Experimental verification on correction factor of oxygen mass transfer in char oxy-fuel combustion

Stefan flow is often neglected in the studies of reaction rate and numerical simulation for char oxy-fuel combustion. It has been proved in our previous works that Stefan flow has significant effects on the mass transfer and heat balance of a char particle burning in O₂/CO₂ atmosphere. In this paper, diffusion coefficient of O₂ was measured by using a thermobalance for different coal chars in the oxy-fuel combustion. These coals include an anthracite, a sub-bituminous, and a lignite. The O₂ concentration varies from 15% to 40%. The reaction temperatures were set to be 1100 °C. The char burned approximately under the diffusion control. The measured transfer coefficient changed with the gaseous composition, char type and Stefan flow. Also, the results were compared with the corrected/ uncorrected theoretical diffusion coefficient. It is concluded that uncorrected theoretical diffusion coefficient greatly deviated from the experimental results while a correction factor to the O₂ transfer could improve it. The feasibility and necessity of the correction factor was verified sucessfully.