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What is a Squeezer?
The final step of plastic film recycle is the drying process. The wet plastic film needs to be dried before being extruded into plastic pellets, which is the final step in the plastic film recycling process. During the extrusion process, the plastic film is melted into a continuous stream of molten polyethylene plastic and extruded through a die (similar to how spaghetti is made), and then cut into pellets or granules. If the plastic film is not properly dried before
extrusion, moisture will be trapped in the molten plastic, thereby creating bubbles in the final particles. To ensure that this does not happen, the moisture content must be controlled below 15%.
There are two accepted methods for drying plastic films in cleaning lines. The first and more common method is through a dehydrator or horizontal centrifuge with a thermal heater. The dehydrator removes excess water by centrifugal force. Effective to a certain extent, dehydration will bring the moisture content of the wet plastic film to about 20-30%. The rest of the water is removed by a thermal dryer, just like a hair dryer.
The second method is more economical, it uses a screw press to mechanically squeeze and twist the plastic film. The resulting film is usually dried enough to extrude about 15%.
Dewatering / Thermal Heater
The manufacture of a dehydrator or horizontal centrifuge is very similar to a high-speed friction washer. In the center of the dehydrator, there are many panels or paddles, which are mounted on a shaft, which rotates at a high speed of about 1,000 revolutions per minute. Around this fast axis of rotation is a screen tunnel. The entire device is housed in a metal container, and the motor is installed in the metal container from the outside.
When the wet plastic film enters the dewatering machine, the spinning plate will centrifugally force the plastic film around the mesh screen and throw it towards the mesh screen. At this time, excess water will flow out through the mesh screen, and the plastic film will be contained in it.
The hot heater uses hot air to dry the plastic film. After dehydration, the plastic film is evacuated by a transport blower and mixed with hot air, which is wound back and forth through a long transport pipe. The plastic film is mixed and rotated in the long transportation channel until it enters the cyclone, where the residual moisture is further reduced. It is usually sufficient to use one set of heat heaters, but some washing plants may choose 2 or 3 heat heaters in a row to ensure that the moisture content is reduced as much as possible.
Dewatering Screw Press
Dehydration screw presses are commonly used in the fields of food processing, paper and pulp industry, sewage treatment, etc. This sturdy mechanical device has excellent dehumidification capacity without having to spend a high cost of thermal heaters (electricity).
The core of the dewatering screw press is a screw shaft with increasing diameter. The screw shaft is the narrowest at the opening where the plastic film first enters through the vertical feeder. The screw shaft is surrounded by a thick-walled, constant-diameter outer tube lined with fine holes for drainage. The ordinary dewatering screw press for plastic film cleaning production line is 4-6 meters long, but it can be increased or decreased according to the application. When the wet plastic film is fed into the feeder, the screw shaft rotates slowly, moving the plastic film forward. As the diameter of the screw shaft becomes thicker, the plastic film becomes more and more close to the shell wall. The water in the plastic film is squeezed out and leaves the small holes.
At the end of the horizontal screw press, the diameter of the screw shaft is only slightly smaller than the inner diameter of the outer shell. The dried plastic film is discharged from the screw press through this narrow gap. A well-made screw press will reduce the moisture content to an acceptable level below 15%.
extrusion, moisture will be trapped in the molten plastic, thereby creating bubbles in the final particles. To ensure that this does not happen, the moisture content must be controlled below 15%.
There are two accepted methods for drying plastic films in cleaning lines. The first and more common method is through a dehydrator or horizontal centrifuge with a thermal heater. The dehydrator removes excess water by centrifugal force. Effective to a certain extent, dehydration will bring the moisture content of the wet plastic film to about 20-30%. The rest of the water is removed by a thermal dryer, just like a hair dryer.
The second method is more economical, it uses a screw press to mechanically squeeze and twist the plastic film. The resulting film is usually dried enough to extrude about 15%.
Dewatering / Thermal Heater
The manufacture of a dehydrator or horizontal centrifuge is very similar to a high-speed friction washer. In the center of the dehydrator, there are many panels or paddles, which are mounted on a shaft, which rotates at a high speed of about 1,000 revolutions per minute. Around this fast axis of rotation is a screen tunnel. The entire device is housed in a metal container, and the motor is installed in the metal container from the outside.
When the wet plastic film enters the dewatering machine, the spinning plate will centrifugally force the plastic film around the mesh screen and throw it towards the mesh screen. At this time, excess water will flow out through the mesh screen, and the plastic film will be contained in it.
The hot heater uses hot air to dry the plastic film. After dehydration, the plastic film is evacuated by a transport blower and mixed with hot air, which is wound back and forth through a long transport pipe. The plastic film is mixed and rotated in the long transportation channel until it enters the cyclone, where the residual moisture is further reduced. It is usually sufficient to use one set of heat heaters, but some washing plants may choose 2 or 3 heat heaters in a row to ensure that the moisture content is reduced as much as possible.
Dewatering Screw Press
Dehydration screw presses are commonly used in the fields of food processing, paper and pulp industry, sewage treatment, etc. This sturdy mechanical device has excellent dehumidification capacity without having to spend a high cost of thermal heaters (electricity).
The core of the dewatering screw press is a screw shaft with increasing diameter. The screw shaft is the narrowest at the opening where the plastic film first enters through the vertical feeder. The screw shaft is surrounded by a thick-walled, constant-diameter outer tube lined with fine holes for drainage. The ordinary dewatering screw press for plastic film cleaning production line is 4-6 meters long, but it can be increased or decreased according to the application. When the wet plastic film is fed into the feeder, the screw shaft rotates slowly, moving the plastic film forward. As the diameter of the screw shaft becomes thicker, the plastic film becomes more and more close to the shell wall. The water in the plastic film is squeezed out and leaves the small holes.
At the end of the horizontal screw press, the diameter of the screw shaft is only slightly smaller than the inner diameter of the outer shell. The dried plastic film is discharged from the screw press through this narrow gap. A well-made screw press will reduce the moisture content to an acceptable level below 15%.
Reference: PRM
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