Abstract:

Using ash melting point apparatus, XRD and thermodynamic simulation, the influence mechanism of atmosphere and chemical composition on the melting characteristics of high-speed iron coal ash was studied. The results indicate that the fusion temperature of high-iron coal ash decreases with the increasing iron content, or calcium content, or S/A (the mass ratio of SiO₂ to Al₂O₃). Further, the fusion behavior of high calcium or high S/A and high-iron ash under mild reducing atmosphere (MR) follows the “melting-dissolution” mechanism due to the existence of the initial melting stage, while the fusion of low calcium or low S/A and high-iron ash under air belongs to the “softening-melting” mechanism. The iron accelerates the melting of quartz and anorthite under MR, and the calcium promotes the melting of quartz and corundum or transformations of these minerals to the calcium-based aluminosilicates. Under MR, the liquid content increases with the iron content or S/A, and the liquid viscosity decreases with the increasing calcium content or iron content, improving the mass transfer. In contrast, the crystallization of iron-containing solid solutions which were found in the low-calcium or low S/A and high iron ash leads to a higher liquid viscosity or lower liquid content under air, inhibiting the mass transfer of ash melting.

Key words: coal ash, gasification, fusion characteristic, crystallization, phase change, chemical composition, atmosphere

摘要：

采用灰熔点仪、XRD和热力学模拟，研究气氛和化学组成对高铁煤灰熔融特性的影响机理。研究结果表明，灰熔融温度随铁含量、钙含量或硅铝比增加而降低。弱还原气氛下低钙或低硅铝比煤灰熔融存在明显的初始熔融阶段，熔融过程遵循“软化-熔融”机理，而空气气氛下高钙或高硅铝比煤灰熔融过程属于“熔融-溶解”机理。弱还原气氛下铁含量增加显著促进石英和钙长石熔融，空气气氛下钙含量增加促进刚玉和石英熔融或转化为钙基硅铝盐。弱还原气氛下液相含量随硅铝比或铁含量增加而增加，液相黏度随钙含量或铁含量增加而降低，促进熔融传质；空气气氛下低钙或低硅铝比煤灰中铁存在于含铁固溶体，导致液相黏度高或液相含量低，熔融传质受阻。

关键词: 煤灰, 气化, 熔融特性, 结晶, 相变, 化学组成, 气氛