JPH08143872A - Pyrolizer for plastic - Google Patents

Abstract

PURPOSE: To provide a pyrolizer for a plastic excellent in energy recovery efficiency by taking out a melt in a pyrolytic reactor, causing the deterioration in heat transfer efficiency and cooking, and effectively utilizing the taken out melt. CONSTITUTION: This pyrolizer for a plastic is obtained by installing a pyrolytic reactor 3 for melting and pyrolyzing the plastic 36, a condenser 14 capable of condensing a pyrolytic gas generated in the pyrolytic reactor 3, a suction pipe and a suction tank 20 for partially taking out a melt 37 in the pyrolytic reactor 3, a storage tank 21 for the taken out melt and a melt combustion furnace 23 for burning the melt in the storage tank 21. The pyrolytic reactor 3 is heated with a combustion gas generated in the melt combustion furnace 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for, for example, melting and thermally decomposing waste plastic, cooling and condensing the generated pyrolysis gas, and recovering it as pyrolysis oil.

[0002]

2. Description of the Related Art Waste plastics discharged as industrial waste and general waste amount to 5.5 million tons per year, most of which is landfilled with other waste such as crockery and rubber. It was generally incinerated.
However, there is a problem in securing land for landfilling.For the method of incinerating waste plastic directly, the amount of heat generated by combustion of plastic is high, the furnace is easily damaged, the melting point of plastic is low, and it easily sticks to the hearth There are various problems such as black smoke, clinker, and dioxins.

Therefore, in order to solve the above problems, the present inventor previously provided a pyrolysis reactor for melting and thermally decomposing a raw material plastic, and an oil from waste plastic which is a mixture of various plastics. We proposed a thermal decomposition device for plastics that reuses the remaining so-called high-grade plastics (polyethylene, polypropylene, polystyrene, etc.) after recycling them, except for polyvinyl chloride, which is not suitable for recycling.

As shown in FIG. 3, this plastic thermal decomposition apparatus is arranged in a heating furnace (61) heated by a burner (63) and has a plastic supply pipe (64) and an agitator (6).
Pyrolysis reactor (62) equipped with 5), a reforming tower (66) for decomposing the pyrolysis gas generated in the pyrolysis reactor (62) into light components,
A KO pot (67) for separating heavy oil from the cracked gas passed through the reforming tower (66), a condenser (68) for cooling the cracked gas from which the heavy oil has been removed, and a condenser (68) A fuel tank (6) that stores a portion of the light oil obtained in
9), a recovered oil discharge pipe (70) for sending the remaining light oil to the recovered oil tank, and a washing tower (71) for washing uncondensed off gas with water,
An off-gas tank (72), an off-gas incinerator (73), and a melt extracting means (74) for extracting the melt in the thermal decomposition reactor (62) regularly or at any time are provided.

[0005]

By the way, in the thermal decomposition of plastics, most of the plastics used as raw materials are usually discharged as industrial wastes from plastic producers or as separated wastes. Some of these raw material plastics contain a large amount of inorganic matter. For example, for automobile bumpers, Si, M
Approximately 10% of minerals containing g and Ca and Fe are contained, and the plastic bowl contains approximately 40% of minerals containing Ca as the main component. When plastics containing these minerals are used as a raw material, the minerals gradually accumulate in the thermal decomposition reactor. When the slurry concentration of the molten liquid in the thermal decomposition reactor exceeds 40%, the heat transfer efficiency in the thermal decomposition reactor is extremely reduced, and further, coking occurs at the bottom of the thermal decomposition reactor. . Therefore, it is necessary to withdraw the molten liquid regularly or at any time, and the withdrawn molten liquid has been separately incinerated.

Further, in the plastic thermal decomposition apparatus shown in FIG. 3, recovered oil or kerosene is used as the fuel for the burner, which is a very inefficient process considering the energy recovery efficiency.

In view of the above points, an object of the present invention is to extract a molten liquid in a thermal decomposition reactor which causes reduction of heat transfer efficiency and occurrence of coking, and to effectively utilize the extracted molten liquid. , To provide a thermal decomposition device for plastics having excellent energy recovery efficiency.

[0008]

A thermal decomposition apparatus for plastics according to the present invention comprises a thermal decomposition reactor for melting and thermal decomposition of plastic, a condenser for condensing thermal decomposition gas generated in the thermal decomposition reactor, Molten liquid extracting means for extracting a part of the molten liquid in the thermal decomposition reactor, a storage tank for the extracted molten liquid, and burning the molten liquid in the storage tank to use combustion gas as a heating source for the thermal decomposition reactor. And a melt-burning furnace for supply.

The melt combustion furnace has a nozzle for spraying the melt,
It is preferable to include a combustion bed provided below the nozzle, an air header for supplying air to the combustion floor surface, and a burner for heating in the combustion furnace.

The melt extracting means may include a suction pipe arranged in the hollow vertical rotation shaft of the melt agitator, and a suction tank connected to the suction pipe.

The melt extracting means may be provided with a residue settling pipe arranged at the bottom of the pyrolysis reactor and a melt extracting pump connected to the residue settling tube.

It is preferable to provide an off-gas supply pipe for supplying the uncondensed gas of the condenser as fuel for the burner for heating in the combustion furnace.

[0013]

According to the plastic thermal decomposition apparatus of the present invention, the molten liquid that causes the decrease in heat transfer efficiency and the occurrence of coking is extracted, so that continuous operation for a long time becomes possible. Further, since the molten liquid in the thermal decomposition reactor is used as the heating source of the thermal decomposition reactor, no external fuel is required and the energy efficiency is high.

The melt is a residue after the waste plastic is decomposed in the thermal decomposition reactor and the gasoline, kerosene, and light oil phase equal parts are extracted, and the calorific value is the calorific value of the waste plastic before treatment of about 10,000 kcal / It is about half that of kg, and is a relatively stable liquid substance having a slurry viscosity of 100 to 250 cp. Therefore, it is possible to incinerate by a known combustion method such as a liquid spray combustion method.

The melt burning furnace has a nozzle for spraying the melt,
With a combustion bed provided below the nozzle, an air header for supplying air to the combustion floor surface, and a burner for heating in the combustion furnace, the ash formed by burning the inorganic substance in the melt However, since it can be captured and recovered on the surface of the combustion bed, there is no fear that the inorganic substance adheres to the pyrolysis reactor, the inside of the heating furnace and the flue to lower the heat transfer efficiency.

The energy efficiency is further increased in the case where the off-gas supply pipe for supplying the uncondensed gas component of the condenser as the fuel for the burner for heating in the combustion furnace is provided.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a plastic thermal decomposition apparatus according to the present invention.

In FIG. 1, a thermal decomposition apparatus for plastics comprises a thermal decomposition reactor (3) for melting and thermally decomposing waste plastic (36) and a molten liquid extracted from the thermal decomposition reactor (3). And a melt combustion furnace (23) which is used as a heat source for the thermal decomposition reactor (3).

The pyrolysis reactor (3) is arranged in the heating furnace (1), and the heating furnace (1) has a flue (24) for combustion gas in the melt combustion furnace (23). An off gas burner (2) is provided that is connected and used for heating at the start. The bottom surface of the pyrolysis reactor (3) has a concave spherical shape that is recessed downward at the center. The pyrolysis reactor (3) is provided with a raw material hopper (8) for supplying the raw plastic waste (36) and a pyrolysis gas discharge pipe (4). Discharge pipe (4)
Are connected to the reforming tower (11). The reforming tower (11) has a catalyst layer for further decomposing the pyrolysis gas into low carbon chain hydrocarbons.
(10) is provided. The combustion exhaust gas used for heating the pyrolysis reactor (3) is discarded from the chimney (12) of the reforming tower (11). The reforming tower (11) is connected to the condenser (14) via the KO pot (13). Condenser via KO pot (13)
The cracked gas introduced into (14) is cooled and condensed, and the condensed component, that is, high-quality recovered oil is sent to the recovered oil tank (16) by the recovered oil transfer pump (15) and stored there. It
On the other hand, uncondensed gas that has not been condensed in the condenser (14) is sent to the off-gas tank (17) and further burner (1
It is sent to an off-gas incinerator (19) equipped with 8) where it is incinerated.

The stirrer (5) is provided with a hollow vertical rotary shaft (6) penetrating the lid of the thermal decomposition reactor (3). Is connected to the drive motor via.

A suction pipe (7) is arranged in the vertical rotation shaft (6). The upper end of the suction pipe (7) extends above the upper end of the vertical rotary shaft (6), and the lower end of the suction pipe (7) extends vertically.
It is almost at the same height as the bottom edge of (6). The suction tube (7)
It is connected to the suction tank (20) via a conduit (32). The inside of the suction tank (20) is sucked by a pump (not shown). And suction pipe (7), conduit (32) and suction tank
The melt discharge means (31) is constituted by (20), whereby the melt (37) at the center of the bottom surface of the thermal decomposition reactor (3) is discharged.

The suction tank (20) is connected to the melt storage tank (21). The melt storage tank (21) is forcibly kept warm by an electric heater or the like so that the temperature does not drop. The melt in the melt storage tank (21) is sent to the melt combustion furnace (23) by the pump (22). A filter (30) is provided in the middle of the conduit from the melt storage tank (21) to the melt combustion furnace (23), and foreign substances such as metal and glass accumulated in the melt (37) Will be removed.

The melt burning furnace (23) is a nozzle for spraying the melt.
(25) and a combustion bed (26) provided below the nozzle (25),
An air header (27) for supplying air to the surface of the combustion bed (26), a combustion ash discharging device (28) provided below the combustion bed (26), and a burner (29) for heating in the combustion furnace. There is.

In such a structure, waste plastic
(36) is supplied from the hopper (8) to the thermal decomposition reactor (3) by alternately operating the pair of ball valves (9). The plastic (36) is heated and melted by the combustion heat of the melt combustion furnace (23) to become a melt (37). here,
In order to accelerate the reaction, the melt (3
Stir 7) with a stirrer (5). For example, in polypropylene plastics, the melt (37) heated to 390 to 400 ° C. is uniformly mixed with a stirrer and decomposed and evaporated. The pyrolysis gas generated at this time is mainly composed of a hydrocarbon gas having 1 to 40 carbon atoms and is sent to the reforming tower (11) through the discharge pipe (4) where the catalyst layer (10 ) Further decomposes into low carbon chain hydrocarbons, and the cracked gas feed pipe
It is sent to the KO pot (13) by (34). KO pot (13)
Then, the heavy oil is separated, and the heavy oil is returned to the pyrolysis reactor (3) through the heavy oil return pipe (35). The cracked gas from which heavy oil has been removed is sent to the condenser (14) where it is cooled and condensed, and is recovered as light oil. The recovered oil is sent to the recovered oil tank (16) by the recovered oil transfer pump (15).
The uncondensed gas that could not be condensed in the condenser (14) is
Propylene-based combustible off-gas having an average molecular weight of 32 is stored in the off-gas tank (17). The off gas tank (17)
An off-gas supply pipe (33) is provided for supplying uncondensed gas as fuel for the burner (29) for heating in the combustion furnace,
The off gas is being circulated and used. The off-gas supply pipe (33) is also connected to the reheating burner (2) attached to the heating furnace (1) of the pyrolysis reactor (3). Excessive offgas that cannot be completely burned by the burner (29) for heating in the combustion furnace and the additional burner (2) of the heating furnace (1) is incinerated by the burner (18) attached to the offgas incinerator (19).

On the other hand, the waste plastic (36) usually contains 2 to
Since it contains 4% of inorganic additive, this inorganic substance is gradually accumulated in the melt (37) in the thermal decomposition reactor (3). As a result, the heat transfer efficiency decreases due to the increase in the viscosity of the melt (37) and the oil decomposition rate decreases due to this, and if this progresses further, coking occurs at the bottom of the thermal decomposition reactor (3) and oil conversion occurs. The problem arises that the efficiency drops extremely. In order to prevent this, a certain proportion of the melt (37) must be withdrawn, and in this device, suction is placed inside the hollow vertical rotary shaft (6) of the melt agitator (5). Pipe (7) and suction tank (20) connected to the suction pipe (7)
The molten liquid (37) in the thermal decomposition reactor (3) is extracted by. The extracted molten liquid is once stored in the storage tank (21) and is effectively used as fuel in the molten liquid combustion furnace (23).

Since the melt combustion furnace (23) is forcibly heated by the burner (29) which uses uncondensed gas as a fuel, it is in a high temperature atmosphere, and the melt is injected from the melt nozzle (25) into the combustion bed.
The molten liquid can be smoothly incinerated by uniformly spraying it onto the (26) and by supplying air evenly from the combustion bed (26) surface from the air header (27). At this time, the inorganic matter becomes ash and is harmlessly discharged from the discharge device (28) to the outside of the furnace (23). On the other hand, the combustion gas generated by the combustion of the molten liquid is sent to the heating furnace (1) of the thermal decomposition reactor (3) by the flue (24) and is used for melting and thermal decomposition of the plastic (36). It becomes a heating source. The heating furnace (1) of the pyrolysis reactor (3) is the same as that of the melt combustion furnace (23).
It becomes the next combustion chamber where carbon, CO, etc. are recombusted, and the combustion efficiency becomes extremely high.

As described above, the plastic thermal decomposition apparatus according to the present invention uses the self-fuel of the molten liquid and the uncondensed gas, and has a high energy recovery rate.

Table 1 shows the material balance and the heat balance when the waste plastic heat of the polypropylene type is recovered and the heat of the melt combustion is recovered.

[0030]

[Table 1] As can be seen from Table 1, the processing amount of waste plastic is 1 ton / h, the recovered oil is 65% of the input amount of waste plastic, and the exhaust off-gas is 4% of the input amount. There is. The ash discharged is 7.5% of the input (7
5 kg / h) and was a white, free-flowing ash. In Table 1, the combustion Ig-loss residue means that the sample is put in a magnetic crucible and heated and burned in an oxidizing atmosphere in an electric furnace at 600 to 800 ° C. Most of the ash content is inorganic ash), and the ash content in the input plastic is the combustion Ig-l in an 800 ° C electric furnace.
The oss residual analysis value is 7.5%, and when converted to the plastic amount by subtracting this ash amount, it is found that the pure plastic input amount is 925 kg and the oil recovery amount is 70% of the input amount. The required amount of heat is 175 kg / h
And the amount of heat generated by the off gas that is effectively used is 60 kg / h. The heat balance is estimated to be only 4% of the amount of waste plastic input, and all the other off gas and the molten melt extracted are consumed for self-heating. It can be said that this is a process with high energy recovery efficiency.

The melt is a residue after the waste plastic is decomposed in the pyrolysis reactor and gasoline, kerosene, and the corresponding amount are extracted, and the calorific value is a slurry concentration of 30 to 40%. Melt of 5000-6000 kca
Low as 1 / kg, heat value of waste plastic before treatment is about 10
It is about half that of 000 kcal / kg.
And this melt has a slurry viscosity of 100 to 250 c.
p is a relatively stable liquid substance. From this, the spray combustion by the normal liquid spray combustion method is possible, and since the calorific value is low, the melt combustion furnace is not damaged, and the black smoke generation due to the lack of local oxygen in the combustion process is relatively small.

Therefore, as compared with the conventional method of directly burning waste plastic, generation of black smoke is suppressed, spray droplet combustion is possible, there is no generation of local high temperature part in the furnace, and damage to the furnace or sintering It has features such as no generation of rings and clinker.

Further, the melt in the thermal decomposition reactor contains undecomposed waste plastic, generated coke (carbon) and inorganic substances, and it is difficult to detoxify and discard as it is, but the melt combustion furnace The ash generated inside is talc (S
i, Mg), lime (Ca), Fe and the like can be used for detoxification and dumping.

The melt combustion furnace (23) shown in FIG.
With the so-called melt-spray bed combustion method, the ash formed by burning the inorganic substances in the melt can be captured and recovered on the surface of the combustion bed (26), and the inorganic substances are pyrolyzed in the reactor (3). , There is no concern that it will adhere to the inside of the heating furnace (1) and the flue (24) and reduce the heat transfer efficiency. However, as a matter of course, a known spray combustion type melt liquid combustion furnace may be used instead of the melt liquid spread bed combustion type melt liquid combustion furnace.

FIG. 2 shows another embodiment of the melt discharge means (41) for discharging the melt in the thermal decomposition reactor (3). The melt withdrawing means (41) of this embodiment is arranged in the center of the bottom surface of the pyrolysis reactor (3) and a residue settling pipe (42) extending downward through the bottom wall of the heating furnace (1). And a melt discharge pump (43) connected to the residue settling pipe (42). heating furnace
The bottom wall of (1) is provided with a cylindrical projecting portion (44) surrounding the residue settling tube (42) to ensure uniform heating of the residue settling tube (42). The melt extracted through the residue settling pipe (42) is sent to the melt storage tank (21) for use as fuel in the melt combustion furnace (23), but part of it is pyrolyzed. Returned to the reactor (3).

[0036]

According to the plastic thermal decomposition apparatus of the present invention, the molten liquid that causes the decrease in heat transfer efficiency and the occurrence of coking is extracted, so that continuous operation for a long time becomes possible. Further, since the molten liquid in the thermal decomposition reactor is used as the heating source of the thermal decomposition reactor, no external fuel is required and the energy efficiency is high.

The ash generated in the melt burning furnace is talc (Si, Mg), lime (Ca), Fe, etc., and can be detoxified and discarded.

Further, since the molten liquid can be burned by a known burning method such as a liquid spray burning method, compared with the method of directly burning the waste plastic, there is no damage to the molten liquid combustion furnace and the burning process The generation of black smoke due to local oxygen deficiency is relatively small.

The melt burning furnace has a nozzle for spraying the melt,
With a combustion bed provided below the nozzle, an air header for supplying air to the combustion floor surface, and a burner for heating in the combustion furnace, the ash formed by burning the inorganic substance in the melt However, since it can be captured and recovered on the surface of the combustion bed, there is no fear that the inorganic substance adheres to the pyrolysis reactor, the inside of the heating furnace and the flue to lower the heat transfer efficiency.

The energy efficiency is further increased in the case where the off-gas supply pipe for supplying the uncondensed gas content of the condenser as the fuel for the burner for heating in the combustion furnace is provided.

[Brief description of drawings]

FIG. 1 is a flow chart showing a thermal decomposition apparatus according to an embodiment of the present invention, in which a main portion is shown in a vertical sectional view.

FIG. 2 is a vertical sectional view showing a modified example of the thermal decomposition apparatus according to the embodiment of the present invention.

FIG. 3 is a flowchart showing a conventional thermal decomposition apparatus.

[Explanation of symbols]

 (3) Pyrolysis reactor (5) Stirrer (7) Suction pipe (14) Condenser (20) Suction tank (21) Combustion melt storage tank (23) Melt combustion furnace (25) Dispersion of melt Nozzle (26) Combustion bed (27) Air header (29) Burner for heating in combustion furnace (31) Melt liquid extraction means (33) Off-gas supply pipe (41) Melt liquid extraction device (42) Residue settling pipe (43) Melt extraction pump

Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location C10J 3/00 ZAB A (72) Inventor Kenichi Nagai 5-3-28 Nishikujo, Konohana-ku, Osaka, Hitachi Shipbuilding Co. In the company

Claims (5)

[Claims] 1. A thermal decomposition reactor (3) for melting and thermally decomposing a plastic (36), a condenser (14) for condensing the thermal decomposition gas generated in the thermal decomposition reactor (3), and thermal decomposition. Melt liquid extraction means (31) (41) for extracting a part of the melt liquid (37) in the reactor (3), and a storage tank (21) for the extracted melt liquid
And a melt combustion furnace (2) that burns the melt in the storage tank (21) and supplies the combustion gas as a heating source for the pyrolysis reactor (3).
3) Plastic pyrolysis device with and. 2. A melt combustion furnace (23) comprising a melt spray nozzle (25) and a combustion bed (26) provided below the nozzle (25).
And an air header (27) that supplies air to the combustion bed (26) surface,
The thermal decomposition apparatus for plastics according to claim 1, further comprising a burner (29) for heating the inside of the combustion furnace. 3. The melt extracting means (31) is a melt agitator.
Suction tube (7) located inside the hollow vertical shaft (6) of (5)
And a suction tank (20) connected to the suction pipe (7). 4. A melt decomposition means (41) is a thermal decomposition reactor.
The residue settling pipe (42) arranged at the bottom of (3), and a melt discharge pump (43) connected to the residue settling pipe (42). Plastic pyrolyzer. 5. An off-gas supply pipe (3) for supplying the uncondensed gas component of the condenser (14) as fuel for the burner (29) for heating in the combustion furnace.
3. The plastic thermal decomposition apparatus according to claim 2, further comprising 3).