基于草木灰修饰Fe基载氧体的化学链燃烧实验

Experimental investigation of chemical looping combustion of Fe-based oxygen carrier modified by plant ash

采用草木灰对Fe基载氧体进行修饰,并在流化床反应器上进行了气体燃料化学链燃烧实验。研究了草木灰修饰对提高Fe基载氧体还原活性的可行性,讨论了草木灰种类、草木灰的无机组分对载氧体活性的影响。结果表明,草木灰修饰能有效提高Fe载氧体的反应活性,载氧体的还原反应活性由草木灰中K和Si的含量共同决定。随着修饰草木灰中的K含量提高,载氧体的活性逐渐提高;但在Fe3O4/FeO的转化阶段,同时存在碱金属K对还原反应的催化作用和低熔点碱金属硅酸盐对还原反应的抑制作用。循环实验表明,草木灰中碱金属K对载氧体活性的提高效果始终明显,载氧体中负载的K在循环过程中出现了流失现象,而生成的碱金属硅酸盐类化合物,可抑制碱金属K的流失。

Chemical looping combustion of gaseous fuel was performed in a fluidized bed reactor with Fe-based oxygen carrier modified with plant ash. The feasibility of the enhanced reduction performance of Fe-based oxygen carrier modified by plant ash was investigated, and the effects of ash type and chemical composition of the ash were discussed. The results indicate that the addition of plant ash into Fe-based oxygen carrier can efficiently enhance the reduction reactivity of the Fe-based oxygen carrier, depending on the content of K and Si in ash. The elevated K content in the ash enhanced reactivity during the whole reduction stage, including Fez O3/Fe3O4 and Fe3O4/FeO. However, the suppression effect of alkali metal silicates with a low melt point on the oxygen carrier reduction was also observed in the stage of Fe3O4/FeO. The 10-cycle redox experiments indicate that the modified Fe-based oxygen carrier maintains the enhanced reactivity although there exists a reactivity decrease. There was a loss of K in the modified Fe-based oxygen carrier during the cycle, but the alkali metal silicates can reduce the loss of K.