Coupling Crystallization Process Of Cooling-Solvent Out And Reaction-Extraction For Production Of Potassium Chloride

The potassium is one of the three most essential factors for the grows of crops . The potassium fertilizer can balance nitrogen, phosphorus and other nutrition .so it improves the crops quality and enhances the crops production. Potassium fertilizer is produced mainly by potassium chloride.There are many processes for the production of potassium chloride at home and abroad at present, the research project is one of the national eleventh five-year scientifical supporting and planning projects, named as systematical engineering study of ecological exploitation of KCl and MgCl2·6H2O minerals and focuses on exploitation of potassium minerals, but the former processes are not very suitable because this issue is aiming to achieve ecological extraction of potassium chloride, in view of the actual condition of the Laos potassium-magnesium salt ore, this experiment develops two steps of new crystallization process: cooling-solvent out crystallization and reaction-extraction crystallization, to produce the potassium chloride product meeting industrial standard. Furthermore, a systematic investigation on the crystallization process of potassium chloride, including the crystal morphological analysis, influence of impurities to the crystal shape of potassium chloride, thermodynamics and kinetics of crystallization and crystallization process simulation, were performed in details. And finally an optimized crystallization technology for potassium chloride by this process was presented.Firstly, a new cooling-solvent and reaction-extraction coupling crystallization technology and operation timetable was developed in view of the actual condition of the Laos potassium-magnesium salt ore.Then the morphologic behaviors of potassium chloride, including the crystal microstructure and crystal habit, and the influence of impurities to the crystal shape of potassium chloride were discussed in detail. By single crystal X-ray diffraction, the crystal structure was resolved on the basis of which the influence of impurity ions of sodium, magnesium, calcium etc. to the crystal shape of potassium chloride were discussed.The crystallization thermodynamics of potassium chloride from reaction- extraction crystallization process was studied. The solubilities of potassium chloride and metastable zone at different temperature were measured based on this process.The crystallization kinetics of potassium chloride from reaction-extraction crystallization was analyzed in detail by experiments and model simulation. The crystallization kinetic equations of potassium chloride were established and the correlation parameters of nucleation, growth and agglomeration rate equations were determined. By using the crystallization thermodynamic and kinetic data obtained above, the mathematical model of the reaction-extraction crystallization process of potassium chloride was established based on the population balance and the mass balance equations.The influence to the granularity and yield of the product of cooling-solvent crystallization were studied through changing the speed of temperature decrease, rotate speed and the final temperature in cooling-solvent crystallization; the granularity and purity of the product was also studied by considering the temperature, adding speed of raw material, rotate speed, seeds in reaction-extraction crystallization; in addition, the change of the impurity content of the product of reaction-extraction crystallization is also studied through washing by saturated solution of potassium chloride.