Fixed bed reduction of hematite under alternating reduction and oxidation cycles

摘要

The work presented in this paper focusses on the reduction behavior of hematite as an oxygen carrier for chemical looping applications. In this work, nominally 1 kg samples of the hematite are reacted with methane for nominally 10 minutes of a cycle. A comparison of the data with a model for a single reaction between the methane and the iron oxide shows that the results cannot be obtained with a single reaction. The analysis contained herein shows that the conversion occurs with a fast process that likely consumes all the oxygen close to the surface and a slow process that is likely controlled by the diffusion of oxygen to the surface. Additional analysis shows that the thickness of the fast layer is on the order of 8 unit crystals. This is only about 0.4% of the hematite; however, it comprises about 20 to 25% of the conversion for the 10 min reduction cycle.