EFFECT OF COAL BLENDING AND PARTICLE-SIZE ON NOX EMISSION AND BURNOUT

Investigations were undertaken with a 0.5 MW(th) test combustor burning pulverized coal, with burner or in-furnace air-staging. Significant dependences of NO(x) emission and unburnt carbon in fly ash on the flow conditions in the furnace, the blending ratio of high- and low-volatile coals and the fineness of the coal were observed. The lowest NO(x) emission, 180 ppmv, was achieved with in-furnace air-staging, at an unburnt carbon content of approximately 10 wt%, acceptable for small test facilities. The results indicate limits to the use of NO(x)-reduction techniques.