The investigation of NOx formation and reduction during O2/CO2 combustion of raw coal and coal char

This study investigated the behavior of NO emissions during combustion of pulverized coal char and pulverized raw coal in O2/CO2 environments under nearly isothermal condition in a drop tube furnace. A representative Chinese coal Ling Nancang (LNC) and LNC CO2-char (made in CO2 condition) were studied with four different excess oxygen ratios (a=0.6, 0.8, 1.2, and 1.4). Combustion experiments were performed with an elevated concentration (850 ppm) of NO. When a increased from 0.6 to 1.4, the total amount of NOx reduction was increased in both pulverized coal and char combustion. To investigate the effects of coal and char on NO reburn reactions, LNC coal char and the raw coal combustion experiments were also performed under three high background NO concentrations (400, 850, and 1200 ppm) in O-2/CO2 atmosphere. During experiments with elevated NO concentrations, there was an increase in net NO reduction; however, there was also a decrease in the calculated NO reduction ratio.