Coal Char Reaction with Oxygen Carrier in Chemical Looping Combustion

Chemical-looping combustion is a high-efficiency technology for the conversion of solid fuels and capture of CO2. The reaction of char with an oxygen carrier is a control step in the chemical-looping combustion reaction. In the presence of steam, the rate of char conversion is increased by the reaction of product gases with the oxygen carrier. The reaction system comprises two consecutive reactions. Here, we investigated the reaction of char with two types of oxygen carriers: natural ilmenite and Fe2O3/Al2O3 under an atmosphere of N-2, CO2/N-2, or H2O/N-2. The effect of the oxygen carrier on the water-gas shift reaction was also studied. We found that the rate of the water-gas shift reaction increased with increasing temperature and that the reaction of the char with the oxygen carriers under an H2O/N-2 atmosphere involved two consecutive reactions. The overall activation energy of the two-step consecutive reaction, comprising char gasification and reaction of product gases with an oxygen carrier, was approximately the sum of the activation energies of the individual reactions.