Advance of research on the occurrence state and content of nitrogen in coal

This paper summarizes the current status of research on occurrence state and content of nitrogen in coal. Organic nitrogen is considered as the major mode in coal and exists in the forms of pyridine (N-6), pyrrolic(N-5), quaternary nitrogen (N-Q) and nitrogen oxides (N-X). Relative amount of these four nitrogen -bearing functional groups change with coal rank and the pyrolysis of coal. Studies have shown that nitrogen content in coal varies from 0.5% to 2.5%, and is mainly influenced by several geological factors including coal rank, coal-forming age, depositional environment, coal-forming plants, macerals and magmatic intrusion. At present, study of nitrogen content in coal focuses on the relationship between the nitrogen content and coal rank, and considers that the nitrogen content increases with coal rank, but decreases rapidly in the late stage of coalification. Relative studies of nitrogen in coal can enrich the geochemistry research of elements in coal and provide more scientific basis for controlling environmental pollution of coal.