Oxidation and reduction characteristics of oxygen carrier particles and reaction kinetics by unreacted core model

The reaction kinetics of the oxygen carrier particles, which are used as be d material for a fluidized bed chemical looping combustor (CLC), has been s tudied experimentally by a conventional thermal gravimetrical analysis tech nique. The weight percent of nickel and nickel oxide in oxygen carrier part icles and reaction temperature were considered as experimental variables. A fter oxidation reaction, the pure nickel particle was sintered and unsuitab le to use as fluidizing particles. The oxidation reaction rate increased wi th increasing weight percent of nickel in oxygen carrier particles and reac tion temperature. The rate of reduction shows maximum point with weight per cent of nickel oxide (57.8%) and reaction temperature (750 or 800 degreesC) increased. In this work, the reaction between air and Ni/bentonite particl e was described by a special case of unreacted core model in which the glob al reaction rate is controlled by product layer diffusion resistance. Howev er, the reaction between CH4 and NiO/bentonite particle was described by un reacted core model in which the global reaction rate is controlled by chemi cal reaction resistance. The temperature dependence of the effective diffus ivity of oxidation reaction and reaction rate constant of reduction reactio n could be calculated from experimental data and fitted to the Arrhenius eq uation.