Thermodynamic Properties Of Oilfield Brine Systems Containing Lithium At Multi-trmperatures

There are abundant lithium resources in our country.The effective exploitation and utilization of lithium industry is of great significance to improving the competitiveness of China's lithium industry in the world.Therefore,the thermodynamic properties of water-salt systems are the most important basis for the lithium extraction technology of saline lake.The phase equilibrium of the quarternary system LiCl-NaCl-CaCl2-H2O at 208.15 and 308.15 K,were studied using isothermal dissolution method in this thesis.The solubilites and the physicochemical properties in all studied systems were measured.The dry-salt diagram and water phase diagram of the quaternary systems and the diagrams were plotted.The diagrams of the physicochemical properties versus the solution compositions in all systems were presented.The isopiestic molalities of the systems(LiBr-H20),(SrBr2-H20)and(LiBr-SrBr2-H2O)were measured at 308.15 K by the isopiestic method.The osmotic coefficients and the saturated vapor pressures were calculated for these systems.The osmotic coefficients and saturated vapor pressure against ionic strength diagram of the quaternary systems were plotted.The diagram of quaternary system(LiCl-NaCl-CaCl2-H2O)at 288.15 K,there are two invariant points corresponding to LiCl·H2O+ CaCl2·LiCl·5H2O+NaCl and CaCl2·6H2O+CaCl2·LiCl·5H2O+NaCl,five co-saturated curves,and four co-saturated crystallizing zones corresponding to LiCl·H2O,NaCl,CaCl2·LiCl·5H2O and CaCl2·6H2O.It was found that the physicochemical properties in the metastable equilibrium solution are changed regularly with the increasing of CaCl2 concentration and the distinguished points are exited at the invariant points.The diagram of quaternary system(LiCl-NaCl-CaCl2-H2O)at 288.15 K,there are two invariant points,five co-saturated curves and four co-saturated crystallizing zones.At 288.15 K CaCl2 exist as CaCl2-6H2O while CaCl2 exist as CaCl2-4H2O at 308.15 K.The isopiestic osmotic of the systems(LiBr-H2O),(SrBr2-H2O)and(LiBr-SrBr2-H2O)were measured at 308.15 K by the isopiestic method in the ranges of 0?12.8 mol/kg,0?4 mol/kg and 0.5231?12.1004 mol/kg respectively.It was found that the osmotic coefficients and the saturated vapor pressures are changed regularly with the increasing of ionic strength.