熔融结晶法净化磷酸过程研究

发布时间：2018-02-09 11:30

本文关键词： 湿法磷酸熔融结晶洗涤塔 Aspen Material Studio　出处：《华东理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：湿法磷酸是重要工业原料,但杂质含量高,必须净化后才能应用于下游行业。工业上大规模采用萃取法净化磷酸,存在溶剂难以去除的问题。与萃取法相比,结晶法不使用溶剂,可简化工艺流程、降低能耗、而且环境友好,符合工业发展趋势,是一种极具潜力的方法。但结晶法多为间歇操作,净化效率和产能有限,难以满足工业化需要。因此,开发连续化结晶技术是结晶法净化湿法磷酸技术工业化的关键。为此,本研究采用连续化悬浮熔融结晶逆流洗涤工艺净化湿法磷酸。采用虹吸技术实现了晶浆的稳定输送,固液预分离环节强化了逆流洗涤过程,成功解决了连续化熔融结晶逆流洗涤操作过程的关键问题。并研究了洗涤塔的晶体沉降速度、融化速率等性能,为该技术的工业化实践奠定了基础。本文首先用Aspen plus模拟了磷酸体系的密度和黏度,验证了Aspen plus模拟获取磷酸的物性参数及相图的可行性。用Material Studio模拟软件的morphology模块预测H3PO4·0.5H2O晶体的理论形貌,AE模型所得与实际形貌最接近。通过分子动力学计算磷酸体系中典型杂质扩散系数,得出Cl-的扩散系数最大。用离子间的径向分布函数(RDF)解释了体系中离子与水分子的微观作用。用discover模块计算杂质对H3PO4·0.5H2O晶体各晶面的影响,结果表明阳离子中Fe2+,阴离子中S042-对各晶面生长速率的影响较大。其次,本文通过对比静态与悬浮熔融结晶过程得出悬浮熔融结晶所得晶体颗粒小,分布均匀,便于输送,适宜于连续化操作。两种操作方式杂质去除率都随结晶时间增长而增大。悬浮熔融结晶对于Fe3+和F-的去除率高于静态熔融结晶,同时多级重结晶能更有效提纯晶体。最后,在本研究所设计的结晶设备中,洗涤塔的沉降段实现晶体的逆流洗涤过程,通过实验得到晶体沉降速率在6.61mm/s,与在T=293.2K,dp=3mm条件下理论计算得到的沉降速率6.88mm/s相近。通过洗涤塔的洗涤,晶体除杂率为50%左右,且回流比越大,提纯效果越好,在回流比R=6时,除杂率能达到60%。
[Abstract]:Wet process phosphoric acid is an important industrial raw material, but its impurity content is high, it must be purified before it can be used in downstream industry. The crystallization process without solvent can simplify the process process, reduce energy consumption, and is environmentally friendly and in line with the trend of industrial development. It is a promising method. However, the crystallization process is mostly batch operation, and the purification efficiency and capacity are limited. It is difficult to meet the needs of industrialization. Therefore, the development of continuous crystallization technology is the key to industrialization of purification of wet phosphoric acid by crystallization. In this study, the continuous suspension melt crystallization countercurrent washing process was used to purify the wet phosphoric acid. The siphon technology was used to realize the stable transportation of the crystal slurry, and the solid-liquid pre-separation process strengthened the countercurrent washing process. The key problem of continuous melt crystallization countercurrent washing operation has been solved successfully, and the properties of the crystal sedimentation rate and melting rate of the scrubber have been studied. In this paper, the density and viscosity of phosphoric acid system were simulated by Aspen plus. The feasibility of obtaining physical parameters and phase diagrams of phosphoric acid by Aspen plus simulation was verified. The theoretical morphology model of H3PO4 路0.5H2O crystal was predicted by morphology module of Material Studio simulation software. The diffusion coefficient of typical impurity in the system, It is concluded that the diffusion coefficient of Cl- is the largest. The microcosmic interaction between ions and water molecules in the system is explained by the radial distribution function between ions. The influence of impurity on the crystal faces of H _ 3PO _ 4 路0.5H _ 2O crystal is calculated by discover module. The effect of S042- in anion on the growth rate of each crystal plane is great. Secondly, by comparing the static and suspended melting crystallization processes, it is found that the crystal particles obtained by suspension melt crystallization are small, uniform distribution and easy to transport. The removal rate of impurities increases with the increase of crystallization time. The removal rate of Fe3 and F- in suspension melt crystallization is higher than that in static melt crystallization, and multi-stage recrystallization can purify the crystal more effectively. In the crystal equipment designed in this paper, the sedimentation section of the washing tower realizes the process of crystal countercurrent washing. The crystal sedimentation rate is 6.61 mm / s through experiment, which is close to that calculated theoretically under the condition of 3mm T _ (293.2KN) dpg ~ (3 mm), and the washing through the washing tower, The impurity removal rate of the crystal is about 50%, and the higher the reflux ratio is, the better the purification effect is. When the reflux ratio is 6:00, the impurity removal rate can reach 60%.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ126.35

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