Advanced development of fine coal desulfurization and recovery technology. Quarterly technical progress report, April 1, 1977--June 30, 1977

Abstract

The improvement and technical development of several promising methods for desulfurizing and recovering fine coal were continued. These methods include froth flotation, selective oil agglomeration, pelletization, and a chemical desulfurization process which involves leaching fine coal with a hot dilute solution of sodium carbonate containing dissolved oxygen or air under pressure. Numerous laboratory experiments and measurements were carried out to advance the state of this technology. It was shown that the chemical leaching process removed most of the inorganic sulfur from several high sulfur coals as well as a significant amount of organic sulfur from some of the coals. Higher temperatures and/or oxygen partial pressures resulted in more organic sulfur being removed in some instances. Also it was shown that the rate of conversion of pyrite to soluble sulfates depends on particle size and alkali concentration as well as oxygen partial pressure and flow rate. In addition the effectiveness of a chemical pretreatment step for improving the separation of coal and pyrite by oil agglomeration was demonstrated. Among various fuel oils tested for agglomerating coal, No. 1 or 2 provided greater sulfur reduction than No. 5 or 6. Also the lighter fuel oils seemed better suited to agglomerating finely groundmore » coal. However, No. 6 fuel oil was adapted to the agglomeration of ball milled coal by diluting it with a lighter oil. Construction was started on a bench-scale flow system for demonstrating the beneficiation and recovery of fine-size coal by various methods. Furthermore the suitability of the ASTM method for determining pyritic sulfur in coal was confirmed for certain high volatile C bituminous coals. Confirmation was obtained by scanning electron microscope/energy dispersive x-ray analyses.« less