JP2016060799A - Waste plastic liquefaction processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste plastic liquefaction processing apparatus in which the fouling of high boiling components to the equipment and piping after a thermal decomposition kettle, is suppressed, and the occurrence of occlusion is prevented.SOLUTION: Provided is a waste plastic liquefaction processing apparatus including a thermal decomposition kettle for thermally decomposing a waste plastic and producing a decomposition gas, and a condenser for cooling and liquefying the decomposition gas obtained by the thermal decomposition kettle to produce a regeneration oil, in which there is provided, above the thermal decomposition kettle, a reflux column for refluxing the decomposition gas obtained by the thermal decomposition kettle and returning the high boiling component in the decomposition gas to the thermal decomposition kettle.SELECTED DRAWING: Figure 1

Description

  This invention relates to an apparatus for producing recycled oil by decomposing waste plastics, and more specifically, is characterized by returning high boiling components in cracked gas obtained in a pyrolysis kettle to the pyrolysis kettle It is invention which concerns on the apparatus for manufacturing recycled oil from waste plastics.

  Conventionally, as a plastic recycling method, various methods for decomposing waste plastic to obtain recycled oil and the like have been studied. As an example of this method, a method is known in which waste plastic is pyrolyzed in a pyrolysis kettle to generate cracked gas, which is liquefied to obtain recycled oil.

  However, the obtained cracked gas may contain high boiling components such as wax. In this case, the high boiling component adheres to various devices after the pyrolysis kettle and piping between the devices to generate carbides, and in some cases, the piping and the like may be blocked. Moreover, when the wax content concentration is high, the solidification temperature of the obtained reclaimed oil is high, as will be apparent from Comparative Examples described later, and it tends to be difficult to use easily.

  On the other hand, a method is known in which the obtained cracked gas is sent to a catalytic reaction tank and a high-boiling component such as a wax is decomposed (Patent Document 1, etc.).

JP 2005-170986 A

However, even if a high-boiling component is reacted in this catalytic reaction tank, the high-boiling component remains without being decomposed, and there is a possibility that the subsequent apparatus or piping may become dirty or clogged.
Therefore, an object of the present invention is to prevent the high-boiling component from adhering to the apparatus and piping after the pyrolysis kettle and prevent clogging.

  The present invention relates to a pyrolysis kettle that pyrolyzes waste plastic to generate cracked gas, and a waste plastic oil conversion process having a condenser that cools and liquefies the cracked gas obtained in the pyrolysis kettle to obtain recycled oil The apparatus is provided with a reflux tower that recirculates the regenerated oil obtained in the pyrolysis kettle above the pyrolysis kettle, and the waste plastic oil conversion process returns high boiling components in the cracked gas to the pyrolysis kettle By using an apparatus, the above-mentioned problems have been solved.

  In this invention, a reflux tower is provided above the pyrolysis kettle, and the cracked gas generated in the pyrolysis kettle is sent to the reflux tower and refluxed, so that the high boiling component can be selectively returned to the pyrolysis kettle, It is possible to suppress the adhesion and blockage of dirt in subsequent pipes and devices.

The flowchart which shows the process of the waste plastic oil conversion processing apparatus which concerns on this invention In FIG. 1, a flow diagram showing a case where part of the product is returned to the reflux tower or the like. In FIG. 1, a flowchart showing a process of cooling the pyrolysis kettle

  As shown in FIG. 1, the waste plastic oil processing apparatus according to the present invention cools the cracked gas obtained in the pyrolysis kettle 11a which pyrolyzes the waste plastic M to produce cracked gas, and the pyrolysis kettle. It is an apparatus having a condenser 12 that is liquefied to obtain regenerated oil.

  Examples of the waste plastic to be treated in the present invention include polyolefins such as polyethylene and polypropylene, polystyrene, polyamide and the like.

  As a specific process, the process shown in FIG. 1 can be mentioned. First, the waste plastic M to be treated is cut (not shown) and washed and dried in the washing and drying step 13. Thereby, dust and moisture adhering to the waste plastic M can be removed, and liquefaction in the next process can be performed more easily. As this washing machine, Bun-Sen (manufactured by Kanemiya Co., Ltd.) and the like can be raised. Moreover, the said drying process can dry using the waste heat of the thermal decomposition pot 11a.

  The washed and dried waste plastic M is liquefied in the liquefaction step 14 to obtain molten waste plastic. The temperature at this time should just be the temperature which can melt | dissolve the target waste plastic, and if it is about 230 to 260 degreeC, it is enough. As an apparatus used for this liquefaction process, extruders, such as a single screw extruder and a twin screw extruder, etc. can be mention | raise | lifted.

  Next, the molten waste plastic is supplied to the thermal decomposition pot 11a and thermally decomposed into a decomposition gas. This pyrolysis pot 11a constitutes a pyrolysis furnace 11 together with a combustion furnace 11b that heats it, and the temperature of the pyrolysis pot 11a is adjusted by the combustion furnace 11b. An agitator (not shown) for agitating the molten waste plastic is provided inside the pyrolysis kettle 11a, so that the temperature inside the pyrolysis kettle 11a is made substantially uniform.

  The thermal decomposition temperature is preferably 370 ° C. or higher, and preferably 380 ° C. or higher. When it is lower than 370 ° C., it may be difficult to sufficiently thermally decompose the molten waste plastic. On the other hand, the upper limit of the thermal decomposition temperature is preferably 400 ° C, and preferably 390 ° C. When the temperature is higher than 400 ° C., evaporation and distillation (distillation) of the wax from the pyrolysis kettle becomes remarkable, and the yield of the regenerated oil may be deteriorated, and carbides accumulate in the pyrolysis kettle 11a. It becomes.

  The cracked gas obtained in the pyrolysis kettle 11a is sent to the reflux tower 15 provided above the pyrolysis kettle 11a and partially refluxed. As a result, high boiling components such as wax components accompanying the cracked gas are returned to the lower pyrolysis pot 11a. The reflux tower 15 may have a state in which reflux occurs, that is, a state in which the cracked gas and the liquefied gas of the cracked gas counter-flow. Examples thereof include a method of setting the height to such a level that the above-described object can be achieved, a method of cooling the reflux tower 15 to such an extent that the temperature inside the reflux tower 15 can enable liquefaction of the cracked gas, and the like. Moreover, you may fill the inside of the reflux tower 15 with a filler as needed. By using the packing material, the height of the reflux tower can be set low and the degree of cooling can be lowered.

  Further, as shown in FIG. 2, a part of the regenerated oil P that is a product stored in a liquid storage tank 18 to be described later may be extracted and cooled by the condenser 21, and then returned to the upper part of the reflux tower 15. . By doing in this way, it becomes possible to cool the cracked gas which went up to the reflux tower 15 by making direct contact with the regenerated oil P which is a product. The amount and temperature of the reclaimed oil P to be returned are appropriately selected according to the recovered amount of reclaimed oil, the amount of high boiling components contained in the reclaimed oil, the target degree of cooling, and the like. And by doing in this way, the effect of the cooling in the reflux tower 15 can be improved more, and the separation from the decomposition gas of a high boiling component can be made easier.

  The filler may be regular packing or irregular packing. The regular packing is preferable because it can keep the reflux state constant and can further reduce the pressure loss. This ordered packing has a large number of holes, and a flat plate or a net-like body having a large number of holes is processed into a cylindrical shape or a tower shape. And this regular packing is used in accordance with the diameter and height of the reflux tower 15. Examples of such regular packing include MC pack (manufactured by Matsui Machine Co., Ltd.) and the like.

In the reflux tower 15, the liquid high-boiling component and the liquefied cracked gas are returned to the lower pyrolysis tank 11 a, while the remaining cracked gas is sent to the condenser 12 from above the reflux tower 15. And the decomposition gas which can be liquefied here is liquefied. Next, the gas-liquid separator 16 separates the gas and liquid, and the gas component is purified by the purifier 17 and released as exhaust.
On the other hand, the regenerated oil P which is a liquid component is stored in the liquid storage tank 18 and used as a product.

  When the cooling effect in the condenser 12 is insufficient, there is a possibility that the decomposition gas in the gas state goes to the purification device 17. When this state may occur, as shown in FIG. 2, a part of the regenerated oil P, which is a product stored in the liquid storage tank 18, is extracted and cooled by the condenser 21. To the pipe to the condenser 12. By doing in this way, the cracked gas sent to the condenser 12 is cooled by the direct contact with the regenerated oil P, and cooling in the condenser 12 can be assisted. The amount and temperature of the reclaimed oil P to be returned are appropriately selected according to the recovered amount of reclaimed oil, the amount of high boiling components contained in the reclaimed oil, the target degree of cooling, and the like.

  By the way, when the high-temperature decomposition gas enters the condenser 12 as it is, there is a possibility that adhesion occurs on the inner surface of the heat exchange tube of the condenser 12 at the same time as liquefaction. Furthermore, in some cases, carbonization may occur if a high temperature state is maintained. In such a case, the inside of the condenser 12 needs to be cleaned, but it may not be removed by simple cleaning, and may need to be scraped off. On the other hand, a part of the cooled regenerated oil P is branched and allowed to flow in the form of a spray to the condenser 12 so that the high temperature gas and the cooled regenerated oil are brought into direct contact with each other, thereby reducing the temperature of the cracked gas. It is possible to prevent adhesion and carbonization to the inner surface of the heat exchange tube of the condenser 12.

  Further, when the cooling effect in the condenser 12 is insufficient, or when it is desired to adjust the components of the reclaimed oil P to be recovered, the second condenser and the second condenser are connected from the gas-liquid separation device 16 to the piping of the purification device 17. Two gas-liquid separators may be provided. If it does in this way, when the cooling effect in the said condenser 12 is inadequate, it will be possible to cool again and the reproduction | regeneration oil P will be more reliably recoverable.

  Further, in this case, when the component of the regenerated oil P to be recovered is to be adjusted, the cooling temperature of the condenser 12 and the second condenser is set to different temperatures, and the cooling temperature of the condenser 12 is further increased, The recycled oil liquefied by the condenser 12 and collected in the liquid storage tank 18 is liquefied by the second condenser, and the component having a higher boiling point than the recycled oil collected in the second liquid storage tank is collected. This makes it possible to produce reclaimed oil according to the purpose of use.

By the way, although air etc. are used as a refrigerant | coolant of the condenser 12, when the air etc. which heat was added in this condenser 12 are used as a hot air for drying in the washing | cleaning and drying process 13, it is preferable from a viewpoint of thermal recycling. .
Further, if a part of the regenerated oil P as a product is used as a part or all of the combustion raw material of the combustion furnace 11b, the consumption of external energy can be saved, and the energy saving can be achieved in the whole apparatus.

When the regenerated oil P is produced by the above-described method, a residue is accumulated in the pyrolysis vessel 11a. For this reason, it is necessary to cool the pyrolysis kettle 11a at a timing at which the thermal decomposition efficiency of the waste plastic M in the pyrolysis kettle 11a is not lowered so much that the internal residue is taken out together with the molten waste plastic M. In this case, natural cooling may be performed. However, when the pyrolysis pot 11a is large, cooling takes time, which is not efficient. In such a case, as shown in FIG. 3, it is preferable to connect a cooling unit for cooling the internal gas of the pyrolysis vessel 11a to the pyrolysis vessel 11a.
The cooling unit includes a condenser 22 for cooling the internal gas of the pyrolysis kettle 11a, a lead-out line for sending the internal gas of the pyrolysis kettle 11a to the condenser 22, and the internal gas cooled by the condenser 22 It has an introduction line that returns to the pyrolysis kettle 11a.
When operating this cooling unit, first, the combustion furnace 11b is temporarily stopped, and the heating of the pyrolysis pot 11a is temporarily stopped. Next, the internal gas of the pyrolysis vessel 11a is sent to the condenser 22 via the lead-out line. And after cooling internal gas with the condenser 22, this cooled internal gas is returned to the thermal decomposition pot 11a via the said introduction line.
This operation is preferable because the inside of the pyrolysis pot 11a can be forcibly cooled and the cooling time can be shortened. At this time, it is preferable to add a small amount of nitrogen gas (N ₂ ) to the positive pressure through a pipe from the pyrolysis kettle 11 a to the condenser 22. If it does in that way, the subsequent piping will become a negative pressure by cooling with the condenser 22, and it can prevent that air, especially oxygen enter. This is because when oxygen intrudes, the temperature is high and oxidation may occur.
In addition, since the residue in the pyrolysis pot 11a is a carbide | carbonized_material, it is better to cool as much as possible.

The following method can be given as a specific example of the method for periodically taking out the residue from the pyrolysis kettle 11a.
During the operation of the waste plastic oil converting apparatus according to the present invention, when taking out the residue in the pyrolysis vessel 11a, first, supply of molten waste plastic to the pyrolysis vessel 11a is first stopped. At this time, the decomposition of the molten waste plastic in the thermal decomposition pot 11a continues. However, since the amount of cracked gas sent to the reflux tower 15 decreases, the supply amount of the regenerated oil P supplied from the condenser 21 to the upper part of the reflux tower 15 is reduced accordingly.

Next, when the temperature of the pyrolysis kettle 11a exceeds 430 ° C., the heating of the pyrolysis kettle 11a is stopped. Then, forced cooling of the pyrolysis pot 11a is performed by the method described above. Prior to this, when the temperature of the pyrolysis vessel 11a exceeds 410 ° C., the supply amount of the regenerated oil P supplied from the condenser 21 to the upper part of the reflux tower 15 and the piping from the reflux tower 15 to the condenser 12 is stopped. Let Further, the outlet of the liquid storage tank 18 is closed. When two liquid storage tanks (the liquid storage tank 18 and the second liquid storage tank) are used, the line between them and the outlet of the second liquid storage tank are closed.
Next, when the pyrolysis kettle 11a is sufficiently cooled (about 50 ° C. to 70 ° C.), an internal residue is taken out from the bottom of the pyrolysis kettle 11a.

  By the way, there is cracked gas sent from the pyrolysis kettle 11a to the reflux tower 15 after the heating of the pyrolysis kettle 11a is stopped until this operation is completed. In this case, since the supply of the regenerated oil P from the condenser 21 to the upper part of the reflux tower 15 is stopped, the high-boiling components contained in the cracked gas are not sufficiently separated and can reach the liquid storage tank 18. There is.

  Next, after taking out the residue, the open portion of the pyrolysis vessel 11a is closed, and the supply of waste plastic and the heating of the pyrolysis vessel 11a are resumed. At this time, the entire amount of the regenerated oil P in the liquid storage tank 18 is preferably returned to the upper part of the reflux tower 15 via the condenser 21. Thereby, the high-boiling component contained in the regenerated oil P in the liquid storage tank 18 can be subjected to reflux again. At this time, the outlet of the liquid storage tank 18 is kept closed. If two liquid storage tanks are used (the liquid storage tank 18 and the second liquid storage tank), the line between them and the outlet of the second liquid storage tank are kept closed, and the liquid storage tank After the entire amount of the regenerated oil P in 18 is discharged, the regenerated oil P in the second liquid storage tank is transferred to the liquid storage tank 18. If there is a liquid in the liquid storage tank 18, the regenerated oil P can be immediately supplied to the reflux tower 15 and the like.

  When the cracked gas starts to flow from the thermal decomposition tank 11a to the reflux tower 15, when the outlet of the liquid storage tank 18 (two liquid storage tanks (the liquid storage tank 18 and the second liquid storage tank) are used, The line between them and the outlet of the second liquid storage tank) are opened, and in a state where the regenerated oil P has accumulated to some extent in the liquid storage tank 18, the condenser 21 is connected to the upper part of the reflux tower 15 and from the reflux tower 15 to the condenser 12. The supply of the regenerated oil P supplied to the pipe is resumed.

  When the waste plastic oil treatment apparatus according to the present invention is used, recycled oil can be obtained from waste plastic that has been conventionally discarded and burned, and a new energy source can be obtained.

Hereinafter, the present invention will be described more specifically with reference to examples.
[Example 1]
Using the flow described in FIG. 1 and FIG.
First, waste plastics (polyethylene: 75% by weight, polypropylene: 5% by weight, polystyrene: 5% by weight) were washed with a cleaning device (manufactured by Kanemiya Co., Ltd .: Bun-Sen) to remove dirt. Next, warm air of 70 ° C. to 80 ° C. was obtained using the exhaust heat of the pyrolysis pot 11a, and this was blown and dried.
Next, it was charged at about 400 kg / h into the inlet on the inlet side of the single screw extruder (manufactured by Ishinaka Iron Works Co., Ltd.). In this single screw extruder, the temperature condition is set so that the outlet side is about 260 ° C.
The molten waste plastic melted by this single screw extruder is continuously supplied to the pyrolysis vessel 11a. The pyrolysis furnace 11a of the pyrolysis furnace 11 has an inner diameter of 2 m and a height of 2 m, a central part is cylindrical, an upper part and a lower part are elliptical, and a combustion furnace 11b is arranged at the lower part. 11a is heated. The pyrolysis pot 11a is adjusted so that the internal temperature becomes 380 ° C to 440 ° C.

The molten waste plastic is pyrolyzed in the pyrolysis kettle 11a to become cracked gas and moves to the reflux tower 15 above the pyrolysis kettle 11a. This cooling tower has an inner diameter of 310.5 mm and a height of 2150.2 mm, and is filled with a regular packing (manufactured by Matsui Machine Co., Ltd .: MC pack).
Inside the reflux tower 15, a part of the cracked gas is liquefied at the upper part to generate a reflux state. This is because the cracked gas is allowed to cool as it goes to the upper part of the reflux tower 15 and the temperature is lowered. As will be described later, a part of the regenerated oil stored in the liquid storage tank 18 is cooled to return to the reflux tower. This is because it is supplied to the upper part of 15 and brought into direct contact with the cracked gas.
The liquefied liquid of the cracked gas liquefied in the reflux tower 15 returns to the thermal decomposition tank 11a and is again provided for thermal decomposition. On the other hand, the cracked gas that has not been liquefied is sent to the condenser 12 from above the reflux tower 15. A part of the regenerated oil in the liquid storage tank 18 that has been partially cooled is supplied to the pipe from the reflux tower 15 to the condenser 12 to directly cool the cracked gas.

Next, the decomposition gas is cooled in the condenser 12. Air is used as the refrigerant at this time. Since the air used as the refrigerant reaches about 80 ° C. after passing through the condenser 12, it is reused as part of the hot air of the hot air dryer described above.
The cracked gas cooled by the condenser 12 is introduced into the gas-liquid separation device 16 together with the liquefied liquefied liquid and the regenerated oil directly introduced for cooling, and the gas-liquid is separated, and the gas component is purified by a purification device (Seiko Chemical Industries). Co., Ltd .: TRS-F20) 17 is sent, the ammonia component is removed, and the remainder is discharged to the outside as exhaust gas.
On the other hand, the liquid component is sent to the liquid storage tank 18 and stored as recycled oil. This stored reclaimed oil is used as a product. A part of the regenerated oil is cooled by the condenser 21 and supplied as a cooling liquid to the reflux tower 15 and the piping from the reflux tower 15 to the condenser 12 as described above.
This regenerated oil is cooled by the condenser 21 within a range of 50 ° C. to 120 ° C. and used. The amount of regenerated oil supplied to the reflux tower 15 is 130 kg / h, and the amount of regenerated oil supplied to the pipe from the reflux tower 15 to the condenser 12 is 3.07 kg / h. These supplies are supplied whenever necessary using regenerated oil that is always stored in the storage tank 18.

  Recycled oil is produced by these flows, and the first fraction of the regenerated oil (100 liters first accumulated in the liquid storage tank 18. Also, the recycle oil reflux tower 15 and the piping from the reflux tower 15 to the condenser 12. The composition in the distillate was examined for the middle distillate (the distillate in the range of 400 liters to 800 liters). The results are shown in Table 1.

  In addition, since the composition of kerosene was investigated as the reference example 1, it shows together.

[Comparative Examples 1-4]
In the first embodiment, the internal temperature of the pyrolysis vessel 11a is changed, and the regenerated oil in the liquid storage tank 18 is supplied to the reflux tower 15 and the piping from the reflux tower 15 to the condenser 12 without using the reflux tower 15. A regenerated oil was produced in the same manner as in Example 1 except that the oil was removed.
About each middle distillate when the internal temperature of the pyrolysis pot 11a is changed to 380 ° C. (Comparative Example 1), 390 ° C. (Comparative Example 2), 400 ° C. (Comparative Example 3), 410 ° C. (Comparative Example 4) The composition was examined. The results are shown in Table 1.

In Table 1, “naphtha” means a component having 5 to 9 carbon atoms, “lamp / light oil” means a component having 10 to 17 carbon atoms, and “heavy oil” means 18 to 18 carbon atoms. 21 refers to a component having a carbon number of 22 or more.
In Table 1, “pour point” refers to the temperature at which the fraction exhibits fluidity.

(result)
From the comparison between the middle distillate of Example 1 and Comparative Example 4 (middle distillate), in Example 1 using the reflux tower, the wax content was 2.7% by weight, and the wax content was mixed into the recycled oil. It became clear that it could be suppressed.
Further, as apparent from the pour point of each comparative example, when the reflux tower is not used, when the inside of the pyrolysis kettle reaches 390 ° C. or higher, the distillation of the wax increases, and the pour point becomes 8.0 ° C. or higher. It became clear that it became easy to solidify. On the other hand, in Example 1, despite the fact that the inside of the pyrolysis kettle is 410 ° C., the wax content is small and the pour point is less than −10 ° C. It was found that adhesion was difficult to occur.

DESCRIPTION OF SYMBOLS 11 Pyrolysis furnace 11a Pyrolysis pot 11b Combustion furnace 12 Condenser 13 Washing and drying process 14 Liquefaction process 15 Reflux tower 16 Gas-liquid separation apparatus 17 Purification apparatus 18 Liquid storage tank 21 Condenser 22 Condenser M Waste plastic P Recycled oil

Claims (6)

It is a waste plastic oil processing apparatus having a condenser that thermally decomposes waste plastic to generate cracked gas, and a condenser that cools and liquefies the cracked gas obtained in the thermal cracking pot to obtain recycled oil,
A waste plastic oil processing apparatus for providing a reflux tower for refluxing the cracked gas obtained in the pyrolysis kettle above the pyrolysis kettle, and returning high boiling components in the cracked gas to the pyrolysis kettle.   The waste plastic oil treatment apparatus according to claim 1, wherein a part of the regenerated oil obtained in the condenser is cooled and returned to at least one of the reflux tower and a pipe between the reflux tower and the condenser. The pyrolysis kettle is connected to a cooling unit for cooling the internal gas of the pyrolysis kettle,
The cooling unit includes a condenser for cooling the internal gas of the pyrolysis kettle, a lead-out line for sending the internal gas of the pyrolysis kettle to the condenser, and the internal gas cooled by the condenser. The waste plastic oil converting apparatus according to claim 1 or 2, further comprising an introduction line for returning to the pyrolysis kettle. Supply molten plastic to the pyrolysis kettle,
The molten waste plastic is pyrolyzed with this pyrolysis kettle,
The cracked gas obtained by the pyrolysis is sent to a reflux tower provided above the pyrolysis kettle to be refluxed,
A method for producing recycled oil from waste plastic, wherein the cracked gas from the reflux tower is cooled by a condenser to obtain recycled oil.   A part of the regenerated oil obtained in the condenser is cooled and returned to at least one of the reflux tower and the pipe between the reflux tower and the condenser, and the cracked gas in the reflux tower, or in the pipe A method for producing reclaimed oil from waste plastics according to claim 3, which is brought into direct contact with the cracked gas. When removing the reclaimed oil, in order to remove the residue accumulated in the pyrolysis kettle,
Temporarily stops heating the pyrolysis kettle,
Send the internal gas of the pyrolysis kettle to the condenser via the outlet line,
Cooling the internal gas with the condenser;
The method for producing recycled oil from waste plastic according to claim 4 or 5, wherein the inside of the pyrolysis kettle is cooled by returning the cooled internal gas to the pyrolysis kettle via an introduction line.

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