PM_(2.5) Emissions from Aluminum Smelters: Coefficients and Environmental Impact

摘要

From 2004 to 2009, aiming to better understand implications for its smelters, Rio Tinto Alcan conducted a detailed study of PM_(2.5) and PM_(10) (paniculate matter [PM] ≤ 2.5 and 10 μm in aerodynamic diameter, respectively) in its facilities. This involved a two-level study: part 1, emission quantification; and part 2, assessment of aluminum smelter contribution to the surrounding environment. In the first part, U.S. Environmental Protection Agency Other Test Method (OTM) OTM27 and OTM28 are assessed as relevant and efficient methods for measuring fine particle emissions from aluminum smelter stacks. Rio Tinto Alcan has also developed a safe and robust method called CYCLEX to measure PM_(2.5) and condensable partic-ulate matter (CPM) at the roof vents of potrooms. This work aims to determine the PM_(2.5) emission coefficients of 17, 55, and 417 g·t~(-1) of aluminum produced (including CPM) in anode baking furnace exhaust (fume treatment center), at potroom scrubber stacks (gas treatment centers), and at potroom roof vents, respectively. Results indicate that roof vents are the primary PM_(2.5) emitters (85% of all smelter emissions) and that 71% of all smelter PM_(2.5) comes from CPM. In the second part, preliminary inorganic speciation studies are conducted by scanning electron microscopy-energy-dispersive X-ray analysis and by isotopic ratios to track smelter emissions to their surrounding environment. This paper releases the first speciation results for an aluminum smelter, and the preliminary isotopic ratio study indicates a 3% impact in terms of PM_(2.5) emissions for a representative smelter in an urban area.