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What is a Gravity Separation Tank?
The gravity separation tank serves two purposes:
Cleaning: Immerse the plastic film in water in a large tank to loosen debris.
Separation: Loose debris and heavier contaminants will sink when the plastic film floats. The top layer continues to the next step in the washing line while removing sunken particles.
The gravity separation tank also called the floating / sink tank, is a large rectangular tank. The water is on the top and will keep lossing and evaporating, so it needs to be continuously replaced. The plastic film enters the separation tank and is pushed forward in the lengthwise direction by a slowly rotating paddle drum, and sometimes by a tap water nozzle.
When the plastic film is soaked and bathed in this large water tank, debris and other contaminants sink to the bottom, while the plastic film floats and advances. The device uses the basic characteristics of water and its density to assist the separation. The density of water is 1 g / cm3, any object with a density less than this density will float, and any object with a density greater than water will sink. And the density of plastic LDPE film is about 0.9 g / cm3, so it will float. The rock, sand and gravel through the granulator and friction washer will be cleared because their density is much larger than the water.
This makes gravity separation an important part of any plastic film cleaning line. Actually due to polyethylene (made of ldpe film or low density polyethylene) and polypropylene have a density of less than 1 g / cm3, so it is good that other films which not made of polyethylene and polypropylene will be removed.
The bottom of the separation sink is tapered, and all sinking waste will be collected there and will finally removed by a screw / belt conveyor or flusher mounted on a tilt valve or pneumatic valve. The wastes just collected are mainly composed of water and dirt and will be finally buried or professionally landfilled.
Hydrocyclones
The hydrocyclone is for recycling PET bottles commonly, and can also be used for cleaning plastic films. Its function is the same as the purpose of the separation tank. In the separation tank, the plastic film can be separated in a more effective way from the heavier pollutants. In hydrocyclones, pressure jets are superior to the water mixture of membranes and contaminants in cylindrical equipment. The resulting cyclone pushes the lighter plastic film upward and outward, while the heavier pollutants move inward and downward. The sensitivity and selectivity of the cyclone separator can be adjusted by selecting the nozzle size at the top and bottom outlets.
Whether using a separation tank or a hydrocyclone, the plastic film will finally become very clean, free of pollution, and ready for dehydration and drying.
Cleaning: Immerse the plastic film in water in a large tank to loosen debris.
Separation: Loose debris and heavier contaminants will sink when the plastic film floats. The top layer continues to the next step in the washing line while removing sunken particles.
The gravity separation tank also called the floating / sink tank, is a large rectangular tank. The water is on the top and will keep lossing and evaporating, so it needs to be continuously replaced. The plastic film enters the separation tank and is pushed forward in the lengthwise direction by a slowly rotating paddle drum, and sometimes by a tap water nozzle.
When the plastic film is soaked and bathed in this large water tank, debris and other contaminants sink to the bottom, while the plastic film floats and advances. The device uses the basic characteristics of water and its density to assist the separation. The density of water is 1 g / cm3, any object with a density less than this density will float, and any object with a density greater than water will sink. And the density of plastic LDPE film is about 0.9 g / cm3, so it will float. The rock, sand and gravel through the granulator and friction washer will be cleared because their density is much larger than the water.
This makes gravity separation an important part of any plastic film cleaning line. Actually due to polyethylene (made of ldpe film or low density polyethylene) and polypropylene have a density of less than 1 g / cm3, so it is good that other films which not made of polyethylene and polypropylene will be removed.
The bottom of the separation sink is tapered, and all sinking waste will be collected there and will finally removed by a screw / belt conveyor or flusher mounted on a tilt valve or pneumatic valve. The wastes just collected are mainly composed of water and dirt and will be finally buried or professionally landfilled.
Hydrocyclones
The hydrocyclone is for recycling PET bottles commonly, and can also be used for cleaning plastic films. Its function is the same as the purpose of the separation tank. In the separation tank, the plastic film can be separated in a more effective way from the heavier pollutants. In hydrocyclones, pressure jets are superior to the water mixture of membranes and contaminants in cylindrical equipment. The resulting cyclone pushes the lighter plastic film upward and outward, while the heavier pollutants move inward and downward. The sensitivity and selectivity of the cyclone separator can be adjusted by selecting the nozzle size at the top and bottom outlets.
Whether using a separation tank or a hydrocyclone, the plastic film will finally become very clean, free of pollution, and ready for dehydration and drying.
Reference: PRM
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