Improving XRD Analysis for Complex Bath Chemistries — Investigations and Challenges Faced

An accurate bath composition analysis is essential for regulating an electrolysis cell’s mass and thermal balance. XRD is widely utilised in smelters to analyse % excess AlF₃ (xsAlF₃) and Cryolite Ratio (CR) of bath samples. However, the conventional method of analysis can provide misleading results for the more complex bath chemistries usually found in, but not limited to, Chinese smelters. This complexity is due to the presence of Li, K and Mg constituents coming into the bath from alumina impurities. They react with AlF₃ and cryolite, producing additional AlF₃-containing phases other than chiolite and Cacryolite, which are not accounted for in the conventional xsAlF₃ or CR analysis.Improvement of the xsAlF₃ analysis for complex bath chemistries was investigated and presented in this paper. The aim was to provide an XRD methodology to measure the LiF, KF and MgF₂ levels in the bath through an intensity calibration method, so that they can be integrated into the xsAlF₃ and CR analyses. The challenges faced will also be discussed in this paper.