Laser-Induced Breakdown Spectroscopy Combined with Temporal Plasma Analysis of C₂ Molecular Emission for Carbon Analysis in Coal

Abstract

A benchtop Laser-Induced Breakdown Spectroscopy (LIBS) is demonstrated to determine the elemental carbon content present in raw coal used for combustion in power plants. The spectral intensities of molecular CN and C2 emission are measured together with the atomic carbon (C) and other inorganic elements (Si, Fe, Mg, Al, Ca, Na, and K) in the LIBS spectrum of coal. The emission persistence time of C2 molecule emission is measured from the coal plasma generated by a nanosecond laser ablation with a wavelength of 266 nm in the Ar atmosphere. The emission persistence time of molecular C2 emission along with the spectral intensities of major ash elements (Fe, Si, Al, and Ca) and carbon emissions (atomic C, molecular CN, and C2) shows a better relationship with the carbon wt% of different coal samples. The calibration model to measure elemental carbon (wt%) is developed by combining the spectral characteristics (Spectral intensity) and the temporal characteristics (Emission persistence time of C2 molecule emission). The temporal characteristic studies combined with the spectroscopic data in the PLSR (Partial Least Square Regression) model has resulted in an improvement in the root mean square error of validation (RMSEV), and the relative standard deviation (RSD) is reduced from 10.86% to 4.12% and from 11.32% to 6.04%, respectively.

Understanding the Surface Condition of Silicone Rubber Nanocomposite Due to Corona Aging Using AFM Imaging and LIBS Spectroscopy

“…When the induced plasma started to cool after the laser pulse is terminated, the excited electrons return to the ground state by making the plasma emit photons. The temporal persistence time of the LIBS emission spectra is measured by capturing the emitted light using the photodiode [29]. The addition of an alumina nanofiller increases the intensity of the emitted spectra and the cooling period as confirmed by the observed increase of the initial magnitude and mean a lifetime of the sample with an increasing filler content.…”