(639b) Mercury Control Strategies in Coal-Fired Power Plants

Mercury control in coal-fired power plants can be accomplished using two main strategies, co-benefits approach or mercury-specific approaches, and this talk will present an overview of these stratgies and how various technologies fit into the strategies.  We will review specific pilot- and full-scale experimental results.  Finally, we will focus on the development of future technologies in mercury control.

Co-benefits approaches generally focus on the oxidation of mercury and the dissolution of the oxidized mercury into existing wet flue gas desulfurization (WFGD) equipment.  This oxidation can be accomplished by the native halides in the fuel, by the addition of halides or other oxidizing agents to combustion process, or by the co-benefit of oxidation across existing catalyst, which would be used for NOx reduction.  Once oxidized, the mercury salts can be dissolved into the WFGD.  However, depending upon the WFGD unit chemistry, reduction of mercury salts back to the elemental form may occur, necessitating the use of a mercury-specific approach (such as sorbent or chelating agent in the WFGD). Mercury-specific approaches generally focus on the use of sorbents for the removal of mercury, and the mercury-laden sorbents are then removed in existing electrostatic precipitator (ESP) or fabric filter (FF) baghouse.  Typically the sorbents have an activated carbon base material, though non-carbon oxides, metals, and other materials have been tested over the years.  There are some challenges related to these sorbents, particularly in flue gases derived from high S fuels (high SO3) where their sorption capacity is decreased.  This talk will focus also on some strategies that have been used to increase capacity in high SO3 environments.  Other issues include sorbent in fly ash, as well as the generally low dynamic sorption of these materials in the flue gas environment. 

Several research programs, including development/testing of SO3 tolerant and non-carbon sorbents as well as control of mercury re-emission from the WFGD, have been recently performed at Southern Company. This talk will highlight those results which have been achieved at the pilot- and full-scale. 

Finally, with the US EPA enforcement of Mercury and Air Toxics Standards Rule imminent, this talk will discuss the future of mercury control technology development.