Cleaning of Coal Using an Integrated Grinding-Flotation Column System

Improved pyritic sulfur and ash reduction was obtained by using an advanced column flotation system that integrates grinding and flotation operations in a single stage. The column was tested with Illinois No. 6 coal (minus 60 mesh) containing 36.6% ash and 3.5% total sulfur, out of which pyritic sulfur accounted for 2.03%. Using designed experiments, a bilinear response surface was fitted describing the main and interactive effects of selected variables on grade and recovery of clean coal. Tests performed on Illinois No. 6 coal utilizing effective operating conditions provided a clean coal with 6.61% ash and 0.70% pyritic sulfur. The process removed 84% of the ash, 66% of the total pyritic sulfur (88% of the liberated pyritic sulfur) with over 90% recovery of the fine coal.