Bench- and pilot-scale evaluation of mercury speciation measurement methods

摘要

The 1990 Clean Air Act Amendments require the US Environmental Protection Agency (EPA) to assess the health risks associated with mercury. Since the rate of mercury deposition and the type of control strategies used may depend on the type of mercury species emitted, a proven sampling method that can reliably and accurately speciate mercury at the very low concentrations found in coal combustion flue gas is necessary. A number of mercury speciation methods have been proposed, including wet-chemistry methods, such as EPA Method 29, the Ontario Hydro method, and the tris-buffer method, as well as dry methods such as the Mercury Speciation Absorption method (MESA). In addition, a number of companies are developing continuous emissions monitors to speciate mercury by difference. Bench- and pilot-scale tests, sponsored by the Electric Power Research Institute (EPRI) and the US Department of Energy (DOE), are currently under way at the Energy and Environmental Research Center (EERC) to determine the most accurate and precise mercury speciation method available. The overall objective of the test program is to determine whether EPA Method 29 or other sampling methods can reliably quantify and speciate mercury in flue gas from coal-fired boilers at both the inlet and outlet of a particulate control device such as a pulse-jet baghouse. A specific goal of the project is to determine the precision and bias of the various mercury speciation methods as a function of process variables.