A honeycomb SCR catalyst of V2O5/TiO2 with WO3 and MoO3 was prepared and its deNOx performance was investigated in a pilot plant test using flue gas of a coal-fired power plant.The results show that the larger catalyst volume is

the higher deNOx efficiency

and SO2 oxidation increases too

but increase ratio becomes smaller.When deNOx efficiency is above 80%

the outlet NOx concentration met the emission standards

and the efficiency improvement is not significant by further enlarging catalyst volume which led to higher construct cost.In order to obtain the best ratio of deNOx efficiency to catalyst volume and avoid resources waste for single requirement of higher deNOx efficiency

SCR catalyst volume should be adjusted for different boiler types

according to flue gas component of coal-fired power plant and national emission standards.The deNOx efficiency reduces with soot increase deposited

and drops about 9.4% within 4 h of soot depositing.The outlet NOx concentration can be at 198 mg·m-3 after 8 h of soot depositing.At 0.031 kg·m-3 of fly ash concentration

the soot deposited needed to be blown each 6 h to obtain a satisfied deNOx efficiency (>80%).When run time prolongs

the deNOx efficiency falls sharply first

and then reaches a relative stable level.Within 48—168 h

the deNOx efficiency and SO2 oxidation decline less than 1% and 0.1%

respectively.After continuous run for 3 months (2160 h)

the NOx concentration at outlet of SCR tower is 196 mg·m-3.The deNOx efficiency declines at a rate of 1% per 700 h for continuous 12 month run.