JP7107685B2 - How to treat chlorine-containing plastics - Google Patents

Description

The present invention relates to a method for treating chlorine-containing plastics.

Chlorine-containing plastics such as polyvinyl chloride are widely used, for example, as materials for transparent sheets and piping. Incineration is widely used as a method for treating waste containing chlorine-containing plastics. However, from the viewpoint of resource reuse, it is also being studied to recover organic components in chlorine-containing plastics and use them as a substitute for fuel.

In Patent Document 1, organic waste containing chlorine is introduced into a reaction vessel, superheated steam at 210 to 240 ° C. is supplied to and discharged from the reaction vessel at normal pressure, and organic waste in the waste is removed in the reaction vessel. A method is disclosed in which after pyrolyzing chlorine, the solid content remaining in the reaction vessel is taken out of the reaction vessel as a regenerated solid fuel and washed with water.

In Patent Document 2, a waste containing chlorine and an alkali of 3 molar equivalents or more relative to the amount of chlorine in the waste are introduced into a reaction vessel, and superheated steam is supplied to and discharged from the reaction vessel. A method is disclosed in which chlorine is vaporized inside the reaction vessel, the solid content remaining in the reaction vessel is discharged outside the reaction vessel as a regenerated solid fuel, and the regenerated solid fuel is washed with water under predetermined conditions.

In Patent Document 3, a crushed waste product containing chlorine-containing plastic and a solid alkali metal compound or alkaline earth metal compound are introduced into a reaction vessel, and superheated steam of 210 to 350 ° C. is added. It is supplied to and discharged from the reaction vessel, and the hydrogen chloride generated by the decomposition of the plastic in the waste in the reaction vessel is captured by the alkali metal compound or alkaline earth metal compound, fixed to the solid phase, and remains in the reaction vessel. Disclosed is a method for discharging the recovered solid content out of the reaction vessel as a regenerated solid fuel. In the method disclosed in Patent Document 3, after crushing the solid content drawn out of the reaction vessel, it is classified using a sieve, and only the finely divided solid content with a high chlorine concentration that has passed through the sieve mesh by classification. I am washing.

Japanese Patent No. 6022745 Japanese Patent No. 5732278 Japanese Patent No. 5845124

In the chlorine-containing plastic treatment methods described in Patent Documents 1 to 3, the chlorine-containing plastic is treated at a relatively low temperature. Therefore, there is an advantage that volatilization of the organic component contained in the plastic can be reduced, and a relatively large amount of high calorific value carbide can be recovered. However, thermoplastics such as polyvinyl chloride generally soften and melt at 90 to 330°C. There is the problem that it is difficult to process chlorine-containing plastics continuously over a long period of time, as they form particles which can clog the outlet of the reaction vessel. In addition, if the heating temperature of the chlorine-containing plastic is low, thermal decomposition does not proceed, and there is also the problem that organic chlorine remains. In addition, since heavy pyrolysis products (tar) may clog the discharge port of the reaction vessel, it is important to suppress the formation of tar. Furthermore, since carbonized products at low temperatures contain heavy thermal decomposition products such as tar, when the carbonized products are washed with water, the amount of organic matter in the wastewater increases, complicating wastewater treatment. Furthermore, in the treatment of chlorine-containing plastics, it is also important to suppress highly harmful by-products such as dioxins by fixing hydrogen chloride generated by thermal decomposition with high efficiency.

The present invention has been made in view of the above-mentioned circumstances, and its object is to be able to continuously treat chlorine-containing plastics over a long period of time, and to remove hydrogen chloride generated by thermal decomposition of chlorine-containing plastics. To provide a method for treating chlorine-containing plastics capable of fixing with high efficiency and hardly generating dioxins.

In order to solve the above problems, the method for treating chlorine-containing plastics of the present invention provides chlorine-containing plastics with at least one calcium compound selected from the group consisting of calcium hydroxide, calcium carbonate and calcium oxide. A mixture obtained by mixing at a ratio such that the molar ratio of the amount of calcium in the calcium compound to the amount of chlorine in the containing plastic is within the range of 2 or more and 10 or less is heated at a temperature of 500° C. or more and 900° C. or less in a non-oxidizing atmosphere. a pyrolysis step of generating a pyrolysis gas of the chlorine-containing plastic and a carbide, and reacting the chlorine contained in the chlorine-containing plastic with the calcium compound to generate a chlorine-containing calcium compound; a gas recovery step of recovering gas; and classifying the carbide and the chlorine-containing calcium compound using a sieve smaller than the average particle size of the chlorine-containing plastic and larger than the average particle size of the calcium compound. A separation step of separating into fine particles and coarse particles by a method of separating fine particles and coarse particles, a step of washing the chlorine-containing calcium compound separated in the separation step, and a step of washing the carbide separated in the separation step. and a step.

According to the chlorine-containing plastic treatment method of the present invention having such a configuration, in the pyrolysis step, the mixture of the chlorine-containing plastic and the calcium compound is mixed in the above-mentioned ratio, and the mixture is heated at 500° C. in a non-oxidizing atmosphere. Since the heating is performed at a relatively high temperature of 900° C. or less, it is difficult to generate clumps or tar in which chlorine-containing plastics are fused together. Therefore, chlorine-containing plastics can be treated continuously over a long period of time. In addition, hydrogen chloride (HCl) generated by thermal decomposition of chlorine-containing plastic can be efficiently fixed to the calcium compound, and dioxins are less likely to be generated. Furthermore, in the gas recovery process, the pyrolysis gas of chlorine-containing plastics is recovered, but since the chlorine concentration in the pyrolysis gas is low, when used as a fuel alternative gas, the corrosion of equipment and the burden of exhaust gas treatment are very low. . Furthermore, the organic substances contained in the pyrolysis gas can be used as fuel.

The carbide separated in the separation process can be used as a high-grade fuel substitute, and the chlorine-containing calcium compound can be used as a cement raw material substitute or a calcium compound for fixing chlorine after desalination.

According to the present invention, chlorine-containing plastics can be continuously treated for a long period of time, hydrogen chloride generated by thermal decomposition of chlorine-containing plastics can be fixed with high efficiency, and dioxins are difficult to generate. It is possible to provide a processing method for

1 is a flow chart showing a method for treating chlorine-containing plastics according to one embodiment of the present invention; FIG. 1 is a cross-sectional view showing the configuration of a heat treatment apparatus that can be advantageously used in the method for treating chlorine-containing plastics according to one embodiment of the present invention. FIG.

Hereinafter, a method for treating chlorine-containing plastics, which is an embodiment of the present invention, will be described with reference to the accompanying drawings.

FIG. 1 is a flow diagram showing a method for treating chlorine-containing plastics according to one embodiment of the present invention.
As shown in FIG. 1, the chlorine-containing plastic treatment method of the present embodiment includes a mixing step S01 of mixing the chlorine-containing plastic and a calcium compound, and a thermal decomposition step S02 of heating the mixture obtained in the mixing step S01. , a gas recovery step S03 for recovering the pyrolysis gas of the chlorine-containing plastic, a separation step S04 for separating the solid content generated in the pyrolysis step S02 into fine particles and coarse particles, and the fine particles separated in the separation step S04 A fine particle cleaning step S05 for cleaning objects and a coarse particle cleaning step S06 for cleaning coarse particles separated in the separation step are provided.

(Mixing step S01)
In the mixing step S01, a chlorine-containing plastic to be treated and a calcium compound are mixed to obtain a mixture. The mixing may be dry or wet. As the mixing device, a mixing device such as a tumbler mixer, a drum mixer, or a ribbon mixer, which is generally used for mixing fine powder, can be used. If the furnace type of the heating device used in the heating step S02 can sufficiently flow inside such as a rotary kiln, the mixing step may be omitted. However, in this case, it is preferable to adjust the introduction rate of the chlorine-containing plastic and the calcium compound so that the mixture in the heat treatment apparatus has a predetermined Ca/Cl ratio. In this mixing step S01, drying, heat quantity adjustment, chemical composition adjustment, particle size adjustment, etc. may be performed simultaneously so that the heat treatment can be performed efficiently.

Chlorine-containing plastics are, for example, waste plastic products containing chlorine-containing plastics. Examples of chlorine-containing plastics include polyvinyl chloride and polyvinylidene chloride. Chlorine-containing plastics may include non-chlorine-containing plastics and combustibles such as wood chips and rubber. The chlorine content of the chlorine-containing plastic is preferably in the range of 0.5 mass % or more and 60 mass % or less. The particle size of the chlorine-containing plastic is not particularly limited, but is usually in the range of 1 mm or more and 150 mm or less.

The calcium compound contains at least one selected from the group consisting of calcium hydroxide, calcium carbonate and calcium oxide. In the pyrolysis step S02, the calcium compound has the effect of accelerating the thermal decomposition of the chlorine-containing plastic to lighten the thermal decomposition product, and the hydrogen chloride (HCl) generated by the thermal decomposition of the chlorine-containing plastic is converted into calcium chloride or chloride. It has an effect of fixing as calcium hydroxide.

The calcium compound may contain components other than calcium hydroxide, calcium carbonate and calcium oxide. For example, incineration fly ash or dust may be used as the calcium compound. Incineration fly ash is fine particles produced by neutralizing acid gas containing chlorine-based gas generated in the incineration of municipal waste with a calcium compound (particularly calcium hydroxide and calcium oxide). Soot and dust are fine particles produced by neutralizing acid gases, including chlorine-based gases, generated by incineration of industrial waste with calcium compounds. Although they contain chlorine, they can be used as calcium compounds because they contain a large amount of chlorine and unbound calcium. It is more effective if chlorine is removed in advance by washing with water or the like. These may be used individually by 1 type, and may be used in combination of 2 or more type. For the same reason, chlorine bypass dust by-produced in cement plants and dried neutralized sludge from industrial wastewater can also be used.

The calcium compound preferably has a smaller particle size than the chlorine-containing plastic. When the particle size of the calcium compound is small, it becomes easier to separate the solid content into fine particles and coarse particles in the separation step S04. The median diameter of the calcium compound is preferably 100 µm or less. On the other hand, if the particle size of the calcium compound becomes too small, the amount of dust generated in the thermal decomposition step S02 may increase. There is a risk of scattering in the generated pyrolysis gas. Therefore, the calcium compound preferably has a median diameter of 1 μm or more.

The mixing ratio of the chlorine-containing plastic and the calcium compound is such that the ratio of the amount of calcium in the calcium compound to the amount of chlorine in the chlorine-containing plastic (Ca/Cl ratio) is within the range of 2 or more and 10 or less in terms of molar ratio. If the Ca/Cl ratio is less than 2, the amount of hydrogen chloride fixed to the calcium compound may decrease in the thermal decomposition step S02, and hydrogen chloride may easily be mixed into the thermal decomposition gas. In addition, in the thermal decomposition step S02, the thermal decomposition of the chlorine-containing plastic is not accelerated, and heavy thermal decomposition products (tar) are likely to be generated. On the other hand, when the Ca/Cl ratio exceeds 10, not only are the above effects saturated, but the amount of chlorine-containing plastics to be treated becomes relatively small, resulting in a reduction in the efficiency of chlorine-containing plastics treatment. The Ca/Cl ratio is preferably in the range of 3 or more and 10 or less.

(Thermal decomposition step S02)
In the pyrolysis step S02, the mixture obtained in the mixing step S01 is heated to generate a pyrolysis gas of the chlorine-containing plastic and a carbide, and the chlorine contained in the chlorine-containing plastic reacts with the calcium compound to produce chlorine. Generates contained calcium compounds.

Heating of the mixture is performed in a non-oxidizing atmosphere. A non-oxidizing atmosphere is one in which chlorine-containing plastics do not oxidize (burn). The non-oxidizing atmosphere is preferably an atmosphere in which the oxygen concentration is adjusted to 1% by volume or less. Specifically, an inert gas atmosphere such as nitrogen, water vapor, carbon dioxide, and argon, and a negative pressure atmosphere can be used.

The heating temperature is 500° C. or higher and 900° C. or lower. If the heating temperature is less than 500° C., there is a risk that clumps of fused chlorine-containing plastics may be formed. On the other hand, if the heating temperature exceeds 900° C., the chlorine-containing calcium compound is thermally decomposed, and hydrogen chloride gas is likely to be mixed into the thermal decomposition gas.

The heating time varies depending on factors such as the heating temperature, the chlorine content of the chlorine-containing plastic, and the mixing ratio of the chlorine-containing plastic and the calcium compound in the mixture, but is generally within the range of 15 minutes or more and 120 minutes or less, preferably 20 minutes. minutes or more and 60 minutes or less.

(Gas recovery step S03)
In the gas recovery step S03, the pyrolysis gas of the chlorine-containing plastic is recovered. Pyrolysis gases typically contain combustible materials such as hydrogen, carbon monoxide, and low molecular weight hydrocarbon compounds. Examples of hydrocarbon compounds include methane, ethane, ethylene, propane, propene, butane, butene, and the like. The pyrolysis gas containing such combustible substances can be used as fuel. For example, the pyrolysis gas can be used as fuel for the heat treatment device used in the pyrolysis step S02.

Here, an example of a heat treatment apparatus using pyrolysis gas as fuel will be described with reference to FIG. FIG. 2 is a cross-sectional view showing the configuration of a heat treatment apparatus that can be advantageously used in the method for treating chlorine-containing plastics according to one embodiment of the present invention.
The heat treatment apparatus 10 is an externally heated rotary kiln having an inner cylinder 20 and an outer cylinder 30 accommodating the inner cylinder 20, as shown in FIG.

The inner cylinder 20 has a mixture supply port 21 at one end and an outlet 22 for solids (carbides and chlorine-containing calcium compounds) produced by heating the mixture at the other end. The inner cylinder 20 has an outlet 23 for pyrolysis gas generated by heating the mixture on its side surface. In addition, the inner cylinder 20 has inner cylinder rotating devices 24 for rotating the inner cylinder 20 at both ends.

The outer cylinder 30 heats the inner cylinder 20 by burning the pyrolysis gas extracted from the thermal decomposition gas outlet 23 of the inner cylinder 20 . The outer cylinder 30 is provided with an air inlet (not shown), an auxiliary burner 31, and a smoke outlet 32 for discharging combustion gas generated by combustion of the pyrolysis gas to the outside.

In the heat treatment apparatus 10, the mixture supplied from the mixture supply port 21 is heated while being agitated by the rotation of the inner cylinder 20 to generate pyrolysis gas, carbides, and chlorine-containing calcium compounds. The pyrolysis gas is taken out to the outer cylinder 30 through the pyrolysis gas outlet 23 .
Solids (carbides and chlorine-containing calcium compounds) are taken out through a solids take-out port 22 . On the other hand, the pyrolysis gas taken out to the outer cylinder 30 is combusted to generate combustion gas 25 . The combustion gas 25 is taken out to the outside through the smoke outlet 32 . The combustion gas 25 taken out may be processed in a secondary combustion furnace. A cement firing kiln may be used as the secondary combustion furnace.

The outer cylinder 30 of the heat treatment device 10 may be equipped with a chlorine analyzer for measuring the chlorine concentration of the combustion gas 25 . In this case, when the chlorine concentration of the combustion gas 25 becomes high, it is possible to take countermeasures such as increasing the ratio of the calcium compound in the mixture to improve the chlorine fixation efficiency.

(Separation step S04)
The separation step S04 separates the solid content (mixture of carbide and chlorine-containing calcium compound) generated in the thermal decomposition step S02 into fine particles and coarse particles. Specifically, by classifying using a sieve smaller than the average particle size of the chlorine-containing plastic and larger than the average particle size of the calcium compound, fine particles and coarse particles are separated. By doing so, it is possible to separate the fine particles relatively rich in chlorine-containing calcium compounds and the coarse particles relatively rich in carbides.

(Fine particle cleaning step S05)
In the fine particle washing step S05, the fine particles separated in the separation step S04 are washed with water. This water washing dissolves and removes soluble salts such as calcium chloride in the fine particles. As a method for washing with water, a method of suspending the fine particles in water and washing with stirring, a method of showering the fine particles with water, or the like can be used. The washed fines can be dewatered using pressure filtration equipment, centrifugal separation equipment, vacuum filtration equipment, vibration dewatering, and the like.

The fine particles after washing contain a large amount of calcium carbonate or calcium hydroxide. Therefore, the fine particles after washing can be used as a substitute for cement raw materials. It can also be reused as a calcium compound for fixing chlorine.

(Coarse particle cleaning step S06)
In the coarse particle washing step S06, the coarse particles separated in the separation step S04 are washed with water. This water washing dissolves and removes soluble salts such as calcium chloride in the coarse particles. As the washing method, the same method as the washing method for fine particles can be used. The washed coarse particles can be dewatered using a pressure filtration device, a centrifugal separation device, a vacuum filtration device, vibration dehydration, or the like. If the coarse particles cannot be efficiently washed with water, the coarse particles may be pulverized in advance and washed to improve the washing efficiency.

The coarse particles after washing contain a large amount of carbide. The coarse particles after washing can be used as a substitute fuel for rotary kilns for cement production because of their low chlorine content and high calorific value.

According to the method for treating chlorine-containing plastics according to the present embodiment, which is configured as described above, the mixture containing the chlorine-containing plastic and the calcium compound obtained in the mixing step S01 at a predetermined amount ratio is subjected to the thermal decomposition step. In S02, heating is performed at a relatively high temperature of 500° C. or higher and 900° C. or lower in a non-oxidizing atmosphere, so that clumps or tar formed by fusion of chlorine-containing plastics are less likely to form. Therefore, chlorine-containing plastics can be treated continuously over a long period of time. In addition, hydrogen chloride generated by thermal decomposition of chlorine-containing plastic can be efficiently fixed to the calcium compound, and dioxins are less likely to be generated.

Further, in the method for treating chlorine-containing plastics of the present embodiment, a separation step S04 for separating the solids (carbides and chlorine-containing calcium compounds) generated in the thermal decomposition step S02 into fine particles and coarse particles is further performed. Since the fine particles contain a relatively large amount of chlorine-containing calcium compounds, after cleaning in the fine particle cleaning step S05, the fine particles can be reused as a substitute for cement raw materials or as a calcium compound for fixing chlorine. can. In addition, since the coarse particles contain a relatively large amount of carbide, they can be used as a substitute fuel for a rotary kiln for manufacturing cement after being washed in the coarse particle cleaning step S06.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the technical idea of the invention.
For example, in the present embodiment, the pyrolysis gas of the chlorine-containing plastic is used as the fuel for the heat treatment device used in the pyrolysis step S02, but the present invention is not limited to this. For example, pyrolysis gas can be used as an alternative fuel for rotary kilns for cement production.

Further, in the present embodiment, the chlorine-containing calcium compound and the carbide contained in the solid content are separated as fine particles and coarse particles using a sieve in the separation step S04, but the present invention is not limited to this. . For example, wet or dry gravity sorting may be performed. In this case, the low specific gravity material with a low specific gravity contains a relatively large amount of carbide, and the high specific gravity material with a high specific gravity contains a relatively large amount of chlorine-containing calcium compounds. Floating separation may be performed by adhering a highly hydrophobic carbide to the air bubbles. Alternatively, highly conductive carbides may be sorted out by electrostatic force.

Furthermore, in the present embodiment, the solid content is separated into fine particles and coarse particles in the separation step S04, and the fine particle cleaning step S05 and the coarse particle cleaning step S06 are performed, but the present invention is not limited to this. never For example, after washing the solids, the solids may be separated into fine particles and coarse particles.

Furthermore, in the present embodiment, in the fine particle washing step S05, the fine particles (chlorine-containing calcium compound) are washed with water to dissolve and remove soluble salts such as calcium chloride in the fine particles. is not limited to For example, the particulate may be heated to volatilize the chlorine.

Furthermore, in the present embodiment, in the coarse particle washing step S06, the coarse particles are washed with water to dissolve and remove soluble salts such as calcium chloride in the coarse particles. If the chlorine content is low, it may be used as a fuel substitute for a rotary kiln for cement production without washing.

The effects of the present invention will be described below with reference to examples.

[Invention Example 1]
As a chlorine-containing plastic, 5 g of polyvinyl chloride resin (PVC, particle size: 3 to 5 mm) having a total chlorine content of 56.7% by mass was prepared. Calcium hydroxide (purity: 95% by mass or more, median diameter: 20 μm) was mixed with this PVC as a calcium compound so that the Ca/Cl ratio was 2 in molar ratio to prepare a mixture. The prepared mixture was placed in an alumina boat and heat-treated at a temperature of 700° C. for 30 minutes in a nitrogen atmosphere using an electric furnace. After the heat treatment, the output of the electric furnace was set to zero, and after confirming that the temperature inside the electric furnace had dropped to 100° C. or less, the alumina boat was taken out and the solid content in the alumina boat was recovered. During the heat treatment, the gas discharged from the electric furnace was discharged outside after passing through a cold trap.

(Chlorine fixation rate)
The content of inorganic chlorine in the collected solids was measured, and the chlorine fixation rate was calculated from the following formula based on the total chlorine content in the mixture measured in advance. The results are shown in Table 1. Incidentally, the chlorine content was measured by the following method.
Chlorine fixation rate = (inorganic chlorine content in solid content/total chlorine content in mixture) x 100

(Method for measuring chlorine content)
After the sample was ultrasonically leached with an alkaline eluent, filtration was performed to collect the filtrate and leaching residue. The amount of chlorine in the resulting filtrate was measured by ion chromatography to calculate the content of inorganic chlorine in the sample. In addition, after drying the leaching residue in a vacuum dryer, the organic chlorine content is determined according to the method specified in JIS Z 7302-6 (Waste solidified fuel-Part 6: Total chlorine content test method) was measured. Specifically, air was introduced into a quartz combustion tube heated to 1100° C. to burn the sample, and water absorbed the generated gas. The amount of chlorine in the obtained solution was measured by ion chromatography, and the content of organic chlorine in the sample was calculated.
The total amount of inorganic chlorine content and organic chlorine content obtained by the above method was taken as the total chlorine content in the sample.

(Presence or absence of lumps)
The collected solid content was visually observed to confirm the presence or absence of lumps in which grains of carbide were connected to each other. The results are shown in Table 1.

(Recovery rate of condensate recovered by cold trap)
The weight of the precipitate collected by the cold trap was measured, and the recovery rate of the precipitate was calculated from the following formula based on the previously measured weight in the mixture. The results are shown in Table 1.
Recovery rate of coagulum = (1-(weight of coagulum recovered in cold trap/weight in mixture)) x 100

[Invention Examples 2 to 10, Comparative Examples 1 to 5]
The mixture was heat-treated in the same manner as in Invention Example 1, except that the type of calcium compound, the Ca/Cl ratio, and the heating temperature were changed as shown in Table 1 below, and the chlorine fixation rate and lumps were determined. Presence and cold trap recovery of coagulum was evaluated. The results are shown in Table 1.

In Comparative Example 1 in which the Ca/Cl ratio was lower than the range of the present invention and in Comparative Example 2 in which no calcium compound was added, the chlorine fixation rate decreased and the recovery rate of the coagulum recovered in the cold trap was high. became. The reason why the chlorine fixation rate decreased is considered to be that the amount of the calcium compound in the mixture was too small, and the amount of hydrogen chloride fixed to the calcium compound was reduced. In addition, it is considered that the reason why the recovery rate of the condensate was high is that the pyrolysis of the chlorine-containing plastic was not accelerated and heavy pyrolysis products (tar) were generated.
In Comparative Examples 3 and 4, in which the heating temperature was lower than the range of the present invention, the chlorine fixation rate was lowered and lumps were formed in the solid content. The reason why the chlorine fixation rate decreased is considered to be that the chlorine-containing plastic did not undergo thermal decomposition and remained as organic chlorine. It is considered that the lumps were generated because the heating temperature became too low and the melted chlorine-containing plastics fused together.
In Comparative Example 5 in which the heating temperature was higher than the range of the present invention, the chlorine fixation rate was lowered. This is probably because the heating temperature was too high and the chlorine-containing calcium compound was thermally decomposed.

On the other hand, Examples 1 to 10 of the present invention, in which the Ca/Cl ratio and the heating temperature are within the ranges of the present invention, have a high chlorine fixation rate, do not form lumps in the solid content, and are recovered with a cold trap. The recovery rate of the coagulated material was low.
From the above, according to Examples 1 to 10 of the present invention, chlorine-containing plastics can be treated continuously over a long period of time, chlorine can be fixed with high efficiency, and dioxins are unlikely to be generated. It was confirmed that it is possible to provide a method.

[Invention Example 11]
The solid content obtained in Inventive Example 1 was washed. Washing is performed by mixing 10 g of the solid content and 100 mL of distilled water to form a slurry, shaking it for 30 minutes using a shaker, then filtering the slurry under reduced pressure to obtain a cake, and distilling the obtained cake. It was carried out by washing with 100 mL of water. The total organic carbon concentration (TOC) of the waste liquid after washing the solid content (mixture of the filtrate collected during vacuum filtration of the slurry and the distilled water collected during washing of the cake) was measured with a TOC meter. It was 4.5 mg/L.

[Comparative Example 6]
The solid matter was washed in the same manner as in Inventive Example 11, except that the solid matter obtained in Comparative Example 3 was used. As a result of measuring the TOC of the liquid after washing the solid content, it was 785 mg/L.

In Comparative Example 6, in which the solid content obtained in Comparative Example 3, in which the heating temperature was lower than the range of the present invention, was washed, the TOC of the waste liquid increased. This is probably because the heating temperature was too low and thermal decomposition did not proceed, and heavy thermal decomposition products such as tar remained in the solid content.
On the other hand, the solid content obtained in Example 1 of the present invention, in which the heating temperature is within the range of the present invention, was decomposed from heavy thermal decomposition products such as tar, so the solid content was washed and , the TOC of the effluent was low.

[Invention Example 12]
An appropriate amount of PVC (particle diameter: 3-4 mm) is added to RPF (particle diameter: 5-30 mm) with a total chlorine content of 0.2% by mass and mixed in a bag to simulate a total chlorine content of 2% by mass. Waste plastic. A mixture was prepared by mixing calcium hydroxide (purity: 95% by mass or more, median diameter: 20 μm) as a calcium compound with this simulated waste plastic so that the Ca/Cl ratio was 2 in molar ratio. . The prepared mixture is continuously supplied to a gas-heated rotary kiln at a rate of 5 kg / h using a screw feeder, and heat-treated for 30 minutes inside the kiln maintained at a negative pressure (-5 Pa) and 700 ° C., Solids were collected from the outlet at the rear of the kiln. 500 g of the collected solid content was sieved using a sieve with a sieve opening diameter of 1.0 mm, and fine grains were collected under the sieve and coarse grains were collected above the sieve.

The recovered fine particles and coarse particles were each washed. Washing is carried out by mixing 10 g of fine particles or coarse particles and 100 mL of distilled water to prepare a slurry, shaking the mixture with a shaker for 30 minutes, and then filtering the slurry under reduced pressure to obtain a cake. The obtained cake was washed with 100 mL of distilled water.

The washed material (cake) obtained by washing was dried at a temperature of 105° C. using a dryer. The total chlorine content, calcium content, and calorific value of the fine particles and coarse particles after washing and drying thus obtained were measured. The total chlorine content was measured by the method described above. Calcium content and calorific value were measured by the following methods. The results are shown in Table 2.

(Method for measuring calcium content)
The sample was combusted using a burner to obtain ash. Thereafter, the cooled ash was dissolved with an acid, the calcium concentration in the resulting solution was measured by the ICP-AES method, and the obtained calcium concentration was converted to the calcium content in the sample.

(Measurement method of calorific value)
It was measured with an adiabatic cylinder calorimeter.

[Comparative Example 7]
The mixture was heat treated in the same manner as in Invention Example 12, except that the solids recovered from the outlet at the rear of the kiln were not sieved. The recovered solid content was washed and dried in the same manner as in Inventive Example 12. The chlorine content, calcium content and calorific value of the solid content after washing and drying were measured. The results are shown in Table 2.

From the results of Example 6 of the present invention, it is possible to obtain fine particles containing a large amount of calcium (calcium compounds) and coarse particles (carbides) having a large calorific value by classifying the solid content.

[Invention Example 13]
The mixture was heat-treated and the solid content was recovered in the same manner as in Invention Example 1, except that the fine particles obtained in Invention Example 12 were used as the calcium compound. The inorganic chlorine content in the recovered solid content was measured, and the chlorine fixation rate was calculated to be 93.1% by mass. From this result, it was confirmed that the fine particles (calcium compound) obtained by classifying and washing the solid content can be used as a chlorine fixing material.

REFERENCE SIGNS LIST 10 Heat treatment device 20 Inner cylinder 21 Mixture supply port 22 Solid content outlet 23 Pyrolysis gas outlet 24 Inner cylinder rotating device 25 Combustion gas 30 Outer cylinder 31 Support burner 32 Smoke exhaust port

Claims (6)

At least one calcium compound selected from the group consisting of calcium hydroxide, calcium carbonate and calcium oxide is added to a chlorine-containing plastic so that the ratio of the amount of calcium in the calcium compound to the amount of chlorine in the chlorine-containing plastic is 2 or more in terms of molar ratio. A mixture mixed in a ratio of 10 or less is heated at a temperature of 500° C. or more and 900° C. or less in a non-oxidizing atmosphere to generate a pyrolysis gas and carbides of the chlorine-containing plastic, and the chlorine. a pyrolysis step of reacting chlorine contained in the containing plastic with the calcium compound to produce a chlorine-containing calcium compound;
a gas recovery step of recovering the pyrolysis gas;
By classifying the carbide and the chlorine-containing calcium compound using a sieve smaller than the average particle size of the chlorine-containing plastic and larger than the average particle size of the calcium compound, fine particles and coarse particles are separated. A separation step of separating by a method of separating into
a step of washing the chlorine-containing calcium compound separated in the separation step;
and a step of washing the carbide separated in the separation step with water. 2. The method for treating chlorine-containing plastics according to claim 1, wherein said calcium compound has a particle size smaller than that of said chlorine-containing plastics. 3. The method for treating chlorine-containing plastics according to claim 1, wherein the chlorine-containing plastic has a particle diameter of 1 mm or more and 150 mm or less, and the calcium compound has a median diameter of 1 μm or more and 100 μm or less. The method for treating chlorine-containing plastics according to any one of claims 1 to 3, wherein in the separation step, the carbide and the chlorine-containing calcium compound are separated using a sieve. The method for treating chlorine-containing plastics according to any one of claims 1 to 4, wherein in the thermal decomposition step, the mixture is heated at a temperature of 600°C or higher and 900°C or lower in a non-oxidizing atmosphere. The method for treating chlorine-containing plastics according to any one of claims 1 to 5, wherein the pyrolysis gas recovered in the gas recovery step is used as fuel for the pyrolysis step.

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