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The solubilities in the quaternary system K+, NH4+//Cl−, SO42--H2O and its two ternary subsystems NH4Cl-KCl-H2O, (NH4)2SO4-K2SO4-H2O at 80.0 °C were measured using the isothermal dissolution equilibrium method under atmospheric pressure, and the corresponding phase diagrams were plotted. In the phase diagram of the NH4Cl-KCl-H2O system, there are three crystalline zones, which correspond to (K1−m,(NH4)m)Cl, ((NH4)n,K1−n)Cl and the co-existence zone of (K1−m,(NH4)m)Cl and ((NH4)n,K1−n)Cl, respectively. In the phase diagram of the (NH4)2SO4-K2SO4-H2O system, there is only one crystalline zone for (K1−t,(NH4)t)2SO4. In the phase diagram of the K+, NH4+//Cl−, SO42--H2O system, there are three crystal zones, which correspond to (K1−t,(NH4)t)2SO4, (K1−m,(NH4)m)Cl and ((NH4)n,K1−n)Cl, respectively. According to the analysis and the calculations for the phase diagrams of the K+, NH4+//Cl−, SO42--H2O system at 80.0 °C and 50.0 °C, this paper proposes a technological process. In the process, the (K1−t,(NH4)t)2SO4 can be prepared at 80.0 °C and the ((NH4)n,K1−n)Cl can crystallize out at 50.0 °C. The mass fraction of K2SO4 in product L1 (K1−t,(NH4)t)2SO4 (t = 0.1465) is 88.48%. The composition of solid solutions in the K+, NH4+//Cl−, SO42--H2O system was experimentally determined and then theoretical calculations about the process can be carried out. [ABSTRACT FROM AUTHOR]

Based on the requirement for the comprehensive exploitation and utilization of the salt lake resources magnesium chloride and potassium chloride, a new technology to produce KCl and ammonium carnallite (NHCl·MgCl·6HO) by using NHCl as salting-out agent to separate carnallite is proposed. The solubilities of quaternary system KCl-MgCl-NHCl-HO were measured by the isothermal method at t = 60.00 °C and the corresponding phase diagram was plotted and analyzed. The analysis of this phase diagram shows that there are seven saturation points and eight regions of crystallization. These eight regions of crystallization represent salts corresponding to KCl, NHCl, MgCl·6HO, (K(NH))Cl, ((NH)K)Cl, (K(NH))Cl·MgCl·6HO, KCl·MgCl·6HO and NHCl·MgCl·6HO. According to the phase diagram analysis and calculations, ammonium carnallite (NHCl·MgCl·6HO) and KCl can be obtained using carnallite as raw materials and ammonium chloride as salting-out agent at t = 60.00 °C. The new technology shows the advantages of being easy to operate and having low energy consumption. The research on this quaternary phase diagram is the foundation for reasonable development of carnallite resources and comprehensive utilization of the salt lake brines. [ABSTRACT FROM AUTHOR]