JPH0971684A - Recovery of oil from waste plastics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably reduce the load on a pretreating fractionation step by allowing the intrusion of thermosetting resins and other solid foreign matters without causing troubles. SOLUTION: Oil is recovered by thermally decomposing a waste vinyl chloride plastics or other chlorine-containing waste plastics. A treated mixture of the waste plastics and sand essentially free from chlorine is produced by placing, before the thermal decomposition step, a process for extruding the waste plastics, mixing the flow of the waste plastics with high-temperature sand and/or additive and heating at 250-350 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering oil from waste plastics by pyrolysis, and more particularly to a method for converting waste plastics separated and collected in municipal waste or collected as industrial waste into oil. To reuse as fuel.

[0002]

2. Description of the Related Art Conventionally, to obtain oil from waste plastic, a carbon skeleton is cut at a temperature of about 400 ° C. to reduce the molecular weight and liquefy. In this method, about 500-
Energy of 1,000 kcal / kg (plastic) is required. As a method of applying this energy to plastic, there is a method of circulating molten plastic by a pump and applying energy by a heating furnace provided in the middle.

Further, in this method, it is necessary to completely remove the thermosetting resin and solid foreign matter in the pretreatment step in order to avoid troubles in the pump circulation line.
The cost was large and the economy was problematic.

Further, the oil obtained by decomposing only by heat is unstable and causes a trouble of caulking on the inner wall surface of the tube of the heating furnace.

Further, even in a thermoplastic resin, a part of carbonaceous residue is produced by thermal polycondensation, but these are suspended in a pump circulation line and separated by solid-liquid separation by filtration or centrifugation. Although it is collected, some oil is inevitably mixed, resulting in oil loss. Moreover, the recovered carbonaceous residue is a valuable energy source, but it is not effectively used.

Further, since these liquid oils are solidified at room temperature, the pump circulation line needs to keep the steam jacket and the like warm, and the process line must be replaced with heavy oil or the like at the time of start-up and shutdown, resulting in an increase in operation and maintenance costs. Connected to.

[0007]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a method which does not cause a trouble even when a thermosetting resin or solid foreign matter is mixed in, thereby increasing the load of the pretreatment separation step. It is intended to provide an oil recovery method that reduces the width. Another object of the present invention is to provide a method for suppressing coking trouble in the process of applying energy to waste plastic, and for effectively utilizing solid pyrolysis residue as a heat source without separating it. Further, another object of the present invention is to
A method for easily starting and shutting down a method of recovering oil from the waste plastic by thermal decomposition is provided. Yet another object of the present invention is to provide high boiling oils with low boiling points.

[0008]

As a result of intensive studies, the present inventors have found the following method as a means for solving the above problems. That is, when recovering oil from waste plastics containing vinyl chloride and other chlorine by thermal decomposition, the waste plastics are mixed with high temperature sand and / or additives while extruding and flowing the waste plastics before the thermal decomposition step. The first feature is that a step of producing a treated product composed of a mixture of waste plastic from which chlorine is substantially removed and sand by heating to a temperature of 250 to 350 ° C. is provided.

In addition, as a thermal decomposition step for thermally decomposing the waste plastic from which chlorine has been removed after the above-mentioned pretreatment or the waste plastic from which chlorine has been substantially removed due to its composition, it is mixed with high temperature sand and directly Heat to about 35
0-500 ° C, preferably about 400-480 ° C
The second feature is that the holding process is a thermal decomposition process in which the waste plastic is thermally decomposed.

Further, in order to effectively utilize the solid thermal decomposition residue after the thermal decomposition, the thermal decomposition derivative such as the solid thermal decomposition residue after the thermal decomposition is moved by air in the flow of sand. Combustion in a bed or high-speed circulating fluidized bed to produce high-temperature sand,
A third feature is that a part of the high-temperature sand is returned to the thermal decomposition step of the waste plastic or the chlorine removal step of the preceding step, and recycled.

In order to obtain a high-quality oil having a lower boiling point, the first thermal decomposition product obtained by the thermal decomposition process of waste plastic is used.
Gas-liquid separating means for separating the liquid high-boiling point oil into a gas low-boiling point oil and a low-molecular-weight gas, and returning the high-boiling point oil to the thermal decomposition step; and a second gas-liquid separating means for lowering the liquid low-boiling point oil. The fourth feature is that the step of separating oil and gas into low-molecular gas is connected in series.

Further, as a comprehensive system for recovering oil from waste plastics by thermal decomposition, the waste plastics are mixed with high temperature sand and heated to a temperature of 250 to 350 ° C. First step for producing a treated product comprising a mixture of plastic and sand, high temperature sand and / or additives are added to the treated product of the first step, and the temperature is about 350 to 500 ° C, preferably about 400 to Four
The second step of producing a thermal decomposition product consisting of a gaseous high boiling point oil, a low boiling point oil and a low molecular gas and a solid thermal decomposition residue / sand mixture by heating to 80 ° C., the second step heat The first gas-liquid separation means separates the decomposition product into a liquid high-boiling oil, a gas low-boiling oil, and a low-molecular gas, and a high-boiling oil is refluxed to the second step, a second gas-liquid separation. A separation step of separating into liquid low boiling point oil and gaseous low molecular gas by means, solid pyrolysis residue / sand mixture in the second step, and sand that fluidizes the low molecular gas of the second gas-liquid separating means with air. A method for recovering oil from waste plastics is proposed, which comprises combusting in a fluidized bed as a medium to produce high-temperature sand, and reusing a part of the sand for the first or second step.

In this case, the additive used in the second step is a catalyst for accelerating the decomposition of wax, and may be synthetic zeolite or natural zeolite, preferably natural mordenite.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail. The term “waste plastic” as used in the present invention refers to waste that contains a large amount of plastic separated from municipal waste, and is mainly composed of a thermoplastic resin (polyethylene, polypropylene, polystyrene, etc.) and partially polyvinyl chloride, PETs,
A thermosetting resin, paper, and foreign matter such as porridge may be mixed. Further, among industrial wastes, those containing a large amount of plastic such as residual plastic of plastic die-cast products are also included.

When chlorine is contained in waste plastic such as polyvinyl chloride, and when this is thermally decomposed to produce oil, the quality of the oil is deteriorated, which causes deterioration of the catalyst and corrosion of materials. Therefore, it is necessary to separate and remove in advance. Most of the chlorine in this waste plastic is derived from polyvinyl chloride and polyvinylidene chloride, and it is generally known that these chlorines are selectively separated and removed by heating at a temperature of 250 to 350 ° C. There is.

The present inventors have found that a method of directly heating with high temperature sand is preferable as a method of heating to a temperature of 250 to 350 ° C. The heat transfer area is the surface area of sand, and the waste plastic can be easily heated.
As a device for realizing such a dechlorination step (first step), it was also found that a structure in which waste plastic is extruded and flowed is preferable from the viewpoint of improving the dechlorination rate, and specifically, a rotary kiln is preferable. .

By the above method, the separated gas containing HCl as a main component is recovered with water or an alkali absorbing liquid. On the other hand, in the thermal decomposition step (second step), waste plastic is directly heated by high-temperature sand with a large specific surface area to raise and maintain the temperature at 400 to 480 ° C, thus transferring heat like a conventional indirect heat exchanger. It was found that troubles due to caulking on the heat side could be avoided.

In the case of the present invention, even if carbonaceous matter adheres to the surface of the sand, the sand is constantly flowing, and the sand with carbonaceous matter is burned in the third step (sand reclamation step). It was also found that trouble can be prevented in advance because it can be easily reproduced.

As a device for realizing the thermal decomposition step (second step) of the present invention, a fluidized bed or a stirring tank capable of uniformly mixing sand, additives and waste plastic is suitable. Specifically, the thermal decomposition step (second step) of the present invention is carried out with an additive.
A high temperature circulating sand of 00 to 950 ° C is mixed with a treated material (waste plastic) and the temperature is maintained at 350 to 500 ° C, preferably 400 to 480 ° C.

The additive 10 is a catalyst for further promoting the decomposition of the wax produced by the thermal decomposition of waste plastic,
Conventionally well-used in the petrochemical field, synthetic zeolite or natural zeolite, preferably natural mordenite. It has also been found by the present inventor that such an additive can simultaneously suppress coking due to a polycondensation reaction that occurs simultaneously with thermal decomposition.

Next, a low molecular gas in the thermal decomposition product generated in the second step, a low boiling point oil in a gaseous state (boiling point 250 ° C.)
High boiling point oil (boiling point 250 ° C. or higher) is taken out from the gas outlet line of the second step and cooled to about 200 to 250 ° C. by the first gas-liquid separation means to liquefy only the high boiling point oil,
It is preferable to circulate back to the second step from the reflux line.
The boundary temperature of 250 ° C. is 200
It can be freely set in the range of up to 400 ° C.

According to this method, the high-boiling oil is further heated in the second step under the additive, so that the high-boiling oil is further decomposed into the low-boiling oil, and the yield of the low-boiling oil is increased. It has been found that the quality and storage stability of oil are improved.

Therefore, in the present invention, the first gas-liquid separating means for separating the liquid high boiling point oil, the gaseous low boiling point oil and the low molecular gas, and the first gas-liquid separating means for separating the liquid low boiling point oil and the gaseous low molecular gas. Since the second gas-liquid separating means is connected in series, only the low molecular gas and the low boiling point oil can be obtained from the second gas-liquid separating means, and the second gas-liquid separating means cools to about 30 ° C. To obtain low boiling point oil and low molecular gas.

Next, the solid thermal decomposition residue (carbonaceous material) produced in the second step, the solid foreign matter, and the non-liquefied thermosetting resin are taken out by a screw feeder or the like and introduced into the third step 3, In the third step, air is introduced to form a fluidized bed using sand as a medium, the organic matter and the organic matter adhering to the sand are completely burned, and the temperature is kept at 500 to 950 ° C. Is recycled from the line 20 to the first and second steps.

As an apparatus for realizing the third step,
It has also been found that a bubbling fluidized bed or a high speed circulating fluidized bed is most suitable. Therefore, in the present invention, since sand is used as the fluid medium in all of the first, second, and third steps, if the solid content in the waste plastic is crushed to 100 to 200 mm or less, there is no trouble such as line blockage. Was issued. As a result,
It was also found that the pretreatment only requires crushing, and the separation can be omitted.

[0026]

Embodiments of the present invention will be described in detail below with reference to FIGS. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but merely illustrative examples. Nothing more.

Reference numeral 1 is a rotary kiln for performing dechlorination (dechlorination step), in which the waste plastic P supplied from the waste plastic supply line 6 and the circulating sand S heated at a high temperature of 400 to 950 ° C. are extruded and mixed, and the waste plastic is removed. Heat P to a temperature of 250-350 ° C. As a result,
About 95% or more of the chlorine in the waste plastic P is separated, and the gas containing HCl as the main component is taken out from the HCl rich gas extraction line 8 provided at the upper part of the kiln 1, and is recovered as water or an alkaline absorption liquid in an absorption tank (not shown). At the same time, the mixture of the circulating sand S and the dechlorinated plastic P (processed material in the first step) is supplied to the thermal decomposition step 2 through an extraction line 9 including a screw conveyor or the like.

According to the step 1, the heat transfer area is large as the surface area of the sand because it is directly heated by the high temperature sand, and the waste plastic P can be easily heated.

Pyrolysis step 2 comprises a stirring tank capable of uniformly mixing sand, additives and waste plastic P. Additive T supplied from additive supply line 10 and 500 supplied from circulating sand supply line 11. Circulating sand S with high temperature up to 950 ℃
Is mixed with the processed material in the first step supplied from the extraction line 9 to a temperature of 350 to 500 ° C., preferably 40
Thermal decomposition is performed while maintaining at 0 to 480 ° C.

As the additive T, synthetic zeolite or natural zeolite, preferably natural mordenite is used. In the thermal decomposition step 2, the waste plastic P can be directly heated by the high temperature sand having a large specific surface area in a fluidized state to easily raise and maintain the temperature at 400 to 480 ° C. Further, because of the fluidized bed or the stirring tank, even if carbonaceous matter is attached to the surface of the sand, the sand is constantly flowing, and is taken out from the pyrolysis residue mixture extraction line 17 and burned in the third step 3. Since it can be easily regenerated, caulking trouble can be prevented.

Next, in the thermal decomposition step 2, the first gas-liquid separating means 4 and the first through the thermal decomposition product withdrawing line 12.
Gas-liquid separation means Second through the uncondensed gas extraction line 13
The gas-liquid separating means 5 are connected in series. As a result, among the thermal decomposition products generated in the thermal decomposition step 2, low molecular gas, gaseous low boiling point oil (boiling point 250 ° C. or lower) and high boiling point oil (boiling point 250 ° C. or higher) are taken out from the line 12. Approximately 200 to 250 depending on the first gas-liquid separating means 4 such as a condenser.
Only the high boiling point oil is liquefied by cooling to 0 ° C., and the high boiling point distillate condensate reflux line 14 or line 12 returns to the pyrolysis step 2 for circulation. It was also found that by refluxing the high boiling point oil in the line, scale adhesion in the line 12 can be prevented.

By such a method, the refluxed high-boiling oil is further heated in the thermal cracking step 2, so that the high-boiling oil is further decomposed into a low-boiling oil, the yield of the low-boiling oil is increased, and the oil Quality and storage stability are improved.

Therefore, low-molecular gas and low-boiling point oil are obtained from the line 13, cooled to about 30 ° C. by the second gas-liquid separation means 5 such as a condenser, and cooled to a level lower than that of the low-boiling point condensed liquid extraction line 15. The boiling point oil O is obtained, and the uncondensed low molecular gas is sent to the residue incineration step 3 through the low molecular gas extraction line 16.

Next, the solid pyrolysis residue (carbonaceous material) generated in the pyrolysis step 2, solid foreign matter, and the non-liquefied thermosetting resin are discharged from the pyrolysis residue mixture extraction line 17 with a screw feeder or the like. It is taken out and introduced into the residue incineration process 3.

The residue incineration step 3 is composed of a high-speed circulating fluidized bed or a bubbling fluidized bed as shown in FIG. 2. As shown in FIG. 2, air A is introduced from the combustion air supply line 18 and sand is used as a medium. Form a floor and heat to 500-950
C., preferably 750-950.degree. C., line 17
Completely burn the organic matter in the inside, and by introducing secondary air from the line 180, the exhaust gas is heated to 850 to 950 ° C. to suppress the generation of dioxins and the like, and the exhaust gas G is discharged from the combustion exhaust gas extraction line 21. Take out and treat the exhaust gas as necessary.

On the other hand, the incombustibles F such as metal and glass which cannot be completely incinerated in the residue incineration step 3 are incombustibles extraction line 19
Take out from. Further, a part of the sand in the fluidized bed heated to 750 to 950 ° C. is put into the negative pressure pot 30 by gravity by the sand extraction line 20, and together with the air put into the intake section 301 from the air branch line 18 ′, The high temperature air, which is guided to the cyclone 32 through the sand removal line 20 and separated from the sand therein, is returned to the fluidized bed 3 through the return line 33, and is used for combustion of the fluidized bed and maintenance of the temperature of 750 to 950 ° C. .

Further, the sand separated by the cyclone 32 is put into the sand hopper 34 and recycled from the lines 11 and 7 to the dechlorination step 1 and the thermal decomposition step 2. It has been found that this method allows the hot sand to be easily recycled and is suitable for the present invention.

If the amount of heat of the circulating sand S is insufficient, a part of the oil O in the low molecular gas extraction line 16 or the low boiling point distillate condensate extraction line 15 is used as a fuel for the residue incineration process 3 if necessary. Can be used as

Therefore, in this embodiment, since sand is used as the fluid medium in all of the first step (dechlorination step), the second step (pyrolysis step) and the third step (residue incineration step), the solid type in the waste plastic P is It was also found that if the minutes were crushed to 100 to 200 mm or less, there would be no trouble such as line blockage.
As a result, the pretreatment only needs to be crushed, and the separation can be omitted.

[0040]

As described above, according to the present invention, regarding the oil recovery of waste plastics, the solid foreign matter-compatible type simplifies pretreatment separation, long-term continuous operation by suppressing coking,
It has the effects of simplifying start-up and shutdown, effective utilization of pyrolysis residue, and increased yield of high-quality oil with a low boiling point.

[Brief description of drawings]

FIG. 1 is a schematic view showing an oil recovery device from waste plastic according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a bubbling fluidized bed in a preferred embodiment of the third step according to the above embodiment.

[Explanation of symbols]

1 1st process (dechlorination process) 2 2nd process (pyrolysis process) 3 3rd process (residue incineration process) 4 1st gas-liquid separation means 5 2nd gas-liquid separation means 6 Waste plastic supply line 7 Circulating sand supply Line 8 HCl rich gas extraction line 9 First step treated product (mixture of sand and dechlorinated plastic) extraction line 10 Additive supply line 11 Circulating sand supply line 12 Thermal decomposition products (high boiling point oil, low boiling point oil, (Low molecular gas) extraction line 13 First gas-liquid separation means Uncondensed gas extraction line 14 High boiling point distillate condensate recirculation line 15 Low boiling point distillate condensate extraction line 16 Low molecular gas extraction line 17 Pyrolysis residue mixture extraction line 18 Combustion air supply line 19 Incombustibles extraction line 20 Sand extraction line 21 Combustion exhaust gas extraction line

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shizuo Yasuda 12 Nishiki-cho, Naka-ku, Yokohama City Mitsubishi Heavy Industries, Ltd.Yokohama Works (72) Yuji Kaihara 12, Nishiki-cho, Naka-ku, Yokohama Mitsubishi Heavy Industries, Ltd. Inside the factory

Claims (6)

[Claims] 1. A method for recovering oil from waste plastics containing vinyl chloride and other chlorine-containing plastics by thermal decomposition, wherein the waste plastics are extruded and flowed while the waste plastics are subjected to high temperature sand and / or heat before the thermal decomposition step. By mixing with the additive and heating to a temperature of 250-350 ° C,
What is claimed is: 1. A method for recovering oil from waste plastic, which comprises the step of producing a treated product consisting of a mixture of waste plastic and sand from which chlorine has been substantially removed. 2. A method for recovering oil from waste plastics by thermal decomposition, the waste plastics from which chlorine has been substantially removed by pretreatment or composition thereof are mixed with hot sand and / or additives and directly heated. And the temperature is about 350 ~
A method for recovering oil from waste plastics, which comprises thermally decomposing the waste plastics by heating and maintaining the temperature at 500 ° C, preferably about 400 to 480 ° C. 3. A method for recovering oil from waste plastics by thermal decomposition, wherein a fluidized bed using sand as a medium in which thermal decomposition products such as solid thermal decomposition residue after thermal decomposition is air-driven is used, or high-speed circulating fluidization. Combustion in the bed to produce high-temperature sand, and a part of the high-temperature sand is returned to the thermal decomposition step of the waste plastic or the chlorine removal step of the preceding step, and reused for recycling. Oil recovery method. 4. A method for recovering oil from waste plastics by pyrolysis, wherein the pyrolysis products obtained from the pyrolysis step of the waste plastics are liquid high boiling point oil and gaseous low boiling point oil by the first gas-liquid separation means. And the step of separating the low boiling point oil into the low molecular weight gas and refluxing the high boiling point oil to the thermal decomposition step and the step of separating the liquid low boiling point oil and the gaseous low molecular weight gas by the second gas-liquid separating means are connected in series. A method for recovering oil from waste plastic, which is characterized in that 5. A method for recovering oil from waste plastics by pyrolysis, wherein the waste plastics are mixed with high temperature sand to obtain a temperature of 250 to 35.
A first step for producing a treated product consisting of a mixture of waste plastic and sand from which chlorine has been substantially removed by heating to 0 ° C .; high temperature sand and / or an additive is added to the treated product of the first step. The temperature is about 350-500 ° C., preferably about 400-
A second step of producing a thermal decomposition product consisting of a gaseous high boiling point oil, a low boiling point oil and a low molecular gas and a solid thermal decomposition residue / sand mixture by heating to 480 ° C .; A reflux step of separating the decomposition product into a liquid high-boiling oil, a gas low-boiling oil and a low-molecular gas by the first gas-liquid separation means, and refluxing the high-boiling oil to the second step, a second gas-liquid separation Separation step of separating into liquid low boiling point oil and gaseous low molecular gas by means, solid pyrolysis residue / sand mixture of the second step, and sand that fluidizes the low molecular gas of the second gas-liquid separating means with air A method for recovering oil from waste plastics, which comprises a third step of producing high temperature sand by burning in a fluidized bed as a medium, and recycling at least a part of the sand in the first or second step. . 6. The waste plastic according to claim 5, wherein the additive used in the second step is a catalyst for promoting wax decomposition, which is synthetic zeolite or natural zeolite, preferably natural mordenite. Oil recovery method.