A physical modification and spectrum-image fusion dual-dimensional method for coal analysis using LIBS

Abstract

Elemental analysis of coal is essential for combustion optimization and pollution reduction. Laser-induced breakdown spectroscopy (LIBS) is a rapidly rising coal measurement technique, because of its advantages such as limited sample pretreatment, minimally destructive nature and online capabilities. However, the severe nonlinear response between plasma temperature and image occurs in coal LIBS analysis, which is one of the causes of matrix effects and limited quantitative accuracy. To improve the analysis accuracy, a novel calibration method named plasma temperature correction method of physical modification and spectrum-image dual-dimensional fusion based on LIBS (PTPI-LIBS) was proposed. This method homogenizes the plasma state and ensures a realistic match between the plasma and its image. It further uses plasma image brightness to characterize the temperature and to achieve consistency in correction parameters across different plasmas. As a result, it effectively establishes a reliable response among different plasmas, which eliminates the influence of matrix effects on elemental quantification. To verify the feasibility of PTPI-LIBS, element analysis of coal was carried out. After correction by PTPI-LIBS, the R² of the calibration curves for C, N, and H elements all improved to above 0.993, and the average RMSE decreased by 80%. These experimental results demonstrate that PTPI-LIBS can effectively eliminate the influence of matrix effects on coal LIBS elemental detection and improve analysis accuracy. In summary, PTPI-LIBS presents a potential approach for the application of LIBS in the energy industry.