Quantitative analysis of trace elements (vanadium, sodium, and calcium) in petroleum coke using laser-induced breakdown spectroscopy with binder

Abstract

The concentrations of Vanadium (V), Sodium (Na), and Calcium (Ca) have a great effect on the quality of petroleum coke. In this work, the trace elements of V, Na, and Ca in petroleum coke were determined by laser-induced breakdown spectroscopy (LIBS). First, petroleum coke powder was mixed with the stearic acid binder and pressed into pellets to achieve a high signal repeatability. Then, to optimize the percentage of the binder in the pressed pellets, the influence of stearic acid on LIBS signal was studied in detail. When the stearic accounted for 30 w% in the mixed-pressed pellets, the plasma morphology and spectral signal were more stable. Finally, the linear calibration curves were plotted by fitting the emission line intensities and the element concentrations. In addition, the results achieved through this method were compared with other conventional methods. The determination coefficients of calibration curves of V, Na, and Ca elements all exceed 0.99. The relative standard deviations of the predicted values of V, Na, and Ca concentrations were 3.65%, 4.38%, and 5.53%, respectively. We also calculated the limit of detection of the V, Na, and Ca elements, which were 1.19 mg/kg, 0.41 mg/kg, and 0.51 mg/kg, respectively. The experimental results demonstrate that LIBS detection is an accurate and precision method for the determination of trace elements in petroleum coke.