Kinetics of CO2/Coal Gasification in Molten Blast Furnace Slag

The coal/CO2 gasification reactions in molten BF (blast furnace) slag were studied kinetically by temperature-programmed thermogravbmetry using a thermal analyzer. The effect of heating rates and molten BF slag on coal gasification were studied, and the activation energies, frequency factors, and most possibility mechanism functions were calculated. The results show that the order of reactivity sequence at these temperatures was DT (Datong) coal > FX (Fuxin) coal > coke. With the increase in heating rate, the carbon conversion, and the peak value of reaction rate increased at the same reaction time, the carbon conversion curve shifts to a higher temperature and the reaction rate curve shifts rightward systematically, both of the time required for the carbon conversion to reach nearly unity and the time necessary for reaction rate to reach its maximum decreased. The carbon conversion and reaction rates were sensitive to BF slag; at the same time, the carbon conversion and reaction rates of coal gasification with slag are higher than those without slag. The time required for the carbon conversion to reach nearly unity and the time required for the reaction rate to reach maximum with slag are both shorter than that without slag. In the presence of BF slag, the carbon conversion curve shifts to lower temperature, the peak value of reaction rate is higher than that without slag, and the reaction rate curve also shifts to lower temperature. The molten BF slag acts as a good catalyst to coal gasification. Without molten BF slag, the mechanism functions of coke and FX coal are a C-1 model (phase boundary reaction (n = 2) model), while the mechanism function of DT coal is a C-2 model (phase boundary reaction (n = 3/2) model). However, with molten BF slag, the mechanism function of coke is a D-5 model (3-D diffusion (anti-Jander) model), the mechanism function of DT coal is a D-4 model (3-D diffusion model), and the mechanism function of FX coal is a C-2 model (phase boundary reaction (n = 3/2) model). The activation energies and frequency factors decrease as heating rates increase. The kinetic compensation effect of coal/CO2 gasification in molten BF slag exists.