Abstract
Quantitative analysis of CaO in limestone mining is mandatory, not only for ore exploration, but also for grade control. A partial least squares regression (PLSR) CaO estimation technique was developed for limestone mining. The proposed near-infrared spectroscopy (NIR)-based method uses reflectance spectra of the rock sample surface in the visible to short-wave infrared wavelength regions (350–2500 nm (4000–28,571 cm−1)) without the need to crush and pulverize the rock samples. The root mean square (RMS) error of CaO estimation using limestone ore fragment was 1.2%. The CaO content estimated by the PLSR method was used to predict average CaO content of composite samples with a sample size of 15, which resulted in an RMS error of 0.3%. The prediction accuracy with moisture on sample surfaces was also examined to find out if the NIR-based method showed a similar RMS error. Results suggest that the NIR technique can be used as a rapid assaying method in limestone workings with or without the presence of groundwater.
Highlights
Limestone is a common sedimentary rock primarily composed of calcium carbonate (CaCO3 )with lesser amounts of calcium magnesium carbonate (CaMg(CO3 )2 )
X-ray diffraction (XRD) analysis showed that the main reason for the lower CaO content of the ore is the presence of reddish clay that infills fractures
We developed and tested a PLS-based technique for the estimation of CaO content using near-infrared spectroscopy (NIR)
Summary
Limestone is a common sedimentary rock primarily composed of calcium carbonate (CaCO3 )with lesser amounts of calcium magnesium carbonate (CaMg(CO3 ) ). Depending on the various mineralogical and chemical compositions of limestone, the extracted ore is used as a source material for a wide range of products such as cement, lime, glass, metallurgical flux, filler and extender. Chemical analysis of limestone is frequently conducted by X-ray fluorescence (XRF), by energy-dispersive XRF, in limestone mining and the cement industry. Detection limits of XRF are element-specific and technique-specific (energy-dispersive or wavelength-dispersive), in general, XRF can accurately measure a wide range of elements with detection limits within ppm levels. Results of XRF are usually reported by element name, e.g., Ca and Mg, whereas the results of the glass bead method can be presented in oxide form, e.g., CaO and MgO, due to the release of CO2 from carbonate minerals during fused bead production.
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