Development of advanced retrofit FGD designs

The 1990 Clean Air Act Amendment is a dramatic departure from previous legislation in that it affords the electric utility industry the flexibility to achieve their portion of the sulfur dioxide reduction in a myriad of ways. Each utility must look at its system overall. One strategy which may prove beneficial is to remove as much SO2 as possible at facilities where there is an existing flue gas desulfurization (FGD) system or where one is planned. In response to this need EPRI is developing a family of advanced retrofit FGD designs that incorporate recent advances in FGD technology. A range of design options are being investigated to determine both the SO2 collection capability and the relative cost impacts of each option. Some of the design options considered include the use of trays, packing, additional liquid flow rate, and additives to boost the removal efficiency. These options are being investigated for limestone, and magnesium-enhanced lime systems. The sensitivity of these designs to changes in coal sulfur content, chloride content, unit size, gas velocity, and other factors are being investigated to determine how the performance of a designs is changed and the ability to meet compliance. This paper illustrates the type of analysis used to develop the advanced designs and presents the sensitivity of a Countercurrent spray tower design using limestone and forced oxidation to changes in specific design input parameters such as boiler load, tower height, and gas velocity