柴达木盆地盐湖巨化学系统全组分、全浓度、多温热力学模型构建及模拟预测系统集成

Salt lake brine in Qaidam basin is a complicated system that involves 12 components (Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+//SO42−, Cl−, and borate-H2O)). The development and integration of the thermodynamic modeling system, in the scale of full components, full concentration and multi-temperatures, is of essential importance for the highly efficient separation and utilization of valuable resources. For developing such a modeling system, the following key scientific issues will be solved：i: thermodynamic model development for representing the properties of complicated salt lake brine with extremely high concentration and strong ionic association; ii: strategy of reliable parameter regression to guaranty their physical significance and extrapolation ability; iii: thermodynamic quantity estimation of model parameters which is difficult to determine experimentally; iv: strategy of phase equilibria calculation for multi-dimensional brine systems; v: strategy for expression of multi-dimensional phase equilibria. Then, a comprehensive modeling system will be constructed by integrating various type of thermodynamic properties of low-dimensional systems in a unified thermodynamic framework. As the first computer modeling system in the world developed especially for the phase equilibria simulation of the salt lake brines, it can be applied to accurately predict the phase equilibria of the complicated salt lake brine under arbitrary conditions and simulate the evaporation processes of natural or mixed brines at ambient or artificial temperatures. The developed modeling system will provide fundamental methods for the design of highly efficient extraction and separation strategies of valuable elements in salt lake brines.

柴达木盐湖卤水是一个涉及12种组分（Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+//SO42−, Cl−, B4O72-, BO2-, H3BO3-H2O)和上百个固相的巨化学系统，资源的高效利用迫切需要建立一套统一的理论来描述和预测它们的行为。本项目通过解决i:描述超高浓度和复杂缔合电解质溶液性质的热力学模型确立; ii:巨化学系统参数简化、物理意义和外推能力保障方案；iii:难实验测定参数的估算方法；iv:多维相平衡计算方案；v:多维相平衡表达等关键科学问题，集成低维盐湖体系各类热力学数据，建成世界上第一个专门针对盐湖化工相平衡的一站式动态模拟系统，实现在全组分、全工艺温度和全盐浓度范围的任一组成盐湖卤水在任意工艺条件下结晶过程的准确定量化模拟计算，模拟预测真实卤水体系在天然或强制等温蒸发和调卤过程的结晶规律，为盐湖有价元素高效分离提取的方案设计提供理论支撑。

我国柴达木盆地盐湖富含锂、钠、钾、铷、铯、镁、钙、锶、硫酸盐、硼酸盐、氯化物等宝贵资源，资源的高效提取迫切需要掌握这些资源所涉及的Li+,Na+,K+,Rb+,Cs+,H+,Mg2+,Ca2+,Sr2+//BxOy3x-2y,SO42-,Cl--H2O体系及其上千个子体系在多温和宽浓度范围的溶解度相图。而目前世界上缺乏专门针对盐湖的模拟预测系统。在本项目的支持下，我们开发了盐湖巨化学模拟预测系统。. 项目的主要研究内容及成果如下：. 1）在热力学模型框架方面，为表征高浓度体系盐-盐相互作用非线性增强的问题，我们用高阶水项替代原来的三离子作用项，强化了水对阴阳离子缔合强度的调节作用，使得模型能够表达超高浓度盐湖卤水体系性质。同时，重新推导了中性分子对离子活度系数的表达式，使得一切含H3BO3的数百个体系的相图计算成为可能。. 2）从热容出发关联上百个固相的焓、熵和吉布斯能，确保了参数的物理意义和温度外推能力，减大幅少模型参数约500个。. 3）模型中引进固溶体的相平衡计算，使得模型能准确描述和预测易形成固溶体的元素（铷、铯）在盐湖化工中的走向。. 4）我们引进不动点线性收缩算法，确保了巨化学体系相图计算过程的收敛性。采取了基于元素守恒的计算策略，实现了多种固溶体共存和酸碱平衡体系的可靠计算。. 5）突破传统相图表达的窠臼，提出并践行了用“单点平衡计算+脚本文件”的方式来表达多维相图的思路。. 6）开发了适合测定稀盐溶液偏摩尔热容的功率补偿型差式流动量热仪，精度比热流型量热仪至少高1个数量级，补充测定了一系列单个盐湖体系的热力学数据。. 7）开发的模型能准确预测盐田滩晒过程锂盐结晶损失的拐点、铷突然消失的机理、冬季冻硝提高钾光卤石的质量和锂回收率等，表现出高度的可靠性与实用性。. 通过本项目工作，建成了世界首个专门针对盐湖巨化学体系相平衡的模拟预测系统，国内外同行纷纷表达极大的应用兴趣，来电来函索取使用。项目的实施，培养了硕（博）士研究生28（5）名，发表论文40篇，申请了软件著作权1件，获授权发明专利10项。