Reduction and oxidation kinetics of Mn3O4/Mg–ZrO2 oxygen carrier particles for chemical-looping combustion

The kinetics of reduction with methane and oxidation with oxygen of Mn3O4 supported on Mg–ZrO2 prepared by freeze granulation has been investigated. The reactivity experiments were performed in a thermogravimetric analyzer (TGA) using different reacting gas concentrations and temperatures in the range of 1073–1223 K. The oxygen carrier particles showed high reactivity during both reduction and oxidation at all investigated temperatures. An empirical reaction model, which assumes a linear relation between time and conversion, was used to determine the kinetic parameters for reduction and oxidation, with chemical reaction being the main resistance to the reaction. The order of reaction found was 1 with respect to CH4 and 0.65 with respect to O2. The activation energy for the reduction reaction was 119 and 19kJmol-1 for the oxidation reaction. The reactivity data and kinetic parameters were used to estimate the solid inventory in the air and fuel reactor of a CLC system. The optimum solid inventory obtained was 135kgMWf-1 at a value of ΔXs=0.4ΔXs=0.4. At these conditions, the recirculation rate of oxygen carrier between air and fuel reactor was 7.1kgs-1 per MW of fuel, which could be accomplished in an industrial reactor. The high reactivity of the Mn3O4/Mg–ZrO2 with both methane and oxygen showed that this is a very promising oxygen carrier for CLC.

[1]  A. Abad,et al.  Reduction and Oxidation Kinetics of a Copper-Based Oxygen Carrier Prepared by Impregnation for Chemical-Looping Combustion , 2004 .

[2]  Anders Lyngfelt,et al.  Investigation of Mn3O4 With Stabilized ZrO2 for Chemical-Looping Combustion , 2006 .

[3]  Jeong-Hoo Choi,et al.  Oxidation and reduction characteristics of oxygen carrier particles and reaction kinetics by unreacted core model , 2001, Korean Journal of Chemical Engineering.

[4]  Toshihiro Okamoto,et al.  A Fundamental Study of a New Kind of Medium Material for Chemical-Looping Combustion , 1996 .

[5]  A. Abad,et al.  Mapping of the range of operational conditions for Cu-, Fe-, and Ni-based oxygen carriers in chemical-looping combustion , 2007 .

[6]  A. Lyngfelt,et al.  Reactivity of some metal oxides supported on alumina with alternating methane and oxygen - Application for chemical-looping combustion , 2003 .

[7]  T. Mattisson,et al.  Redox investigation of some oxides of transition-state metals, Ni, Cu, Fe, and Mn Supported on SiO2 , 2005 .

[8]  A. Lyngfelt,et al.  Comparison of iron-, nickel-, copper- and manganese-based oxygen carriers for chemical-looping combustion , 2004 .

[9]  Anders Lyngfelt,et al.  Defluidization Conditions for a Fluidized Bed of Iron Oxide-, Nickel Oxide-, and Manganese Oxide-Containing Oxygen Carriers for Chemical-Looping Combustion , 2006 .

[10]  A. Abad,et al.  Temperature variations in the oxygen carrier particles during their reduction and oxidation in a chemical-looping combustion system , 2005 .

[11]  S. D. Kim,et al.  Chemical-Looping Combustion with NiO and Fe2O3 in a Thermobalance and Circulating Fluidized Bed Reactor with Double Loops , 2006 .

[12]  Tobias Mattisson,et al.  Integrated hydrogen and power production with CO2 capture using chemical-looping reforming-redox reactivity of particles of CuO, Mn 2O3, NiO, and Fe2O3 using SiO 2 as a support , 2005 .

[13]  D. Zheng,et al.  Evaluation of a chemical-looping-combustion power-generation system by graphic exergy analysis , 1987 .

[14]  J Baeyens,et al.  Gas fluidized beds operating at high velocities: a critical review of occurring regimes , 2001 .

[15]  Richard Blom,et al.  Chemical looping combustion using NiO/NiAl2O4 : Mechanisms and kinetics of reduction-oxidation (Red-Ox) reactions from in situ powder X-ray diffraction and thermogravimetry experiments , 2006 .

[16]  A. Abad,et al.  Chemical Looping Combustion in a 10 kWth Prototype Using a CuO/Al2O3 Oxygen Carrier: Effect of Operating Conditions on Methane Combustion , 2006 .

[17]  Chang-Keun Yi,et al.  Demonstration of inherent CO2 separation and no NOx emission in a 50kW chemical-looping combustor: Continuous reduction and oxidation experiment , 2005 .

[18]  Octave Levenspiel,et al.  The chemical reactor minibook , 1979 .

[19]  Börje Sten Gevert,et al.  Reaction Kinetics of Freeze-Granulated NiO/MgAl2O4 Oxygen Carrier Particles for Chemical-Looping Combustion , 2007 .

[20]  Anders Lyngfelt,et al.  The GRACE project. Development of oxygen carrier particles for chemical-looping combustion. Design and operation of a 10 kW chemical-looping combustor , 2004 .

[21]  A. Lyngfelt,et al.  A fluidized-bed combustion process with inherent CO2 separation; Application of chemical-looping combustion , 2001 .

[22]  A. Abad,et al.  Selection of Oxygen Carriers for Chemical-Looping Combustion , 2004 .

[23]  E. R. Stobbe,et al.  The reduction and oxidation behaviour of manganese oxides , 1999 .

[24]  Anders Lyngfelt,et al.  Chemical-looping combustion in a 300 W continuously operating reactor system using a manganese-based oxygen carrier , 2006 .

[25]  R. Villa.  Ni based mixed oxide materials for CH4 oxidation under redox cycle conditions , 2003 .