Dentrification of coal by mild pyrolysis in a novel coal feeder

Abstract

A series of experiments have been performed with Ohio No. 8 coal in a novel coal feeder device to investigate the fate of coal nitrogen during processing. The feeder has been primarily designed to remove organic sulfur from coal prior to combustion, but tests have shown that a significant portion of the fuel nitrogen may also be removed under mild pyrolysis conditions of temperatures from 350–550°C. The degree of devolatilization and denitrification has been found to depend on the coal particles residence time in the feeder and the feeder temperature. A linear relationship was found between the percentage of devolitilization and denitrification indicating that denitrification of the volatile fraction of the coal nitrogen occurs in conjunction with the other non-nitrogen containing volatile species. The activation energies for both denitrification and devolatilization indicate the loss of volatiles and coal nitrogen are limited by heat transfer in the device, as the addition of stainless steel balls to the coal during feeding substantially increases the loss rates of both. The results indicate that it may be possible to reduce the formation of NO x from coal combustion by the use of mild pyrolysis prior to combustion of the char.