| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 99 === Chemical looping process (CLP) was a promising energy technology with high efficiency and low greenhouse gas emission, and a successful operation of CLP strongly depended on the effective reactivity of an oxygen carrier. The fabrication of Fe2O3/Al2O3 composite oxygen carrier was tested by thermogravimetic analysis (TGA) with better reactivity and recyclability than Fe2O3 pellet, and the effect of preparation parameters such as ratio of Fe2O3/Al2O3, sintering temperature, pelletizing pressure and starch content were discussed. The weights of Fe2O3/Al2O3 composite oxygen carrier were 200 mg, and the reaction temperatures were 900°C. Three gas flows included syngas, air, and N2 as reducing, oxidizing and purge gases, and syngas was used to simulate the product of coal gasification. The addition of inert support could restrain the surface agglomeration and increase the reactivity of oxygen carrier, and Fe2O3/Al2O3 composite oxygen carrier composed of 40% Al2O3 showed highest reactivity. Fe2O3/Al2O3 composite oxygen carrier sintered at 1300°C would contain a crystal phase of FeAl2O4, and it would contribute to present a better reactivity. After the pelletizing process, with increasing the starch content, the Fe2O3/Al2O3 composite oxygen carrier would keep the preferable recyclability with the presence of fine pore structures. However, the pelletizing pressure was not significant for the reactivity of Fe2O3/Al2O3 composite oxygen carrier. TGA, XRD, FESEM, Archimedes’ balance, and pressure sensor were employed to examine the characterization of Fe2O3/Al2O3 composite oxygen carrier.
Charcoal directed combustion with oxygen carrier has been proved as the most efficient way among all types of the fuels. The prepared Fe2O3/Al2O3 composite oxygen carrier was firstly tested by TGA with better reactivity and recyclability than Fe2O3 pellet. The weights of Fe2O3/Al2O3 composite oxygen carrier and charcoal were 1 and 10 g, respectively, loaded in the fixed bed reactor (FBR). The reaction temperatures were 700, 800 and 900°C at CO2/steam atmosphere. CO2/steam gas with 100 mL/min of flowrate was introduced into the FBR to enhance the reaction rate because CO2/steam gas would react with charcoal to produce CO/H¬2 synthesis gas that induced the chain reaction between charcoal and oxygen carrier. At 900°C, Fe2O3/Al2O3 composite oxygen carrier would completely convert to the reduced metal oxide during 20 minutes, and the reduction rates at 700 and 800°C were much slower. Hence, the higher reaction temperature could enhance the reactivity of oxygen carrier. Besides, the prepared Fe2O3/Al2O3 composite oxygen carrier was feasible applying to solid fuel directly combustion in FBR. The results would be taken into account on design of solid fuel chemical looping reactor subsequently.
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