Fe2O3/ATP载氧体制备及煤化学链燃烧性能研究

Preparation and performance of the Fe2O3/ATP oxygen carriers in coal chemical looping combustion

  • 摘要: 以天然凹凸棒(ATP)为载体,分别利用机械混合法、浸渍法和溶胶-凝胶法制备了3种铁基复合载氧体。利用X射线衍射(XRD)、能谱(EDS)、N2-吸附脱附等温线等对其进行物化表征,并在900 ℃流化床中考察其煤化学链燃烧反应性能。结果表明,ATP能显著增加载氧体比表面积和抗磨损能力,并对煤转化过程有催化作用,其与Fe2O3的协同作用使初始碳转化速率显著提高。溶胶-凝胶法制备的U-Fe4ATP6表面Ca元素含量为4.3%,比表面积为4.920 7 m2/g,均高于其他两种载氧体,表现出更高的催化性能和反应活性:初始碳转化速率为0.168 min-1,平均CO2浓度为98.6%,燃烧效率为98.7%。20次反应后,U-Fe4ATP6催化性能略有降低,对应的初始碳转化速率降至0.108 min-1,停留时间t95延长到18 min;且能维持较高的反应活性,对应的CO2捕集效率和燃烧效率分别稳定在98.6%和96.7%。

     

    Abstract: Through mechanical-mixing, impregnating and sol-gel methods, Fe2O3-based oxygen carriers (OC) were prepared with natural attapulgite (ATP) as an inert support and characterized by X-ray diffraction (XRD), energy dispersive spectrometer (EDS), and nitrogen adsorption-desorption measurements. The reactivity of Fe2O3-based oxygen carriers (Fe2O3/ATP OCs) in coal chemical looping combustion (CLC) was investigated in a fluidized-bed reactor at 900 ℃ by using steam as the gasification agent. The results indicated that the surface area and attrition resistance of Fe2O3/ATP OCs are improved significantly by using ATP as the support. Owing the synergy between ATP and Fe2O3, both are catalytic active, carbon conversion is enhanced significantly. ATP is an appropriate support for Fe2O3 oxygen carriers, whereas the sol-gel method gives the carriers best performance. U-Fe4ATP6 prepared by the sol-gel method, with a surface area of 4.920 7 m2/g and Ca content of 4.3%, exhibits much better performance than other two oxygen carriers. When used in CLC, the initial carbon conversion rate reaches 0.168 min-1, with an average CO2 concentration of 98.6% and a combustion efficiency of 98.7%. The catalytic activity of U-Fe4ATP6 is slightly decreased after twenty cycles; the initial carbon conversion rate is decreased to 0.108 min-1 and the residence time (t95) is extended to 18 min, whereas the CO2 capture efficiency and combustion efficiency remain at about 98.6% and 96.7%, respectively.

     

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