【作者】 姜晓滨；

【导师】 王静康；

【作者基本信息】 天津大学 ， 化学工程， 2012， 博士

【摘要】 高纯磷酸作为高端的电子化学品,在国内外电子工业中有着广泛的应用。为了制备高品质的高纯磷酸产品,本论文对高纯磷酸的熔融结晶制备技术进行了系统工程的研究,开发出了液膜结晶和静态多级熔融结晶两种制备高纯磷酸的结晶技术,已制备出符合国际标准的高纯磷酸产品。本研究中,精确测定了高纯磷酸的基础物性数据,包括常见浓度和温度下的密度与黏度、不同浓度和温度下磷酸晶层的导热系数、理想逐步冻凝状态下磷酸主要杂质组分在晶层和液相中的分配系数,为结晶过程数学模型的建立提供了基础数据。分别应用间隙体积法和直接测量法,测定了液膜结晶和静态熔融结晶中的磷酸晶层生长过程和发汗过程的宏观动力学数据。按照粒度无关生长模型建立了晶层生长动力学方程;以温度梯度为推动力建立了发汗过程的动力学方程,同时引入晶层结构参数,对发汗过程的阻力因素进行了深入分析,完善了发汗过程的动力学理论。在前人研究工作的基础上,采用热量衡算、边界层传质理论和相平衡,分别建立了液膜结晶动态过程和静态熔融结晶过程的数学模型,取得了良好的拟合结果。在此基础上提出了加晶种温度、原料初始浓度、喷淋密度、降温速率、降温终点温度、发汗终点温度作为关键工艺参数。对于熔融结晶过程中研究较少又极为重要的排液过程,创新性地引入分形多孔介质理论,建立了适用于熔融结晶晶层体系的数学模型,取得了很好的拟合结果,得到了晶层的结构和特性参数以及过程的优化参数,该模型还可用于其他物系熔融结晶过程的晶层结构和特性分析。在高纯磷酸结晶过程研究、模型建立和模拟等上述研究基础上,分别对液膜结晶和静态熔融结晶的工艺进行了深入的实验研究。实验考察了各种操作工艺参数对产率和分离效果的影响,提出了液膜结晶工艺方案。针对静态熔融结晶中晶层细晶较多,杂质包藏随结晶塔长度而增加的问题,开发了静态多级熔融结晶工艺。该工艺可以有效地消除细晶,提高静态熔融结晶过程的分离效率,从而获得高质量的高纯磷酸产品。最后,对液膜结晶和静态多级熔融结晶两种结晶模式关于生产能力和分离效果进行工业化应用的初步技术经济指标分析,最终提出了两种结晶模式联合操作的优化工艺方案,具有工业化应用前景,可以有效地提高了过程的分离效率,产率及整体生产能力。所开发工艺路线达到了废液零排放,能耗低,为绿色环境友好型工艺,具有较大的产业化意义。该技术亦可推广应用于其他熔融结晶制备高纯晶体产品的过程中。以上有关研究内容尚未见文献报道。更多还原

【Abstract】 Hyperpure phosphoric acid, which belongs to high end electronic chemical, has an immense demand in electronic industry and wide market prospect. In order to prepare high quality hyperpure phosphoric acid product, the system engineering investigation on melt crystallization preparing hyperpure phosphoric acid has been performed. By means of two different new crystallization technology-liquid film crystallization (LFC) and static multistage melt crystallization (SMC)-the hyperpure phosphoric acid product, which comes up to the multiplex international standards, has been successfully prepared.In this work, the density and viscosity of hyperpure phosphoric acid under common temperatures and concentrations had been accurately measured. The heat conductivity coefficient of phosphoric acid crystal layer under different temperatures and initial concentrations were also measured. In addition, the distribution coefficient of main ion impurities between crystal layer and liquid phase were determined, all these data have built a foundation for mathematical model.The macroscopic crystal layer growth and sweating kinetic data of LFC and SMC have been determined by intermittent volume method and direct measurement method, respectively. The crystal later growth kinetic equations were established with size-independent growth rate model; the sweating kinetic equations were established with the temperature gradient as driving force. In addition, we analyzed the resistance factors during sweating process and completed the sweating kinetics theory by introducing the paratmeters of layer structure.On the basis of predecessors’work, the liquid film crystallization dynamic model and static melt crystallization model have been established by heat balance calculation, boundary layer mass transfer theory and phase equilibrium. The models obtained good fitting results on two melt crystallization modes. We selected the seed ing temperature, material initial concentration, sprinkle density, cooling rate, cooling endpoint temperature and sweating endpoint temperature as the key technological parameters.On the seeping, which is distinctly important in melt crystallization research, the mathematical model which applied to melt crystallization crystal layer system had been established and a good fitting result had been obtained by introducing fractal porous media theory; the structure and characteristic parameters of crystal layer can also be obtained from the model. This mathematical model can be applied to the analysis of crystal layer structure and characteristic in other melt crystallization cases.Based on the above investigation of hyperpure phosphoric acid crystallization process, model establishment and simulation, crystallization and sweating kinetic researches, we had in-depth studied the LFC and SMC technology. The effects of operation conditions on the crystallization process and separation effect were investigated in detail by both experiments and model simulation, and the optimal operation strategy of LFC was established. In order to solve the problem of too much fine crystal in crystal layer and impurities parceled increasing with length, the static multi-step melt crystallization technology was developed. The hyperpure phosphoric acid can be obtained by this technology for the fine crystal had been effectively eliminated.On the basis of above research, we compared LFC and SMC on production capacity and separation efficiency with the method of elementary technical and economic index analysis. As a conclusion, we proposed the combining operation technology of two crystallization modes and optimized process scheme, which effectively increased the separation efficiency, yield and production capacity. In addition, this technology has achieved the zero release of liquid waste and low energy consumption, which believe to be a green-environment friendly technology. This combining melt crystallization technology has important significance for industrialization and can also be spread and applied to other hyperpure crystal product preparation with melt crystallization method, too.No same report to above study results have been published in literature up to date.更多还原