THE EFFECT OF ASH COMPONENTS ON THE NO REDUCTION AND FORMATION IN THE PRESENCE AND ABSENCE OF AIR

Publisher Summary This chapter describes the effect of ash components on the NO reduction and formation in the presence and absence of air. The reason for the low concentrations of NOx in the flue gas is the internal reduction or decomposition reactions of NO with radicals such as –CHN and –NH and reactions on surfaces, above all on char, coal, and limestone. The reduction of NO is, thus, both homogeneous and heterogeneous. In a study described in the chapter, the reaction of NO over a mixture of sand and oxides showed a few percent reductions in the absence of oxygen even at a space velocity of 10000 h−1. The effect was most pronounced with Fe2O3 in the bed. With oxygen and nitrogen present, a net production was measured. The reduction of 5000 ppm NH3 over activated carbon was not much influenced by the presence of nitrogen and 1% O2, whether it is mixed with sand or other oxides. The fly ash was less reactive, with regard to the reduction of NO, than activated carbon, which may be attributed to a lower specific surface area. The presence of oxygen and nitrogen decreased the reduction at 800°C and 900°C.