**5. Conclusions**

In this work, a series of multivariate analysis techniques were applied to spectral data obtained during the combustion of chalcopyrite and copper concentrates. The results show that the intensity of the combustion and the spectral characteristics present in the signal depend on the temperature reached by the combustion cloud. The copper concentrates, according to their pyrite content, can reach an intensity such that it allows visualizing some spectral lines, such as those associated with sodium and potassium in the visible range and, even so, the spectral data of all the combustion tests required an exploratory analysis to reveal the presence of spectral lines that are not visible in the average spectrum. The sample that provided the most information on the possible oxidized phases that were generated in the combustion cloud was a high pyrite concentrate sample. The spectral information provided was not only limited to copper oxide emission lines at ~606 and ~616 nm but, instead, there are two emission lines at 779.1 and 793.9 nm that may be associated with iron species, according to some authors. Finally, the application of the MCR-ALS method to a spectral dataset measured from the combustion of a high pyrite concentrate and previous knowledge of spectral bands of Na, FeO, and Fe3O4 patterns allowed us to find a spectral profile associated with copper oxides in the range of 540 and 650 nm.

This research shows that the use of spectral measurement techniques is a powerful tool to relate the spectral emission with physicochemical processes in a combustion flame of copper concentrates. The online and real-time identification of copper oxide formation in a flash furnace flame could be a grea<sup>t</sup> advance for the non-ferrous mineral in the pyrometallurgical industry, improving process control by measuring a few process variables such as copper content in mate or slag.

**Author Contributions:** Conceptualization, W.D., G.R. and C.T.; methodology, W.D., G.R., and C.T.; software, C.T.; validation, W.D., C.T.; formal analysis, W.D., G.R., C.T., and S.T.; investigation, W.D. and G.R.; resources, R.P., E.B. and S.T.; data curation, W.D.; writing—original draft preparation, W.D. and G.R.; writing—review and editing, C.T. and A.V.; visualization, W.D.; supervision, C.T., S.T., E.B. and R.P.; project administration, E.B.; funding acquisition, E.B. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the CONICYT, Anillo Minería ACM170008, and by Fondef IT under Grant Number 16M10029.

**Institutional Review Board Statement:** Not Applicable.

**Informed Consent Statement:** Not Applicable.

**Data Availability Statement:** Data is contained within the article.

**Acknowledgments:** We thank the Metallurgical Engineering Department at the University of Concepción for giving us access to their facilities, allowing us to conduct the experiments reported in this work.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; n\or in the decision to publish the results.
