Oxygen Release and Oxidation Rates of MgAl2O4-Supported CuO Oxygen Carrier for Chemical-Looping Combustion with Oxygen Uncoupling (CLOU)
Oxygen Release and Oxidation Rates of MgAl2O4-Supported CuO Oxygen Carrier for Chemical-Looping Combustion with Oxygen Uncoupling (CLOU)
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DOI：
10.1021/ef3010064
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发表时间：
2012-11-01
期刊：
影响因子：
5.3
通讯作者：
Lyngfelt, Anders
中科院分区：
文献类型：
--
作者：
Arjmand, Mehdi;Keller, Martin;Lyngfelt, Anders
化学环燃烧（CLC）和化学环氧解偶联（CLOU）工艺是实现二氧化碳固有分离高效燃烧的新方法。这些过程使用金属氧化物作为氧载体，将氧气从空气反应堆转移到燃料反应堆，燃料在那里与固体氧载体发生反应。当在CLC中使用固体燃料时，焦炭必须被（例如蒸汽）气化以形成H-2和CO，这些H-2和CO随后可以被氧载体氧化成H2O和CO2。在CLOU的情况下，氧载体在燃料反应堆中释放氧气。这使得固体燃料的焦炭转化率很高，因为它消除了使用固体燃料的普通CLC所需的气化步骤。在这项工作中，氧气释放和氧化的速率。研究了以MgAl2O4 （40/60 wt %）负载CuO为氧载体的CLOU工艺。采用冷冻造粒法制备氧载体，在950℃下煅烧，筛分至125 ~ 180 μ m，在实验室规模的流化床反应器中，在850 ~ 900℃的温度范围内，在还原性和氧化性交替条件下获得反应速率。以脱挥发木炭为燃料，测定了N-2流化过程中氧的释放速率。在燃料与载体释放的氧气燃烧过程中，在床上获得可靠的测量结果，不受燃料可用性和温度升高的影响。用Avrami-Erofeev机制模拟氧释放速率，估计k(o)和E-app的值分别为2.5 × 10(5) s（-1）和1393 kJ mol（-1）。研究了反应器入口流量为5% O-2时氧化Cu2O的速率。然而，观察到氧化速率受到氧气供应的限制，表明氧载体的快速转化。根据获得的反应速率，所研究的氧载体在空气和燃料反应堆中所需的最小总量估计在69-139 kg MWth-1之间。
The chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) processes are novel solutions for efficient combustion with inherent separation of carbon dioxide. These processes use a metal oxide as an oxygen carrier to transfer oxygen from an air reactor to a fuel reactor, where the fuel reacts with the solid oxygen carrier. When solid fuel is used in CLC, the char must be gasified by, e.g., steam to form H-2 and CO, that can be subsequently oxidized to H2O and CO2 by the oxygen carrier. In the case of CLOU, the oxygen carrier releases oxygen gas in the fuel reactor. This enables a high rate of conversion of char from solid fuels, because it eliminates the need for the gasification step needed in normal CLC with Solid fuels. In this work, the rate of oxygen release and oxidation. of an oxygen carrier consisting of CuO supported by MgAl2O4 (40/60 wt %) for the CLOU process is investigated. The oxygen :carrier was produced by freeze granulation, calcined at 950 degrees C, and sieved to a size range of 125-180 mu m. The reaction rates Were obtained in a laboratory-scale fluidized bed reactor in the temperature range of 850-900 degrees C, under alternating reducing and oxidizing conditions. The rate of oxygen release was obtained using devolatilized wood char as the fuel in N-2 fluidization. Care was taken to Obtain reliable measurements not affected by the availability of the fuel and temperature increase :in the bed during combustion of the fuel with the released oxygen from the carrier. The Avrami-Erofeev mechanism was used to model the rates of oxygen release and the values of k(o) and E-app were estimated to be 2.5 x 10(5) s(-1) and 1393 kJ mol(-1), respectively. The rates of Cu2O oxidation were investigated in a flow of 5% O-2 at the inlet of the reactor. However, it was observed that the oxidation rate is limited by the oxygen supply, indicating rapid conversion of the oxygen carrier. From the obtained reaction rates, the minimum total amount of the investigated oxygen carrier needed in the air and the fuel reactor is estimated to be between 69-139 kg MWth-1.