Tampa Electric Company (TEC) Big Bend Station is located in Apollo Beach, Florida and consists of four (4) coal-fired boilers with a total generating capacity of 1,840 MW. A limestone based forced oxidation flue gas desulfurization (FGD) system began operation in March 1985 to
control sulfur dioxide emissions from Unit 4. Flue gas from Unit 3 was added to the existing FGD system for sulfur dioxide removal in 1996.
To meet 1990 Clean Air Act Amendments Phase II requirements, TEC is required to reduce sulfur dioxide emissions from Units 1 & 2. To achieve compliance and broaden the range of fuel types and sources, TEC has elected to retrofit a new flue gas desulfurization system for the combined flue gas generated by Units 1 & 2. The FGD system will consist of a single absorber module designed to operate at a high velocity and achieve 95% sulfur dioxide removal. The absorber will utilize a Dual Flow Tray and dibasic acid (DBA) to enhance flue gas absorption capacity, while producing commercial grade gypsum. The new FGD system includes booster fans, ductwork to interface with the existing electrostatic
precipitators, and a new chimney. The existing reagent preparation system was expanded to provide reagent slurry for the new system (Units 1 & 2). The dewatering equipment, consisting of primary dewatering hydroclones and rotary drum vacuum filters, was also upgraded to serve
both station FGD systems. A new wastewater treatment system, sized to handle the combined blowdown from both FGD systems, is also
supplied. The single absorber vessel for scrubbing the gases of Units 1&2 necessitated the selection of corrosion resistant materials that would allow for high on-line availability of the FGD system. The chloride concentration level of up to 30,000 ppm in the recycle tank during normal
operation, eliminated many of the medium grade stainless steels from consideration for the scrubber/outlet duct. This paper will review the overall system and absorber designs. The materials of construction that were selected along with those that were considered will be
discussed. Construction methods with specific attention to welding considerations will also be reviewed.