Quantitative analysis of Fe and detection of multiple elements in the coal ash by laser-induced breakdown spectroscopy

Sulfates produced by the reaction of metal oxides in coal ash with the acid gases in the atmosphere are the main causes of haze-fog formation. In this study, laser induced breakdown spectroscopy(LIBS) was used for elemental analysis in coal ash. A new method was adopted to conduct an accurate qualitative analysis of the four elements (Al, Ca, Cu and Fe) that easily form sulfates in coal ash. An internal standard method was used to quantitatively analyze the typical Fe element of the four elements with a calibration curve that had a linear correlation coefficient (R-2) of 0.986. In order to test the accuracy of the curve, three kinds of coal ash with unknown composition were selected and analyzed by LIBS and X-ray fluorescence spectrometry (XRF). The relative differences of the two methods were around 7.42%, 3.37% and 4.34%, respectively, which are all in the acceptable range. The experimental results indicate that LIBS can be employed for the rapid detection and analysis of metal elements in coal ash and provide a new classification method for coal ash based on the content of Fe element.