Laser-induced breakdown spectroscopy; Carbon emission; Plasma temperature; Fly ash; Unburned carbon;ONLINE ANALYSIS; INDUCED PLASMAS; COAL; LIBS; SPECTROMETRY; NITROGEN; BOILER; STEEL; AIR

Laser ablation chemical analysis of fly ash samples was studied by laser-induced breakdown spectroscopy (LIES). Ablation was performed using a 1064 nm Nd:YAG laser in air environment. The molecular emission CN was measured together with the atomic carbon (CI). The combination of atomic and molecular carbon emissions (CI and CN) was available to establish the calibration model for quantitative analysis of the unburned carbon content in fly ash. In order to further improve the measurement accuracy, the matrix effect of fly ash samples was presented and it is found that two lines of the same element in the same order could be used to characterize the plasma temperature. The influence of laser energy on plasmas temperature was studied to estimate the correction factor with the ratio of two Mg ionic lines (Mg II 279.5 nm and Mg II 280.2 nm). The results showed that the combination of carbon atomic and molecular emissions with plasmas temperature correction could improve the accuracy and precision for quantitative analysis of unburned carbon in fly ash samples. (C) 2017 Elsevier B.V. All rights reserved.