JPH0748578A - Liquefying method for oil vapor from waste plastic melt - Google Patents

Abstract

PURPOSE:To effectively utilize an oil vapor from a waste plastic melt instead of burning the vapor in vain. CONSTITUTION:A thermal decomposition oil 21 is recovered by melting and thermally decomposing a waste plastic and cooling and condensing the resultant thermal decomposition gas, and a waste plastic melt 25 contg. contaminants and residues 26 is removed. The recovered oil 21 is used for condensing and liquefying an oil vapor rising from the melt 25.

Description

Detailed Description of the Invention

[0001]

This invention relates to a method for liquefying oil vapor from waste plastic melts.

[0002]

As one of the methods for thermally decomposing waste plastics, the waste plastics are melted and pyrolyzed at the same time in a pyrolysis reactor.
A method of recovering light oil by sending a gas generated by thermal decomposition to a catalyst layer to decompose it into a low carbon chain hydrocarbon and then condensing it in a cooling / condensing section is practiced.

By the way, in such a method, the waste plastic used as a raw material is usually industrial waste, which is discharged from a plastic manufacturer, or waste, which is discharged as separated waste. Therefore, the waste plastics as raw materials are mixed with metals such as wires, clips and screws, and foreign substances such as earth and sand and glass. Such foreign matter is released into the melt during melting in the above method, and accumulates in the melt when continuously treated, and melts the pyrolysis reactor that melts and thermally decomposes the plastic. Accumulate in. Further, the polymer chain of the plastic is broken by thermal decomposition to become a low molecular weight hydrocarbon, and inorganic carbon is separated and generated at this time, and this is accumulated as a residue in the melt in the thermal decomposition reactor. These foreign substances and residues cause the thermal decomposition efficiency in the thermal decomposition reactor to decrease.

In order to solve the above problems, therefore, when the amount of foreign matter and residue in the pyrolysis reactor increases and the pyrolysis efficiency decreases, the supply of waste plastic is stopped and the oil content is removed. After completely evaporating (baking), the foreign matter and the residue are solidified, and after the thermal decomposition reactor is cooled to near room temperature, the accumulated foreign matter and the residue are manually removed. After removing the foreign matter and the residue, the temperature is raised again and the operation of the apparatus is restarted.

However, in such a method, the energy loss when the apparatus is cooled to near room temperature for removing the foreign matter and the energy loss required for the temperature rise until the restart after the foreign matter is removed are large, and the thermal decomposition is caused. There is a problem that the fuel consumption required for

Therefore, in order to solve the above problem, there is a method of discharging the molten liquid of waste plastic containing foreign matters and residues from the inside of the thermal decomposition reactor by sucking it with a vacuum pump, for example, without stopping the apparatus. It is considered.

By the way, from the molten liquid of the waste plastic discharged from the pyrolysis reactor, oil vapor capable of recovering the pyrolysis oil is still generated. The amount of this oil vapor reaches about 1/4 of the melt, but the present situation is that the oil vapor is incinerated without being effectively used.

An object of the present invention is to solve the above problems and to provide a method for effectively utilizing oil vapor generated from a melt of waste plastic discharged from the pyrolysis reactor.

[0009]

The method for liquefying oil vapor from a waste plastic melt according to the present invention melts waste plastic to cause thermal decomposition, cools the generated pyrolysis gas, and condenses the pyrolysis oil. In the method for removing the waste plastic melt containing foreign matters and residues, the oil vapor generated from the waste plastic melt is condensed and liquefied by the recovered pyrolysis oil.

[0010]

When the oil vapor generated from the waste plastic melt containing foreign matters and residues is condensed and liquefied by the recovered pyrolysis oil, the oil vapor can be recovered as oil.

[0011]

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

FIG. 1 shows a thermal decomposition apparatus for waste plastic.

In FIG. 1, the waste plastic thermal decomposition apparatus comprises a thermal decomposition reactor (1) for melting and thermally decomposing the raw material plastic, and a foreign matter / residue collection container (2).

The pyrolysis reactor (1) is arranged in a furnace (4) having a heating burner (3). The bottom surface of the pyrolysis reactor (1) has a concave spherical shape that is recessed downward. On the lid (1a) of the pyrolysis reactor (1), supply pipe of the waste plastic as raw material
(5) and the pyrolysis gas discharge pipe (6) are connected.
The supply pipe (5) is connected to the raw material hopper (8) via a valve (7). The discharge pipe (6) is connected to a portion having a catalyst layer (not shown) for further decomposing hydrocarbons. Then, the pyrolysis gas is sent from the pyrolysis reactor (1) through the discharge pipe (6) to the portion having the catalyst layer, where it is further decomposed by the catalyst, and subsequently to the cooling and condensation section. It is sent and condensed, where it is recovered as light pyrolysis oil.

A hollow vertical rotating shaft (9) is arranged so as to penetrate the lid (1a) of the thermal decomposition reactor (1). Vertical rotation axis
A seal device (10) seals between (9) and the periphery of the hole through which the rotary shaft (9) penetrates in the lid (1a). The lower end of the vertical rotation shaft (9) is located near the bottom of the pyrolysis reactor (1). The upper end of the vertical rotation shaft (9) is located above the lid (1a), and the drive motor (13) is connected via the gears (11) (12).
Are linked to. A plurality of stirring blades (14) are fixedly provided at the lower end of the vertical rotation shaft (9). Each stirring blade (14) is curved in a substantially arc shape according to the shape of the bottom surface of the thermal decomposition reactor (1).

Foreign matter and residue suction pipe (15) in the vertical rotation shaft (9)
Are arranged. The upper end of the foreign matter / residue suction pipe (15) extends above the upper end of the vertical rotation shaft (9), and the conduit (16)
It is connected to the foreign matter collection container (2) via. A valve (17) is provided between the foreign matter / residue suction pipe (15) and the conduit (16). The upper end of the vertical rotation axis (9) and foreign matter, residue suction tube (15)
A seal device (18) seals the space between them. Further, the lower end of the foreign matter / residue suction pipe (15) is at substantially the same height as the lower end of the vertical rotation shaft (9).

A condensate liquefaction tank (20) is connected to the foreign matter / residue collection container (2) through a conduit (19). The condensed pyrolyzed oil (21) is contained in the condensing liquefaction tank (20). The end of the conduit (19) on the tank (20) side is immersed in the pyrolysis oil (21), and a large number of holes (19a) are formed in the peripheral wall of the portion immersed in the pyrolysis oil (21). Are formed. A vacuum pump (23) is connected to the condensing liquefaction tank (20) via a pipe (22). A valve (24) is provided in the middle of the pipe (22). Normally, the valve (24) is opened, the valve (17) is closed, and the vacuum pump (23) is operated, so that both conduits (16) (19) and piping (22) are
The inside of the foreign matter and residue collection container (2) is evacuated.

In such a construction, the waste plastic mixed with foreign matter such as industrial waste is opened from the raw material hopper (8) through the supply pipe (5) by opening the valve (7) and the thermal decomposition reactor ( 1) is supplied to. This waste plastic is heated and melted by the combustion heat of the heating burner (3),
It becomes the melt (25). Here, in order to accelerate the reaction, the vertical rotation shaft (9) is rotated by the drive motor (13), and the melt liquid (25) in the thermal decomposition reactor (1) is stirred by the stirring blade (14). The melt (25) depends on the type of plastic, but 14
When maintained at 0 ° C or higher, a thermal decomposition reaction occurs and a thermal decomposition gas is generated. The generated gas is mainly composed of hydrocarbon gas having 1 to 40 carbon atoms, and is sent to the portion having the catalyst layer through the discharge pipe (6), where it is further decomposed into low carbon chain hydrocarbons. After being cooled, it is sent to a cooling / condensing section, where it is cooled and condensed, and recovered as light oil.

If such an operation is continued, foreign substances (26) such as metal and glass mixed in the melt (25) accumulate in the thermal decomposition reactor (1). In addition, the polymer chain of plastic is broken by thermal decomposition to become low molecular weight hydrocarbons,
At this time, inorganic carbon is separated and generated, and this is accumulated as a residue (26) in the thermal decomposition reactor (1). Then, the foreign matter having a large specific gravity such as metal and glass, and the residue (26) are removed from the thermal decomposition reactor (1) by the aggregating effect due to the shape of the stirring blade (14) and the shape of the bottom surface of the thermal decomposition reactor (1). Collects in the center of the bottom. When the amount of accumulated foreign matter and residue (26) increases, the stirring blade (14) is damaged and the melt (25) at the bottom of the thermal decomposition reactor (1)
There is a problem such as charring. To prevent this, open the valves (17) and (24) and operate the vacuum pump (23) to bring the foreign matter and residue collection container (2) into a vacuum state, and the pyrolysis reactor The melt (25) in (1) is foreign matter,
Foreign matter with residue (26), residue suction pipe (15) and conduit (16)
Then, the foreign matter is sucked into the residue collecting container (2). Thus, without stopping the operation of the thermal decomposition device
(26) is removed.

From the waste liquid (25) of the waste plastic sucked into the foreign matter / residue collecting container (2), oil vapor of the same quality as the recovered pyrolysis oil is generated. Although the amount depends on the temperature of the melt, about 1/4 of the melt (melt temperature 300 ° C., vacuum degree 0.5 kgf / cm ² ) evaporates to generate oil vapor. This oil vapor passes through the conduit (19) to the condensation liquefaction tank (2
0), it is blown into the pyrolysis oil (21) from the hole (19a) of the conduit (19). Then, the thermal decomposition oil (21) is directly touched and instantly condensed and liquefied.

By condensing and liquefying the oil vapor,
Although a decrease in the vacuum degree due to a sudden rise in the internal pressure of the condensate liquefaction tank (20) is suppressed, it is possible that volatilization from the pyrolysis oil (21) due to depressurization and condensation of oil vapor on the pyrolysis oil (21) The vacuum pump (23)
It is better to always operate to keep the vacuum level. This volatilized gas having a low temperature goes to the vacuum pump (23), and no special measures against high temperature are required.

In the above, foreign matter and residue collection container (2)
And a condensing liquefaction tank (20) are provided separately,
The foreign matter / residue collection container and the condensing liquefaction tank may be combined. In this case, the pyrolysis oil is mixed with the foreign matter and the waste plastic melt containing the residue, but since this does not solidify even at room temperature, the foreign matter and the residue can be easily separated. Furthermore, since the above mixture is a liquid at room temperature, it can be transported using a normal pump when it is used as a fuel for a heating burner or when it is incinerated. Since the residue component is carbon, it can be burnt out.

[0023]

According to the method for liquefying the oil vapor from the waste plastic melt according to the present invention, the oil vapor generated from the waste plastic melt is recovered as oil and mixed with the pyrolysis oil as described above. Can be made. Therefore,
The oil vapor can be effectively used without wasteful incineration.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a thermal decomposition apparatus for carrying out the method of the present invention.

[Explanation of symbols]

 21 Pyrolysis oil 25 Waste plastic melt 26 Foreign matter, residue

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C10J 3/00 A C10L 1/00 6958-4H

Claims (1)

[Claims] 1. A method of melting waste plastic for thermal decomposition, cooling the generated pyrolysis gas, condensing and collecting it as pyrolysis oil, and removing the waste plastic melt containing foreign matters and residues. A method for liquefying oil vapor from waste plastic melt, comprising condensing and liquefying oil vapor generated from waste plastic melt with pyrolysis oil recovered.