Trinity Consultants


On December 15, 2003, the United States Environmental Protection Agency (U.S. EPA) proposed a rule with two alternatives to permanently reduce mercury (Hg) emissions from power plants. Under one alternative, which is the focus of this paper, the utilities would install controls known as Maximum Achievable Control Technologies (MACT) under section 112 of the Clean Air Act (CAA). The proposed rule is to be finalized in March 2005. If implemented, several considerations must be taken into account before preparing successful strategies for meeting the proposed MACT standard. These considerations include, but are not limited to, the accuracy of Hg measurement, the lack of commercially available continuous emission monitoring systems for Hg emissions, and the options available for control technologies. This paper presents a case study of a coal-fired power plant owned and operated by the Lower Colorado River Authority (LCRA) in La Grange, Texas, which would be subject to the proposed Hg MACT standard and is currently evaluating the feasibility of compliance with the standard. As a part of ongoing continuous compliance determination measures, coal samples are analyzed for Hg content, chloride content, sulfur content, ash content, and calorific value. Additionally, the utility has historical records of flue gas Hg measurements, which were submitted during the U.S. EPA’s Information Collection Request (ICR) in 1999. The available Hg input and output emissions information is reviewed to assist in making decisions on controlling Hg emissions from the plant. However, the variability of coal Hg content poses unique challenges in developing strategies for compliance with the proposed MACT standard. In this paper, coal composition, Hg content, plant design and operation, available control options, and the effectiveness of several types of Hg emission control methods including precombustion controls, flue gas cleaning technologies, wet scrubbers, particulate controls, etc., are reviewed to identify possible strategies for Hg MACT compliance.

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