Abstract
The existence of continuous or non-anode effect formed perfluorocarbons (PFC) has been documented for larger size aluminium electrolysis cells. It has been proposed that less uniformity in dissolved alumina for larger cells may elevate individual anode overvoltage sufficiently to produce PFC. Continuous PFC was monitored after the dry scrubber on a train of 28 cells at a Norwegian smelter. For this work a fourier-transform infrared spectrometer was used. Equipped with a mercury cadmium telluride detector and retrofitted with a 35 m / 11 L measurement cell it was possible to get the detection limit down in the low ppb range needed for this study.
It was discovered that also small cells could emit PFC that was not directly related to the full anode effect. Continuous formation of PFC was found to be in the form of CF4, for the most part; however, the results indicate that C2F6 may also form outside the full anode effect. No numerical data for the contribution of non-anode effect emissions to the overall PFC was calculated, nonetheless, judging by the difference in intensity it will be small for this particular smelter.
It was discovered that also small cells could emit PFC that was not directly related to the full anode effect. Continuous formation of PFC was found to be in the form of CF4, for the most part; however, the results indicate that C2F6 may also form outside the full anode effect. No numerical data for the contribution of non-anode effect emissions to the overall PFC was calculated, nonetheless, judging by the difference in intensity it will be small for this particular smelter.