Study on the ignition characteristics and alkali release of single coal particles with additional different forms of potassium

The work concerned the ignition characteristics and alkali metals (Na and K) release behavior during the combustion process of single coal particles with the additional different forms of K contents. The measurement was performed in O-2/N-2 and O-2/CO2 atmospheres. The high-speed camera was used to investigate the influences from different forms of potassium (KCl and K2CO3) on the ignition characteristics, and the temporal release behaviors of alkali metals were obtained with the detection of atomic emission spectrum of alkali metals (Na and K). The sample with additive of KCl has the higher emission intensity and lower ignition delay than that the sample with additive of K2CO3. The substituting CO2 for N-2 had more effect for KCl than for K2CO3 addition in the initial stage of volatile combustion, but it reversed as burning progressed. The comparison of the gas phase temperature during the ignition with the appearance moment of the K emission could be further illustrated that the main reason affecting the release of atomic alkali metals was the presence of different form of potassium, which affected the liberation and diffusion rate of the volatiles.