. Therefore, if the structure of the reactor is not appropriate, the above-described steps of melting, pyrolysis and coking may occur simultaneously in the reactor, not only reducing the yield of the target product, but also, for example,
If the caulking occurs violently, it may cause an operational problem such as clogging in the piping of the equipment.

Various reactors have been used for the melting or thermal decomposition reaction, and can be broadly classified into the following three types. (1) Tank-type reactor (2) Extruder-type reactor (3) Rotary kiln-type reactor The tank-type reactor heats chlorine-containing thermoplastic resin, for example, plastics, contained in the tank from the outer wall of the tank. In this method, melting and thermal decomposition are performed, but the heat transfer area is small compared to the internal volume of the tank, and the heat transfer coefficient to the molten plastic is also small. Therefore, in order to transfer a sufficient amount of heat to the plastics in the tank, a large heat flux (heat transfer amount per unit area) is required.
That is, the temperature gradient in the reactor is steep, and even if the temperature on the heating surface has reached the temperature at which coking occurs,
The required reaction temperature may not be obtained sufficiently.

The extruder-type reactor uses an extruder conventionally used for molding plastics as a reactor. That is, while applying a considerable amount of mechanical pressure and shearing stress due to torsion to plastics in a solid state at room temperature, which is accommodated in a reactor, the plastics are extruded, and the temperature is raised by frictional heat generated at that time. In this method, the softened thermoplastic resin is further melted and kneaded while being heated by an auxiliary electric heater, a heating medium jacket, or the like, and then heated to a pyrolysis temperature as necessary.

Although this method has a higher heat transfer efficiency than a tank reactor, its structure makes it difficult to produce a large-capacity apparatus. In addition, when used for the thermal decomposition reaction of polyvinyl chloride, which generates corrosive hydrogen chloride gas at a high reaction temperature, the extruder often causes corrosion on the material.

As the rotary kiln type reactor, a so-called rotary kiln generally used in the production of cement or the like is used. In the kiln, a chlorine-containing thermoplastic resin such as plastics is thermally decomposed while rotating and heating. This rotary kiln type reactor has a high ability to cope with coking that occurs particularly when pyrolysis is required at high temperatures.

When a rotary kiln type reactor is used, it is necessary to add and mix a powdery solid substance to plastics which is a main reactant charged in the kiln. That is, by adding and mixing the particulate solid material, the molten plastics, which is a viscous fluid that is difficult to handle, is coated on the particulate solid material, and the fluidity thereof is improved, so that the handling becomes easier. In addition, even if a coking reaction occurs, coke precipitation occurs mainly on the surface of the mixed solid material, and the coke deposited on the wall of the kiln is scraped off by friction between the rotating kiln and the solid material in the kiln. . Therefore, when a rotary kiln type reactor is used, it is an essential condition to add and mix a powdery solid substance.

If a solid fuel such as coal or coke is used as the particulate solid substance, a mixture of the solid substance and a pyrolysis product of plastics can be used as a solid fuel or metallurgical material without separation. be able to.

Further, even when using a reactor of another type, if the powdered solid material is mixed with the plastics and the surface of the powdered solid material is thinly coated with the molten plastics, the surface area can be reduced. It can be subjected to a thermal decomposition reaction in a largely secured state, which is extremely advantageous in smoothing the temperature distribution and promoting diffusion and separation of the decomposition gas.

[0015]

As described above, if a solid fuel such as coal or coke is used as a particulate solid material mixed with a chlorine-containing thermoplastic resin such as plastics, the heat of the solid material and the plastics can be reduced. The mixture with the decomposed product can be used as a solid carbonaceous fuel or metallurgical material without separation as it is and can be used effectively in steelworks and thermal power plants.

However, facilities such as steelworks and thermal power plants that use the above-mentioned solid carbonaceous fuels and metallurgical materials are limited in area and few in number. On the other hand, in recent years, the sources of waste plastics are diverse and widely present nationwide.

Therefore, there is not always a facility such as a steel mill or a thermal power plant that uses solid carbonaceous fuel near a source of waste plastics. Often have to be transported. For this reason, there is a problem that a large amount of cost is required for transporting the solid carbonaceous fuel, so that economical treatment cannot be performed.

Therefore, the present inventors have found that if the solid carbonaceous fuel is incinerated by incineration facilities for general and industrial wastes installed in various parts of the country, the waste incineration facility may be a source of waste plastics. We focused on the fact that it can be economically treated because of its relatively close location.

However, in the incineration facilities for general and industrial wastes, the treatment of the incinerated ash generated is a problem. Therefore, the solid waste discharged from the reactor using the waste incineration facility is used. It is extremely important to avoid increasing the amount of incineration ash generated when incinerating materials.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to mix a particulate solid material with a chlorine-containing thermoplastic resin such as plastics and thermally decompose it in a reactor to remove chlorine. To provide a method for treating the pyrolysis residue discharged from the reactor and using the incineration equipment for general and industrial waste without increasing the amount of incinerated ash discharged from the incineration equipment Is to do.

[0021]

Means for Solving the Problems In view of the above-mentioned situation, the present inventors have utilized incineration facilities for general waste and industrial waste, which are located relatively close to each other in any area, Intensive research has been conducted to develop a method for thermally decomposing chlorine-containing thermoplastic resin waste such as waste plastics without increasing the amount of incinerated ash discharged from these incinerators. As a result, the following findings were obtained.

(1) When thermally decomposing waste plastics in a reactor, a thermally stable powdery solid substance is added to and mixed with the waste plastics, and the molten plastics, which is a viscous fluid, is powdered. If coated on the surface of a granular solid substance, its fluidity can be improved, and the thermal decomposition reaction is performed with a large surface area, so the temperature distribution during the thermal decomposition treatment in the reactor is smoothed Thus, diffusion and separation of the decomposition gas can be promoted.

(2) If the solid waste that has been pyrolyzed and discharged in the reactor is incinerated with general waste and industrial waste incineration facilities installed in various parts of the country, it can be removed to remote locations. It is economical because it does not need to be transported up to However, when the solid waste is incinerated in a waste incineration facility, it is necessary not to increase the amount of incinerated ash discharged from the incineration facility.

(3) When coal or coke is used as the particulate solid substance added to the waste plastics during the thermal decomposition treatment in the reactor, the amount of incinerated ash is reduced as compared with the case where sand or the like is used. However, it is inevitable that the amount of incinerated ash discharged from the incinerator increases due to the ash contained in the coal and coke itself. Also, the use of expensive solid fuels such as coal and coke for incineration in waste incineration facilities that do not require auxiliary fuel is not economically feasible.

(4) Therefore, if incinerated ash generated from a waste incinerator that incinerates waste plastics or the like is used as the powdery solid substance added to the waste plastics, the incinerated ash from the incinerator may be used. It does not increase the generation.

The present invention has been made on the basis of the above-mentioned findings, and is based on a chlorine-containing thermoplastic resin such as a vinyl chloride resin or a crushed plastics containing the chlorine-containing thermoplastic resin, which is produced from an incinerator. The incinerated ash thus obtained is charged into a reactor, and both are mixed in the reactor in a state of 200-200.
Pyrolysis in an atmosphere substantially free of oxygen at a temperature in the range of 400 ° C. to form a solid mixture of pyrolysis residue and incineration ash substantially free of chlorine, and a cracked gas containing hydrogen chloride And discharged from the reactor,
The present invention is characterized in that the discharged solid mixture of the pyrolysis residue and incinerated ash is incinerated.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, when a crushed product of a chlorine-containing thermoplastic resin, for example, plastics, is pyrolyzed in a reactor, a powdery solid substance added to the plastics is supplied from various waste incinerators. Use the generated incineration ash (including fly ash; the same applies hereinafter). That is, by mixing plastics with incineration ash generated from various waste incinerators, a plastics melt, which is a viscous fluid, is coated in a thin film on the surface of the incineration ash.

As a result, the plastics becomes a readily flowable reactant having a large surface area and is easily handled in a reactor at a temperature of 200 to 400 ° C. in an atmosphere substantially free of oxygen. Thermal decomposition under the following conditions promotes smoothing of temperature distribution and diffusion and separation of cracked gas, and a solid mixture of pyrolyzed residue and incinerated ash substantially free of chlorine, and cracked gas containing hydrogen chloride gas And discharged from the reactor.

The discharged solid mixture of the pyrolysis residue and incinerated ash is incinerated in a waste incineration facility for general waste and industrial waste to increase the amount of incinerated ash generated from the incinerator. The reaction control of the thermal decomposition reaction of the plastics can be facilitated without the above.

As the reactor, a tank type reactor may be used in addition to a rotary kiln type reactor, and a part or all of the thermal decomposition reaction may be performed using an extruder type reactor. .

The pyrolysis reaction in the reactor starts at 200 ° C. and ends at 400 ° C. Therefore, the thermal decomposition temperature is 20
It is necessary to be in the range of 0 to 400 ° C. In addition,
The particle size of the incineration ash charged into the reactor is preferably 15 mm or less. If the particle size of the incinerated ash exceeds 15 mm, the surface area with respect to the weight ratio of plastics and incinerated ash becomes insufficient.

Next, an example of an apparatus used in the method of the present invention will be described with reference to the drawings. As shown in FIG. 1, a raw material supply port 3 is provided at one end of a cylindrical rotary kiln type reactor 1 having an outer cylinder 2 and rotating from one end to the other end, which rotates about its axis. And one end of a screw feeder 4 is attached to the raw material supply port 3.

At the other end of the screw feeder 4 is provided a hopper 5 having a double-sealed damper for accommodating waste vinyl chloride crushed material and incinerated ash. An inert gas supply pipe 6 for blowing gas is connected. Reference numeral 7 denotes a hot-air generating furnace for supplying hot air to the space between the outer cylinder 2 and the reactor 1 to heat the reactor 1. At the other end of the reactor 1, a gas outlet 8 and a solid waste outlet 9 are provided.
Is connected to the waste gas treatment unit 10.

With the above-described apparatus, the crushed waste vinyl chloride and the incinerated ash supplied from the hopper 5 through the screw feeder 4 into the rotary kiln type reactor 1 are mixed in the rotating reactor 1, and are mixed with the outer cylinder 2. Reactor 1
In the state where the surface of the incineration ash is coated with a vinyl chloride melt, the inside of the reactor 1 inclined from one end to the other end is directed downstream with the hot air supplied to the space between While moving, it is pyrolyzed on the surface of the incineration ash.

The inert gas such as nitrogen blown into the reactor 1 from the inert gas supply pipe 6 through the hopper 5 and the screw feeder 4 generates heat containing hydrogen chloride generated in the reactor 1 as a main component. The cracked gas is carried toward the gas outlet 8 of the reactor 1 and is continuously discharged from the gas outlet 8. The pyrolysis gas discharged from the reactor 1 is
Treated by the waste gas treatment unit 10 while being substantially free of chlorine produced in the reactor 1;
The mixture of the pyrolysis residue and the incineration ash is discharged from the solid waste discharge port 9 at the other end of the reactor 1 and incinerated in a nearby waste combustion furnace.

[0036]

Next, the present invention will be described with reference to embodiments.
Using the apparatus shown in FIG. 1, 50 volumes of waste vinyl chloride resin crushed to 15 mm or less and 50 volumes of incineration ash with a particle size of 7 mm or less discharged from a municipal waste incinerator, housed in the hopper 5 using the apparatus shown in FIG. The mixture was supplied into the rotary kiln type reactor 1 through the screw feeder 4 and nitrogen gas was blown into the reactor 1 through the hopper 5 and the screw feeder 4 from the inert gas supply pipe 6.

The reactor 1 is rotated about its axis, and the mixture of waste vinyl chloride resin and incinerated ash in the reactor 1 is heated to 330 ° C. by hot air supplied to the space between the outer cylinder 2 and the reactor. And pyrolyzed. As a result, 97% of waste vinyl chloride resin
Was separated and removed in the pyrolysis gas.

The mixture of the pyrolysis residue and the incinerated ash, substantially free of chlorine, discharged from the reactor 1 can be incinerated without increasing the amount of incinerated ash in a waste combustion furnace. Was.

[0039]

As described above, according to the present invention,
A powdered solid substance is mixed with a chlorine-containing thermoplastic resin such as plastics, and this is pyrolyzed in a reactor to remove chlorine, then discharged from the reactor, and the discharged pyrolysis residue is compared. The incineration equipment for general waste and industrial waste installed in the vicinity of the source of waste plastics has an industrially useful effect that it can be treated without increasing the amount of incinerated ash.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of an apparatus used in the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reactor 2 Outer cylinder 3 Raw material supply port 4 Screw feeder 5 Hopper 6 Inert gas supply pipe 7 Hot air generator 8 Gas discharge 9 Solid waste discharge 10 Waste gas treatment unit

Claims (6)

[Claims] A chlorinated thermoplastic resin such as a vinyl chloride resin or a crushed plastics containing said chlorine-containing thermoplastic resin and incinerated ash generated from an incinerator are charged into a reactor. Within 200 ~
Pyrolysis in an atmosphere substantially free of oxygen at a temperature in the range of 400 ° C. to form a solid mixture of pyrolysis residue and incineration ash substantially free of chlorine, and a cracked gas containing hydrogen chloride And discharging the solid mixture of the pyrolysis residue and the incineration ash discharged from the reactor, and incinerating the solid mixture. 2. The method according to claim 1, wherein the pyrolysis is performed using a rotary kiln type reactor as the reactor. 3. A tank-type reactor is used as the reactor,
The method of claim 1, wherein said pyrolysis is performed. 4. The method according to claim 1, wherein an extruder-type reactor is used as the pyrolysis reactor, and a part or all of the pyrolysis is performed. 5. The method according to claim 1, wherein the incineration of the solid mixture of the pyrolysis residue and the incineration ash discharged from the reactor is performed by a waste incineration facility such as general waste or industrial waste. A method according to any one of the preceding claims. 6. The particle size of the incinerated ash charged into the reactor is 1
The method according to any one of claims 1 to 5, which is less than or equal to 5 mm.