Chemical-looping gasification reaction characteristics and mechanism of coal and Fe-based composite oxygen carriers

doi:10.3969/j.issn.0438-1157.2013.07.038

Abstract

Abstract: An investigation into chemical-looping gasification (CLG)of coal with K₂CO₃ and NiO-decorated Fe₂O₃ oxygen carrier in a fluidized bed reactor,using steam as the gasification-fluidization medium,was carried out.The reactivity and regeneration of two kinds of Fe₂O₃ composite oxygen carriers in multi-cycles,as well as the mechanism and kinetics model of the gasification process,were presented.At 920℃,the reactivity order was as follow:Fe4Al6K1>Fe4Al6>Fe4Al6Ni1.X-ray diffraction (XRD)images showed that the Fe4Al6K1 composite oxygen carrier was completely regenerated after 6 cycle redox experiments,and potassium ferrites were formed during the calcinations process,whose structure could boost the reactivity of Fe-based oxygen carrier.Fe4Al6K1 particles were excellent oxygen carriers for chemical-looping gasification of coal.Finally,the peak fitting technique was used to analyze the gasification reaction rate curve describing the reaction mechanism of coal and Fe₂O₃ composite oxygen carrier.It indicated that complex reactions of CLG included three stages,the reaction between Fe₂O₃,coal char and steam,the gasification of coal char,and the reaction of Fe₃O₄ to FeO.

Key words: chemical-looping gasification, fluidized bed reactor, Fe-based composite oxygen carriers, kinetic model

摘要： 以水蒸气作为气化/流化介质,在流化床中研究了两种铁基复合载氧体的化学链气化反应特性及循环特性,并对气化过程中的反应机理、动力学方程进行了推断。结果表明:温度为920℃时,添加不同修饰物的铁基复合载氧体与煤焦气化的反应活性依次为Fe4Al6K1>Fe4Al6>Fe4Al6Ni1。在多次循环实验过程中,合成气成分保持稳定,表明Fe4Al6K1复合载氧体循环特性良好。XRD谱图分析表明,六次氧化还原实验后的铁基载氧体氧化态仍为Fe₂O₃。K⁺主要以铁酸钾形态存在,该结构有利于促进化学链气化反应。利用高斯函数对气化反应速率进行了峰拟合,拟合结果表明化学链气化主要分为3个阶段:化学链作用阶段、煤气化阶段以及Fe₃O₄向FeO转变的气化阶段。

关键词: 化学链气化, 流化床反应器, 铁基复合载氧体, 动力学模型

CLC Number:

CHENG Yu, LIU Yongzhuo, TIAN Hongjing, GUO Qingjie. Chemical-looping gasification reaction characteristics and mechanism of coal and Fe-based composite oxygen carriers[J]. CIESC Journal, 2013, 64(7): 2587-2595.

程煜, 刘永卓, 田红景, 郭庆杰. 铁基复合载氧体煤化学链气化反应特性及机理[J]. 化工学报, 2013, 64(7): 2587-2595.

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