JPH0691649A - Method and device for processing waste plastic - Google Patents

Abstract

PURPOSE:To recycle light oil of high quality as a fuel by a method and device wherein cracked gas is suitably retrieved by supplying intake pressure and negative pressure to the inside of a heating furnace under a condition of melting temperature of waste plastic and the retrieve is performed by classifying into waste plastic of molten residue and kneaded matter generated due to caking of incinerated ashes. CONSTITUTION:Cracked gas is sucked, filtered by a gas-liquid separating filter pot 9a, cooled by a cooler 10 so as to change to oil, and returned to an oil separating tank 11 as oil. As for sucking and retrieving quantity of the cracked gas, constant sucking time is detected by a timer or oil quantity in the oil separating tank 11 is detected, and a suction fan 12 is controlled. The cracked gas which can not be changed to oil burns as a fuel at a heating furnace 16a so as to be a heating source. Separated oil is stored in an oil product tank as occasion demands as a replenishing fuel in the heating furnace. Molten residue of retrieved optional cracked gas opens a shielding damper 7, it is discharged being kneaded by a recovery screw feeder 8, retrieved into a cooling tank 18, crushed into optional size by a crusher so as to make soil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating and reusing wastes, and in particular, it collects useful light oil from polyolefin plastics among waste plastics that are difficult to dispose of as appropriate. The present invention relates to a method and an apparatus for recycling and incinerating ash to be landfilled as final disposal and a molten residue of the waste plastic to be solidified and solidified to be pollution-free as soil.

[0002]

2. Description of the Related Art In recent years, Japan has become more affluent with economic development and the diversification of lifestyles and industrial structures has led to an increase in the amount of waste generated. The quantity and quality change greatly, complicating the waste management problem. In particular, the use of plastics has expanded rapidly from food packages and various containers to home electric appliances, etc., and a large amount of plastics have been discharged as waste. Many problems have been pointed out, such as the fact that plastic does not rot even when it is landfilled, the ground in the landfill is not stable, and when incinerated it becomes hot and damages the incinerator and discharges harmful gases. Therefore, various processing techniques have been developed for processing plastics. For example, processing techniques for plastics alone or mixed wastes such as melt solidification recycling, pyrolysis oilification, high temperature melting, melt solidification volume reduction, incineration residual heat recovery utilization have been studied and developed. These technologies are described in detail in the "Technology Guidebook for Waste Plastic Processing and Resource Recycling Technology" published by Japan Plastics Processing Promotion Association (March 1989).

On the other hand, the mainstream of waste treatment in Japan is incineration, and most of the general waste collected by local governments is incinerated. Since there are few landfills, the actual situation is that the volume is reduced to the maximum by incineration. However, if incinerated, exhaust gas, wastewater treatment, or incinerated ash of the incineration residue is landfilled, but ash scattering by wind, runoff by rainwater and secondary pollution due to elution of harmful substances and heavy metals contained in ash, etc. There is concern about the danger.

Although the final disposal is landfill, there are various problems. In addition, the increasing amount of industrial waste has led to a tight landfill site, which often causes illegal dumping, which is a social problem. Due to this situation, many inventions relating to waste plastic processing have been published. For example,
"Waste Incinerated Ash Solids and Their Manufacturing Method" (Japanese Patent Publication No. 1-2
54285), "Waste melting treatment method" (Japanese Patent Publication No. 57-74513)
No.), “Plastic waste treatment method” (Japanese Patent Publication No. 61-78847), and several inventions relating to melting treatment of waste plastic and incineration ash and oilification from waste plastic have been disclosed. However, these inventions relate to a method for producing a molded solidified product by melting oil or plastic and incineration ash, and there is no reference from the viewpoint of having both of them.

[0005]

The treatment of the waste plastic and incineration ash has the following problems.

Difficulty in processing The amount of plastics discharged as waste has increased in recent years, and various processing techniques have been developed. As for the treatment technology, there is a method in which it is heated and melted and reused as a volume-reduced molded solid matter, but the technical trend seems to be the mainstream is oiling technology from melting and decomposition gas.

[0007] In municipalities, whether to dispose of waste plastic as burnable waste or non-burnable waste must be dealt with depending on the conditions of the incinerator and the landfill site, which is a problem.

Landfilling waste plastic as it is will not rot and the ground will not be stable, and the bulkiness will accelerate the shortage of landfill.

[0009] Volume reduction and processing of molded solids are expensive, the market for reuse is small, and they are finally incinerated or landfilled.

[0010] In the oil technology, the recovered oil has problems such as tar and oil quality, and reforming with a catalyst has been developed.
There are development issues such as catalyst life.

[0011] In the plastic baking, the heat resistance of the furnace becomes a problem because the temperature of the furnace becomes a few hundreds of degrees when burned because the plastic has a high calorie.

As described above, the mainstream of waste treatment is incineration, but as the amount of treatment increases, naturally, incineration ash also increases. The disposal is mainly landfill, but it is scattered by the wind and is discharged as rainwater.

Pollution of soil and groundwater by elution of harmful substances and heavy metals contained in incineration ash, environmental pollution by various inorganic and organic pollutants contained in combustion exhaust gas and wastewater.

There is a problem of. Therefore, the treatment technology is (a) solidification of concrete: it has been put to practical use as a solidification technology for burying harmful substances such as mercury and cyan, but it is necessary to optimize the type of cement, mixing ratio, kneading method, and molding method. Therefore, it cannot be said that there are many uses.

(B) Ash melting: The incineration ash is melted at high temperature and cooled and solidified. Hazardous substances and the like are also trapped in the solidified material, and have a wide range of applications such as construction materials such as cement and substitution of sand for road construction. As a melting method, there are electric resistance, electric arc, electric microwave melting method, etc., but since ash is melted at a high temperature, for example, power consumption is 700 to 1,000 KWh / T.
The cost is considerably high, for example, ash is required.

The object of the present invention is to treat difficult-to-treat plastic and incineration ash at the same time, recover good quality light oil from the plastic, and solidify the plastic melting residue and incineration ash to suppress secondary pollution. It is intended to provide a method and an apparatus for converting into soil.

[0017]

In order to achieve the above object, the present invention is to reduce the pressure at the melting temperature of plastics.
By paying attention to the fact that light decomposition gas is generated from plastic when forced intake is performed, it is possible to combine both known oil processing and melting processing technologies. With collecting
It is intended to provide a method and an apparatus for obtaining a solidified and solidified material obtained by kneading a molten residue of plastic and incinerated ash as soil.

As a result, good quality light oil can be used as a fuel, and recycling can be achieved. In addition, the caking solidified product of the molten residue of the plastic and the incinerated ash of the inorganic substance greatly suppresses the elution of harmful substances in the incinerated ash, and since the plastic molten residue partially carbonizes, it becomes a soil with excellent water retention. Can be reused.

[0019]

[Function] The current oil recycling system for waste plastic is 28
In a melting tank heated to 0 to 340 ° C., a method in which plastic is melted, then supplied to a thermal decomposition tank and thermally decomposed at around 400 ° C., and the decomposed gas is cooled and oiled to recover oil is the mainstream. However, the obtained oil is in the form of wax or tar, and there is a problem in reusing it as a fuel. Therefore, a method has been proposed in which cracked gas is reformed with a catalyst to produce light oil (Japanese Patent Publication No. 178195/1988).
-29492).

The present invention has been made in the basic experiment of thermal decomposition and oilification of waste plastics by paying attention to the fact that when plastics are melted and the inside of the container is sucked and decompressed, decomposition gas is easily generated at the melting temperature. is there. In the experiment, the material (polystyrene: PS) used in the waste refrigerator was crushed into 10 to 20 mm pieces for use. PS melts at 250 to 280 ° C. and becomes liquid, and decomposition gas is generated at around 300 ° C. However, when suction and decompression are performed in the container, generation of decomposition gas becomes active under the same temperature condition. Further, observing the change over time in which the inhaled decomposed gas is liquefied through the cooler, the oily property when the generated gas in the early stage of inhalation is oiled is light brown and has high fluidity.
When the intake is further continued, the oil obtained gradually changes from brown to black in color and becomes more viscous. It is considered that the light fraction is preferentially gasified by intake air, and the oil in the early stage of oiling is a good quality light oil and does not require reforming by a catalyst. On the other hand, the kneaded product of the molten plastic residue and the incinerated ash when the plastic and the incinerated ash are mixed, since the incinerated ash is bound by the molten plastic, it can be crushed to an arbitrary size after cooling and used as soil. here,
It should be noted that when the decomposition gas is excessively generated, the viscosity of the molten residue becomes high, and at the same time, the caking degree of the incineration ash decreases. In the experiment, the weight ratio of plastic to incinerated ash was 1: 0.3, and the recovery amount of oil was 30 to 50w based on the weight of the plastic sample.
About t% was suitable. A schematic diagram of the soil obtained in this way is shown in Fig. 3. When crushed to a particle size of 2 to 3 mm, plastic and incineration ash were problems when they were used alone, but runoff, scattering, and landfill The problem of ground stability of the ground can be solved. In particular, harmful substances and the like eluted from the incineration ash are significantly suppressed by being bound by the plastic melting residue. Furthermore, by controlling melt decomposition appropriately, most of the melt residue is carbonized, and it can be used as a high-quality soil having both porous water retention and hydrophilicity of incineration ash. That is, the present invention is to recover only high-quality light oil from waste plastic and recycle it, and use the kneaded product of the molten residue and incinerated ash as the improved soil.

[0021]

Embodiments will be described below with reference to the drawings.

FIG. 1 shows a device configuration of an embodiment of the present invention. The mixing hopper 3 for mixing and preheating the plastic piece 1 and the incineration ash 2, the supply screw feeder 4 for supplying the mixture 3a, the closed furnace 6 and the recovery screw feeder 8 for discharging the kneaded material 6a are the main device configurations. Shielding dampers 5 and 7, an oiling device, and an exhaust gas treatment device are attached to the inlet side of each screw feeder.

Although not shown, the mixing weight ratio of the thermoplastic plastic pieces 1 and the incineration ash 2 (not shown) crushed to an arbitrary size in the crushing step is 1: 0.1 to 0.7, preferably 1 : 200 to 200 in the hopper 3 at a ratio of 0.2 to 0.3
When the mixture is stirred and mixed by the stirring blade 3a while preheating at ˜250 ° C., the plastic is softened, the surface is melted, and the incinerated ash 2 is attached to the dumpling. When vinyl chloride resin (PVC) is mixed in the plastic as the feedstock, PVC has a low melting point, and most of it decomposes and gasifies at the stage of stirring and mixing by preheating at 250 ° C, and the gas is mixed in the hopper 3
Impurities entrained by the gas-liquid separation filter 9a are separated from the upper part, a gas containing chlorine is introduced into the off-gas cleaning device 17, and chlorine is dissolved and absorbed by water cleaning and then exhausted.
After that, the shielding damper 5 is opened, and the dumpling-shaped plastic is supplied to the closed furnace 6 while being kneaded by the supply screw feeder 4. Therefore, scattering of incinerated ash in the feeder and closed furnace is small. The closed furnace 6 is heated to 250 to 400 ° C., preferably around 300 ° C., stirred so that the molten plastic mixes well with the incinerated ash, and the inside of the closed furnace is sucked by the suction fan 12 to a negative pressure. As a result, the generated decomposition gas is sucked, filtered by the gas-liquid separation filter pot 9a, cooled and oiled by the cooler 10, and collected as oil in the oil / water separation tank 11. The amount of suction / recovery of the decomposed gas is controlled by a timer for a certain suction time or by detecting the amount of oil in the oil / water separation tank 11 to control the suction fan 12. The decomposed gas that is not liquefied burns as fuel in the heating furnace 16a and is used as a heating source. The separated oil is stocked in the oil product tank as well as the refueling fuel for the heating furnace. On the other hand, the melted residue in which any decomposed gas is collected is opened by opening the shielding damper 7, discharged while being kneaded by the collecting screw feeder 8, collected in the cooling water tank 18, and crushed to an arbitrary size by a crusher to be soil. . Although not shown, it is also possible to provide a molded metal piece at the end of the recovery screw feeder to form a molded solid material. The present invention is
Although it was described on the premise of batch processing, continuous operation is possible depending on the agitating and mixing in the hopper 3 and the supply state in the feeder 4, but in consideration of the fact that the pressure is reduced and suctioned, intermittent continuous processing is performed by a fixed amount. Driving is preferred.

FIG. 2 is a diagram showing the construction of an apparatus whose main purpose is to knead and soil the screw feeder with a temperature gradient. A fixed amount of plastic pieces 1 and incinerated ash 2 are supplied to the hopper 16a,
Mix. The shut-off dampers 5 and 7 are opened, and the mixture is fed by the screw feeder 4 to the hopper 16b. The screw feeder 4 is heated and controlled at 200 to 250 ° C. by the heater 20, and is heated and kneaded in the feeding process. At this time, at the discharge port of the screw feeder 4, the chlorine gas generated by mixing the vinyl chloride resin is removed through the filter pot 9b and the gas cleaning device 15 and exhausted as in the embodiment. When a certain amount of heat is supplied, then the shut-off damper 7
Closed, suction air is taken in by the suction fan 12, and the heaters 21, 2 are closed.
2 and heat to 280-320 ℃, screw feeder 8
To supply a kneaded product, suck the decomposed gas generated here, filter through the filter pot 9a, and cool with the cooler 10.
Liquefy. The kneaded material is stored in the hopper 16c, and the shut-off damper 7a is appropriately opened to cool and crush it to obtain soil.

[0025]

The present invention has the following effects.

(1) Plastics and incinerated ash, which are difficult to dispose of in industrial waste, can be treated at the same time.

(2) Good quality light oil can be recovered from plastics and recycled as fuel. (3) The kneaded product of the molten residue can be used as soil, and when it is landfilled, toxic substances are less eluted, and environmental pollution such as secondary pollution can be suppressed.

[Brief description of drawings]

FIG. 1 is a system diagram of an apparatus that is an embodiment of the present invention.

FIG. 2 is a system diagram of an apparatus that is another embodiment of the present invention.

FIG. 3 is an explanatory view of carbonized soil.

[Explanation of symbols]

1 ... Waste plastic, 2 ... Incinerated ash, 3 ... Mixing hopper,
4 ... Supply feeder, 5, 7 ... Shutoff damper, 6 ... Closed furnace,
8 ... Collection feeder, 9a, 9b ... Filter pot, 10
... Cooler, 11 ... Oil-water separation tank, 12 ... Suction fan, 13
... oil tank, 14 ... heating furnace, 15 ... off-gas cleaning device.

Claims (8)

[Claims] 1. A method of melting waste plastic by mixing waste plastic and incinerated ash and heating the mixture in a heating furnace, wherein the inside of the heating furnace is subjected to suction / negative pressure under the melting temperature condition of the waste plastic. A method for treating waste plastics, characterized in that the decomposed gas is appropriately recovered by means of the method, and the waste plastics as a molten residue and the kneaded material in which the incinerated ash are caking are separated and recovered. 2. The processing apparatus for waste plastic according to claim 1, wherein the heating furnace is a closed type, and the decomposed gas is sucked outside the furnace to be cooled / liquefied and recovered as oil. 3. The kneaded material obtained by caking and solidifying the molten plastic and the incinerated ash according to claim 1, is kneaded from a closed furnace by a conveying device using a screw feeder, discharged and collected, and appropriately cooled and crushed to obtain soil. Equipment for processing waste plastic for reuse. 4. The process according to claim 1, wherein waste plastic and incineration ash are preheated by a mixing hopper, and a step of supplying the mixture to a closed furnace by a screw feeder and heating the mixture, the waste plastic is melted and kneaded with the incineration ash. Steps and steps of forcibly inhaling the decomposition gas of the waste plastic, cooling and oiling, and discharging the caking kneaded product of the residual molten plastic and the incinerated ash from the closed furnace by the screw feeder Plastic processing system. 5. The reduced pressure from the heating furnace according to claim 1,
A treatment system for waste plastics, which controls recovery of the decomposed gas under negative pressure by detecting from a fixed intake time or a cooled oilification amount. 6. The method for treating waste plastic according to claim 1, wherein the heating and melting temperature in the closed furnace is 250 to 400 ° C. 7. The method for treating waste plastic according to claim 1, wherein the mixing weight ratio of the waste plastic and incineration ash is 1: 0.1 to 0.7. 8. The method according to claim 1, wherein the inside of the heating furnace is pressurized with an inert gas at a constant pressure, and excess gas due to generation of decomposition gas under the melting temperature condition of the waste plastic is appropriately recovered, and the waste residue is discarded. A method for treating waste plastic, in which the plastic and the kneaded material in which the incinerated ash is caking are separated and collected.