The reactivity of chars from coal, peat and wood towards NO, with and without CO

The reduction of NO by chemical reaction with chars prepared from bituminous coal, peat and wood was studied, with and without CO present in the gas. Chars were prepared in pure nitrogen at the same temperatures as for the NO reduction: 750, 850 and 950°C. Tests were conducted in a quartz fixed bed reactor with gas analysis for NO, CO and the product gas CO₂. The bulk gas was nitrogen; since no oxygen was present N₂O was not considered. Eleven different solid fuel qualities were studied. Chars from peat and lignite appeared more reactive with respect to NO than chars from bituminous coal or wood. This trend was different from char gasification reactivities of these fuels, which increased with increasing fuel volatility. Activation energies were in the range 28-131 kJ mol^-1 for the NO reduction with CO, catalysed by the char, against 29-95 kJ mol^-1 for the NO reduction by char. For peat, the reduction of NO was found to be faster without CO than with CO present in the gas. Correlations between NO reduction capacity and char composition were made, which showed the catalytic effect of calcium, magnesium and potassium. The role of iron appeared unclear.