JP2004099762A - Method for treating used plastic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating used plastic, whereby in treating the used plastics in a blast furnace in an ironworks, the used plastic can be treated even though it is difficultly granulable or it is large in amount. <P>SOLUTION: The method comprises treating the used plastic with a combination of a blast furnace and a converter. A gas generated in treating the used plastic in the converter is utilized as an industrial fuel; difficultly breakable used plastic is treated with the converter; and the used plastic containing metallic components is treated with the converter. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for treating used plastics, and more particularly to a method for recycling used plastics in steel works.
[0002]
[Prior art]
In recent years, synthetic resins such as plastics have been rapidly increasing as industrial wastes and general wastes, and their disposal has become a major problem. In particular, plastics, which are high-molecular hydrocarbon compounds, generate a large amount of heat during combustion, and when incinerated, damage to the incinerator makes mass treatment difficult, and many of them are dumped in landfills. That is the current situation. However, dumping of plastics and the like is not preferable in terms of environmental measures, and development of a large-scale treatment method is eagerly desired.
[0003]
As a method of effectively utilizing synthetic resins such as plastics, there is known a method of blowing synthetic resins into a furnace such as a blast furnace or a scrap melting furnace for use (for example, see Patent Document 1). In order to blow used plastic into a blast furnace, there is also known a method in which a film-shaped and a solid synthetic resin are separated, a chlorine-containing resin is removed, and then pneumatically supplied to a blast furnace or the like and blown into the furnace. (For example, see Patent Document 2). When synthetic resins such as chlorine-containing polymer resins such as vinyl chloride are blown into a blast furnace or the like as a reducing agent, a chlorine-based gas (hydrogen chloride, chlorine gas, etc.) is generated due to thermal decomposition of the chlorine-containing polymer resin, and If a large amount of chlorine-based corrosive gas is contained in the gas, it causes corrosion problems in the furnace body, gas treatment equipment, and the like. Therefore, the amount of chlorine-containing resin to be treated in a blast furnace is limited. Therefore, the remainder after removing the chlorine-containing resin is used for blowing. The removed chlorine-containing resin can be blown into a blast furnace by separately performing a dechlorination treatment (for example, see Patent Document 3).
[0004]
[Patent Document 1]
JP-B-51-33493
[0005]
[Patent Document 2]
JP-A-9-170009
[0006]
[Patent Document 3]
JP-A-10-60509
[0007]
[Problems to be solved by the invention]
However, when processing used plastic in a blast furnace as described in Patent Documents 1 to 3 above, the used plastic is reduced to a size and shape that can be stably pneumatically transported to be blown into the furnace from tuyeres. It needs to be granulated, which is costly. Further, composite plastics such as FRP (fiber reinforced plastic), which is difficult to crush, and plastics to which metal adheres may cause damage to blades of crushers and the like, so that there is a problem in that granulation is difficult.
[0008]
Therefore, an object of the present invention is to solve such problems of the prior art, and when treating used plastics using a blast furnace in an ironworks, it is possible to treat even used plastics that are difficult to granulate. Another object of the present invention is to provide a used plastic processing method capable of processing a large amount of used plastic.
[0009]
[Means for Solving the Problems]
The features of the present invention for solving such a problem are as follows.
(1) A method for treating used plastic, wherein the used plastic is treated using a blast furnace and a converter together.
(2) The method for treating used plastic according to (1), wherein a gas generated by treating the used plastic in a converter is used as an industrial fuel.
(3) The method for treating used plastic according to (1) or (2), wherein the used plastic that is difficult to crush is treated in a converter.
(4) The method for treating used plastic according to any one of (1) to (3), wherein the used plastic containing a metal component is treated in a converter.
(5) a step of separating the used plastic into a used plastic (A) mainly composed of a film-like plastic and another used plastic (B), and a chlorine-containing plastic from the used plastic (A). Separating and removing the used plastic (A) after the step, and charging the used plastic (A) into a converter; crushing the used plastic (B); and using the used plastic (B) after the step. ) To the blast furnace and blowing it into the furnace.
(6) The method for treating used plastic according to any one of (1) to (5), wherein a part of the used plastic is treated in a coke oven and / or a gasification melting furnace.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is an embodiment of the present invention, and shows an overall view of a used plastic processing using a blast furnace and a converter in combination.
[0011]
The used plastic 1 received at the steel mill is separated into a solid plastic 3, a film-based plastic 4, and foreign substances 12 (metal pieces, wood chips, etc.) in a separation step 2. The solid plastic 3 is crushed in the coarse crushing step 5 and, if necessary, the chlorine-containing resin is removed in the chlorine-containing plastic removing step 6 and then crushed and granulated to a predetermined particle size in the crushing step 7. The film-based plastic 4 is crushed in the coarse crushing step 8, and after removing the chlorine-containing resin in the chlorine-containing plastic removing step 9, it is granulated to a predetermined particle size in the granulating step 10 and granulated. The used plastic granulated to a predetermined particle size in the pulverizing step 7 and the granulating step 10 is blown into a blast furnace 11 from a tuyere and treated as a reducing agent.
[0012]
The foreign matter 12 separated in the separation step 2 is mainly composed of small pieces such as metal pieces, wood chips, metal-attached plastics, etc. Among them, a small amount of metal pieces, metal-attached plastics 13 and the like are used by other thermoplastics. It is molded together with the plastic into a molded article in a molding step 17, and is included in the molded article and processed in the converter 14. A part of the used plastic from which the chlorine-containing plastic such as vinyl chloride has been removed in the chlorine-containing plastic removing steps 6 and 9 is also formed into a molded body in the molding step 17 and processed in the converter 14. In addition, a part of the solid plastic processed in the pulverizing step 7 and a part of the film-based plastic granulated in the granulating step 10 can be formed in the forming step 17 and processed in the converter 14. In particular, it is desirable to use a converter to remove the used plastic that has been removed by sieving, etc., after crushing and granulation, and that is not suitable for blowing into a blast furnace. If the used plastic received at the steel mill is a difficult-to-pulverize used plastic 15 such as a plastic not suitable for pulverization to a size suitable for blowing into a blast furnace, it may be used together with other thermoplastic used plastics. It is formed in a forming step 17, and is contained in a formed body and processed in the converter 14. At the time of processing in a converter, it is desirable to mold with a specific gravity adjusting substance as described below so as to facilitate charging, and then process as a molded body. The generated gas generated in the converter 14 is recovered and used as industrial gas.
[0013]
It is preferable to use a converter to process used plastics that are not suitable for crushing to a size suitable for blowing into a blast furnace, such as metal-attached plastics 13 and used plastics 15 mainly composed of difficult-to-crush plastics. Used plastic from which chlorine-containing plastics such as vinyl chloride has been removed in the plastic-containing plastic removal steps 6 and 9, solid plastic processed in the pulverization step 7, and film-based plastic granulated in the granulation step 10 are processed in both a blast furnace and a converter. It is possible, and the allocation will be determined appropriately according to the status of receiving and processing of used plastic. Considering the costs of the pulverizing step 7 and the granulating step 10, it can be used for processing in a converter at the stage of used plastic from which chlorine-containing plastics such as PVC have been removed by the chlorine-containing plastic removing steps 6 and 9. desirable.
[0014]
The used plastics to be received are mixed with foreign substances, such as general waste plastics discharged from homes, are not separated in the form of solids, films, etc., and are in a mixed state of multiple types of plastics. In some cases, chlorine-containing plastics such as those described above are also mixed. The reason why the separation step 2 is provided is that it is preferable to use different pretreatment steps depending on whether the used plastic to be treated is solid or film-shaped. The solid plastic can be granulated to a predetermined particle size by crushing and grinding. On the other hand, since film-based plastics do not become granules suitable for pneumatic transport by blowing into a blast furnace even if they are pulverized in the same manner as solid plastics, it is preferable that the plastics be semi-molten or melt-solidified, then cut or crushed, granulated and processed. Therefore, it is efficient to separate the received plastic into solid plastic and film-based plastic and treat them separately. In this separation step, for example, a heavy-weight solid plastic and a light-weight film-based plastic can be separated using an oscillating sorter. In the case of using an oscillating sorter, foreign substances can be simultaneously separated as small-sized objects. It is desirable that the foreign matters 12 such as metal pieces, wood chips and metal-adhered plastics be separated also for protecting the equipment of the crusher and the crusher.
[0015]
Chlorine-containing plastics 16 such as PVC, which are not suitable for blowing treatment in a blast furnace and treatment in a converter, are mainly made of a chlorine-containing polymer resin material such as vinyl chloride or vinylidene chloride. Used plastic containing chlorine in excess of the processable concentration. For example, it is appropriately set such that the chlorine content is 1 mass% or more. The chlorine-containing plastic 16 is separately subjected to a dechlorination treatment and is treated in a blast furnace and / or a converter, or is subjected to, for example, a landfill treatment as a residue. Further, the metal-adhered plastic is separated from the separated foreign matter 12 by using magnetic separation or the like. Spent plastics containing metal components can be processed in a converter, but foreign materials other than metals are separately disposed of. Even in the case where metal-contaminated plastics are mixed with foreign substances of simple metals, when processing in a converter, the molded product can be molded together with other used plastics up to the shape and size that can be put into the converter. If there is, there is no particular problem.
[0016]
As described above, the present invention is characterized in that used plastic is treated by using both a blast furnace and a converter. Further, it is preferable to use gas generated by treating used plastic in a converter as an industrial fuel.
[0017]
By using a blast furnace and a converter together, the amount of used plastics to be processed in an ironworks increases, and even a used plastic that is difficult to granulate can be processed in a converter. Recycling used plastic as a blast furnace reducing agent and treating the used plastic in a converter increases the amount of gas generated in the converter. The energy utilization rate of plastic is greatly improved.
[0018]
In the present invention, it is preferable to treat a used plastic which is difficult to crush by a converter. Blow-in treatment in a blast furnace when the plastic to be received is mainly difficult-to-process plastic such as FRP (fiber reinforced plastic) which is difficult to crush, or when it is difficult to separate solid plastic from film-like plastic. If the granulation treatment is difficult, these plastics are preferably treated in a converter. Since the processing in the converter is basically the charging to the molten metal surface, even in the case of manufacturing a molded product, it is easier than the granulation processing for blowing into a blast furnace, and the cost is low. is there.
[0019]
In addition, when used plastics containing metal components are crushed to a size suitable for blowing into a blast furnace, blades of a crusher or the like may be damaged, and crushing is difficult. Is preferred. When a used plastic containing a metal component is treated in a converter, it can be recovered as a metal component depending on the type of metal, and the metal component can be used effectively.
[0020]
In addition, the used plastics are separated into solid used plastics and film used plastics, and chlorine-containing plastics are removed from each.The solid used plastics are mainly used in the blast furnace and the film used plastics are used in the converter. It is preferable to form and treat a molded body as a main body because the cost of the granulation 10 can be reduced. That is, a method for treating used plastic in a blast furnace and a converter, wherein the used plastic is converted into a used plastic (A) mainly composed of a film-like plastic and another used plastic (B). Separating the used plastic (A), separating and removing the chlorine-containing plastic from the used plastic (A), forming the used plastic (A) after the step, and charging the same into a converter; ), A step of separating and removing the chlorine-containing plastic after the crushing or during a plurality of crushing steps, and pneumatically feeding the crushed used plastic (B) to a blast furnace, It is preferable to use a method for treating used plastics, characterized by comprising a step of blowing into plastic. If it is a normal used plastic, the used plastic (solid plastic) other than the film-shaped plastic hardly contains a chlorine-containing plastic resin. Therefore, in the processing step of the used plastic (B), the chlorine-containing plastic is used. Can be omitted. Since the cost of manufacturing a molded article of used plastic to be put into a converter is lower than the cost of granulating granular plastic for blowing into a blast furnace, the above-described processing method capable of omitting the step of granulation 10 is costly. It is effective for reduction.
[0021]
In the chlorine-containing plastic removing steps 6 and 9, it is preferable to remove the chlorine-containing plastic by specific gravity separation. Chlorine-containing plastic materials such as vinyl chloride and vinylidene chloride, which are chlorine-containing plastics, have a higher specific gravity than other synthetic resins (specific gravity of polyethylene: 0.91 to 0.96, specific gravity of polypropylene: 0.89). (About 0.16 to about 0.91; specific gravity of vinyl chloride: about 1.16 to 1.55). Usually, a specific gravity separation method using a liquid such as water or a centrifugal separation method is used as a separation device for specific gravity separation. In order to perform the specific gravity separation, it is preferable to perform the separation after crushing the used plastic to about 8 mm to 20 mm.
[0022]
As a method of granulating a film-shaped plastic, a method of obtaining a granular material by completely melting a used plastic, extruding it into a rod shape by an extruder, and cutting it into granules, a method of cutting or crushing used plastics. The plastic is semi-molten by heating or frictional heat generated by the cutting or crushing, and the semi-molten synthetic resin material is rapidly cooled to be shrunk and solidified. At this time, the plastic resin is shrunk and solidified into granules or the shrunk and solidified synthetic resin material is crushed. A method of obtaining granular material by processing, cutting or crushing with a high-speed rotating rotary blade, semi-molten used plastic by frictional heat due to the cutting or crushing, and then spraying the semi-molten used plastic with water The material is quenched and solidified by quenching, etc. Reduction and simultaneously pulverized by the rotary blade, it is possible to use any method of a method such as to obtain granules.
[0023]
In the treatment of used plastics in a converter, it is preferable to form a molded body having a specific gravity of a certain level or more from the used plastics and put it into the converter. By putting used plastic into the converter, the calorific value of the converter gas can be increased and the converter gas amount can be increased, and heat is added efficiently without contaminating the molten metal. It can also be used as a steelmaking method. When the used plastic is introduced from the top of the converter, it is preferable to manufacture a compact having a specific gravity of a certain value or more so as not to be blown off by rising gas generated from the converter. And the iron ore and the used plastic are mixed and kneaded, and the mass of each piece is about 20 to 150 g, and the apparent density is 1100 to 2500 kg / m. ³ Manufacture compacts such as cylinders and prisms. Metal oxides such as Mn ore and iron ore can be recovered as metal components by reduction as well as density adjustment. As reducing agents for metal oxides, carbon and hydrogen gases generated from plastics work effectively. The used plastic molded body to be charged into the converter can be charged even if a small amount of metal is adhered, as long as it hardly affects the components of the molten metal to be processed in the converter. If the metal component is a steel component such as iron or manganese, it can be used positively. When the used plastic is effectively supplied to the melt surface of the converter, it can be effectively used as a heat source, and when Mn ore or iron ore is used as the specific gravity adjusting material, the heat required for the reduction of ore by the plastic is obtained. Can be given. Also, the reduction yield is improved.
[0024]
Generally, in order to granulate a used plastic into a shape suitable for blowing into a blast furnace, it is necessary to perform a plurality of crushing treatments, for example, to crush the particle size from several mm to about several tens mm. However, difficult-to-process plastics, metal-containing plastics, and the like impose a large load on the crusher, lower the productivity, and sometimes damage the blades of the crusher. On the other hand, when processing used plastics in a converter, the size of the molded body to be charged also needs to be a certain size (for example, several tens of mm). The problem is alleviated because it is not necessary to grind to the extent. For this reason, it is preferable that a used plastic containing an unsuitable foreign substance when pulverizing is processed in a converter. Therefore, by using a blast furnace and a converter together, especially when the used plastic is mainly a difficult-to-process plastic such as FRP (fiber reinforced plastic) or a metal-containing plastic, which is difficult to crush, The amount of used plastic to be processed can be increased.
[0025]
In addition to the treatment in the blast furnace and the converter, it is preferable to treat a part of the used plastic in a coke oven and / or a gasification melting furnace. When a coke oven and / or a gasification melting furnace are used, the chlorine-containing resin can be treated, and by using them together, it is possible to further increase the throughput of the used plastic. However, in a coke oven, there is a problem that the coke strength is reduced, and there is a limit to the amount of used plastic added to the coke oven. On the other hand, when a gasification melting furnace is used, the processing amount of the chlorine-containing resin is not particularly limited, and foreign substances and the like can be processed.
[0026]
In addition, some of the used plastics can be processed in other steelworks facilities.
[0027]
As a gasification and melting furnace, for example, a shaft furnace that can efficiently pyrolyze used plastics is used, and coke, limestone, etc. are added as auxiliary materials together with used plastics from the top of the furnace, and from the tuyere of the shaft furnace. The used plastic is thermally decomposed and melted by blowing pure oxygen.
[0028]
A gasification and melting furnace is a plant that generates a pyrolysis gas from waste using a kiln (rotary kiln) or a fluidized-bed furnace, and melts pyrolysis residues such as incineration ash using the heat of the pyrolysis gas. It is preferable to use a shaft furnace, which is also called a coke bed type melting furnace, having a structure in which the pyrolysis furnace and the melting furnace are integrated, as the gasification melting furnace. Maintaining the temperature inside the furnace top of the shaft furnace at a high temperature of 800 ° C to 1100 ° C to sufficiently gasify impurities in the pyrolysis gas such as tar and char in the generated gas generated in the shaft furnace. Is preferred. Immediately high-temperature dry-distilling the used used plastic to gasify tars and the like enables recovery of flammable gas with higher calories than before.
[0029]
As described above, when it is difficult to maintain the entire temperature inside the furnace top of the shaft furnace at a high temperature of 800 ° C. to 1100 ° C., it is desirable to use a gasification and melting furnace provided with a reforming furnace. In addition to the shaft furnace, when using a gasification and melting furnace provided with a reforming furnace that easily adjusts the ambient temperature for gasifying tar and / or char generated from spent plastic by pyrolysis uniformly, By gasifying tar and / or char generated by thermal decomposition in the reforming furnace, impurities in the pyrolysis gas can be efficiently gasified. The gasification and melting furnace further includes gas cooling equipment for cooling the gas reformed in the reforming furnace using water, water treatment equipment for treating gas cooling water, and desulfurization equipment for desulfurizing the cooled gas. It is preferable to provide The desulfurized gas is stored in a gas holder and recycled.
[0030]
The reforming furnace may be, for example, one having a substantially cylindrical shape as a whole and having a refractory adhered to the inner periphery thereof. The diameter of the reforming furnace is smaller than the diameter of the furnace top of the shaft furnace. For example, while the diameter of the furnace top is about 9 m, the diameter of the reforming furnace is set to, for example, 2 to 3 m. It is desirable to provide a plurality of blowing ports in the circumferential direction for blowing pure oxygen and water into the reforming furnace where the diameter of the lower portion of the reforming furnace is reduced. By blowing pure oxygen and water from the inlet, the ambient temperature inside the reforming furnace can be set to 1000 to 1200 ° C.
[0031]
When a shaft furnace is used as the gasification and melting furnace, the upper part of the deposited layer of used plastic deposited inside the shaft furnace is a fluidized bed in a fluidized state without using a reforming furnace, and has an oxygen concentration of 90% or more. By controlling the temperature of the fluidized bed from about 800 ° C. to about 1000 ° C. by blowing pure oxygen into a shaft furnace, it is possible to suppress the generation of tar and / or char during gasification of used plastic. it can.
[0032]
【Example】
(Example 1) Used plastic was received at an ironworks, and used plastic processing was performed using a blast furnace and a converter. The received used plastic was in a state where solids and films were not separated, and chlorine-containing plastics such as PVC were mixed. Separately from this, plastic containing chlorine and containing no FRP (used plastic 15 mainly composed of difficult-to-crush plastic), which is industrial waste discharged from factories, was also treated.
[0033]
The used plastic processing described above was performed according to the same processing flow as in FIG. In order to remove foreign matter from the used plastic 1, the used plastic is separated into heavy (solid plastic), small-diameter (metal pieces, wood chips, etc.) and lightweight (film plastic) using a rocking sorter. did. Since the solid plastic 3 is mainly a plastic containing no chlorine, after the coarse crushing 3, the chlorine-containing plastic is not separated 6 but crushed 7 by a crusher to about 8 mm, and the tuyere is used as a reducing agent for the blast furnace 11. I blew it from In order to separate and remove the chlorine-containing plastic, the separated film-based spent plastic 4 was separated into a weight portion having a specific gravity of 1 or more and a lightweight portion having a specific gravity of 1 or less using a centrifugal-type specific gravity separator. The lightweight portion was granulated 10 using a granulator, and was blown from a tuyere as a reducing agent for the blast furnace 11. Since most of the weight component was chlorine-containing plastic 16, it was separately treated in a gasification melting furnace. The remaining part of the small-diameter foreign matter 12 excluding the metal-adhered plastic 13 was also processed in a gasification melting furnace. Using a part of a coarsely crushed solid plastic, a part of a film-based plastic from which chlorine-containing plastic is separated and removed, a chlorine-free plastic 15 mainly composed of FRP, and a metal-attached plastic 13 Then, a molded body for charging the converter was formed together with the specific gravity adjusting material. As a specific gravity adjusting material, a material obtained by sintering Mn ore to reduce the degree of oxidation of Mn (hereinafter referred to as a Mn ore sintered powder) and a used plastic compounded to be 70 mass% of the whole are mixed and kneaded. The weight of one piece is 30 to 40 g, and the apparent density is about 1200 kg / m ³ Was produced. Next, the formed body was supplied from a feeder onto the molten metal during converter blowing. The plastic was effectively supplied to the melt surface and could be effectively used as a heat source, and the plastic could provide the heat required for the reduction of Mn ore.
[0034]
The chlorine content of the used plastic supplied to the blast furnace 11 and the converter 14 was 0.5 mass% or less. The tapping rate of the blast furnace was 10,000 t / day, the unit consumption of waste plastic was 16 kg / t, and there was no change in wind pressure, shaft pressure, etc., and the operation was successful. In addition, the converter was able to process 40 t / day of used plastic. As compared with the case where the used plastic is processed only in the blast furnace, the amount of the used plastic greatly increased, and it was possible to process the metal-attached plastic and the used plastic that was difficult to granulate.
[0035]
(Embodiment 2) The same used plastic as in Embodiment 1 was processed in a blast furnace and a converter in substantially the same manner as in Embodiment 1 by the same processing flow as in FIG. In the present example, most of the separated solid plastic 3 was blown into the blast furnace 11 for processing, and most of the separated film plastic was processed in the converter. A chlorine-free plastic 15 mainly composed of FRP and a metal-adhered plastic 13 were treated in a converter in the same manner as in Example 1. By processing most of the film-based plastics in the converter, the granulation step for blowing in the blast furnace could be omitted, thereby reducing the cost of pretreatment.
[0036]
【The invention's effect】
As described above, according to the present invention, when treating used plastics in a steel mill using a blast furnace, it is possible to treat even used plastics that are difficult to granulate, which affects the operation of the blast furnace. A large amount of used plastic can be processed without giving any waste.
[Brief description of the drawings]
FIG. 1 shows an overall view of used plastic processing using a blast furnace and a converter.
[Explanation of symbols]
1: Used plastic,
2: sorting process,
3: solid plastic,
4: Film plastic
5: coarse crushing process,
6: Chlorine-containing plastic removal process,
7: grinding process,
8: coarse crushing process,
9: Chlorine-containing plastic removal process,
10: granulation process,
11: Blast furnace,
12: Foreign matter (metal fragments, wood chips, etc.),
13: Metal-adhered plastic,
14: Converter,
15: Used plastic mainly composed of difficult-to-crush plastics
16: chlorine-containing plastic,
17: Molding process

Claims (6)

A method for treating used plastic, wherein the used plastic is treated using a blast furnace and a converter together. The method for treating used plastic according to claim 1, wherein a gas generated by treating used plastic in a converter is used as an industrial fuel. The used plastic processing method according to claim 1 or 2, wherein the used plastic that is difficult to crush is processed in a converter. The method for treating used plastic according to any one of claims 1 to 3, wherein the used plastic containing a metal component is treated in a converter. A step of separating the used plastic into a used plastic (A) mainly composed of a film plastic and another used plastic (B), and separating and removing the chlorine-containing plastic from the used plastic (A). A process and a step of molding the used plastic (A) after the step and charging the same into a converter; a step of crushing the used plastic (B) and a step of converting the used plastic (B) after the step into a blast furnace. The method for treating used plastic according to any one of claims 1 to 4, comprising a step of pneumatically feeding and blowing into a furnace. The method for treating used plastic according to any one of claims 1 to 5, wherein a part of the used plastic is treated in a coke oven and / or a gasification melting furnace.

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