| The purpose of this research is to provide a basis for improving the recovery and grade of coal in the beneficiation of raw coals, giving particular attention to western coals. Increased amounts of mineral matter will be liberated by the controlled crushing of coal, but the fines produced are more difficult to process. Many coal preparation plant operators are incapable of recovering coal finer than 100 (mu)m in diameter, forcing them to discard many millions of tons of clean coal yearly. In many coal and mineral beneficiation systems, processes which effect separation by modifying and exploiting surface chemical differences between the mineral values and the gangue material have demonstrated their technical and economic efficacy. This research addresses the processing of fine western coals by two surface chemical methods, froth flotation and selective oil agglomeration.; Nine western coals from Utah, Colorado and Wyoming, ranging from subbituminous, class C to high-volatile bituminous, class A, were selected for study. These coals were characterized with respect to chemical and physical structure and wettability. The flotation responses of the coals were determined and correlated with chemical composition. Excellent correspondence was found between concentrations of the principal oxygen-containing functional groups, phenolic and carboxyl, and flotation responses for the nine coals. The flotation response also correlates well with coal rank, and it is concluded that the much poorer flotation behavor of the subbituminous coals (as compared to high-rank coals) is principally due to their higher concentrations of phenolic anc carboxylic oxygen.; Agglomeration flotation is the combination of agglomeration followed by froth flotation. It was found that by using viscous oils in amounts of less than 1 percent (10 kg oil per ton coal), coal slurries could be effectively cleaned with over 90 percent combustible material recovery. At this level of recovery, a synthetic "blackwater" containing 55 percent ash was cleaned to less than 10 percent ash usng waste motor oil at a dose rate of 0.3 percent (3 kg per ton coal). Because of their high selectivities, processes utilizing differences in surface chemistry are destined to become very important in coal processing. |
