Characterization of ammonium bisulfate formation in a bench-scale single-channel air preheater.

摘要

Ammonium bisulfate (ABS) is a compound that forms in coal-fired power plant exhaust systems when ammonia slip from the NOx control system reacts at the appropriate temperature with the sulfur oxides and water in the flue gas. The critical temperature range for ABS formation occurs in the air preheater, where ABS is known to cause corrosion and pluggage that can require unplanned outages and expensive cleaning. To mitigate the deleterious effects of ABS in air preheaters, it is important to know its formation temperature and location. This thesis describes a bench-scale single-channel air preheater experiment, with the appropriate temperature gradient, used in conjunction with simulated coal combustion flue gas, including sulfur oxides, ammonia, and water vapor, to investigate the formation of ABS. Formation was observed optically, and the formation temperatures for a wide range of reactant concentrations are presented and compared with previous studies on ABS formation. It was found that the measured ABS formation temperature under air preheater channel conditions lies between the temperatures reported by others. The results also show that, at least for this experimental configuration, ABS forms as an aerosol in the gas phase rather than as a condensate on the channel walls.