JP3327786B2 - Oil recovery method from waste plastic - Google Patents

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. More particularly, the present invention relates to a method for recovering oil from waste plastics, in which waste plastics containing vinyl chloride and other chlorine-containing plastics are dechlorinated and then thermally decomposed.

[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.

In this method, it is necessary to completely remove the thermosetting resin and solid foreign matter in a pretreatment step in order to avoid troubles in the pump circulation line.
The cost was large and the economy was problematic. Furthermore, the oil obtained by decomposition only with heat is unstable, causing not only the trouble of coking on the inner wall surface of the heating furnace pipe, but also the solidification of these liquid oils at room temperature, so that the pump circulation line Requires the heat insulation of a steam jacket, etc., and requires replacement of the process line with heavy fuel oil A during startup and shutdown, leading to an increase in operation and maintenance costs.

[0004] In order to solve such a problem, the present applicant has
Japanese Patent Application No. 7-194226 proposes a method in which a thermosetting resin or a solid foreign matter does not cause a trouble even if mixed therein. (Unknown, hereinafter referred to as prior art) This application was developed as a comprehensive system for recovering oil by pyrolysis of waste plastic, and the feature of the application is to mix waste plastic with hot sand. A first step (a dechlorination step) of producing a treated product comprising a mixture of waste plastic and sand from which chlorine has been substantially removed by heating to a temperature of 250 to 350 ° C. By adding high-temperature sand and / or additives and heating to a temperature of about 350 to 500 ° C., preferably about 400 to 480 ° C., it comprises gaseous high-boiling oil, low-boiling oil and low-molecular gas. A second step (pyrolysis step) of producing a pyrolysis product and a solid pyrolysis residue / sand mixture, and converting the pyrolysis product of the second step into a liquid high-boiling oil, a gas low-boiling oil, and a low-molecular compound Gas into high-boiling oil A first gas-liquid separation step of refluxing into two steps, a second gas-liquid separation step of separating into a liquid low-boiling oil and a gaseous low molecular gas, and a solid pyrolysis residue / sand mixture in the second step; (2) A third method in which the low molecular gas in the gas-liquid separation step is burned in a fluidized bed using sand flowing through air as a medium to produce high-temperature sand, and a part of the sand is recycled to the first or second step. Oil recovery method consisting of a process (residue incineration process).

[0005] In the above prior art, the present applicant has
As a suitable technique for the dechlorination step, Japanese Patent Application No. 8-65371 (prior application, unknown) proposes a dechlorination step using a rotary kiln, specifically a structure in which waste plastic is extruded and flowed.

[0006]

However, in the case where the dechlorination step is constituted by a mechanical stirring means such as a rotary kiln, the filling rate of the processed material is as low as 10 to 20%, and as a result, the capacity must be increased. is there.

The present invention has been made in view of the above problems, and has as its object to provide an oil recovery method capable of reducing the installation space of a dechlorination step and a pyrolysis step and efficiently transporting the oil. The waste plastic referred to in the present invention is garbage containing a large amount of plastic separated from municipal garbage, which contains thermoplastic resin (polyethylene, polypropylene, polystyrene, etc.) as a main component, and partially contains polyvinyl chloride, PET, heat, etc. Contaminants such as curable resin, paper, and garbage may be mixed. Also,
Among industrial wastes, those containing a large amount of plastic such as residual plastic of plastic die-cast products are also included.

According to a first aspect of the present invention, there is provided a method for recovering oil by pyrolysis of waste plastics including vinyl chloride and other chlorine-containing plastics .
Mixed with sand, by heating to a temperature 250 to 350 ° C., a dechlorination step of producing a processed product comprising a mixture of waste plastics and sand substantially chlorine has been removed, the treated product, hot sand And mixed directly with the sand by thermal contact
A heating decomposition step for heating and decomposing the waste plastic by heating and raising the temperature to about 350 to 500 ° C. , wherein the dechlorination step and the heat decomposition step are constituted by mechanical stirring means; The dechlorination step and the thermal decomposition step are arranged with a difference in gravity, and the transfer of the processed material from the dechlorination step to the thermal decomposition step is performed using gravity. In addition, along with high-temperature sand in the dechlorination step,
Synthetic zeolite, natural zeolite or natural mordenite
Decomposes wax produced by thermal decomposition of waste plastics
An additive consisting of a promoting catalyst may be added.

According to this invention, the fact that the dechlorination step and the thermal decomposition step can be arranged with a difference in gravity is provided by stacking the dechlorination step and the thermal decomposition step vertically.
In addition, when the two processes are constituted by mechanical stirring means having a horizontal structure such as a horizontal kiln, the installation area can be reduced to almost half even when the two processes are provided, resulting in a large saving. It leads to space.

Further, according to the present invention, the thermal decomposition step or the dechlorination step may be performed by appropriately arranging the waste plastic and fluidized sand at an appropriate position on the bottom of the stirring space where the sand is mechanically conveyed. Is disposed, and is constituted by a mechanical stirring means for flowing the waste plastic and the fluidized sand by an air current spouted from the diffuser, thereby facilitating dechlorination and thermal decomposition, and blocking the fluidized medium and the like. Etc. can also be prevented. In this case, in addition to the screw conveyor, a horizontal stirring tank having a double helical ribbon structure can be used as the mechanical stirring means. The invention according to claim 3
Can be used in a horizontal kiln or the like to perform the dechlorination step and the thermal decomposition step.
It is composed of mechanical stirring means having a mold structure, and the two
It is characterized by the fact that the process is arranged vertically stacked,
Further space saving can be achieved. Claims 4 and 5
As in the invention described, the hot sand is heated to 400 to 750 ° C.
High-temperature heated circulating sand and spouted from the diffuser
It is preferable that the exhaust gas be the combustion exhaust gas EGR. Further
Further, as in the invention according to claim 6, the dechlorination step
Is composed of a mechanical stirring tank with a horizontal structure such as a horizontal kiln.
In both cases, an aeration tube extending in the longitudinal direction of the stirring tank is arranged,
The exhaust gas EGR is introduced into the air diffuser, and the bottom of the stirring tank is introduced.
By diffusing the combustion exhaust gas in the tank,
The oil can be recovered by mixing and stirring.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. It's just FIG. 1 is a detailed view showing a dechlorination step and a thermal decomposition step according to an embodiment of the present invention, and FIG. 2 shows an oil recovery system for waste plastic incorporating the dechlorination step. In FIG. 1, a twin-screw horizontal stirring and conveying device is vertically arranged, an upper conveying device is configured as a dechlorination furnace 1, and a lower conveying device is configured as a pyrolysis furnace 2, and both are connected by a vertical duct 1C. It is composed. That is, in the twin-screw horizontal stirring and conveying device, a pair of screw shafts 40a in which the helical screw blades 40 are arranged are arranged in parallel in a horizontally long flowing medium stirring tank 42 having a bottom side formed in a semicylindrical shape. I do. In the stirring tank 42 on the side of the dechlorination furnace 1, a diffuser 41 extending in the longitudinal direction is disposed at a central bottom portion sandwiched between a pair of screw shafts 40 a, and the flue gas is connected to the diffuser 41 via the line 21. The EGR is introduced to allow the combustion exhaust gas to be diffused into the stirring tank from the bottom of the stirring tank 42, and a waste plastic supply port 6 is provided at an upper portion on the position side of the stirring tank 42. But its supply port 6
On the upstream side adjacent to the branch line 7 from the residue combustion furnace 3
From the outlet end of the line 7 to 600-9
It is configured so that high-temperature fluidized sand of about 50 ° C. can be charged.

At the outlet end of the stirring tank 42 connected to the vertical duct 1C, a vertical partition plate 44 having a concave overflow portion 44a formed on the center upper surface is erected, and a combustion chamber is provided on the outlet side of the pipe 8 at the outlet side. An HCl absorption tower 81 is connected via a tower 80 and a pipe 82. (See FIG. 2) A non-combustible transfer passage is provided on the bottom surface of the partition plate 44 on the inlet side, and is open to the vertical duct 1C via a pusher 93. A diffuser tube 41 is disposed above the pusher 93 to prevent clogging by incombustibles.

The vertical duct 1C is connected to the overflow section 44.
a, the waste waste plastic is continuously connected to the inlet side of the pyrolysis furnace 2 by gravity so as to be able to be charged by gravity, and the open end 1C1 of the vertical duct 1C on the side of the pyrolysis furnace 2 is used to prevent backflow and to provide a gas seal. It is good to make it open in the sand storage part.

According to the dechlorination furnace 1, 1
Waste plastic P pulverized to about 200 to 200 mm and 400 to 750 ° C. from line 7, preferably 500 to
When the circulating sand S heated to a high temperature of 600 ° C. is supplied to the inlet side, the waste plastic and the high-temperature circulating sand S are mixed with the combustion exhaust gas or the like supplied from the air diffuser 41 while being bubbled and stirred in the stirring tank 42. The mixture is conveyed toward the outlet side while being stirred by the pair of spiral screw blades 40 in the stirring tank 42, and the waste plastic is dechlorinated in the space in the stirring tank 42 maintained at a temperature of 250 ° C. to 350 ° C. As shown in FIG. 1, the dechlorinated waste plastic is charged into the pyrolysis furnace 2 by gravity through the vertical duct 1C from the overflow section 44a together with the fluidized sand.

As shown in FIG. 2, chlorine in the waste plastic P is separated by about 95% or more by the stirring, and the
Through the combustion tower 80 provided at the upper part of the dechlorination furnace 1 outlet side
A Cl-rich gas is withdrawn, and a fuel and air or oxygen-enriched air are supplied in the combustion tower 80 to remove terephthalic acid (derived from PET), PVC plastic (derived from polyvinyl chloride), etc. contained in the HCl-rich gas. Performs complete combustion of combustible substances such as sublimable substances and HC gas. Thereafter, the HCl-rich gas is guided to the HCl absorption tower 81, and the HCl is recovered with water or an alkali absorbing solution. As a result, even when the HCl-rich gas guided to the HCl absorption tower 81 is cooled, various coking troubles in the pipe 82 and the HCl absorption tower 81 may occur without solid deposition of the sublimable substance, HC gas, and the like. Absent.

On the other hand, in the stirring tank 42 on the side of the pyrolysis furnace 2 into which the waste plastic and the fluidized sand are introduced, a stirring tank 42 in which a pair of screw shafts 40a extend below the dechlorination furnace 1 is moved in the longitudinal direction. And the outlet end of the branch line 11 to which the circulating sand S of the residue incinerator 3 is returned is connected, and the outlet end of the line 11 is connected at 600 to 950 ° C.
The hot and circulating sand before and after can be charged. At the outlet end of the stirring tank 42 on the side of the pyrolysis furnace 2, a vertical partition plate 44 having a concave overflow portion 44 a recessed on the central upper surface as described above is erected, and the partition plate 44 is formed.
On the bottom surface on the inlet side, there is provided a noncombustible discharge line 28 which opens toward the inclined outlet line 9 via a pusher 93.
After the large incombustibles are removed by the filter 85 disposed in the middle of the path, the remaining processed material is returned to the pyrolysis furnace 2 via the return line 84 composed of a bucket conveyor or the like. An air diffuser 45 is disposed above the pusher 93 to prevent clogging by incombustibles.

According to the pyrolysis furnace 2, the vertical duct 1
The dechlorinated plastic mixture supplied from C is mixed with the additive T supplied from the additive supply line 10 and the circulating sand S at a high temperature of 600 to 950 ° C. supplied from the circulating sand supply line 11 to a temperature of 350 ° C. While maintaining the temperature at ５００500 ° C., preferably 400-480 ° C., the mixture is conveyed toward the outlet side while being stirred by a pair of spiral screw blades 40 to perform thermal decomposition. The additive T is a catalyst for further accelerating the decomposition of wax generated by the thermal decomposition of waste plastic, and is conventionally used in the petrochemical field, and is a synthetic zeolite or a natural zeolite, and is preferably a natural mordenite. With such an additive, coking due to a polycondensation reaction that occurs simultaneously with thermal decomposition can be suppressed at the same time, but the additive is not necessarily required.

Next, as shown in FIG. 2, a first gas-liquid separation step 4 is attached to the outlet 2a of the pyrolysis furnace 2 where the pyrolysis products evaporate. On the gas outlet side of the process, a second gas-liquid separation process 5 is connected in series via an uncondensed gas extraction line 13. As a result, of the gaseous pyrolysis products generated in the pyrolysis furnace 2, low molecular gas, gaseous low-boiling oil (for example, having a boiling point of 250 ° C. or less), and high-boiling oil (for example, having a boiling point of 250 ° C. or more) exit. The condensate such as high-boiling oil is taken out of the section 2a and cooled to about 250 ° C. in the first gas-liquid separation step 4 to be circulated back to the pyrolysis furnace 2 from the outlet 2a.

A low molecular gas and a low boiling point oil are obtained from the line 13, cooled in the second gas-liquid separation step 5 and the cooler 22, and discharged from the low boiling point distillate condensate extraction line 15 through the low boiling point oil O. And the uncondensed low molecular gas is sent out to the residue incinerator 3 through the low molecular gas extraction line 16. On the other hand, the solid pyrolysis residue (carbonaceous material), solid foreign matter, and non-liquefied thermosetting resin generated in the pyrolysis furnace 2 are taken out from the pyrolysis residue mixture extraction line 17 by gravity or a screw feeder, and the like. It is introduced into the residue incinerator 3.

The first gas-liquid separation step 4 is constituted by disposing a liquid disperser 62 such as a spray nozzle on the upper side of a distillation tower 41 such as a packed tower or a column tower as a gas-liquid contact means. As a liquid to be supplied to the liquid disperser 62, a part of the low-boiling oil separated in the second gas-liquid separation step 5 and cooled by the cooler 22 passes through the liquid disperser 62 from the line 15 ′ to the first gas-liquid Reflux to separation step 4 to substantially eliminate high boiling oil in line 13.

Although the second gas-liquid separation step 5 can be constituted by a condenser, the reboiler 53, the lower gas-liquid contact portion (low molecular gas diffusion portion) 51A, and the upper gas-liquid contact portion are arranged in this order from the bottom of the vertical tower. (Low boiling point oil recovery unit) 51B and cooling unit 5
2 and an uncondensed gas extraction line 13 is preferably connected between the upper gas-liquid contact portion 51B and the lower gas-liquid contact portion 51A. The low-boiling oil extracted from the bottom of the second gas-liquid separation step 5 through the line 15 is cooled by the cooler 22 and then reused, but part of the oil is recycled through the branch line 15 '. The liquid is supplied to the liquid disperser 62 in the first gas-liquid separation step 4.

The residue incinerator 3 is composed of a high-speed circulating fluidized bed or a bubbled fluidized bed. Air is introduced from the combustion air supply line 18 to form a fluidized bed using sand as a medium. The temperature is 500 to 950 ° C., preferably. Is maintained at 750 to 950 ° C., the organic matter in the line 17 is completely burned, and the exhaust gas is further reduced to 850 to 9 by the introduction of secondary air from the line 18.
While the temperature is raised to 50 ° C. to suppress the generation of dioxins and the like, the flue gas G is taken out from the flue gas take-out line 21, and the air diffusers 41, 4 of the dechlorination furnace 1 and the pyrolysis furnace 2 are taken out.
3, 45.

On the other hand, incombustibles F such as metal and glass which cannot be completely incinerated in the residue incinerator 3 are taken out from an incombustibles extraction line 19. The sand separated from the residue incinerator 3 by a cyclone or the like (not shown) is recycled from the lines 11 and 7 to a dechlorination furnace and a pyrolysis furnace. With this method, high-temperature sand can be easily circulated and used. When the calorie of the circulating sand S is insufficient, a part of the low molecular gas in the low molecular gas extraction line 16 or the oil O in the low boiling fraction condensate extraction line 15 may be used as fuel for the residue incinerator 3. it can.

[0024]

As described above, according to the present invention, the installation space for the dechlorination step and the pyrolysis step can be reduced, and the transfer can be carried out efficiently.

[Brief description of the drawings]

FIG. 1 is a schematic view of a dechlorination furnace and a pyrolysis furnace according to an embodiment of the present invention used in the oil recovery system of FIG.

FIG. 2 is an overall schematic diagram showing a system for recovering oil from waste plastic according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dechlorination furnace 1C Vertical duct 2 Pyrolysis furnace 3 Residue incinerator 4 1st gas-liquid separation process 5 2nd gas-liquid separation process 81 HCl absorption tower

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Shizuo Yasuda 12 Nishiki-cho, Naka-ku, Yokohama-shi Mitsubishi Heavy Industries, Ltd.Yokohama Works Ltd. (56) References JP-A-7-286062 (JP, A) JP-A-8-188778 (JP, A) JP-A-8-188780 (JP, A) JP-A-7-316339 (JP, A) Kaihei 7-62353 (JP, A) International Publication 96/40839 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C10G 1/10 B29B 17/00 C08J 11/12 C08J 11 / 16

Claims (6)

(57) [Claims] 1. A method for recovering oil by pyrolysis of waste plastics including vinyl chloride and other chlorine-containing plastics, wherein the waste plastics are mixed with high-temperature sand, and the temperature is 250 to 35.
A dechlorination step of producing a treated material comprising a mixture of waste plastic and sand from which chlorine has been substantially removed by heating to 0 ° C .; mixing the treated material with high-temperature sand; For thermal contact
A heating / decomposition step of heating / decomposing waste plastic by directly heating and raising / maintaining the temperature to about 350 to 500 ° C. , wherein the dechlorination step and the heat decomposition step are constituted by mechanical stirring means. The oil from waste plastics, wherein the dechlorination step and the thermal decomposition step are arranged with a gravity difference, and the transfer of the processed material from the dechlorination step to the thermal decomposition step is performed using gravity. Collection method. 2. The thermal decomposition step or the dechlorination step,
Waste plastic and fluidized sand is disposed airflow diffuser section at an appropriate position of the stirring space bottom conveyed mechanically agitated, by air flow ejected from the diverging air unit, the waste plastic and the flow <br/> dynamic 2. The method for recovering oil from waste plastic according to claim 1, wherein the method comprises mechanical stirring means for flowing sand. 3. The method according to claim 1, wherein the dechlorination step and the thermal decomposition step are performed in a horizontal key.
It consists of mechanical stirring means of horizontal structure such as run
Wherein the two steps are vertically stacked.
The method for recovering oil from waste plastic according to claim 1. 4. The hot sand is heated to 400 to 750 ° C.
2. The waste according to claim 1, wherein the circulating sand is heated.
How to recover oil from plastic. 5. A gas discharged from the air diffuser is a combustion exhaust gas.
3. The waste plastic according to claim 2, wherein the waste plastic is EGR.
How to recover oil from sticks. 6. A horizontal structure such as a horizontal kiln for the dechlorination step.
A mechanical stirring tank, and the length of the stirring tank
A diffuser pipe extending in the direction is disposed, and the flue gas E
Introduce GR and scatter combustion exhaust gas into the tank from the bottom of the stirring tank.
3. The waste plastic according to claim 2, wherein
How to recover oil from oil.