JP2019123771A - Chlorine-containing plastic treatment method - Google Patents

Abstract

To provide a chlorine-containing plastic treatment method enabling chlorine-containing plastic to be continuously treated over a long period of time, enabling chlorine to be fixed at high efficiency, and hardly generating dioxins.SOLUTION: The chlorine-containing plastic treatment method is provided that comprises: a thermal decomposition step in which a mixture is heated in non-oxidative atmosphere at a temperature of 500 to 900°C to generate a pyrolysis gas of chlorine-containing plastic and carbide, and chlorine contained in the chlorine-containing plastic is reacted with the calcium compound to generate a chlorine-containing calcium compound, wherein the mixture is obtained by mixing at least one kind of calcium compound selected from a group consisting of calcium hydroxide, calcium carbonate, and calcium oxide with the chlorine-containing plastic at such a mixing ratio that calcium amount of the calcium compound to chlorine amount of the chlorine-containing plastic falls within the range of 2 to 10 by molar ratio; and a gas recovery step of recovering the pyrolysis gas.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of 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 of treating waste containing such chlorine-containing plastics. However, from the viewpoint of resource recycling, it has also been studied to recover the organic component in chlorine-containing plastic and use it as a substitute for fuel.

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

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

  In Patent Document 3, crushed wastes of plastics containing chlorine and solid alkali metal compounds or alkaline earth metal compounds are introduced into a reaction vessel, and superheated steam at 210 to 350 ° C. is used. It is supplied to / discharged from the reaction vessel, and hydrogen chloride generated by decomposition of the plastic in the waste in the reaction vessel is fixed to the solid phase by capturing it with an alkali metal compound or alkaline earth metal compound, and remains in the reaction vessel. Discloses a method for discharging the solid content out of the reaction vessel as a regenerated solid fuel. In the method disclosed in this patent document 3, after breaking up the solid content drawn out of the reaction vessel, classification is performed using a sieve, and only fine chlorine-containing solid particles having passed through a sieve by classification are used. It is washing with water.

Patent No. 6022745 Patent No. 5732278 gazette Patent No. 5845124 gazette

  In the method of treating a chlorine-containing plastic described in Patent Documents 1 to 3, the chlorine-containing plastic is treated at a relatively low temperature. Therefore, the volatilization of the organic component contained in the plastic can be reduced, and there is an advantage that relatively large amounts of carbides with high calorific value can be recovered. However, since thermoplastic plastics such as polyvinyl chloride generally soften and melt at 90 to 330 ° C., the softened and melted chlorine-containing plastics are fused to form lumps in the temperature range described in Patent Documents 1 to 3 There is a problem that it may form an object, which may block the outlet of the reaction vessel, making it difficult to treat the chlorine-containing plastic continuously for a long period of time. In addition, when the heating temperature of the chlorine-containing plastic is low, thermal decomposition does not proceed, and there is also a problem that organic chlorine remains. In addition, since heavy thermal decomposition products (tars) may also block the outlet of the reaction vessel, it is important to suppress the formation of tars. Furthermore, since the carbonized product at low temperatures contains heavy thermal decomposition products such as tar, when the carbonized product is washed with water, the amount of organic matter in the waste water is increased, and the waste water treatment becomes complicated. Furthermore, in the processing 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-described circumstances, and an object thereof is to be able to treat chlorine-containing plastics continuously over a long period of time, and to generate hydrogen chloride generated by thermal decomposition of chlorine-containing plastics. It is an object of the present invention to provide a method for treating chlorine-containing plastics that can be fixed with high efficiency and is less likely to generate dioxins.

  In order to solve the above problems, the method for treating a chlorine-containing plastic of the present invention comprises, as a chlorine-containing plastic, at least one calcium compound selected from the group consisting of calcium hydroxide, calcium carbonate and calcium oxide; A mixture in which the ratio of the calcium content of the calcium compound to the chlorine content of the contained plastic is in the range of 2 to 10 in molar ratio is heated at a temperature of 500 ° C. to 900 ° C. in a nonoxidizing atmosphere. A thermal decomposition step of forming a thermal decomposition gas and a carbide of the chlorine-containing plastic and reacting chlorine contained in the chlorine-containing plastic with the calcium compound to form a chlorine-containing calcium compound; And a gas recovery step of recovering the gas.

  According to the method for treating a chlorine-containing plastic of the present invention having such a constitution, in the thermal decomposition step, it is 500 ° C. in a non-oxidizing atmosphere as a mixture in which the chlorine-containing plastic and the calcium compound are mixed in the above ratio Since heating is performed at a relatively high temperature of 900 ° C. or less, it is difficult to form a block or tar in which chlorine-containing plastics are fused to each other. For this reason, chlorine-containing plastics can be treated continuously over a long period of time. Further, hydrogen chloride (HCl) generated by thermal decomposition of the chlorine-containing plastic can be efficiently fixed to the calcium compound, and dioxins are less likely to be generated. Furthermore, although the pyrolysis gas of chlorine-containing plastics is recovered in the gas recovery step, the chlorine concentration in the pyrolysis gas is low, so the burden on equipment corrosion and exhaust gas treatment is extremely low when used as a fuel alternative gas . Furthermore, organic substances contained in the pyrolysis gas can be used as fuel.

Here, in the method of treating a chlorine-containing plastic of the present invention, it is preferable to further include a separation step of separating the carbide and the chlorine-containing calcium compound.
In this case, the separated carbide 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 as a calcium compound for fixing chlorine after desalting.

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

It is a flow figure showing the processing method of the chlorine content plastic concerning one embodiment of the present invention. It is sectional drawing which shows the structure of the heat processing apparatus which can be used advantageously in the processing method of the chlorine containing plastics which concern on one Embodiment of this invention.

  Hereinafter, a method of treating a chlorine-containing plastic according to an embodiment of the present invention will be described with reference to the attached drawings.

FIG. 1 is a flow chart showing a method of treating a chlorine-containing plastic according to an embodiment of the present invention.
In the processing method of the chlorine-containing plastic of the present embodiment, as shown in FIG. 1, a mixing step S01 for mixing the chlorine-containing plastic and the calcium compound, and a thermal decomposition step S02 for heating the mixture obtained in the mixing step S01. The gas recovery step S03 for recovering pyrolysis gas of chlorine-containing plastic, the separation step S04 for separating 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 washing step S05 for washing the material and a coarse particle washing step S06 for washing the coarse particles separated in the separation step are provided.

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

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

  The calcium compound contains at least one selected from the group consisting of calcium hydroxide, calcium carbonate and calcium oxide. The calcium compound promotes the thermal decomposition of the chlorine-containing plastic in the thermal decomposition step S02 to reduce the thermal decomposition product, and the hydrogen chloride (HCl) produced by the thermal decomposition of the chlorine-containing plastic is calcium chloride or chloride. It has the action of fixing it 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 a calcium compound. Incineration fly ash is fine particles generated by neutralizing acid gas containing chlorine gas generated by incineration treatment of municipal waste with a calcium compound (in particular, calcium hydroxide, calcium oxide). Dust is fine particles produced by neutralizing acid gas containing chlorine gas generated by incineration treatment of industrial waste with a calcium compound. Although these contain chlorine, since they contain a large amount of chlorine and unbound calcium, they can be used as calcium compounds. It is more effective to remove chlorine in advance by washing with water. One of these may be used alone, or two or more may be used in combination. For the same reason, it is also possible to utilize chlorine bypass dust by-produced in a cement plant or a dried product of neutralized sludge from industrial wastewater.

  The calcium compound preferably has a particle size smaller than that of the chlorine-containing plastic. When the particle size of the calcium compound is small, the solid content is easily separated 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 is too small, the amount of dust generated in the thermal decomposition step S02 may be increased. There is a risk of scattering in the generated pyrolysis gas. For this reason, 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 calcium amount of the calcium compound to the chlorine amount of the chlorine-containing plastic (Ca / Cl ratio) is in the range of 2 to 10 in molar ratio. If the Ca / Cl ratio is less than 2, the amount of hydrogen chloride fixed to the calcium compound may be reduced in the thermal decomposition step S02, and hydrogen chloride may be easily mixed in the thermal decomposition gas. Further, in the thermal decomposition step S02, there is a possibility that heavy thermal decomposition products (tars) are likely to be generated without promoting thermal decomposition of the chlorine-containing plastic. On the other hand, when the Ca / Cl ratio exceeds 10, not only the above-mentioned effects are saturated, but the amount of the chlorine-containing plastic to be treated is relatively reduced, and the treatment efficiency of the chlorine-containing plastic is lowered. The Ca / Cl ratio is preferably in the range of 3 or more and 10 or less.

(Thermal decomposition step S02)
In the thermal decomposition step S02, the mixture obtained in the mixing step S01 is heated to form a thermal decomposition gas and a carbide of a chlorine-containing plastic, and chlorine contained in the chlorine-containing plastic is reacted with a calcium compound to produce chlorine. The contained calcium compound is formed.

  The heating of the mixture takes place in a non-oxidizing atmosphere. The non-oxidizing atmosphere is an atmosphere in which the chlorine-containing plastic is not oxidized (burned). The non-oxidizing atmosphere is preferably an atmosphere in which the oxygen concentration is adjusted to 1% by volume or less. Specifically, an atmosphere of an inert gas such as nitrogen, water vapor, carbon dioxide and argon, or a negative pressure atmosphere can be mentioned.

  The heating temperature is a temperature of 500 ° C. or more and 900 ° C. or less. If the heating temperature is less than 500 ° C., a lump in which chlorine-containing plastics are fused may be formed. On the other hand, when the heating temperature exceeds 900 ° C., the chlorine-containing calcium compound is thermally decomposed to easily mix hydrogen chloride gas into the thermal decomposition gas.

  The heating time varies depending on the heating temperature, the chlorine content of the chlorine-containing plastic, the mixing ratio of the chlorine-containing plastic and the calcium compound in the mixture, etc., but generally within the range of 15 minutes to 120 minutes, preferably 20 Within the range of minutes to 60 minutes.

(Gas recovery process S03)
In the gas recovery step S03, the pyrolysis gas of the chlorine-containing plastic is recovered. The pyrolysis gas usually comprises combustibles such as hydrogen, carbon monoxide, low molecular weight hydrocarbon compounds. Examples of hydrocarbon compounds include methane, ethane, ethylene, propane, propene, butane, butene and the like. Pyrolysis gas containing such combustible substances can be used as fuel. For example, the pyrolysis gas can be used as a fuel of the heat treatment apparatus 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 a chlorine-containing plastic according to an embodiment of the present invention.
As shown in FIG. 2, the heat treatment apparatus 10 is an externally heated rotary kiln having an inner cylinder 20 and an outer cylinder 30 for housing the inner cylinder 20.

  The inner cylinder 20 is provided with a mixture supply port 21 at one end, and an extraction port 22 of solids (carbide and chlorine-containing calcium compound) generated 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 the side. Further, the inner cylinder 20 is provided with an inner cylinder rotation device 24 for rotating the inner cylinder 20 at both ends.

  The outer cylinder 30 heats the inner cylinder 20 by burning the thermal decomposition gas taken out 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 flue 32 for discharging the combustion gas generated by the combustion of the pyrolysis gas to the outside.

In the heat treatment apparatus 10, the mixture supplied from the supply port 21 of the mixture is heated while being stirred by the rotation of the inner cylinder 20, thereby generating a pyrolysis gas, a carbide and a calcium compound containing chlorine. The pyrolysis gas is taken out to the outer cylinder 30 through the pyrolysis gas outlet 23.
The solid content (carbide and chlorine-containing calcium compound) is taken out through the solid content outlet 22. On the other hand, the thermal decomposition gas taken out to the outer cylinder 30 is burned to generate a combustion gas 25. The combustion gas 25 is extracted to the outside through the exhaust port 32. The combustion gas 25 extracted to the outside 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 apparatus 10 may be provided 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, the proportion of the calcium compound in the mixture can be increased to improve the chlorine fixation efficiency.

(Separation process S04)
In the separation step S04, the solid content (mixture of carbide and chlorine-containing calcium compound) generated in the thermal decomposition step S02 is separated into fine particles and coarse particles. Specifically, fine particles and coarse particles are separated by classification 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. By so doing, the fine particles can be separated so as to be relatively rich in chlorine-containing calcium compounds, and the coarse particles can be relatively rich in carbides.

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

  The washed fine particles contain a large amount of calcium carbonate or calcium hydroxide. For this reason, the fine particles after washing can be used as a cement material substitute. In addition, it can be reused as a calcium compound for fixing chlorine.

(Coarse-grain cleaning step S06)
In the coarse particle washing step S06, the coarse particles separated in the separation step S04 are washed with water. By this water washing, soluble salts such as calcium chloride in the coarse particles are dissolved and removed. As the method of water washing, the same method as the method of water washing of fine particles can be used. The washed coarse particles can be dewatered using a pressure filtration device, a centrifugal separator, a vacuum filtration device and vibrational dewatering. In addition, when washing of the coarse particles can not be efficiently performed, the coarse particles may be previously crushed and washed to improve the washing efficiency.

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

  According to the method for treating a chlorine-containing plastic according to the present embodiment having the above-described configuration, the mixture containing the chlorine-containing plastic obtained in the mixing step S01 and the calcium compound in a predetermined amount ratio is subjected to the thermal decomposition step In S02, since heating is performed at a relatively high temperature of 500 ° C. to 900 ° C. in a non-oxidizing atmosphere, it is difficult to form a block or tar in which chlorine-containing plastics are fused. For this reason, chlorine-containing plastics can be treated continuously over a long period of time. In addition, hydrogen chloride generated by thermal decomposition of a chlorine-containing plastic can be efficiently fixed to a calcium compound, and dioxins are less likely to be generated.

  Moreover, in the processing method of the chlorine-containing plastic of this embodiment, the separation step S04 is further performed to separate the solid content (carbide and chlorine-containing calcium compound) generated in the thermal decomposition step S02 into fine particles and coarse particles. Since the fine particles contain a relatively large amount of calcium compounds containing chlorine, after being washed in the fine particle washing step S05, they should be reused as cement material substitutes or calcium compounds for fixing chlorine. it can. In addition, since the coarse particles contain a relatively large amount of carbides, after being cleaned in the coarse particle cleaning step S06, the coarse particles can be used as a fuel substitute for a rotary kiln for cement production.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.
For example, in the present embodiment, the pyrolysis gas of chlorine-containing plastic is used as the fuel of the heat treatment apparatus used in the pyrolysis step S02, but is not limited thereto. For example, pyrolysis gas can be used as an alternative fuel for rotary kilns for cement production.

  In the present embodiment, the chlorine-containing calcium compound and the carbide contained in the solid content in the separation step S04 are separated as fine particles and coarse particles using a sieve, but the present invention is not limited thereto. . For example, specific gravity selection may be performed wet or dry. In this case, the low specific gravity substance having a low specific gravity contains a relatively large amount of carbides, and the high specific gravity substance having a high specific gravity contains a relatively large amount of chlorine-containing calcium compound. A highly hydrophobic carbide may be attached to bubbles and float-sorted. Alternatively, highly conductive carbides may be sorted 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 thereto. There is nothing to do. For example, after washing the solid content, the solid content may be separated into fine particles and coarse particles.

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

  Furthermore, in the present embodiment, the coarse particles are washed with water in the coarse particle washing step S06 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 rotary kilns for cement production without cleaning.

  Below, the effect of this invention is demonstrated by an Example.

[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. A mixture was prepared by mixing calcium hydroxide (purity: 95% by mass or more, median diameter: 20 μm) as a calcium compound to this PVC so that the Ca / Cl ratio was 2 in molar ratio. 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 reduced 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 exhausted from the electric furnace was discharged to the outside after passing through the cold trap.

(Chlorine fixation rate)
The inorganic chlorine content in the recovered solid content was measured, and the chlorine fixation rate was calculated from the total chlorine content in the mixture measured in advance from the following equation. The results are shown in Table 1. The chlorine content was measured by the following method.
Chlorine fixation rate = (Inorganic chlorine content in solid content / Total chlorine content in mixture) × 100

(Method of measuring chlorine content)
The sample was subjected to ultrasonic leaching with an alkaline eluate and then filtered to recover the filtrate and leaching residue. The amount of chlorine in the obtained filtrate was measured by ion chromatography, and the content of inorganic chlorine in the sample was calculated. In addition, after leaching residue is dried with a vacuum dryer, organic chlorine content 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 the generated gas was absorbed into water. The amount of chlorine in the obtained solution was measured by an ion chromatograph, and the content of organic chlorine in the sample was calculated.
The total amount of the inorganic chlorine content and the organic chlorine content obtained by the above method was taken as the total chlorine content in the sample.

(With or without lumps)
The collected solid content was visually observed to confirm the presence or absence of lumps in which carbide grains were connected. The results are shown in Table 1.

(Recovery rate of condensate collected by cold trap)
The weight of the coagulated substance recovered by the cold trap was measured, and the recovery rate of the coagulated substance was calculated from the weight in the mixture measured in advance by the following equation. The results are shown in Table 1.
Recovery rate of aggregates = (1− (weight of aggregates collected by cold trap / weight in mixture)) × 100

[Inventive Examples 2 to 10, Comparative Examples 1 to 5]
The mixture is heat-treated in the same manner as Example 1 of the present invention except that the type of calcium compound, the Ca / Cl ratio and the heating temperature are changed as shown in Table 1 below, and the chlorine fixation rate, lumps The presence or absence and recovery rate of the aggregates collected by the cold trap were evaluated. The results are shown in Table 1.

In Comparative Example 1 in which the Ca / Cl ratio is lower than the range of the present invention and Comparative Example 2 in which the calcium compound is not added, the chlorine immobilization rate decreases, and the recovery rate of the aggregates recovered by the cold trap is high. became. The reason for the decrease in the chlorine immobilization rate is considered to be that the blending amount of the calcium compound in the mixture is too small and the amount of hydrogen chloride immobilized to the calcium compound is reduced. Further, it is considered that the recovery rate of the condensate is high because the thermal decomposition of the chlorine-containing plastic is not promoted and a heavy thermal decomposition product (tar) is formed.
In Comparative Examples 3 and 4 in which the heating temperature was lower than the range of the present invention, the chlorine fixation rate decreased and a lump was formed in the solid content. The reason for the decrease in the chlorine fixation rate is considered to be that the pyrolysis of the chlorine-containing plastic did not proceed, and it remained as organic chlorine. The formation of a lump is considered to be because the heating temperature became too low and the molten chlorine-containing plastics of the chlorine-containing plastic were fused.
In Comparative Example 5 in which the heating temperature was higher than the range of the present invention, the chlorine fixation rate decreased. It is considered that this is because the heating temperature is too high and the chlorine-containing calcium compound is thermally decomposed.

On the other hand, in the invention examples 1 to 10 in which the Ca / Cl ratio and heating temperature are within the range of the present invention, the chlorine fixation rate is high, no lumps are formed in the solid content, and they are further recovered by a cold trap. The recovery rate of the collected aggregates was low.
From the above, according to the invention examples 1 to 10, chlorine-containing plastics can be treated continuously for a long period of time, chlorine can be fixed with high efficiency, and dioxins are hardly generated. It was confirmed that it would be possible to provide a method.

[Inventive Example 11]
The solid content obtained in Inventive Example 1 was washed. For washing, 10 g of solid content and 100 mL of distilled water are mixed to form a slurry, which is shaken for 30 minutes using a shaker, and then the slurry is filtered under reduced pressure to obtain a cake, and the obtained cake is distilled. It was carried out by washing with 100 mL of water. As a result of measuring the total organic carbon concentration (TOC) of the drainage after washing of the solid content (a liquid mixture of the filtrate collected at the reduced pressure filtration of the slurry and the distilled water collected at the water washing of the cake) by a TOC meter, It was 4.5 mg / L.

Comparative Example 6
A solid was washed in the same manner as in Invention Example 11 except that the solid content obtained in Comparative Example 3 was used. It was 785 mg / L as a result of measuring TOC of the liquid after washing | cleaning of solid content.

In the comparative example 6 which wash | cleaned the solid content obtained by the comparative example 3 whose heating temperature is lower than the scope of the present invention, TOC of drainage increased. It is considered that this is 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 Inventive Example 1 whose heating temperature is in the range of the present invention was such that heavy thermal decomposition products such as tar were decomposed. So, the drainage TOC was low.

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

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

  The wash (cake) obtained by washing was dried using a drier at a temperature of 105 ° C. The total chlorine content, calcium content, and calorific value were measured for the washed and dried fine particles and coarse particles obtained as described above. In addition, total chlorine content was measured by the above-mentioned method. The calcium content and the calorific value were measured by the following method. The results are shown in Table 2.

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

(Method of measuring calorific value)
It was measured by an adiabatic bomb calorimeter.

Comparative Example 7
The mixture was heat-treated in the same manner as in Inventive Example 12, except that the solid content collected from the outlet at the rear of the kiln was 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 were measured for the solid content after washing and drying. The results are shown in Table 2.

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

[Inventive Example 13]
The mixture was heat-treated in the same manner as in Inventive Example 1 except that the fine particles obtained in Inventive Example 12 were used as the calcium compound, and the solid content was recovered. The inorganic chlorine content in the recovered solid content was measured, and the chlorine fixation rate was calculated, and as a result, it was 93.1 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.

DESCRIPTION OF SYMBOLS 10 heat processing apparatus 20 inner cylinder 21 supply port of mixture 22 solid content extraction / extraction port 23 thermal decomposition gas extraction port 24 inner cylinder rotation apparatus 25 combustion gas 30 outer cylinder 31 auxiliary burner 32 exhaust smoke port

Claims (2)

In the chlorine-containing plastic, at least one calcium compound selected from the group consisting of calcium hydroxide, calcium carbonate and calcium oxide, and the ratio of the calcium amount of the calcium compound to the chlorine amount of the chlorine-containing plastic is 2 or more in molar ratio The mixture mixed at 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 a carbide of the chlorine-containing plastic, and the chlorine A pyrolysis step of reacting chlorine contained in the contained plastic with the calcium compound to form a chlorine-containing calcium compound;
And D. a gas recovery step of recovering the pyrolysis gas.   The method for treating a chlorine-containing plastic according to claim 1, further comprising a separation step of separating the carbide and the chlorine-containing calcium compound.

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