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 ℃

摘要

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 ℃. 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 NH3 and MCN from char-N. The presence of volatile-char interactions during the gasification of Victorian brown coal in O_2 at 800 ℃ drastically enhanced the formation of NH_3 and, albeit to a lesser extent, the formation of HCN. The enhanced conversion of char-N into NH3 (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.