OCR Text |
Show (4) Step r espons of NUx for inpul of the coo ling air or bypass- flue damper I ) Coo ling air Fig. 1-20 shows the step response of NOx for input of the cooling air volume. 02 and NOx are in a remarkably positive relationship. The stepped increase and decrease in the cooling air, in other wards, increase and decrease of 02 are clearly shown in fluctuation of NOx. ii) Bypass-f lue damper Fig. 1-21 shows the step res ponse of NOx for the opening of the bypass-flue damper. The difference due to opening and closing of the bypass-flue damper is the difference between whether or not the reduction gas generated in the drying zone passes under a high O2 concentration through the main combustion zone with flames and the after burning zone. (Refer to Fig. 1-22) When the bypass-flue damper is in the full open pos ition, as the r eduction gAS passes through the bypass-flue where the temperature is not high under a low 02 concentration, the increase in NOx controls due to Ileal decomposition of the reduction gas or oxidation of NII3 and HCN. Al so, it becomes poss ibl e to Jet it self-denitrify effertiv01y in the gas mixing chamber away from the main combustion zone. Therefore, the step changes of the bypass-flue damper remarkably appears in the step response of NOx. 6 |