Characteristic And Application Of Non-equilibrium State Salt Forming Region In K⁺、Mg²⁺//Cl^-、SO₄^2--H₂O System

Salt-water system, the prevalence of the metastable phenomenon, the metastable phase diagram significantly deviates from the equilibrium phase diagram. Through studying on the salt-forming characteristics in conditions of high temperatures and strong evaporation intensity, we find that the salt-forming area is different from the metastable phase diagram and the Non-equilibrium diagram. And so we propose the Non-equilibrium salt-forming diagram concept. Which have been successfully applied in Magnesium sulfate production in Egypt and so on. Taking into account that solid-liquid relation exists in the boiling evaporation processes is different from the equilibrium state and the metastable state, so we research K+、Mg2+∥Cl-、SO42--H2O systems in boiling evaporation process, which is close to brine system.In this study, through determining the solid solution and liquid composition changes under the conditions of evaporation boiling temperature at75℃and constant stirring rate we are to define the salt-forming regions of Langbenite (K.2SO4·MgSO4), Sylvite (KC1), Kainite (KCC·MgSO4·3H2O) and Kieserite (Ml). Based on the results, we proposed the use of non-equilibrium phase diagram of salt-type brine water resources development of new ideas. Exploring its feasibility, the brine utilization of the production process is important. The results show that:1. Salt-forming area of non-equilibrium and equilibrium phase diagrams are quite different.(1) experimental samples locate in the Langbenite’s (K2SO4·MgSO4) precipitation area in the equilibrium phase diagram. According to the wet solid-phase method to determine the types precipitation of salt, the anhydrous potassium magnesium sulfate salt precipitates instead of alum. Which show that its salt-forming area expanded to the Langbenite area in the equilibrium phase diagram, and occupied parts of anhydrous salt area. The new region area caculated is1.51times larger than the original area;(2) was measured by XRD, Kieserite precipitated area in equilibrium phase diagram was mainly replaced by Tetrahydrite;(3) the salt-forming area of Kainite expanded to the area of Langbenite、 Kieserite and Sylvite in the equilibrium phase diagram and was3.74times larger than that in equilibrium phase diagram;(4)These salt-forming area in this system in non-equilibrium evaporation and crystallization not only depart from the equilibrium phase diagram, and there is many staggered and overlapped regions. While this may not happened in the equilibrium phase diagram and the metastable phase diagram, which is the special feature of non-equilibrium phase diagram. It also provides guidance for the operation of industrial processes. 2. The bittern was experimented under the boiling evaporation and the results was expressed in K+、 Mg2+//Cl-、SO42-H2O system at75℃in the equilibrium phase diagram. The raw material point locates in the salt-forming area of Kainite. According to the results, using the bittern to produce Kainite and then to produce fertilizer, the new idea have been researched preliminarily which is feasible.