# Characterization of Off-Gases from an Inert Electrode Aluminum Electrolysis Cell

## TL;DR

This study analyzed the gases released from a new aluminum electrolysis cell and found oxygen to be the main gas, with other gases likely coming from the environment.

## Contribution

The study provides a detailed gas characterization of an inert electrode aluminum electrolysis cell compared to traditional methods.

## Key findings

- Oxygen was identified as the main gas released during the inert electrode electrolysis process.
- Hydrogen fluoride and gases like nitrogen and CO2 were detected, likely from environmental sources.
- A small amount of SiF4 was also detected in the off-gases.

## Abstract

Characterization of the off-gases from a 500 A inert electrode aluminum electrolysis cell operating at a temperature of ca. 800 °C has been conducted using characterization units comprising gas chromatography, tuneable diode laser spectroscopy, and Fourier-transform infrared spectroscopy. The off-gases detected from the inert electrode aluminum electrolysis cell have been compared to the off-gases released from the traditional Hall–Héroult aluminum electrolysis cell. All the measurements from the inert electrode cell confirmed oxygen as the main process gas during the electrolysis process. Hydrogen fluoride, HF, which is assumed to result from reactions between moisture in the alumina raw material or the surrounding air and the fluoride melt, was also observed together with gases assumed to come from air introduced, such as nitrogen and CO2. There were no indications that these gases came from the production process. A very small amount of SiF4 was also detected.