Research on the K₂SO₄ Synthesis Process Based on the Nonequilibrium-Phase Diagram of the Na⁺, K⁺//Cl^–, SO₄^2––H₂O System

To optimize the production process of K2SO4, this study employs the equilibrium cosaturated solution boiling evaporation crystallization method to determine the nonequilibrium-phase diagram of the Na+, K+//Cl–, SO42––H2O quaternary system under boiling evaporation conditions. Based on the nonequilibrium-phase diagram and the 25 °C equilibrium-phase diagram of the Na+, K+//Cl–, SO42––H2O system, the traditional two-step method for preparing and separating K2SO4 via the double decomposition reaction of KCl and Na2SO4 is optimized. Process calculations and experimental validations are conducted to evaluate the improvements. In addition to reducing the circulation volume of the mother liquor and the evaporation water volume, thereby lowering energy consumption, the optimized production process also achieved a 26.85% increase in the single-pass yield of the byproduct NaCl.