Experimental study of the influence of synergistic effects on the co-firing characteristics of biomass and coal

Co -firing biomass with coal is a promising strategy for utilizing biomass as a viable alternative to fossil fuels in stationary energy conversion. Investigating the combustion characteristics of specific biomass types when cofiring with coal is beneficial for its efficient utilization. In this study, a biomass with high potassium (K) content, chestnut shells (CNS), was chosen as the potential biomass for small to medium-scale co-firing with coal. The co-firing characteristics were examined by flame emission spectroscopy and image processing on a Hencken burner. The results showed that the ignition delay time, volatile flame temperature, gas phase K release of the blended pellets exhibited nonlinear changes with the increasing CNS blending ratio, demonstrating obvious synergistic effects, which were most obvious at a blending ratio of 50 % CNS. The burnout ash compositions and the element content were analyzed. The results also showed abnormal changes at a 50 % CNS ratio, especially calcium and iron. Different mineral crystal phases were observed at varying CNS ratios, suggesting that ashrelated issues such as fouling and slagging may vary when co-firing at different ratios. Mineral transformation in coal ash plays a crucial role in generating synergistic effects during the char burnout stage.