Determination of Forms of Sulfur in Coal

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Abstract
Widespread interest in reducing the sulfur content of coal has increased the need for chemical determinations of the forms of sulfur: sulfate, pyritic, and organic. The proper use and application of methods of determining the forms of sulfur in coal and coal refuse, including interpretation of results, can pose serious problems; consequently, a report and discussion of current methods of analysis, including instrumental methods, should prove helpful. A review of the evolution of current ASTM sulfur standards is presented, and a critical examination is made of problems associated with the determination of the varieties of sulfur in coal. Results of instrumental, oxidation, and reduction methods are given to show that close agreement among the three can be obtained and that calculation of organic sulfur by difference is reasonably accurate. The dangers of applying these methods to the determination of forms of sulfur in coal-related materials (e.g., high-ash fractions from float-sink procedures) are illustrated by data from a washability study of 64 coals.