湿法脱硫塔氧化区内脱硫石膏结晶机理及其动力学特性

This project is aiming at reducing the concentration of fine particles come from the limestone-gypsum wet flue gas desulfurization tower by controlling the size of gypsum. Adopt the method of theoretical analysis, experimental research and numerical simulation, the micro dynamics of crystallization under the complete mixing flow condition and the macro dynamic of crystallization under the non-uniform suspension condition are investigated in the oxidation area of the wet desulfurization tower, and the effect of them on crystal size distribution is taking into more consideration. Using experimental research, the basic data of solution solubility, induction time and the meta-stable zone width are expanded. Combined with the nucleation theory, the nucleation mechanism is deduced, the nucleation rate is derived. According to the crystallization kinetics theory and the peak intensity of crystal gained by Raman spectroscopy et al., the overall crystal growth rate is derived. In the CFD commercial software platform, by introducing the crystal growth rate obtained from the experimental study, the solution method of population balance equation coupled with multiphase flow is established. Furthermore, the crystal size distribution in the oxidation and crystallization zone of desulfurization tower is predicted by CFD simulation. When the conditions permit, the accuracy and applicability of the model will be verified with the data from the real tower. These results should provide some necessary theoretical support and basic data for the microscopic mechanism of gypsum crystallization and crystal size control in limestone-gypsum wet desulfurization process.

以控制石膏粒径进而减少石灰石-石膏湿法脱硫塔出口细颗粒物浓度为背景，采用理论分析、实验研究和数值模拟相结合的研究思路，以湿法脱硫塔氧化区为研究对象，研究全混流条件下结晶的微观动力学特性、非均匀悬浮条件下结晶的宏观动力学特性及其对晶体粒度分布的影响机制。采用实验研究的方法，扩充溶液溶解度、诱导时间和介稳区宽度等基础数据；结合成核理论，推断成核微观机理，推导成核速率；根据结晶动力学理论和拉曼光谱等所得晶体峰强度推导晶体生长速率；在CFD商业软件平台上，通过引入实验所得晶体生长速率模型，建立与实验数据吻合的多相流与粒数耦合的CFD求解方法；进而采用上述模型对工业尺寸的脱硫塔氧化结晶区内的晶体粒度分布进行预测，并采用现场数据进行模型准确性和适用性的对比分析。为石灰石-石膏湿法脱硫过程石膏结晶的微观机理及粒度控制提供理论支撑和基础数据。

本项目以控制石膏粒径进而减少石灰石-石膏湿法脱硫塔出口细颗粒物浓度为背景，采用理论分析、实验研究和数值模拟相结合的研究思路，采用实验研究的方法，更加全面的分析了石膏的物理化学性质，扩充了溶解度和诱导时间等基础数据；在拉曼光谱平台上，建立了硫酸盐定量测试方法，并考察了温度和杂质对测试模型的影响；结合成核理论，推断了均相成核和非均相成核的可能分界点，推导了成核速率；在CFD商业软件平台上，通过添加用户自定义子程序，建立了基本流动模型、传质、传热和粒数衡算模型，并对6种曳力模型的适用性进行了重点分析；进而采用上述模型对工业尺寸的脱硫塔进行了数值模拟，主要考察了具有区域特征的流动特性、pH分布和SO2浓度分布，以及氧化结晶区随时间变化的晶体粒度分布。以上研究旨在为石灰石-石膏湿法脱硫过程石膏结晶的微观机理及粒度控制提供理论支撑和基础数据。