JPH115868A - Recycling system of waste polystyrene resin by method for dissolving and decomposing to oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a recycle system of waste polystyrene by a method for dissolving and decomposing into oil. SOLUTION: Dissolving, melting, thermal decomposition of waste polystyrene into oil and light oil/heavy oil-separation of pyrolytically produced oil are carried out by effectively combining a simple screw machine, a thermal degradation tank (with an agitator and an electric heater) and a heat exchanger. The light oil having high dissolving ability to the polystyrene resin is used as a solvent and the light oil is used as a heat source for carrying out the melting and thermal decomposition by gasifying the light oil at a high temperature and directly contacting with the waste polystyrene. A multipurpose apparatus capable of carrying out a continuous separation of the light oil, which is a solvent, from the polystyrene resin and pelletizing the resin is provided by further adding a vacuum pump, a screw for discharging from the bottom of the thermal degradation tank, a cooling tank and a pelletizer. This apparatus is used as a core and dissolved waste polystyrene is recovered to the spot where the apparatus locates by putting the solvent (the light oil) obtained from the apparatus into a dissolving tank with a deodorizing device installed at a spot of occurrence of waste polystyrene to dissolve the waste polystyrene.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application field] The present invention installs a dissolving tank containing this solvent in a market, a factory, a supermarket, etc., where waste polystyrene (foams, trays, containers) is generated. , Dissolve at room temperature on the spot, collect and transport highly viscous solution with trucks, etc.,
The solvent and polystyrene resin are separated by a solvent recovery device (also used for oiling) installed in the factory, and the solvent is reused as it is. Also, the polystyrene resin relates to a series of equipment for processing into pellets or molded products and a recycling system (see FIG. 3).

[Prior Art] As a waste polystyrene treatment method, 45% is not recycled (incinerated and landfilled), and 55% is recycled by material reuse, melt solidification, and pelletization. Among them, melt solidification accounts for 80%. Polystyrene resin has thermoplasticity, so it becomes soft and melts when high heat is applied. Heating methods include steam, hot air, direct heating, and infrared friction heating. As a method close to the present invention, there is a solvent method. Waste polystyrene is dissolved by utilizing the property of dissolving it well in styrene, which is a raw material, and it is evaporated and thermally decomposed by giving it at 38 ° C. and a residence time of 3 to 4 hours.
In addition, a method of liquefying (styrene liquefaction) through a catalyst. All fractions of the product oil are used as solvent. The mainstream of the waste polystyrene treatment method is to install equipment in places where melting and solidification frequently occur, and have them receive ingots with low product value. Originally, we would like to sell high value-added virgin pellets, but waste polystyrene contains many foreign materials (metals, aluminum, paper labels, stones, other resins, etc.), which hinders the process of processing into pellets of several millimeters. I will. In order to remove them, expensive equipment and a large number of people are required, and there is no economic efficiency in the current method. As another solvent, citrus vegetable essential oil "d-limonene" and mineral oil are used.

[Problems to be Solved by the Invention] To list the problems of the conventional method: 1) Styrofoam containers have a very small bulk specific gravity. If they are to be treated without volume reduction, they have a large storage area and high transportation (such as carrying air). )There will be a cost. Melting and solidifying equipment generally involves intensive processing because of the labor, time and energy loss that occurs during startup. Therefore, a large storage space until processing is required.

2) Use of the entire fraction (including heavy oil) of the pyrolysis or catalytic cracking product oil of waste polystyrene as a solvent lowers the dissolving capacity, increases the cost of solvent recovery, and increases the cost of recovering the polyethylene resin. Reduce quality.

3) When dissolving the waste polystyrene with another solvent (d-limonene), it is necessary to heat the polystyrene to 100 to 150 ° C., and the place where the polystyrene is dissolved is limited for safety. Also, other solvent costs are significantly higher than in the present invention.

4) Manufacturing high value-added virgin pellets after melting and solidifying waste polystyrene requires a great deal of pretreatment (sorting, crushing, foreign matter removal, washing and drying), and is not economically viable at present. Further, since the conventional melt-solidification is performed at a high temperature, the molecular weight of polystyrene is greatly reduced, so that the product has a very low grade.

5) It is not economically feasible to always rely only on thermal decomposition without recovering (not recycling) the solvent, which results in high operating costs.

6) Only the places where waste polystyrene is constantly generated abundantly are processed by the liquid consolidation equipment, but in places where only a small amount of waste polystyrene is generated, industrial waste traders pay high disposal costs (high transportation costs) to collect them. I have. That is, since there is no ultra-small melter, the waste polystyrene recovery efficiency at the place where a small amount is generated is low.

7) When making virgin pellets or molded products by conventional methods,
Use expensive extruders to melt.

8) In the case of thermal decomposition oil conversion of waste polystyrene, long-term stable operation is difficult due to coking problems in the heating furnace tube. In addition, many of them are indirectly heated, resulting in poor efficiency and difficult scale-up.

9) The problem of malodor such as styrene odor has not been solved in the melting and oiling process of waste polystyrene.

As described above, an object of the present invention is to solve all the problems of the related art.

[Means for Solving the Problems] 1) It is well known that a thermally decomposed oil of polystyrene dissolves polystyrene, but this method uses a light oil (distillation range 130 ~ 170
° C, specific gravity 0.850), and light oil is used as a solvent. The separation method employed an evaporative heat exchanger without a distillation column.

2) In order to increase the charging rate of the polystyrene foam, after dissolving with a solvent (0.7 KG polystyrene is dissolved in 1 L of solvent), dissolve until it becomes colloidal, and feed it to a screw machine via a pump.

3) Waste polystyrene contains many foreign substances (paper, fish, stone, aluminum, etc.), so it is subjected to a two-stage treatment with a strainer (first time in a dissolution tank and second time before screw injection).

4) Heat is supplied to the screw machine by blowing light oil vapor at about 350 ° C. from the side of the screw. The screw is a multiple type, and the rotation direction is outward rotation by a gear, and the shape is preferably a ribbon screw. The length of the shaft is about 2M. The resin temperature is heated to about 230 ° C.

5) The heated and melted polystyrene resin and light oil are flushed to a vacuum pyrolysis tank and separated into polystyrene resin and a solvent (light oil). The polystyrene resin is mixed and reheated by an electric heater and a stirring blade provided at the bottom of the pyrolysis tank, and the solvent dissolved in the polystyrene resin is almost separated and about 97% is recovered.

6) The separated solvent is heat-recovered by a heat exchanger and liquefied by a cooler and recycled. If the solvent is insufficient, the resultant is given at 380 ° C. for 4 hours with an electric heater in a pyrolysis tank to obtain pyrolysis oil, which is roughly separated into light oil / heavy oil by an evaporative heat exchanger.

7) The high temperature gas blown into the screw machine is obtained by heating the light oil with a heat exchanger and a heating furnace after increasing the pressure of the light oil with a pump. At this time, an evaporative heat exchanger is provided to prevent pulsation and coking in the tube, and the heating furnace inlet is considered to be completely vapor (no phase change). Since the fluid is light oil, the coking problem can be solved even with a high-temperature gas of 500 ° C.

8) Since the malodorous substance is concentrated in the pyrolysis gas, it is incinerated and deodorized in a heating furnace.

9) A polystyrene resin at the bottom of the pyrolysis tank is provided with a perforated plate at the outlet of a simple screw machine, extruded in a string form, quenched in a cooling tank, cut into a length of 3 to 5 MM with a pelletizer, and formed into pellets. In the case of an ingot, remove the perforated exit plate and drop it directly into the cooling tank.

10) The present apparatus uses a slide input machine to melt and dissolve waste polystyrene in contact with a 400 ° C. high-temperature gas without making it colloidal.

11) The dissolution tank has the structure shown in Fig. 1. When the inlet is opened as a countermeasure against odor, the small blower starts automatically, sucks air and odor gas, and the gas is cooled by a refrigerator to condense and separate odor components. When producing resin pellets, the colored polystyrene must be sorted out in the dissolving tank in order to reduce the quality value. There is no problem even if the colored polystyrene is mixed in the case of manufacturing a molded article using a colorant in an injection molding machine.

[Effects of the Invention] 1) Immediate dissolution at the place where it occurs reduces the accumulation area.

2) The raw material of the solvent is waste polystyrene. The oiling mode, which requires an operating cost, is a solvent recovery mode (only at a temperature of 230 to 250 ° C. evaporating operation) in which only the initial solvent securing and replenishing is performed and no operating cost is required. In the thermal decomposition mode, one batch requires 6 hours, but in the solvent recovery mode, it can be done in 3 hours. Solvent production costs are lower.

3) The solvent dissolving ability dissolves 0.6 kg of polystyrene per liter of solvent only by thermal decomposition, and dissolves 0.7 kg by thermal decomposition / catalytic decomposition. Transport efficiency is not different from melting.

4) The operating conditions of the dissolution tank installed in the place where it occurs are normal temperature (no heating equipment required), normal pressure, and sufficient measures against fire and odor are taken. Since this solvent is adjusted to a flash point of 35 ° C. or higher, the Fire Service Law corresponds to the second petroleum.

5) Foreign matter (metal, aluminum, paper,
Sand, stone, glass, vegetables, fish, meat, other resins, etc.). Naturally, the person who puts it into the dissolution tank has to be careful in removing foreign matter, but even if it is mistakenly introduced, polystyrene will dissolve in a solvent in a short time and become a highly viscous solution. Since there is no change, most of the foreign matter is removed by passing through the strainer, and only the solution (solvent + polyethylene) is introduced into the screw machine. That is, in the conventional method, crushing, foreign matter separation,
Sorting, washing, and drying steps were required, but in the present invention, all of the above steps can be eliminated by treating them as a solution. Virgin pellets (excluding colored polystyrene), which are high value-added products, can be economically manufactured.

6) When the waste polystyrene is converted to oil, pretreatment equipment (crushing and volume reduction) is required, but the present invention does not require any such equipment, and is very economical.

7) The distillation range of the solvent is as low as 130 to 230 ° C for thermal decomposition only 130 to 190 ° C for pyrolysis and catalytic cracking. Therefore, the solvent can be recovered at low temperature.
At ~ 250 ° C, the recovery rate approaches 100% by reducing the pressure by about 90 wt% pressure. Since light solvents are separated at a relatively low temperature (no distillation operation), solvent recovery costs are low, and thermal degradation to polystyrene resin can be minimized.
The quality of the final product pellets or molded products is good. In addition, the equipment cost is low and efficient because one apparatus serves both oil conversion (pyrolysis), solvent recovery and pellet production.

8) Since the dissolving tank installed at the place where the dissolution occurred has a simple structure, it can be easily manufactured from ultra-small to large. In particular, it can be installed in any place where waste polyethylene resin is generated, and as a result, the recovery rate of waste polystyrene is remarkably improved as compared with the conventional method.

9) If the waste polystyrene recycling system of the present invention is constructed and expanded nationwide, economies of scale will work, and the processing costs for markets, factories, supermarkets, etc. will be significantly reduced. In addition, since the amount of foams and containers in the garbage discharged from the home is reduced, the bulk density of the garbage is increased, and the transport effect is improved.

10) In the conventional method, when manufacturing virgin pellets and molded articles, an expensive extruder is used for melting. However, in the present invention, the temperature of the solvent recovery tank is about 230 ° C. and the polystyrene resin is completely melted. Do not require an extruder. A simple screw machine is sufficient.

11) The heat donation of the present method is easy to scale up because the hot gas is brought into direct contact with the resin. No problems such as coking occur in the process of producing the high-temperature gas. Because the fluid is light oil, a reflux heat exchanger (with evaporator) is installed to prevent pulsation, and the inside of the heating furnace tube is completely vaporized at the inlet so that there is no phase change. Driving is stable.

12) When waste polystyrene is melted and thermally decomposed, styrene odor is generated, but it is not a problem because it is treated completely closed and gas containing odor is incinerated and deodorized in a heating furnace.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram of an apparatus suitable for carrying out the method of the present invention. Waste polystyrene (foamed products / containers) generated in markets, factories, supermarkets, etc. is put into a dissolving tank 101 with a deodorizer, which is half filled with a solvent, by employees who can roughly sort. When the solution in the dissolving tank becomes colloidal, the solution is loaded on the truck through a pump and a strainer 102 provided in the truck (installation of the solution tank and the solvent tank). Next, the solvent is half-filled from the truck into the dissolution tank. The truck loaded with the solution goes to a factory (solvent recovery device), where the foreign matter is removed again by the strainer 105 and then introduced into the screw machine 106 by the feed pump 104. When the solvent is insufficient, the operation is performed in the thermal decomposition mode. However, since the operation is usually in the solvent recovery mode, the operation will be described below in this mode. The pyrolysis tank 108 includes a stirrer 110 and an electric heater 111 and operates at about 230 ° C. under vacuum. The heating source of the screw machine uses the same fraction as the solvent as the heating furnace feed pump 1
At 17, the heat is fed to a heating furnace 118, the temperature is raised to 300 to 330 ° C., and blown directly from the side surface 109 of the screw machine to provide heat supply and a stirring effect. The distillation range of the solvent is 130-2
Since the temperature is 30 ° C, considerable solvent evaporates at normal pressure,
In order to achieve as close to 100% recovery as possible, the pyrolysis tank is reheated with an electric heater while stirring under vacuum. The oil content in the polystyrene resin in the pyrolysis tank is below the allowable value. After the separated light oil gas is recovered in the heat exchanger 112, it is cooled to become a liquid and recycled. A part of the solvent is heated to 330 ° C. in the heat exchanger 112 and the heating furnace 118 and is blown from the side of the screw machine. The pyrolysis gas and odorous substances are sucked by the blower 124 and burned in a heating furnace. Light oil and water are separated by the difference in specific gravity.
Heavy oil is used as fuel for heating furnaces. The polystyrene resin of about 230 ° C. remaining in the pyrolysis tank is extruded in a string form through a perforated plate 121 attached to the screw outlet. It is solidified in a cooling tank 122, and this is pelletized by a pelletizer 123.
And cut into 3-5 mm lengths, sent to the hopper, packed in bags and shipped.

[Brief description of the drawings]

FIG. 1 is a model diagram showing a preferred embodiment of a waste polystyrene dissolving tank of the present invention.

FIG. 2 is a model diagram showing an example of waste polystyrene of the present invention.

FIG. 3 is a diagram of a waste polystyrene recycling system.

[Explanation of symbols]

 101. Dissolution tank 101-a. Input port 101-b. Freezing separator 101-c. Suction blower 101-d. Solvent return tube 101-e. Input port open / close switch 102. Strainer 1 103. Stock tank 104. Feed pump 105. Strainer 2 106. Screw machine 107. Sliding input machine 108. Pyrolysis tank 109. Screw machine hot gas injection port 110. Stirrer 111. Electric heater 112. Evaporative heat exchanger 113. Cooler 114. Light oil receiving tank 115. Heavy oil receiving tank 116. Pyrolysis gas tank 117. Heating furnace feed pump 118. Heating furnace 119. Fuel oil supply pump 120. Pyrolysis tank bottom screw machine 121. Perforated plate at screw machine outlet 122. Cooling tank 123. Pelletizer 124. Suction blower a Light oil b Heavy oil c Residue d Pellet o Ingot

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[Procedure amendment]

[Submission date] January 5, 1998

[Procedure amendment 3]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG. 1

FIG. 2

[Figure-3]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10G 1/10 ZAB B09B 3/00 302A 303E

Claims (2)

[Claims] 1. Melting, melting and pyrolysis of waste polystyrene (especially foreign matter and dirty polystyrene) by effectively combining a simple screw machine, a pyrolysis tank (with a stirrer and an electric heater), and an evaporative heat exchanger. And separation of light oil / heavy oil of the pyrolysis product oil. Light oil having high dissolving ability in polystyrene resin is used as a solvent, and the light oil is gasified at a high temperature and used as a heat source for melt pyrolysis by direct contact with waste polystyrene. In addition, a vacuum pump,
A multipurpose device capable of continuously separating and pelletizing the solvent and polystyrene resin by adding a screw for extracting the bottom of the pyrolysis tank, a cooling tank, and a pelletizer. 2. Using the apparatus of claim 1 as a core, a solvent (light oil) obtained therefrom is transferred to a dissolving tank with a deodorizer provided at a market, a factory, a supermarket or the like where waste polystyrene is generated. The waste polystyrene is put into a dissolving tank at a half filling and kept at room temperature, and dissolved until it becomes colloidal. Foreign matter in the solution is removed by a strainer, loaded on a truck, transported to the apparatus of claim 1, and separated into a solvent and a polystyrene resin by the apparatus. About 97% of the solvent is recovered and recycled. The polystyrene resin becomes a pellet or an ingot. A series of these recycling systems, highly efficient solvent recovery methods and dissolution tank facilities.