铁是普遍存在于煤中的重要元素,其含量和价态等参数是影响煤气化灰渣理化特性(矿物转化和熔融、结晶、黏温和流变性等)的关键因素。气化炉用煤的种类和操作工况(气氛和温度)等变化影响铁的赋存形态,含铁的煤气化灰渣呈不同理化性质,其研究对指导气化炉的顺畅排渣具有重要意义。综述了近年来学者对铁元素在气化灰渣的赋存形态、铁对煤气化灰渣的熔融特性、降温过程结晶性和黏温特性等研究进展。铁主要以FeO、Fe2O3、FeS和FeS2等形式存在于原煤中,在煤气化过程中转化为含铁的硅铝酸盐类物质,且受气体组分(CO/CO2/O2/H2)、化学组成和温度影响显著。因Fe3+具有强极性,难以与其他矿物反应,在氧化性气氛下的灰渣熔融温度较高;而CO、H2等气体具有较强的还原性,灰渣中的Fe2O3被还原为亚铁(Fe2+),其熔融温度降低,但还原为金属Fe时,其具有高熔点特性,灰熔融温度升高。煤气化灰渣中铁元素对熔融液态渣在冷却降温过程的结晶性能产生影响,包括含Fe的晶体种类、结晶温度、析晶条件、晶体形貌和尺寸等。其中,Fe与Ca在硅铝酸盐网状结构中的作用受气氛、温度和化学组成影响显著,主要为Fe/Fe2+/Fe3+三者的转化与钙长石类矿物的相互作用,影响含铁晶体转化和铁单质析出。阐明了煤气化灰渣中铁元素对其黏温特性的影响机制,包括黏度和临界黏度温度,铁的不同价态和含量是黏度变化和熔体结构转变过程的重要参数。最后,总结了铁元素对煤气化灰渣理化性质的作用,展望复杂气氛下(H2/CO/CO2)铁单质、离子态(Fe2+/Fe3+)等对煤气化过程矿物转化、灰渣熔融和结晶等物理和化学综合作用是明晰煤气化灰渣中铁元素作用的关键,需建立合适的含铁煤气化灰渣性质预测体系,为工业气化炉运行提供指导。

Iron is an important element commonly found in coal minerals, and its occurrence parameters such as content and valence arethe key factors affecting the physical and chemical properties of coal gasification ash, such as mineral transformation, melting, crystalliza⁃tion, viscosity, rheology, etc. The type of coal used in gasifier and the change of operating conditions (atmosphere and temperature) af⁃fect the occurrence form of Fe, and the coal gasification ash containing iron shows different physical and chemical properties, which isof great significance to guide the smooth slagging of gasifier. Research progress on the occurrence form of iron in gasification ash, meltingproperties of Fe on coal gasification ash, crystallinity and viscosity-temperature properties during cooling process were reviewed. Fe mainlyexists in raw coal in the form of FeO, Fe2O3, FeS, and FeS2, and is converted into iron-containing aluminosilicates during coal gasifica⁃tion, which is significantly affected by gas compositions (CO/ CO2 / O2 / H2), chemical compositions and temperature. Due to Fe3+ has astrong polarity, it is difficult to react with other minerals, and the melting temperature of ash slag in oxidizing atmosphere is higher. WhileCO, H2 and other reducing gases have strong reducibility, Fe2O3 in ash slag is reduced to ferrous (Fe2+), its melting temperature is re⁃duced, but reduced to metallic iron (Fe), it has a high melting point characteristic, ash melting temperature increases. The effects of Fein coal gasification ash on the crystallization properties of molten liquid slag during the cooling process include the types of Fe-contai⁃ning crystals, crystallization temperature, crystallization conditions, crystal morphology and scale. Among them, the interaction of Fe andCa in aluminosilicate network structure is significantly affected by atmosphere, temperature and chemical composition. The main effect isthe interaction between the transformation of Fe/ Fe2+ / Fe3+ and calcium feldspar minerals, which affects the transformation of iron-contai⁃ning crystals and the precipitation of iron. The effect of Fe on the viscosity - temperature and viscosity - temperature characteristicsof coal gasification slag was discussed, including the variation of viscosity and the critical viscosity temperature, the different valencestates and contents of Fe were important parameters in the process of viscosity change and melt structure transformation. Finally, the effectof Fe on the physical and chemical properties of coal gasification ash was summarized. It is expected that the combined physical and chem⁃ical effects of iron elemental and ionic state ( Fe2+ / Fe3+ ) in complex atmosphere ( H2 / CO/ CO2 ) on mineral conversion, ash meltingand crystallization are the key to clarify the role of iron in coal gasification ash. It is necessary to establish a suitable prediction system forthe properties of iron coal gasification ash and slag to provide guidance for the operation of industrial gasifier.

0 引言

1 煤灰渣中铁元素的赋存形态

   1.1 含铁矿物种类

   1.2 含铁矿物转化

   1.3 铁元素迁移

   1.4 不同气氛下的铁元素赋存形态

2 铁对煤灰熔融性的影响

   2.1 气体组分影响

   2.2 铁价态对灰渣熔融温度影响

   2.3 含铁助熔剂的作用

   2.4 其他元素与铁作用

   2.5 含铁灰渣结渣性

3 铁对高温熔体降温过程结晶的影响

   3.1 铁元素及含铁化合物对结晶的影响

   3.2 其他物质对含铁晶体析出影响

4 铁对灰渣黏温特性的影响

   4.1 铁及铁氧化物的影响

   4.2 含铁添加剂的影响

5 结语与展望