Chemical Removal of Pyritic Sulfur from Coal

Abstract

A new approach for the chemical removal of pyritic sulfur from coal is described. The process is based on the discovery that aqueous ferric salt selectively oxidizes the pyritic sulfur in coal to chemical forms which can be removed by vaporization, steam, or solvent extraction. Data for removal of the pyritic sulfur from four major coals (Lower Kittanning, Illinois No. 5, Herrin No. 6, and Pittsburgh) are presented together with a detailed discussion of the process chemistry. The effect of variables, such as coal particle size, acid and iron concentration, reaction time and temperature among others, are discussed. The results show that near complete removal of pyritic sulfur can be obtained under mild conditions, resulting in a reduction of the total sulfur content of the coals from 40 to 80 percent, depending on the original pyritic sulfur content. The current development effort is being accomplished under support from the Environmental Protection Agency, Division of Control Systems.