Abstract:

A high-temperature hot-stage microscope was used to study the crystal growth rule and morphological characteristics of the crystallization process of non-Newtonian coal ash slag, and obtain parameters such as the type transformation and the aspect ratio change of the cinder crystals with different chemical compositions. Based on the crystal growth rule from the experiment, the viscosity model of the suspension was modified coupled with the crystal morphology, aspect ratio and the relationship between the slag solid phase and temperature. A viscosity-temperature prediction model suitable for non-Newtonian slag was established in this study, which was compared and verified with the measured viscosity-temperature curve. The model considered the single-phase and multiphase crystal morphology features of feldspar, melilite, anorthite, and merwinite, etc., mainly precipitated as monoclinic or triclinic crystal systems. The model was also modified by combining the parameters of solid fraction of coal slag (range 0≤? ≤0.8) and aspect ratio (1.0—16.0). The results showed that the model was limited as listed conditions, including acidity/basicity ratio of coal slags with ranged of 0.5—3.0, the total content of silicon and aluminum oxides from 35% to 70%(mass), the CaO content lower than 30%(mass), MgO content from 0 to 10%(mass), and the Fe₂O₃ content lower than 16%(mass).

Key words: gasification, coal ash/slag, crystallization, viscosity, model

摘要：

采用高温热台显微镜研究了非牛顿煤灰渣结晶过程的晶体生长规律及形貌特征，获得不同化学组成煤渣晶体的种类转变和长宽比变化等参数。基于实验获得的晶体生长规律，耦合晶体形貌、长宽比及熔渣固相随温度的变化关系式，修正悬浮液的黏度模型，建立了适用于非牛顿熔渣的黏温预测模型，并与实测黏温曲线对比和验证。该模型考虑了主要析出以单斜晶系或三斜晶系特征的长石类、黄长石、钙长石和镁硅钙石等单相和多相晶体形貌特征，并结合煤渣固相分数（范围0≤?≤0.8）和长宽比（1.0~16.0）等参数修正。结果发现，模型对于煤渣酸碱比范围为0.5~3.0，煤渣硅铝含量总和35%~70%（质量）范围，CaO含量低于30%（质量）、MgO含量为0~10%（质量）以及Fe₂O₃含量范围低于16%（质量）的煤渣黏度预测适用性较好。

关键词: 气化, 煤灰渣, 结晶, 黏度, 模型