JP5132093B2 - Waste plastic thermal decomposition treatment apparatus and thermal decomposition treatment method - Google Patents

Description

  The present invention relates to a thermal decomposition treatment apparatus installed in a waste plastic oil treatment apparatus.

In recent years, efforts to form a recycling-oriented economic society have begun in various fields, and the need to recycle waste plastics is also increasing. As one of the recycling processes of waste plastics, a process called oil conversion for extracting oil from waste plastics is known. In such an oiling treatment, waste plastic is first put into a pyrolysis tank, and the waste plastic in the pyrolysis tank is pyrolyzed to generate pyrolysis gas, and the generated pyrolysis gas is cooled to remove oil. It has gained. However, in such an oil conversion treatment, a residue is generated together with the pyrolysis gas when the waste plastic is thermally decomposed in the pyrolysis tank, and the residue adheres to the inner wall (including the bottom surface) of the pyrolysis tank. Therefore, in order to facilitate the discharge operation of the adhered residue, for example, the oil treatment apparatus described in Patent Document 1 is configured to thermally decompose waste plastic with an inner pot that can be attached to and detached from the thermal decomposition tank. ing. In this apparatus, when collecting the waste plastic residue, the inner pot can be removed from the thermal decomposition tank and the residue in the inner pot can be taken out. However, even in the thermal decomposition treatment apparatus as described in Patent Document 1, since the residue adheres to the inner wall of the inner pot, the work of scraping and removing the adhered residue is necessary as in the case of the conventional apparatus, and production There was a problem that the improvement of the property was not sufficient. In order to solve this problem, for example, in a thermal decomposition apparatus as described in Patent Document 2, a stirrer is installed in the thermal decomposition tank, and the waste plastic in the thermal decomposition tank is melted while being stirred by the stirrer. Therefore, the residue is difficult to adhere to the inner wall of the pyrolysis tank.
JP-A-8-170081 JP-A-9-13044

  However, the stirrer described in Patent Document 2 always rotates at a constant rotation speed regardless of the viscosity of the waste plastic in the pyrolysis tank. For this reason, in the case of unmelted waste plastic that has just been thrown into the waste plastic in the pyrolysis tank, the stirrer collides with the unmelted waste plastic, and the stirrer blade of the stirrer is damaged, There is a problem of being damaged.

  Therefore, an object of the present invention is to provide a highly durable pyrolysis apparatus capable of easily collecting and removing residues in the pyrolysis tank and preventing the stirrer from being damaged.

  A thermal decomposition treatment apparatus according to the present invention is made to solve the above-described problems, and is a thermal decomposition treatment apparatus installed in a waste plastic oil conversion treatment system, which heats waste plastic by heating by a heating means. A pyrolysis tank for decomposition, a stirrer rotatably supported in the pyrolysis tank, agitating waste plastic, a torque detection means for detecting a load torque acting on the agitator, and detected by the torque detection means Control means for controlling the rotation of the stirrer according to the applied load torque.

  In a general pyrolysis apparatus, the control means is configured to control the rotation of the stirrer, for example, by detecting the temperature of the waste plastic or the temperature in the pyrolysis tank, and performing the control according to the detected temperature. Can be considered. However, since various waste plastics are usually charged into the pyrolysis tank, the temperature at which melting starts varies depending on the type of waste plastics charged. In this way, the temperature at which melting starts depends on the type of waste plastic, so it is difficult to determine the melting state of waste plastic from the detected temperature in the pyrolysis tank. The waste plastic which has not been agitated may be agitated and the agitator may be damaged. On the other hand, according to the above-described configuration of the thermal decomposition treatment apparatus according to the present invention, the rotation of the agitator is controlled by the control means according to the load torque acting on the agitator rather than the temperature in the pyrolysis tank. Yes. Here, the load torque acting on the stirrer varies depending on the molten state of the waste plastic. Therefore, by controlling the rotation of the stirrer according to the load torque acting on the stirrer, the rotation of the stirrer can be controlled according to the molten state of the waste plastic in the pyrolysis tank.

  In particular, the control means can be configured to control the stirrer to start stirring when the detected load torque is not more than a predetermined value. By configuring in this way, for example, when the load torque acting on the stirrer is large, that is, in a state where the viscosity of the waste plastic in the pyrolysis tank is high or the waste plastic is not melted, the stirrer It can be controlled not to stir. And when the load torque which acts on a stirrer begins to become small, ie, when the waste plastic in a thermal decomposition tank begins to melt and a viscosity begins to become low, it can control so that a stirrer may begin to stir. For this reason, when the viscosity of the waste plastic is high, or when the waste plastic is not melted, the stirrer can be prevented from being damaged due to the start of stirring.

  Moreover, the said control means can be comprised so that the temperature in a thermal decomposition tank may be further controlled. That is, the control means raises the temperature in the pyrolysis tank so that the temperature rises to a second temperature for carbonizing the waste plastic after raising the temperature to the first temperature for generating pyrolysis gas from the waste plastic. It is preferable to control the temperature.

  Thus, instead of suddenly raising the temperature in the pyrolysis tank to the temperature for carbonizing, for example, the temperature is temporarily raised to the first temperature for generating pyrolysis gas, and the first temperature is increased. Is maintained for a predetermined time, and then the carbon content in the pyrolysis gas can be reduced by raising the temperature in two stages so as to raise the temperature to the second temperature. to enable.

  A thermal decomposition treatment method according to the present invention is made to solve the above-mentioned problems, and is a method for thermally decomposing waste plastic in a waste plastic oil conversion treatment system, and pyrolyzing waste plastic. A charging step for charging into the tank, and a thermal decomposition step for thermally decomposing the waste plastic in the pyrolysis tank, wherein in the thermal decomposition step, the waste plastic heated according to the viscosity is agitated To stir.

  According to this method, since the stirring is performed according to the viscosity of the waste plastic, the stirring can be stopped when the waste plastic has a high viscosity, that is, when the melting of the waste plastic has not started. Damage to the instrument can be prevented.

  In the above method, it is preferable to detect a load torque acting on the stirrer and control the rotation of the stirrer according to the load torque.

  The pyrolysis step includes a step of generating pyrolysis gas from waste plastic at a first temperature, and a step of carbonizing waste plastic after generating pyrolysis gas at a second temperature higher than the first temperature. Are preferably provided. Thus, by performing two-step temperature increase, the carbon content in the pyrolysis gas can be reduced, and as a result, high-quality oil can be recovered.

  In addition, since the residue is obtained in a dry state after the above method, it is further provided with a recovery and removal step of recovering and removing the residue generated in the thermal decomposition layer by suction with a suction device after the thermal decomposition step. May be. Thereby, the residue can be recovered and removed more easily.

  Also, at least two pyrolysis tanks are prepared, and after passing through the charging step and the pyrolysis process in one pyrolysis tank, a process of cooling the pyrolysis tank is performed, and in the other pyrolysis tank, While performing the cooling process in the pyrolysis tank, the pyrolysis process may be started. Thus, by using two pyrolysis tanks alternately, the cooling time of the pyrolysis tank which normally requires a long time can be used effectively, and productivity can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the durable thermal decomposition apparatus which can collect | recover the residue in a thermal decomposition tank easily and can prevent damage to a stirrer can be provided.

  Hereinafter, an embodiment of a thermal decomposition treatment apparatus for waste plastic according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a flowchart of a waste plastic oil processing system in which a thermal decomposition processing apparatus according to this embodiment is installed.

  As shown in FIG. 1, the thermal decomposition processing apparatus 1 according to the present embodiment is installed in a waste plastic oil conversion processing system 10. Here, first, the waste plastic oil converting system 10 will be described. In the uppermost stream of the waste plastic oil conversion processing system 10, there is disposed a thermal decomposition treatment apparatus 1 for thermally decomposing waste plastic to be treated and generating pyrolysis gas from the waste plastic. A tar removing device 200 for removing tar in the pyrolysis gas and a catalyst device 300 for reforming the pyrolysis gas are arranged in this order downstream of the pyrolysis treatment device 1. Further, a condensing device 400 for cooling and condensing the pyrolysis gas to produce oil and an oil / water separating device 500 for separating water from the produced oil are arranged downstream of this. The oil from which water has been separated is stored in the oil tank 600, and hydrogen chloride in so-called off-gas that is not condensed by the condensing device 400 is removed by the desalting device 700. Hereafter, each apparatus mentioned above is demonstrated.

  FIG. 2 is a side sectional view of the thermal decomposition processing apparatus 1, and FIG. 3 is a front sectional view of the thermal decomposition processing apparatus 1. As shown in FIGS. 2 and 3, the thermal decomposition treatment apparatus 1 includes a thermal decomposition tank 2 that thermally decomposes waste plastic, and a furnace section (heating means) 6 that heats the thermal decomposition tank 2. The pyrolysis tank 2 is configured in a cylindrical shape having a curved bottom surface 21 and an upper surface 22 bulging in a bowl shape, and is configured to be accommodated in the furnace section 6. The upper surface 22 of the pyrolysis tank 2 is provided with a lid portion 23 that can be opened and closed for charging waste plastic, and a discharge pipe 24 that discharges pyrolysis gas generated from the waste plastic. The exhaust pipe 24 is configured to communicate with the first gas pipe 210 connected to the tar removing device 200 when the pyrolysis tank 2 is installed in the furnace section 6. Further, a temperature measuring instrument 25 for measuring the temperature in the tank is installed on the upper surface 22 of the pyrolysis tank 2. The control device 5 shown in FIG. 1 is connected to the temperature measuring instrument 25, receives the temperature signal in the pyrolysis tank 2 measured by the temperature measuring instrument 25, and according to the temperature in the pyrolysis tank 2. Adjust the burner firepower.

  Moreover, the agitator 3 for agitating the waste plastic in the pyrolysis tank 2 is rotatably supported by the pyrolysis tank 2. The stirrer 3 is a rotating shaft 31 that is rotatably supported through the upper surface 22 of the pyrolysis tank 2, and a stirring blade that is fixedly attached to the lower end 311 of the rotating shaft 31 and stirs the inside of the pyrolysis tank 2. 32, and a motor 33 that rotates the rotating shaft 31 is attached to the upper end of the rotating shaft 31. The stirring blade 32 includes a curved portion 321 formed along the bottom surface 21 swelled like a bowl and a straight portion 322 connecting both ends of the curved portion. The rotating shaft 31 is connected. A torque sensor (torque detection means) 4 is attached near the upper end of the rotating shaft 31 of the stirrer 3, and the torque sensor 4 detects a load torque acting on the stirrer 3 by waste plastic. The control device 5 described above is also connected to the stirrer 3 and controls the rotation of the stirrer 3 by controlling the motor 33 according to the load torque detected by the torque sensor 4.

  The furnace section 6 is open at the top, and is configured to accommodate the pyrolysis tank 2 from the opening. Moreover, in order to heat the accommodated thermal decomposition tank 2, the burner 61 is installed in each of the opposing side wall. The burner 61 is connected to a service tank 62 and a desalting apparatus 700, and burns using off-gas from the desalting apparatus 700 described later and oil from the service tank 62 as fuel. The service tank 62 is connected to a control device 5 that controls the fuel supply amount.

  Returning to FIG. 1, the description of the oil processing system 10 will be continued. As shown in the figure, the discharge pipe 24 of the pyrolysis apparatus 1 is connected to the first gas pipe 210, and the pyrolysis gas generated in the pyrolysis apparatus 1 is supplied to the tar removal apparatus 200.

  FIG. 4 is an enlarged front view showing the tar removing device 200 and the catalyst device 300. As shown in FIG. 4, the tar removing device 200 includes a cylindrical body 201 having a hollow cylindrical shape, and a certain amount of oil 204 is sealed in the cylindrical body 201 so that a space is formed in the upper portion. A supply line 205 for supplying oil 204 from an external oil supply source (not shown) is connected to the side surface of the upper space portion of the cylindrical main body 201. The supply line 205 is provided with a valve 206 that can be opened and closed. Note that the valve 206 can be automatically controlled so that the oil 204 is automatically opened when the oil 204 in the cylindrical main body 201 is reduced to supply oil into the cylindrical main body 201. Here, the temperature of the oil is preferably 250 to 350 ° C, and more preferably 280 to 320 ° C.

  Further, the tar removing device 200 includes a supply pipe 207 that supplies the pyrolysis gas from the first gas pipe 210 into the cylindrical main body 201. The supply pipe 207 is formed in an L shape that bends downward. That is, while extending from the outside of the cylindrical main body 201 to the upper space through the outer peripheral surface, the lower end 208 extends downward so that the lower end 208 is located in the oil 204. The other end 209 of the supply pipe 207 extending to the outside of the cylindrical main body 201 is connected to the first gas pipe 210. Thus, since the lower end 208 of the supply pipe 207 is located in the oil 204, the pyrolysis gas discharged from the supply pipe 207 and proceeding into the upper space of the cylindrical body 201 is used for the oil 204. There is no back flow to the supply pipe 207, and consequently no back flow to the thermal decomposition treatment apparatus 1. Further, since the lower end 208 of the supply pipe 207 is opened downward, the tar naturally cooled and solidified in the first gas pipe 210 is supplied from the lower end 208 of the supply pipe 207 and is supplied to the cylindrical body 201. It is comprised so that it may fall to a bottom face. In order to discharge tar falling on the bottom surface to the outside as described above, a discharge pipe 202 having a valve 203 that can be freely opened and closed is provided on the bottom surface of the cylindrical main body 201. Further, a discharge part 211 configured to be connected to the second gas pipe 310 is provided on a side surface of the upper space of the cylindrical main body 201, and configured to discharge the pyrolysis gas from which tar has been removed to the catalyst device 300. Has been.

  The catalyst device 300 includes a cylindrical body 301 having a hollow cylindrical shape, and the inside of the cylindrical body 301 is filled with a catalyst for reforming pyrolysis gas, such as a zeolite catalyst. Further, the bottom end of the cylindrical main body 301 is connected to the upper end of the three ends of the trifurcated connecting pipe 302. The horizontal end of the connecting pipe 302 facing the horizontal direction is connected to the second gas pipe 310, and the lower end of the connecting pipe 302 is connected to a discharge pipe 303 having an openable / closable valve 304. As described above, since the lower end of the connection pipe 302 is connected to the discharge pipe 303, even when the pyrolysis gas is discharged to the second gas pipe 310 without the tar being sufficiently removed by the tar removal device 200. The tar is solidified by being naturally cooled in the second gas pipe 310, falls from the lower end of the connection pipe 302 to the discharge pipe 303 by gravity, and can be discharged to the outside by opening the valve 304. In addition, a discharge part 305 configured to be connected to the third gas pipe 410 is provided on the outer peripheral surface of the cylindrical main body 301.

  FIG. 5 is a front sectional view showing the condensing device 400, and FIG. 6 is an enlarged view showing details of the partition 404 of the condensing device 400 as viewed from the A direction. As shown in FIG. 5, the condensing device 400 includes a hollow cylindrical cooling tank 401 and a stock tank 406. The cooling tank 401 is installed such that its axial direction is horizontal, a supply unit 402 is formed at the upper part on one end side, and a discharge unit 403 is formed at the upper part on the other end side. A third gas pipe 410 from the catalyst device 300 is connected to the supply unit 402, and a fourth gas pipe 710 connected to the demineralizer 700 is connected to the discharge unit 403. The cooling tank 401 is provided with five partition walls 404 so as to divide the inside thereof into six chambers in the axial direction (left-right direction in FIG. 5). As shown in FIG. 6, a plurality of holes 405 are formed in the upper half of the partition wall 404, and the pyrolysis gas can pass through the holes 405.

  In addition, a water channel (not shown) for flowing cooling water is formed on the outer peripheral surface of the cooling tank 401. The cooling water flowing on the outer peripheral surface of the cooling tank 401 is cooled and condensed while the pyrolysis gas flows through the cooling tank 401 from the supply unit 402 to the discharge unit 403 through the hole 405 of the partition wall 404, and oil in each chamber. Is generated. The pyrolysis gas is cooled in the cooling tank 401 as it proceeds from the supply unit 402 to the discharge unit 403. Therefore, the oil having a high boiling point is generated by being condensed in the chamber on the supply unit 402 side. Is generated in the chamber on the discharge unit 403 side, and the chamber in which oil is generated can be divided by the difference in boiling point.

  The stock tank 406 is installed below the cooling tank 401 in order to stock oil generated in each chamber of the cooling tank 401. The stock tank 406 is formed with a plurality of chambers so as to correspond to the respective chambers of the cooling tank 401, and each chamber of the stock tank 406 is connected to the corresponding cooling tank 401 via a connecting pipe 407 having a valve 408. Connected to each room. Each chamber of the stock tank 406 is connected to a pipe 409 for sending the stocked oil to the oil / water separator 500 shown in FIG.

  The oil / water separator 500 is configured to separate oil and water using the difference in specific gravity between oil and water. An oil tank 600 for storing oil from which water has been separated is installed downstream of the oil / water separator 500.

  As shown in FIG. 1, the fourth gas pipe 710 connected to the discharge unit 403 of the cooling tank 401 described above is connected to the desalting apparatus 700.

  FIG. 7 is a front sectional view showing the desalting apparatus 700. As shown in FIG. 7, the desalting apparatus 700 includes a hollow cylindrical cylindrical main body 701. The cylindrical body 701 is installed so that its axial direction is horizontal. In addition, the cylindrical main body 701 is formed with a partition wall 702 that divides the cylindrical main body 701 into two chambers in the axial direction (left-right direction in FIG. 7). The partition wall 702 is not formed up to the upper part of the cylindrical main body 701. For this reason, the two chambers of the cylindrical main body 701 communicate with each other at the upper part. Water 703 is stored in one of the two chambers of the cylindrical body 701, and off-gas is supplied to this water.

  In addition, the desalting apparatus 700 includes a supply pipe 705 that supplies the off gas from the fourth gas pipe 710 into the cylindrical main body 701. The supply pipe 705 is formed in an L shape that is bent in the horizontal direction. In other words, the connecting portion 707 that penetrates the outer peripheral surface from the outside of the cylindrical main body 701 and extends vertically downward into the water 703 and the one end of the connecting portion 707 that extends into the water 703 and horizontally extends in the water 703. Part 706. The other end of the connecting portion 707 extending to the outside of the cylindrical main body 701 is connected to the fourth gas pipe 710. The supply unit 706 has a plurality of holes, and off-gas is supplied into the water 703 from the holes. As described above, since the supply unit 706 is disposed in the water 703, the off-gas supplied from the supply unit 706 and rising as bubbles in the water 703 is prevented from flowing back due to the water 703.

  A spray tube 704 extends horizontally above the other chamber partitioned by the partition wall 702. The spray pipe 704 extends through the cylindrical main body 701 and is connected to a sodium hydroxide aqueous solution supply source (not shown) so as to spray the sodium hydroxide aqueous solution into the other chamber of the cylindrical main body 701. It is configured. Thus, since the sodium hydroxide aqueous solution is sprayed from the spray pipe 704, the sodium chloride aqueous solution is accumulated in the other chamber of the cylindrical main body 701, but the cylindrical main body is prevented from flowing into the one chamber. A second discharge portion 709 is provided at a position lower than the upper end of the partition wall 702 of 701. A first discharge part 708 is provided at the upper part of the other chamber side end of the cylindrical main body 701, and the first discharge part 708 is connected to a fifth gas pipe 810 connected to the burner 61. Instead of spraying the sodium hydroxide aqueous solution as described above, the sodium hydroxide aqueous solution can be injected into the other chamber in advance.

  Next, an oil treatment method by the waste plastic oil treatment system 10 configured as described above will be described with reference to the drawings.

  First, as shown in FIGS. 1, 2 and 3, the lid portion 23 of the thermal decomposition tank 2 arranged at the charging position is opened, and waste plastic is charged through this opening.

  After waste plastic is put into the pyrolysis tank 2 by various means and the lid portion 23 is closed, the pyrolysis tank 2 is moved from the charging position by a crane or the like and accommodated in the furnace section 6. The discharge pipe 24 extending from the upper part of the first gas pipe 210 connected to the tar removing device 200 is connected.

  After the pyrolysis tank 2 is installed in the furnace section 6 in this way, the controller 5 starts fuel supply from the service tank 62 to start combustion of the burner 61, and heats the pyrolysis tank 2. When the temperature in the pyrolysis tank 2 is gradually increased by heating the pyrolysis tank 2 with the burner 61, the waste plastic in the pyrolysis tank 2 starts to melt.

  On the other hand, after the thermal decomposition tank 2 is installed in the furnace section 6, the rotating shaft 31 of the stirrer 3 is rotated at a predetermined rotational speed by the motor 33. By rotating the rotary shaft 31 with the motor 33 in this way, a load torque due to waste plastic in the pyrolysis tank 2 acts on the stirring blade 32. Here, the load torque acting on the stirring blade 32 varies depending on the molten state of the waste plastic. Therefore, when the load torque is larger than a predetermined value, that is, when the waste plastic is not melted or starts to melt, the motor 33 rotates the rotating shaft 31 with a low driving torque so that the stirring blade 32 does not stir. Is rotating. As described above, when the waste plastic starts to melt by increasing the temperature in the pyrolysis tank 2, the viscosity of the waste plastic decreases and the load torque acting on the stirring blade 32 also decreases. When the load torque becomes equal to or less than a predetermined value, the control device 5 that detects the load torque increases the drive torque to the rotating shaft 31 by the motor 33 so as to overcome the load torque and starts stirring of the stirring blade 32. Here, the predetermined value for starting stirring of the stirring blade 31 varies depending on the output of the motor 33, the strength of the stirrer 3, the amount of waste plastic in the thermal decomposition tank 2, and the like, but 6 to 12 N / It is preferable to use mm. Thus, stirring of the stirrer 3 is started according to the molten state of the waste plastic.

  Thus, by continuing the heating of the pyrolysis tank 2 by the burner 61 while stirring the waste plastic in the pyrolysis tank 2 with the stirrer 3, the temperature in the pyrolysis tank 2 is increased as shown in the graph of FIG. Raise. FIG. 8 is a graph in which the horizontal axis is the heating time t (minutes) and the vertical axis is the temperature (° C.) in the pyrolysis tank 2. Here, when the temperature in the pyrolysis tank 2 is increased to 500 to 600 ° C., which is a temperature for generating pyrolysis gas, at a stretch, the carbon-carbon bond of the waste plastic is heated without being sufficiently cut. Since the gas is generated by decomposition, the generated pyrolysis gas has a large number of carbon atoms.

Therefore, in this embodiment, to increase the first temperature in the thermal cracking bath 2 to 300 to 400 ° C., which is the first temperature T _1, the carbon in the waste plastics in the process - with cut carbon bond, the burner 61 The heating of the pyrolysis tank 2 is continued. And if the control apparatus 5 detects that the temperature in the thermal decomposition tank 2 rose to _1st temperature T1 with the signal from the temperature measurement apparatus 25, the control apparatus 5 will hold | maintain _1st temperature T1. The heating power of the burner 67 is controlled by adjusting the amount of fuel supplied from the service tank 62. In addition, it is preferable to hold | maintain _1st temperature T1 for 180 to 240 minutes. Then, after maintaining the first temperature T ₁ for the predetermined time, the second temperature T ₂ is a _second temperature T ₂ for further pyrolyzing the waste plastic to generate pyrolysis gas from the first temperature T _1. The heating power of the burner 61 is controlled by adjusting the fuel supply amount from the service tank 62 by the control device 5 so that the temperature in the pyrolysis tank 2 rises to ˜600 ° C. When the temperature in the pyrolysis tank 2 rises to the second temperature, the waste plastic starts to pyrolyze and pyrolysis gas is generated. This pyrolysis gas is discharged from the discharge pipe 24 and sent to the tar removing device 200. In this way, the temperature rise is temporarily stopped at the first temperature T ₁ and held for a predetermined time, and then the temperature is raised to the second temperature T ₂ to sufficiently cut the carbon-carbon bond of the waste plastic. A pyrolysis gas having a small number of carbon atoms can be generated.

After maintaining the second temperature T ₂ for about 1 hour and sufficiently generating pyrolysis gas from waste plastic, heating by the burner 61 is stopped and the pyrolysis tank 2 is naturally cooled. In this case, for example, forced cooling can be performed by sending air to the thermal decomposition tank 2 by a blower. The stirrer 3 continues to stir during cooling of the pyrolysis tank 2. In such pyrolysis treatment of waste plastic, carbide called residue is generated simultaneously with pyrolysis gas. Therefore, after the pyrolysis tank 2 is sufficiently cooled, the lid portion 23 of the pyrolysis tank 2 is opened, and the residue in the pyrolysis tank 2 is sucked and collected from there by a suction machine (not shown). In addition, since the waste plastic melted by the stirrer 3 is agitated during the thermal decomposition step, the residue in the thermal decomposition tank 2 becomes a powder instead of a lump and can be easily sucked and collected with a suction machine or the like. Can be recovered.

  In this way, pyrolysis gas is generated by the pyrolysis treatment apparatus 1, and generally tar, which is a viscous brown or black liquid, is obtained when waste plastic is pyrolyzed. In the thermal decomposition treatment apparatus 1 according to this embodiment, in order to perform thermal decomposition at a high temperature of about 500 to 600 ° C., the tar is vaporized and mixed in the thermal decomposition gas. The pyrolysis gas moves in the gas pipe to perform various treatments. During the movement in the gas pipe, the pyrolysis gas is naturally cooled at the outside temperature, so that the vaporized tar in the pyrolysis gas is solidified. There is a risk of adhering to the inside of the pipe and blocking the gas pipe. Therefore, in order to solve this problem, the pyrolysis gas generated by the pyrolysis apparatus 1 is supplied to the tar removing apparatus 200 via the first gas pipe 210.

  As shown in FIG. 4, the pyrolysis gas supplied to the tar removing device 200 is supplied from the lower end 208 of the supply pipe 207 and rises as bubbles in the oil 204 and proceeds to the upper space, and the second gas. It is discharged to a discharge unit 211 connected to the pipe 310 and sent to the catalyst device 300. At this time, from the lower end 208 of the supply pipe 207, the vaporized tar in the pyrolysis gas naturally cooled and solidified in the first gas pipe 210 falls to the bottom surface of the cylindrical main body 201 by gravity. When a certain amount of tar accumulates on the bottom surface, it is discharged from the discharge pipe 202 together with the oil 204 in the cylindrical body 201. Note that this operation may be performed after the end of the oil treatment cycle, or may be performed automatically during the oil treatment cycle. At this time, the oil 204 in the cylindrical main body 201 is reduced by being discharged together with tar, but is maintained at a predetermined amount by being manually or automatically replenished from a supply line 205 connected to an external oil supply source.

  The pyrolysis gas sent to the upper space of the cylindrical main body 201 is discharged from the discharge unit 211 and supplied to the catalyst device 300 via the second gas pipe 310. The pyrolysis gas supplied to the catalyst device 300 is supplied to the cylindrical main body 301 filled with the catalyst via the connecting pipe 302. The pyrolysis gas passes through the cylindrical body 301 and comes into contact with the catalyst to be reformed into a low boiling point gas. The reformed pyrolysis gas is discharged from the discharge unit 305 to the third gas pipe 410 and supplied to the condensing device 400. In addition, a heater or a heat insulating material can be attached to the first, second, and third gas pipes 210, 310, and 410 to keep the temperature, and thus generation of tar can be suppressed. Moreover, it is effective in suppressing generation | occurrence | production of tar also by shortening each gas pipe as much as possible.

  As shown in FIGS. 5 and 6, the pyrolysis gas from the third gas pipe 410 is supplied from the supply unit 402 into the cooling tank 401. The pyrolysis gas supplied into the cooling tank 401 is gradually cooled by the cooling water flowing on the outer surface of the cooling tank 401 while passing through the hole 405 of the partition wall 404 and proceeding to the discharge unit 403. As described above, the pyrolysis gas is condensed by being cooled, and oil is generated in each chamber. The oil produced in each chamber is a heavy oil with a high boiling point in the chamber on the supply unit 402 side, and the oil produced in the chamber on the discharge unit 403 side is a light oil with the lowest boiling point. It has become. When oil generated in each chamber accumulates to some extent, the valve 408 is opened and sent to the corresponding chamber of the stock tank 406 via the connecting pipe 407. Then, the oil stocked in each chamber of the stock tank 406 is sent to the oil / water separator 500 through a pipe 409 by a pump. The oil whose water has been separated by the oil / water separator 500 is sent to the oil tank 600 by a pump. It is also possible to change the temperature of the cooling water so that the temperature decreases from the supply unit 402 side toward the discharge unit 403 side. Accordingly, it is possible to reliably obtain oil having a high boiling point on the supply unit 402 side and oil having a low boiling point on the discharge unit 403 side.

  Here, the pyrolysis gas contains components that are not condensed by the condensing device 400. For this reason, so-called off-gas discharged from the discharge unit 403 without being condensed in the cooling tank 401 of the condenser 400 is supplied to the desalinator 700 through the fourth gas pipe 710.

  As shown in FIG. 7, the off-gas sent from the fourth gas pipe 710 to the supply pipe 705 is supplied from the supply unit 706 into the water 703 and rises in the water 703 as bubbles. The off-gas that has risen to the water surface is sprayed with an aqueous solution of sodium hydroxide from the spray pipe 704 in the other chamber until it passes over the partition 702 and travels toward the first discharge part 708. By spraying the aqueous sodium hydroxide solution in this way, hydrogen chloride in the off-gas is neutralized. The off-gas from which hydrogen chloride has been neutralized and removed is discharged from the first discharge unit 708 and then supplied to the burner 61 through the fifth gas pipe 810 and burned as fuel for the burner 61. By repeating the above cycle, waste plastic is recycled.

  As described above, according to the thermal decomposition treatment apparatus 1 according to the present embodiment, the control device 5 controls the rotation of the stirrer 3 in accordance with the load torque acting on the stirrer 3 that changes depending on the molten state of the waste plastic. ing. For this reason, the rotation of the stirrer 3 can be controlled according to the molten state of the waste plastic in the pyrolysis tank 2, and as a result, damage to the stirrer 3 and the like can be prevented, and highly durable pyrolysis treatment The device 1 can be obtained.

  In particular, in this embodiment, when the load torque acting on the stirrer 3 is equal to or less than a predetermined value, the control device 5 controls the stirrer 3 to start stirring. Therefore, when the load torque is large, i.e., when the waste plastic is not melted or in a high viscosity state at which the plastic starts to melt, for example, the load torque acting on the stirrer 3 is large. Can be controlled to not. And when the load torque which acts on the stirrer 3 begins to become small, ie, when the waste plastic in a thermal decomposition tank begins to melt and a viscosity begins to become low, it can control so that the stirrer 3 may begin to stir. For this reason, when the viscosity of the waste plastic is high, or when the waste plastic is not melted, the stirrer can be prevented from being damaged due to the start of stirring.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these, A various change is possible unless it deviates from the meaning of this invention. For example, in the past, in order for the residue in the pyrolysis tank to be agglomerated and fixed in the pyrolysis tank, the pyrolysis tank is moved to a turntable for inverting the pyrolysis tank, and the pyrolysis tank is inverted. The internal residue was scraped off. However, in this embodiment, since the residue is in a powder form, it can be sucked and collected with a suction machine or the like without moving the pyrolysis tank. Therefore, the space for installing the turntable for inverting the pyrolysis tank is omitted. Therefore, in the above-described embodiment, the description is made on the assumption that there is only one pyrolysis tank 2, but two pyrolysis tanks 2 can be installed using the omitted space. Thereby, while one pyrolysis tank is being cooled, pyrolysis can be performed in the other pyrolysis tank, so that productivity can be improved.

  Moreover, in the said embodiment, although it comprises so that stirring may be started when the load torque which acts on the stirring blade 32 becomes below a predetermined value, for example, the melt viscosity of waste plastics by the fall of heating temperature etc. during stirring is carried out. When the load torque received by the stirrer becomes higher than a predetermined value, the stirring is stopped. When the melt viscosity of the waste plastic becomes lower again and the load torque becomes lower than the predetermined value, the control device 5 starts the stirring. You may control.

  Moreover, in the said embodiment, in order to start stirring of the stirrer 3, the drive torque to the rotating shaft 31 by the motor 33 is increased, but besides this, for example, the motor 33 and the rotating shaft 31 are connected. By connecting via the clutch device, stirring of the stirrer 3 can be started while the driving torque by the motor 33 is kept constant. That is, when the load torque acting on the stirring blade 32 is larger than a predetermined value, the clutch device is engaged (half-clutch) so that only a part of the driving torque from the motor 33 is transmitted to the rotating shaft 31. Thus, the stirring blade 32 is controlled not to stir. When the load torque acting on the stirring blade 32 becomes a predetermined value or less, the control device 5 that detects this causes the clutch device to be completely fitted so that the drive torque from the motor 33 is completely transmitted to the rotating shaft 31. Then, stirring by the stirring blade 32 is started.

  In addition, the stirring blade 32 of the above embodiment may include a plurality of scraping claws extending toward the bottom surface 21 of the thermal decomposition tank 2. With such a configuration, even if a residue adheres to the bottom surface 21 of the thermal decomposition tank 2, the adhered residue can be scraped off with the scraping claw. Moreover, since resistance becomes small compared with scraping the residue adhering to the bottom face 21 in the whole curved part of the stirring blade with a plurality of scraping claws in this way, the burden on the motor 33 can be reduced.

It is a flowchart of the waste plastic oil-ized processing system in which the thermal decomposition processing apparatus which concerns on this embodiment is installed. It is an expanded side view which shows embodiment of the thermal decomposition processing apparatus which concerns on this invention. It is an enlarged front view which shows embodiment of the thermal decomposition processing apparatus which concerns on this invention. It is an enlarged view of a tar removal device and a catalyst device concerning this embodiment. It is sectional drawing of the condensing apparatus which concerns on this embodiment. It is an enlarged view which shows the partition of the condensing apparatus which concerns on this embodiment. It is sectional drawing of the desalination apparatus which concerns on this embodiment. It is a graph which shows the relationship between the temperature in the thermal decomposition tank of the thermal decomposition process of the thermal decomposition processing method which concerns on this invention, and time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermal decomposition processing apparatus 2 Thermal decomposition tank 3 Stirrer 4 Torque sensor (torque detection means)
5 Control means 6 Furnace part (heating means)

Claims (7)

A thermal decomposition processing apparatus installed in a waste plastic oil processing system,
A pyrolysis tank for pyrolyzing waste plastic by heating with a heating means;
A stirrer that is rotatably supported in the pyrolysis tank and stirs the waste plastic;
Torque detecting means for detecting load torque acting on the stirrer;
Control means for controlling the rotation of the stirrer according to the load torque detected by the torque detection means;
Equipped with a,
The said control means is a thermal decomposition processing apparatus which controls the said stirrer to start stirring, when the detected load torque is below a predetermined value . The control means includes
The temperature in the pyrolysis tank is controlled so that the temperature is raised to a second temperature in order to carbonize the waste plastic after the temperature is raised to a first temperature to generate pyrolysis gas from the waste plastic. Item 2. The thermal decomposition treatment apparatus according to Item 1. A method for thermally decomposing waste plastic in a waste plastic oil processing system,
A charging process for charging waste plastic into the thermal decomposition tank;
A pyrolysis step of heating and decomposing waste plastic in the pyrolysis tank,
In the thermal decomposition step, when the viscosity of the waste plastics is less than the predetermined value, the heated waste plastics begins to be agitated by stirrer, thermal cracking process. The thermal decomposition processing method according to claim 3 , wherein load torque acting on the stirrer is detected, and control is performed to start rotation of the stirrer when the detected load torque is equal to or less than a predetermined value . The pyrolysis step includes
Generating pyrolysis gas from waste plastic at a first temperature;
5. The thermal decomposition treatment method according to claim 3 , further comprising a step of carbonizing the waste plastic after generating the pyrolysis gas at a second temperature higher than the first temperature. The thermal decomposition treatment method according to any one of claims 3 to 5 , further comprising a recovery removal step of recovering and removing the residue generated in the decomposition layer by suction with a suction device after the thermal decomposition step. Preparing at least two pyrolysis tanks;
After passing through the charging step and the pyrolysis step in one pyrolysis tank, performing a step of cooling the pyrolysis tank,
The thermal decomposition treatment method according to any one of claims 3 to 6 , wherein, in the other thermal decomposition tank, the thermal decomposition process is started while the cooling process is performed in the one thermal decomposition tank.

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