Abstract:

The single hot thermocouple technique (SHTT) and image analysis program were applied to study synthetic slag's crystallization behaviors under different temperatures and cooling rates. In order to get crystallization mechanism, the crystallization kinetics parameters in isothermal process were calculated. Crystalline phases also were predicted by FactSage. In isothermal process, as temperature decreases, crystallization time decreases at first and increases later, and the crystals get smaller. At the same time, crystallization proportion increases at first, keeps stable later and decreases finally. There is saltation of crystallization proportion because of different crystalline phases at different temperature ranges. With increase of cooling rates, initial crystallization temperature declines and crystal turn from bulks to grains. Crystallization proportion remains unchanged, then decreases. Several stable areas of crystallization proportion appear owing to different crystalline phases under changing cooling rates. There is no crystal when cooling rate is large enough, and slag is totally solidified in glassy state. The heat curve of slag's crystallization measured by DSC fits well with the result of SHTT.

Key words: gasification, coal slag, crystallization, crystallization proportion, SHTT

摘要：

采用单热电偶在线观察系统（SHTT）、图像分析程序等研究等温过程中温度和连续冷却过程中冷却速率对于人工配制灰渣结晶行为的影响，通过计算结晶动力学参数分析其析晶机理，并采用FactSage软件预测晶体类型。实验结果表明，等温过程中，温度降低，结晶所需时间先减小后增大，晶体尺寸减小，结晶比例先增大再稳定最后减小，不同温度区间生成晶体类型不同，导致结晶比例在某些温度出现较大的变化。连续冷却过程中，冷却速率增大，初始结晶温度降低，晶体由块状向颗粒状转变，结晶比例先稳定后减小，由于析出的晶体类型不同，结晶比例出现多个稳定区间，达到临界冷却速率后熔渣全部凝固为玻璃态，无晶体析出。由DSC得到的熔渣结晶放热曲线与SHTT得到的结果吻合较好。

关键词: 煤气化, 灰渣, 结晶, 结晶比例, SHTT