The effect of iron-bearing mineral melting behavior on ash deposition during coal combustion
The effect of iron-bearing mineral melting behavior on ash deposition during coal combustion
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DOI：
10.1016/j.proci.2010.07.061
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
Zhong-xiao Zhang;Xiaojiang Wu;T. Zhou;Yushuang Chen;Ning Hou;Guilin Piao;Nobusuke Kobayashi;Y. Itaya;S. Mori
中科院分区：
文献类型：
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作者：
Zhong-xiao Zhang;Xiaojiang Wu;T. Zhou;Yushuang Chen;Ning Hou;Guilin Piao;Nobusuke Kobayashi;Y. Itaya;S. Mori
煤中的矿物是煤燃烧中产生结垢、结渣和腐蚀等问题的重要来源之一。矿物转化和矿渣形成是煤的特殊性质，为煤燃烧或气化的适宜性提供了更多的信息。采用加热显微镜、x射线衍射仪（XRD）、扫描电镜（SEM）结合EDX （SEM-EDX）技术，研究了中国煤粉（PC）灰分在不同气氛下的烧结行为，特别是含铁矿物的烧结转变机理。此外，利用量子化学理论计算了含铁矿物铁矾石（2FeO·SiO2）的分子化学特征，从分子水平上详细了解矿物反应机理。结果表明：不同条件下煤灰烧结性能不同的主要原因是铁（Fe2+或Fe3+）的不同状态。灰分中的含铁矿物浮氏体（FeO）、铝锰矿（3FeO·Al2O3·3SiO2）和铁矾石等是影响煤燃烧过程中1273 ~ 1373K还原条件下灰分初始烧结行为的最重要因素。在费亚尔石分子团簇中，由于最高占据分子轨道（HOMO）和最低占据分子轨道（LUMO）主要由铁原子构成，且费亚尔石分子团簇中HOMO和LUMO的最小能量差（1.659eV）远低于莫来石（3Al2O3·2SiO2·h2o, 6.8eV）和高岭石（Al2O3·2SiO2·2H2O, 3.49eV），因此费亚尔石的热稳定性相对较低，铁原子（尤其是Fe(6)），铁(8)和铁(3)在铁铝石分子簇中具有相对较高的反应活性。这就是为什么在灰分烧结过程中，铁矾石在相对较低的温度下开始熔化的原因。
Mineral matter in coal is one of the most important sources of problems in coal combustion, including fouling, slagging and corrosion, etc. Mineral matter transformation and slag formation are specific properties of coal that provide more information on the suitability for coal combustion or gasification. In this research, the sintering behavior of Chinese pulverized coal (PC) ash as well as mineral transition mechanism under various atmospheres, especially iron-bearing minerals, was studied by heating microscopy, X-ray diffraction (XRD), Scanning Electron Microscope (SEM) combined with EDX (SEM-EDX). Furthermore, the molecular chemical characteristics of iron-bearing minerals, fayalite (2FeO·SiO2), were also calculated using quantum chemistry theory to provide an insight into the mineral reaction mechanism at molecular level in detail. The results showed that the different states of iron (Fe2+or Fe3+) are the dominant reasons for different sintering behaviors of coal ash under different conditions. The iron-bearing minerals in ash, such as wustite (FeO), almandite (3FeO·Al2O3·3SiO2) and fayalite, etc., are the most important factors influencing the initial sintering behavior of coal ash in the temperature range from 1273 to 1373K under reducing condition during coal combustion. In fayalite molecular cluster, it is because that the highest occupied molecular orbital (HOMO) and the lowest occupied molecular orbital (LUMO) are mostly constituted by Fe atoms and the minimum energy difference between HOMO and LUMO in fayalite cluster (1.659eV) is much lower than that of mullite (3Al2O3·2SiO2, 6.8eV) and kaolinite (Al2O3·2SiO2·2H2O, 3.49eV), the thermal stability of fayalite is relatively low and Fe atoms (especially Fe(6), Fe(8) and Fe(3)) have relatively higher reactivity than any other atoms in fayalite molecular cluster. That is the reason why fayalite starts to melt at relatively low temperature during ash sintering behavior.