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过程工程学报 ›› 2021, Vol. 21 ›› Issue (3): 286-297.DOI: 10.12034/j.issn.1009-606X.220084

• 反应与分离 • 上一篇    下一篇

273 K及323 K条件下NaCl–NaBr–CH3OH三元体系相平衡 研究及其应用

吴 耀1,2, 李 雲1,2, 郭宏飞1,2, 刘秀伍1,2, 陈学青1,2, 曹吉林1,2*   

  1. 1. 河北工业大学化工学院,天津 300130 2. 河北省绿色化工与高校节能重点实验室,天津 300130
  • 收稿日期:2020-03-13 修回日期:2020-05-09 出版日期:2021-03-22 发布日期:2021-03-23
  • 通讯作者: 曹吉林
  • 基金资助:
    MgCl26H2O-Mg(OH)2-MgO技术路线制备高纯镁砂过程基础研究;河北省自然科学基金项目

Study on phase equilibrium of NaCl–NaBr–CH3OH ternary system at 273 K and 323 K and its application

Yao WU1,2, Yun LI1,2, Hongfei GUO1,2, Xiuwu LIU1,2, Xueqing CHEN1,2, Jilin CAO1,2*   

  1. 1. College of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130, China 2. Hebei Provincial Key Laboratory of Green Chemical Technology and High Efficient Energy Saving, Tianjin 300130, China
  • Received:2020-03-13 Revised:2020-05-09 Online:2021-03-22 Published:2021-03-23
  • Contact: CAO Ji-lin
  • Supported by:
    ;Project of Natural Science Foundation of Hebei Province

摘要: 为了对苦卤结晶析出的Na(Cl,Br)固溶体中氯化钠组分和溴化钠组分进行分离,测定了NaCl–NaBr–CH3OH三元体系在273及323 K温度时的溶解度数据,根据测得的液相点和湿渣相点确定了对应的固相点,由此绘制出了两个温度下的相图。结果显示,273及323 K温度下该三元体系的相图特征相似,均只有一个共饱点、两条饱和溶解度曲线,对应的固相结晶区有三个:NaCl纯盐结晶区、NaCl和Na(Cl,Br)固溶体共结晶区、Na(Cl,Br)固溶体结晶区。NaBr在无水甲醇中溶解度的增大导致NaCl溶解度大幅减小,说明NaBr对NaCl产生了较强的盐析效应,273 K时两种溶质在甲醇中的溶解度均比323 K时的溶解度大。依据273和323 K的NaCl–NaBr–CH3OH体系相图及298 K的NaCl–NaBr–H2O体系相图设计了分离Na(Cl,Br)固溶体中氯化钠和溴化钠的工艺。

关键词: 苦卤, 相平衡, Na(Cl,Br)固溶体, 甲醇, 溶解度, 分离

Abstract: In order to separate sodium chloride and sodium bromide from the solid solution Na(Cl,Br) crystallized from bittern, the isothermal solubility data of NaCl–NaBr–CH3OH ternary system at 273 and 323 K was measured by isothermal solution equilibrium method, and the solid phase points were determined according to the measured liquid phase points and wet slag phase points, from which the phase diagrams at two temperatures were obtained. The results showed that the phase diagram characteristics of the ternary system were similar at 273 and 323 K. There was only one invariant point and two univariant curves, and there were three solid-phase crystallization regions: NaCl pure salt crystallization region, the co-crystallization zone of NaCl and Na(Cl,Br) solid solution and Na(Cl,Br) solid solution crystallization region. This was different from the phase diagram of NaCl–NaBr–H2O system, which only had the crystallization region of solid solution. The liquid composition of the invariant point at 273 K was 0.2904wt% NaCl, 14.66wt% NaBr and the liquid composition of the invariant point at 323 K was 0.2529wt% NaCl, 13.45wt% NaBr. The mass fraction of NaBr at the boundary of the solid solution crystallization region at 273 and 323 K was 28.93% and 34.28%, respectively. The solubility of NaBr in anhydrous methanol was much higher than that of NaCl, which indicated that NaBr had a strong salting-out effect on NaCl, and the solubility of these two solutes in methanol at 273 K was higher than that at 323 K, which was opposite to that in aqueous solution. According to the phase diagrams of NaCl–NaBr–CH3OH system at 273 and 323 K and NaCl–NaBr–H2O system at 298 K, the process for the separation of sodium chloride and sodium bromide was designed. Not only the pure salt of NaCl was obtained, but also solid solution with extremely high NaBr content was obtained. And the mass fraction of NaBr in the separated solid solution was 98.06% and 98.15%, respectively.

Key words: bittern, phase equilibria, Na(Cl,Br) solid solution, methanol, solubility, separation