Based on the mechanism of ammonium bisulfate poisoning on catalyst

this study explains the reasons of setting minimum operating temperature(MOT) for catalyst. By analyzing the factors that influence the MOT

the variability of MOT is proposed. And according to the actual operating flue gas parameters of the selective catalytic reduction(SCR) denitrification system

the importance of MOT is scientifically evaluated. The results of low-load operation evaluation experiment of typical catalyst indicate that the catalyst performance can restore after low-load operation for a short time between the ammonium bisulfate condensation temperature and MOT. The measures to reduce the mass concentration of SO_3 by blending low-sulfur coal or other SO3 control technologies can reduce MOT for catalyst. The MOT for catalyst needs to be re-evaluated when the NOx concentration in the denitrification inlet largely deviates from the design value

or boiler is burned with high moisture content coal such as lignite coal or Indonesian coal

or the type of first layer catalyst is replaced. This conclusion provides a theoretical basis for full load operation of the denitrification system.