脱硫废液中硫酸钙结晶的大小和晶习差异将直接导致其易积垢于热交换面且难以处理,结晶状况对生产工艺、设备配置和过程的经济性均会产生影响,因此硫酸钙的结晶机制及相应的硫酸钙结晶动力学研究可为该脱硫废液的减量化处理和工程设计提供技术支持。通过对脱硫废液的水质特征分析、沉淀和蒸发结晶,采用显微镜、SEM-EDS及XRD等分析手段,解析结晶产物的微观特征,并研究硫酸钙的结晶机制和结晶动力学行为。结果表明,脱硫废液pH值的不同可导致不同金属离子的沉淀,废液中的重金属离子随着碱度的提高先行沉淀析出,然后废液中的镁离子主要以氢氧化镁的形态沉淀。蒸发结晶过程中废液中的氯离子等杂质存在则影响硫酸钙晶体的结晶和规整度,较高浓度的氯离子优先以氯化物结晶体析出。硫酸钙的结晶过程为晶体成核、晶体生长、晶簇团聚及晶粒成长的渐进历程,由于废液中的杂质可能成为晶核,致使硫酸钙结晶的速率更快,但其变化规律与纯硫酸钙的结晶一致。脱硫废液中硫酸钙晶体的成核速率在很大程度上取决于溶液的过饱和度,钙离子过饱和度越大则结晶速度越快。蒸发过程中硫酸钙晶体生长过程可拟合为1.38级反应过程,反应速率常数为34.62,结晶反应速率方程为r=34.62C1.38。

As the size and habit of calcium sulfate crystals in the desulfurization waste water can directly lead to theireasy accumulation on heat exchange surfaces and difficulty to clear. The crystallization condition affects the productionprocess, equipment configuration, and process economics. Therefore, the study of the crystallization mechanism ofcalcium sulfate and the corresponding crystallization kinetics of calcium sulfate can provide technical support for thereduction treatment and engineering design of this desulfurization waste water. The microscopic characteristics of thecrystallization products were analyzed by means of microscope, SEM⁃EDS and XRD, and the crystallization mecha⁃nism and crystallization kinetics of calcium sulfate were studied. The results show that, the different pH value of thewaste liquid can lead to the precipitation of different metal ions, and the heavy metal ions in the waste liquid precipi⁃tate first with the increase of alkalinity, then the magnesium ions in the waste liquid precipitate mainly in the form ofmagnesium hydroxide. The existence of chloride ion and other impurities in the waste liquor affects the crystallizationand regularity of calcium sulfate crystal. The crystallization of calcium sulfate is a gradual process of crystal nuclea⁃tion, crystal growth, crystal cluster aggregation and grain growth, but the change rule is consistent with the crystal ofpure calcium sulfate. The nucleation rate of calcium sulfate crystal in desulphurization waste liquor largely depends onthe super⁃saturation of solution, the higher the super⁃saturation of calcium ion, the faster the crystallization rate. Thegrowth process of calcium sulfate crystal during evaporation can be fitted into a 1. 38 order reaction process, the reac⁃tion rate constant is 34. 62, and the crystallization reaction rate equation is r = 34. 62C.