Reduction Kinetics of Cu-, Ni-, and Fe-Based Oxygen Carriers Using Syngas (CO + H2) for Chemical-Looping Combustion
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- 作者：Alberto Abad ; Francisco Garcí ; a-Labiano ; Luis F. de Diego ; Pilar Gayá ; n ; Juan Adá ; nez
- 刊名：Energy & Fuels
- 出版年：2007
- 出版时间：July 2007
- 年：2007
- 卷：21
- 期：4
- 页码：1843 - 1853
- 全文大小：189K
- 年卷期：v.21,no.4(July 2007)
- ISSN：1520-5029
文摘
The reactivity of three Cu-, Fe-, and Ni-based oxygen carriers to be used in a chemical-looping combustion(CLC) system using syngas as fuel has been analyzed. The oxygen carriers exhibited high reactivity duringreduction with fuel gases present in syngas (H2 and CO), with average values in the range 8-30% min-1. Noeffect of the gas products (H2O, CO2) on the reduction reaction rate was detected. The kinetic parameters ofreaction with H2 and CO have been determined by thermogravimetric analysis. The grain model with sphericalor platelike geometry in the grain was used for the kinetic determination, in which the chemical reactioncontrolled the global reaction rate. The activation energies determined for these reactions were low, with valuesranging from 14 to 33 kJ mol-1. The reaction order depended on the reacting gas, and values from 0.5 to 1were found. Moreover, the reactivity of the oxygen carriers when both H2 and CO are simultaneously presentin the reacting gases has been analyzed, both at atmospheric and pressurized conditions. For the Cu- andFe-based oxygen carriers, the reaction rate of the oxygen carrier with syngas corresponded to the addition ofthe reaction rates for the individual fuel gases, H2 and CO. For the Ni-based oxygen carrier, the reaction ratewas that corresponding to the fuel gas that reacted faster with the oxygen carrier at the reacting conditions(fuel concentration, temperature, and pressure). The consequences of the behavior of the reaction of syngasand the water-gas shift (WGS) equilibrium on the design of the fuel reactor of a CLC system have beenanalyzed. A preliminary estimation of the solids inventory for the use of syngas in the fuel reactor of a CLCsystem gave values in the range of 19-34 kg MW-1 when the WGS equilibrium was considered to beinstantaneous.