Ya-Ning Zou, Chong Zou, Nan Yu, Wei-Guang Zhang, Meng-Meng Ren, Rui-Meng Shi, Shi-Wei Liu
To address the kinetic constraints inherent in the catalytic combustion of pulverized coal injection under low heating-rate conditions within conventional air atmospheres, a drop tube furnace was utilized to simulate the catalytic combustion of pulverized coal (PC). The effects of gas composition, oxygen concentration, the type, and the content of catalysts on the combustion reactivity were systematically analyzed. Furthermore, the structural changes of unburned pulverized coal were also examined. Experimental results indicate that as the oxygen concentration increased from 21% to 79%, compared with the O2/N2 condition, the increment in the burnout rate of PC under the O2/CO2 condition increased from 3% to 23%. After the addition of catalysts, including hematite, metallurgical oil sludge, and light-burnt dolomite (LBD), under the condition of 21% oxygen concentration, the effects of the three catalysts under the O2/CO2 condition were superior to those under the O2/N2 condition. This trend was reversed under the conditions of 38% and 79% oxygen concentrations. In all atmospheres, the three catalysts can enhance the burnout rate of PC. Among them, LBD exhibits the most favorable effect, and there exists an optimal dosage. Mechanistic analysis through scanning electron microscopy, X-ray diffraction, and N2 adsorption-desorption reveals that under 21% O2/79% CO2 conditions, high-concentration CO2 leads to the formation of pores, and additives accelerate the oxidation of C and the gasification of CO2 through oxygen transfer, thereby enhancing the burnout rate of PC.
