硝酸钙-磷酸-水-异丙醇体系中溶析结晶工艺研究

酸解液中氮磷的高效分离是发展硝酸法湿法磷酸的关键技术之一。提出采用溶析结晶使酸解液中磷以磷酸钙盐形式析出从而达到氮磷分离的研究思路。以异丙醇为溶析剂，通过单因素实验考察了溶析剂加入比（异丙醇与模拟酸解液质量比）、温度、五氧化二磷质量分数、溶析时间对析出晶体物相结构以及磷析出率的影响。结果表明，溶析时间不会影响析出晶体物相结构，增大溶析剂加入比、升高温度、降低五氧化二磷质量分数都会使得析出的晶体由磷酸二氢钙转变成磷酸氢钙。通过对比磷析出率得出适宜的工艺条件：溶析剂加入比为3∶1、温度为5.0 ℃、五氧化二磷质量分数为30%、溶析时间为1.0 h，在此条件下磷析出率可达73.58%。

Study on antisolvent crystallization process in calcium nitrate-phosphoric acid-water-isopropanol system

The efficient separation of nitrogen and phosphorus in acid hydrolysis solution is one of the key technologies for the development of nitric acid wet phosphoric acid process.The research idea of using antisolvent crystallization to precipitate phosphorus in the form of calcium phosphate in the acid hydrolysis solution was put forward，so as to achieve the separation of nitrogen and phosphorus.Using isopropanol as the antislovent，the effect of antisolvent addition ratio（mass ratio of isopropanol to simulated acidolysis solution），temperature，P₂O₅ mass fraction and antisolvent time on the phase structure and phosphorus precipitation ratio of precipitated crystals was investigated by single factor experiment.The experimental results showed that the antisolvent time did not effect the phase structure of the precipitated crystals.Increasing the antisolvent addition ratio，increasing the temperature and reducing the mass fraction of P₂O₅ would change the precipitated crystals from monocalcium phosphate to dicalcium phosphate.By comparing the phosphorus precipitation ratio，it was concluded that the suitable process conditions were as follows：the antisolvent addition ratio was 3∶1，the temperature was 5.0 ℃，the mass fraction of P₂O₅ was 30%，and the antisolvent time was 1.0 h.At this time，the phosphorus precipitation ratio was 73.58%.