相律的应用:蒸发结晶过程自由度

Application Of Phase Rule: The Degree of Freedom of Evaporation—Crystallization

在连续原理和浓度限制条件的基础上,分析了卤水蒸发过程的自由度,提出了“蒸发结晶过程自由度”这一概念。发现蒸发结晶过程自由度在整个过程中不是1便是0,在1和0之间交替变化,与选择的组分数和析出固相数目无关。蒸发结晶过程自由度为1,物理意义是在不引起新相产生旧相不消失的前提下过程连续地变化(水分的连续蒸失),几何意义是指在适当的坐标系中的一条线,一条直线或曲线;0的物理意义是指新相的产生和旧相的即将消失或者前一段的连续变化过渡到后一段的连续变化,几何意义是指一点,两蒸发阶段的交点或者过程的终点。简单地讨论了过程的单向性和连续件。

Based on the continuous principle and the concentration restrictions, the degree of freedom of evaporation process of brine has been analyzed. A new concept'freedom degree of evaporation-crystallization' was proposed in this paper. After the beginning of the evaporation process at constant temperature and pressure and in equilibrium state, the degree of freedom of evaporation-crystallizition is given either 1or 0, and has nothing to do with the number of the chosen components and precipitated phases. The f_(evp) in the whole process changes alternately between 0 and 1. The physical significance of f_(evp)=1 means that the process may be continuously changed without causing the appearance of any new phase and the disappearance of any old phase. Its geometric meaning signifies that the evaporation path is only a line, either straight line or curve. The physical significance of f_(evp)=0 implies that the evaporation path is at a point, the crossing point between two stages or the end point of the evaporation path. The properties of the continuity and monodirection in the evaporation process were briefly discussed.