The Clean Air Act Amendments Essay -- Environmental Protection Agency

The Clean Air Act Amendments of 1990 (CAAA) address 189 hazardous air pollutants (HAPs) believed to be detrimental to human health and the environment and found that mercury and its compounds are one of the highest priority pollutants to investigate. The CAAA required the U.S. Environmental Protection Agency (EPA) to conduct a mercury emissions study, including those from electric utility steam generating units. In 1997, EPA released the Mercury Study Report to Congress which analyzed mercury emissions from power plants and investigated control technologies. In 1998, EPA released the Utility Air Toxics Study which also showed mercury as a top priority pollutant due to its multi-pathway exposure potential and its ability to bio-accumulate and persist in the environment as methyl mercury. [1, 2] Mercury control in combustion flue gas is highly dependent on speciation. Oxidized mercury is removed relatively easily by particulate control equipment as well as wet scrubbers used to control sulfur dioxide. However, elemental mercury is highly volatile and has very low water solubility allowing it to escape through most pollution control equipment. The objective of this project is to understand the importance of and the contribution of gas-phase coal constituents in the mercury oxidation reactions. The project involves experimental efforts. The objective is to determine the experimental parameters of importance in the homogeneous oxidation reactions; effect of each of these parameters on the mercury oxidation for various concentration and temperatures. The objective of this project was to test the performance of Bromine and Chlorine (Cl2) on homogeneous mercury oxidation in the presence of common flue gas components such as Nitric Oxide ... ...constituents or it self before it could oxidize mercury at the required temperature. A fundamental understanding of the mercury flue gas chemistry is needed to develop effective control technologies for mercury. Since the reactions of atomic and molecular chlorine with other flue gas constituents determine the concentration of reactive chlorine species remaining in the cooled gas, the effects of specific gas constituents on the chlorine-mercury have been extensively investigated. Experimental data indicate a negative effect of SO2 and NO mercury chlorination in the presence of H2O [13]. Recent experimental data by the EERC indicate that bromine species have a high potential in mercury control applications [12]. In the proposed study the emphasis is on the homogeneous reactions of mercury in flue gas with Br2 and Cl2 in the presence of other flue gas constituents.