Effects of inherent alkali and alkaline earth metals on nitrogen transformation during steam gasification of Shengli lignite

Abstract

Abstract This work evaluated the effects of inherent alkali and alkaline earth metals on nitrogen transformation during steam gasification of Shengli lignite at the temperature of 873–1173 K in a fluidized-bed/fixed-bed quartz reactor. The results indicated that the alkali metal Na and alkaline earth metals Ca, Mg in coal have different effects on inherent nitrogen transformation to NH3, HCN and char-N during the lignite steam gasification. Specifically during the steam gasification of Shengli lignite, Na and Ca, Mg not only catalyze the inherent nitrogen conversions to NH3, but also promote the secondary reactions of the nascent char-N as well as the generation of NH3 from the generated HCN, meanwhile they also inhibited the inherent nitrogen conversion to HCN and char-N. The presence of Na, Ca and Mg hindered the formation of oxidized nitrogen (N-X) functional groups, but enhanced pyridinic nitrogen (N-6) and quaternary nitrogen’s (N-Q) formation in char.

Keywords

• Lignite
• Steam gasification
• Nitrogen transformation
• Alkali metal
• Alkaline earth metal