Removal of Sulfur from Coal Using Mild Oxidizing Conditions

Abstract

Methods for the determination of organic sulfur in coal and for the identification of organic sulfur compounds in coal and coal extracts are reviewed. Most studies have focused on the thiophenic sulfur groups in coal which are the most stable and the most difficult to remove. The goal of this research was to optimize mild oxidizing conditions capable of removing inorganic and aliphatic sulfur constituents from coal, but not thiophenic sulfur groups. Consequently, mild oxidizing conditions were used to quantify the amounts of aliphatic sulfur compounds in Illinois Basin coals and the distribution of these compounds in different ranks of coals. The results of this research indicated the optimum mild oxidizing conditions are aqueous slurries of 5% coal ( 60 mesh) in 1 M NH4OH reacted at 7 - 10 atm of O2 and 150 - 200°C for 1.5 hrs. Under these conditions 22 - 44% of the organic sulfur, 81 - 95% of the inorganic sulfur, and 51 - 75% of the total sulfur are removed from Illinois Basin Coals. In addition, it appears that aliphatic sulfur is higher in high sulfur coals than in low sulfur coals, and is very low in high rank anthracite coal. Aliphatic sulfur in the Illinois Basin bituminous coals studied ranged from 22% to 44%