Abstract
The applicability of near-infrared (NIR) spectroscopy as tool for continuous and direct quality control of bauxite material on conveyor belts at mining sites was assessed. Modal quantifications of the bauxite mineralogy were performed by X-ray powder diffractions (XRPD)/Rietveld-analysis on 200 aliquots derived from 4 charges from the same sample locality and compared to Near Infrared (NIR) spectra measured in reflectance mode. Based on the two methods multivariate calibration models from partial least squares (PLS) regressions were evolved. Laboratory scaled results show a predictability of the major mineralogical phases (gibbsite and kaolinite) within 2.5wt% (1σ).In order to test the quality of the laboratory scaled calibrations and their applicability to mining procedures, additional measurements were performed using an industrial NIR-analyzer from ABB that was specifically developed for conveyor belts. Results show that for an industrial usage two crucial points have to be considered: (1) The modal mineralogy of individual chunks of material depends on the grain size. Specifically, larger chunks contain a higher modal content of gibbsite and often are coated by a kaolinite-rich shell. Therefore, modal mineralogy determined by NIR spectroscopy in reflectance mode is biased by the grain size. In order to yield unbiased measurements, the material must be crushed at least to cm-size. (2) Humidity has strong influence on the NIR-spectra by changing band intensities. Therefore, in order to get accurate predictions, absorption bands of water have to be taken into account as additional constituent in the calibration models.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.