JP2001303147A - Method for recycling waste plastics as resource - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively recycle waste plastics separated from non-industrial waste or industrial waste, or the like, as a resource by a simple method and to utilize the waste plastics containing chlorine-containing plastics without removing the chlorine. SOLUTION: The waste plastics containing the chlorine-containing plastics and formed into granular state or small pieces is utilized as a reducing agent for non-ferrous metals when the non-ferrous metals containing heavy metals are fused or refined in a blast furnace or a refining furnace. Then, hydrogen chloride produced when the waste plastics is thermally decomposed in the blast furnace or the refining furnace is reacted with the heavy metals contained in the non-ferrous metals and fixed as the heavy metal chlorides.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for effectively recycling waste plastics containing chlorine-containing plastics contained in general wastes or industrial wastes, etc., by simply performing a simple pretreatment. The present invention relates to a method for fixing chlorine, which has been treated as a harmful substance at a high cost, by a simple method, or for effectively utilizing it as a volatile agent for valuable metals contained as impurities.

[0002]

2. Description of the Related Art Waste plastic collected as general waste is collected in a state of being mixed with other waste. The recovered waste plastic itself also contains chlorine-free polyethylene (PE: PolyEthylene), polypropylene (PP: PolyPropylene), polystyrene (PS: Pol)
yStyrene), polyethylene terephthalate (PET: Po
It includes various types such as lyEthylene terephthalate, chlorine-containing polyvinyl chloride (PVC: Poly Vinyl Chloride), and polyvinylidene chloride (PVDC: Poly Vinyl iDene Chloride).

[0003] Most of this waste plastic is either disposed of as non-combustible waste or simply incinerated as combustible waste. Landfill disposal of waste plastic as incombustible waste has been a serious problem due to the shortage of disposal sites, and it is highly likely that landfill treatment using disposal sites will not be possible in the future, which is not preferable in terms of environmental measures. Incineration of waste plastic as combustible waste generates a large amount of heat when it is burned, and incineration damages the incinerator when it is incinerated, making it difficult to process it in large quantities. In waste plastic, chlorine such as PVC or PVDC is contained in waste plastic. Since the plastic containing plastic is contained, it is necessary to take measures to eliminate highly corrosive toxic hydrogen chloride gas generated by thermal decomposition of the chlorine-containing plastic, and there has been a problem that equipment and treatment costs increase. At present, the ratio of waste plastic in waste is extremely low, and the current disposal method has the above-mentioned problems. However, since plastics are produced from petroleum, which is a source of depletion of resources, they have high caloric value and are desired to be recycled.

As one of the recycling methods, there is a method of recycling plastics into plastics of the original material. In this recycling method, it is necessary to separate the plastics for each material. If chlorine-containing plastic is mixed in, it cannot be recycled. The standard for recycling is generally said to be 0.5% by weight or less of chlorine content.
pm or less. At present, no technology has been established for separating plastics that have been mixed according to this standard. Therefore, only when a single plastic (in this case, PP) is used as in a battery case, the waste plastic is recycled into the original plastic product.

[0005] A recycling method using waste plastic as a raw material for a blast furnace has also been proposed. However, chlorine-containing plastics such as PVC and PVDC in waste plastic are thermally decomposed when burned, and are highly corrosive toxic hydrogen chloride gas. In order to recycle as raw material energy for blast furnaces, dechlorination is performed before combustion to prevent the generation of hydrogen chloride gas during combustion, or expensive exhaust gas treatment equipment such as flue gas and boilers It is necessary to use materials and perform dehydrochlorination by exhaust gas treatment. As a pretreatment of a recycling method in which the waste plastic is used as a raw material of a blast furnace, a pretreatment method of recycling the waste plastic by performing dechlorination has been proposed and put into practical use (Japanese Patent Laid-Open No. 10-2).
No. 59272). In this method, before injecting waste plastic into a blast furnace, the waste plastic is heated to a certain temperature while containing chlorine-containing plastic, melted to remove chlorine, and granulated waste plastic is treated as a reducing agent. It is.

[0006]

However, Japanese Patent Application Laid-Open No.
According to the method disclosed in Japanese Patent Publication No. 0-259272, in order to use chlorine as a reducing agent in a blast furnace or the like, it is necessary to perform a heat treatment at a high temperature of about 350 ° C. to remove chlorine from chlorine-containing plastic. It was necessary to remove earth and sand, bottles, cans, and the like accompanying plastic as impurities. An object of the present invention is to provide a method for effectively recycling waste plastic separated from waste such as general waste or industrial waste by a simple method. Another object of the present invention is to provide a method of recycling waste plastics that can utilize waste plastics containing chlorine-containing plastics without removing chlorine.

[0007]

The invention according to claim 1 is
A waste plastic recycling method that uses, as a reducing agent for non-ferrous metals, waste plastics containing chlorine-containing plastics formed into granules or small pieces when melting or refining non-ferrous metals containing heavy metals in a blast furnace or a refining furnace. is there. The invention according to claim 1 uses waste plastic as a heat source by utilizing waste plastic containing chlorine-containing plastic as a reducing agent for non-ferrous metal when melting or refining in a blast furnace or a refining furnace for non-ferrous metal containing heavy metal. And can be effectively used as a reducing agent. Furthermore, resources can be recycled without incurring costs for equipment and pretreatment.

[0008] The invention according to claim 2 is the invention according to claim 1, wherein hydrogen chloride gas generated when waste plastic containing chlorine-containing plastic is thermally decomposed in a blast furnace or a refining furnace is contained in the non-ferrous metal. This is a method for recycling waste plastics that reacts with heavy metals to be immobilized as heavy metal chlorides. According to the second aspect of the invention, the hydrogen chloride gas generated during the thermal decomposition of the chlorine-containing plastic in the furnace reacts with the heavy metal in the non-ferrous metal and is fixed, so that the toxic and corrosive hydrogen chloride gas is harmless. Can be The invention according to claim 3 is the invention according to claim 1, and is a method for recycling waste plastics into granules by crushing, cutting, or granulating.

[0009]

Next, an embodiment of the present invention will be described. The waste plastic of the present invention is contained in waste such as general waste or industrial waste. Waste plastic may contain some earth and sand, bottles, cans and the like. Waste plastics include those that do not contain chlorine and those that contain chlorine. PE, PP, PS, P
ET and the like, and those containing chlorine include PVC, P
VDC and the like.

In the embodiment of the present invention, waste plastic is separated from general waste or industrial waste, and as shown in FIG. 1, waste plastic mixed with chlorine-containing plastic such as PVC or PVDC is crushed by a crusher 10a. Then, the material is crushed, cut or granulated by a cutting machine 10b or a granulator 10c to form granules or small pieces of 10 mm or less. Either crushing, cutting or granulation means is selected depending on the shape (film type, solid type) of the waste plastic. Granular or small piece diameter of waste plastic is 10mm
If it is above, the fluidity and transportability at the time of pneumatic feeding to the furnace 11 of the blast furnace or the refining furnace to be described later are poor, and clogging easily occurs in the pneumatic pipe system. Therefore, it is preferable to process to about 5 to 10 mm. The processed waste plastic is blown as a reducing agent into a smelting furnace for smelting lead and zinc, a copper refining furnace, a furnace containing lead, zinc, cadmium, tin and other heavy metals as impurities. The waste plastic blown into the furnace 11 burns in the furnace 11, and the chlorine-containing plastic contained in the waste plastic undergoes thermal decomposition to generate hydrogen chloride gas. This hydrogen chloride is supplied to the furnace 11 as shown in the equation (1).
It reacts with heavy metals such as lead and zinc present in the metal to generate chlorides (Formula (1) shows a reaction with zinc). Zn + 2HCl → ZnCl ₂ + H ₂ (1)

Therefore, the present invention is characterized in that chlorine-containing plastics are fixed by reacting hydrogen chloride gas generated by thermal decomposition with heavy metals by utilizing the reaction represented by the formula (1). The chloride generated by the reaction formula (1) has a low volatilization temperature, and the blast furnace and the refining furnace are always kept at 1000 ° C. or higher. Therefore, the chloride volatilizes in the furnace 11 and is discharged out of the furnace together with the exhaust gas. . The discharged exhaust gas containing volatile heavy metal chlorides is sent to a dust collector 12 for solid-gas separation,
It is separated into heavy metal chlorides and exhaust gas and recovered respectively. Examples of the dust collecting device 12 include a wet dust removing device and a cyclone. After dissolving the recovered chloride in water,
As shown in the formula (2), it can be easily recovered as a hydroxide by adjusting the pH. ZnCl ₂ + 2NaOH → Zn (OH) ₂ + 2NaCl (2) As described above, a chlorine-containing plastic in waste plastic can be used as a reducing agent for non-ferrous metals simply by performing a simple pretreatment such as crushing without separating and removing the plastic. It is possible to utilize chlorine in chlorine-containing plastics, which has been conventionally difficult to handle and requires high processing cost.

In a lead or zinc blast furnace, it is possible to use chlorine-containing plastic as a reducing agent without separating it by directly blowing waste plastic from a tuyere. In the blast furnace, hydrogen chloride gas is generated. Hydrogen chloride gas reacts with lead and zinc, is fixed as chloride, and is rendered harmless. In furnaces containing heavy metals such as lead and zinc as impurities such as copper refining furnaces, chlorine-containing plastics are used as a reducing agent without separation, and hydrogen chloride gas generated during pyrolysis is combined with heavy metals such as lead and zinc. Reacts and is fixed as chloride,
Since it is detoxified and heavy metal chlorides can be concentrated and recovered in fume ash, impurities can be recycled as heavy metals. Lead chloride (PbCl ₂ ) concentrated in smoke ash is hot water, zinc chloride (ZnCl ₂ ), cadmium chloride (Cd
Cl ₂ ) can be easily separated and recovered by adjusting the pH after dissolving in water. The exhaust gas discharged from the refining furnace passes through a dust collector 12 and a flue gas desulfurization device (not shown), is finally recovered as hydroxide in wastewater treatment, and is returned to the smelting process. Becomes

[0013] Even if a small amount of bottles, cans, earth and sand, etc. are contained in this waste plastic, it can be fixed as slag, which is a by-product when the target metal is produced, if it is burned as a reducing agent as it is. After being discharged outside the furnace, it can be used as a cement raw material.

[0014]

Next, embodiments of the present invention will be described. <Example 1> A PVC pipe having a chlorine content of 52.7% by weight crushed to 10 mm or less was prepared as a waste plastic simulated material. The simulated material was blown from a tuyere of a lead blast furnace at a rate of 5 kg / min for 5 minutes. The tuyere sub-temperature of this lead smelting furnace was 1200 to 1250 ° C. At this time, the blast furnace suction gas amount was 420 Nm ³ / min. The exhaust gas after combustion was discharged from the blast furnace, and the exhaust gas was passed through a cylindrical filter paper to remove dust. Then, the exhaust gas was passed through two absorption bottles filled with pure water, and the concentration of hydrogen chloride gas was measured by ion chromatography. <Comparative Example 1> 1 g of the same simulated material as in Example 1 was burned in a combustion tube while being held at 1200 ° C, which is considered to be the tuyere-medium temperature of a blast furnace, and the entire amount of generated gas was absorbed in an absorption bottle filled with glass wool. After that, pure water was absorbed in an absorption bottle filled with pure water, and the amount of generated hydrogen chloride gas was measured. As a result of sucking off the exhaust gas burning the simulated material, 96.
It was found that 8% had migrated into the gas.

<Comparative Evaluation 1> From the amount of hydrogen chloride gas generated in Comparative Example 1, the amount of hydrogen chloride gas generated in Example 1 was simply calculated from the supply amount of the simulated material supplied into the blast furnace. As a result, 1920 ppm of hydrogen chloride gas was obtained. Although a numerical value indicating that a gas was generated was obtained, a numerical value that was practically not much different from the background concentration of hydrogen chloride gas in the blast furnace exhaust gas of 20 ppm was obtained. From this, it was considered that in Example 1, the hydrogen chloride gas was fixed to lead as lead chloride, and it was confirmed that even if PVC was directly blown into the lead blast furnace, it could be used as a reducing agent. In this example, the test was carried out in a lead blast furnace, but it is clear that similar results can be obtained by a method in which lead and zinc are simultaneously reduced and volatilized.

Example 2 A chlorine content of 52.2% by weight
Was crushed to 10 mm or less to prepare a waste plastic simulated material. This simulated material was blown from a tuyere of a copper refining furnace at a rate of 10 kg / min for 10 minutes. The temperature at the time of reduction was 1200 to 1250 ° C. The purification furnace suction gas amount was 580 Nm ³ / min. The exhaust gas after combustion was discharged from the refining furnace, and the exhaust gas was passed through a cylindrical filter paper to remove dust. Then, the exhaust gas was passed through two absorption bottles filled with pure water, and the concentration of hydrogen chloride gas was measured by ion chromatography. <Comparative Example 2> 1 g of the same simulated material as in Example 2 was burned in a combustion tube while being kept at 1200 ° C, which is considered to be the tuyere reference temperature of the refining furnace, and the entire amount of generated gas was absorbed by filling glass wool. After passing through the bottle, pure water was absorbed in the sealed absorption bottle, and the amount of generated hydrogen chloride gas was measured. As a result of sucking off the exhaust gas burning the simulated material, 95.
It was found that 8% had migrated into the gas.

<Comparative Evaluation 2> As in Comparative Evaluation 1, from the amount of hydrogen chloride gas generated in Comparative Example 2, the amount of hydrogen chloride gas generated in Example 2 was simply calculated from the amount of the simulated material supplied into the refining furnace. Although a value of 275 ppm of hydrogen chloride gas was obtained, the concentration of hydrogen chloride gas in the exhaust gas from the refining furnace was actually 18 ppm. From this, it is considered that in Example 2, the hydrogen chloride gas generated by the thermal decomposition of PVC reacted with heavy metal impurities such as lead and zinc in the blister copper and was fixed as chloride. It has been confirmed that chlorine-containing plastics can be used as a reducing agent even if they are directly blown.

[0018]

As described above, according to the present invention, waste plastics containing chlorine-containing plastics formed into granular or small pieces when melting or refining nonferrous metals including heavy metals in a blast furnace or a refining furnace. By using as a non-ferrous metal reducing agent, waste plastic can be used as a non-ferrous metal reducing agent without separating chlorine-containing plastics such as PVC and PVDC, thereby greatly simplifying processing equipment. It becomes possible and operation costs can be reduced. In addition, hydrogen chloride gas generated when waste plastics containing chlorine-containing plastics are thermally decomposed in blast furnaces or refining furnaces reacts with heavy metals contained in non-ferrous metals and is fixed as heavy metal chlorides. It is possible to positively utilize the chlorine that has been used, to volatilize and remove heavy metals, which are impurities in copper smelting and the like, as chlorides, and to concentrate and recover heavy metals.

[Brief description of the drawings]

FIG. 1 is a diagram showing a recycling method according to the present invention.

Claims (3)

[Claims] 1. A waste plastic using a waste plastic containing a chlorine-containing plastic formed in a granular or small form when a non-ferrous metal containing a heavy metal is melted or refined in a blast furnace or a refining furnace as a reducing agent for the non-ferrous metal. Resource recycling method. 2. The method according to claim 1, wherein hydrogen chloride gas generated when waste plastic containing chlorine-containing plastic is thermally decomposed in a blast furnace or a refining furnace is reacted with heavy metal contained in non-ferrous metal and fixed as heavy metal chloride. The recycling method of the waste plastic described in the above. 3. The method for recycling waste plastic according to claim 1, wherein the waste plastic is granulated by crushing, cutting or granulating.