Effect of Pressure on the Behavior of Copper-, Iron-, and Nickel-Based Oxygen Carriers for Chemical-Looping Combustion

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• 作者：Francisco Garc&iacute ; a-Labiano ; Juan Adá ; nez ; Luis F. de Diego ; Pilar Gayá ; n ; and Alberto Abad
• 刊名：Energy & Fuels
• 出版年：2006
• 出版时间：January 2006
• 年：2006
• 卷：20
• 期：1
• 页码：26 - 33
• 全文大小：194K
• 年卷期：v.20,no.1(January 2006)
• ISSN：1520-5029

文摘

The combustion process integrated by coal gasification and chemical-looping combustion (CLC) could beused in power plants with a low energy penalty for CO₂ capture. This work analyzes the main characteristicsrelated to the CLC process necessary to use the syngas obtained in an integrated gasification combined cycle(IGCC) power plant. The kinetics of reduction with H₂ and CO and oxidation with O₂ of three high-reactivityoxygen carriers used in the CLC system have been determined in a thermogravimetric analyzer at atmosphericpressure. The iron- and nickel-based oxygen carriers were prepared by freeze-granulation, and the copper-based oxygen carrier was prepared by impregnation. The changing grain size model (CGSM) was used for thekinetic determination, assuming spherical grains for the freeze-granulated particles containing iron and nickeland a platelike geometry for the reacting surface of the copper-based impregnated particles. The dependenceof the reaction rates on temperature was low, with the activation energy values varying from 14 to 33 kJmol^-1 for the reduction and 7 to 15 kJ mol^-1 for the oxidation. The reaction order depended on the reactinggas and oxygen carrier, with values ranging from 0.25 to 1. However, an increase in the operating pressure forthe IGCC + CLC system increases the thermal efficiency of the process, and the CO₂ is recovered as a highpressure gas, decreasing the energy demand for further compression. The effect of pressure on the behavior ofthe oxygen carriers has been analyzed in a pressurized thermogravimetric analyzer at 1073 K and pressures upto 30 atm. It has been found that an increase in total pressure has a negative effect on the reaction rates of allthe oxygen carriers. Moreover, the use of the CGSM with the kinetic parameters obtained at atmosphericpressure predicted higher reaction rates than those experimentally obtained at higher pressures, and therefore,the kinetic parameters necessary to design pressurized CLC plants must be determined at the operating pressure.