Removal of trace elements from coal using a multiple-property processing circuit
The U.S. Environmental Protection Agency is conducting a three-year study of toxic air emissions specific to coal fired utilities to assess the potential health risks of trace elements released during coal combustion. Several trace elements in coal associate with the mineral matter while others associate with pyrite. Researchers at the Virginia Center for Coal and Minerals Processing have developed a multiple-property processing circuit capable of providing high rejections of ash-forming mineral matter and pyritic sulfur. Reductions were expected for trace elements associated with the mineral matter and pyritic sulfur in proportion to ash and pyrite reductions. Trace elements associated with the organic fractions of coal that may be more difficult to remove by physical cleaning are ideal candidates for removal by chelating agents. The purpose of this study was to determine whether trace elements can be effectively separated from coal using the circuit followed by chelating agents. Thirteen of the sixteen trace elements examined in this study were reduced (27-93%) in concentration by the circuit. EDTA further reduced (2-17%) the concentrations of several trace elements in the circuit product coals. EDTA was found to be effective at low concentration and without pH adjustment I providing a practical means for further reducing the concentrations of several trace elements beyond circuit processing.