Pre-combustion cleaning of pulverized fine coal at power plant using novel RTS dry separation technology

Coal cleaning technologies are vitally important for producing clean coal to supply abundant and affordable energy for the nation's economy under the increasingly stringent environmental regulations. They are generally categorized into pre-combustion and post-combustion processes. Coal cleaning prior to combustion is often accomplished using wet physical processes at coal preparation plants. However, the resultant coal product still contains a significant amount of impurities such as ash, sulfur, mercury that are not well liberated from coal particles mostly in the size range of several millimeters to inches. The pulverization of coal prior to combustion at the power plant provides an ideal feed of well liberated fine coal particles for physical cleaning. If a cost-effective dry separation process is developed to further clean pulverized fine coal at the power plant prior to its combustion, the cost of expensive post-combustion chemical cleaning processes such as flue gas scrubbing can be reduced considerably. In this study, a novel rotary triboelectrostatic separator (RTS) was investigated for dry cleaning of pulverized Illinois fine coal samples. The proprietary RTS technology is characterized by an innovative high efficiency rotary charger, charger electrification, laminar air flow, and specially designed electrodes. The separation performance of this technology was evaluated in terms of ash content reduction as well as mercury and sulfur content reduction. Important process parameters such as charger material, potential and rotation speed, feed flow rate and air flow rate were investigated for their effects on the separation performance.