A Kinetic Modelling Study of the Effect of Selected Impurities on the Ignition of Crude Glycerol

The effect of impurities in crude glycerol on its ignition and the associated chemistries and mechanisms were examined using Chemkin kinetic modelling. A specific attention was paid to the effect of methanol, biodiesel, and water. The reaction mechanisms of the selected impurities were obtained from the literature to form reaction chemistries of the glycerol-methanol-biodiesel mixture. The closed homogeneous model was used to predict the ignition delay time. A sensitivity analysis was performed to identify the key elementary reactions determining the role of impurities in affecting ignition of glycerol. The results showed that the ignition delay time increased with increasing water concentration, while decreased with increasing methanol or biodiesel concentration. This is in accordance with the observations in the ignition experiments using single droplets of glycerol. A reaction pathway analysis showed that the presence of methanol or biodiesel enhanced the production of the O and OH radicals, thus promoting ignition. However, water consumed the O radicals and subsequently delayed the ignition of glycerol.