Research Progress on Ammonium Bisulfate Formation and Control in the Process of Selective Catalytic Reduction

The formation mechanism of ammonium bisulfate (ABS) in the process of SCR flue gas denitrification and some research progresses on ABS are reviewed in the paper. The main factors affecting the formation of ABS are investigated, the formation temperature of ABS is in the range of about 190 degrees C-240 degrees C; ABS exists in vapor phase at temperature between 320 degrees C and 345 degrees C, and begins to decompose when the temperature is higher than 345 degrees C; the formation of the ABS can be reduced by reducing the amount of NH3 slip and SO3, in the flue gas. The adverse effects of ABS on catalyst and air preheater are discussed: ABS will cover the surface of catalyst and Bronsted acid sites, decreasing denitrification efficiency; it will deposit in the air preheater, fouling and corroding the air preheater and reduce its operational effectiveness; it also can reduce the resistivity of fly ash and the quality of the fly ash as well. The methods to control ABS formation and the measures to reduce its negative effects are proposed: Select appropriate operating temperature to reduce the ABS deposition over the SCR catalyst; replace the material of the air preheater components from steel to ceramic coating type and change the structure of the air preheater; Take proper methods to reduce NH3 slip and the oxidation rate of SO2, etc. (C) 2016 American Institute of Chemical Engineers Environ Prog, 35: 1664-1672, 2016