气化技术是煤化工的龙头技术,气流床气化炉具有燃料适用广、转化率高等优势,是大型煤气化的发展方向。由于原料组分或操作条件变化,反应后的灰熔渣在流动过程中会因晶体析出呈现非牛顿流体特性,造成排渣不畅,因此掌握炉内熔渣析晶行为对控制熔渣的流变特性及设备稳定运行有重要指导意义。论述了非牛顿熔渣析晶行为研究,分析了灰渣中结晶行为的影响因素。不同过冷度带来的晶体生长驱动力不同,从而影响晶体生长速率。增大冷却速率会导致晶体孕育时间不足,晶体生长较小。冷却速率超过熔渣的临界冷却速率时,熔渣呈现玻璃体状态。熔渣中主要成分变化导致熔渣的扩散特性及晶体类型改变,熔体碱性组分增加会促进熔渣结晶。此外,不同晶体种类,晶体大小和形状、固液界面析晶反应、晶体生长速率等均发生变化,从而引起流变特性变化。因此,总结了熔渣中几种常见晶体(钙长石、黄长石和尖晶石)的生长特性,以及晶体对熔渣流变特性的影响。对于非牛顿气化渣,晶体析出种类及对应的晶体生长特性仍不明确,有待进一步研究。通过晶体生长预测和控制来调节熔渣流变行为,将实现炉内液态渣层沿程流动的黏度变化预测,对于优化工程中液态排渣炉内熔渣流动有重要指导意义。

Gasification technology is the leading technology of the coal chemical industry, and the airflow bed gasifier is the direction oflarge-scale gasification due to the flexible fuel application and high conversion rate. As the raw material components or operating condi⁃tions change, the slag may exhibit non-Newtonian fluid properties due to crystal precipitation during the flow process, resulting in poorslag discharge. Therefore, the crystal precipitation behavior of the slag in the furnace has important guiding significance for controlling therheological properties of the slag and the stable operation of the equipment. Research on the crystallization behavior of non-Newtonianslags was summarized, the influencing factors of the main components and cooling conditions were analyzed. The driving force of crys⁃tal growth varies with different undercooling degrees, thereby affecting the crystal growth rate. Increasing the cooling rate leads to insuffi⁃cient crystal incubation time and thus small crystals. When the cooling rate exceeds the critical cooling rate, the slag takes on a vitreousstate. The changes in the main components of the slag lead to changes of the diffusion properties as well as the crystal types. An increase inthe alkalinity of the melt leads to an increased crystallization capacity of the slag. In addition, different crystal types, the size and shape ofthe crystals, the crystallization reaction at the solid-liquid interface, and the crystal growth rate, etc. all undergo changes, resultingin changes in rheological properties. Therefore, the growth characteristics of several common crystals in slag (Anorthite, Melilite and Spi⁃nel) were summarized, as well as the influence of the crystals on the rheological properties of the slag. For non-Newtonian slags, the crys⁃tal precipitation types and corresponding crystal characteristics are still unclear and need to be further studied. Adjusting the rheologicalbehavior of slag by forecasting and controlling the crystal growth will realize the prediction of the viscosity change of the liquid slag layer,which is significant for optimizing the flow of slag discharge furnace.

0 引言

1 结晶研究方法

   1.1 差示扫描量热法

   1.2 X射线衍射法

   1.3 扫描电子显微镜（SEM-EDS）

   1.4 热电偶技术（HTT）

   1.5 高温共焦激光扫描显微镜法（CSLM）

   1.6 Factsage热力学计算

2 结晶的影响因素

   2.1 组分对结晶的影响

   2.2 冷却条件对结晶的影响

3 常见气化熔渣晶体的生长特性

   3.1 钙长石的结晶特性

   3.2 黄长石的结晶特性

   3.3 尖晶石的结晶特性

4 晶体对熔渣流变特性的影响

   4.1 晶体比例

   4.2 颗粒形状

   4.3 晶体尺寸

   4.4 剪切速率

5 结语及展望