Combined control of aluminum bath composition by X-ray diffraction and X-ray fluorescence analysis

Abstract

The present paper provides a combined application of X-ray diffraction (XRD) and X-ray fluorescence (XRF) methods in process control for the analysis of aluminum baths of different compositions. Developed approaches to the combined calibration XRD and XRF methods, independent calibration XRF techniques and to the full-profile automated Rietveld analysis of a bath composition are described. We established that combined XRD–XRF calibration techniques provide an accurate stable analysis of technological parameters in a wide range of traditional and low-melting compositions due to an accurate quantification of CaF2, MgF2 and KF additives. The developed XRF techniques provide quantitative analysis of both cryolite ratio and alumina with the accuracy of 0.03 and 0.25% wt. respectively, which is comparable with the technologically required accuracy. The evolutionary approach that automates full profile quantitative XRD analysis of bath composition and uses XRF data on Ca and Mg provides a better accuracy of measuring cryolite ratio compared to an accuracy of non-automated analysis by Rietveld method. Combined application of the two X-ray methods eliminates gross analytical errors and stabilizes overall performance of a smelter's process control system. Copyright © 2017 John Wiley & Sons, Ltd.