Effect of screw design on hopper draw down by a horizontal screw feeder

Screw feeders are used extensively in the food, plastics, household products, mineral processing and agricultural industries to remove material from hoppers and bins at a controlled rate. A key design requirement is to make the empty space in the screw available evenly along its exposed length below the hopper or bin. The evenness of the flow depends on the drawdown flow pattern, which in turn depends on the screw and hopper design, shape of the particles and wall friction effects. If the drawdown is not even then compositional variations in the outgoing stream can be created. The strongly varying residence time distributions for particles within the bin can also lead to quality issues. Designs to date have typically been based on analytical models and often performance issues are observed when the screw design used does not give the desired flow pattern. In this study the Discrete Element Method (DEM) is used to simulate particle transport in a horizontal screw feeder system for a range of conventional screw designs including variable screw pitch, screw flight and core diameters. The influence of screw design on the particle mass flow rate, the evenness of particle drawdown from the hopper and power consumption are investigated. The results of this study are able to better inform the design of screw feeders for specific materials. This has implications for product quality control, reduced power consumption and reduced wear on conveyer components