一里坪盐湖卤水冷冻转化

取密度分别为1.215、1.218、1.221 g/cm3的一里坪盐湖晶间卤水分别在-5、-10、-15、-20 ℃进行冷冻除硫酸根实验，得到卤水冷冻除硫酸根最佳条件：卤水密度为1.215 g/cm3、冷冻温度为-15 ℃；当冷冻卤水中硫酸根质量浓度降低到原卤水中硫酸根质量浓度的1/3左右时进行固液分离。将盐湖卤水在选定条件下冷冻除硫酸根，固液分离后的卤水在实验室模拟自然蒸发。从卤水特征系数分析，冷冻后的卤水也应归入硫酸镁亚型盐湖卤水，但在自然蒸发过程中液相点的变化趋势符合25 ℃下Na+、K+、Mg2+∥Cl-—H2O四元体系相图。同时，将未经冷冻的原始卤水在实验室模拟自然蒸发时，液相点的变化趋势与Na+、K+、Mg2+∥Cl-、SO42-—H2O五元体系25 ℃介稳相图吻合。所以，从相图应用的角度看，硫酸镁亚型盐湖卤水通过冷冻脱硝实现了由五元体系向四元体系转化的可行性，从而可为一里坪盐湖卤水的开采利用提供工艺参考，并为硫酸盐型盐湖卤水的转型提供理论支撑。

Freezing conversion of brine in Yiliping salt lake

To achieve the optimal condition for desulfurization by freezing，the freezing experiment on Yiliping salt lake brine was conducted under different densities of 1.215，1.218，and 1.221 g/cm3 and temperature of -5 ℃，-10 ℃，-15 ℃，and -20 ℃，respectively.Results showed that the density of 1.215 g/cm3 and temperature of -15 ℃ can be selected as the best conditions for desulfurization.When the concentration of SO42- was decreased to approximately 1/3 of raw brine，the separation of solid and liquid was completed.The simulated natural evaporation on residual liquid has been conducted in laboratory.As far as the characteristic coefficient of brine was concerned，the brine frozen still belonged to magnesium sulfate subtype.Ho- wever，the evaporation behavior of liquid point could be in conformity with the Na+，K+，Mg2+∥Cl--H2O quaternary system at 25 ℃ and that of raw brine untreated should be explained by the Na+，K+，Mg2+∥Cl-，SO42--H2O quinary meta-stable system，which means that the chemical type of magnesium sulfate sub-type brine can be converted from quinary to quaternary by freezing in terms of application of phase diagram.It will provide technical reference for the exploitation of Yiliping salt lake and theoretical guidance for conversion of sulfate type salt lake brine.