Bulk solid conveying screw conveyors

Different conveyors such as the belt, chain, and screw types, as well as pneumatic equipment, are used to transport bulk powdered foods. Conveyor belts are used for movement of different types of bulk solids at long distances. The belt and its load are supported on idlers on both conveying and return sections. The material can be discharged over the end of the belt either by using a diagonal scraper, by tilting one or more of the idler pulleys, or by using a tripper. 

There are a number of ways to feed an air-assisted gravity conveyor. The most common feed method is simply a flood feed from a mass flow hopper. A non-mass flow hopper may cause problems with inconsistent feed which may result in blockages. That is, if too much material is fed onto the conveyor, then there will be insufficient air to fluidise the material, and if too little material, or none at all, then conveying may halt due to a maldistribution of air from the plenum chamber. While an air-assisted gravity conveyor does not work independently as a feeder, if the bulk solid is metred onto it by the use of a screw feeder or rotary valve, it will then convey this material at a constant rate. Another method of controlling the flow of material is to use a gate or baffle at either end of the conveying duct. 

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