Solid–Liquid Phase Equilibria of Quaternary System LiBr–NaBr–KBr–H2O and Its Subsystems at 348.15 K

In view of the composition characteristics of lithium, calcium, and bromine rich in Nanyishan oilfield water of the Qaidam Basin, Qinghai Province, the phase equilibrium relationships of quaternary system LiBr–NaBr–KBr–H2O and its ternary subsystems LiBr–NaBr–H2O and LiBr–KBr–H2O at 348.15 K were studied by the isothermal solution equilibrium method, and the equilibrium solid-phase crystallization regions and composition of each invariant point in each system were determined. The results show that there is no complex salt or solid solution in ternary systems LiBr–NaBr–H2O and LiBr–KBr–H2O at 348.15 K, and the phase diagram contains only one invariant point, two isothermal univariate curves, and two equilibrium solid-phase crystallization regions. The quaternary system LiBr–NaBr–KBr–H2O also has no formation of complex salt or solid solution, and the phase diagram contains only one invariant point, three isothermal univariate curves, and three equilibrium solid-phase crystallization regions. Meanwhile, the phase equilibrium relationships and change laws of each component of the above-mentioned systems at different temperatures were compared and discussed.