JPH05245463A - Treatment of mixed plastic waste and device therefor - Google Patents

Abstract

PURPOSE:To remove chlorine from a treated mixed plastic waste completely and thereby, recover high-purity hydrogen chloride by crushing the mixed plastic waste, then increasing the temperature stepwise until the highest attainable temperature level within a specified temperature range for thermal decomposition is attained separating the gas product from a fused solid. CONSTITUTION:A thermal decomposition reaction device 1 consists of a reaction cylinder 4 of corrosion-inhibitive material, thermocouples 5-1 to 5-3, a hopper 6, an opposite-direction rotating two-axial screw 7, an adjustment valve 10, a gas intake tube 11, and a fused solid outflow tube 12. A mixed plastic material is charged from the hopper 6. The temperature is increased stepwise using a heater 2 and monitoring it using the thermocouples 5-1 to 5-3 so that the highest attainable temperature level is 290 to 330 deg.C within a range up to 330 deg.C from a normal temperature. In addition, the mixed plastic material is stirred and mixed using an opposite-direction rotating two-axial screw 7 to cause a thermal decomposition. Further, the decomposed molten product and a decomposition gas are discharged by adjusting an outflow pressure using an adjustment valve 10. Consequently, the gas is separately recovered by an HCl recovery vessel 13 through a suction tube 11 and the decomposed molten product by a solid outflow tube 12, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a pretreatment for reducing the volume of a mixed plastic waste, recycling it into a pollution-free oil, and incinerating it in a pollution-free manner. It relates to a pyrolysis method and a treatment device for substantially removing.

[0002]

2. Description of the Related Art In Japan, the production amount of plastic raw materials in recent years is about 37.0% for polyolefin type plastics (eg polyethylene, polypropylene), about 17.0% for polyvinyl chloride (PVC) type plastics and polystyrene type. Plastics account for about 12.0%, and these thermoplastics account for the top, accounting for about 66.0% of the total plastic production.

On the other hand, plastics discarded after the end of their useful life are discharged as mixed plastic wastes, and the amount of disposal is increasing year by year.

The breakdown of mixed plastic waste is classified into general waste from households and industrial waste from production and processing plants. Regarding the treatment method of these mixed plastic wastes, very limited types of high quality are selected, processed into molded articles and reused, but most of them are landfilled or incinerated. Only.

However, it is difficult to secure a landfill site for mixed plastic waste, which is increasing year by year, and there is an urgent need to deal with it. At this time, in order to quickly solve the problem of the landfill site, it is considered necessary to incinerate the mixed plastic waste. However, since chlorine plastics are mixed in the mixed plastic waste, chlorine content is converted to HCl by incineration and mixed in the exhaust gas, which promotes deterioration and corrosion of the incinerator and piping. .. Further, if the exhaust gas containing HCl is scattered into the atmosphere as it is, it may cause a bad influence on living things and the natural environment.

Conventionally, HC from mixed plastic waste
The l removal technology removes HCl in the produced gas by a wet method and a dry method after treating at a high temperature in a thermal decomposition reaction or incineration. The wet method mainly performs alkaline cleaning and has a high HCl removal rate, but requires a large amount of cost for wastewater treatment, removal equipment and maintenance. The dry method includes a method of directly spraying an alkaline substance into the reaction furnace and a moving bed method, but the removal rate of HCl is lower than that of the wet method. As described above, the conventional method for removing HCl is that HCl generated in the reaction furnace at high temperature is
Corrosion progresses further because it is exposed to
Measures are urgently needed. On the other hand, it is impossible to completely separate PVC-based plastics from mixed plastic wastes.

[0007] Therefore, by utilizing the peculiar thermal characteristics of PVC-based plastics, it is possible to remove as pollution-free HCl as pretreatment by means of equipment corrosion, air pollution, recycling of dehydrochlorinated molten solids, and HCl. It is considered to be the best method in terms of reuse and processing cost.

[0008]

Even if PVC-based plastics (PVC) are selected and excluded from mixed plastic wastes, complete separation is impossible. Here, in order to efficiently remove HCl in the mixed plastic waste, it is necessary to grasp the thermal characteristics of the PVC plastic and study the method of de-HCl according to the thermal properties.

Therefore, the first object of the present invention is to treat HCl without pollution, so that the mixed plastic waste is treated in advance from the sample before the treatment such as volume reduction, pyrolysis oil conversion and incineration. It is to provide a method for removing harmful HCl gas and a pretreatment thermal decomposition apparatus.

A second object of the present invention is to pretreat the PVC plastic in the mixed plastic waste by thermal decomposition to generate only HCl gas, and dehydrogenate by a simple method.
The present invention intends to provide a Cl method and an apparatus therefor. In other words, by thermally decomposing the mixed plastic waste in the pre-treatment stage and de-HCling it, effective treatment of resources such as volume reduction, pyrolysis oil conversion and incineration by practical treatment conditions assuming pollution prevention. It provides the basic means for efficient use.

Another object of the present invention is HC generated by thermal decomposition of PVC plastic in mixed plastic waste.
It is an object of the present invention to provide a method and a processing apparatus for recovering 1 with extremely high purity and obtaining it in reusable purity and concentration.

[0012]

According to the research conducted by the present inventors, the object of the present invention is to obtain a sample obtained by pulverizing mixed plastic wastes as it is, or after dehydration, from room temperature to 330 ° C. The highest temperature reached in the range is 290-330
A mixed plastic waste treatment product in which chlorine is substantially removed and the volume is reduced, which is characterized in that it is thermally decomposed at a temperature gradually increasing to ℃, and then separated into a gas product and a molten solid substance. A further object of the present invention, which is achieved by a treatment method for obtaining a) is: a) a pyrolysis reactor having external heating for stepwise thermal decomposition of a sample obtained by pulverizing mixed plastic waste, b) a hopper for supplying a sample to a reaction tube installed in the thermal decomposition reactor, c) a counter-rotating biaxial screw for inserting a sample into the reaction tube of the thermal decomposition reactor, d) the above The reaction chamber in the space where the heated and melted product is evenly mixed on the outlet side of the reaction tube of the thermal decomposition reaction device and the adjusting valve for adjusting the outflow pressure e) Outflow from the adjusting valve at the outlet of the reaction tube of the thermal decomposition reaction device Gas production It has been found to be achieved by means of a mixed plastics waste treatment unit comprising a separator for separating the product and molten solids and f) a collector for recovering HCl from the gas product.

According to the present invention, a plastic melt substantially free of chlorine is obtained from the mixed plastic waste, and the melt is about 1/6 to 1/1 as compared with that before the treatment.
It is possible to reduce the volume to 5, and it is not only easy to dispose of or to bury it, but also it can be sufficiently used as a fuel.

Further, according to the present invention, HCl generated by thermal decomposition of PVC plastic can be recovered without being discharged into the atmosphere, and since HCl is recovered in high purity, its reuse can be expected. ..

The present invention will be described in more detail below.

It is known that when PVC-based plastics are heated in an inert gas, a unique weight loss curve is drawn. Here, the weight loss appears above 230 ° C and 360 ° C.
The first zone up to, the second zone from 360 ° C to 420 ° C, and the third zone from 420 ° C to 500 ° C can be observed.

Regarding the weight reduction in the first zone, almost all chlorine is desorbed and the decomposition reaction is carried out to release HCl.

Further, on the high temperature side above 360 ° C., C
Various lower hydrocarbons and their derivatives are produced by cleavage of the -C bond.

That is, the point is to remove only HCl from the mixed plastic waste by pretreatment. PVC-based plastics can be heated from 230 ° C to 3 at normal pressure.
When heated to 60 ° C., HCl is generated, but it is very difficult to completely remove chlorine in this temperature range.

The present invention is intended for mixed plastic wastes that are separately collected from general wastes and industrial wastes, and dehydrochlorination is performed by a simple treatment method to reduce the volume and to make pyrolysis oil. It also provides appropriate information for disposal measures such as incineration.

The mixed plastic waste used in the present invention may be any mixture as long as it is a mixture, but a copolymer or the like is also preferable. Further, the mixed plastic waste can be used regardless of the shape such as a film, a sheet or a molded product as long as it is a crushed product having an average particle size of about 20 mm or less, preferably 10 mm or less.

The operation of the present invention will be described in relation to processing measures. First, the mixed plastic waste, as it is or after dehydration, is put into a hopper installed in a thermal decomposition reactor having external heating, and the sample is inserted from room temperature in the reaction cylinder by a bi-directional rotating screw screw. In the reaction tube, a mixture of a gas product rich in HCl and a molten solid pyrolyzed under the uniform mixing and the adjustment of the outflow pressure in stages up to 320 ° C. is discharged. Other general-purpose plastics such as polyethylene, polypropylene, and polystyrene, which occupy a large amount, have a difference in thermal property that they do not vaporize unless they are about 370 ° C. or higher. Even if these different kinds of plastics are mixed, thermal properties are not combined, It retains its original characteristics.

Therefore, the thermal decomposition at 320 ° C. or lower is P
Dehydrochlorination selectively occurs from VC plastics, and a purity of 98.6% or more is obtained, and the activity for use is sufficiently possible.

Further, the melted solid matter that has flown out is reduced in volume and dehydrochlorinated, so that it can be used as a resource for pyrolysis oil conversion or fuel, etc., and can be useful for recycling and pollution prevention.
As described above, the present invention provides a basic series of treatment methods and a treatment apparatus for obtaining a molten solid substance having a reduced volume by dehydrochlorination of mixed plastic waste in a pretreatment.

The method and apparatus of the present invention will be described below with reference to the accompanying drawings. 1 is a schematic front view of the apparatus of the present invention, FIG. 2 is a schematic plan view, and FIG. 3 is a schematic right side view. In the front view of FIG. 1, the thermal decomposition reaction device (1) is
A heater (2), a temperature controller (3), a cylindrical reaction tube (4) covered with the heater (2), and a thermocouple (5-1) inserted in the reaction tube (4). , 5-
2, 5-3), a hopper (6) installed on top of the reaction tube (4) to supply the sample, and a bidirectional rotation type twin screw screw (7) for introducing the sample into the reaction tube (4). An electric motor (8) connected to a bi-directional screw type screw (7) for adjusting the rotation speed, and a reaction chamber (9) for uniformly mixing the heated and melted product at the outlet side of the reaction tube (4). And a regulating valve (10) for regulating the outflow pressure, a gas suction pipe (11) for inhaling only the gas component of the product, and a molten solids outflow pipe (12) for outflowing only the molten solids. ..

In the thermal decomposition reactor (1), a mixed plastic waste crushed to preferably a particle size of 10.0 mm or less is charged from a hopper (6) installed on the upper part of the reaction tube (4) to carry out the reaction. The sample is introduced by the counter-rotating biaxial screw (7) in the cylinder (4). The sample introduced by the counter-rotating twin-screw screw (7) was heated from room temperature to 330 ° C. by the temperature controller (3) connected to the outer circumference of the reaction tube (4) in the electric circuit of the heater (2). Up to the range, it is heated stepwise so that the highest temperature reaches 290 ° C to 330 ° C and is pyrolyzed. Here, the thermocouple (5-
1), (5-2) and (5-3) each independently perform temperature control, and the region of the thermocouple (5-3) has the highest attainable temperature. The preferred maximum temperature is 300 to 32
It is in the range of 0 ° C. In the present invention, it is necessary to heat the crushed sample of the mixed plastic waste in stages to the above-mentioned maximum temperature for the purpose. The stepwise operation is an operation of gradually increasing the temperature from room temperature to the highest temperature. Specifically, heating is performed at a rising rate of about 8 to 62 ° C./min, preferably 32 to 55 ° C./min so that the total heating time is about 4 minutes to about 30 minutes, preferably about 4 minutes to about 10 minutes. It is advantageous to control

The molten product obtained by this treatment is the reaction tube (4).
By uniformly mixing in the reaction chamber (9) on the outlet side of the, and adjusting the outflow pressure with the adjusting valve (10),
In the separation chamber, it is separated into gas components and molten solids,
Gas suction pipe (11), molten solids outflow pipe (1
It leads to 2).

The HCl recovery unit (13) is equipped with a suction pump (14) connected to the outlet side gas suction pipe (11) of the thermal decomposition reaction apparatus (1), an absorption tower (15), a spray pipe (16),
It comprises a packing (17) in the absorption tower (15), a withdrawal pipe (18) for absorbing liquid, and an adsorption tower (19) for minute gas.

In the HCl recovery unit (13), HCl rising by the suction pump (14) from the bottom of the suction tower (15) toward the top of the tower is a spray pipe (16) provided at the top of the tower.
The water then becomes mist and descends in the absorption tower (15). In addition, a packing (17) is provided in the absorption tower (15) to improve contact between water and HCl. The water descending the absorption tower (15) and the HCl rising from the bottom come into contact with each other and are absorbed by the water to accumulate as hydrochloric acid at the bottom of the absorption tower (15).
It is collected by the withdrawal pipe (18). The minute harmful gas further passes through the adsorption tower (19) and is completely adsorbed.

[0030]

EXAMPLES Next, the experimental results of processing using the thermal decomposition reaction apparatus (1) for volume reduction and dehydrochlorination in mixed plastic waste according to the present invention will be described.

Example The thermal decomposition reaction apparatus used in this example is the same as the thermal decomposition reaction apparatus (1) shown in FIG. 1, except that the reaction tube (4) and the thermocouples (5-1, 5-2, 5) are used. -3), the hopper (6), the counter-rotating biaxial screw (7), the regulating valve (10), the gas suction pipe (11) and the molten solids outflow pipe (12) are made of a material resistant to corrosion (for example, (Made of SUS27 or SUS32 steel) having the same structure as that shown in the drawing, and a reaction tube (4)
Within the length of 300 mm and the inner diameter of 26 mm (2 pieces),
The length of the screen is 275 mm and the diameter is 14 mm (2
), The blades were housed in the screen at even intervals, and the reaction cylinder (4) had a space volume of 0.2 liter.

The thermal decomposition temperature was raised stepwise from room temperature, the maximum temperature was changed from 260 ° C. to 320 ° C., and the dehydrochlorination state of the mixed plastic waste in which the mixing ratio of PVC was changed was examined. It was The analysis of residual HCl concentration of the produced molten solid product was conducted by heating a sample amount of 10 g at a constant rate from room temperature to 500 ° C. in a batch pyrolysis apparatus to pyrolyze it, thereby producing a gas product, an oil product and a residue. And the HCl concentration in the gas product was separated by gas chromatography and HC.
1 It was measured with a detector tube.

Samples used: As the sample, an industrial waste (PE / PP) mixed with high density polyethylene, low density polyethylene and polypropylene and an egg case (PVC) separated from general waste were used. PE / PP and PVC
For dehydrochlorination treatment of the mixture of
It was 1.70 kg / hr. For these samples,
Residual HCl of molten solid product de-HCled under various conditions
The analysis results of are shown below.

Only the PVC used was heated at a constant rate from room temperature to 500 ° C. in a batch pyrolysis apparatus to be pyrolyzed, and the HCl concentration in the produced gas was 57.6 wt%.
The concentration of HCl dissolved in the oil product was very small. Also, no HCl concentration was detected in the residue.

[1] Removal of HCl by heating pyrolysis temperature
Removed by the ratio; Table 1, the PVC to PE · PP in the present invention apparatus is mixed with 9.0 wt%, when the processing amount constant, the HCl in the thermal decomposition temperature of two hundred and sixty to three hundred twenty ° C. then allowed stepwise elevated from room It shows the analysis result of the removal rate.

[0036]

[Table 1] According to Table 1, the removal rate of HCl by the device of the present invention is high and the removal rate of HCl does not change even when the maximum temperature of the stepwise temperature increase from 260 ° C. to 300 ° C. is high when the treatment amount is as low as 0.32 kg / hr. The percentage is shown. It was confirmed that when the treatment amount was about 3.8 times the above, the removal rate of HCl was high from the maximum temperature of 300 ° C. or higher.

[2] Mixing ratio of PVC and removal of HCl
Ratio;

[0038]

[Table 2] Table 2 shows that PE / PP with PVC from 5.0 wt% to 15.
Analysis of the removal rate of HCl when mixed in the range of 0 wt% and thermally decomposed gradually from room temperature at the maximum temperatures of 300 ° C. and 320 ° C. and the treatment amount of 1.12 to 1.92 kg / hr. The results and the results of residence time are shown.

The residence time by the thermal decomposition apparatus of the present invention was determined as follows.

[0040]

[Equation 1] From Table 2, even if the mixing ratio of PVC is 15.0 wt%, the maximum temperature for stepwise thermal decomposition is 300 to 320.
It was confirmed that the removal rate of HCl was as high as 99.9 wt% or more even at a relatively low temperature of ℃.

The residence time for removing HCl is 4.5.
It was also confirmed that the time was as short as ~ 8.7 minutes.

[3] Comparison of HCl Removal Devices; Table 3
Is a mixture of PE and PP with 9.0 wt% of PVC, and is heated and decomposed in stages from room temperature to HCl at a maximum temperature of 320 ° C.
It is a comparison of the results of the removal ratios when the removal is performed by the device of the present invention and when the HCl removal is performed at 320 ° C. under the isothermal condition by the existing batch type device.

[0043]

[Table 3] From Table 3, it was confirmed that the removal rate of HCl by the apparatus of the present invention has higher accuracy than that of the existing apparatus, and the time for removing HCl is significantly shortened.

[4] Volume reduction of molten solid product; Table 4
In the apparatus of the present invention, PE / PP is mixed with PVC in an amount of 5.0 wt% to 15.0 wt%, the temperature is raised stepwise from room temperature, and the maximum temperature is thermally decomposed at 300 ° C. and 320 ° C. to remove H.
It shows the apparent density of the molten solid product subjected to Cl treatment and volume reduction. Here, PV is added to PE / PP at room temperature.
The apparent density of C mixed with 5.0 wt% to 15 wt% is about 0.13 kg / l.

[0045]

[Table 4] From Table 4, the apparent density of the molten solid product obtained by treating at 300 ° C. and 320 ° C. is 0.76 to 0.78 kg / l, which is about 1/6 of the apparent density at room temperature. It became clear that the volume would be reduced.

[5] Analytical result of HCl in gas product
Result: Using the device of the present invention, PVC was added to PE / PP at 5.0.
Table 5 shows the results of analysis of HCl in the gas components produced by mixing 1 wt% to 15.0 wt% of the mixture, gradually raising the temperature from room temperature, and thermally decomposing at a maximum temperature of 320 ° C.

[0047]

[Table 5] From Table 5, the HCl concentration in the produced gas component is 98.
It was found that the concentration was as high as 6 Vol% or more, and that it could be reused.

[Brief description of drawings]

1 is a schematic front view of an example of an apparatus suitable for performing mixed plastic waste treatment according to the method of the present invention.

FIG. 2 is a schematic view of the plane of FIG.

FIG. 3 is a schematic view of the right side surface of FIG.

[Explanation of symbols]

 1 Pyrolysis Reactor 2 Heater 3 Temperature Controller 4 Reaction Tube 5-1 Thermocouple 5-2 Thermocouple 5-3 Thermocouple 6 Hopper 7 Counter-rotating Biaxial Screw 8 Electric Motor 9 Reaction Chamber 10 Control Valve 11 Gas suction pipe 12 Molten solids outflow pipe 13 HCl recovery device 14 Suction pump 15 Absorption tower 16 Spray pipe 17 Packing material 18 Extraction pipe 19 Adsorption tower

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Suzuki Sat, Hokkaido, Toyohira-ku, Hokkaido 2-17-17 Tsukikanto, Industrial Technology Institute, Hokkaido Industrial Development Laboratory (72) Inventor Hiroyuki Nakatani New Home Nakanomachi, Himeji City 1-21

Claims (3)

[Claims] 1. A sample obtained by pulverizing mixed plastic waste is pyrolyzed in a temperature range from room temperature to 330 ° C. so that the maximum temperature reaches 290 to 330 ° C., and then gas products are obtained. And a molten solid, which is a treatment method for obtaining a mixed plastics waste treated product in which chlorine is substantially removed and the volume is reduced. 2. The treatment method according to claim 1, wherein a sample obtained by pulverizing the mixed plastic waste is dehydrated and then thermally decomposed at elevated temperature. 3. A pyrolysis reactor having external heating for stepwise thermal pyrolysis of a sample obtained by pulverizing mixed plastic waste, b) a reaction installed in the pyrolysis reactor. A hopper for supplying the sample to the cylinder, c) A bi-directional rotating biaxial screw for inserting the sample into the reaction tube of the thermal decomposition reaction apparatus, d) A heating tube melted on the outlet side of the reaction tube of the thermal decomposition reaction apparatus A reaction chamber in the space where the products are uniformly mixed and a regulating valve for regulating the outflow pressure e) for separating the gas product and the molten solid substance flowing out from the regulating valve at the outlet of the reaction tube of the thermal decomposition reactor Separator and f) Equipment for processing mixed plastic waste consisting of a collector for recovering hydrogen chloride (HCl) from gas products.