Quantitative Concentrations of Sodium and Potassium Released from Brown Coal and Pine Wood in a Laminar Premixed Flame Using LIBS

A quantitative point measurement of total sodium and potassium released during combustion of Australian Loy Yang brown coal particles (23 3 mg) and pine wood pellets (63 3 mg) has been performed using laser-induced breakdown spectroscopy (LIBS) in a laminar premixed methane flame at the equivalence ratio (Φ) of 1.287. Calibration was performed using droplets of sodium sulfite (Na2SO3) and potassium sulphate (K2SO4) entrained into the flame. This compensated for the absorption caused by atomic alkalis in outer seeded flame, which is significant at high concentrations. Hence quantitative release of sodium and potassium during the three phases of combustion, namely devolatilization, char and ash cooking, were obtained. The concentration of total sodium in the plume released from the combustion of pine wood pellets during the devolatilization reached up to 15 ppm. The strongest concentrations of total sodium and potassium released from burning coal and wood particles during char phase were found to be 21.3 and 2.4 ppm, 15.5 and 26.3 ppm, respectively.