Methods for Minimizing Segregation: A Review

Abstract

Segregation, as a common problem in particulate material industries, has been studied by many researchers from different science and engineering disciplines within academia and numerous industries. Various patterns and factors influencing segregation, as well as corresponding methods to minimize segregation, are discussed in this article. Universal methods used to minimize segregation mainly include improvement of material properties (i.e., narrowing size distribution spread, reducing absolute size, and avoiding irregularly shaped particles), proper selection of handling equipment and operational parameters (i.e., lowering free-fall height and employing mass flow bins), and proper control of material handling environmental conditions (i.e., minimizing vibration and maintaining humidity). For various material handling processes such as filling/deposition, discharging, conveying, and mixing, appropriate methods exist. For instance, various inserts have been used to minimize segregation during filling or discharging processes. Based on detailed review in this article, four fundamental segregation mechanisms—trajectory, sieving, fluidization, and agglomeration—have been identified. In addition, the current limitations identified precluding advancement of research on segregation include: (1) application-oriented research that limits researchers from capturing the larger picture of segregation; (2) use of ideal experimental materials that prevent the application of test results to industrial processes; and (3) all segregation measurements conducted so far being restricted to time-independent conditions described by a coefficient that is clearly not applicable to the entire time-varying process. To overcome these limitations, the second-generation primary segregation shear cell (PSSC-II) with novel and flexible design features models the sieving and percolation segregation mechanisms. This new approach could serve as an example to develop similar testers and much needed multi-scale constitutive models for the other three fundamental segregation mechanisms.