Research On Crystallization Process Of Potassium Salt By Solvent Extraction

KH₂PO₄ and K₂SO₄ have been widespread used in industrial,agricultural,food and medicine industry.Moreover,they are important products of potassium salt industry.At present,the production method of potassium dihydrogen phosphate mostly is neutralization method and potassium sulfate production by Mannheim method both here and abroad.Solvent extraction method is considered to be very promising because it has the advantages of low energy consumption,mild reaction conditions,and high product purity.However,the technology is not stable and the quality of the products is low by solvent extraction method.Accordingly,we based on the determination of the phase equilibrium data,optimizated crystallization process and laid the foundation for optimizing the process of industry.First,we determined the solid liquid phase equilibrium and physical properties??,p?of quaternary systems K₂SO₄-KCl-H₂SO₄-H₂O and KCl-KH₂PO₄-H₃PO₄-H₂O,and its ternary systems at 298.15K,313.15K.Researched the solid liquid phase equilibrium and physical properties of the ternary systems KCl-KH₂PO₄-H20 in the different concentration?10%,30%,50%?ethanol aqueous mixture solutions.According to the experimdental data,the phase diagrams,solubility curves and physical parameters curves of the systems were plotted.The solubility,density and viscosity of the equilibrium liquid phase were calculated by the empirical formula at 298.15K,313.15K.Crystallization is important step of remove impurities stage,the optimization conditions of cooling crystallization process,explore the impurities and dissolving agent ethanol had important effect on the crystallization of potassium dihydrogen phosphate.In this paper,the preparation of high quality KH₂PO₄ and the effects of various parameters on the crystallization process of KH₂PO₄ were investigated.The optimum technological conditions:the stirring rate was 300 r/min,the cooling rate was 0.25 ?/min,the aging time was 30min,the seed quality was 1.01%,and the crystal mesh number was 100.There are a variety of trace impurities in wet process phosphoric acid,and the impurity ion have great influence on the formation and growth effects of KH₂PO₄ crystal nucleus,therefore,this paper studies the effect of different metal ions in solution doped with ratio,explored the synergistic effects of metal ion on KH₂PO₄ crystal process.The results of this study provided the basic data for the production of KH₂PO₄ and K₂SO₄ by solvent extraction,and provided the basis for the production of high quality KH₂PO₄ and other sylvite.