OCR Text |
Show 3.2 Results and Considerations Figure 6 shows the variations of the NOx concentration. the conte'nt of unburnt carbon in fly ash (UB) and the coal burnout (BR) with the excess O2 (ex.02) in the outlet of the furnace, where the parameter is the coal particle size. The results we obtained were as fo llow. UB decreased and BR increased with decreasing particle size. That is, a smaller particle size gave a higher combustion efficiency. The variation of NOx reduction with particle size was greatly affected by the excess O2 ~oncentration. That is, the NOx concentration decreased with decreasing particle . size at low excess O2 concentrations (ex. O2 <3%). but it decreased with increasing particle size at high excess o 2 con c eOn t rat ion s (ex. O2 >3%)". Then, we measured the NOx. O2 and temperature profiles in the furnace for the conditions of 2% excess O2 (low excess O2 ) and 5% excess O2 IN ii to -- 200 oz> ( . fg Fig. 6 (high excess O2 ), \ . 99.5 99.0 ~~ 98.5 98.0 6.0 Effect of Particle Size on NOx and Unburnt Carbon Figures 1 and 8 show the distributions along the axis of the furnace under low excess 0, (2%) and high excess O2 (5%), respectively. The results we obtained as follows. When using fine particles (more than 95 wt% passing through 200 mesh) at both low a.nd high excess 0, conditions. rema.rkable changes were -5- |