Effects of volatile–char interaction on the formation of HCN and NH 3 during the gasification of Victorian brown coal in O 2 at 500 °C

Abstract

In a coal gasifier interactions between volatiles and char are significant. The partly reducing conditions in a gasifier would mean the presence of high concentration of partial oxidation products and radicals surrounding the char particles. Currently, little is known about the effects of in situ volatile–char interactions on the conversion of char-N. This study examines the effect of in situ volatile–char interactions on the formation of HCN and NH 3 during the low temperature (500 °C) gasification of Loy Yang brown coal in oxygen. Two novel reactor systems were used. The reactor configurations allowed the quantification of HCN and NH 3 from char-N gasification, volatile-N oxidation and volatile–char interactions separately. Our results indicate that volatile–char interactions can have drastic effects on coal-N conversion during gasification by providing an important source of the radicals for the formation of HCN and NH 3 from char-N during gasification in 4% or 8% O 2 at 500 °C. In the presence of radicals and O 2, N-containing structures in the nascent char can be easily broken down to give HCN and NH 3 during the gasification of the char. In the absence of O 2, some of the nascent char-N structures may stabilise into structures less favourable for the formation of HCN and NH 3 and more favourable for the formation of other N-containing species such as NO x .