Biochemical removal of HAP precursors from coal - INEEL slurry column testing

A combined physical/biochemical process for the precombustion removal of 13 inorganic hazardous air pollutant (HAP) precursors, i.e., Sb, As, Be, Cd, Cr, CI, Co, F, Pb, Hg, Mn, Ni and Se, from coal was tested. Biochemical pro cesses for removal of HAP precursors from coal potentially offer advantages of deeper cleaning, more specificity, and less coal loss. The slurry colum n is a second-generation process for the beneficiation of fine (60-mesh x 1 0-mu m) coal by a combination of physical separation of mineral matter and biooxidation of pyrite. Sixty-seven percent removal of pyrite from a 60-mes h Pittsburgh #8 coal was achieved at a 35% (w/w) slurry concentration and a five-day reactor residence time. Ninety per-cent of the hearing value of t he feed coal was recovered. Among the HAP precursors of most concern, over half of the Se, As and Hg were removed from the feed coal. From 40% to 70% of most HAP precursors were removed from the feed coal. Hg in the feed coal was reduced from 0.12 to 0.054 mu g in the product coal, while waste coal contained 0.24 mu g/g.