Coal cleaning: Progress and potential

Results from a detailed analysis of sulfur dioxide (SO)2 reductions achievable through “deep” physical coal cleaning (PCC) at 20 coal‐fired power plants in the Ohio‐Indiana‐Illinois region are presented here. These plants all have capacities larger than 500 MWe, are currently without any flue‐gas‐desulfurization (FGD) systems, and burn coal of greater than 1% sulfur content (in 1980). Their aggregate emissions of 2.4 million tons of SO2 per year represent 55% of the SO2 inventory for these states. The principal coal supplies for each power plant were identified and characterized as to coal seam and county of origin, so that published coal‐washability data could be matched to each supplier. The SO2 reductions that would result from deep cleaning (Level 4) and moderate cleaning (Level 3) of each coal were calculated using a PCC computer model. For deep cleaning, percentage reductions in sulfur content ranged from zero to 52%, with a mean value of 29%, and costs ranged from a low of $364/ton SO2 removed to over $2000/ton SO2 removed. Because coal suppliers to these power plants employ some voluntary coal cleaning, the anticipated emissions reduction from current levels if deep cleaning were used should be near 20%. These emissions reductions were projected using conventional coal‐cleaning‐circuit designs. The basic elements of typical commercial PCC designs are briefly described, and current research and development activities in physical, chemical, and biological desulfurization of coal are reviewed. Possible governmental actions to either encourage or mandate coal cleaning are identified and evaluated.