【作者】 李翠屏；

【导师】 武斌；

【作者基本信息】 华东理工大学 ， 化学工程， 2012， 硕士

【摘要】 溶剂萃取是湿法磷酸净化的主流方法。湿法磷酸成本较热法磷酸低,但杂质含量较高,在用于制备纯度等级较高的磷酸盐产物时往往需要采用溶剂萃取等方法进行净化处理。现有溶剂萃取工艺通常包括：湿法磷酸浓缩、萃取、洗涤、反萃等步骤,再以所得的反萃磷酸作为制备磷酸盐的出发原料。从理论上分析,通过有机相中磷酸的直接反应制备磷酸盐产物,可以省去反萃取操作；通过对萃取相磷酸反应进程的分阶段控制,有可能得到不同纯度等级的磷酸盐产物。本文以此为背景开展研究工作,以磷酸铵盐作为目的产物。采用的工艺流程包括湿法磷酸浓缩、多级萃取、多级洗涤、成盐反应,萃取中以甲基异丁基甲酮为萃取剂。通过该工艺流程,可以得到不同等级的磷酸铵盐,其中一部分是高纯度的铵盐。为了建立分级反应制备高纯磷酸铵盐的方法,先考察目的产物磷酸铵盐和杂质盐在非水介质中溶解过程的热力学特性。研究了磷酸氢二铵、磷酸二氢铵、磷酸铁和硫酸铵在甲基异丁基甲酮中的溶解平衡特性,并且比较了不同温度下杂质盐的结晶析出的顺序与中和度之间的关系。由研究结果知,温度区间为25～35℃时,水饱和的甲基异丁基甲酮中溶解度大小排序为：磷酸二氢铵<硫酸铵<磷酸铁<磷酸氢二铵,温度35℃时有利于分级成盐反应的进行。在此基础上,提出了分级反应制磷酸铵盐的初步流程,对提出的流程开展工艺学研究。为了提高分级反应制高纯度磷酸铵盐的需要,湿法磷酸的前端净化应该在较优化的条件下进行。考虑反应对净化酸纯度的要求,经实验验证,萃取净化的最佳条件：酸浓度为75%-79%,有机溶剂和酸的质量比为1.2：1,温度为30℃；洗涤净化的最佳条件：洗涤酸浓度为53%～54%,温度为30℃,萃取有机相与洗涤酸相的质量比为mO:mA=1:0.4。在上述研究的基础上,用净化的湿法磷酸制备磷酸铵盐,在成盐反应过程中,通过控制反应中和度,在反应的各阶段分别制得工业级磷酸盐、食品级磷酸盐和高纯级磷酸盐。反应产物直接结晶析出,与传统方法中蒸发水得到磷酸盐产品的过程相比,省去了水的蒸发,存在节能的潜力。更多还原

【Abstract】 Solvent extraction is the main method of purification of wet phosphoric acid, its costs are lower than thermal phosphoric acid, but its impurities level is higher, so wet phosphoric acid is required to be purified by solvent extraction or other methods in the preparation for the high purity grade phosphate products. Present solvent extraction process typically includes: concentration, extraction, scrubbing, back-extraction and so on, the back-extracted phosphoric acid is then used as the starting materials for preparation of phosphates. From the theoretical analysis, phosphoric acid in organic phase can directly react to prepare for phosphates, which can eliminate back-extracting operation. Through controling the neitralisation reaction degree of phosphoric acid, different purity level phosphates may be got by crystallisation from extract phase.With ammonium phosphates as end products, a coupling process of extractive purification and stagewise reaction has been experimentally studied. The processes include: concentration, multi-stage extraction, multi-stage scrubbing and stagewise reaction, while methyl isobutyl ketone is used as extractant, through this process we can obtain different grades of ammonium phosphates (one part is high purity ammonium phosphates).In order to establish the method for preparation of high purity ammonium phosphates through stagewise reaction, thermodynamic properties of end products and impurities salts were firstly researched. The solid liquid equilibrium properties of monoammonium phosphate, diammonium phosphate, ferric phosphate and ammonium sulphate in methyl isobutyl ketone were studied. Known from researching result, when temperature was ranged from 25℃to 35℃, the sequence of solubilities in water-saturated methyl isobutyl ketone is listed as follows:monoammonium phosphate<ammonium sulphate<ironic phosphate<diammonium phosphate, and it will be more conductive to grading salt reaction at temperature of 35℃.On this basis, initial process of preparation of ammonium phosphate through grading reaction was proposed, and corresponding technological study was conducted. Studies indicated that the optimal conditions for extracting purification:acid concentration is from 75% to 79%, mass ratio between organic solvent and concentrated phosphoric acid is 1.2:1, the temperature is 30℃; the optimal conditions for scrubbing purification:the concentration of scrubbing acid is from 53% to 54%. mass ratio between organic extraction phase and scrubbing acid phase is 1:0.4. the temperature is 30℃.Based on the above research, the extractive purified wet phosphoric acid is used for production of ammonium phosphate by stagewise reactive crystallizaion, by controlling the reaction degree industrial grade, food grade and high purity grade phosphates can be obtained in the reacting process. Reaction products can be crystallized directly from the extract phase, so the traditional process of evaporating water to get phosphate products can be eliminated.更多还原