JP3417838B2 - Waste plastic treatment method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to chlorine and / or chlorine generated during thermal decomposition treatment of waste plastic containing a chlorine-based polymer.
Alternatively, the present invention relates to a method for efficiently removing a chlorine compound to obtain a molten plastic having a small residual chlorine content.

[0002]

2. Description of the Related Art Waste plastics contained in general wastes and industrial wastes have been conventionally disposed of by landfilling, but in recent years, from the viewpoint of environmental protection and effective use of resources, low molecular weight and low chemical recycling have been achieved. Attention has been focused on reduction of boiling point oil, that is, oil recovery and energy recovery by combustion as thermal recycling.

By the way, chemical recycling and thermal recycling process waste plastics at a high temperature. When the waste plastics contain chlorine-based polymers such as polyvinyl chloride and polyvinylidene chloride,
Chlorine is generated during processing, which causes major problems such as corrosion of processing equipment, deterioration of product (oil) quality, reduction of heat and electric energy recovery rate, and generation of harmful dioxins. It was For this reason, the method of separating and removing the chlorine-based polymer from the waste plastic, and when performing chemical recycling or thermal recycling, the chlorine-based polymer in the waste plastic is thermally decomposed to remove chlorine as a pretreatment. Dechlorination pretreatment is performed.

[0004]

However, the conventional methods for separating and removing chlorine-based polymers require complicated equipment because of the need for an apparatus for separating and removing chlorine polymers. Therefore, there is a problem that it is difficult to completely remove the chlorine-based polymer.

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

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

That is, in the conventional thermal decomposition treatment apparatus, the chlorine-based polymer in the waste plastic generally undergoes reactions such as dehydrochlorination reaction when heated to 190 to 200 ° C. or higher. 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 molten molten plastic outlet is generally 300 to 350.
It often becomes ℃. Here, the reason why the thermal decomposition treatment temperature is higher than the decomposition start temperature of the chlorine-based polymer is that the thermal decomposition rate of the chlorine-based polymer in the waste plastic is increased and dechlorination is carried out in the shortest possible time. The residence time of the waste plastic in the thermal decomposition treatment apparatus is generally 3 to 5 minutes or longer. Therefore, the generation of chlorine or chlorine compounds in the thermal decomposition treatment device gradually occurs from the input of waste plastic to the discharge of molten plastic. Therefore, depending on the generation position of chlorine or a chlorine compound in the device, the generated chlorine or chlorine compound may be an inorganic filler such as calcium carbonate, talc, or titanium oxide existing in the waste plastic before reaching these outlets. , 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. By way of example, the boiling points of such chlorides are 1600 ° C. or higher for calcium chloride, 1412 ° C. for magnesium chloride, 1500 ° C. for potassium chloride, 1413 ° C. for sodium chloride, and 440 ° C. or higher for titanium trichloride.

Therefore, an object of the present invention is to provide chlorine and / or chlorine generated by thermal decomposition of waste plastics containing a 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 of a chlorine compound with an inorganic filler or the like to generate a high boiling point compound.

[0011]

In view of such circumstances, the present inventors have conducted diligent research, and as a result, during the thermal decomposition treatment of waste plastics containing a chlorine-based polymer, they react with hydrogen chloride at the thermal decomposition treatment temperature. The inventors have found that when a specific substance that generates gaseous chloride is added, chlorine and / or chlorine compounds generated by thermal decomposition are not captured by an inorganic filler or the like and can be efficiently removed from molten plastic, and the present invention has been completed.

That is, the present invention provides a method for treating waste plastics, which comprises adding ethanol, acetylene or ethylene to waste plastics containing a chlorine-based polymer and subjecting the waste plastics to thermal decomposition treatment.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION As a substance which reacts with hydrogen chloride used in the present invention to generate gaseous chloride at a thermal decomposition treatment temperature (hereinafter, referred to as "gaseous chloride generating substance"), it is a liquid or a gas at room temperature. Are preferred. This is because in the case of a solid, it is difficult to generate a low boiling point chloride. The liquid used here is ethanol, and when ethanol is used for the thermal decomposition treatment, for example, the following reaction occurs with hydrogen chloride produced in the dehydrochlorination reaction to produce ethyl chloride.

[0014]

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

The boiling point of ethyl chloride produced is 12.30.
Since the temperature is 0 ° C., which is lower than the thermal decomposition temperature, it can be removed outside the system of the thermal decomposition apparatus by a method such as decompression.

On the other hand, gaseous gaseous chloride generating substances are acetylene and ethylene, of which acetylene is
Reacts with hydrogen chloride as follows to give 1,1-dichloroethane and 1,2-dichloroethane.

[0017]

[Chemical 3]

1,1-dichloroethane and 1, 1, which are produced
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 outside the system of the thermal decomposition treatment apparatus by a method such as decompression.

The gaseous chloride-generating substance is introduced into the thermal decomposition treatment apparatus together with the waste plastic, and reacts with chlorine compounds such as chlorine and hydrogen chloride to generate gaseous chloride. The addition amount of the gas chloride generating substance is not particularly limited, but in consideration of the effect and the cost, it is preferably 1 to 2 times the equivalent amount with respect to the generated chlorine and / or chlorine compound.

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

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

The heating means is not particularly limited, but for example, heating with a heater can be mentioned. 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 examples thereof include a rotary blade in a batch type processing device and a screw in a continuous type processing device. Further, the guide means is not particularly limited, and examples thereof include a case of using a screw and a case of applying pressure from one end side.

FIG. 1 is a schematic view showing a cross section of an example of a batch type thermal decomposition treatment apparatus. Waste plastic as a raw material is charged from a raw material supply port 2 and has a thermal decomposition tank 1 having a heating means 6.
After being melted inside, and further mixed and kneaded for a predetermined time by a rotary blade 5 as a mixing and kneading means, a gaseous chloride generating substance is injected from an injection port 9 and then discharged from a molten plastic outlet 3. Chlorine or chlorine compounds generated by thermal decomposition of waste plastic during mixing / kneading are discharged from the discharge port 4.

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

The thermal decomposition treatment apparatus is not particularly limited as described above, but in the batch type thermal decomposition treatment apparatus, the molten plastic that has undergone thermal decomposition adheres to and stays on the wall surface in the thermal decomposition tank to burn the material. It is particularly desirable to use a continuous thermal decomposition treatment apparatus in order to generate heat.

Further, the type of continuous thermal decomposition treatment apparatus is also
Although not particularly limited, a multiaxial thermal decomposition treatment device having a self-cleaning property is preferable. In the case of the uniaxial type, since there is no self-cleaning property, the material may stay in the thermal decomposition processing apparatus. Moreover, the processing conditions when using a batch type thermal decomposition processing apparatus as shown in FIG. 1 as the thermal decomposition processing apparatus are not particularly limited, but the thermal decomposition setting 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, the volatilization amount of the fuel component in the waste plastic may increase, especially when the waste plastic before treatment is converted into a solid fuel or oil, which is not preferable. Pyrolysis temperature is 3
If the temperature is lower than 00 ° C., the waste plastic cannot be thermally decomposed sufficiently, and chlorine and chlorine compounds remain in the material, which is not preferable. If the residence time is less than 20 minutes, waste plastic may not be sufficiently thermally decomposed, which is not preferable.

Further, the processing conditions when the continuous thermal decomposition processing apparatus as shown in FIG. 2 is used as the thermal decomposition processing apparatus are not particularly limited, but the thermal decomposition setting temperature is 300 ° C.
At 400 ° C., the residence time is preferably 1 minute or longer, particularly 3 minutes or longer. If the thermal decomposition temperature exceeds 400 ° C,
In particular, when the waste plastic after the treatment is used as a solid fuel, the volatilization amount of the fuel component in the waste plastic may increase, which is not preferable. Pyrolysis temperature is 30
If the temperature is lower than 0 ° C, the waste plastic cannot be thermally decomposed sufficiently, 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 of removing chlorine or chlorine compound from the chlorine or chlorine compound discharge port is not particularly limited, and it can be carried out 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 thermal decomposition treatment apparatus, biaxial co-rotating meshing with a single chlorine and chlorine compound outlet provided between a waste plastic inlet and a molten plastic outlet as shown in FIG. Using a model extruder TEX44-49AW (manufactured by Japan Steel Works, Ltd.), 25 kg / hr of ethanol was added to 35 kg / hr of waste plastic to perform dehydrochlorination for 60 minutes. The results are shown in Table 1.

Example 2 Using the same apparatus as in Example 1, 35 kg of waste plastic
1.4 kg / hr of acetylene was added to the mixture / hr for dehydrochlorination for 60 minutes. The results are shown in Table 1.

Comparative Example 1 Using the same apparatus as in Example 1 and Example 2, dehydrochlorination was carried out only with waste plastic. The results are shown in Table 1.

[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 plastic waste product of Example 2, the urban type of Comparative Example was used. It can be seen that the chlorine content after treatment is smaller than in the case of only waste plastic crushed products.

[0035]

INDUSTRIAL APPLICABILITY In the present invention, a low boiling point chlorine compound 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 point chlorine compound, it has become possible to efficiently and easily remove chlorine or a chlorine compound generated by thermal decomposition from the waste plastic.

[Brief description of drawings]

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

FIG. 2 is a schematic view of a continuous thermal decomposition treatment apparatus for removing chlorine or chlorine compounds generated by thermal decomposition from waste plastic according to the embodiment of the present invention.

[Explanation 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 Port 4,14 Chlorine or Chlorine Compound Discharge Port 5 Rotating Blade 15 Screw (Guide Means) 6,16 Heating means 7,17 Motor 8,18 Speed reducer 9,19 Gas chloride generating substance inlet

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yukihiro Sumihiro 1-6-1, Funakoshi Minami, Aki-ku, Hiroshima City, Hiroshima Prefecture Japan Steel Works, Inc. (72) Inventor Takeshi Fukushima Minami Funakoshi, Aki-ku, Hiroshima City, Hiroshima Prefecture Chome 6-1-1 Japan Steel Works Co., Ltd. (72) Inventor Kunihiko Koyanagi 1-6-1-1, Funakoshi Minami, Aki-ku, Hiroshima City, Hiroshima Prefecture Japan Steel Works Co., Ltd. (72) Ken Hirokawa Ichika Kagamiyama, Higashi-Hiroshima City, Hiroshima Prefecture Citation No. 4-1-1, Faculty of Engineering, Hiroshima University (56) Reference JP-A-53-40380 (JP, A) JP-A-6-136458 (JP, A) JP-A-10-85554 (JP, A) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) C08J 11/00-11/28 B29B 17/00-17/02

Claims (8)

(57) [Claims] 1. A method for treating waste plastic, which comprises adding ethanol, acetylene or ethylene to waste plastic containing a chlorine-based polymer and subjecting it to thermal decomposition treatment. 2. The treatment method according to claim 1, wherein the amount of ethanol, acetylene or ethylene added is 1 to 2 times the equivalent of chlorine and / or chlorine compounds generated by the thermal decomposition treatment. 3. Pyrolysis treatment, waste plastic input port, molten plastic outlet, chlorine and chlorine compound discharge port, heating means for heating waste plastic, mixing / kneading for mixing and kneading molten plastic The method according to claim 1 or 2, which is carried out by a thermal decomposition treatment apparatus provided with a means. 4. The processing method according to claim 3, wherein the thermal decomposition treatment apparatus is a batch type thermal decomposition treatment apparatus. 5. The processing method according to claim 4, wherein the preset thermal decomposition temperature of the batch type thermal decomposition apparatus is 300 ° C. to 400 ° C., and the residence time is 20 minutes or more. 6. The processing method according to claim 3, wherein the thermal decomposition treatment apparatus is a continuous thermal decomposition treatment apparatus. 7. The processing method according to claim 6, wherein the thermal decomposition set temperature of the continuous thermal decomposition apparatus is 300 ° C. to 400 ° C., and the residence time is 1 minute or more. 8. The continuous pyrolysis treatment apparatus is a multi-axis pyrolysis treatment apparatus having a self-cleaning property.
Or the processing method described in 7.