Correlations between segregation intensity and material properties such as particle sizes and adhesions and novel methods for assessment

Abstract

Assessment of powder segregation is essential in most powder-based industries when homogeneity of the powder is a concern. This study focuses on exploring correlations between segregation possibilities of the powders with a wide size range and some common material properties such as particle size, size ratio and adhesion, so that a simple method for assessing segregation intensity of a powder just based on the material properties can be developed, although the current study is designed for surface rolling segregation only.In this study, eight blends were made from different grades of calcium carbonate, which were selected based on different particle size ranges and particle adhesions. Segregation of a sample was determined by measuring segregation index, which was defined as a ratio of fines concentration change between segregated samples at the top and bottom sections of a surface segregation tester and the averaged concentration. Particle size distributions of the blended samples were measured before segregation tests and then the segregation tests were completed for the same blends. Powder adhesion of the virgin blends was also examined and represented by measuring the “bond number” using a mechanical surface energy tester developed at the Wolfson Centre.The experimental results showed correlations between the segregation index and the material properties such as particle size, size ratio and bond numbers, and was fitted to multiple empirical functions. With the correlations determined, novel methods for assessing surface segregation have been developed; one method considers just the particle sizes and the other one considers both particle sizes and particle adhesion identified by the bond number.