磷酸二氢钾结晶行为及在聚醚精制后处理工艺中应用研究

发布时间：2018-05-12 04:19

  本文选题：磷酸二氢钾 + 介稳区　； 参考：《天津工业大学》2017年硕士论文

【摘要】：采用重结晶的方法研究了磷酸二氢钾在水溶液中的结晶行为,探讨了搅拌速率、降温速率、pH值及金属离子掺杂等因素对其介稳区宽度、结晶速率、结晶形态、晶体粒径大小及粒度分布等的影响规律,对磷酸二氢钾在水溶液中的结晶工艺进行了研究;在最佳结晶工艺条件下,晶体粒度分布均匀、粒径较大,将优化的结晶工艺应用到聚醚多元醇后处理精制过程中能明显缩短聚醚后处理精制周期,提高聚醚生产效率。研究表明:随着搅拌速率的增大磷酸二氢钾溶液介稳区宽度变窄,诱导期缩短,降温速率和溶液的pH 一定,当搅拌速率为300r/min时,结晶速率最小为0.43g/min;随着降温速率的增加,介稳区宽度逐渐增加,诱导期和晶体的平均粒径均减小,降温速率为0.3℃/min时,晶体的平均粒径最大为530.21μm;在pH=3时,介稳区宽度和诱导期达到最小,结晶速率达到最大为1.3g/min;控制搅拌速率为200r/min,降温速率为0.5℃/min,溶液的pH值为3.0时,从水溶液中结晶得到的磷酸二氢钾晶体颗粒均匀且粒径较大为417.65μm,并且此条件下结晶可有效防止晶簇。本文研究了磷酸二氢钾结晶技术在聚醚后处理实际生产过程中的应用,优化了针对不同分子量聚醚乳液中通过磷酸中和,结晶析出磷酸二氢钾,过滤等工序去除催化剂金属离子的聚醚后处理精制工艺。控制Na+/K+摩尔掺杂比为1:1,搅拌速率90～110r/min,pH值3～4范围内,能够得到粒度分布均匀、颗粒较大的磷酸二氢盐晶体;精制处理后聚醚中钾、钠金属离子平均含量分别为2.6ppm和2.2ppm,且钾钠离子含量的总和小于现行业5ppm的要求;磷酸二氢钾及磷酸二氢钠结晶析出颗粒较大,且形成了良好的架桥效应,体系粘度低,过滤速度快,能显著缩短聚醚后处理过滤循环及过滤时间,提高聚醚精制后处理过程的生产效率,聚醚后处理结晶工艺的优化对实际生产过程有着积极的指导意义。
[Abstract]:The crystallization behavior of potassium dihydrogen phosphate in aqueous solution was studied by recrystallization method. The effects of stirring rate, cooling rate, pH value and metal ion doping on the metastable zone width, crystallization rate and crystal morphology of potassium dihydrogen phosphate were investigated. The crystallization process of potassium dihydrogen phosphate in aqueous solution was studied under the optimum crystallization conditions, the crystal size distribution was uniform and the particle size was large. The application of the optimized crystallization process to the process of polyether polyol aftertreatment can obviously shorten the refining period of polyether and improve the production efficiency of polyether. The results show that with the increase of stirring rate, the width of the metastable zone of potassium dihydrogen phosphate solution becomes narrower, the induction period is shorter, the cooling rate and pH of the solution are constant, the minimum crystallization rate is 0.43 g / min when the stirring rate is 300r/min, and the minimum crystallization rate is 0.43 g / min with the increase of the cooling rate. The width of the metastable zone increases gradually, and the average particle size of the crystal decreases during the induction period. When the cooling rate is 0.3 鈩，

本文编号：1877071