Separation and recovery of potassium chloride from sintering filtrated dust of ferrous metallurgy by solvent crystallization and the phase equilibrium of quaternary solution system

Solvent displacement crystallization provides an energy-efficient alternative to evaporative crystallization potentially and has the advantage of obtaining superior quality products. In this work, the solvent crystallization was used to extract KCl from sintering filtrated dust of ferrous metallurgy. The purity and total recovery efficiency of KCl reached 93.8% and 75.8%, respectively, under the optimal conditions. The equilibrium properties of KCl and NaCl in the KCl-NaCl-H2O-C2H5OH quaternary system were investigated and discussed. A pyramid phase diagram of the quaternary system was established to illustrate the phase equilibrium of the KCl recovery solvent crystallization process. The minimum (critical) amount of organic solvent and the critical crystallization composition of the saturated system were determined by the diagram. The novel diagram is of both practical value and scientific importance of guiding the process design and operation for organic solvent crystallization.