Abstract:

The ash fusion temperature of coal at high temperature is an important parameter for the efficient and safe operation of coal gasifiers. The equipment of ash fusion temperature was used to measure the ash fusion temperatures of the oxide components composed of SiO₂, Al₂O₃, Fe₂O₃, MgO, and CaO with different proportions. Five variables composed of Si/Al, Si+Al, Fe₂O_3, MgO, and CaO were selected to verify the effect of the change on the coal ash fusing characteristics and the range of variables cover most domestic coal ash. Factsage was used to calculate the liquidus temperature of coal ash components, and to obtain the solid phase ratios of each crystal in each slag system and the simulation results are verified by experiments. With the contents of CaO, Fe₂O₃ and Si/Al increase, the ash fusion temperature gradually decreases while with the content increasing of Si+Al and MgO, the ash fusion temperature of the coal ash gradually increases. The ash fusion temperature varied with the contents of the oxide components and was closely related to the corresponding liquidus temperature, which was always higher than the ash fusion temperature about 200℃. Factsage was also used to predict the crystal compositions of the slag system at different temperatures. It could be concluded that there was no necessary relationship between the transformation of different slag systems with the change of a certain variable, and further analysis was needed for the slag system dominated by a specific factor. In the crystal phase experiment, after the slag was fused, quenching could be performed quickly to maintain the original crystal form at the high temperature. When X-ray diffraction analysis was completed, the precipitation ratios of different crystals at various temperatures could be obtained, which was in good agreement with the simulation results. The differences between the simulation and experimental results were also explored. The effects of different oxide compositions on the slag solidification ratios were investigated. The conclusion of this paper lays a foundation for further analysis of the product and characteristics of the molten state of multi-oxide system, and is of great significance for the optimization design operation of gasifier.

Key words: phase change, crystallization, coal combustion, numerical simulation, ash fusion temperature, Factsage

摘要：

煤在高温下的灰熔点是气化炉安全高效运行的重要参数，利用灰熔点仪对由SiO₂，Al₂O₃，Fe₂O₃，MgO，CaO按不同比例组成的氧化物组分进行灰熔点测定，选取Si/Al、Si+Al、Fe₂O₃、MgO、CaO五个关键变量以验证其变化对煤灰熔融特性的影响，变量变化范围涵盖国内大部分煤灰的范围。采用Factsage软件预测了煤灰组分的全液相温度并与灰熔点进行比较。结果表明，随着CaO、Fe₂O₃、Si/Al含量的增加，煤灰的灰熔点逐渐降低；随着MgO、Si+Al含量的增加，煤灰的灰熔点逐渐升高，由Factsage计算出的全液相温度总是高于灰熔点200℃左右。利用Factsage获得各个渣系随温度变化析出晶体的固相比例，并对模拟结果进行了实验验证，探究了两者产生差异的原因及不同氧化物组成对各个渣系固相比例所产生的影响。结论为进一步分析多元氧化物体系熔融状态产物及特点奠定了基础，并对气化炉优化设计运行具有重要意义。

关键词: 相变, 结晶, 煤燃烧, 数值模拟, 灰熔点, Factsage