Effects of oxygen concentration on devolatilization and combustion behavior of coal particles: A multi-parameter study

摘要

The devolatilization and volatile combustion of lignite coal (LC), sub-bituminous coal (SBC) and bitumi-nous coal (BC) with different O 2 concentrations (21%-50%) were investigated on a concentrating pho-tothermal experiment platform. The characteristics and mechanism of different coal particle combustion were analyzed by using multiple diagnostics, including Planar Laser Induced Fluorescence (PLIF) of OH radicals and polycyclic aromatic hydrocarbons (PAHs), high-speed cinematography and FT-IR. The results showed that, with increasing O 2 concentration, the ignition delay time (tign) of different ranks of coal de-creased, which was associated with the increase of OH concentrations during the ignition stage. The good correlation between tign and OH concentration was observed. For the volatile combustion, the OH con-centration, volatile release amount and volatile flame duration time (tvol) significantly increased with the increasing of O 2 concentration at low O 2 concentrations. In the higher O 2 concentrations, coals with dif-ferent PAHs generation amount responded differently on the increasing of O 2 concentration. On one hand, for the coals with lower PAHs generation amount, the OH concentration increased with the increasing of O 2 concentration, while the tvol was not sensitive to changes of the O 2 concentration. On the other hand, for the coals with higher PAHs generation amount, the OH concentration decreased with the increasing of O 2 concentration while the tvol increased with the increasing of O 2 concentration. It can be concluded that PAHs inhibited the OH generation, and the generation characteristics of OH and PAHs affected the sustained state of volatile combustion. The higher PAHs concentration consumed higher amount of OH during the volatile combustion. Meanwhile, with the increasing of PAHs concentration, the reaction rate of H + O 2 + M -> HO2 + M in which PAHs participate was increased, inhibiting the reaction H + O2 -> OH + O , and the increasing of polymer soot of PAHs will reduce the flame temperature through thermal radiation, which further inhibited the OH formation. (c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.