Analysis of Lakhra Coal by Calibration Free Laser-Induced Breakdown Spectroscopy (CF-LIBS) and Comparison of Self-Absorption Correction Procedures

Abstract

The analysis of Lakhra Coal to determine its total carbon content and ash content is reported by calibration-free laser-induced breakdown spectroscopy (CF-LIBS). The total carbon content and ash content in coal are key parameters for efficient energy u in sepower plants. The optical emission spectrum of coal contains spectral lines of Ca, Si, Fe, Ti, Mg, Na, K, Li, Al, and C together with traces of Ba and Sr. The excitation temperature and electron number density of the laser-produced plasma were estimated using a Boltzmann plot and Stark broadened Hα line, respectively. The self-absorption correction in the emission intensities of the spectral lines were performed using the internal reference self-absorption correction (IRSAC) and the density correction. The analysis of the coal was performed by CF-LIBS, CF-LIBS with IRSAC, and CF-LIBS with density correction which were then compared with the certified composition reported by the Lakhra Coal Development Company. The results revealed that IRSAC with a fixed slope is more easily applicable and reliable than the number density correction for analyzing the total carbon content, ash content, and trace elements.

KEYWORDS:

• Calibration-free laser-induced breakdown spectroscopy (CF-LIBS)
• coal
• number density correction
• self-absorption correction
• total carbon content