JP4371439B2 - Specific gravity separator for waste plastic - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a specific gravity separation apparatus for waste plastic, and more particularly to a specific gravity separation apparatus capable of performing specific gravity separation regardless of the form of waste plastic containing polyethylene and vinyl chloride while reducing the size of the entire apparatus.
[0002]
[Prior art]
As a specific gravity separation method that separates these plastics using the specific gravity difference of various plastics contained in general waste plastics (hereinafter referred to as waste plastic), for example, a specific gravity separation method using buoyancy difference, centrifugal A specific gravity separation method using a so-called hydrocyclone using a force difference is known.
The former specific gravity separation method is mainly researched and developed as a separation method for wire covering plastics containing polyethylene and vinyl chloride. This method uses the fact that the pulverized wire covering plastic is put into a tank containing water, vinyl chloride having a specific gravity of about 1.35 to 1.45 sinks in water, and polyethylene having a specific gravity of about 0.92 to 0.96 floats in the water. In this method, polyethylene and vinyl chloride are separated.
[0003]
However, in this method, the surface of the plastic particle obtained by pulverizing the waste plastic peeled off from the electric wire has a complicated shape including irregularities, so that air adheres or adsorbs to the surface, and as a result, the plastic particle Especially, the surface of the vinyl chloride is not sufficiently wetted with water, the apparent specific gravity is lightened, the vinyl chloride that should be submerged in water does not settle, and it is mixed with polyethylene floating in the water to separate the polyethylene and vinyl chloride. Made it difficult.
In order to solve such a problem, the present inventor disclosed in Japanese Patent Application No. 4-264652 by vacuum degassing waste plastic before specific gravity separation to remove the air adhering to the surface of the plastic particle. In particular, a specific gravity separation device equipped with a vacuum deaeration device for making the surface of vinyl chloride particles easily wet with water has been proposed.
[0004]
Referring to FIG. 2, the specific gravity separation apparatus 100 is schematically described. The specific gravity separation apparatus 100 is connected to a supply hopper 90 filled with a waste plastic fluff through a gate valve 130, and further includes a vacuum pump 110 for evacuating the inside. A depressurization vessel 120, a vacuum pump 140 connected to the depressurization vessel 120 directly below the gate valve 130 for evacuating the interior, and a mixing agitation tank 160 equipped with a stirrer 150; The specific gravity separation tank 170 for separating vinyl chloride from the mixed slurry delivered from the stirring tank 160, the light fluff group selected by the specific gravity separation tank 170, and the heavy fluff group are each dehydrated and dried, and the dewatered surplus water is removed from the system. And a dehydrating / drying apparatus 180 for returning to the above. According to the specific gravity separation apparatus 100, the waste plastic is made to have a specific gravity by reliably sinking vinyl chloride, which has acquired hydrophilicity by the vacuum degassing action of the vacuum vessel 120 and the mixing and stirring tank 160, in water in the specific gravity separation tank 170. Can be separated.
[0005]
[Problems to be solved by the invention]
However, such a specific gravity separator causes problems during vacuum degassing and specific gravity separation.
First, in the vacuum degassing, since a method of evacuating the mixed fluff before being sent to the mixing agitation tank is adopted, firstly, the supply of the mixed fluff must be batch-processed. As a result, the processing efficiency is reduced. Secondly, for such batch processing, installation of a gate valve or the like or an increase in capacity of the vacuum pump is required. The inventor has confirmed through experiments that the degree of vacuum required for the surface of the plastic particles to be sufficiently wetted with water (hydrophilicity) is about 100 Torr, and that a high degree of vacuum is not required. Therefore, in this sense, the conventional specific gravity separator can be said to be an excess facility for ensuring the hydrophilicity of plastic particles, particularly vinyl chloride.
[0006]
In addition, from the viewpoint of securing the NPSH of the pump, the installation position of the mixing and stirring tank must inevitably be raised, and further, vacuum degasification of waste plastic and prevention of separation of vinyl chloride and polyethylene prior to specific gravity separation. For this reason, it is difficult to suspend waste plastic and water in parallel in the same container while achieving the desired functions. Make it difficult.
Thirdly, since a system in which the plastic fluff from the supply silo is sent to the mixing and stirring tank by free-falling is adopted, the applicable waste plastic results in being relatively heavy, for example, limited to a wire coating material plastic or the like. .
Next, during the specific gravity separation, a technical problem that reduces the specific gravity separation efficiency occurs. That is, the vinyl chloride having hydrophilicity in the specific gravity separation tank tends to sink below the surface of the water, but the plastic fluff is brought into the tank in a mixed form of heavy and light fluff groups, so the light fluff groups floating on the water surface. May trap heavy fluffs, especially preventing vinyl chloride from sinking. As a result, the heavy fluff group remains mixed in the light fluff group, and the separation efficiency is reduced. In order to prevent such a situation, the installation of a specific gravity separation tank having a sufficiently large opening area with respect to the amount of carry-in of the fluff causes an increase in the size of the equipment as described above.
[0007]
The latter specific gravity separation method, that is, the specific gravity separation method using a hydrocyclone, introduces a mixed slurry made of a mixture of waste plastic fluff and water from a tangential direction into a cylindrical container, and vortexes in the container. This is a method of separating into a heavy fluff group approaching the outer side of the container and a light fluff group approaching the inner side due to the difference in centrifugal force.
However, even if such a method is used, when it is introduced into the container in a state where air adheres to the surface of the heavy fluff group, which is inherently heavy in specific gravity, as in the case of the wire covering material plastic, it is apparent that May reduce the specific gravity of the light fluff, thereby mixing into the light fluff group and reducing the separation efficiency.
Therefore, in view of such problems, the object of the present invention is to provide a specific gravity separator for waste plastic that achieves improvement in specific gravity separation efficiency without being influenced by the form of waste plastic while achieving downsizing of equipment. There is to do.
[0008]
[Means for Solving the Problems]
In order to achieve the object of the present invention, the specific gravity separator for waste plastic according to the present invention is a specific gravity separator for separating the specific gravity of waste plastic by utilizing the difference in specific gravity of various plastics contained in the waste plastic. In the above, a mixing agitation tank for supplying and stirring a waste plastic fluff consisting of a light weight fluff group and water, to which the waste plastic was crushed, was sent from the mixing agitation tank upstream of the specific gravity separator. A vacuum degassing tower for degassing the mixed slurry under reduced pressure is used.
The specific gravity separation device has a specific gravity separation tank for floating the light fluff group of waste plastic in water and sinking the heavy fluff group in water, and the waste plastic is crushed upstream of the specific gravity separation tank. A mixing stirrer tank for supplying and stirring waste plastic fluffs consisting of light heavy fluff groups and water, and a vacuum deaeration tower for degassing the mixed slurry sent from the mixing stirrer tank It's okay.
[0009]
Further, the vacuum deaeration tower has an upper inlet for introducing the mixed slurry and a shape that substantially cooperates with each other and substantially covers the cross-sectional area, and has a predetermined interval in the longitudinal direction of the vacuum deaeration tower. It is preferable to have a plurality of stages of a pair of shelves arranged separately from the upper part toward the lower part.
Furthermore, one of the pair of shelves has an umbrella shape with a sharp upper portion disposed at a substantially central portion in a transverse section of the vacuum degassing tower, and the other of the pair of shelves is the vacuum escape tower. It is good to have an annular shape which is arranged over the entire inner peripheral surface and has a reduced diameter toward the lower side.
[0010]
[Action]
According to the waste plastic specific gravity separation device of the present invention, the vacuum degassing tower is installed on the downstream side of the mixing and stirring tank, thereby forcing the vacuum degassing tower toward the vacuum degassing tower. It is possible to degas from a mixed slurry made of plastic fluff mixed with water and water sent to the surface, and by removing air adhering to the surface of the fluff, the apparent specific gravity of the reduced fluff is reduced Separation efficiency can be ensured by making effective use of the specific gravity difference to the original specific gravity.
In addition, by installing the vacuum degassing tower on the downstream side of the mixing and stirring tank, in the sealed space in the vacuum degassing tower, water and water that were forcibly sent toward the vacuum degassing tower were mixed. It is possible to deaerate mixed slurry consisting of plastic fluffs, allowing continuous supply of mixed fluffs, and reducing the size of the entire system by eliminating gate valves and preventing large-capacity vacuum pumps. Furthermore, specific gravity separation can be applied to waste plastic fluffs made of various plastics such as films, sheets and containers.
[0011]
Furthermore, by providing a shelf in the vacuum degassing tower, etc., it is possible to reduce the size of the mixed slurry that freely falls in the tower and secure the degassing time, thereby improving the degassing efficiency from the mixed slurry. It becomes possible. .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
In FIG. 1, the specific gravity separation device 10 is roughly composed of a mixing and stirring tank 14, a vacuum deaeration tower 15, a specific gravity separation tank 16, a light fluff group dehydrator 18, and a heavy fluff group dehydrator 20. Yes. The system after the specific gravity separation tank 16 of the separation system according to the present embodiment is substantially the same as that of the specific gravity separation system for waste plastic by vacuum degassing disclosed in Japanese Patent Application No. 4-264652.
The mixing agitation tank 14 includes a stirrer 22 which will be described later, along with the plastic fluff supplied from the supply silo 1 via the conveyor belt 2, and water is continuously supplied at a predetermined ratio, for example, 2 to 10%. To be supplied into the tank. The internal volume of the mixing and stirring tank 14 is selected so that the plastic fluff and water are sufficiently mixed and stirred in the mixing and stirring tank 14 by the stirrer 22 having a predetermined stirring ability, and in particular, the specific gravity separation tank 16 described later. It is preferable to be smaller.
[0013]
The agitator 22 is a conventionally known type of propeller type agitator, for example, a predetermined number of stages and a predetermined number of blades 22c are connected to the tip of a rotating shaft 22b connected to a motor 22a. It is comprised so that a mixing stirring function may be fulfill | performed by rotating by. The number of blades 22c and the number of stages are appropriately selected in view of the amount of waste plastic fluff introduced into the mixing and stirring tank 14, the internal volume of the mixing and stirring tank 14, and the like.
The vacuum deaeration tower 15 is composed of a vertically long sealed container, and is connected to the mixing and stirring tank 14 by a line 23 through a first delivery pump 21. A line 25 for evacuating the inside of the container by a vacuum pump 17 is connected to the top of the deaeration tower 15, a line 23 from the mixing and stirring tank 14 is connected to the upper part, and an intermediate part is described in detail later. A pair of shelves 40 to be described are arranged at a predetermined interval in the longitudinal direction of the vacuum deaeration tower 15, and a constant amount of water is stretched at the lower part of the container. Is provided. The shelves each have a shape that substantially covers the cross-sectional area in cooperation with each other, and the upper side of the first and second tiers is an umbrella-shaped shelf 40a that is pointed upward and is arranged at the substantially center in the cross section, the lower side Is composed of an inclined annular shelf 40b having an annular shape with a reduced diameter toward the lower side, which is disposed over the inner peripheral edge of the container. The shelf is desorbed by securing the residence time in the tower, that is, the deaeration time, while the mixed slurry that falls freely from the top hits the shelf and becomes droplets and increases the surface area. Qi efficiency can be improved. Within the range in which this object can be achieved, for example, the upper side of the first and second stages may be constituted by a simple disk and the lower side may be constituted by an annular plate. As described above, the shape, arrangement, and number of steps of the shelf may be appropriately selected according to the supply amount of the mixed slurry, the cross-sectional area of the container, and the like as long as the mixed slurry is not clogged in the tower and does not accumulate on the shelf.
[0014]
The specific gravity separation tank 16 is connected to the lower part of the vacuum deaeration tower 15 by a line 29 via a second delivery pump 27, and one end of the line 29 faces underwater in the tank 16 and is connected to a disperser 49. The disperser 49 includes a plurality of slurry discharge ports (not shown) and is configured to disperse the slurry in the width direction of the specific gravity separation tank 16 toward an overflow weir 52 described later. The specific gravity separation tank 16 requires a certain opening area to reliably separate the heavy fluff group and the light fluff group charged into the specific gravity separation tank 16 for the following reasons. That is, if the opening area is not sufficient for the input amount of the heavy fluff group and the light fluff group, the heavy fluff group and the light fluff group charged into the specific gravity separation tank 16 are moved downward from the water surface of the tank. As a result, the light fluff groups in the layer that should float on the water surface are prevented from rising to the water surface by the heavy fluff groups, and conversely the heavy fluff groups in the layer that should sink in the water. This is because the light fluff group prevents sedimentation in water.
[0015]
On the other hand, the volume of the mixing and stirring tank 14 is preferably as small as possible in order to ensure the mixing and stirring effect as described above. Therefore, it is practically impossible to combine the mixing and stirring tank 14 for degassing the waste plastic and the specific gravity separation tank 16 for separating the waste plastic into one tank.
In the upper region of the specific gravity separation tank 16, three rows of sprinkler bottles 44 extending in the tank width direction are arranged in the longitudinal direction of the tank, and recovered water, which will be described later, is supplied to each bottle through a line 50. The water is configured to drop downward from the hole 46 provided in the lower part of the bowl toward the water surface of the tank. In addition, as long as water can be dropped from the top of a tank, the structure of a porous elongate pipe may be sufficient. An overflow weir 52 is attached to the liquid level at the leading end in the flow direction of the specific gravity separation tank 16, and a light fluff group floating on the water surface is sent to the weir 52 together with overflow water. The overflow weir 52 is connected to a light fluff group dehydrator 20 described later.
[0016]
Further, a heavy fluff group guide mechanism 48 extending along a bottom surface 54 inclined downward in the flow direction is installed in a lower area of the specific gravity separation tank 16. The heavy fluff group guide mechanism 48 includes a rotating shaft 48a extending substantially in parallel with the bottom surface 54 over substantially the entire longitudinal direction of the tank, and a spiral blade extending substantially over the entire longitudinal direction of the tank fixed to the rotating shaft 48a. 48b and a rotary drive motor 48c connected to one end of the rotary shaft 48a. By this guide mechanism 48, the heavy fluff group that has sunk on the bottom surface is guided to the longitudinal advance side of the tank and is sent to a reservoir 56 provided at the tip. A submersible pump 58 is installed in the reservoir 56, and the accumulated heavy fluff group is sent out of the tank via the line 60 and sent to the heavy fluff group dehydrator 18 described later. Note that the number of turns of the spiral blade, the pitch angle, and the like may be appropriately selected depending on the amount of settlement of the heavy fluff group, the inclination angle of the bottom surface, and the like.
[0017]
Incidentally, if the shape of the specific gravity separation tank 16 can ensure a predetermined opening area, the overall shape thereof can be selected as appropriate, for example, the set-up heavy fluff group is scraped with a screw, or the bottom of the tank or In order to provide a discharge port for discharging the settled heavy fluff group on the side portion, it can have a desired shape.
The heavy fluff group dehydrator 18 and the light fluff group dehydrator 20 are well-known types, and as long as they are useful for reducing thermal energy in the next drying step, a compression type or a centrifugal type can be selected as appropriate. Good. Under the light fluff group dehydrator 20, a circulation tank 62 is provided to collect the dehydrated water, and further through the lines 50 and 68 through the circulation water pump 64 and the watering pump 66, respectively, the mixing and stirring tank 14, It is designed to be supplied to the water sprinkler 44.
[0018]
The operation of the waste plastic specific gravity separator 10 having the above-described configuration will be described below.
First, waste plastic fluff crushed to an appropriate size and shape is supplied from the supply silo 1 to the mixing agitation tank 14 (arrow A), and water is supplied so that a slurry with a predetermined concentration is formed (arrow B) The mixture is stirred in the mixing and stirring tank 14 by the stirrer 22. By the stirring operation by the stirrer 22, the fluff is degassed and mixed with water to become a suspended state, thereby forming a mixed slurry. At this time, in the mixing and stirring tank 14, separation between the heavy fluff group containing vinyl chloride and the light fluff group containing polyethylene is prevented. That is, the plastic fluff is discharged from the lower part of the mixing and stirring tank 14 by mixing and stirring and sent to the vacuum degassing tower 15 through the first pump 21. Is done.
[0019]
Next, the mixed slurry thrown in from the upper part of the vacuum deaeration tower 15 collides with the shelf 40 provided in the intermediate part while freely falling in the tower, and at the same time, the mixed slurry becomes droplets by the impact. Then, the vacuum pump 17 is degassed to about 10 to 100 torr. As a result, the air adhering to the surface of the heavy fluff group is removed, and hydrophilicity is acquired. The mixed fluff degassed under reduced pressure is forcibly sent out from the lower part of the vacuum tower by the stirrer 42 in the water filled in the lower part. Next, the mixed slurry having acquired hydrophilicity is pulled by the second pump 27 and carried into the specific gravity separation tank 16. The mixed slurry exiting the disperser 49 spreads in the width direction in the tank 16 and is divided into a light fluff group that rises and a heavy fluff group that sinks, and the light fluff group moves toward the overflow weir 52 at the other end. The heavy fluffs that are accompanied by being swung up and down by the falling water from the water sprinkling toy 44 on the way are separated. The light fluff group separated from the heavy fluff group is dehydrated by the light fluff group dehydrator 20 together with water through the weir 52 and recovered as a light fluff group (arrow C). The separated water enters the circulation tank 62 and is recirculated into the system by the watering pump 66 and the circulating water pump 64, respectively.
[0020]
On the other hand, the heavy fluff group that has settled in the specific gravity separation tank 16 is collected by the heavy fluff group guiding mechanism 48 and collected in the 56, sucked up by the submersible pump 58, dehydrated by the heavy fluff group dehydrator 18, and heavy fluff. Collected as a group (arrow D). The separated water is returned to the bottom of the specific gravity separation tank 16 via a line 68. The specific gravity separation process is thus completed.
In addition, the magnitude | size of the waste plastic fluff as a processed material and the particle size of particle | grains are not specifically limited. The size of the fluff is usually about 10 mm and the size of the particles is 5 mesh or less, and may be slightly larger or smaller than this.
Although the embodiments of the present invention have been described in detail above, various changes and modifications can be made within the scope of the present invention described in the claims. For example, the number of water sprinklers installed above the specific gravity separation tank may be appropriately selected according to the longitudinal length of the specific gravity separation tank, the flow rate of water in the tank, the amount of fluff in the tank, and the like. . In addition, the shelves installed in the vacuum tower promote the reduction of mixed fluff droplets by appropriately selecting the shape and arrangement so that the fluff passing through the vacuum tower is not blocked and the fluff does not accumulate. However, the deaeration time may be secured while improving the deaeration efficiency.
[0021]
Moreover, the vacuum deaeration tower as a pretreatment device for the specific gravity separation process, that is, the vacuum deaeration device, is a hydrocyclone that separates solid particles in a liquid by centrifugal force in that the apparent specific gravity is returned to the original specific gravity. It is valid.
[0022]
【The invention's effect】
As is apparent from the above description, according to the specific gravity separation apparatus for waste plastic of the present invention, specific gravity separation can be performed efficiently regardless of the form of waste plastic while suppressing an increase in the size of the entire apparatus.
In addition, by providing a shelf in the vacuum degassing tower, it became possible to improve the degassing efficiency by ensuring the degassing time while making the mixed slurry falling freely in the tower small. .
Furthermore, by simply providing a sprinkling basin that is simple and inexpensive in the upper area of the specific gravity separation tank, the heavy fluff group that should be submerged in water is submerged, and the light fluff group that should originally float in water is steadily floated. As a result, the specific gravity separation efficiency by the specific gravity separation method can be further improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a specific gravity separator for waste plastic according to the present invention.
FIG. 2 is a schematic view of a prior art waste plastic specific gravity separator.
[Explanation of symbols]
10 Specific gravity separator
14 Mixing tank
15 Vacuum deaeration tower
16 Specific gravity separation tank
17 Vacuum pump
18 Heavy fluff group dehydrator
20 Light fluff group dehydrator
22 Stirrer
40 shelves
44 Sprinkler
62 Circulating water tank

Claims (3)

In a specific gravity separation device for continuously supplying and separating waste plastic using a specific gravity difference of various plastics contained in the waste plastic, the waste plastic is crushed on the upstream side of the specific gravity separation device. A mixing agitation tank for supplying and stirring a waste plastic fluff including light heavy fluff groups and water, a vacuum deaeration tower for degassing the mixed slurry sent from the mixing agitation tank, and a waste plastic A specific gravity separation tank for floating the light fluff group in water and sinking the heavy fluff group in water, and one end of a line connecting the vacuum degassing tower and the specific gravity separation tank is the specific gravity separation tank Specific gravity separator characterized by facing underwater . The vacuum degassing tower has an upper inlet for charging the mixed slurry, and a shape that substantially covers the cross-sectional area in cooperation with each other, with a predetermined interval in the longitudinal direction of the vacuum degassing tower. The specific gravity separation device according to claim 1, wherein the specific gravity separation device includes a plurality of stages of the arranged shelves from the upper part toward the lower part. One of the pair of shelves has an umbrella shape with a sharp upper portion disposed at a substantially central portion in the cross section of the vacuum degassing tower, and the other of the pair of shelves is an inner peripheral surface of the vacuum escape tower The specific gravity separation device according to claim 2 , wherein the specific gravity separation device is disposed over the whole and has an annular shape with a reduced diameter downward.

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