Inhibition evaluation of magnesium hydroxide, aluminum hydroxide, and hydrotalcite on the flame propagation of coal dust

Abstract

Coal dust suspended in a syngas atmosphere may result in a dust explosion during the coal gasification process. A vertical tube with a high-speed camera and thermocouple was built to investigate the flame propagation characteristics of coal dust. Magnesium hydroxide (MH), aluminum hydroxide (ATH), and hydrotalcite (HT) were selected as the inhibitors to compare their inhibition effect. The results showed that the effects of the three inhibitors differed greatly. The addition of MH prolonged the flame propagation time, but its inhibition of flame temperature was the worst. The peak temperature and velocity of the flame after the addition of HT were the smallest compared to that after the addition of MH and ATH. Besides, the analysis of residues proved that the unburned coal dust was completely encapsulated by the high-temperature resistant oxides from HT so that the coal dust was most effectively protected, which showed the best heat absorption properties and the lowest decomposition temperature compared with that of MH and ATH.