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Precombustion Removal of Hazardous Air Pollutant Precursors
Kohmuench, Jaisen Nathaniel
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The 1990 Clean Air Act Amendment (CAAA) contains provisions that will establish new emission standards for 190 potentially hazardous air pollutant precursors (HAPPs). Studies have suggested that many of these HAPPs have the potential to be removed prior to combustion. This thesis details the findings of a bench-scale test program that was implemented to evaluate the capabilities of physical coal cleaning technologies on the removal of trace elements from coal. Test work was completed on Pittsburgh No. 8 seam coal that was processed using physical cleaning techniques (i.e., crushing, dense media separation, froth flotation, and enhanced gravity separation). The bench-scale test circuit incorporated crushing and rewashing a coarse, mid-density product with hopes that trace element rejections would improve due to greater liberation of HAPPs. The results of this investigation showed that trace elements were predominately rejected in the coarse coal portions of the processing circuit (i.e., dense media separation), and only slight improvements in rejections could be realized from crushing any portion of the coal. It was also shown that trace element rejection could be incrementally increased with minimal loss of total yield or combustible recovery when froth flotation is put in series with enhanced gravity separation. The results of the bench-scale test work, along with trace element float-sink and release analysis data, were used to develop a simulator that can predict trace element rejections from any coal processing circuit. This was achieved by applying general partition functions to trace element washability and bench-scale processing data. Simulation studies included comparing three physical coal cleaning techniques. The results of these analyses showed that although no net improvement in trace element rejection can be gained through crushing the circuit feed, there is a slight increase in product yield. Crushing a mid-density coarse coal product also showed little or no improvement in trace element rejection.
- Masters Theses