Dry coal cleaning using the FGX separator

The extraction of coal typically results in the recovery of pure rock that ranges from very small to very large quantities depending on the seam thickness and other characteristics. In the eastern U.S. coalfields, a significant amount of out-of-seam rock is being extracted in order to recover coal from relatively thin seams. As a result, the amount of run-of-mine feed that is rejected as rock material at the coal cleaning plant can range from 50%-70%. The haulage, processing, and storage of the rock represent significant energy inefficiency and high operating costs. Removing the pure rock material near the extraction point would provide significant economic and environmental benefits. The removal of pure rock using a relatively high-density separation of around 2.0 is referred to as "deshaling". Wet-based technologies are the most commonly employed cleaning units for removing rock from coal; however, these processes are generally massive and immobile, while also requiring water addition and a slurry treatment system. This study focused on evaluating a novel dry separation technology, the FGX Separator, at several coal mining operations throughout the U.S. The FGX Separator applies table concentration principles using air as the medium. Parametric evaluations were conducted at nearly all tests sites using a 3-level experimental design in an effort to realize optimum performances. Regardless of coal type, table frequency and longitudinal slope were found to be the most critical factors in controlling product ash content over a range of energy recovery values. Additionally, the amount of fluidization of air applied through the deck was critical for ensuring optimum energy recovery.