During the low load operation of coal-fired units

the SCR denitration catalyst may be deactivated by ammonium bisulfate(ABS). The experimental tests are carried out on this phenomenon and the results show that:1) with the flue gas temperature below the ABS condensation temperature

the catalyst will be deactivated due to the gradual deposition of ABS in the micropores. The ABS condensation temperature is inversely proportional to the micropore diameter

and the ABS concentration is positively related to the product of NH3 and SO3concentrations in the flue gas; 2) the micropores with pore diameters of 2～20 nm are still the main structure of wide temperature denitration catalyst as well as the conventional catalysts

which cannot change its fate of ABS deactivation under low load; 3) the physical reversibility of catalyst ABS deactivation makes “combination of prevention and treatment” still the fundamental method to solve the ABS problem.