JPS5822067B2 - Method for thermal decomposition of polyolefin plastics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for thermally decomposing polyolefin plastics to obtain hydrocarbons useful as industrial raw materials or fuels.

More specifically, the present invention relates to a method for selectively producing liquid hydrocarbons having a low molecular weight and a narrow molecular weight distribution range by thermally decomposing polyolefin plastics.

Polyolefin plastics account for about 30% of the total plastic production, and are currently used in large quantities in a wide range of applications from daily necessities to industrial products.

By the way, although some of this used waste plastic is incinerated along with municipal garbage, or is used for landfill or building materials after undergoing appropriate treatment, the majority of it is simply disposed of. has been done.

However, this type of plastic is hardly decomposed by microorganisms, so even if it is left in its current form for a long period of time, it will not disappear naturally due to decay etc., and the amount accumulated will gradually increase. has become an important social issue.

Therefore, if such waste plastics could be recycled as industrial raw materials or fuel by some means, it would not only be possible to reduce the amount of waste plastics accumulated (it would also lead to resource and energy savings, It will have important significance in our country.

Until now, methods are known for pyrolyzing waste plastics to recover useful hydrocarbons.

However, when polyolefin plastics are thermally decomposed, the products recovered from the fraction are low-grade products with a wide molecular weight distribution from low-boiling point components to high-boiling point components, and have a grease-like appearance at room temperature. The range is inevitably limited.

Therefore, there has been a demand in this technical field for a method for obtaining decomposition products with a low molecular weight and a narrow molecular weight distribution range by simple means.

As a result of various studies to develop a treatment method for the effective use of polyolefin plastic waste, the present inventor has determined the molecular weight and distribution range of the pyrolysis products by selecting the pyrolysis temperature and the formation of the pyrolysis products. It has been discovered that objects can be conditioned by passing them through a filling zone made of a specific filling material and controlled at a specific temperature, and the present invention has been developed based on this knowledge.

That is, according to the present invention, when producing hydrocarbon oil by thermally decomposing a polyolefin plastic and passing the vaporized product through a heated packed zone, the thermal decomposition temperature is set at 430 to 470°C. In addition, by forming the filling zone with glass beads with a particle size of 6.5 mm or less, and keeping this at a temperature of 250°C or less, it has a low molecular weight, a narrow molecular weight distribution range, and a liquid state at room temperature. grade hydrocarbon oil can be obtained.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

The figure is a schematic cross-sectional view showing one example of an apparatus suitable for carrying out the method of the present invention, in which polyolefin plastic waste is supplied to a pyrolysis reactor 1 from a raw material supply port 4, and there 10 to be heated to 430-470°C and thermally decomposed.

The vaporous material produced by this process rises and is sent to a packed column 2 connected to the top of the pyrolysis reactor 1.

This packed tower 2 is filled with glass beads having a particle size of 6.5 mm, and the internal temperature is maintained at 250° C. or lower by a heating wire 11.

Said vaporous material is further thermally decomposed while passing through the packed column 2 and passes through the outlet 3 to the receiver 6 .

At this time, if desired, an inert gas can be blown into the decomposition reactor 1 through the gas introduction pipe 5 to promote the generation of vaporous substances.

Most of the products not collected in the receiver 6 are collected in the dry ice trap 7, and gaseous substances that do not condense there are collected in the gas trap 8.

The internal temperatures of the decomposition reactor 1 and the packed tower 2 are measured by a thermocouple 9, and controlled based on the results.

In the method of the present invention, it is necessary to thermally decompose the olefinic plastic at a temperature within the range of 430 to 470°C.

If carried out outside this temperature range, the yield of products with a narrow molecular weight distribution range will be reduced.

Furthermore, it is necessary to use glass beads with a particle size of 6.5 mm or less as a filler and keep the temperature at 250° C. or less as a filling zone.

So. Thus, the smaller the particle size of the glass beads, the narrower the molecular weight distribution range.

That is, when no filler is used at all, a product with a wide molecular weight distribution range of carbon number distribution C5 to C40 is obtained, but glass vinyl with a particle size of 6.151 m.

- When filled with glass beads, a product with a molecular weight distribution range of carbon number distribution C5 to C24 is obtained, and when filled with glass beads with a particle size of 2.39 mrn, a product with a carbon number distribution of 05 to C2□
A product with a molecular weight distribution range of is obtained.

In this way, by reducing the particle size of the glass beads and increasing the contact area of the vapor substance, the effect of contact with the filler material can be improved.

In the present invention, the vaporized material pyrolyzed and vaporized in the cracking reaction zone has a certain composition and temperature and rises to contact the glass beads in the filling zone, the temperature of which is higher than the temperature of the vaporous material. As it remains low, some of it condenses and returns to the decomposition reaction zone, where it is re-decomposed and rises again to the packed zone.

On the other hand, the vapor of low-boiling components that has entered the filled zone passes between the glass beads, is re-decomposed at the temperature within the packed zone, and is distilled and recovered as a vapor substance rich in low-boiling components.

In this way, products with a narrow molecular weight distribution range are formed through sequential fractionation by reflux between the cracking reaction zone and the packed zone.

And the most preferable carbon number range C5 as a hydrocarbon oil
Regarding the yield of ~C20, when the temperature in the next filling zone is about 250 ° C., it is found that in the case of no filler, 85 to 94.2% by weight was filled with glass beads with a particle size of 6.1 to 5 mm. 95.7 to 987% by weight, 96.0 when filled with glass beads with a particle size of 2.39 mm
A result of ˜99.95% by weight is obtained.

Also, when comparing the average molecular weight (Mw), it is in the range of 190 to 210 in the case without filler, while
In the case of glass beads with a particle size of 6.151 m, it is 172 to 18
7, and in the case of particle size 2.39 mm, it is 150 to 1
72, each having a low molecular weight and a narrow molecular weight distribution range.

In this way, the lower the temperature of the filled zone and the smaller the particle size of the filler, the lower the average molecular weight of the distilled vapor product, the narrower the molecular weight distribution range, and the more the molecular weight distribution state is shifted toward the low molecular side. Since it is liquid at room temperature, it is suitable as an industrial raw material or fuel.

Therefore, in the present invention, it is necessary that the particle size of the filler in the filling zone is 6.5 mm or less, and that the temperature of this zone is lower than the decomposition reaction temperature, that is, 250° C. or lower.

Polyolefin plastics used as feedstock in the method of the present invention include polyethylene, polypropylene,
In addition to olefin homopolymers such as polybutylene,
Copolymers of ethylene, propylene, butylene and other olefins with copolymerizable monomers, crosslinked polyethylene, and the like are also included.

The time required for thermal decomposition of these plastics in the method of the present invention varies slightly depending on the type of plastic, but is usually in the range of several minutes to several hours.

According to the method of the present invention, useful hydrocarbon oil can be produced using polyolefin plastic waste, which has been discarded without being used in any way, as a main raw material.
It can be said that this is a very meaningful technology in terms of effective use of resources and prevention of pollution.

Next, the present invention will be explained in more detail with reference to Examples.

In the reactor having the same structure as the example drawings, the decomposition reactor 1
The packed tower 2 was made of Pyrex glass with a height of 150 mm and an inner diameter of 31 mm, and filled with glass beads of different particle sizes. was thermally decomposed.

The temperature of the packed tower at this time was 250°C.

Polyethylene is pellet-shaped with a particle size of approximately 37rL7IL, a density of 0.952, and a calorific value of 11000 cal/P.
I used the one from

. The analysis results of the hydrocarbon oil thus obtained are shown in the following table.

[Brief explanation of the drawing]

The figure is a schematic cross-sectional view of an apparatus suitable for carrying out the method of the present invention, and the reference numerals in the figure indicate the following. 1... Pyrolysis reactor, 2... Packed tower, 3... Discharge port, 4... Raw material supply port,
6... Receiver, 10°11... Heating wire.

Claims (1)

[Claims] 1. A method for producing hydrocarbon oil by thermally decomposing a polyolefin plastic and passing the vaporized product through a heated packed zone, wherein the thermal decomposition temperature is 430 to 430°C.
Keeping the temperature within the range of 470℃ and filling zone with particle size 6.5
Formed with glass beads of mm or less, and heated at 250°C
A pyrolysis method characterized by maintaining the temperature at: 2. The method according to claim 1, wherein the polyolefin plastic is polyethylene, polypropylene, polybutylene, or a copolymer of ethylene and propylene.