Feed zone screw cooling

This barrier screw appears similar to that in descrihed [13]. With screw pitch decreased within the feed zone, air cooling is sufficient to control the feed zone temperature. Shearing elements plus a pin/pineapple mixer follows the barrier melting zone. 

Feed Zone This is the part of the screw that picks up the plastic at the feed opening (throat) plus an additional portion downstream. Many screws, particularly for extruders, have an initial constant lead and depth section, all of which is considered the feed section. This section can be welded onto the barrel or a separate part bolted onto the upstream end of the barrel. The feed section is usually jacked for fluid heating and/or cooling. 

A screw conveyor feeds through a cooled downpipe the electrically heated quartz-reactor which has a diameter of 5 cm and a fluidizing zone of up to 8 cm. The fluidizing gas is about 500 1/h of either nitrogen or circulated cracker gas. A cyclone separates solids from the hot pyrolysis gas stream an electrostatic precipitator and a system of intensive coolers and hydrocyclones condense the liquid portions of the cracked products, The non-condensable pyrolysis-gases are measured. 

The feed zone has the most effects on solid conveying of the resin. Three coefficients of friction take place, namely friction between barrel and pellet, between pellet and pellet, and between root of the screw and pellet. Solid conveying is the process wherein the material must stick to the barrel and slip on the screw. Hence, cooling root of screw will reduce the coefficient of friction between the screw and the plastic pellets. Screw cooling should be installed in the core of the screw in the feed section to give another zone of temperature control on the extruder. 

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