ADVANCED DEVELOPMENT OF FINE COAL DESULFURIZATION AND RECOVERY TECHNOLOGY Quarterly Technical Progress Report Oct. 1, 1977 to Dec. 30, 1977nDivision of Materials & Exploratory Research

摘要

Several promising methods for the desulfurization and recovery of fine coal were subjected to further improvement and development. The methods include froth flotation, selective oil agglomeration, pelletization, and a chemical desulfurization process based on leaching coal with a hot, dilute solution of sodium carbonate containing dissolved oxygen under pressure (oxydesulfurization.) Numerous experiments with chemical leaching in an autoclave showed the effect of leaching time, oxygen partial pressure, temperature, and concentration of alkali on the reduction of sulfur in coal. Increased oxygen partial pressure and leaching time improved the removal of sulfur. An optimum temperature range was observed for maximum sulfur reduction. Coal-derived pyrite was leached in a tubular, flow-through reactor. The conversion of sulfur as a function of the length of the packed bed was studied. Chemical treatments of the surface of coal and pyrite were studied to effect a better separation by froth flotation and oil agglomeration. Treatment of acid-cleaned pyrite by an aerated alkaline solution de¬creased its floatability, whereas the floatability of coal was unaffected. Oil agglomeration was also effective in the reduction of sulfur content in coal when a mixture of No. 200 LLS and No. 6 fuel oils was used after a pretreatment with a hot, aerated solution of dilute sodium carbonate. The construction of a bench-scale flow system for demonstrating various methods of cleaning and recovering fine-size coal was continued and is nearing completion. The determination of sulfur in coal by the ASTM procedure was examined to assess the effect of the maceral type and coal rank on the dissolution of pyrite by nitric acid. The study was based on data obtained by scanning electron microscopy and energy-dispersive X-ray analysis.