KR100902713B1 - Fine powder of mixed plastics and process for producing the same - Google Patents

Abstract

A method of producing mixed plastic fine powder includes the steps of preparing a mixed plastic having a chlorine concentration of 2 to 20 mass% by increasing or decreasing at least one plastic selected from the group consisting of a chlorine-containing plastic and a chlorine-free plastic; Stirring the mixed plastics under melting and dechlorinating the chlorine concentration to 0.9 mass% or less; Cooling and solidifying the dechlorinated agitated substance; And grinding the solidified matter. By the application of this method, if the chlorine concentration in the waste plastic is increased within the predetermined chlorine concentration range, stirring and dehydrochlorination of the molten waste plastic are promoted, so that the chlorine concentration is very low and fine waste plastic powder is obtained. Therefore, the plastic discarded in living or industrial activities can be reused as a reducing agent or fuel.

Mixed plastic, waste plastic, chlorine, stirring, melting, cooling, grinding

Description

Fine powder of mixed plastics and its manufacturing method {FINE POWDER OF MIXED PLASTICS AND PROCESS FOR PRODUCING THE SAME}

The present invention relates to fine powders of mixed plastics and a method for producing the same. In particular, the present invention relates to fine powders of waste plastics that are easily reused as plastics, fuels, etc., which have been discarded in living and industrial activities, and a method of manufacturing the same.

In order to use as a substitute material for coke and pulverized coal, the technique which blows waste plastics into a vertical furnace, such as a blast furnace or a scrap melting furnace, or a cement kiln, is known.

For example, Japanese Patent Application Laid-Open No. 2001-220589 proposes to granulate waste plastic and blow it out of a tuyere by air transportation to effectively use the waste plastic as a coke replacement product. According to this technique, in order to improve the combustion rate in a raceway of a furnace, the waste plastic particle is controlled and the waste plastic of about several millimeters in diameter is manufactured.

However, when the particle diameter of the waste plastic is several mm, the combustion speed is sufficiently high, and in the case of blowing this into the blast furnace in large amounts, the ratio of the amount of waste plastic to the amount of oxygen in the blowing air is expected to decrease as a result. .

Therefore, in order to further improve the burning rate of waste plastic, it is necessary to further refine the waste plastic. By the way, in order to grind the waste plastic by the mechanical force in the state as it is and to obtain the granularity similar to pulverized coal, special means such as cooling by liquid nitrogen is required, and the cost becomes high.

Therefore, a number of techniques have been proposed in which waste plastics are heated to be melted, cooled, and then solidified by pulverizing waste plastics, or a technique for performing the same treatment in a solvent or a heat medium.

For example, Japanese Patent Application Laid-Open No. 11-192469 discloses a technique of heating a plastic to 150 ° C or higher in a container to remove low boiling point components, cooling, solidifying and pulverizing it. In Japanese Patent Laid-Open No. 11-197630 or Japanese Patent Laid-Open No. 11-140474, a method of mixing and heating waste plastics with a solvent in a container at 150 ° C. or higher and pulverizing is disclosed. In both techniques, the average particle diameter of the pulverized product is about 1 mm.

Moreover, in the technique of dechlorination in the melt stirring process of waste plastic using a solvent or a medium, it is necessary to recover or circulate the used solvent or medium. Alternatively, in the technique of dechlorination in the melt-stirring process of waste plastic without using a solvent or a medium, it is difficult to make fine powder because of insufficient agitation, and it is difficult to secure a combustion rate for use in large quantities in a blast furnace. It could not be used sufficiently as a substitute for pulverized coal.

On the other hand, in general, discarded plastics often contain chlorine-containing plastics such as polyvinyl chloride. Since chlorine-containing plastics generate hydrogen chloride when heated, it is contemplated to corrode the material and piping of furnaces when they are blown into water furnaces or cement kilns. Therefore, in the prior art, efforts have been made to separate and remove the chlorine-containing plastic as a pretreatment of the grinding technique.

For example, Japanese Patent Application Laid-open No. Hei 9-178130 discloses a method of dividing waste plastics into film-shaped synthetic resins and other synthetic resins, carrying out shredding treatment, and then separating chlorine-containing plastics having a specific gravity by wet centrifugation or the like. It is. In this method, the separation efficiency of the chlorine-containing plastic depends on the shape of the plastic to be injected, and in order to achieve greater separation efficiency, it is necessary to sufficiently manage the physical properties (specific gravity, impurities, etc.) of the specific gravity liquid. Since the wet centrifugation method uses a relative specific gravity difference with the specific gravity liquid, polystyrene and polyethylene terephthalate having a specific gravity equivalent to that of the chlorine-containing plastic are mixed into the heavy material such as the chlorine-containing plastic, resulting in separation loss. In addition, since the specific gravity liquid is attached to the waste plastic (hard material side) having a low chlorine concentration, a drying process is essential.

The present invention has been made to solve such a problem of the prior art.

That is, an object of the present invention is to provide a fine powder of a mixed plastic having a low chlorine content and a manufacturing method thereof. In particular, the present invention provides a fine powder of waste plastic having a low chlorine content and a method of manufacturing the same.

The present invention provides a process for preparing a mixed plastic having a chlorine concentration of 2 to 20 mass% by increasing or decreasing at least one plastic selected from the group consisting of a chlorine-containing plastic and a chlorine-free plastic; Stirring the mixed plastics under melting to dechlorine the chlorine concentration to 0.9 mass% or less; Cooling and solidifying the dechlorinated agitated substance; And a step of pulverizing the solidified material.

Moreover, in this manufacturing method of mixed plastic fine powder, it is preferable to add the plastics containing chlorine to waste plastics, and to prepare the mixed plastics with the said chlorine concentration of 2-20 mass%.

Moreover, in the manufacturing method of any one of said mixed plastic fine powders, it is preferable that the said stirring is kneading with an extruder.

In addition, in the method for producing the mixed plastic fine powder, it is preferable to remove water at the front part of the extruder and to remove hydrogen chloride at the rear part of the extruder. Alternatively, the extruder may include a plurality of extruders, remove water from an anterior kneader, and remove hydrogen chloride from a posterior kneader.

Moreover, in the manufacturing method of the mixed plastic fine powder as described in any one of the above, it is preferable that at least 1 sort (s) of plastic chosen from the group which consists of the said chlorine-containing plastic, the said chlorine-free plastic, and the said mixed plastics is waste plastic. Do.

Moreover, this invention is also the fine powder of the mixed plastics and / or the waste plastics whose particle diameter 500 micrometers or less obtained by the manufacturing method in any one of said above is 80 mass% or more.

Moreover, this invention is also the processing method of the plastic which blows in the blast furnace the said fine powder of the said mixed plastics and / or the fine powder of the said waste plastics.

Moreover, in the processing method of this plastic, it is preferable to mix granulated plastic beforehand into the fine powder of the said mixed plastics, and / or the fine powder of the said waste plastics.

In another aspect, the present invention is characterized in that the waste plastics are mixed with chlorine-containing plastics to heat and melt the mixed waste plastics whose chlorine concentration is adjusted to 2 to 20 mass%, and then solidified by cooling to form solids, and then pulverizing the solids. It is also a treatment method for plastics.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the mechanism of a grindability improvement.

2A, 2B and 2C are explanatory views of the mixing state of waste plastic by a stirring tank having a rotary blade.

3A, 3B and 3C are explanatory views of the mixing state of waste plastic by the extruder.

4 is a graph showing the thermogravimetric analysis of various plastics.

5 is an explanatory diagram of one embodiment of the present invention.

6 is an explanatory diagram of an embodiment of the present invention.

7A is a schematic diagram of an ultrarotor.

7B is a schematic diagram of the pulverizer.

7C is a schematic view of a jet mill.

8 is a graph comparing the grindability by heating temperature when using an extruder.

9 is a graph comparing the crushability in the case of using an extruder and the case of using a stirring vessel.

FIG. 10 is a graph showing the yield of the milled powder having a diameter of 500 µm or less for each mill.

Since the chlorine-containing plastics mixed in the waste plastics as a state of the metal become corrosion factors of the metal, it has been conventionally preferred to remove the chlorine-containing plastics in order to grind the waste plastics. However, the present inventors have found that by adjusting the chlorine concentration in the waste plastic to a predetermined range, it is easy to stir the melt of the waste plastic even in a system not using a solvent or a medium. As a result, it was surprising that the chlorine concentration was very low and fine waste plastic powder was obtained because the dechlorination of the waste plastic was promoted in the stirring process. That is, in the case of most waste plastics having a daily composition, it was found that waste plastic powder having a low chlorine concentration is obtained finely by increasing chlorine concentration by actively adding chlorine-containing plastic.

That is, the present invention provides a process for preparing a mixed plastic having a chlorine concentration of 2 to 20 mass% by increasing or decreasing at least one plastic selected from the group consisting of a chlorine-containing plastic and a chlorine-free plastic;

Stirring the mixed plastics under melting and dechlorination;

Cooling and solidifying the dechlorinated agitated substance; And

Process of pulverizing the said solidified product: The manufacturing method of the mixed plastic fine powder which consists of this, and the fine powder of the mixed plastic with low chlorine concentration obtained by this method.

In this manufacturing method, the mixed plastic having the chlorine concentration of 2 to 20 mass% may be prepared by adding or removing the plastic containing chlorine and / or the plastic containing no chlorine. Moreover, the said chlorine concentration which is preferable from a viewpoint of agitation efficiency, dechlorination efficiency, and micronization is 3-20 mass%, More preferably, it is 4-20 mass%. In addition, the chlorine concentration in the mixed plastic after the dechlorination step is preferably set to 0.9 mass% or less.

In addition, from the viewpoint of reusing waste plastics as a reducing agent or fuel, at least one plastic selected from the group consisting of plastics containing chlorine, plastics not containing chlorine, and mixed plastics is preferably waste plastic. .

Therefore, hereinafter, the present invention will be described with respect to waste plastics.

When waste plastic is the object of the present invention, the mixed plastic having a chlorine concentration of 2 to 20% by mass is preferably prepared by adding plastic containing chlorine and / or plastic not containing chlorine to the waste plastic. This is because it takes time to separate and remove plastics containing chlorine or plastics containing no chlorine from waste plastics. Moreover, since general chlorine concentration is less than 2 mass%, it is more preferable to add the chlorine containing plastic to waste plastics, and to prepare the said chlorine concentration.

The waste plastics used in the present invention are used plastics. Waste plastics are usually a mixture of plural kinds of plastics, and are aggregates of plastics having different polymerization repeating units, glass transition point, melting point, decomposition temperature and the like. More specifically, they are thermoplastic resins such as polyethylene, polypropylene, polystyrene, vinyl chloride resin, polyethylene terephthalate, and fluorine resin, and thermosetting resins such as phenol resin and urethane resin, and even the same polyethylene may have a different polymerization degree (molecular weight). .

Moreover, although the composition of the waste plastics of this invention changes with a generation place and a generation time, the following composition can be illustrated. Polyethylene: 20 to 47% by weight, polypropylene: 15 to 35% by weight, polystyrene: 15 to 30% by weight, PET: 6 to 26% by weight, vinyl chloride: 1 to 8% by weight, other plastics and foreign materials: 0 to 20 % By weight. In the present invention, unused plastic may be mixed with the used plastic. For waste plastics, the amount of unused plastic will be on the order of less than 50% by weight for economic reasons. Also, some of the waste plastics may be compatible with each other when melted, and some may not be used. Furthermore, since inorganic substance is included as a filler and it exists as a laminate with aluminum foil, inorganic substance is also mixed. Examples of the inorganic fillers include silica, calcium carbonate, titanium oxide, alumina and the like.

The chlorine-containing plastics are, for example, plastics containing chlorine components such as PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride), plastics having a high content ratio of these plastics, or waste plastics thereof. In the present invention, similarly, waste plastics and unused plastics can be alternately read.

As the chlorine-containing waste plastic, it is particularly preferable to use PVC, PVDC or the like as industrial waste. In addition, waste plastics subjected to specific gravity separation and the like can be used, and waste plastics having high chlorine concentration separated as high specific gravity can be used. Since these chlorine-containing waste plastics generate hydrogen chloride with heating, they have been inadequate for recycling in the prior art. Therefore, chlorine-containing waste plastics may be discarded and mixed with waste plastics at low cost.

The reason for adding the chlorine-containing plastic to the waste plastic in the present invention is as follows.

If the waste plastic contains chlorine-containing plastic, in particular polyvinyl chloride (PVC), it is heated to eliminate hydrogen chloride. The chlorine-containing plastic in which the number of hydrogen atoms with respect to the number of carbon atoms produced by this desorption reaction is reduced forms a carbonaceous gel that is harder to soften or melt than the plastic containing no chlorine and has good grinding properties. When such plastics are cooled to form a solid, the carbonaceous gel becomes a starting point of fracture, and when cooled, stress is generated at the boundary between the carbonaceous gel portion and the other portion, and the crushability of the plastic solid is improved.

This mechanism is explained using the schematic diagram of FIG.

Process a is a waste plastic before treatment, and a mixture of different plastics of polypropylene (PP) (1), polyethylene (PE) (2), polyvinyl chloride (PVC) (3), and polystyrene (PS) (4) It is a state. By heating these, it will be in the melt-blended state of process b. Furthermore, by heating, dehydrochlorination of PVC (3) occurs, soft carbonaceous gel (5) is produced as shown in step c, and the plastic is made low in molecular weight. By cooling this, the plastic shrinks and residual stress is generated at the interface due to the difference in shrinkage ratio of each plastic, and crack 6 is generated as shown in step d. When the solidified body in such a state is impacted, the carbonaceous gel 5 becomes a starting point of destruction, and as shown in step e, the waste plastic can be pulverized. That is, it is considered that dehydrochlorination of chlorine-containing plastics such as PVC is more likely to occur than decomposition of hydrocarbon-based plastics, and it is a feature of the present invention to disperse and install the starting point of destruction in waste plastics using this.

In order to improve the grinding property, the carbonaceous gel is preferably mixed homogeneously with the waste plastics, and when the chlorine-containing plastic is added to the waste plastics, it is preferable that the mixture is sufficiently mixed.

PE, PP and the like also have different thermal properties such as thermal conductivity, but not as much as carbonaceous material 5, but a residual stress is generated in the solidified body after cooling, and becomes a starting point of cracking when the solidified body obtained by cooling is pulverized.

The chlorine content of the waste plastic is adjusted to 2 to 20 mass% after adding the waste plastic. If it is less than 2 mass%, the origin of breakage is small and the effect of improving the grinding property is low. If it exceeds 20 mass%, the amount of carbonaceous gel formation increases, the transportability deteriorates, and the stirring efficiency deteriorates. In addition, it is difficult to efficiently carry out dehydrochlorination by heat melting treatment, and the residual chlorine concentration of the plastic pulverized product becomes high. According to the method of the present invention, fine powders of waste plastics having a residual chlorine concentration of 0.9 mass% or less can be easily obtained, but when the plastic pulverized product having a residual chlorine concentration of more than 0.9 mass% is blown into the furnace, environmental pollution and Problems such as damage may occur, and in the case of blast furnaces, it is contemplated to lower the quality of slag which is a product. In addition, although chlorine as a component of inorganic substances such as salt and soy sauce derived from waste may adhere to the waste plastic, the chlorine content defined in the present invention is contained as a component of chlorine-containing plastic such as PVC as described above. The amount of chlorine that is present.

In the method of this invention, it is preferable that the said stirring is kneading by an extruder.

In Japanese Patent Laid-Open No. 11-192469, waste plastics are heated and melted, and then cooled and solidified waste plastics are pulverized and micronized. Specifically, the waste plastic in the container is heated and melted to 150 ° C. or higher by an external heater, and then hydrogen chloride generated by distillation under reduced pressure while stirring using a rotary blade is distilled away together with the low boiling point component. Subsequently, the molten waste plastic is cooled and solidified, and then pulverized using a conventional mill to obtain finely divided waste plastic.

However, if a large amount of waste plastic is to be treated in this method, mixing may be insufficient in agitation with a rotary blade, and thus it cannot be said that it is very suitable for grinding a large amount of finely solidified waste plastic. In order to obtain a sufficient stirring effect or to reduce the residual chlorine concentration, a long treatment time is required.

In addition, the above-described method of stirring the molten waste plastic in the container with the rotary blades results in a batch treatment, and thus has poor thermal efficiency, and is not suitable for treating a large amount of waste plastic even from the stirring force.

On the other hand, there is a method of blowing gas into the liquid as a method of stirring the liquid. However, in order to maintain a high stirring efficiency, it is necessary to generate fine bubbles from the lower part of the container and to maintain the bubbles to the liquid level.

However, it is difficult to generate microbubbles in high viscosity liquids such as molten plastic. In addition, gas agitation is not preferable in terms of the large-scale treatment of the exhaust gas and causing an increase in the equipment cost.

In the present invention, a waste plastic treatment method comprising a step of kneading waste plastic melted by an extruder, a step of cooling and solidifying the kneaded waste plastic and a step of grinding the solidified waste plastic are preferred.

Hereinafter, the present invention will be described in comparison with a method of stirring waste plastic melted in a vessel (also called a stirring tank) with a rotary blade, taking out the stirred waste plastic from the vessel, cooling it, and grinding the solid waste plastic. do.

2A, 2B, 2C, 3A, 3B, and 3C will be described by comparing the mixed state in the waste plastic caused by the difference in treatment by the stirring vessel and the extruder.

2A is a schematic diagram of the stirring vessel 11 and FIG. 3A is an extruder 12. The Reynolds number (Re) distribution in the stirring vessel 11 and in the extruder 12 is shown in FIG. 2B at the position A-A 'in FIG. 2A and in FIG. 3B at the position B-B' in FIG. 3A. . Moreover, the disperse | distribution state of the heterogeneous plastic and inorganic material in the molten plastic in the stirring tank 11 and the extruder 12 is typically shown to FIG. 2C and FIG. 3C.

The Reynolds number (Re) is a dimensionless quantity defined by Re = UL / ν, where the velocity is U, the typical length of the object L, and the kinematic viscosity is ν when the object is in a constant flow of viscous fluid. . It is interpreted as the magnitude of the inertia effect on the viscous effect.

When the Reynolds number (Re) distribution in the stirring tank 11 and the extruder 12 is compared, it is nonuniform in a stirring tank as shown in FIG. 2B, and it becomes uniform in an extruder, as shown in FIG. 3B, and stirring efficiency is favorable. Although the stirring tank 11 is a method of stirring with the rotary blade 13, it is stirring in a circumferential direction, and there exists a difference in fluid velocity in the center of a stirring tank, near a wall surface, and the upper and lower parts of a stirring tank.

On the other hand, in the extruder 12, the stirring system serves as a conveyance, and the speed in the conveying direction becomes almost uniform, although the fluid velocity is different in the center of the extruder and near the wall surface.

Therefore, in consideration of the distribution of the heterogeneous plastic and the inorganic substance in the molten plastic, as shown in FIG. 2C, the heterogeneous plastic having a low compatibility at the high melting point, the heteroplastic ( 15) and the inorganic material 16 are unevenly dispersed, and the sizes of the heterogeneous plastics 15 and the inorganic material 16 are also nonuniform. On the other hand, in the extruder, as shown in FIG. 3C, the heterogeneous plastics 15 and the inorganic substance 16 are in a state of uniform dispersion, and the particle diameter and the like are also almost uniform. Moreover, in general, the extruder is stirred while moving in a narrow cylinder, so that the extruder is made of a heterogeneous plastic 15 and an inorganic substance 16 having a small particle size as compared to the stirring vessel.

Since waste plastics are a mixture of plural kinds of plastics, it is inferred that the dissimilar plastics are melted and agitated and brought into a sufficient mixing state, thereby improving the pulverization after cooling and facilitating micronization.

Accordingly, when the molten plastic is cooled and pulverized, a pulverized product having a narrower particle size distribution is obtained when the extruder is used than when a stirring tank is used, and the average particle size is also reduced, and the pulverization is improved.

An extruder is an apparatus which has an extrusion screw in a cylinder, heats and melts the plastic in a cylinder, and conveys it while kneading. Since the screw power of the extruder is large and melt kneaded while the waste plastic moves in the narrow cylinder, a good mixing state can be obtained by sufficient stirring force. In addition, since the residence time in the extruder can be easily adjusted by changing the diameter and rotational speed of the screw, the controllability is high and the predetermined operating conditions are easy to be performed. Moreover, the degree of freedom in designing a manufacturing line is great, for example, by arranging a plurality of extruders. Any number of screws of the extruder can be used, but from the viewpoint of processing efficiency, it is preferable to use an extruder having two or more screws.

Moreover, since an extruder can carry out conveyance simultaneously with stirring, it can respond easily to a continuous process. As described above, the pulverized waste plastic has a small average particle diameter and a narrow particle size distribution. Therefore, by incorporating an extruder into a waste plastics processing facility, it is possible to produce a large amount of finely ground waste plastics by a continuous process having good thermal efficiency.

In the present invention, an extruder having a degassing pipe for water at the front end and a degassing pipe for hydrogen chloride at the rear end is used, and water is removed from the waste plastic at the front end. It is preferable to remove hydrogen chloride at the rear end.

Due to being waste, most waste plastics contain water. In addition, plastics containing chlorine, such as polyvinyl chloride, are often included. Plastics containing chlorine generate hydrogen chloride by heat treatment. The generated hydrogen chloride dissolves in the water contained and becomes hydrochloric acid, which corrodes various devices and its piping. Therefore, it is preferable to carry out dehydrochlorination when preparing fine powder of waste plastic. In the present invention, in the kneading step using the extruder, after the water is evaporated and removed at a relatively low temperature in the front of the extruder, hydrogen chloride generated by pyrolysis at the rear end of the extruder can be removed. In this way, contact between water and hydrogen chloride can be avoided as much as possible, so that generation of corrosive hydrochloric acid can also be suppressed. In addition, the front end of an extruder means the part of the waste plastic inlet side in an extruder. Similarly, the rear end of the extruder refers to the portion of the waste plastic outlet side in the extruder. Here, the ratio between the front end and the rear end device is not particularly limited, and is appropriately determined by the processing conditions.

At the front end of the extruder, the higher the heating temperature, the lower the heat loss in the next step. However, it is necessary to be less than the temperature at which hydrogen chloride is generated, and it is preferably about 160 to 200 ° C. If a corrosion resistant material is used for the piping which discharge | releases water vapor, it can also process at high temperature. This treatment is aimed at dehydration and melting, and it is preferable to treat at low temperature and in a short time as compared with the conditions of the latter stage described later.

At the rear end of the extruder, the waste plastic remaining without melting at the front end is melted and kneaded sufficiently to efficiently disperse the constituent plastics, and to remove chlorine contained in the waste plastic by surface renewal. Can be. Although the heating temperature of the rear stage is higher than 300 ° C., it is more advantageous to remove hydrogen chloride from the waste plastic, but the depolymerization of the plastic also proceeds, and since the low-molecularized component vaporizes, the recovery rate as a pulverized product decreases. Therefore, it is preferable to make heating temperature of the said rear stage into about 320-390 degreeC. This treatment is not only for dehydrochlorination but also for high-efficiency agitation of the molten waste plastic, which requires a high temperature and a long time as compared with the conditions of the shear.

When performing such a degassing process, it is preferable that the contact area of molten plastic and external air is large. In order to increase the contact area, for example, the amount of waste plastic input may be adjusted, or a convex part may be provided on the cylinder top of the extruder. In addition, the gas liquid interface is updated at any time by the rotation of the screw, and the renewal area of the interface can also be increased by controlling the rotational speed of the screw. In this way, separation of gas such as hydrogen chloride generated by using an extruder is further facilitated, and degassing can be performed with higher efficiency than when plastic is heated using a stirring tank.

In addition, to melt the waste plastic by external heating, it is preferable to heat the plastic inside without local heating, and efficient heat supply is important. When the extruder is used, the molten plastic in contact with the heat transfer surface can be quickly updated by the rotation of the screw, so that uniform heating of the waste plastic is easy. However, in the method using a stirring vessel, it is difficult to secure a sufficient heat transfer area because the stirring mechanism is held therein.

In the kneading step described above, one extruder having a degassing pipe for water at the front end and a degassing pipe for hydrogen chloride at the rear end is illustrated, but the kneading step may be performed using two or more extruders. In the case of using two or more extruders, at least two extruders of the extruder of the front stage having the degassing piping for water and the extruder of the rear stage having the degassing piping for hydrogen chloride may be arranged in series. That is, the above-mentioned dehydration-kneading operation may be performed by the extruder of the front end, and the dehydrochlorination-kneading operation mentioned above may be shared by the extruder of the said downstream stage. By using two or more extruders, it is easy to set or change the processing conditions and to make maintenance easier.

The extruder of the latter stage preferably has a degassing space at the top of the cylinder. The presence of a degassing space allows for efficient dehydrochlorination. At this time, it is also possible to supply an inert gas such as nitrogen to the degassing space and actively discharge hydrogen chloride out of the system. In addition, the pipe is preferably heated to the same or above the heating temperature of the extruder of the rear end.

The heating method is not particularly limited, but electric heating is usually used from the ease of temperature control. The method of burning fuel and indirectly heating may be sufficient, and you may heat with the fruit heated separately. In addition, the fruit may be passed through the screw and heated.

The plastic discharged from the extruder of the rear stage may be cooled by a known method such as direct water cooling or indirect cooling such as a steel belt cooler. Moreover, it can also be set as desired shape by the dice etc. which were provided in the discharge port. When waste plastic is extruded more than die | dye, it may be cut | disconnected suitably, it may be made into pellet shape, it may be made into plate shape by the roller which has the mechanism of indirect or direct cooling, and it may be cut | disconnected after that, and it may be set as crushed object.

In any case, the solidified body of the waste plastic (hereinafter also referred to as solidified body) can be easily crushed as compared with the untreated waste plastic. The pulverization method may be carried out using a conventional pulverizer, but for pulverization, it is preferable to perform pulverization after coarse crushing. As a grinding | pulverization system, the impact / friction system like a ball mill, the friction system like a roller mill, the impact system like a hammer mill, and the impact method between particle | grains in the airflow, such as a centrifugal mill (jet mill), etc. can be used. What is necessary is just to select a grinding | pulverization method suitably according to the target particle diameter. For example, when grinding | pulverizing to a particle diameter of 1.0 mm or less, it is preferable to grind | pulverize by the impact of a hammer in addition to mutual collision of the said solidified body. That is, it is preferable that a grinder has a hammer, and the grinding | pulverization of the said solid body is performed by the impact force given by a hammer, and the collision of the said solid bodies.

The pulverized product of the waste plastic (or mixed plastic) obtained by the method of the present invention may be a fine powder having a particle size of 500 μm or less, which occupies 80 mass% or more. A pulverized product having such a particle size distribution has sufficient combustibility and can be blown into a blast furnace or the like even if the pulverized coal blowing facility is used as it is. More preferably, the particle size distribution has a particle size of 100 µm or less and 80 mass% or more. Such fine waste plastics are very combustible and thus improve the combustion rate.

If economically acceptable, a compatibilizer or a stirring medium may be added when the waste plastic is introduced into the extruder. The addition of the compatibilizer or the stirring medium may be added to the extruder simultaneously with the waste plastic, or may be added after mixing with the waste plastic in advance.

The compatibilizer facilitates the dispersion of the component plastics when the waste plastic is melted and kneaded, so that fine waste plastic powder is easily obtained.

PVC, which is a representative chlorine-containing plastic, can be largely divided into hard PVC and soft PVC. Soft PVC is the addition of plasticizers, such as DOP (dioctyl phthalate and boiling point: 231 degreeC) and DIDP (diisodecyl phthalate, boiling point: 261 degreeC), to PVC. DOP and DIDP are an example of what acts as a compatibilizer. The plasticizer has the effect of lowering the viscosity at low temperatures and facilitates uniform mixing of heterogeneous plastics. If soft PVC is present, when heated from room temperature, the plasticizer is first released and a dehydrochlorination reaction occurs in parallel with it. Plastics, such as PE and PP, exist as a liquid phase at 300 degrees C or less, and decompose at the temperature beyond that (FIG. 4).

It is also possible to add a plastic (for example, a hard urethane resin) which decomposes at a processing temperature or lower and generates gas. In this case, by actively generating pores in the molten plastic, cracks during pulverization tend to occur and the pulverization is improved.

In addition, by adding a plastic having different thermal properties such as thermal conductivity, for example, coal, etc., cracks at the time of pulverization are more likely to occur from the higher cooling rate at the time of cooling, and the crushability is improved.

On the other hand, waste plastics are easily dispersed by addition of the stirring medium. For example, when an organic solvent or an organic dispersion medium is used, the waste plastic swells or dissolves partly, thereby facilitating melting, decreasing the viscosity of the molten plastic, and facilitating the release of hydrogen chloride into the gas phase. . As a result, the pulverization of the plastic pulverized product is also improved. The stirring medium is preferably one having a function of swelling and / or dissolving plastics. It is preferable that such a stirring medium contains a substituted aromatic compound. For example, the polycyclic aromatic hydrocarbon which has a methyl group, an ethyl group, or an alkyl group of carbon number more than that is mentioned. More specifically, alkyl phenanthrene, alkyl anthracene, etc. are mentioned. Moreover, these aromatic hydrocarbons may contain oxygen, nitrogen, etc. in a ring, and an alkyl quinoline, alkyl carbazole, etc. are mentioned specifically ,. All of the above alkyl groups may further have an alkyl substituent. These stirring media may be added in an appropriate amount such that the waste plastic solidifies upon cooling. Moreover, in order to raise grindability by a grinder, the softening point of 100 degreeC or more is preferable.

As a particularly preferable medium, coal tar and petroleum tar can be used. Coal tar is heavy oil (bottom oil) from the bottom of a coal tar atmospheric distillation column. Specifically, the soft pitch and the soft pitch leaked from the bottom of the tower where the pressure was distilled under reduced pressure (softening point 110 ° C), the oil leaked from the stop of the distillation column under reduced pressure (distillation temperature of 154 ° C in the reduced pressure distillation column), Oil fraction (HOB: distillation temperature in a vacuum distillation column at 255 ° C.), heavy oil components obtained from coal liquefied oil components, and blended oils thereof. Petroleum-based tars include petroleum-based reduced pressure oil, ethylene bottom oil, reformed oil and FCC oil.

The fine powder of the waste plastic or the fine powder of the mixed plastic obtained in the present invention is very suitable for being blown into various furnaces and used as a reducing agent or a fuel.

5 is an explanatory diagram in the case where the fine powder of the waste plastic obtained by the method of the present invention is blown into the blast furnace.

In this example, the extruder at the front end for water removal and the extruder at the next end for dehydrochlorination are arranged in series.

The waste plastic 71 is preliminarily removed from foreign matter other than plastic as much as possible by magnetic screening, wind screening, and / or water washing, and then is introduced into the extruder 72 at the front end. It is preferable to crush the waste plastic 71 in a predetermined shape in advance, and in order to prevent clogging caused by foreign matter on the die 76, which will be described later, it is preferable to crush it to a die diameter or less. The waste plastic 71 is heated to about 200 ° C. by the extruder 72 at the front end, and melt kneaded while dewatering. The water may be removed by appropriately providing an exhaust port in the cylinder of the extruder 72 at the front end. The molten waste plastic extruded from the extruder 72 at the front end is subsequently heated to about 370 ° C. in the extruder 73 at the rear end and melt-kneaded while dechlorinated. The generated gas, such as hydrogen chloride gas, generated by heating in the extruder 73 at the next stage is sent to the gas treatment system 75 through the degassing pipe 74 for processing. In the gas treatment system 75, combustion treatment, hydrochloric acid, tar recovery, or the like can be performed. The degassing pipe 74 is heated to the same extent as the extruder 73 at the rear end in order to prevent adhesion of tar or the like. The plastic extruded through the die 76 from the rear extruder 73 is cooled and solidified in the water cooling tank 77 or the like, and is cut into a predetermined length to form a pellet. What is necessary is just to implement using a conventional method, such as using a commercially available pellet manufacturing apparatus, when extruding and pelletizing molten plastic from the extruder 73 of a later stage.

The pellets of the produced waste plastics are coarsely pulverized by the first mill 78, and the crude mills are further milled by a second mill 79. The finely divided plastic fine powder is used in the blast furnace 80.

6 is another embodiment using the fine powder of the waste plastic of the present invention. In this embodiment, the granulated plastic is mixed in advance in the fine powder of the waste plastic and blown into the blast furnace.

19 is a crushing device of imported plastic, 20 is a crusher, 21 is a balloon and / or magnetic separator, 22 is a granulator, 23 is a sieve device, 24 is a first extruder (melt dewatering), 25 is 2nd extruder (dechlorine), 26 is a cooling device, 27 is an exhaust gas treatment device, 28 is a vibrating screen device, 29 is a rough crusher, 30 is a fine grinding machine, 31 is a classifier, 32 is a solid gas separator, 33 is a cooler , 34 is a vibrating screen device, 35 is a product hopper, 36 is a differential plastic storage silo, 37 is a assembled plastic storage silo, 38 is a blowing device, 39 is a pretreatment device, 40 is a blower, 41 to 57 is a conveying means, and 58 is Represents a blower.

The pretreatment device 39 may be disposed as necessary for the post process. In the case where the solid is not pulverized, there is a possibility of dust explosion, and an inert gas for adjusting the oxygen concentration is supplied as necessary. When the inert gas is circulated and used, heat is generated due to the impact of the hammer and the solidified body in the pulverizer. Therefore, a cooler is installed in the inert gas line.

The finely divided plastics obtained by the present invention are blown into the blast furnace alone, but in some cases they may be blown into the blast furnace simultaneously with the waste plastic assembled to 10 mm or less.

The conveying means is conveying by a belt conveyor, airflow transportation, and a vehicle, and selects a conveying means as needed. However, from the pulverizer 30 to the vibrating screen device 34, a series of powders is handled, and it is preferable to carry out by airflow transportation.

It does not specifically limit as a grinder. For example, the grinder of the "ultra rotor" type | mold shown by FIG. 7A (made by W.I.Al.) is mentioned. The pulverizer has a rotary hammer, which can simultaneously perform pulverization due to the impact of the hammer 17 and pulverization due to mutual collision of pulverized products due to locally generated vortices. 60 represents a screen. Moreover, the hammer density which impact-crushes with a hammer can be utilized. In addition, as shown in FIG. 7B, the raw materials impact-pulverized by the high-speed rotation of the hammer 17 are classified by the classification rotor 18, and the fine powder is discharged to the outside of the machine. (Iii) A pulverizer (micro-ACM pulverizer type A / ACM-10A: manufactured by Hosokawa Micron Co., Ltd.) having a structure that is repulverized by collision between them can also be used. As shown in Fig. 7C, a jet mill (single truck / jet mill / STJ-200) having a structure in which it is pulverized by the impact of the pulverized product colliding in the jet stream and subjected to pulverization again by a classification action. The stock company's sashing company system) is suitably used. 61 indicates the outlet of the pulverized product.

The fine powder of the waste plastic thus obtained can be blown into the blast furnace 59 using a fine coal injection device or the like already installed and used as a reducing agent for iron ore.

Example 1

Using the equipment shown in Fig. 5, micronization treatment of waste plastic was performed. The used waste plastics were waste at ordinary households, and were 32 mass% polyethylene, 31 mass% polypropylene, 22 mass% polystyrene, and 15 mass% other (paper, etc.) in the state in which plural kinds of plastics and foreign substances were mixed. Foreign substances such as metals were removed and washed, and the film-like ones were sorted and crushed to a particle size of about 20 mm and used for the treatment. Chlorine content was 1.4 mass% after removal of foreign matter.

The waste plastics subjected to the above-mentioned pretreatment are mixed with shredded products of industrial waste PVC shredded to a particle diameter of about 20 mm, and the chlorine concentration in the waste plastics is 1.4 (without mixing chlorine-containing plastics) to 24.1 mass%. (Nos. 1-7) were prepared, and after heat-melting, it cooled, it was made into the solidified body, and it grind | pulverized and manufactured the grind | pulverized material.

Heat-melting of waste plastics to which chlorine-containing plastics were added was carried out using an extruder. The heating temperature in the 1st extruder was 180 degreeC, and the heating temperature in the 2nd extruder was 335 degreeC. The generated gas, such as hydrogen chloride gas, generated by heating in the second extruder, was sent to the gas treatment system through a pipe for treatment. In the gas treatment system, hydrochloric acid and tar were recovered. The plastic extruded using the dice | dies from the 2nd extruder was cooled and solidified by water cooling 7, it was cut | disconnected to predetermined length, and pelletized. The molten plastic was extruded from the second extruder, hot cut, and pelletized. The prepared pellets were coarsely ground in a first mill, and the mills were further milled in a second mill. As a 2nd grinder, the grinder of the "ultra rotor" type | mold shown by FIG. 7A (made by W.I.Al.) was used. The coarsely pulverized plastic is introduced into the lower raw material inlet, finely pulverized, and recovered from the pulverized product outlet.

The residual chlorine concentration and particle size distribution of the plastic pulverized product produced as described above were measured. Residual chlorine concentration, average particle diameter (D50), and a yield of 500 micrometers or less are shown in Table 1. The average particle diameter (D50) used in the present example is a particle diameter such that the mass of the cumulative particles becomes 50% of the total when the powder is classified for each particle diameter by a sieve. The yield of 500 micrometers or less is the weight ratio of the particle which passed the sieve of 500 micrometers.

At 1.4 mass% (No. 1) of chlorine concentration in waste plastic, the crushability was bad, and the yield of 500 micrometers or less was 66%. On the other hand, when the chlorine concentration in waste plastic was 2.4 mass% or more (No. 2-No. 7), it turned out that the yield of 500 micrometers or less will be 80 mass% or more, and the average particle diameter (D50) after grinding | pulverization will fall drastically. Further, when the chlorine concentration in the waste plastic is 20 mass% or less, the chlorine concentration in the waste plastic powder obtained can be lowered to 0.9 mass% or less. 2 to No. I found it in the example of 6. However, No. 2, the chlorine concentration in waste plastic, was set at 24.1 mass%. Although the yield of 500 micrometers or less showed 93 mass% in 7, the carbonaceous gel produced | generated became large, the load of the 2nd extruder became large, and stable manufacture was difficult. The residual chlorine concentration was 1.21 mass%.

Next, after removing the foreign matter, a part of the waste plastic having 2.4 mass% was subjected to centrifugation using water to obtain a high chlorine concentration plastic having a chlorine content of 7.6 mass% as a specific gravity. Mixed waste plastics with a chlorine content of 4.1 mass% by mixing chlorine content of 2.4 mass% with waste plastics and 2.4 mass% of waste plastics and high chlorine concentration plastics in a ratio of 2: 1. For Cl), a pulverized product was prepared in the same manner as above. The results are shown in FIG.

The yield of the particle size of 500 micrometers or less which occupies for the grind | pulverized material obtained on the conditions of the processing temperature of 320 degreeC was 72 mass% when the high chlorine concentration plastic was not added, and 93 mass% when the high chlorine concentration plastic was added. When the heating temperature in the second extruder was changed from 320 to 370 ° C., the yield of particles having a particle size of 500 μm or less occupied in the obtained pulverized product was 80 mass% when no high chlorine concentration plastic was added, and a high chlorine concentration plastic was added. Was 96 mass%, and it was found that the grindability was improved.

The chlorine concentration of the pulverized product obtained under the treatment temperature of 320 ° C. was 0.73 mass% when the high chlorine concentration plastic was not added, while the chlorine concentration was dechlorinated to 0.84 mass% even when the high chlorine concentration plastic was added. When the heating temperature in the second extruder was changed from 320 to 370 ° C., the chlorine concentration of the pulverized product was 0.37 mass% when the high chlorine concentration plastic was not added, while 0.39 even when the high chlorine concentration plastic was added. It could be dechlorinated to about the same level as mass%.

On the other hand, for the sake of comparison, the micronization treatment using the stirring vessel shown in FIG. 2A was also performed.

The waste plastic was stirred while heating to 180 degreeC in the stirring tank, the melted waste plastic was transferred to another stirring tank (not shown), and it heated to 320 degreeC, and dechlorination was performed. Thereafter, the product was solidified by cooling to prepare a pulverized product in the same manner as in the case of using an extruder. In the case of the stirred tank system, a pulverized product was also prepared for the addition of high-chlorine waste plastic (chlorine content 7.6 mass%) obtained by centrifugation to the waste plastic (33 mass%) (hi-Cl). In addition, the grinding | pulverization of the above-mentioned example was performed using FIG. 7A.

The particle size distribution of the pulverized product was measured, and the comparison between the case of using an extruder and the case of using a stirring vessel was shown in FIG. In the same figure, it turned out that the particle | grains which used the extruder had many fine grinding materials, and the grinding property improved. It was also found that the addition of waste plastics with high chlorine concentration significantly improved the crushability.

Next, the grindability by the kind of grinder was examined.

The waste plastic without the addition of high chlorine concentration plastic was formed by using an extruder, and the pulverization of the solid was tested using another kind of grinder. As the mill, the above-mentioned hammer mill, jet mill, pulverizer and ultra rotor were used.

The yield of 500 micrometers or less of the waste plastics obtained by each grinder is shown in FIG. When using an ultra rotor and a pulverizer compared with a hammer mill and a jet mill, the yield of 500 micrometers or less was 80% or more, and the yield of 80% or more was obtained. Therefore, it was found that an efficient fine grinding is achieved in the grinding method in which the impact grinding by the rotary hammer and the grinding by the mutual collision of the pulverized product by the locally generated vortex are simultaneously performed.

According to the flow of FIG. 6, the micronization process of the waste plastics was performed, and the blowing test to the blast furnace was performed. Used waste plastics are general household wastes, and 32 mass% of polyethylene, 31 mass% of polypropylene, 22 mass% of polystyrene, 6 mass% of PVC, etc. (mass of other resins, metals, paper, etc.) in a state where a plurality of plastics and foreign substances are mixed. % And moisture: 5.6 mass% (except from the total amount). Chlorine content was 2.4 mass% after removal of foreign matter.

This was disintegrated, coarsely crushed, ballooned, charited, and granulated at a processing speed of 1.19 t / h to obtain 1.00 t / h granulated material and 0.13 t / h foreign material. The granulated material was melted at 180 ° C. at a rate of 1 t / h and dechlorinated at 335 ° C. to obtain a cracked gas containing 0.90 t / h solid and 0.10 t / h hydrogen chloride. The cracked gas was neutralized after combustion. Further, coarsely pulverized and finely pulverized, a finely ground pulverized product of 0.90 t / h 100% of a 1 mm sieve and a particle diameter of 0.5 mm or less were recovered. The chlorine concentration of the obtained milled product was 0.7 mass%, and the calorific value was 8900 kcal / kg. This was stored in the pulverized plastic storage tank for blast furnace injection, and it supplied to the injection tank at 0.9 t / h by the quantitative cutting device. On the other hand, conventionally used granulated plastics (a cylindrical shape of 7 mm Φ, a mixture of shreds of 10 mm or less) were put into the blowing device in the quantitative cutting device at a rate of 4 t / h. Quantitative discharge was carried out from the blowing tank in the apparatus, and blown into the blast furnace. The blast furnace has an effective volume of 5000 m 3 (number of blow holes: 38) and the molten iron production amount of 11537 t / d. The blowing conditions and test results of the blast furnace are shown in Table 2. The raw unit is a value necessary for producing one ton of molten iron. ηCO is a value calculated from the gas composition of the blast furnace furnace top gas, represents CO ₂ / (CO + CO ₂ ), and represents the effective utilization rate of the reducing gas generated at the bottom of the blast furnace. Further, fine powder plastic was produced under the above conditions, and after storage, the blowing speeds of the fine powder plastic and the granulated plastic were changed, and blast furnace blowing was performed. Compared with the blowing of granulated plastics conventionally used, mixing waste plastic powder and blowing into a blast furnace can improve the combustibility of the granulated plastics, and as a result, the reduction of the reducing agent ratio is aimed at.

Table 1

TABLE 2

When the method of the present invention is applied, very low chlorine concentration and fine waste plastic powder can be easily obtained without removing the chlorine-containing plastic from the mixed plastic such as waste plastic. The fine powder of the waste plastic thus obtained can easily transport air and have high combustibility, so that plastics discarded in living and industrial activities can be reused as a reducing agent or fuel. Therefore, the present invention can contribute to the industry widely.

Claims (11)

delete delete delete Preparing a mixed plastic having a chlorine concentration of 2 to 20 mass% by increasing or decreasing at least one plastic selected from the group consisting of a chlorine-containing plastic and a chlorine-free plastic; Stirring the mixed plastics under melting and dechlorination to a chlorine concentration of 0.9 mass% or less; Cooling and solidifying the dechlorinated agitated substance; And, A step of grinding the solids; The stirring is kneading by an extruder; Removing water from the front end of the extruder, hydrogen chloride is removed from the rear end of the extruder, characterized in that for producing a fine powder. Preparing a mixed plastic having a chlorine concentration of 2 to 20 mass% by increasing or decreasing at least one plastic selected from the group consisting of a chlorine-containing plastic and a chlorine-free plastic; Stirring the mixed plastics under melting and dechlorination to a chlorine concentration of 0.9 mass% or less; Cooling and solidifying the dechlorinated agitated substance; And A step of grinding the solids; The stirring is kneading by an extruder; The extruder is composed of a plurality of extruders, to remove the water in the extruder of the front end, the method of producing mixed plastic fine powder, characterized in that to remove the hydrogen chloride in the extruder of the next stage. delete The method according to claim 4 or 5, A method for producing mixed plastic fine powder, characterized in that at least one plastic selected from the group consisting of chlorine-containing plastics, chlorine-free plastics and mixed plastics thereof is waste plastic. Particle size 500 micrometers or less obtained by the manufacturing method of Claim 7 is 80 mass% or more, The fine powder of the waste plastics characterized by the above-mentioned. The fine plastics waste plastics of Claim 8 are blown into the blast furnace, The waste plastics processing method characterized by the above-mentioned. A method for treating waste plastics, which comprises mixing granulated plastics in advance in the fine powder of waste plastics according to claim 8 and blowing into a blast furnace. delete

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