Abstract
In this paper, we report on the spectral detection of wustite, Fe(II) oxide (FeO), and magnetite, Fe(II, III) oxide (Fe3O4), molecular emissions during the combustion of pyrite (FeS2), in a laboratory-scale furnace operating at high temperatures. These species are typically generated by reactions occurring during the combustion (oxidation) of this iron sulfide mineral. Two detection schemes are addressed: the first consisting of measurements with a built-in developed spectrometer with a high sensitivity and a high spectral resolution. The second one consisting of spectra measured with a low spectral resolution and a low sensitivity commercial spectrometer, but enhanced and analyzed with post signal processing and multivariate data analysis such as principal component analysis (PCA) and a multivariate curve resolution—the alternating least squares method (MCR-ALS). A non-linear model is also proposed to reconstruct spectral signals measured during pyrite combustion. Different combustion conditions were studied to evaluate the capacity of the detection schemes to follow the spectral emissions of iron oxides. The results show a direct correlation between FeO and Fe3O4 spectral features intensity, and non-linear relations with key combustion variables such as flame temperature, and the combusted sulfide mineral particle size.
Highlights
The copper pyrometallurgy industry is facing many challenges regarding the increase of production and more strict demands on environmental compliance regulations
The need for developing online sensing technologies aimed at monitoring the temperature and the chemical composition of the molten phases during the slag and copper tapping period and during the copper concentrate feeding is crucial to enhance the energy and production efficiency, gas emission control and general optimization of the copper making processes [1,2]
The combustion inside the reactor form two molten phases in the settler located at the bottom, namely, the matte that contains most of the copper fed as sulfide, and the slag having most of the iron fed as oxide
Summary
The copper pyrometallurgy industry is facing many challenges regarding the increase of production and more strict demands on environmental compliance regulations. To the best of our knowledge, there are no reported online industrial monitoring systems aimed at the detection of the presence of iron oxides or any other species in the copper flash smelting process. Arias et al [2] reported some spectral features found in radiation emitted from copper concentrate flash smelting and applied optical pyrometry techniques for temperature estimation. The main goal of this manuscript is to apply spectral measurement techniques and mathematical methods to analyze the combusted iron sulfide pyrite spectral information to detect molecular emission intensities. The second procedure involves calibrated measurements with a commercial medium spectral resolution (0.12 nm) spectrometer, signal processing techniques and multivariate methods such as the principal component analysis (PCA) [14], for an exploratory analysis.
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