CHARACTERIZING SEMI-COHESIVE POWDERS USING ANGLE OF REPOSE

When properly measured and interpreted angle of repose (AOR) can be a useful method of characterising a powder. Unfortunately, a multitude o f definitions and measuring equipment is used. A review of the inheren t problems is presented in the first part of this paper. The second pa rt of the paper describes the improvements made to a measuring device developed originally for measuring the angle of repose of soda ash, so that a wider range of powders can be tested. In the improved design, the tendency of cohesive and semi-cohesive powders to block the device 's funnel has been eliminated. A total of 73 powders consisting of fou r different materials, and covering Groups A, A/C and C of Geldart's c lassification, have been tested using the new equipment. The results s how that AOR increases systematically with decrease in mean particle s ize. Combination of AOR measured in the new device with aerated bulk d ensity provides a quick, sensitive and effective method for characteri sing a wide range of powders.