Kinetics of Iron Ore Reduction by Methane for Chemical Looping Combustion

Abstract

Due to increasing atmospheric carbon dioxide (CO2) concentration, energy sources that release smaller amounts of CO2 to the atmosphere are of considerable interest. Attention is also now being paid to sequestering CO2 from the combustion process and eliminating discharge to the atmosphere from the major source points. Chemical-looping combustion (CLC) is a promising concept that can be used in power generation, which integrates power production and CO2 capture. In the present study, a commercially obtained iron ore was used as an oxygen carrier and the associated reduction reaction kinetics parameters have been estimated based on isothermal thermogravimetric analysis (TGA) in reducing environments. The iron oxide in the ore, which is initially Fe2O3, proceeds through a sequence of reaction steps and can ultimately end up as metallic iron. The reduction mechanism for the first stage reaction (i.e., Fe2O3 to Fe3O4) was evaluated using a number of different gas–solid reaction models. The results indicate that the Avrami–Erofe’ev model can be successfully applied to the experimental data. Through this approach, it was confirmed that the initial reaction stage is phase-boundary-controlled, which gradually transitions to diffusion control. The apparent activation energy was estimated and compared with values from the literature data.