煤基化学链燃烧技术的Fe2O3/Al2O3氧载体研究

Fe2O3/Al2O3 OXYGEN CARRIERS FOR CHEMICAL LOOPING COMBUSTION FUELED BY COAL CHAR

直接以煤为燃料的化学链燃烧是解决中国燃煤CO2排放的一种潜在技术，关键问题之一是难以气化和氧化的煤焦与氧载体之间的固固还原反应。本文基于溶胶一凝胶法，利用Al（OC3H7）3和Fe（NO3）3·9H2O制备了12种不同的氧载体，并用XRD、SEM、BET等对其物化性质进行了表征，发现烧结温度以低于1200℃为宜。选择6种不同参数（活性R203质量含量、烧结温度和烧结时间）的Fe2O3／Al2O3氧载体，在热重中研究了它们与煤焦的反应性能，结果表明，在880℃左右时，氧载体与煤焦快速反应，首先快速还原成Fe3O4，然后有一部分FeO出现。综合各方面因素，选用F6A1116氧载体（60％Fe2O3含量，1100℃烧结6h）进行与煤焦／空气的多次循环实验。结果表明，氧载体没有杂质物相生成，表现了良好的循环反应性。反应后氧载体表面发生了一定程度的烧结现象，但仍维持孔隙结构。这些实验结果初步证明，基于Fe2O3／Al2O3氧载体、燃用固体燃料煤焦的化学链燃烧技术是可行的。

Chemical looping combustion （CLC） fueled by coal is a potential technology to solve the CO2 emission from coal combustion in China, one of the key points of which is the solid-solid reduction between oxygen carriers and coal char （it is difficult to gasify and oxidize）. Based on the sol-gel method, Al（OC3H7）3 and Fe（NO3）3.9H2O are selected as main raw materials to prepare 12 kinds of oxygen carriers in this paper. X-ray diffraction （XRD）, N2 adsorption-desorption （BET） method and scanning electron microscope （SEM） are utilized to characterize the physicochemical properties of oxygen carriers. The results show that the sintering temperature is better below 1200℃. Six kinds of oxygen carriers which are different in mass contents of active Fe2O3, sintering temperature and sintering time are selected to react with char in a thermo-gravimetric analysis （TGA） in order to research their reactivity. The experimental results show that Fe2O3/Al2O3 oxygen carriers start to rapidly react with coal char at the temperature 880℃, as when Fe2O3 is first rapidly reduced to Fe304, and then slowly reduced to FeO. Oxygen carrier with contents of 60% Fe2O3, sintering temperature of 1100℃ and sintering time of 6 hours is selected to circularly react with char/air. There are no other phases after several circle reduction-oxidation reactions, which shows extremely good circular reactivity. The sintering behavior is observed on the surface of the particles, but the porous beehive structure of particles is still maintained. These experimental results show promise in the development of the chemical looping combustion of coal, based on Fe2O3/Al2O3 oxygen carriers.