During the operation of selective catalytic reduction(SCR) flue gas denitration system of coal-fired units

NH_3 and SO_3 in the flue gas generate liquid ammonium bisulfate(ABS) at a specific temperature

which is viscous and easy to cause catalyst deactivation at 0～40% low load due to micropore plugging and aggravate the fly ash blockage of heat exchange elements at the cold end of air preheater. Alkali powder injection to remove SO_3 from flue gas is an important method to control ABS. However

the existing grid type multi-nozzle device has problems of uneven injection and low SO_3 removal efficiency. A vertical gas-solid fluidization mixing and distribution injection device is developed to improve the uniformity of absorbent powder injection in the flue section. The pilot test results show that

the SO_3 removal efficiency at upstream of the SCR denitration system reaches 55.6%

the condensation temperature of the catalyst ABS decreases by 8.6 ℃

and the minimum operation temperature decreases by 11.9 ℃

which can expand the lower limit of the catalyst operation temperature and reduce the restriction on the lower limit of the peak load of the unit. The SO_3 removal efficiency at upstream of the air preheater reaches 84.3%

and the ABS deposition influence coefficient decreases by 86.9%

which can delay the ABS ash blockage at the cold end of the air preheater. The SO_3 emission mass concentration from the chimney is 2.5～ 3.4 mg/m~3

which can eliminate blue smoke.