Dynamic behaviors of the sodium, calcium and iron release during coal combustion using multi-point LIBS

摘要

? 2022 The Combustion InstituteA novel application of multi-point LIBS was used to investigate the mineral release for dispersed-particle streams during coal combustion in an enclosed laminar flow reactor. A 1064 nm Nd: YAG laser was used to ablate the pulverized coal in air-like combustion environments at atmospheric pressure. The electron temperature (Te) and electron density (Ne) were calculated to evaluate the characteristics of the laser-induced plasma along the height from the burner surface, and LS-coupling method was further used to distinguish whether self-absorption occurred. The particle temperature was measured by a two-color pyrometer, and the time-resolved behaviors of Na, Ca and Fe along with the combustion process were measured by LIBS. Results show that the Te and Ne of laser-induced plasmas decreased with the flow of coal flame upon devolatilization, and became relatively stable during char combustion. There was little atomic self-absorption during char-combustion process, which provided theoretical support for quantitative combustion analysis. The Na release, mainly atomic forms, decreased with the particle flow upon devolatilization and showed a trend from rise to decline following devolatilization. The Fe and Ca was rarely released upon devolatilization. During char combustion, the Ca have a similar behavior to Na release, while the Fe increased and then remained constant. The temperature dependent kinetics of the Na and Ca release rate was found to obey an Arrhenius expression. The kinetics of Na and Ca atomic release determined by a first-order model had the pre-exponential factor of 101.16 and 102.67 s?1 and the activation energy of 87.2 and 150.8 kJ/mol, respectively.