Determination and graphics expression of ice-salt eutectic points of multicomponent salt-water systems

doi:10.11949/j.issn.0438-1157.20151485

Abstract

Abstract:

For the quaternary salt-water systems, such as the homo-ion system K⁺//Cl^-, SO₄^2-, NO₃^--H₂O and interaction system Na⁺, K⁺//SO₄^2-, NO₃^--H₂O, as well as their six ternary subsystems, the freezing points, eutectic points and the crystallization regularities of salts were studied by cooling method. According to experimental data, the eutectic point temperature-liquid composition diagrams for these systems were plotted. The results were as follows: (1) The crystallization regularity of salts and the eutectic point temperatures can be obtained by measuring the time-temperature curves for multicomponent salt-water systems during cooling process; (2) In these systems above, 3K₂SO₄·Na₂SO₄ existing under normal temperature did not appear at the eutectic point temperature. As a result, the phase relationships in these systems were simplified; (3) The prism can be used to describe the relationships among the phases, freezing points or eutectic points and the compositions of liquids for the ternary systems, the quaternary homo-ion systems and interaction systems concisely and visually; (4) In the eutectic point temperature-liquid composition diagrams, for ternary systems without double-salts, there were two eutectic curves with single salt and ice, one eutectic point with two salts and ice, and one ice crystallizing region. For the quaternary homo-ion systems and interaction systems, there were three and four eutectic regions with single salt and ice, three and five eutectic curves with two salts and ice, and one and two eutectic points with three salts and ice, respectively.

Key words: salt-water system, eutectic point, temperature, phase

摘要：

水盐体系共晶点的数据可以为盐湖卤水低温加工工艺开发提供必要的理论依据,采用低温冷却法,针对四元同离子体系K⁺//Cl^-,SO₄^2-,NO₃^--H₂O和四元交互体系Na⁺,K⁺//SO₄^2-,NO₃^--H₂O及其相关的6个三元子体系,测定研究了其冰点、共晶点以及析盐规律,绘制出了共晶点温度-液相组成图。研究结果表明:通过测定多元水盐体系降温过程中的时间-温度图,可以判断盐类析出规律、测定冰和盐的共晶点温度;上述体系中,常温下存在的复盐钾芒硝,在共晶点温度下均不再出现,水盐体系相关系得以简化;用棱柱图可以简单直观地表达三元体系、四元同离子体系和四元交互体系的相、冰点或共晶点的温度和溶液组成的关系;在三元体系的共晶点温度-液相组成图中,存在两条单盐与冰的共晶线、一个两种盐与冰的共晶点、一个冰析出面;在四元同离子体系和四元交互体系共晶点温度-液相组成图中,分别有3个和4个单盐与冰的共晶面、3条和5条两种盐与冰的共晶线、1个和2个3种盐与冰的共晶点。

关键词: 水盐体系, 共晶点, 温度, 相

CLC Number:

O642.5⁺4

WANG Xueying, HUANG Wenting, HUANG Xueli. Determination and graphics expression of ice-salt eutectic points of multicomponent salt-water systems[J]. CIESC Journal, 2016, 67(5): 1687-1693.

王雪莹, 黄文婷, 黄雪莉. 多元水盐体系冰盐共晶点的测定和图形表达[J]. 化工学报, 2016, 67(5): 1687-1693.

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