Kinetics and mechanism of the reaction of NO with char: Effects of coal rank, burnout, CaO, and flue gases

The kinetics and mechanism of the reduction of NO by char were investigated for chars made from five different rank coals, as well as graphite and coconut char, in a packed bed reactor at 723-1173 K. The results indicate that the NO-char reaction is first order with respect to NO and exhibits an activation energy shift from 20-40 kcal/mol at low temperatures to 45-60 kcal/mol at high temperatures for all chars studied. The char reactivity varies greatly with coal rank ;The major kinetic characteristics are independent of char burnout level and conditions, although different trends of the rate with burnout level result for different burnout conditions. These different trends can be attributed to the variation of CaO and active carbon sites during the reaction. A strong correlation of the rate with CaO surface area suggests that the reaction is catalyzed by CaO. CO and ;A mechanism of the NO-char reaction was proposed based on the kinetic and FTIR studies. Most of the experimental results can be explained by this mechanism.