Low and High Voltage PFC Slope Coefficient Monitoring During Pot Start-Up

The latest intergovernmental panel on climate change update includes a methodology to estimate perfluorocarbon (PFC) emissions generated during reduction cell start-up. Alcoa has sampled PFC emissions to estimate tier 3 PFC emission slope from aluminum cell operation including cell start-up, for low and high voltage PFC emissions. Results obtained show that cell start-up methodology will impact the PFC emission slope. Thus, some aluminum smelters will have similar PFC emission slope coefficients for cell start-up and older cell in operation, while others will have different PFC emission slope coefficients for start-up and older cell. Based on this, Alcoa smelters in Canada have put in place a procedure to analyze and use different slopes or integrate both results into one slope depending on the number of pots started during a given period.