In-situ Measurement of Sodium and Potassium Release during Oxy-Fuel Combustion of Lignite using Laser-Induced Breakdown Spectroscopy: Effects of O_2 and CO_2 Concentration

摘要

Laser-induced breakdown spectroscopy (LIBS) was used in this study to measure quantitatively the sodium (Na) and potassium (K) release from burning coal particles under oxy-ruel combustion environments. A specially designed laminar premised burner was employed to provide a postflame environment with different O_2 and CO_2 concentrations, in which the effects of O_2 and CO_2 on the release of Na and K during coal oxy-fuel combustion were studied systematically. For the devolatilization stage, neither O_2 nor CO_2 had significant influence on the Na and K release. The release of Na and K during the char stage, however, changed significantly at different O_2 and CO_2 concentrations. Under these experimental conditions, when the O_2 concentration increased from 3.9% to 10.6%, the peak concentration of Na at the char stage increased from 1S.2 mg/m~3 to 33.7 mg/m~3, and the maximum concentration of K increased from 6.2 mg/m~3 to 11.7 mg/m~3. When the CO_2 concentration increased from 35.8% to 69.4%, the release of Na and K was inhibited during the char stage, with the peak concentration decreasing from 8.9 mg/m~3 to 6.9 mg/m~3 for Na and from 3.7 mg/m~3 to 2.4 mg/m~3 for K. During the ash stage, the release of Na and K decreased with the O_ 2 concentration, whereas it increased with the CO_2 concentration.