JP3409976B2 - Pyrolysis method and pyrolysis apparatus for plastics - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal decomposition method and a thermal decomposition apparatus for plastics contained in large amounts in general wastes and industrial wastes, and particularly to waste plastics containing a foamed resin containing halogenated hydrocarbons. The present invention relates to a disassembling method and a disassembling apparatus.

[0002]

2. Description of the Related Art Conventionally, when disposing of household electric appliances, they have been treated as general waste when discarded by general consumers, and as industrial waste when discarded by businesses. In this way, although the same waste home appliances were treated and the treatments differed depending on the disposal source, the landfill treatment was the mainstream in both cases.

Most of the waste home electric appliances are made of plastic, and for example, about 50% of plastic is used as a constituent material in refrigerators. If plastic is incinerated as it is, it will damage the incinerator. Therefore, it is necessary to establish a method for disassembling or reusing plastic in order to dispose of waste home electric appliances without landfilling.

As a method for continuously converting plastics into oil,
A method of charging in a dry distillation furnace heated to 400 ° C. has been proposed. However, in this method, the produced oil obtained by carbonizing the plastic is mainly composed of heavy oil components having a carbon number of 20 or more, but also contains a component having a low flash point and a high volatility of 20 or less. Therefore, it is not desirable to use it as heavy oil from the viewpoint of safety. Moreover, the oil produced by this method is partly waxed during storage, so it is difficult to use it directly as fuel oil.

[0005] In addition, a large number of products using foamed urethane resin are included in the waste home electric appliances, and halogenated hydrocarbons (CFC) such as CFC11 and CFC12 are mainly used as a foaming agent for this foamed urethane resin. Came. The urethane foam resin containing such a specific CFC or an alternative CFC as a foaming agent is classified into a soft foam and a hard foam depending on the degree of crosslinking, and the soft foam is used as an automobile part or a packaging container, and the hard foam is Widely used as a heat insulating material and sound absorbing material in various products including refrigerators. In particular, in a refrigerator, in addition to a specific CFC for foaming, a specific CFC is also used for a refrigerant, and about half of the refrigerator constituent material is made of plastic.

[0006] Landfilling a waste home electric appliance product containing a foamed resin containing such a halogenated hydrocarbon as a foaming agent is dangerous because chlorofluorocarbons such as CFC11 and CFC12 are gradually released. For this reason, it is required to treat the waste having such a urethane foam resin as a constituent material after efficiently detoxifying chlorofluorocarbon.

As a method for recovering the halogenated hydrocarbon contained in the urethane foam resin, a urethane foam resin of several tens μm is used.
A method of finely pulverizing to m size has been proposed (see Japanese Patent Laid-Open No. 147038/1993). And with this method,
The crusher must be tightly sealed to prevent the halogenated hydrocarbons from leaking out of the crusher. Therefore, the size of the apparatus is increased, and the crushing process needs to be performed in multiple stages.

In the refrigerator, about 2% of polyvinyl chloride is used as a constituent material. Since hydrogen chloride is generated when polyvinyl chloride is thermally decomposed, there are problems of corrosion of the dry distillation furnace and equipment piping, and problems of mixing organic chlorine compounds in the produced oil. Further, there is a problem that lead contained in the solder of the printed wiring board mixed in the waste is converted into lead chloride and scattered.

[0009]

As described above, in recycling waste plastics such as waste home electric appliances, detoxification of CFCs, improvement of quality of oil produced by decomposition of plastics, decomposition of plastics, etc. It was necessary to solve the problem of reducing the adverse effects on the equipment and piping used.

An object of the present invention is to solve the above-mentioned problems and to recover a product containing a light oil, which is highly useful as a fuel or a petrochemical raw material, as a main component by thermal decomposition of waste plastic.

Another object of the present invention is to safely and efficiently produce a high-quality product by thermal decomposition of waste plastic mixed with a foamed resin containing a halogenated hydrocarbon such as CFC or a halogen-containing plastic such as polyvinyl chloride. To recover the product.

[0012]

In order to solve the above problems, the inventors of the present invention have made extensive studies on the treatment of waste plastics, and as a result, by controlling the temperature of the process of thermally decomposing the plastics according to a predetermined method. The inventors have found that the quality of the produced oil can be improved, and completed the present invention.

In the method for thermally decomposing plastics according to the present invention, the pyrolysis temperature is maintained in the range of 300 to 400 ° C. for 10 minutes or more, and then 450 to 500 at a rate of 3 to 20 ° C./min.
The temperature is raised to a temperature in the range of ℃ and maintained in the range of 450 to 500 ℃.

During the thermal decomposition, a sulfur-containing gas selected from hydrogen sulfide, disulfur dibromide and carbon disulfide is supplied.

The plastic decomposing device according to the present invention is
A rotary furnace having a first region, a second region and a third region along the longitudinal direction, and a temperature of the first region of the rotary furnace are set to 3
The temperature of the third region is set to 450 to 500 ° C. at 00 to 400 ° C.
A controller for controlling the temperature of the rotary furnace so that a temperature gradient of the second region from the temperature of the first region to the temperature of the third region is set to 0 ° C .; A supply device for supplying plastic, and a temperature of the plastic is changed at a rate of 3 to 20 ° C./minute while the plastic is passing through the first region for 10 minutes or more and passing through the second region. And a supply control means for controlling the supply.

According to the above constitution, at a temperature of 300 to 400 ° C., the carbon-carbon bond breakage proceeds in the molten plastic to 450 to 500 ° C. for 3 to 20 ° C.
By performing thermal decomposition by raising the temperature at ° C / min, a light oil containing hydrocarbons having 20 or less carbon atoms as a main component, which can be effectively used as a fuel or a petrochemical raw material, is recovered.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Plastic is a polymer in which carbon atoms are connected in a chain form in the unit of thousands to tens of thousands. However, when heat treatment is performed, carbon-carbon bonds are randomly cleaved, and 1-44 hydrocarbon gases are produced and released from the plastic. When the plastic is suddenly charged into a thermal decomposition furnace at about 500 ° C., the residence time in the molten state is short, so that the carbon-carbon bond is gasified without being sufficiently cut. Therefore, the hydrocarbon gas produced by thermal decomposition has a gas having a carbon number of more than 20 as a main component, and thus the produced oil recovered by cooling becomes a heavy oil having a carbon number of more than 20. Further, since the produced oil contains a part of light oil having 20 or less carbon atoms, it is difficult to use it as heavy oil from the viewpoint of flash point and safety.

In order to recover a light oil having a carbon number of 20 or less, which has a high utility value as a fuel or a petrochemical raw material, as a main component,
It is necessary to appropriately control the heating temperature of the pyrolysis furnace so that the carbon-carbon bond of the plastic can be sufficiently cut in the molten state. In the present invention, as shown as a range T in FIG. 1, the temperature of the plastic is 300 to 400 ° C.
In the range of preferably 350 ° C. for at least 10 minutes or longer, preferably about 20 minutes, and then the heating rate of 3 to
450C-500C at 20C / min, preferably 10C / min
The heating temperature of the pyrolysis furnace is controlled so that the temperature is raised to a temperature in the range. By performing such temperature control,
98 with a kinematic viscosity of 20 cSt or less and a carbon number of 20 or less
Produced oil is obtained which accounts for more than%.

Since plastic is decomposed and gasified at a temperature of 450 ° C. or higher, it is necessary to sufficiently cut the carbon-carbon bond of the plastic before reaching this temperature. Cleavage of carbon-carbon bonds proceeds at 300 ° C. or higher, especially 30
In the range of 0 to 400 ° C., the cutting of carbon-carbon bonds proceeds inside the molten plastic. Therefore, from 300
Maintaining the temperature in the range of 400 ° C. facilitates the formation of low molecular weight hydrocarbon compounds when heated to the cracking gasification temperature. If the initial heating temperature exceeds 400 ° C,
The obtained thermal decomposition product is mainly a heavy component having 20 or more carbon atoms, and is in a waxy form having a kinematic viscosity of 500 cSt or more. In this regard, it is clear that the initial temperature of heating may be 300 ° C. or lower, and the temperature of the plastic is increased to 3 ° C. following the step of raising the temperature from room temperature to 300 ° C.
It suffices if it is within a range of 00 to 400 ° C. for a predetermined time. However, 3
Taking a long time to raise the temperature to 00 ° C. requires the length of the apparatus to be increased when the thermal decomposition treatment is performed using a continuous processing apparatus, and therefore should be adjusted according to the thermal decomposition apparatus used. is there.

Further, the temperature rise from the temperature of the molten state to the temperature of decomposition gasification affects the molecular weight distribution of the obtained product, and the rapid temperature increase widens the component distribution of the product oil. Therefore, after the heating temperature is raised to the decomposition gasification temperature at the temperature rising rate as described above, complete thermal decomposition is carried out at the decomposition gasification temperature. The temperature at which decomposition gasification occurs varies depending on the type of plastic, but most plastics undergo thermal decomposition at a temperature of about 450 ° C, so thermal decomposition is achieved by holding at 450 to 500 ° C for at least 20 minutes. .

It is desirable that the oxygen concentration in the atmosphere in the pyrolysis furnace when the plastic is subjected to heat treatment is suppressed to 0 to 5%. By controlling the oxygen concentration to 0 to 5%, the temperature rising time can be shortened and the amount of oxides in the exhaust gas can be reduced. Further, since it is possible to prevent the metal in the residue from being oxidized, it is easy to collect and recycle the metal, which is preferable in terms of resource protection.

Further, the main component of the thermal decomposition product has 15 carbon atoms.
In order to obtain a soft oil before and after, it is preferable to supply a sulfur-containing gas at the time of thermal decomposition as a catalyst that accelerates thermal decomposition and makes it lighter. Hydrogen sulfide (H ₂
S), disulfur dibromide (Br ₂ S ₂ ), carbon disulfide (CS
₂ ) etc. Further, hydrogen halide produced by decomposition of halogen-containing plastic such as polyvinyl chloride (PVC) contained in plastic can be neutralized and removed from the gas of thermal decomposition product by spraying calcium such as slaked lime. it can.

Halogenated hydrocarbon such as freon gas in the urethane foam resin contained in the plastic is released from the plastic while the plastic is heated and melted. These are treated with a decomposition catalyst and a halogen adsorbent. As the decomposition catalyst, Cr ₂ O ₃ / Al ₂ O ₃ , Cr ₂
O ₃ / ZrO ₃ , WZrO ₂ —TiO ₂ or the like is used, and as the halogen adsorbent, CaCO ₃ , Ca (O
H) ₂ , CaO, activated carbon and the like.

FIG. 2 shows a thermal decomposition apparatus for carrying out the thermal decomposition of the above plastic. The thermal decomposition apparatus 1 uses a rotary furnace (rotary kiln) in order to improve the accuracy of the temperature control of the plastic described above.

More specifically, the thermal decomposition apparatus 1 includes a rotary furnace 3, a charging hopper 5, a charging dual damper 7, a charging pusher 9, a discharging dual damper 11, an oxygen concentration control device 13, and a sulfur-containing gas supply. It has a device 15 and a calcium spraying device 17.

The temperature control device 19 divides the heating temperature of the rotary furnace 3 into three parts, namely, a front part 21, an intermediate part 23 and a rear part 25 to control the temperature. The front part 21 is at 300 to 400 ° C., the rear part 25 is at 450 to 500 ° C., and the intermediate part 23 is at the front part 2.
A temperature gradient is provided so that the temperature continuously rises from 1 toward the rear part 25.

A sulfur-containing gas concentration sensor 27 is installed in parallel in the intermediate portion 23 of the rotary furnace 3 to which the sulfur-containing gas supply device 15 is attached, and constantly measures the sulfur-containing gas concentration. The measurement value is used to control the supply amount of the sulfur-containing gas supply device 15 so that the sulfur-containing gas concentration in the intermediate portion 23 becomes a predetermined amount.

The residence time of the plastic in the rotary furnace 3 is adjusted by changing the rotation speed and the rotary furnace inclination angle by a rotary furnace control device (not shown).

The plastic waste is previously crushed to 300 by a crusher.
It is crushed to about mm square and charged from the charging hopper 5. To insert the plastic waste into the rotary furnace 3, first, the upper hopper of the input double damper 7 is opened and the waste is dropped into the purge chamber 29. After the upper hopper of the double damper 7 is closed, the lower hopper is opened, and the discarded waste is thrown into the rotary furnace 3 by the pushing pusher 9. This double damper 7 can prevent air from entering the furnace and has less troubles compared to the method of material sealing with a two-stage hydraulic cylinder, and the oxygen concentration control described below can be performed accurately. Be seen.

The oxygen concentration in the rotary furnace 3 is controlled by adjusting the flow rate of nitrogen gas supplied to the purge chamber 29 by the oxygen concentration controller 13. The oxygen concentration in the rotary furnace 3 is
The oxygen concentration sensor 31 attached to No. 1 constantly measures. When the oxygen concentration falls below the specified value, the oxygen concentration control device 13 reduces the flow rate of the nitrogen gas fed into the purge chamber 29. On the contrary, when the oxygen concentration in the rotary furnace 3 exceeds the specified value, the flow rate of nitrogen gas supplied by the oxygen concentration control device 13 increases. The oxygen concentration sensor 31 is controlled by using a system controller (not shown).
A control signal is sent to the oxygen concentration control device 13 on the basis of the above data to perform automatic control.

When polyvinyl chloride is contained in the plastic waste, hydrogen chloride is generated by the heat treatment.
Hydrogen chloride corrodes not only the inner wall of the rotary furnace 3 but also gas pipes and attached devices. Also, since hydrogen chloride reacts with the pyrolysis gas of plastics to produce organic chlorine compounds,
Organochlorine compounds are mixed in the produced oil, which hinders their use as fuels and petrochemical raw materials. Further, when the plastic waste contains a printed wiring board, lead in the solder used in the printed wiring board is scattered as lead chloride, which is not preferable from the viewpoint of environmental protection.
In this thermal decomposition apparatus, a hydrogen chloride concentration sensor 33 is provided in the latter part 25 of the rotary furnace 3 to constantly measure the hydrogen chloride concentration in the rotary furnace 3 and spray slaked lime from the calcium spray device 17 according to the measured value. To do. By neutralizing hydrogen chloride in the rotary furnace 3, not only can corrosion of the device be prevented,
Mixing of organic chlorine compounds in the produced oil is reduced, and lead scattering can be suppressed.

The freon-containing foamed resin mixed in the plastic waste is melted in the front stage portion 21 of the rotary furnace 3 to release most of the freon as gas. The molten resin after the release of CFCs is subsequently thermally decomposed and discharged as a hydrocarbon gas.

The upper portion of the rotary furnace 3 is connected to the gas exhaust pipe 35. The gas discharge pipe 35 is connected to the gas condensing unit 37. The chlorofluorocarbon gas released in the rotary furnace 3 and the hydrocarbon gas generated by the heat treatment of plastic or foamed resin are sent to the gas condensing unit 37 through the gas discharge pipe 35.

The gas condensing unit 37 is divided into a cooling chamber A and a cooling chamber B for cooling the gas at three stages of temperature, and the cooling temperature is controlled by a gas temperature control device (not shown). . For example, if the gas cooling temperature of the cooling chamber A is 50
The gas cooling temperature of the cooling chamber B is controlled to about 40 ° C., and the gas cooling temperature of the cooling chamber C is controlled to about 30 ° C.
The hydrocarbons condensed in the cooling chambers A, B and C are recovered in recovery tanks 39A, 39B and 39C, respectively. By controlling the cooling temperature in this manner, it is possible to separately collect light oils having different boiling points.

The freon gas released from the freon-containing foamed resin has a boiling point of 25 ° C. or less, and therefore passes through the gas condensing section 17 and is sent to the freon gas detoxification processing section.

The freon gas detoxification processing section is composed of a cracking catalyst tank 41 filled with a freon cracking catalyst and a halogen adsorbent,
It has a steam introducing device 43, and a catalyst supply unit and a catalyst discharge unit (not shown). The cracking catalyst tank 41 is externally heated by a heating device that heats the oil recovered by the gas condensing unit 37 as a fuel, and is heated to and maintained at a temperature of 500 ° C., for example. Freon gas is efficiently decomposed by the decomposition catalyst and the heating action. The water vapor has a function of suppressing the generation of harmful by-products such as carbon tetrachloride and improving the decomposition rate of CFC gas. Although hydrogen halides such as hydrogen chloride gas and hydrogen fluoride gas are generated by the decomposition of CFCs, poisoning of the catalyst can be prevented and the life of the catalyst can be extended by trapping it in the halogen adsorbent mixed with the catalyst.

In preparation for the case where a part of hydrogen chloride gas or hydrogen fluoride which could not be trapped by the halogen adsorbent is contained in the exhaust gas discharged from the fluorocarbon detoxification processing part, an alkali gas is used as the exhaust gas processing part. The water shower tower 45 is connected, and by this, the amount of hydrogen halide in the exhaust gas can be suppressed below the environmental standard.

[0038]

EXAMPLES The present invention will be described in more detail below based on the experimental results.

Example 1 The following operation was carried out using the thermal decomposition apparatus 1 of FIG. 2 equipped with a rotary kiln having a length of 6 m as the rotary furnace 3.

First, plastic waste (composition: 15% polyurethane, 5% polystyrene, 20% ABS, 40% polypropylene, 20% polyvinyl chloride) was crushed to about 300 mm square with a crusher.

Next, the rotary furnace 3 is set so that the residence time of the plastic in the rotary furnace 3 of the thermal decomposition apparatus 1 is 60 minutes.
The inclination angle is 1.43 degrees and the rotation speed is 0.7 Nrpm. The heating temperature of the front part (200 cm in length) of the rotary furnace 3 is 350 ° C, and the heating temperature in the middle part (150 cm in length) is 40 ° C.
The heating temperature of 0 ° C. and the latter part (length 250 cm) was set to 500 ° C. Cooling chamber A has a gas cooling temperature of 50 ° C., cooling chamber B
Has a gas cooling temperature of 40 ° C, and the gas cooling temperature of the cooling chamber C is 3
It was set to 0 ° C.

The crushed plastic waste was charged from the charging hopper 5 for thermal decomposition. During this period, the oxygen concentration in the rotary furnace 3 is controlled to be maintained at 0.5%, and the amount of supply is adjusted so that the hydrogen sulfide concentration in the rotary furnace 3 is 0.1% by using sulfur hydrogen as the sulfur-containing gas. Controlled. or,
Slaked lime was sprayed from the calcium spraying device 17 so that the hydrogen chloride concentration was 50 ppm or less.

By the above operation, the recovery tanks 39A, 3A
When the products recovered in 9B and 39C were analyzed, in each of the recovery tanks 39A, A having a peak of 15 carbon atoms was detected.
It was a mixture of heavy oil and via, a mixture of via and gasoline in the recovery tank 39B, and produced oil equivalent to gasoline in the recovery tank 39C.

[0044]

[0045]

As described above, according to the present invention, by appropriately setting the thermal decomposition temperature of plastic waste, it is possible to efficiently recover produced oil of a quality that can be effectively used as a fuel or a petrochemical raw material. Even when a foamed resin containing freon as a foaming agent or a plastic containing halogen is treated, it is possible to safely and efficiently detoxify freon and remove hydrogen halide. Furthermore, it is possible to recover metal from the residue and prevent harmful lead compounds from scattering. Therefore, it has not only industrial value but also an advantage in terms of global environment conservation.

[Brief description of drawings]

FIG. 1 is an explanatory view for explaining temperature control in a thermal decomposition treatment of a plastic according to the present invention.

FIG. 2 is a schematic configuration diagram showing an example of a thermal decomposition apparatus for performing a thermal decomposition treatment of plastic according to the present invention.

[Explanation of symbols]

1 Pyrolysis device 3 rotary furnace 7 Double damper for input 13 Oxygen concentration control device 15 Sulfur-containing gas supply system 17 Calcium atomizer 19 Temperature control device 37 Gas condensing section 41 Decomposition catalyst tank 43 Water vapor introducing device 45 Alkaline water shower tower

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fumio Tezuka 8 Shinsita, Isogo-ku, Yokohama-shi, Kanagawa Stock company in Toshiba Yokohama office (72) Terunobu Hayata 8 Shinsugita, Isogo-ku, Yokohama, Kanagawa Toshiba Yokohama Works (56) References JP-A-51-33169 (JP, A) JP-A-6-313173 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C10G 1 / 10 B09B 3/00 C08J 11/12 C10B 53/00

Claims (2)

(57) [Claims] 1. A pyrolysis method for heating and thermally decomposing plastic, which comprises maintaining the pyrolysis temperature in the range of 300 to 400 ° C. for 10 minutes or more and then raising the temperature to the range of 450 to 500 ° C. maintained in the range of 450~500 ℃ Te, up
During the thermal decomposition of the rustic, hydrogen sulfide, disulfur dibromide and
A method for thermally decomposing a plastic, characterized in that a sulfur-containing gas selected from carbon disulfide is supplied . 2. A rotary furnace having a first region, a second region and a third region along the longitudinal direction, and the temperature of the first region of the rotary furnace is set to 300 to 400 ° C. The temperature of the rotary furnace is set so that the temperature of the region is set to 450 to 500 ° C. and the temperature of the second region is raised from the temperature of the first region to the temperature of the third region. A control device for controlling, a supply device for supplying the plastic to the rotary furnace, a supply control means for controlling the supply so that the plastic passes through the first region for 10 minutes or more, and a sulfide water for the plastic.
Sulfur selected from elemental, disulphur dibromide and carbon disulfide
A pyrolysis device for plastics, comprising a gas supply device for supplying gas .