In-situ measurement method of material ratio and chemical uniformity in sintering–pelleting operation using laser-induced breakdown spectroscopy and partial least squares regression

Abstract

The testing cycle, analyzing accuracy and precision of material ratio and chemical uniformity of sintering–pelleting operation directly affect the return fines ratio and economic benefits in the steel industry. In this work, we present an in-situ measurement method, which mainly includes sample preparation, laser-induced breakdown spectroscopy (LIBS) measurement and data processing. Twelve mixture samples composed of Fe2O3, CaO and C powder materials with different concentrations were prepared and measured. The raw spectra were pre-processed with baseline, de-noise, peak finding, sum normalized, line matchning, and feature selection. Important variables of Fe, Ca and C elements were acquired and selected based on partial least squares regression coefficients (PLS-RC) and domain knowledge, and the relationship between the spectral intensity and the certified concentration information was modeled using partial least squares regression (PLSR). After data-processing, the relative standard deviation (RSD) values of Fe I (403.05 nm), Ca I (430.77 nm) and C I (247.85 nm) were optimized to be 4.20 %, 5.29 % and 7.64 %, respectively. Moreover, the coefficient of determination (R2) values of Fe, Ca and C are 98.02 %, 98.43 % and 97.18 %, respectively; the root-mean-square error (RMSE) values are 0.024, 0.010, and 0.014, respectively; and the mean absolute error (MAE) values are 0.019, 0.008, and 0.011, respectively. The evaluation demonstrated that the presented LIBS system can basically satisfy the requirement the industry standards for in-situ material ratio and uniformity analysis in sintering–pelleting operation. Therefore, the proposed in-situ LIBS measuring method has great development potential and is widely applied in sintering–pelleting operations and similar processes.