LiCl、CaCl2和NaCl-CaCl2水溶液体系低温相变过程的X射线衍射法研究

Processes of the Phase Changes for LiCl,CaCl_2 and NaCl-CaCl_2 Aqueous Solutions at the Subzero-Temperature with X-ray Diffraction Method

本文使用低温X射线衍射法对不同浓度的LiCl、CaCl2和NaCl-CaCl2水溶液在降温过程中的相变情况进行了实时监测,获得了降温过程中的衍射图。结果显示,在快速降温的实验条件下,随温度降低,CaCl2溶液在-10～-60℃范围内析出冰或CaCl2·6H2O;LiCl溶液在5～-80℃范围内析出冰或LiCl·H2O;CaCl2-NaCl溶液在5～-40℃范围内析出CaCl2·6H2O或NaCl、冰。实验结果与相图的对比验证了这一实验方法的可行性。根据实验结果推断,本实验条件下固相可能先以无水盐的形式析出,而水合盐的形成则需要更长的平衡时间。本文的实验方法可为其他油田卤水子体系低温相平衡的研究提供有用信息,进而为油田水低温下结晶析盐规律的研究奠定基础。

The X-ray powder diffraction patterns of the solids of CaCl2-H2O,LiCl-H2O,NaCl-CaCl2-H2O systems at different temperature（the temperature of each system was quickly lowered from 5～-80 ℃） were determined.For the CaCl2-H2O system,with the decrease of the temperature,ice or CaCl2·6H2O was precipitated at the temperature range of-10～-60 ℃.For the LiCl-H2O system,ice or LiCl·H2O was obtained as the solid phase at the temperature range of 5～-80 ℃.For CaCl2-NaCl-H2O system,CaCl2·6H2O or NaCl、ice was precipitated at the temperature range of 5～-40 ℃.The XRD results of the CaCl2-H2O,LiCl-H2O and NaCl-CaCl2-H2O systems are consistent with the outcomes of the corresponding phase diagrams.According to the experimental results,we might deduce that the anhydrous salts were formed firstly,and the hydrated solids were obtained with the extension of the equilibrium time.This study provides a reliable method for determining the solid phases of the brine or oilfield water systems.