Fundamental study of the pulverized coal char combustion in oxyfuel mode with drop tube furnace

Abstract

The combustion characteristics of coal char particles in either O 2/N2 or O2/CO2 conditions were experimentally investigated. Especially, the char burnout, the char particle temperature and the shrinkage of the char particles were discussed. A Drop Tube Furnace (DTF: whose wall temperature was set at 873 K, 923 K and 973 K) was used as the experimental apparatus. The experimental results revealed that, in equivalent oxygen concentration, the char burnout and the char particle temperature were higher in O2/N2 conditions than those in O2/CO2 conditions. The shrinkage of the char particle did not show the large difference in either O2/N2 or O 2/CO2 conditions. Up to 15% of char burnout, the char particle diameters were reduced gradually. Up to 80% of char burnout, the char particle diameters were not changed. This is supposed that the chemical reaction is mainly occurred not on the external surface but on the internal surface of the char particle. Over 80% of char burnout, sudden shrinkage could be seen. Finally, an empirical equation for the prediction of the char particle shrinkage was introduced. Further investigation is required in high operating temperature, where CO2 gasification may have a large influence on the char burnout. © Tsinghua University Press, Beijing and Springer-Verlag Berlin Heidelberg 2012.