JPH11302444A - Treatment of waste plastic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To block a reaction which generates high-boiling compounds and remove chlorine and/or chlorine compounds by adding a substance which reacts with hydrogen chloride to generate gaseous chlorides at a thermal decomposition treatment temperature to waste plastic containing chlorine-based polymers and thermally decomposing the waste plastic. SOLUTION: Into thermal decomposition equipment such as a screw extruder provided with an inlet and a means of heating waste plastic, a means of mixing and kneading and an outlet of molten plastic, an outfall of chlorine and chlorine compounds and, if desired, an inlet of a chloride-generating substance, waste plastic is introduced, melt-kneaded at 300-400 deg.C and transported and the chloride- generating substance which is a gas or liquid at room temperature is injected and allowed to reside for 20 minutes or longer. Subsequently, chlorine and chlorine compounds generated by the thermal decomposition are discharged and the molten plastic is taken out from the outlet. As the gaseous chloride- generating substance, liquids such as ethanol and methanol and gases such as acetylene and ethylene are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to chlorine and / or chlorine generated during the thermal decomposition treatment of waste plastics containing chlorine-based polymers.
Alternatively, the present invention relates to a method for efficiently removing a chlorine compound to obtain a molten plastic with a low residual chlorine content.

[0002]

2. Description of the Related Art Conventionally, waste plastics contained in general waste and industrial waste have been disposed of by landfill. However, from the viewpoint of environmental protection and effective use of resources, in recent years, low molecular weight and low molecular weight as chemical recycling have been developed. Attention has been focused on the reduction of boiling point to oil, that is, oil recovery and energy recovery by combustion as thermal recycling.

By the way, chemical recycling and thermal recycling process waste plastic at a high temperature. However, if the waste plastic contains a chlorine-based polymer such as polyvinyl chloride or polyvinylidene chloride,
During processing, chlorine is generated, which causes major problems such as corrosion of processing equipment, deterioration of product (oil) quality, reduction of recovery rate of heat and electric energy, and generation of harmful dioxins. Was. For this reason, a method of separating and removing chlorine-based polymers from waste plastics, and when performing chemical recycling and thermal recycling, removing chlorine by thermally decomposing chlorine-based polymers in waste plastics as pretreatment, Dechlorination pretreatment has been performed.

[0004]

However, the conventional method for separating / removing chlorine-based polymers requires a device for separating / removing the chlorine-based polymer, which requires a complicated processing step, and requires physical treatment. Therefore, there is a problem that it is difficult to completely remove the chlorine-based polymer.

As a pretreatment for dechlorination, for example, a method described in JP-A-8-120285 is known. In this method, when a virgin polymer is used, the dechlorination rate is 90% or more. However, when actual waste plastic was used, the dechlorination rate was reduced to about 80%, and sufficient dechlorination treatment could not be performed.

The cause is that it is relatively easy to thermally decompose a chlorine-based polymer in waste plastic in a thermal decomposition treatment apparatus to generate chlorine or a chlorine compound, but the generated chlorine and the like are discharged out of the system. This is because it reacts with a chemical substance such as an inorganic filler contained in the waste plastic before it becomes a high-boiling compound, and it becomes difficult to remove chlorine and the like out of the system.

That is, in a conventionally used thermal decomposition treatment apparatus, a chlorine-based polymer in waste plastic generally causes a reaction such as a dehydrochlorination reaction when heated to 190 to 200 ° C. or more. For example, the dehydrochlorination reaction in the case of polyvinyl chloride is as shown in the following reaction formula.

[0008]

Embedded image-(CH ₂ -CHCl) _n − → − (CH = CH) _n − + nHCl

The temperature of the waste plastic at the outlet of the molten plastic is generally 300 to 350.
° C in many cases. Here, the reason why the thermal decomposition treatment temperature is higher than the decomposition start temperature of the chlorine-based polymer is to increase the thermal decomposition rate of the chlorine-based polymer in the waste plastic and to perform dechlorination in as short a time as possible. Generally, the residence time of the waste plastic in the thermal decomposition treatment apparatus is 3 to 5 minutes or more. For this reason, the generation of chlorine or chlorine compounds in the thermal decomposition treatment device gradually occurs from the input of the waste plastic to the discharge of the molten plastic. Therefore, depending on the location of the chlorine or chlorine compound generated in the apparatus, the generated chlorine or chlorine compound may be an inorganic filler present in the waste plastic before reaching these outlets, for example, calcium carbonate, talc, titanium oxide. , Gypsum, magnesium hydroxide, silica, sand,
Reacts with miscellaneous chemicals such as food residues to form chlorides. The chloride thus formed often has a high boiling point and a high melting point, and it is extremely difficult to vaporize and discharge it from the outlet. Incidentally, when the boiling points of such chlorides are exemplified, calcium chloride is 1600 ° C. or higher, magnesium chloride is 1412 ° C., potassium chloride is 1500 ° C., sodium chloride is 1413 ° C., and titanium trichloride is 440 ° C. or higher.

[0010] Accordingly, an object of the present invention is to provide chlorine and / or chlorine produced by thermal decomposition of waste plastic containing chlorine-based polymer.
Another object of the present invention is to provide a method for efficiently removing chlorine and / or a chlorine compound by preventing a reaction in which a chlorine compound reacts with an inorganic filler or the like to generate a high-boiling compound.

[0011]

Means for Solving the Problems In view of such circumstances, the present inventors have conducted intensive studies and as a result, during the thermal decomposition treatment of chlorine-containing polymer-containing waste plastics, they react with hydrogen chloride at the thermal decomposition treatment temperature. The inventors have found that if a substance that generates gaseous chloride is added, chlorine and / or chlorine compounds generated by thermal decomposition will not be trapped by inorganic fillers and the like and can be efficiently removed from molten plastic, and the present invention has been completed.

That is, the present invention is characterized in that a substance which reacts with hydrogen chloride and generates a gaseous chloride at a pyrolysis temperature is added to waste plastic containing a chlorine-based polymer, followed by pyrolysis. A method for treating waste plastic is provided.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The substance used in the present invention which reacts with hydrogen chloride and generates gaseous chloride at a thermal decomposition treatment temperature (hereinafter referred to as "gaseous chloride generating substance") is not particularly limited. Substances that are liquid or gas at room temperature are preferred. This is because, in the case of a solid, chloride having a low boiling point is hardly generated. Examples of the liquid used here include ethanol and methanol. Of these, ethanol is preferred. When ethanol is used in the thermal decomposition treatment, for example, the following reaction occurs with hydrogen chloride generated in the dehydrochlorination reaction to generate ethyl chloride.

[0014]

[Chemical Formula 2] C ₂ H ₅ OH + HCl → C ₂ H ₅ Cl + H ₂ O

The boiling point of the produced ethyl chloride is 12.30.
° C, which is lower than the thermal decomposition treatment temperature, so that it can be removed from the system of the thermal decomposition treatment apparatus by a method such as pressure reduction.

On the other hand, examples of the gaseous chloride generating substance include acetylene and ethylene, and acetylene or ethylene is particularly preferable. Of these, acetylene reacts with hydrogen chloride as follows to produce 1,1-dichloroethane and 1,2-dichloroethane.

[0017]

Embedded image

The resulting 1,1-dichloroethane and 1,1
Since the boiling points of 2-dichloroethane are 57.3 ° C. and 83.38 ° C., respectively, which are lower than the thermal decomposition treatment temperature,
It can be removed from the system of the thermal decomposition apparatus by a method such as decompression.

The gaseous chloride-generating substance is put into a thermal decomposition treatment apparatus together with waste plastic, and reacts with chlorine compounds such as chlorine and hydrogen chloride to produce gaseous chloride. The amount of the gaseous chloride generating substance is not particularly limited, but is preferably 1 to 2 equivalents to the generated chlorine and / or chlorine compound in consideration of the effect and cost.

Examples of the chlorine-based polymer contained in the waste plastic include polyvinyl chloride, polyvinylidene chloride, chlorinated polyethylene and the like.

The thermal decomposition apparatus used in the present invention includes:
For example, waste plastic inlet, molten plastic outlet, chlorine and chlorine compound outlet, heating means for heating waste plastic,
One provided with mixing / kneading means for kneading.
If necessary, an inlet for a gaseous chloride generating substance may be provided. The shape of such a pyrolysis apparatus is not particularly limited, and examples thereof include a batch type pyrolysis apparatus and a continuous pyrolysis apparatus such as an extruder. In the case of a continuous pyrolysis apparatus, the apparatus further has a guide means for guiding waste plastic from one end to the other end.

The heating means is not particularly restricted but includes, for example, heating by a heater. Such heating may be performed from the outside of the reaction tube, or may be performed by incorporating a heater or the like inside the thermal decomposition treatment apparatus. The mixing / kneading means is not particularly limited, and includes, for example, a rotary blade in a batch processing apparatus and a screw in a continuous processing apparatus. Further, the guide means is not particularly limited, but includes, for example, a case using a screw, a case where pressure is applied from one end side, and the like.

FIG. 1 is a schematic view showing a cross section of an example of a batch type pyrolysis apparatus. Waste plastic as a raw material is supplied from a raw material supply port 2 and is supplied to a pyrolysis tank 1 having a heating means 6.
The gaseous chloride-generating substance is injected from the injection port 9 while being mixed and kneaded for a predetermined time by the rotary blade 5 as a mixing and kneading means, and then discharged from the molten plastic outflow port 3. Chlorine or a chlorine compound generated by thermal decomposition of waste plastic during mixing and kneading is discharged from the outlet 4.

FIG. 2 is a schematic view showing a cross section of an example of a continuous thermal decomposition apparatus. Waste plastic as a raw material is supplied from a raw material supply hopper 12, melted in a pyrolysis cylinder (reaction tube) 11 having a heating means 16, further mixed and kneaded, and a screw 15 as a transportation means of the waste plastic. While mixing, kneading and transporting, the gaseous chloride generating substance is injected from the inlet 19,
After a predetermined residence time, the molten plastic is discharged from a molten plastic outlet (die) 13. Chlorine or chlorine compounds generated by thermal decomposition of waste plastic during mixing, kneading or transportation are discharged from the outlet 14.

The pyrolysis apparatus is not particularly limited as described above. However, in the batch type pyrolysis apparatus, the molten plastic which has undergone pyrolysis adheres to and accumulates on the wall surface in the pyrolysis tank, causing burning of the material. In particular, it is desirable to use a continuous thermal decomposition apparatus in order to generate the heat generation.

Further, the type of the continuous pyrolysis apparatus is also
Although not particularly limited, a multi-axial thermal decomposition treatment apparatus having self-cleaning properties is preferable. In the case of a single shaft, since there is no self-cleaning property, the material may stay in the thermal decomposition processing apparatus. The processing conditions when using a batch type pyrolysis apparatus as shown in FIG. 1 as the pyrolysis apparatus are not particularly limited, but the set pyrolysis temperature is 300 ° C. to 400 ° C., and the residence time is 20 minutes or more. It is preferable that If the thermal decomposition temperature exceeds 400 ° C., particularly when the waste plastic before treatment is converted into a solid fuel or oil, the volatilization amount of the fuel component in the waste plastic may increase, which is not preferable. Pyrolysis temperature is 3
If the temperature is lower than 00 ° C., waste plastic cannot be sufficiently thermally decomposed and chlorine and chlorine compounds remain in the material, which is not preferable. If the residence time is less than 20 minutes, waste plastics may not be sufficiently thermally decomposed, which is not preferable.

The processing conditions when a continuous pyrolysis apparatus as shown in FIG. 2 is used as the pyrolysis apparatus are not particularly limited.
At 400 ° C., the residence time is preferably at least 1 minute, particularly preferably at least 3 minutes. If the pyrolysis temperature exceeds 400 ° C,
In particular, when the treated waste plastic is used as a solid fuel, the volatilization amount of the fuel component in the waste plastic may increase, which is not preferable. Thermal decomposition temperature is 30
If the temperature is lower than 0 ° C., the waste plastic cannot be sufficiently thermally decomposed and chlorine and chlorine compounds remain in the material, which is not preferable. If the residence time is less than 1 minute, the waste plastic may not be sufficiently thermally decomposed, which is not preferable.

The method for removing chlorine or chlorine compounds from the chlorine or chlorine compound outlet is not particularly limited, and can be performed, for example, by a method such as decompression.

[0029]

EXAMPLES Next, the present invention will be further described with reference to examples, but the present invention is not limited to the following examples.

Example 1 As a continuous pyrolysis apparatus, a two-axis co-rotating mesh with one chlorine and chlorine compound outlet between a waste plastic inlet and a molten plastic outlet shown in FIG. Using TEX44-49AW (manufactured by Nippon Steel Works) which is a mold extruder, ethanol 25 kg / hr was added to waste plastic 35 kg / hr, and dehydrochlorination was performed for 60 minutes. Table 1 shows the results.

Example 2 Using the same apparatus as in Example 1, waste plastic 35 kg
/ Hr was added with 1.4 kg / hr of acetylene, and dehydrochlorination was performed for 60 minutes. Table 1 shows the results.

Comparative Example 1 Using the same apparatus as in Examples 1 and 2, dehydrochlorination was performed using only waste plastic. Table 1 shows the results.

[0033]

[Table 1]

From the results shown in Table 1, when ethanol was added to the crushed urban waste plastic product of Example 1, and when acetylene was added to the crushed urban waste plastic product of Example 2, the comparative example showed that It can be seen that the chlorine content after treatment is smaller than in the case of only waste plastic crushed products.

[0035]

According to the present invention, a chlorine compound having a low boiling point is produced by adding and mixing and kneading a gaseous chloride generating substance in the thermal decomposition treatment of waste plastic,
By efficiently removing the low-boiling chlorine compound, it has become possible to efficiently and easily remove chlorine or a chlorine compound generated by thermal decomposition from waste plastic.

[Brief description of the drawings]

FIG. 1 is a schematic view of a batch-type pyrolysis apparatus for removing chlorine or chlorine compounds generated by thermal decomposition from waste plastics according to an embodiment of the present invention.

FIG. 2 is a schematic view of a continuous pyrolysis apparatus for removing chlorine or chlorine compounds generated by pyrolysis from waste plastics according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pyrolysis tank 11 Pyrolysis cylinder (reaction cylinder) 2,12 Waste plastic input port (raw material supply hopper) 3,13 Molten plastic outlet 4,14 Chlorine or chlorine compound discharge port 5 Rotating blade 15 Screw (guide means) 6,16 Heating means 7,17 Motor 8,18 Reduction gear 9,19 Inlet of gaseous chloride generating substance

Continuing on the front page (72) Inventor Yukihiro Sumihiro 1-6-1, Funakoshi-minami, Aki-ku, Hiroshima City, Hiroshima Prefecture Inside Japan Steel Works Co., Ltd. No. 1 Inside the Japan Steel Works, Ltd. (72) Kunihiko Koyanagi, Inventor Kunihiko Koyanagi 1-6-1, Funakoshi Minami, Aki-ku, Hiroshima-shi, Hiroshima Prefecture Inside Japan Steel Works, Ltd. No. 1 Hiroshima University Faculty of Engineering

Claims (10)

[Claims] 1. A waste plastic containing a chlorine-based polymer, wherein a substance which reacts with hydrogen chloride to generate gaseous chloride at a thermal decomposition treatment temperature is added to the waste plastic, and the waste plastic is subjected to a thermal decomposition treatment. Processing method. 2. The processing method according to claim 1, wherein the substance which reacts with hydrogen chloride to generate a gaseous chloride at a pyrolysis temperature is a liquid or a gas at room temperature. 3. The addition amount of a substance which reacts with hydrogen chloride and generates gaseous chloride at a thermal decomposition treatment temperature is 1 to 2 equivalents of chlorine and / or a chlorine compound generated by the thermal decomposition treatment. Item 3. The processing method according to item 1 or 2. 4. The treatment method according to claim 1, wherein the substance which reacts with hydrogen chloride to generate gaseous chloride at a thermal decomposition treatment temperature is ethanol, acetylene or ethylene. 5. The pyrolysis treatment includes a waste plastic inlet, a molten plastic outlet, a chlorine and chlorine compound outlet, a heating means for heating the waste plastic, and a mixing / kneading for mixing / kneading the molten plastic. 5. The method according to claim 1, wherein the heat treatment is performed by a thermal decomposition treatment apparatus having the means.
The method according to claim 1. 6. The processing method according to claim 5, wherein the thermal decomposition apparatus is a batch type thermal decomposition apparatus. 7. The processing method according to claim 6, wherein the set temperature of the thermal decomposition of the batch type thermal decomposition apparatus is 300 ° C. to 400 ° C., and the residence time is 20 minutes or more. 8. The processing method according to claim 5, wherein the thermal decomposition apparatus is a continuous thermal decomposition apparatus. 9. The processing method according to claim 8, wherein the continuous pyrolysis apparatus has a set pyrolysis temperature of 300 ° C. to 400 ° C. and a residence time of 1 minute or more. 10. The processing method according to claim 8, wherein the continuous thermal decomposition apparatus is a multi-axial thermal decomposition apparatus having a self-cleaning property.