Ryoji Utsumi

An attrition test with a sieve shaker for evaluating granule strength

The purpose of this study is to establish a method for evaluation of the strength of fragile granules such as ferric oxide granules produced by spray pyrolysis from an acid solution of a metallic salt. To examine if they have enough strength to maintain their shape throughout the handling process, and at the same time, enough weakness to break down easily during a specifically designated processing. An attrition test using a Ro-Tap sieve shaker, which is usually used for particle size analysis, was employed. An attrition rate equation was derived from the attrition mechanism of granules on a sieve; a method for the evaluation of strength based on the attrition equation is presented.

Attrition testing of granules with a tapping sieve

Granules produced to overcome powder handling difficulties must retain their shape during storage or transport but, on the other hand, be easily broken down during designated process. Commonly, granule properties have been evaluated for several properties such as flowability, bulk density, and so forth; however, shape retention and fragility have not yet been evaluated. This study examines whether fragility can be evaluated with attrition tests. We carried out attrition tests with a tapping device on ferric oxide granules and followed the progression of the attrition with time. The attrition mechanism was expressed with an attrition-rate equation with two constants. We showed that these two constants are useful for characterizing the attrition of the granules used in the experiments.