Abstract
Removal of sulfur, nitrogen and ash-forming minerals from coal by pretreatment is one of the promising technologies not only to lower the damage of environment but also to accelerate the development of efficient coal utilization processes. This review concerns sulfur in coal which causes air pollution and acid rain in the world. The origin and forms of sulfur in coal, analytical method of sulfur forms, distribution of sulfur in macerals, sulfur behavior during heat treatment, and advanced desulfurization technologies are discussed.
Sulfur in coal was derived from (1) sulfate in sea water that overlaid peat swamps and (2) parent plant material. Lower density group of organic matrix which is composed of exinite and vitrinite contains high sulfur. XANES analysis indicates that the low-density group contains sulfide and sulfoxide, which could contribute to the high extent of organic sulfur removal during rapid pyrolysis. Ferrous-sulfide sulfur and thiophene remains in char.
A combined process of alkali treatment with rapid pyrolysis is introduced which has aimed to transform the thermally stable form of organic sulfur to reactive species before pyrolysis. More than 90 % of organic sulfur has been removed from a subbituminous coal.
