Formation of NO x precursors during the pyrolysis of coal and biomass. Part X: Effects of volatile–char interactions on the conversion of coal-N during the gasification of a Victorian brown coal in O 2 and steam at 800 °C

Abstract

A novel fluidised-bed/fixed-bed reactor was used to study the effects of volatile–char interactions on the conversion of coal-N during the gasification of a Victorian brown coal at 800 °C. The reactor has the capability of controlling the extent and length of the interactions between volatiles and char. Our results indicate that in the absence of volatile–char interactions during gasification in O 2, the lack of abundant H radicals led to negligible formation of NH 3 and HCN from char-N. The presence of volatile–char interactions during the gasification of Victorian brown coal in O 2 at 800 °C drastically enhanced the formation of NH 3 and, albeit to a lesser extent, the formation of HCN. The enhanced conversion of char-N into NH 3 (and HCN) due to the volatile–char interactions is attributed to the presence of H radicals in the volatiles. H radicals in volatiles could “die off” as they pass through the nascent char bed during the course of volatile–char interactions.