Characterization of oxygen carriers for chemical-looping combustion

Abstract

This chapter analyzes the behavior of the different oxygen carriers with respect to selectivity towards complete oxidation products, durability in the cyclic reactions, and attrition and agglomeration during fluidized bed cyclic reactions. In the multicycle tests in thermogravimetric analyzer (TGA), it was observed that most of the oxygen carriers exhibited high reactivity and excellent chemical stability but the Cu and Ni based oxygen carriers prepared by mechanical mixing underwent a rapid degradation of their mechanical properties as the number of cycles increased. The Ni- and the Fe based oxygen carriers did not agglomerate. The attrition rates of the carriers were usually high in the first cycles due to the rounding effects on the particles and because of the fines sticked to the particles during preparation. Later, the attrition rates due to the internal changes produced in the particles by the successive reduction and oxidation processes decreased, and all carriers showed low attrition rates. The product distribution during the oxidation of the fuel depended on the metal oxide used in the oxygen carrier. Complete conversion of CH4 to CO2 and H2O was obtained with the oxygen carrier Cu-AI-I.