化学链燃烧中铁基载氧体研究进展

Research progress on Fe-based oxygen carrier in chemical looping combustion

化学链燃烧是我国应对气候变化的重要技术之一。载氧体作为氧和热的载体,是实现化学链燃烧的关键因素。近年来,寻找廉价载氧体成为研究者们关注的问题。铁基载氧体由于具有价廉、资源丰富、环境友好、机械性能好等优点受到了广泛关注,但其反应活性相对较差,如何提高其反应活性是其大规模应用的关键。笔者详细论述了化学链燃烧中铁基载氧体活性改进的研究进展,针对如何提高铁基载氧体的反应性能,从铁基载氧体制备方法的优化、组分掺杂、结构调控等3方面进行了阐述。指出,对于载氧体制备方法,应综合载氧体反应性能、制备周期和成本等因素,对其进一步选择或改进。对于载氧体组分,惰性载体的添加、制备成复合载氧体以及碱金属掺杂均可在一定程度上提高载氧体的反应性能,但采用单一措施均存在一定的问题,如活性组分与惰性载体的相互反应、复合载氧体的烧结以及碱金属的流失等,因而需要进一步研究各种因素间的相互作用。对于不同结构的载氧体,虽具有良好的结构稳定性或热稳定性,但也存在各自的缺点,如钙钛矿结构储氧能力较低,氧释放能力较低;在长时间的循环过程中,尖晶石结构的载氧体产生晶相分离和颗粒烧结而失活的现象;为了保持壳核结构的载氧体在循环过程中的稳定性及反应活性,对壳材料需要进一步选择及优化。基于目前研究现状,笔者指出铁基载氧体反应性能的进一步提高需综合考虑各方面因素并深入探究各因素之间的相互作用。

Chemical looping combustion is one of the most important technologies to deal with climate change in China.As the carrier of oxygen and heat,oxygen carrier is the key factor to realize chemical looping combustion.In recent years,how to develop cheap oxygen carriers has become a major concern.Due to its advantages of low cost,abundant resources,environmental friendliness and good mechanical properties,Fe-based oxygen carrier has attracted extensive attention,but its reactivity is relatively poor,and how to improve its reactivity is the key to its large-scale application.In this paper,the research progress on the improvement of the activity of Fe-based oxygen carrierin chemical looping combustion was reviewed.In order to improve the reactivity of Fe-based oxygen carrier,the optimization of preparation method,the doping of components and the structure regulation of Fe-based oxygen carrier were discussed.It is pointed out that the preparation method of oxygen carrier should be further improved by combing the factors such as the reaction performance,the preparation duration and cost of oxygen carrier.For the oxygen carrier components,the addition of the inert carrier,preparation of the composite oxygen carrier and alkali metal doping can improve the reactivity of the oxygen carrier to some extent.However,there are certain problems in the use of a single measure,such as the interaction of the active component with the inert carrier,the sintering of the composite oxygen carrier,and the loss of the alkali metal.Therefore,it is necessary to further study the interaction among various factors.For the oxygen carrier with different structures,it has good structural stability or thermal stability,but it also has its own disadvantages.For example,the oxygen carrier with perovskite structure has low oxygen storage capacity and oxygen release ability.The oxygen carrier with spinel structure may be deactivated by crystal phase separation and particle sintering during a long cycle.The oxygen carrier with core-shell structure,shell materials need to be further optimized so as to maintain its stability and reactivity in the cycle.Based on the current research status,it is pointed out that further improvement of the Fe-based oxygen carrier reactivity needs to comprehensively consider various factors and deeply explore the interaction between various factors.