Control of sulphur trioxide (SO{sub}3) emissions from coal fired power plants has recently been the subject of attention from utility management, the public living near the plants, and environmental regulators. What once was an aggravating problem of sulphuric acid corrosion of ducts and electrostatic precipitators (ESP) has become a problem of visible plumes, plume touchdowns, increased operating costs, and increased scrutiny from regulators and the public. Ironically the main cause of the recent attention has been the advent of selective catalytic reduction (SCR) for control of nitrogen oxides (NO{sub}X). These SCR units actually reduce the amount of air pollution coming from the plants. However, they also increase SO{sub}3 concentrations in flue gas enough to make significant changes in the sulphuric acid dew point and in the visible plume.
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