Electrostatic Precipitation of Powdered Activated Carbon and Implications for Secondary Mercury Adsorption within Electrostatic Precipitators

Abstract

The injection of powdered sorbents, such as activated carbon, for mercury emissions control at coal-fired power plants has primarily taken place upstream of electrostatic precipitators (ESPs), which far outnumber baghouses in the U.S. Although full-scale sorbent injection tests have demonstrated varying degrees of mercury removal efficiency, the actual behavior of powdered activated carbon (PAC) within an ESP has not been well-established, particularly as this behavior relates to adsorbing gas-phase mercury. In the present experimental investigation, results obtained in a lab-scale ESP indicate that the electrical properties of PAC may cause its collection in a full-scale ESP to be significantly different from that of the native fly ash. There appears to be potential for significant collection of PAC on the discharge electrode wires of an ESP. Because these wires are typically not rapped as frequently as collection electrodes in an ESP, over time, such behavior could potentially create a series of cylindr...