Oxy-Combustion of Low-Volatility Fuel With High Water Content

High water content fuels , such as coal fine , microalgae and bioethanol , are abundant in nature. Fundamental study is necessary to investigate the novel idea of direct combustion of high water content fuels , which avoids the energy intensive dewatering process. Our previous research investigated the flame stability for high-volatility fuels , including ethanol , 1-propanol and t-butanol. In this study , we continue the study and focus on low-volatility fuel and glycerol is chosen as the candidate. It is found that self-sustained flame can only be obtained for glycerol solution with concentration higher than 50 wt% , when it is burned in pure O2. However , the flame is lifted far away from the nozzle , which is not typical for a swirl stabilized burner. Knowing ethanol having strong preferential vaporization over water from previous study , ethanol was added as additive to enhance the flame stability. Experiment showed that anchored flame can be obtained by burning the mixture of 10 wt% ethanol , 30 wt% glycerol and 60 wt% water under oxy-fired condition. The flame stability for this mixture was characterized under 100% and 85% swirl flow conditions. It is found in our previous research that t-butanol shows even stronger preferential vaporization behavior than ethanol. The flame stability for the mixture of 8.3 wt% t-butanol , 30 wt% glycerol and 61.7 wt% water , which has the same energy content as the mixture of 10 wt% ethanol , 30 wt% glycerol and 60 wt% water , was characterized under the same flow conditions as ethanol case. Under 100% swirl flow condition , the blow-off limits are approximately the same for both cases. Under 85% swirl flow condition , the blow-off limits for t-butanol case are much lower in the low flow rate region. Additionally , the lift-off limits for t-butanol case are shifted to the left compared to the ethanol case , which means the flame stability for t-butanol case is better. Further , flame structure was characterized. Contours of temperature across the chamber’s centerline were obtained for flame burning 10 wt% ethanol , 30 wt% glycerol and 60 wt% water under three different running conditions , including 100% O2 and 100% swirl , 100% O2 and 85% swirl , 80% O2 and 100% swirl. It is found the anchored flame becomes narrower as the swirl intensity decreases and the peak temperature zone shifts downstream as the O2 concentration decreases.