Research On Thermodynamic And Solid-liquid Equilibrium Of Lithium Brine System

It is an important tool to study salt water phase diagram system for salt water system.With the support of national natural fund project,we carry out the study on thermodynamic model related to the qinghai salt-lake system for scientific problem about the phase equilibria in the chloride type and sulfate type and subtype of salt-lake open complex giant system.We obtained the liquid model parameters through solution properties,determined thermodynamic constant of solid salts by solid-liquid phase equilibrium datas,predicted the solid liquid equilibrium of the ternary and quaternary system.On this basis,we carried out the study on the salting-law of evaporating lithium salts and the technology of extracting lithium sulfate for sulfate-type salt-lake.The key process datas of the production of lithium sulfate by brine transformation method were obtained.It provides reference for the development and comprehensive utilization of lithium brine resources in sulfate-type salt-lake.The system involved in this study is related to lithium,potassium/sodium and magnesium in qinghai salt lakes.(1)Study on solution property simulating and solution parameters.Simulating the experimental data of the chemical and physical properties of solution(saturated vapor pressure,activity coefficient and permeability coefficient,eat capacity),we determined 6 electrolyte-water pairs interaction parameters for the LiCl + H2O,Li2SO4+H2O,KCl + H2O system by using symmetrical eNRTL model;For MgCl2 + LiCl +H20,LiCl + KCl + H20,Li2SO4 + MgS04 + H2O,LiCl + Li2SO4 + H20 ternary system,8 electrolyte-electrolyte pairs interaction parameters are redefined by fitting solid-liquid phase equilibrium datas and thermodynamic properties for the ternary system.(2)Study on solid-liquid equilibrium simulating and thermochemical data of solid salt.Simulating the solubility of binary system at whole temperature range,we obtained thermodynamic constant(the standard gibbs free energy,standard formation enthalpy,etc)of 16 solid salts for the LiCl + H2O,Li2SCO4+ H2O,KC1 + H2O binary systems by using solid-liquid phase equilibrium model;The thermodynamic constants of the double-salt are determined by simulating solubility data for the ternary system.(3)Multivariate system full temperature phase equilibrium prediction and phase diagram integration.On the basis of the study of binary system and ternary system,the temperature continuous and visual integration of the complete phase diagram of the four ternary system is obtained.Using the parameters of liquid phase and solid phase thermodynamic constant,the dry base diagram and water diagram for Li+,Na+,K///Cl--H2O quaternary system and Li+,Na+ Mg2+//SO42-quaternary system are obtained under multitemperature.The consistency of the results of the model calculation and the literature datas are satisfactory.It is shown that the model is successful in calculating the physical and chemical properties of the solution,thermodynamic constants and prediction of multiphase diagrams.(4)Development of lithium brine extraction process in salt-lake.Study on the rule of evaporative lithium salt and the extraction technology of lithium sulfate for the Li+contained brine.The key process data of the production of lithium sulfate by brine transformation was obtained.The research results will provide references for the development and comprehensive utilization of lithium brine resources.