JP2001040137A - Process for pyrolytic decomposition of chlorine- containing resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a pyrolytic decomposition rate without dilution or contamination of a hydrogen chloride gas produced through pyrolytic decomposition by feeding hydrogen chloride as a carrier gas into a pyrolytic decomposition furnace. SOLUTION: The pyrolytic decomposition is carried out by feeding a chlorine- containing resin from an inlet, for example, of a rotary kiln-type indirect heating furnace, and heating indirectly from the inside or outside of the kiln to set the inside at an appropriate temperature. The chlorine-containing resin is de- chlorinated during the course of movement through the kiln and is taken out after separation into a carbonized product and a hydrogen chloride-containing exhaust gas. At this time, hydrogen chloride is fed into the furnace as a carrier gas, so that an easy-to-melt substance bled out on the surface of the chlorine- containing resin is forced to be volatilized and can thus be removed. Eventually, the pyrolytic decomposition rate the resin can be remarkably improved. If the feed of the carrier gas is increased, the resultant hydrogen chloride gas is not contaminated, thereby permitting a high de-chlorination rate of the chlorine-containing resin to be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel pyrolysis method for chlorine-containing resins. More specifically, it is a method for pyrolyzing a chlorine-containing resin that can increase the rate of thermal decomposition of the chlorine-containing resin when pyrolyzing the chlorine-containing resin using a rotary kiln-type pyrolysis furnace.

[0002]

2. Description of the Related Art In recent years, a large amount of waste containing chlorine-containing resin such as polyvinyl chloride has been discharged, and the amount of waste has been increasing steadily. Most of these wastes are simply incinerated or directly landfilled.

However, when these chlorine-containing resins are simply incinerated, harmful substances such as hydrogen chloride generated at the time of incineration may be directly released to the atmosphere. On the other hand, simple landfills have been problematic due to the difficulty in securing land and resource recycling.

In recent years, studies have been made to thermally decompose these chlorine-containing resins and recover and reuse the effective components therein as carbides.

[0005] In the above pyrolysis, a rotary kiln (hereinafter simply referred to as kiln) type pyrolysis furnace is typical as a pyrolysis furnace for treating a chlorine-containing resin. In the pyrolysis furnace, the chlorine-containing resin is heated under an inert atmosphere and decomposed into hydrogen chloride gas and solid carbide. And the decomposed hydrogen chloride gas is taken out from the bleed port of the pyrolysis furnace,
On the other hand, the carbide is taken out from the outlet.

[0006]

However, when the thermal decomposition of a chlorine-containing resin is carried out, the rate of thermal decomposition in a cracking furnace is unexpectedly low, especially when the resin contains an organic substance such as a plasticizer. There is a problem that it becomes noticeable.

In general, in order to improve the rate of thermal decomposition in the above decomposition reaction, it is conceivable to remove hydrogen chloride gas, a product in the reaction equilibrium, from the surface of the chlorine-containing resin.

[0008] For example, a mode in which a carrier gas comprising an inert gas such as nitrogen is supplied into a decomposition furnace, and hydrogen chloride gas generated by thermal decomposition is removed from the resin surface is considered.

However, when the above-mentioned inert gas is used as a carrier gas, it is necessary to increase the amount of nitrogen gas to be supplied in order to sufficiently increase the rate of thermal decomposition. It is remarkably diluted by gas, and when the hydrogen chloride gas is purified in a gaseous state and used as a hydrogen chloride source in another step, for example, a step such as oxychlorination, the nitrogen gas is purified and removed. Have difficulty.

[0010] Further, even if it can be produced to a certain extent, there is a problem that the effect of nitrogen contained in the hydrogen chloride gas causes a reduction in product yield and a reduction in reaction rate in the above process.

Accordingly, an object of the present invention is to provide a method for thermally decomposing a chlorine-containing resin capable of improving the rate of thermal decomposition without diluting or contaminating the hydrogen chloride gas generated by the thermal decomposition of the chlorine-containing resin. Is to do.

[0012]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, the main factor inhibiting the thermal decomposition reaction of the chlorine-containing resin is as follows. As easily as the hydrogen chloride gas generated and staying on the surface, an easily melted substance existing as an additive or as a polymer component in the resin may cover the surface by the heat of thermal decomposition. It was confirmed that this was an extremely large factor.

As a result of further study, the use of hydrogen chloride gas as the carrier gas has the effect of removing the above-mentioned easily melted material present on the resin surface,
It has been found that the rate of thermal decomposition of the chlorine-containing resin can be improved, and as a result, a surprising effect that contamination and dilution of the obtained hydrogen chloride gas do not occur can be obtained, and the present invention has been completed.

That is, the present invention provides a method for pyrolyzing a chlorine-containing resin, wherein hydrogen chloride is supplied as a carrier gas into the pyrolysis furnace when the chlorine-containing resin is pyrolyzed in the pyrolysis furnace. is there.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a chlorine-containing resin is
Known resins which can be dehydrochlorinated by thermal decomposition are used without particular limitation. For example, vinyl chloride resin, vinylidene chloride resin, chlorinated polyolefin and the like can be mentioned. Among them, a vinyl chloride resin is typical. The chlorine-containing resin in which the present invention is particularly effective includes phthalic acid esters, dibutyl phthalate (DBP), di-2-ethylhexyl phthalate (DOP), and other easily melted materials.

The shape and size of the chlorine-containing resin supplied to the pyrolysis furnace are not particularly limited, but those which have been pulverized or crushed to an appropriate size should be used because of the ease of the pyrolysis reaction. Is preferred. Further, in order to prevent the chlorine-containing resin from adhering to the inner wall of the pyrolysis furnace during the pyrolysis process, it is preferable to previously mix with the powdery anti-adhesion agent or to simultaneously supply both to the pyrolysis furnace. . As the anti-adhesion agent, a material that does not adversely affect the use of the carbide is used without any limitation. For example, when using a carbide simply as a fuel, coke powder, a crushed material of the carbide obtained by pyrolysis, etc., and when using as a fuel for cement, in addition to the above examples, cement clinker powder, etc. Is preferably used. The proportion of the adhesion inhibitor is preferably 5 to 100 parts by weight based on 100 parts by weight of the chlorine-containing resin.

In the present invention, when the chlorine-containing resin is supplied to the pyrolysis furnace, in order to reduce the entrained air as much as possible, after degassing in a decompression chamber, the entrained gas is converted into hydrogen chloride. It is preferable to replace the gas and supply it to the pyrolysis furnace.

In the present invention, as long as the pyrolysis furnace for pyrolyzing the chlorine-containing resin has a carrier gas supply port and an extraction port for hydrogen chloride gas generated by pyrolysis, other structures can be used. The structure of a known pyrolysis furnace is adopted without any particular limitation. Among them, a kiln type pyrolysis furnace is preferably used.

For example, a kiln-type pyrolysis furnace suitably used in the present invention has a carrier gas supply port and an extraction port for hydrogen chloride gas generated by pyrolysis with the kiln interposed therebetween. In addition, one of the kilns has a raw material supply chamber having a raw material supply port for supplying a chlorine-containing resin as a raw material and a supply device such as a screw feeder, and a carbide outlet for taking out carbide generated in the other. Are connected to each other. The carrier gas supply port and the hydrogen chloride gas extraction port are appropriately provided in the raw material supply chamber or the carbide removal chamber.

Further, the kiln is installed such that the raw material supply port side is held higher than the carbide outlet port side, and the raw material supplied from the supply port moves to the outlet port while being thermally decomposed. Further, a heater for heating is provided outside the kiln.

In the pyrolysis furnace, hydrogen chloride gas generated by the pyrolysis leaks to the outside from a portion other than the bleed port.
In order to prevent environmental pollution, it is preferable to employ a structure for sealing the hydrogen chloride gas, including a known structure.

In the present invention, known conditions for the thermal decomposition of the chlorine-containing resin are employed without any particular limitation. For example,
Taking the rotary kiln type indirect heating furnace as an example, a chlorine-containing resin is supplied from an inlet, and heating is performed indirectly from the inside or outside of the kiln.
It is generally carried out by adjusting the temperature to 00 to 370 ° C. The chlorine-containing resin is dechlorinated while moving in the kiln, is separated into a solid made of dechlorinated chlorine-containing resin (hereinafter also referred to as carbide) and an exhaust gas containing hydrogen chloride, and each is taken out from an outlet. It is.

The most important feature of the present invention is that hydrogen chloride gas is supplied as a carrier gas into the pyrolysis furnace.
That is, by supplying the hydrogen chloride gas, in the pyrolysis furnace, the easily melted substance bleed out to the surface of the chlorine-containing resin can be forcibly volatilized and removed, and the thermal decomposition rate of the resin can be reduced. It can be greatly improved. As described above, it is completely unpredictable that the use of hydrogen chloride gas, which is a product in the reaction equilibrium of the thermal decomposition, as the carrier gas exhibits the effect of improving the reaction rate.

Since the carrier gas is hydrogen chloride gas, even if the supply amount is increased, the generated hydrogen chloride gas is not contaminated. Therefore, the supply amount of the carrier gas is increased to increase the dechlorination rate of the chlorine-containing resin. It is possible to achieve

Further, by supplying hydrogen chloride gas as a carrier gas into the kiln, the temperature distribution in the kiln can be made uniform.

When the temperature of the hydrogen chloride gas supplied as the carrier gas is low, the temperature inside the furnace is lowered by the supply.
It is preferable to supply by heating to 00 ° C. In particular, supplying hydrogen chloride gas heated above the set temperature in the kiln is very useful because it can be used as a heating source in the kiln.

Although the supply amount of the hydrogen chloride gas supplied as the carrier gas is not particularly limited, the linear velocity of the gas flow in the kiln is 0.01 m / s or more, preferably 0.03
m / s or more, more preferably 0.03 to 0.1 m / s. When the supply amount of the hydrogen chloride gas is small and the linear velocity in the kiln is lower than 0.01 m / s, the effect of removing the easily meltable substance may be insufficient, and the thermal decomposition rate tends to decrease.

Further, when a rotary kiln type pyrolysis furnace is used, the carrier gas may flow in any direction with respect to the flow of the chlorine-containing resin in the pyrolysis furnace. It is preferable to flow so as to flow.

According to the method of the present invention, the hydrogen chloride gas taken out of the pyrolysis furnace contains water and other undecomposed organic components supplied along with the chlorine-containing resin.
It is a hot gas of 300 to 370 ° C.

The gas taken out of the pyrolysis furnace is obtained as hydrogen chloride gas in which the amount of hydrogen chloride gas supplied as a carrier gas is increased, and by applying a dry refining method, extremely high-purity hydrogen chloride gas is obtained. It can be obtained efficiently. As a preferred dry purification method, a method of contacting a crude hydrogen chloride gas with an organic solvent inert to hydrogen chloride is recommended. It is preferable to maintain the temperature of the hydrogen chloride gas at 250 ° C. or higher until immediately before the contact with the organic solvent in order to efficiently and stably perform the purification.

Examples of suitable organic solvents used for the above contact include chlorine-based organic solvents such as ethylene dichloride (EDC), dichloromethane, chlorobenzene, and the like.
-Non-chlorine organic solvents such as hexane, and heavy ends obtained from the above-mentioned organic solvent production process. Among them, a chlorine-based organic solvent is preferably used because it is less contaminated with hydrogen chloride and has a low solubility of hydrogen chloride. In particular, when the obtained hydrogen chloride is used for the production of EDC, a part of the produced EDC can be used as the organic solvent, and the impure EDC after contact with the exhaust gas is used as the EDC. The present invention can be purified and reused in a manufacturing facility, and the present invention can be carried out extremely economically.

It is preferable that the organic solvent is cooled upon contact with hydrogen chloride gas. The temperature of the organic solvent is not higher than the boiling point of the organic solvent, preferably 20
The temperature is lower than ℃.

Further, the method of contacting the hydrogen chloride gas with the organic solvent is not particularly limited, and a known gas-liquid contact method is employed. For example, (a) a method of forcibly forming a gas-liquid mixed flow of hydrogen chloride gas and an organic solvent using an ejector, (b) a method of spraying an organic solvent on a hydrogen chloride gas flow, and (c) a method of spraying an organic solvent And a method of blowing hydrogen chloride gas directly into the liquid phase. In the above method (b), facing contact is preferable, and it is recommended that an organic solvent is sprayed from above on the upward flow of the crude hydrogen chloride gas to make facing contact. Further, in the method (c), a mode using a packed tower, a bubble bell tower, or the like is preferable since the contact can be performed effectively.

Among these contact methods, the most effective and simple one is the method using the ejector (a).

For recovering the hydrogen chloride gas phase, a mode in which the organic solvent can be efficiently removed is suitably adopted. For example,
In the above method (a), the gas phase is obtained as a gas-liquid mixed phase flow after the contact, so that the gas phase is preferably recovered using a known gas-liquid separation device. In the methods (b) and (c), since the gas phase is generally obtained from the top of the apparatus, a gas-liquid separation apparatus is not separately required. It is preferable that the organic solvent be brought into contact with the cooled organic solvent near the outlet of the apparatus.

Preferably, the gas phase is recovered as it is, and a part thereof is used as the carrier gas of the present invention.
The hydrogen chloride gas may be used as a hydrogen chloride source in another step.

In the above applications, it is preferable to remove a trace amount of water. For the removal of the water, a known method is employed without particular limitation. For example, the gas phase is-
A cryogenic separation method of cooling to 20 ° C. or less, a method of contacting with a dehydrating agent such as concentrated sulfuric acid, calcium chloride, zeolite, or acid-resistant molecular sieve can be suitably performed.

[0038]

As will be understood from the above description, according to the method of the present invention, when the chlorine-containing resin is thermally decomposed by using a pyrolysis furnace such as a rotary kiln, the removal of easily melted material and the inside of the kiln are performed. The thermal decomposition rate can be improved by making the temperature uniform, and the hydrogen chloride gas generated by the thermal decomposition of the chlorine-containing resin can be recovered without dilution or contamination. Value is extremely large.

[0039]

Example 1 Using a rotary kiln type pyrolysis furnace, vinyl chloride resin pellets were pyrolyzed under the following conditions.

That is, a raw material obtained by mixing 40 parts by weight of oil coke powder with respect to 100 parts by weight of a vinyl chloride resin is supplied to a rotary kiln by a screw feeder through a two-stage damper, and the average temperature in the kiln is set to 350 parts.
C. and moved inside the furnace.

On the other hand, from the carrier gas supply port provided so that the flow of the carrier gas is countercurrent to the flow direction of the chlorine-containing resin, the linear velocity in the kiln becomes 0.05 m / s. Hydrogen chloride gas (purity 9) heated to 350 ° C
9.9%).

In order to confirm the thermal decomposition rate of the thermal decomposition method, an experiment was conducted by gradually increasing the inclination of the kiln and changing the residence time in the kiln. As a result, the residence time in the kiln was reduced to 30 minutes. As a result, the dechlorination rate of the chlorine-containing resin was 9
9%.

On the other hand, the gas taken out from the bleed port is 3
While maintaining the temperature at 00 ° C or higher, EDC
After contact with, water in the obtained gas phase was removed by cryogenic separation to purify.

The purity of the obtained hydrogen chloride gas is 99.5%.
Met.

Comparative Example 1 A vinyl chloride resin was thermally decomposed in the same manner as in Example 1 except that no carrier gas was supplied.

As a result, the dechlorination rate of the chlorine-containing resin was 85%.
Met.

Comparative Example 2 The procedure of Example 1 was repeated, except that the carrier gas was changed to nitrogen. In this case, in order to maintain the purity of the obtained hydrogen chloride gas at 90%, the linear velocity had to be 0.01 m / s, and as a result, the dechlorination rate of the chlorine-containing resin was 90%. .

Claims (2)

[Claims] 1. A method for pyrolyzing a chlorine-containing resin, wherein hydrogen chloride is supplied as a carrier gas into the pyrolysis furnace when the chlorine-containing resin is thermally decomposed in the pyrolysis furnace. 2. The method according to claim 1, wherein a part of the hydrogen chloride gas produced by the thermal decomposition of the chlorine-containing resin and taken out of the thermal decomposition furnace is used as the hydrogen chloride gas.