Evaluation of Gas Composition from Laboratory Scale Electrolysis Experiments with Anodes of Different Sulphur Content

Abstract

With the anticipated decrease in available anode raw materials, future anodes are expected to contain higher levels of impurities. Currently the implications of this are being investigated through evaluation of electrochemical performance of anodes and the environmental aspects through gas evolution studies. In this work, four experiments of aluminum smelting have been conducted with anodes of varying sulphur content. The aim of this work was to evaluate the speciation of sulphur in the off-gas. It was found that COS is the main sulphur species in the inert argon furnace atmosphere. The gas composition was further evaluated as a function of set anode voltages in potentiostatic mode. The significance levels of gas composition were evaluated through repeated experiments. As an FTIR multicomponent analyzer was used, less commonly discussed gaseous constituents such as CH4 and HCl were evaluated with respect to given impurity levels in the anode.

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

“…Most of the published data on carbon oxide gas production are, however, reported from either laboratory-scale experiments or experiments where the anode gas is extracted from the cell attempting to avoid the aforementioned reactions of the carbon dioxide gas after being produced. [47][48][49] Primary aluminium production off-gas composition, including both the CO and CO 2 ratios, is, however, scarcely reported. Kimmerle 48 reported numbers for CO 2 and CO to be 14,500 and 1340 ppm, respectively.…”

“…Experimental data clearly show that COS is the dominating sulfurous gas species when oxidation is avoided. 48,49,52,54,55 Although the gas species H 2 S and CS 2 are frequently reported in small amounts in the anode gas, it is only occasionally reported for duct gas measurements. Most likely the observed CS 2 (and H 2 S) is a result of decomposition of COS at intermediate temperatures (350-600°C).…”