Analysis of ammonium bisulfate/sulfate generation and deposition characteristics as the by-product of SCR in coal-fired flue gas

Abstract

The generation and deposition of ammonium bisulfate (ABS) in flue gas caused serious blockage and corrosion to the air preheater, which seriously affect the safe and economic operation of coal-fired power plants. The generation and deposition of ABS/ammonium sulfate (AS) under non-catalytic conditions were studied on a simulated air preheater test bench, and FT-IR and XRD tests were performed to characterize the products under different conditions. Experimental results show that the generation of ABS/AS is complicated and controlled by the concentration of SO3 and NH3, the ratio of SO3 to NH3 (SO3/NH3) and deposition temperature. Under the same SO3 conditions, ABS/AS generation rate under different SO3/NH3 conditions is 1:2 > 2:1 > 1:1. The initial deposition temperature of ABS/AS will increase with the corresponding increase of SO3 and NH3 concentration, and is exponentially correlated with the product of SO3 and NH3 concentration in flue gas. In the temperature range 390–223 °C, ABS generated and deposited under all conditions, and in the temperature range 223–131 °C, the mixture of H2O, H2SO4, and ABS generated and deposited when SO3/NH3 is 2:1, and AS with a small amount of (NH4)3H(SO4)2 generated and deposited when SO3/NH3 is 1:1 and 1:2.