Leaching of coals with subcritical water

The effects of subcritical water and organic acid additives on the leaching of three low-rank Turkish coals, can Tuncbilek, and Soma which have high ash and moderate sulfur contents were investigated. Test variables included temperature, pressure, and concentrations of organic acids. It was observed that temperature had a strong effect on the removal of ash and sulfur while pressure had a small effect. The best removal of sulfur was observed when organic acid solutions were used at 200 degrees C and 70 atm. The best removal of ash was observed by using 1 M bortrifluorid (BF3) solution at 250 degrees C and 70 atm. Depending on the leaching conditions and coal used, reductions ranged from 5% to 36% in sulfur and 5% to 59% in ash content.