Effects of potassium additives on the combustion behavior of chrysanthemum biochar blended with graphite carbon as a heating source for heat-not-burn tobacco

Heat-not-burn tobacco with an external heating source is a cleaner alternative to conventional cigarettes due to its lower emission of nicotine, CO and tar in the smoke, and the co-combustion of the composite carbon source (chrysanthemum biochar blended with graphite carbon) is a promising carbon heating source for a heat-not-burn tobacco product. This work has investigated the effect of the blending ratio of the graphite carbon on the co-combustion characteristics (i.e., the minimum ignition temperature, the burnout temperature, etc.) of the composite carbon source, as well as the effect of K2CO3 on the co-combustion behaviors. The results indicate that the minimum ignition temperature is mainly controlled by the ignition of the biochar while the burnout temperature is dominated by that of the graphite. The minimum ignition temperature of the carbon mixture is decreased by only 2-17 degrees C with K2CO3 because the ignition temperature of the biochar is difficult to reduce further by adding K2CO3. Simultaneously, the burnout temperature can be reduced by 30-60 degrees C since the graphite firing can be significantly improved by the presence of K2CO3. Moreover, the promotion effect of K2CO3 on the co-firing process is not always proportional to the addition amount of the catalyst, especially when the mass fraction of the graphite exceeds the threshold value of 30% based on the observation of the activation energies from the third-order kinetic model analysis.