Measurement and calculation of solid–liquid equilibria of two quinary systems LiBr–NaBr–MgBr2–SrBr2–H2O and LiBr–KBr–MgBr2–SrBr2–H2O at 298.15 K

Abstract

As an important strategic reserve resource, the comprehensive development and utilization of Nanyishan oil-gas field brine will bring great economic and social value. Here, according to the composition characteristics of this oil-gas field brine being rich in lithium, potassium and strontium, the solid-liquid stable phase equilibria and phase diagrams of Li-containing quaternary system (LiBr–MgBr₂–SrBr₂–H₂O) and two quinary systems (LiBr–NaBr–MgBr₂–SrBr₂–H₂O and LiBr–KBr–MgBr₂–SrBr₂–H₂O) were studied at 298.15 K. Based on the results of phase equilibrium experimental research, the phase equilibrium relationship and crystallization-dissolution behavior of each component in liquid phase were revealed theoretically, and the changing trend was summarized. Using theoretical model of Pitzer electrolyte solution, the relevant interaction parameters of mixed ions at 298.15 K were obtained by fitting experimental data, and the solubility reaching equilibrium of various salts in above systems was calculated, and the experimental results were verified. The research results of this paper lay an important foundation for further theoretical study of multi-temperature phase equilibrium and thermodynamic properties of complex brine system in the later stage. Meanwhile, it provides basic thermodynamic data and theoretical guidance for the rational development and comprehensive utilization of this oil-gas field brine resources.