SO{sub 3}'s impacts on plant O & M: part 1

The visible consequences of sulfuric acid aerosol emissions, opaque stack emissions called 'blue plumes', are merely the tip of an iceberg. In sufficient concentration, SO{sub 3} also can increase corrosion and fouling of equipment and components downstream of the furnace while decreasing their efficiency and penalizing overall plant heat rate. This article, the first in a three part series, details the negative impacts of SO{sub 3} on operations and maintenance of back-end plant equipment. These include: reduction of unit heat rate and increased corrosion of downstream equipment due to the raising of dew point by SO{sub 3}; fouling of air heaters and SCR catalysts due to the reaction of SO{sub 3} with ammonia and competition of SO{sub 3} with mercury for adsorption sites on carbon particles, reducing the effectiveness of mercury emissions control. Part II will explain and quantify the potential benefits of limiting the concentration of SO{sub 3} in flue gas to 3ppm at the entrance to the air heater. Part III will describe the characteristics of an optimal SO{sub 3} removal technology and present the technical details and operating experience of one patented process that has worked successfully at a half dozen plants for up to three years. 1 ref., 2 figs.