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Quantification of perfluorocarbons emissions during high voltage anode effects using non-linear approach

Dion, Lukas, Marks, Jerry, Kiss, László I., Poncsák, Sándor, Lagacé, Charles-Luc
Journal of cleaner production 2017 v.164 pp. 357-366
aluminum, anodes, carbon dioxide, carbon tetrafluoride, data collection, emissions, greenhouse gases, inventories, nonlinear models, prediction, spectrometers
Significant amounts of greenhouses gases are produced annually by aluminium smelters around the globe. Most of these emissions are carbon dioxide but perfluorocarbons are nonetheless an essential part of GHG inventories for aluminium smelters. The total mass of perfluorocarbons declared is estimated using a linear relationship between some process parameters and a specific emission coefficient. However, this linear method does not accurately represent the observed behaviour of PFC emissions.Continuous gas measurements were performed using a Fourier-transformed infrared spectrometer connected to the gas treatment centre for several days. With the data collected from individual high voltage anode effects, four new models are proposed to estimate the emissions of tetrafluoromethane, along with three new models to estimate hexafluoroethane emissions.These non-linear models are compared to the existing methods and the overall accuracy of each model is calculated in comparison to in-situ measurements. The accuracy of each model to predict emissions associated to individual anode effects have been investigated as well and the results indicate that tetrafluoromethane emissions can be more accurately predicted by the proposed non-linear models. Models proposed to predict hexafluoroethane emissions are optimistic, but further refinements are necessary to optimise the accuracy of individual predictions.