Fast food restaurant and cafeteria waste in addition to containing large amounts of PSF also commonly comprises a large proportion of paper products (such as bags, cups and napkins), wax-coated paper products, condiment containers, plastic eating utensils and food morsels.
Recycled polystyrene foam can be used to manufacture a wide variety of products such as plant pots, plastic desk organizers, foam construction insulation etc. and is therefore, a valuable product. Further, polystyrene foam, like most plastic, takes a very long time to degrade when placed in landfills. Therefore, it is desirable to recycle polystyrene foam to reduce the amount of such plastic in municipal landfills.
FLAIL MILL(Helylpatterson Inc.)
The waste is then continuously fed into an air classifier. In a preferred embodiment, the air classifier is a large rotating cylinder which uses an air stream to carry lighter materials, such as napkins and PSF through the cylinder, while the heavier waste, primarily wax coated containers and remaining food, drops out of one end of the classifier and is removed from the primary stream of waste. The light fraction output of the air classifier, which comprises primarily PSF and paper, is fed into a plenum chamber where the air velocity is reduced allowing the light fraction waste to settle to the bottom of the chamber.
The light fraction waste is then continuously delivered to a reversible conveyor which can bring the waste either to a batch pulper or a continuous pulper. Either of the pulpers essentially mixes the waste with water and vigorously agitates the mixture so as to break down the paper waste to paper pulp. The water and paper pulp is then separated from the PSF by passing the mixture through a screen which allows the water and paper pulp to pass through but retains the larger PSF waste particles. The PSF is air conveyed from the screen to a granulator. The particle size is further reduced in the granulator.
The PSF is then dried and prepared for shipment. The paper pulp and water which passes through the screen is pumped to a static sieve where the water and paper are partially separated. The water is then recovered and recycled back into the apparatus. The paper pulp is further fed through a de-watering screw where additional water is removed and recycled.
The de-watered paper pulp is then collected in containers and can be sold for recycling. The undersized waste removed in the rotating trommel and the "heavy" waste removed in the air classifier is combined and delivered to a shredder where the size of the waste is further reduced. The output of the shredder is sent to a pellet mill, which compresses the waste and extrudes it into small pellets. To ensure that the pellets do not readily crumble, they are air cooled in a pellet cooler before storage.