Thermodynamics of Electrochemical Reduction of Alumina

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

“…Thermodynamically, the first one is most likely, although the reactions taking place may differ because of other oxygen-containing ions in the bath. 37,38 LOI (20-300°C) values for secondary alumina were found to be in the 0.6-2.0% range, depending on humidity. 36 In addition, some residual oxyhydroxides bound in other transition aluminas will be released at higher temperatures, which contribute to delayed formation of HF in the cell.…”

“…It is formed by reaction with fluorides in the bath or vapour phase according to reactions: 44 Water is available from the humidity in air but also the structural hydroxy groups in the primary alumina. 38,64 In addition, HF may form from the hydrogen content of the anode, where an electrolytic reaction has been proposed: 63…”

Environmental pollution due to gaseous emissions during non-ferrous extraction processes

“…According to Haupin and Kvande [16], active AlF3, which reduces melting temperature of the bath, reacts with residual moisture in the alumina charge to produce HF gas. In addition, volatile fluoride compound react with mois ture in air can form HF gas and particulate fluorides.…”

Effect of Coke Properties on the Bubble Formation at the Anodes During Aluminium Electrolysis in Laboratory Scale

“…Due to the horizontal placement of anodes in the cells, with the active part of the electrode facing downwards, such large amount of gas produced on the surface has a significant impact on the process. According to Haupin and Kvande [1], the presence of gas bubbles in an industrial cell increases the cell voltage by 0.25 V which gives about 6 % contribution to the total cell voltage. In the literature it is very common to denote this component of the cell voltage as bubbles overpotential, which is slightly confusing, because, in fact, bubbles increase cell voltage by two main mechanisms: increase of ohmic resistance of the electrolyte and increase of activation polarization [2].…”