Monitoring of Continuous PFC Formation in Small to Moderate Size Aluminium Electrolysis Cells

Aluminium Primary Production Off-Gas Composition and Emissions: An Overview

“…42 The trade-off for sensitivity is often a loss in dynamics due to the increased volume of the measurement cell. 43 For in-line configurations, the across-duct installation diameter would normally dictate the quantification limit. References to multi-pass configurations for in-line monitoring have not been found.…”

“…Evidence of CF 4 formation at low voltages may support an intermediate formation of COF 2 followed by decomposition into CF 4 . 43,71 In industrial-scale electrolysis, COF 2 is believed to decompose into HF and CO 2 and is thus not present in the duct. In a beam-through cell experiment with open-path spectroscopy, only traces of COF 2 have been identified.…”

Simulator of Non-homogenous Alumina and Current Distribution in an Aluminum Electrolysis Cell to Predict Low-Voltage Anode Effects

“…On the other hand, Reaction [2] is plausibly the main reaction leading to PFC generation during LVAE as the increase in anodic overvoltage is not occurring globally in the cell but rather locally under only a small number of anodes where the local conditions changed due to a low alumina concentration. However, COF 2 is thermodynamically unstable under the electrolysis bath conditions and will rapidly decompose to form CF 4 or C 2 F 6 following Reactions [5] and [6], where K is the kinetic of the reactions.…”

“…In agreement with the theoretical assumptions, a low alumina concentration was found to be one of the most important elements that can lead to LVAE. [8,9,11,[13][14][15][16][17] However, most of these studies also demonstrated that the current density and the anodic overvoltage were strongly related to LVAE as well [8,9,11,13,15,16] due to the interdependence of all these elements. Coherently with these results, the onset of LVAE often appears a short while after an anode change [8,9,12,16,17] which indicates that the perturbation of the current distribution plays an important role in this phenomenon.…”

“…Since the cell voltage is a well-followed indicator, such events can be easily detected by the cell control system and are classified as high-voltage anode effect (HVAE). However, recent studies (early 2010s) [5][6][7][8][9][10] demonstrated that PFC emissions can also be generated locally by similar mechanisms under only a few number of anodes. Redistribution of the current might prevent propagation of this phenomenon and only a local increase in resistance is observed with no significant increase in the global cell voltage.…”