Kinetics of the Oxidation of a Co-precipitated Mixture of Cu and Al₂O₃ by O₂ for Chemical-Looping Combustion

Abstract

A co-precipitated mixture of CuO and Al 2 O 3 is a good oxygen carrier for chemical-looping combustion in, e.g., CuO + CO → Cu + CO 2 . The kinetics of regeneration of this reduced oxygen carrier (particle size of 355−500 μm) by O 2 were measured from 300 to 750 °C. Care was taken to ensure that these measurements were not affected by interphase mass transfer or mixing of gases in the bed and sampling system. The order of reaction with respect to O 2 was found to be approximately unity, and the rates of regeneration in subsequent cycles could be approximated by those in the first. Below 600 °C, oxidation of the reduced oxygen carrier was incomplete. Above 600 °C, oxidation was complete to CuO and was controlled to a considerable extent by external mass transfer. At these higher temperatures, regeneration involved a shrinking core mechanism and the two consecutive steps: (1) (2) At 900 °C, the fully oxidized carrier decomposed to Cu 2 O and O 2 .