JP3806829B2 - Waste plastic pyrolysis apparatus and cleaning method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a waste plastic pyrolysis apparatus capable of removing residues accumulated by heating and decomposing waste plastic in the absence of oxygen with an elongated tube type pyrolysis apparatus, and a cleaning method therefor. Is.
[0002]
[Prior art]
In order to recover waste plastics such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and acrylic-butadiene-styrene copolymer (ABS) as resources, pyrolysis Many methods are employed that thermally decomposes into low molecules in the absence of oxygen in the apparatus, condenses the generated gas components, and recovers them as oil components.
Such pyrolysis devices include a tank type and a tube type. The tank type is equipped with a cylindrical tank body with a conical bottom and a heating unit placed around it. The upper part is a waste plastic input part, the generated gas component discharge part, and the bottom part is a residue discharge. Parts are provided. A scraper mechanism is provided that stirs the waste plastic to be pyrolyzed and discharges the residue generated and accumulated by pyrolysis or peels off the coking that adheres to the inclined surface of the bottom.
The tube type is equipped with a horizontally long and cylindrical tube body and a heating part arranged around it, and there are a screw type with a screw inside and a simple tube type without a screw. .
[0003]
The tank-type thermal decomposition apparatus which is currently mainstream has a problem that the tank is generally large, and the scraper mechanism for discharging residue and coking peeling is included inside, so that the cost is high. In addition, tube-type pyrolysis devices that employ a screw type are designed to discharge residues with an internal screw or to remove coking that adheres to the inner surface of the tube body. There is a problem that it becomes higher.
On the other hand, a simple tube-type pyrolysis device that does not have a screw inside has the advantage of simple structure and low cost, but it must be periodically cleaned to remove residue inside the tube body and remove coking. There is. In the conventional cleaning, remove the cover plate that closes both ends of the tube body, insert a cleaning tool such as a brush longer than one end, reciprocate to peel off the coking and the other end The method is generally used to discharge coke that has been peeled off from the residue.
[0004]
[Problems to be solved by the invention]
However, this method has the problem that it takes a lot of time and effort to remove the lids at both ends of the tube body and to operate the cleaning tool, and if the tube body is quite long, the inner wall surface of the tube body There is a problem that it is difficult to sufficiently peel off the caulking that is firmly fixed. Further, prior to cleaning, it is necessary to lower the temperature in the tube body to room temperature and raise the temperature to a predetermined value when the thermal decomposition reaction is resumed, which increases the time and energy consumption.
Accordingly, an object of the present invention is to provide a cleaning method capable of efficiently and sufficiently removing residues and coking (hereinafter referred to as “residues”) in a simple tube-type pyrolyzer without a screw.
[0005]
[Means for Solving the Problems]
The invention according to claim 1 is a tubular body having a pipe body (2) and the pipe body (2), having a gas supply part (6) at one end and a gas discharge part (7) at the other end. Waste plastic connected to one end of the pipe body (2) via a first on-off valve (10), a heating part (3), a combustion furnace (18) connected to the gas supply part (6) A supply device (9) is connected to one end of the pipe body (2) via a flow rate adjusting valve (22), and the flow rate of oxygen-containing pressurized gas supplied into the pipe body (2) is made variable. A pressurized gas supply device (23) to be obtained, a condensing device (12) connected to the other end of the tube body (2) via a second on-off valve (13), and the other of the tube body (2) A third on-off valve (25) having one end connected to the end, and a fourth on-off valve (29) having one end connected to the other end of the third on-off valve (25) A dust collector (30) connected to the other end of the fourth on-off valve (29), and a fifth on-off valve (28) having one end connected to the other end of the third on-off valve (25). And a gas treatment device (16) connected to the other end of the fifth on-off valve (28) .
[0006]
According to this waste plastic thermal decomposition apparatus, when residues adhere to the inner surface of the tube body 2, it is easily oxidized and decomposed, and the decomposed material is captured by the dust collecting device 30 and the internal Can be easily cleaned. That is, while the waste plastic pyrolysis apparatus is moving, the first on-off valve 10 is closed to prevent the molten waste plastic from being introduced into the pipe body 2, and then the flow rate adjustment valve 22 is adjusted to be open and adjusted. By supplying an appropriate amount of oxygen from the pressurized gas supply device 23, the residues in the tube body 2 can be efficiently oxidized. Next, the residual oxide generated by the oxidation treatment is sufficiently supplied with the pressurized gas from the pressurized gas supply device 23, so that the residual oxide is blown off, and the third on-off valve 25 and the fourth on-off valve. It can be captured by the dust collecting device 30 via 29.
Note that the gas component generated by the oxidation treatment can be rendered harmless by the gas treatment device 16 via the fifth on-off valve 28.
[0007]
Invention of Claim 2 introduces a heating gas into the cylindrical heating part (3) surrounding the pipe body (2) and heats the inside of the heating part (3), and the pipe body (2). A step of introducing molten waste plastic from one end of the tube, a step of thermally decomposing the molten waste plastic in the form of a gas in the pipe body (2), and introducing the pyrolysis gas into the condenser (12) for condensation Producing the oil component and the non-condensed gas component, introducing the gas component into the gas treatment device (16) and detoxifying it, and thereafter supplying the molten waste plastic to the pipe body (2). A process of stopping;
Next, a first step of introducing an oxygen-containing pressurized gas having a first in-pipe flow rate into the pipe body (2) to oxidize residues in the pipe body (2), and this oxidation treatment Introducing the generated gas component into the gas processing device (16) to render it harmless;
Subsequently, the step of increasing the flow rate in the pipe of the oxygen-containing pressurized gas introduced into the pipe body (2) to a second pipe flow rate larger than the pipe flow rate in the first step, and thereby the pipe body ( And 2) a step of forcibly discharging the residual oxide from the pipe body and introducing it into the dust collector (30) .
According to the cleaning method of the waste plastic pyrolysis apparatus of the present invention, organic substances constituting the residues react with oxygen by oxidation treatment of the residues, so that carbon dioxide (CO ₂ ) or water (H ₂ O ) is reacted. ), And the portion that cannot be decomposed is reduced in volume and left as an inorganic component such as ash, sand, or metal pieces. And since the organic substance fixed as caulking is decomposed and carbonaceous substance is substantially lost, the adhesive force to the inner wall of the pipe body is remarkably reduced, and it is easily peeled off and discharged by air blow. Furthermore, even when the tube body is considerably long, the coking can be easily peeled off and discharged. In addition, this method can quickly shift to a high temperature oxidation state after stopping the pyrolysis reaction without once reducing the temperature inside the tube body held at a high temperature during the pyrolysis operation to room temperature, so that the time required for cleaning is reduced. Is short and energy consumption may be small.
Moreover, in order to set the flow rate of the pressurized gas supplied to the tube body to the first flow rate for treating the residue and to discharge the residual oxide after the oxidation treatment, the flow rate is higher than the first flow rate. Since the process is performed at the second flow rate, the remaining oxide can be reliably guided to the dust collector 30 and captured.
Further, according to the cleaning method of the present invention, since the harmful components in exhaust gas generated during the oxidation process may be detoxification or removal treatment in the gas treatment device, never contaminate the environment.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic process flow diagram showing an example of a thermal decomposition apparatus for carrying out the cleaning method of the present invention. An elongated tube-type pyrolysis apparatus 1 includes a horizontally long tube main body 2 without a screw inside, and a heating unit 3 having a cylindrical heat insulating wall surrounding the periphery thereof. A waste plastic introduction part 4 is provided at the end on the left side, and a discharge part 5 for discharging gas components generated at the end on the downstream side (right side in the drawing). Further, a gas supply unit 6 for supplying a heating gas to the upstream (left side of the drawing) end of the heating unit 3 and a gas discharge unit 7 for discharging the heat-exchanged gas to the downstream (right side of the drawing) end are provided. .
[0009]
The introduction part 4 of the pipe body 2 is connected to a waste plastic supply device 9 by a pipe 8, and an open / close valve 10 is provided in the pipe 8. Further, the discharge portion 5 of the pipe body 2 is connected to a condenser device 12 by a pipe 11, and an open / close valve 13 is provided in the pipe 11. The condenser 12 is provided with a cooling pipe (not shown) for cooling the gas component, and the pipe 14 for discharging the oil component cooled and condensed by the condenser 12 is connected to an oil component recovery tank (not shown) and does not condense. The pipe 15 for discharging the gas component is connected to the gas processing device 16.
[0010]
The gas supply unit 6 of the heating unit 3 is connected by a pipe 17 to a gas discharge port of a combustion furnace 18 that generates a heated gas by burner combustion, and the heated gas exchanged through the heating unit 3 is shown from the gas discharge unit 7. Not exhausted to the exhaust gas treatment device.
A pipe 19 is branched from the pipe 8, and an opening / closing valve 20, a flow meter 21, and a flow rate adjustment valve 22 are provided in the pipe 19, and the tip thereof is connected to a pressurization type gas supply device 23 such as a blower. A pipe 24 is branched from the pipe 11, and an open / close valve 25 is provided in the pipe 24. The pipe 24 is further branched into a pipe 26 and a pipe 27, and an opening / closing valve 28 is provided in the pipe 26, and the tip thereof is connected to the gas processing device 16.
On the other hand, an opening / closing valve 29 is provided in the pipe 27 and its tip is connected to a bag filter type or cyclone type dust collector 30. The dust collector 30 is connected with a pipe 31 for discharging the exhaust gas from which inorganic components have been removed and a pipe 32 for discharging the removed inorganic components.
[0011]
The supply device 9 heats and melts waste plastic and supplies it to the thermal decomposition apparatus 1, and the same device as the heat transfer heater type melting device usually used for plastic injection molding is used. That is, it has a melt extrusion screw 35 that is rotationally driven by a rotating device 36 such as an electric motor in a cylindrical melting part 33, and has a hopper 38 that supplies finely pulverized waste plastic on the upstream side (left side in the drawing). A pipe 8 is connected to the discharge port at the side end.
As the gas processing device 16, for example, a combustion type or an adsorption type filled with activated carbon is used. The combustion type detoxifies harmful substances in the gas component by combustion, and the adsorption type adsorbs the harmful substances in the gas component. Is to be removed. In addition, the processed gas component discharged | emitted from the gas processing apparatus 16 is discharged | emitted from the piping 37 outside.
[0012]
Next, the operation of the above apparatus will be described. First, the inside of the pipe body 2 of the thermal decomposition apparatus 1 is replaced with an inert gas such as nitrogen gas by a purge pipe (not shown). Next, a heating gas of about 800 ° C. is introduced from the heating furnace 18 into the heating unit 3 to heat the inside of the tube body 2 and the supply device 9 is operated to melt the waste plastic. Next, the on-off valves 10 and 13 are opened, the on-off valves 20 and 25 are closed, and waste plastic melted at a temperature of about 150 to 300 ° C. is continuously introduced into the pipe body 2.
The waste plastic introduced into the tube body 2 is gradually pyrolyzed in the absence of oxygen while passing through the plastic body, is reduced in molecular weight, and is evaporated. The evaporated gas component is introduced from the discharge part 5 through the pipe 11 to the condenser 12 and cooled and condensed. The condensed oil component is recovered from the pipe 14 into an oil component recovery tank (not shown), and the remaining non-condensed gas component is introduced into the gas processing device 16 from the pipe 15 and is rendered harmless by, for example, combustion and discharged from the pipe 37.
[0013]
Residue that is not gradually decomposed accumulates in the pipe body 2 due to the operation of the thermal decomposition apparatus 1, and coke is fixed to the inner wall of the pipe body 2. The amount of residue generated is usually about 1% by weight of the amount of waste plastic introduced if it is pure, but impurities may be mixed in, and if it is operated for a certain period of time, it will accumulate considerably. To reach. When the amount of residues in the pipe body 2 reaches a predetermined amount, the thermal decomposition reaction in the pipe body 2 is stopped by closing the on-off valve 10 and stopping the introduction of waste plastic from the supply device 9. Then, after the thermal decomposition reaction substantially stops, the temperature in the tube body 2 is lowered to, for example, about 500 ° C. by adjusting the supply amount of the heating gas from the heating furnace 18, and the temperature is maintained thereafter.
[0014]
Next, the on-off valve 13 is closed, the on-off valves 20, 25 and 28 are opened, and the gas supply device 23 is operated to introduce an oxygen-containing gas, for example air, into the pipe body 2. The gas flow rate to the pipe body 2 is confirmed by the flow rate adjustment valve 22 with the flow meter 21 so that, for example, when the amount of residue is 1 kg or less, in the case of air, a relatively low value of about 1 to 10 m ³ / Hr is obtained. While adjusting. The larger the amount of oxygen, the shorter the time required for the oxidation treatment. However, the temperature in the tube body 2 decreases in proportion to this, so that as much oxygen-containing gas as possible flows as long as the temperature does not fall below an allowable value. It is desirable to adjust so that.
[0015]
The inside of the tube body 2 into which the oxygen-containing gas has been introduced is in a high-temperature oxidation state, and residues present there are efficiently oxidized. Residue organic substances react with oxygen and decompose into carbon dioxide (CO ₂ ) and water (H ₂ O) as described above, and the parts that cannot be decomposed are reduced in volume to reduce the inorganic content such as ash, sand, and metal fragments. Left as. Moreover, since the organic substance fixed as caulking is decomposed and carbonaceous substance is substantially lost, the adhesion force to the inner wall of the pipe body 2 is significantly reduced. Carbon monoxide (CO), soot, etc. generated by incomplete combustion or the like during the oxidation treatment is introduced into the gas treatment device 16 through the piping 24 and the piping 26 together with CO ₂ and H ₂ O. It is detoxified and discharged from the pipe 37.
[0016]
When the residues in the pipe body 2 are sufficiently oxidized, the on-off valve 28 is closed and the on-off valve 29 is opened, and the flow rate adjusting valve is further operated to adjust the flow rate of the oxygen-containing gas from the gas supply device 23. For example, it increases to about 30 to 70 m / s at the pipe flow velocity. Due to this increase, the oxide in the tube body 2 is forcibly discharged from the discharge portion 5 to the outside by a strong air blowing action, and further introduced into the dust collecting device 30 through the pipes 24 and 27, where the solid inorganic matter is removed. And discharged from the pipe 31. The inorganic matter accumulated in the dust collector 30 is periodically discharged from the pipe 32 to the outside.
When the residues in the pipe body 2 are discharged as described above, the amount of the heated gas from the heating furnace 18 is readjusted to increase the temperature in the pipe body 2 to the pyrolysis temperature, and the on-off valve 20, 25 is closed, the on-off valves 10 and 13 are opened, and the operation of the waste plastic thermal decomposition apparatus 1 is resumed.
In the above embodiment, as a method of supplying the oxygen-containing gas into the tube body 2, the pressure type gas supply device 23 is provided on the introduction part 4 side, but instead, a suction type blower is provided on the discharge part 5 side. For example, an oxygen-containing gas may be supplied into the tube main body 2 by suction.
[0017]
【The invention's effect】
As described above, according to the invention of the waste plastic pyrolysis apparatus according to claim 1,
When residues adhere to the inner surface of the tube body 2, it can be easily oxidized and decomposed, and the decomposed material can be captured by the dust collector 30 and the inside can be easily cleaned. That is, while the waste plastic thermal decomposition apparatus is moving, the first on-off valve 10 is closed to prevent the molten waste plastic from being introduced into the pipe body 2, and then the flow rate adjusting valve 22 is opened to an appropriate amount for pressurization. By supplying oxygen from the gas supply device 23, the residues in the tube body 2 can be oxidized. Next, the residual oxide generated by the oxidation treatment is blown off by the pressurized gas from the pressurized gas supply device 23 and is captured by the dust collector 30 through the third on-off valve 25 and the fourth on-off valve 29. be able to.
Note that the gas component generated by the oxidation treatment can be rendered harmless by the gas treatment device 16 via the fifth on-off valve 28.
[0018]
According to the cleaning method for the waste plastic thermal decomposition apparatus according to claim 2, the organic substance constituting the residue reacts with oxygen by oxidation treatment of the residue, so that carbon dioxide (CO ₂ ) or water (H ₂ O) is decomposed, and the portion that cannot be decomposed is reduced in volume and left as an inorganic component such as ash, sand, and metal pieces. And since the organic substance fixed as caulking is decomposed and carbonaceous substance is substantially lost, the adhesive force to the inner wall of the pipe body is remarkably reduced, and it is easily peeled off and discharged by air blow. Furthermore, even when the tube body is considerably long, the coking can be easily peeled off and discharged. In addition, this method can quickly shift to a high temperature oxidation state after the thermal decomposition reaction is stopped without once reducing the temperature in the tube body held at a high temperature during the thermal decomposition operation to room temperature, so that the time required for cleaning is reduced. Is short and energy consumption may be small.
Moreover, in order to set the flow rate of the pressurized gas supplied to the tube body to the first flow rate for treating the residue and to discharge the residual oxide after the oxidation treatment, the flow rate is higher than the first flow rate. Since the process is performed at the second flow rate, the remaining oxide can be reliably guided to the dust collector 30 and captured.
Further, according to the cleaning method of the present invention, since the harmful components in exhaust gas generated during the oxidation process may be detoxification or removal treatment in the gas treatment device, never contaminate the environment.
[Brief description of the drawings]
FIG. 1 is a schematic process flow diagram showing an example of a thermal decomposition apparatus for performing a cleaning method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Thermal decomposition apparatus 2 Pipe | tube main body 3 Heating part 4 Introduction part 5 Discharge part 6 Gas supply part 7 Gas discharge part 8 Pipe 9 Supply apparatus 10 On-off valve 11 Pipe 12 Condenser 13 On-off valve 14 Pipe 15 Pipe 16 Gas processing apparatus 17 Pipe 18 Combustion furnace 19 Pipe 20 On-off valve 21 Flow meter 22 Flow rate adjusting valve 23 Gas supply device 24 Pipe 25 On-off valve 26 Pipe 27 Pipe 28 On-off valve 29 On-off valve 30 Dust collector 31 Pipe 32 Pipe 33 Melting section 35 Melting extrusion screw 36 Rotating device 38 Hopper 37 Piping

Claims (2)

A tube body (2), a tubular heating section (3) surrounding the tube body (2), having a gas supply section (6) at one end and a gas discharge section (7) at the other end, and the gas A combustion furnace (18) connected to a supply unit (6), a waste plastic supply device (9) connected to one end of the pipe body (2) via a first on-off valve (10), and the pipe A pressurized gas supply device (23) connected to one end of the main body (2) via a flow rate adjusting valve (22) and capable of varying the flow velocity of the oxygen-containing pressurized gas supplied into the pipe main body (2). A condenser (12) connected to the other end of the pipe body (2) via a second on-off valve (13), and a third end connected to the other end of the pipe body (2). On-off valve (25), a fourth on-off valve (29) having one end connected to the other end of the third on-off valve (25), and the fourth on-off valve (29 A dust collecting device (30) connected to the other end of the second on-off valve, a fifth on-off valve (28) having one end connected to the other end of the third on-off valve (25), and a fifth on-off valve ( 28) A waste plastic pyrolysis apparatus comprising a gas processing apparatus (16) connected to the other end of the apparatus. Introducing heated gas into the cylindrical heating section (3) surrounding the pipe body (2) and heating the heating section (3), and introducing molten waste plastic from one end of the pipe body (2) A step of thermally decomposing the molten waste plastic into a gaseous state in the pipe body (2), and introducing the pyrolyzed gas into the condenser (12) to condense the condensed oil component and the non-condensed gas component. A step of generating, a step of introducing the gas component into the gas processing device (16) and detoxifying, and a step of stopping the supply of the molten waste plastic to the pipe body (2),
Next, a first step of introducing an oxygen-containing pressurized gas having a first in-pipe flow rate into the pipe body (2) to oxidize residues in the pipe body (2), and this oxidation treatment Introducing the generated gas component into the gas processing device (16) to render it harmless;
Subsequently, the step of increasing the flow rate in the pipe of the oxygen-containing pressurized gas introduced into the pipe body (2) to a second pipe flow rate larger than the pipe flow rate in the first step, and thereby the pipe body ( And 2) a step of forcibly discharging the residual oxide from the pipe body and introducing it into the dust collector (30).

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