Performance evaluation of a dense-medium cyclone using alternative silica-based media

Abstract

The production of superior metallurgical-grade silicon requires the use of ultra-clean coal containing <1.5% ash with no iron contamination. The magnetite suspension utilized for coal cleaning in a dense-medium cyclone (DMC) is a detrimental impurity in the final coal product that dramatically diminishes the purity of silicon. A prior study has demonstrated that several silica-based materials may be suitable alternatives that eliminate iron contamination. To further improve the separation performance and evaluate the silica-based media, DMC separation tests were conducted based on a statistically designed program to identify the role of various operational parameters (i.e. medium relative density, silica media blend ratio, and cyclone apex diameter) in maximizing organic efficiency and minimizing low-density bypass. An ideal medium composition with a bimodal particle size distribution considerably improves medium stability properties while also eliminating the undesirable effects of apex diameter on the DMC separation efficiency. Low-density cutpoints (<1.35) are hindered by medium instability, but these issues can be rectified by increasing the amount of fine media particles or decreasing the apex diameter.