Evaluation of red mud as oxygen carrier for chemical looping combustion of methane and biomass in fluidized bed

Abstract

The reaction performance of red mud, which generally contains high amount of Na, as an oxygen carrier for Chemical Looping Combustion (CLC) was evaluated using methane and biomass char as fuel respectively. Effects of reaction temperature and cycles on fuel conversion, particle agglomeration and Na distribution were investigated. Fluidized Bed Thermogravimetric test suggested a stable reactivity during successive redox cycles of the red mud with an oxygen transport capacity of 1.65%. The red mud demonstrates a low reactivity with methane, and a serious agglomeration was found during the fluidized bed experiments with methane due to the further reduction of Fe2O3 to its low state of FeO. It has enough reactivity to oxidize the char gasification productions, thus accelerating the char conversion. The average values of the instantaneous rate increase by 2.82 times at 1143 K, 3.88 times at 1163 K, 3.58 times at 1183 K and 2.0 times at 1203 K in comparison with inert gasification process. Almost no agglomerates formation was found for the CLC investigation using biomass char as fuel. Irrespective of the CLC process of methane or the biomass char, Na exists in a stable phase of NaAlSiO4 with a high melting point and has no influence on particle agglomeration.