JP2005053090A - Method and apparatus for separating mixed waste plastics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To still more lower the chlorine content of a chlorine non-containing plastic separated from mixed waste plastics to respond to the demand related to the reduction of chlorine content from a receiving side. <P>SOLUTION: The mixed waste plastics containing a chlorine-containing plastic are stirred to produce friction heat and, after the chlorine non-containing plastic is melted by this frictional heat to subject to granulation processing, the waste plastics are separated into the chlorine-containing plastic and the chlorine non-containing plastic. At the time of granulation processing, cooling operation is performed a plurality of times within a temperature range from the melting start temperature of the chlorine non-containing plastic to the below melting temperature of the chlorine-containing plastic during the temperature rise of the mixed waste plastics. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the present invention, chlorine-containing plastics {PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride)} (hereinafter referred to as PVC and / or PVDC) are classified as “chlorine” from plastic waste in general and industrial wastes. The present invention relates to a method and an apparatus for separating the “containing plastic”.

  Plastic waste, generally called waste plastic, includes a plurality of types of plastics, including polystyrene (PS), polyethylene (PE), polypropylene (PP), PVC (polyvinyl chloride) and PVDC (polyvinyl chloride). Chlorine-containing plastics such as vinylidene chloride) are also included. When recycling such mixed waste plastics containing chlorine-containing plastics, the following becomes a problem.

  One method of effectively using waste plastic is to blow it into a blast furnace as a reducing agent for iron sources at steelworks, but hydrogen chloride gas is generated due to the thermal decomposition of chlorine-containing plastics, and the equipment is corroded. There is a problem to say. For this reason, when the waste plastics are effectively used, it is necessary to perform a pretreatment for removing the chlorine-containing plastics in advance so that the content rate is equal to or less than an allowable value.

  There has been disclosed a method capable of dealing with this problem and obtaining a plastic having a low chlorine content by separating the chlorine-containing plastic from the mixed waste plastic (for example, see Patent Document 1).

  The technique of Patent Document 1 is based on the fact that the melting point of chlorine-containing plastic and non-chlorine-containing plastic are different. In this technique, mixed waste plastic containing chlorine-containing plastic and non-chlorine-containing plastic is agitated to generate frictional heat due to collision between plastic pieces, and for example, the temperature at which non-chlorine-containing plastic melts while stirring is continued. The molten plastic is granulated by raising the temperature up to. Next, the mixed plastic becomes chlorine-containing plastic by separating the plastic (non-chlorine-containing plastic) that has become a granular material and plastic that has not been granulated (chlorine-containing plastic) by dry specific gravity shape separation or shape separation means by wind sorting. And non-chlorine-containing plastics that can be used effectively.

According to this method, a plastic granular material having a low chlorine content that can be used as a fuel material for blowing into a blast furnace, a cement kiln or the like of an ironworks is obtained.
JP 2002-205306 A

  According to the technology disclosed in Patent Document 1, a low-chlorine content and recyclable plastic can be obtained. On the side that accepts and uses the waste plastic, supply of waste plastic with a lower chlorine content Is desired.

  The present invention has been made to solve the above-described problems, and can further reduce the chlorine content of non-chlorine-containing plastics separated from waste plastics, and to reduce the chlorine content from the receiving side. It is an object of the present invention to provide a method and apparatus for separating mixed waste plastic that can meet the demand.

  The above prior art is a method in which the mixed waste plastic granulated by the melt granulator is separated into a granular material and a non-granular material by a shape separation means, and the granular material is recovered as a non-chlorine-containing plastic. However, according to the results of the following investigation conducted by the present inventors, it is not possible to sufficiently reduce the chlorine content of the obtained non-chlorine-containing plastics simply by performing a treatment that separates the granular and non-particulate materials. I found out.

  The survey was conducted as follows. The film-like waste plastic mixed with PVC waste was crushed to a size of about 20 mm and agglomerated by a melting granulator for softening and melting by agitation to generate frictional heat and granulating. Next, the treated product is separated by a dry specific gravity shape separation apparatus shown in FIG. 6, and then the material (heavy one) separated into granular materials is sieved and divided into six particles, and the chlorine content of each particle As a result, the results shown in Table 1 were obtained. In addition, the particle size of Table 1 shows the opening size of the sieved sieve.

  According to Table 1, the chlorine content of the granulated product is higher as the particle size is smaller, and the chlorine content of the fine particles is particularly high. The chlorine content gradually decreases as the particle size increases, but increases again when the particle size exceeds a certain limit. Specifically, the chlorine content of the particles of 9.5 mm to 5.6 mm and the particles of 5.6 mm to 2.8 mm is the lowest, and is high before and after that. Thus, the chlorine content of the granulated product varies depending on the size of the granule, and only a certain range of particle sizes has a low value. In Table 1, the one having a particle size range centered around about 5 mm has the lowest chlorine content.

  The chlorine content in the granulated product shown in Table 1 is due to the fact that PVC is mixed into the particles of non-chlorine-containing plastics that have been melted and granulated. , PVC has a property of being pulverized into powder and fine particles. In other words, since PVC contains a large amount of plasticizers such as DOP that easily volatilize, when the waste plastic mixed with PVC is heated, a part of the plasticizer in PVC is volatilized and the PVC becomes brittle. It will be in a state of taking on. And while the PVC which became brittle is being stirred in a melt granulator, it is grind | pulverized and becomes a powdery substance or a fine particle. Many of the PVC powders and fine particles produced in this way are separated during the subsequent process, but some of them adhere to the surface of non-chlorine-containing plastic particles or are confined inside. It mixes with the granulated product.

  The results of Table 1 were examined for the PVC contamination that occurred in this way. First, the reason why the chlorine content of the fine particles and powders among the granulated materials is remarkably increased is considered as follows. Part of the PVC powder and fine particles produced as described above adheres to the melted non-chlorine-containing plastic particles. The smaller the surface area, the larger the proportion of PVC powder and fine particles that adhere, and thus the higher the chlorine content.

  In addition, the cause of the high chlorine content of the grains exceeding the limit is considered as follows. In a melt granulator that granulates by frictional heat of stirring, the cooling operation is performed when the non-chlorine-containing plastic piece softens and melts to form small particles and the small particles grow to an appropriate size while gathering. The melted grains are solidified. At that time, it is sandwiched between the molten particles in which PVC powder and fine particles gather, and is confined inside. However, when rapid growth of the grains occurs, many particles adhere suddenly and integrate. Therefore, PVC existing in the vicinity of the aggregated particles is embraced together and confined inside.

  And when large grains are produced, rapid growth of the grains occurs at any point in time, and the large grains contain a large amount of PVC trapped inside, so that the chlorine content of the large grains will increase. It is.

  As described above, since the chlorine content in the granulated product is contained in a large amount in small and large particles, the formation of large particles is suppressed, and the powdery and fine particles in the granulated product, If small particles that have been separated into products are removed, the chlorine content of the non-chlorine-containing plastic separated as a product will be significantly lower than that of the prior art.

  The present invention has been made based on the above examination results, and has the following characteristics.

  The method for separating mixed waste plastic according to claim 1 performs a process of stirring the mixed waste plastic containing chlorine-containing plastic to generate frictional heat, and melting and granulating the non-chlorine-containing plastic by the frictional heat. Then, in the waste plastic separation method for separating into chlorine-containing plastic and non-chlorine-containing plastic, the non-chlorine-containing plastic is melted during the temperature rise of the mixed waste plastic during the granulation process. The cooling operation is performed at least twice within the temperature range from the starting temperature to the melting temperature of the chlorine-containing plastic.

  The method for separating mixed waste plastic according to claim 2 is the method according to claim 1, wherein the sieving treatment is performed to divide the granulated material into a material having a particle size smaller than a predetermined particle size and a material having a predetermined particle size or larger. It is characterized by doing.

  The method for separating mixed waste plastic according to claim 3 is the method according to claim 2, wherein a shape separation process is performed for separating a sieved particle size or more into a granular material and a non-granular material. It is characterized by.

  The apparatus for separating mixed waste plastic according to claim 4 stirs the mixed waste plastic containing chlorine-containing plastic to generate frictional heat, and melts and granulates the non-chlorine-containing plastic by the frictional heat. After that, in the waste plastic separator that separates into chlorine-containing plastic and non-chlorine-containing plastic, measure the temperature of the molten granulation tank equipped with a stirrer and the mixed waste plastic stirred in the melt granulation tank A temperature measuring device, a watering device for cooling the melted plastic particles, and a control for operating the watering device when the measured values by the temperature measuring device reach a plurality of preset cooling temperatures. And a granulating apparatus having a control device configured to be performed, and a sieve for sieving the granulated material discharged from the melt granulating apparatus It is characterized by having a device.

  In the present invention, the temperature at which the non-chlorine-containing plastic starts to melt means the temperature at which a part of the non-chlorine-containing plastic starts to shrink and melt to become a granular material. The melting temperature of the chlorine-containing plastic means a temperature at which a part of the crushed piece of the chlorine-containing plastic starts to melt and melt.

  The predetermined particle size means the opening size of a sieve for obtaining a plastic having a chlorine content equal to or less than a target value when sieving waste plastics discharged from the granulation process. As mentioned above, since the chlorine content in the granular material increases as the particle size decreases, the sieve opening size that determines the lower limit of the particle size to be recovered as a recyclable plastic is the target for the chlorine content. Although it is determined by the value, the determination is made based on the past results in consideration of the properties of the waste plastic to be processed, the transfer conditions of the melt granulator, and the like. In the sieving step, a sieve having an opening of 1 to 3 mm is usually used.

  As described above, it is inevitable that a certain amount of chlorine-containing plastic is mixed into the non-chlorine-containing plastic recovered as a product, but in the present invention, two means for suppressing the mixing are taken. It is intended to minimize contamination of the contained plastic.

  As a first means, the granulated product is cooled a plurality of times in the final stage of the granulation treatment, thereby suppressing the formation of large particles. The effect of this means for suppressing the formation of large grains has been experimentally confirmed, and the details of the mechanism relating to the action of this means are not clear. However, according to the test results of the present inventors, it has been recognized that the generation ratio of large grains varies depending on the processing conditions at the initial stage of granulation, particularly where the non-chlorine-containing plastic begins to soften and melt. The generation of large grains due to the difference in the processing conditions at the initial stage is considered to occur as follows.

  The initial stage of granulation, where the melting of the non-chlorine containing plastic is initiated, is the stage where the plastic piece softens and shrinks and then begins to melt and become fine granules. And since the rate of temperature rise increases from around that temperature (softening and melting start temperature), the shrinking and melting plastic, that is, the plastic in the middle of granulation is entangled and adheres to the aggregate. It is thought that this aggregate will result in the formation of large grains during subsequent processing.

  For this reason, in the present invention, the grain cooling is performed a plurality of times in the growth process from the time when the non-chlorine-containing plastic starts to be granulated to the time when the grain becomes an appropriate grain size. This cooling method will be described with reference to FIG.

FIG. 8 is a diagram showing a temperature change when cooling is performed twice during the granulation process. In the figure, T _m is the softening and melting start temperature, T ₁ is the primary cooling start temperature and a predetermined temperature set slightly higher than the softening and melting start temperature T _m , and T _S is the final cooling start temperature and starts the final stage of cooling. Indicates a predetermined temperature.
In the prior art, cooling is started when the temperature of the mixed waste plastic being stirred rises to the final cooling start temperature T _S , the temperature of the particles is rapidly lowered to solidify, and the granulation process is finished. . When this cooling method is used, large grains are easily generated. The generation of this large is believed to be due to easily occur rapid grain growth in the vicinity past the softening melting start temperature T _m.

On the other hand, in the above-described two-time cooling according to the present invention, after the softening and melting of the non-chlorine-containing plastic starts, the primary cooling is performed when the primary cooling start temperature T ₁ is reached, and the temperature rises again. and performs a final cooling upon reaching the final cooling start temperature T _S and are finished granulation process. According to this cooling method, the ratio of large grains is reduced.
By the way, in the initial stage of granulation where the non-chlorine-containing plastic begins to soften and melt and partly becomes granular, since the amount of heat generated by stirring increases, a temperature difference occurs between the particle surface and the inside, Surface temperature rises abnormally. For this reason, adhesion of particles is promoted, and an aggregate of plastic pieces is formed.
However, if cooling is performed at the initial stage of granulation, the particle surface temperature is cooled before it abnormally increases, so that the formation of the aggregate is interrupted. Then, the temperature of the particles rises again due to the continued stirring, but the surface temperature of the particles does not immediately rise abnormally, so it seems that the formation of large particles is greatly suppressed.

  In addition, when the aggregate in which the plastic pieces are entangled and adhered is rapidly cooled by cooling at the initial stage of granulation, the thermal shock at that time causes separation between different types of plastics, causing adhesion or confinement. The chlorine-containing plastic that had been left is detached from the assembly. For this reason, by cooling at the initial stage of granulation, the formation of large grains is suppressed and the chlorine content of the granular material is lowered.

  Note that FIG. 8 only describes the case where the cooling is performed twice. However, if more cooling is performed during the growth process of the particles that have passed the softening and melting start temperature, large grains are formed. It is further suppressed. In addition, the chlorine content of the granular material is further reduced.

  In addition, as a second means, it is possible to carry out a sieving process to divide the granulated processed material into those having a predetermined particle size and those having a predetermined particle size or more, and thereby the chlorine content is high. Powdery materials and fine particles, PVC powdery materials and fine particles are removed, and the chlorine-containing plastic is efficiently separated.

  In the above sieving process, the separation efficiency of the chlorine-containing plastic can be increased only by performing the operation alone, and when it is performed in combination with other means, the separation efficiency can be increased. There are cases where it can be done. Whether the sieving operation is carried out alone or in combination with other means is determined mainly based on the properties of PVC in the waste plastic to be treated.

  That is, according to the test results of the present inventors, when PVC is contained when the waste plastic is stirred and granulated, PVC powder or fine particles are produced. The degree of becoming a product or fine particles varies depending on the properties of PVC. When PVC is a thin film, most of the PVC is crushed into granules and fine particles during granulation, but the PVC is relatively thick like a bottle. In some cases, some remain uncrushed.

  For this reason, when the PVC contained in the mixed waste plastic is thin, most of the PVC adheres to the powder, fine particles, and small particles in the granular material. These chlorine-containing plastics can be separated simply by sieving the treated material.

  However, when the PVC is relatively thick, PVC that has not been pulverized is present in the processed product discharged from the melt granulator, in addition to the powdery material and fine PVC. Since most of the unpulverized PVC is indistinguishable from the large particles in the granular material, the PVC that has not been pulverized even if the processed product discharged from the melt granulator is sieved. Will be sorted into the same category as large grains. For this reason, in this invention, when PVC is comparatively thick, the processed material discharged | emitted from the melt granulation apparatus is sieved, and it is in the powdery material, fine particle, and granular material which contain much PVC. After removing the small particles, specific gravity shape separation and wind sorting are performed. In this separation process, unpulverized PVC is not granulated and is classified into light ones, so that it is separated from the particulates and removed.

  ADVANTAGE OF THE INVENTION According to this invention, the chlorine content rate of the non-chlorine containing plastic isolate | separated from waste plastic can be reduced further, and the request | requirement with respect to the chlorine content rate reduction from the receiving side can be met.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view of an example of a mixed waste plastic separation processing method according to the present invention. This figure shows the case where waste plastic containing a thin chlorine-containing plastic is processed. In FIG. 1, the mixed waste plastic 80 containing chlorine-containing plastic is crushed into a size of about 10 to 50 mm square in the crushing step 10. The crushed mixed waste plastic is sent to the granulation step 11. In the granulation step 11, the melt granulator shown in FIGS. 3 and 4 is used, and the mixed waste plastic is stirred at a high speed to generate frictional heat. This frictional heat causes non-chlorine having a melting point lower than that of the chlorine-containing plastic. A process is performed in which the contained plastic is melted into a granulated product and the chlorine-containing plastic is not melted. In such a stage, the mixed plastic is cooled by spraying water twice. First, sprinkling of the non-chlorine-containing plastic crushed pieces begins to sprinkle at a predetermined temperature that reaches a stage where a part of the crushed pieces starts to melt and small particles start to be generated, and the first cooling (primary cooling) is performed. In this first cooling, the temperature is reduced to such an extent that the molten non-chlorine-containing plastic is solidified. The solidified non-chlorine-containing plastic is heated again to melt and become a granular material. Next, when a predetermined temperature is reached at which the grains grow and have an appropriate size, water is sprayed and final cooling is performed. By performing the cooling twice as described above, the formation of large particles is suppressed, and a granulated product having an appropriate size can be obtained.

  The granulated mixed waste plastic is sieved with a sieve having a predetermined size in the sieving step 12. By this sieving operation, the grain content with a high chlorine-containing plastic content is less than a predetermined particle diameter (particulate 82 consisting of powder, fine particles, and small particles) and the chlorine-containing plastic content with a low content is not less than a predetermined particle diameter. It is divided into things 81.

  The granular material 81 having a predetermined particle size or more separated by the above-described treatment has a high content of PVC and less than a predetermined particle size, and also has a small proportion of large particles and a low chlorine content. It can be reused as a raw material to be blown into a blast furnace or a raw material to be blown into a cement kiln as an iron source reducing agent.

  In the description of FIG. 1, only the case where the sieving process in the sieving step 12 is removed to be less than the predetermined particle diameter is described, but the sieving process in the present invention is simultaneously performed as necessary. The process which isolate | separates the large grain more than a predetermined particle size is performed.

  FIG. 2 is an explanatory view of another example of the mixed waste plastic separating method according to the present invention. This figure shows the case of processing waste plastic containing a thick chlorine-containing plastic. In FIG. 2, operations in the three steps of crushing step-granulating step-sieving step are the same as those in FIG. In this embodiment, a shape separation processing step 13 is provided after the sieving step 12. As described above, when waste plastic containing thick chlorine-containing plastic is melted and granulated, it contains chlorine that has not been crushed until it becomes powdery or fine particles. This is because plastic (non-particulate matter) is mixed, and in the sieving step, the non-particulate matter (chlorine-containing plastic) and particulate matter having a predetermined particle size or more cannot be separated. For this reason, after the sieving step 12, there is provided a step of separating what has been separated as having a predetermined particle size or more into granular and non-granular materials.

  In the shape separation processing step 13, shape separation processing means such as a dry specific gravity shape separation device shown in FIG. 6 to be described later or a wind power sorting device shown in FIG. 7 is used, and the particle size is larger than a predetermined particle size separated in the sieving step 12. A process of dividing the product (mixture 83 of the granular material and the non-granular material) into a granular material 84 mainly made of non-chlorine-containing plastic and a non-granular material 85 mainly made of chlorine-containing plastic pieces is performed.

  Since only a small amount of PVC or PVDC adheres to the granular material 84 separated by the above treatment, the granular material 84 is reused as a raw material blown into a blast furnace or a raw material blown into a cement kiln as an iron source reducing agent. Can be used.

  In the mixed waste plastic separation treatment method shown in FIG. 2, the treatment steps are provided in the order of crushing, granulation, sieving, and shape separation, but the treatment for increasing the removal rate of the chlorine-containing plastic is: The order is not necessarily limited to the above. You may process in order of crushing-granulation-shape separation-sieving. However, according to the method of FIG. 2 in which the processing steps are provided in the order of sieving and shape separation, those having a particle size less than the predetermined particle size are removed in the sieving step, so the load is reduced in the shape separation processing step. At the same time, it is only necessary to perform an operation of separating the particulate matter (heavy) and the non-particulate matter (light) into two, so that the processing is simplified.

  Next, an apparatus used in the present invention will be described. FIG. 3 is a diagram showing an example of a configuration relating to a melt granulator used in the granulation step. In FIG. 3, reference numeral 20 denotes a melt granulation tank in which mixed waste plastic is charged to perform granulation treatment, and friction heat is generated by rotating a stirrer 21 provided at the bottom thereof at high speed. Reference numeral 80 denotes the mixed waste plastic charged.

  A temperature measuring device 34 for measuring the temperature of the waste plastic being stirred and a watering device 31 for cooling and solidifying the molten non-chlorine-containing plastic are provided on the upper part of the melt granulation tank 20. The watering device 31 is activated and stopped by an instruction signal from the watering control device 35. The sprinkler control device 35 has set values for the primary cooling temperature (predetermined temperature at the stage where melting of the non-chlorine-containing plastic starts) and the final cooling temperature (predetermined temperature for obtaining a granulated product having a desired particle size range). When the measured value of the temperature measuring device 34 reaches the set value, the control valve 33 is opened for a predetermined time so that the amount of cooling water sprayed from the watering device becomes a predetermined amount. Become. Reference numeral 40 denotes a sieving apparatus for sieving the granulated material that has been cooled and solidified as described above to remove particles having a high chlorine content and less than a predetermined particle size.

  FIG. 4 is a perspective view showing the structure of the melt granulator. In FIG. 4, 20 is a melting granulation tank in which mixed waste plastic is charged and granulated, and 21 is a stirrer that generates frictional heat by rapidly stirring the mixed waste plastic 80 charged in the melting granulation tank 20. is there. The stirrer 21 is disposed in the lower part of the melt granulation tank, and the stirring blade 22 that rotates in the circumferential direction of the melt granulation tank 20 is disposed substantially parallel to the bottom surface of the melt granulation tank 20. Reference numeral 23 is a motor for driving the stirring blades, 24 is an inlet, 25 is a discharge port, and 26 is a gate provided at the discharge port. Reference numeral 80 denotes mixed waste plastic.

  FIG. 5 is a view showing an example of the structure of a stirrer provided in the melt granulator, FIG. 5 (a) is a front view of the stirrer, and FIG. 5 (b) is a plan view of the stirrer. The stirrer is provided at the bottom of the melt granulation tank, and has a structure in which a plurality of stirring blades 22 are attached to a rotating plate 28 attached to a rotating shaft 27. The mixed waste plastic charged in the container is stirred and heated up.

  The stirring blade 22 is composed of a main blade 29 formed in parallel with the bottom surface and a vertical blade 30 standing on the main blade 29, and those having various structures are used depending on the operating conditions of the melt granulator.

  In FIG. 4, only the stirring blade in which the main blade 29 is formed in parallel with the bottom surface has been described, but the stirring blade 22 may be any as long as it has a function of stirring waste plastic and generating frictional heat. It is not limited to the structure shown in FIG. For example, the main blade 29 may be inclined with respect to the bottom surface.

  FIG. 6 is a perspective view showing an air table type dry specific gravity shape separation device which is one of the separation means used in the shape separation processing step. The separation device includes a vibrating screen 50 that can vibrate substantially horizontally in the vibration direction 62, and a plurality of baffle plates (ruffles) 51 that are disposed on the vibrating screen 50 in parallel with each other in substantially the same direction as the vibration direction. In addition, the vibration sieve 50 is inclined (end slope) toward the vibration direction 52 and is also inclined (side slope) toward the horizontal direction orthogonal to the vibration direction 52.

  Then, while causing the vibrating sieve 50 to vibrate in the vibration direction 52, the ascending air flow 53 is jetted from below the vibrating sieve 50, whereby the mixture 83 of the particulate matter and the non-particulate matter charged on the vibrating sieve 50 is obtained. The particulate matter (heavy) 84 and the non-particulate matter (light) 85 are separated by the specific gravity difference and the shape difference. The powdery material is scattered together with the rising air flow 53 and collected by a dust collector.

  As described above, the particles having a predetermined particle size or more separated by the sieving device have a granular material having a low chlorine content or a predetermined particle size, a non-particulate material having a high chlorine content, and a chlorine content. Divided into very high powders.

  FIG. 7 is a diagram showing a wind power sorting device which is one of the separating means used in the shape separation processing step. This apparatus is called a zigzag type wind sorter, in which 60 is a wind sorter body formed in a zigzag type, 61 is an inlet for a mixture 83 of particulate matter and non-particulate matter, and 62 is a wind sorter body 60. A blower 63 for blowing air from the lower part of the dust collector 63 is a dust collector.

  In this wind power sorter, air is blown by a blower 62 to generate an upward flow in the wind power sorter main body 60, and a mixture 83 of particulate matter and non-particulate matter is thrown from an inlet 61 provided at the top. To do. Of the mixture 83, non-particulate matter (film-like or lightweight) 85 is scattered with the rising air flow and collected by the dust collector 63. On the other hand, the granular material 84 falls and is collected. In this way, the fraction 83 having a predetermined particle size or more separated by the sieving device is divided into a granular material 84 having a low chlorine content and a non-particulate material 85 having a high chlorine content. In the above-described wind sorting, the air flow velocity in the wind sorter main body 60 is normally set in the range of 2 m / sec to 4 m / sec.

  Next, examples of the present invention will be described.

  In this example, the chlorine-containing plastic was separated from the waste plastic by a four-stage process of crushing, granulation, sieving, and shape separation. The waste plastic that was processed was waste plastic collected by local governments and used for containers and packaging.

  The treatment for separating the chlorine-containing plastic was performed as follows. A container-packaged plastic bale was loosened with a crusher and then crushed with a crusher to obtain a screen-passed product of about 10 to 50 mm. The main non-chlorine-containing plastic contained in this crushed material was PE.

  250 kg of the crushed material was charged into a melt granulator having the same configuration as in FIG. 3, and the temperature was increased by rotating the stirrer at high speed. When the temperature of the charge reached 143 ° C., 5 liters of cooling water was sprinkled from the watering device, and the first cooling (primary cooling) was performed. Next, when the temperature of the charge reached 155 ° C., 15 liters of cooling water was sprinkled from the watering device, and the second cooling (secondary cooling) was performed.

  The primary cooling start temperature 143 ° C. is a temperature in a state in which a part of the charged non-chlorine-containing plastic crushed material starts to melt and reaches a stage where small particles are generated, and is based on the state observation during the past operation. It is the value decided. The secondary cooling start temperature 155 ° C. is a temperature at which a granulated product having an appropriate particle size range is obtained, and is a value determined based on experimental results.

  The granulated waste plastic is discharged from the melt granulator, and sieved with a sieve having an opening of 2.8 mm. Those having a particle size smaller than a predetermined particle size (under the sieve) and those having a particle size larger than the predetermined particle size (on the sieve) Divided into.

  The above sieve was charged into a dry specific gravity shape separation apparatus having the same configuration as that shown in FIG. 6, and separated into a granular material and a non-granular material, and the granular material was recovered as being reusable. Table 2 shows the results of examining the chlorine content of the recovered granular material and the proportion of particles of 9.5 mm or more.

  Next, as a comparative example, a granulation process was performed by a conventional method in which cooling was performed only once, and a process of separating chlorine-containing plastic from waste plastic was performed. This separation process was performed in the same manner as in Example 1 except that the cooling performed during the granulation process was performed only once and the cooling start temperature was 158 ° C. The treated waste plastic was of the same lot as that used in Example 1.

  In the comparative example, when the waste plastic being stirred reached 158 ° C., 20 liters of cooling water was sprinkled from the watering device and cooled to finish the granulation treatment.

  The granulated waste plastic is discharged from the melt granulator, and sieved with a sieve having an opening of 2.8 mm. Those having a particle size smaller than a predetermined particle size (under the sieve) and those having a particle size larger than the predetermined particle size (on the sieve) Divided into. And the thing of 2.8 mm or more was inserted into the dry-type specific gravity shape separation apparatus, and it isolate | separated into the granular material and the non-granular material, and collect | recovered the granular material. Table 2 shows the results of examining the chlorine content of the recovered particulate matter and the proportion of particles having a particle size of 9.5 mm or more together with the results of Examples.

  According to Table 1, when the results of Example 1 and the comparative example are compared, in the example, all of the chlorine content, the recovery rate, and the +9.5 grain fraction (ratio of large grains) are good with respect to the comparative example. The value is obtained. First, regarding the chlorine content, the value of the example is lower than the value of the comparative example. This is due to the small generation rate of large grains (+9.5 mm), as is clear from the above-described investigation results (explanation of Table 1).

It is explanatory drawing of an example of the mixing waste plastic separation processing method which concerns on this invention. It is explanatory drawing of the other example of the mixing waste plastic separation processing method which concerns on this invention. It is a figure which shows an example of the structure which concerns on the melt granulation apparatus used at a granulation process. It is a perspective view which shows the structure of a melt granulator. It is a figure which shows an example of the structure of the stirrer with which a melt granulator is equipped. It is a perspective view which shows the air table type dry specific gravity shape separation apparatus which is one of the separation means used in a shape separation process. It is a figure which shows the wind power sorter which is one of the separation means used at a shape separation process. It is a figure which shows the temperature change at the time of cooling twice during a granulation process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Crushing process 11 Granulation process 12 Sieving process 13 Shape separation process 20 Melting granulation tank 21 Stirrer 22 Stirring blade 23 Motor 24 Loading port 25 Discharge port 26 Discharge port gate 27 Rotating shaft 28 Rotary plate 29 Main blade 30 Vertical Blade 31 Sprinkling device 32 Cooling water pipe 33 Control valve 34 Temperature measuring device 35 Sprinkling control device 40 Sieving device 50 Vibrating screen 51 of shape separation device 51 Baffle plate 52 Vibration direction 53 Ascending air flow 60 Wind power sorter body 61 Input port 62 Blower 63 Dust collector 80 Mixed waste plastic 81 Granules having a predetermined particle size or more 82 Granules consisting of powder, fine particles, and small particles 83 Mixture of particles and non-particles 84 Granules obtained by separating non-particles 85 Non-particles

Claims (4)

  The mixed waste plastic containing chlorine-containing plastic is agitated to generate frictional heat, and the frictional heat melts and granulates the non-chlorine-containing plastic, which is then separated into chlorine-containing plastic and non-chlorine-containing plastic. In the method for separating waste plastics to be treated, when the granulation treatment is performed, the temperature within the temperature range of the mixed waste plastic is within a temperature range from the temperature at which the non-chlorine-containing plastic starts to melt to the melting temperature of the chlorine-containing plastic. A method for separating mixed waste plastic, wherein the cooling operation is performed a plurality of times.   2. The method for separating mixed waste plastic according to claim 1, wherein a sieving treatment is performed to divide the granulated product into a product having a particle size of less than a predetermined particle size and a product having a particle size of not less than a predetermined particle size.   3. The method for separating mixed waste plastics according to claim 2, wherein a shape separation process is performed for separating the sieved particles having a predetermined particle size or more into granular and non-granular materials.   The mixed waste plastic containing chlorine-containing plastic is agitated to generate frictional heat, and the frictional heat melts and granulates the non-chlorine-containing plastic, which is then separated into chlorine-containing plastic and non-chlorine-containing plastic. In a waste plastic separator for processing, a melting granulation tank equipped with a stirrer, a temperature measuring device for measuring the temperature of the mixed waste plastic stirred in the melting granulation tank, and for cooling the melted plastic particles And a control device configured to control each of the watering devices to operate when the measured values by the temperature measuring device reach a plurality of preset cooling temperatures. A mixed waste plastic characterized by having a sieving device for sieving the granulated product discharged from the granulating device and the melt granulating device Away equipment.

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