Study on fine powder discharged from hoppers modified with insert

Abstract

The use of inserts in the hopper provides a reliable way to improve the quality of powder flow. In this work, glass beads, fluidized catalytic cracking catalyst (FCC), lignite and polyvinyl chloride (PVC) were used as experimental materials and the flow properties of powders were characterized by the FT4 powder rheometer and the PT-X powder tester. Discharge experiments on a Perspex hopper at a laboratory scale are presented in this paper, comparing the flow characteristics of fine powders discharged from a plain hopper and from hoppers modified with the use of inserts of different geometries. Effects of insert and powder properties on powder flow rate are discussed. A mechanism model is developed to describe the hindering effect to the discharge consequent to the powder expansion at the hopper outlet. Mechanisms of insert on powder flow are analyzed. It is demonstrated that the higher flow rates of the hopper operating with a solid insert are due to the anticipated expansion of the material generated by the presence of the insert. The hopper with a hollow insert shows a flow sequence and the values for the powder flow rates are averaged values between two regimes. Based on understanding above mechanisms, powder flow rates for plain hopper and hoppers modified with insert are successfully predicted.