Method for preparing sodium nitrate through solvent extraction

Abstract

The invention provides a method for preparing sodium nitrate through solvent extraction. The method includes the following steps that step1, a potassium chloride saturated solution with the temperature of 50 DEG C-70 DEG C is prepared, nitric acid is added to react with the potassium chloride saturated solution at the temperature of 50 DEG C-70 DEG C, cooling crystallization and solid-liquid separation are performed, and an obtained solid phase is washed with water and dried to obtain a potassium nitrate product; step2, an extraction agent is added into a liquid phase obtained in solid-liquid separation in the step1, and a raffinate water phase is returned into a reaction vessel in the step1; 3, an organic phase obtained in extraction in the step2 is mixed with water or a second mother solution, ammonia gas is led into the mixture for reverse extraction, and a reverse extraction organic phase is returned to the step2; 4, condensation crystallization and solid-liquid separation are performed on a reverse extraction water phase in the step3 to obtain ammonium chloride and a first mother solution, potassium chloride is added into the first mother solution and reacts with the first mother solution at the temperature of 60 DEG C-80 DEG C, cooling crystallization and solid-liquid separation are performed to obtain a solid phase and the second mother solution, the obtained solid phase is washed and dried to obtain a potassium nitrate product, and the second mother solution is returned to the step3.

Description

technical field [0001] The invention belongs to the field of agricultural fertilizer production, in particular to a method for preparing potassium nitrate by solvent extraction. Background technique [0002] Potassium nitrate is a chlorine-free high-grade nitrogen and potassium binary compound fertilizer. Its total nutrient content is as high as 60wt%. It is universally applicable and non-volatile. After application, it can be completely absorbed by plants and soil without being brought Chemical residues, which can effectively improve the quality and yield of plants, are called "true green fertilizers". There are many production methods of potassium nitrate, currently the main methods used in industry are: sodium nitrate-potassium chloride conversion method, ammonium nitrate-potassium chloride double decomposition method, ion exchange method, nitric acid and potassium chloride preparation method. [0003] Wang Guiyun etc. have reported a method for preparing agricultural po...

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Problems solved by technology

This method has the following disadvantages: (1) high energy consumption: the reaction temperature is controlled at about 5°C, and a large amount of refrigeration energy consumption is required in the production process, resulting in high production costs; (2) HCl and HNO cannot be effectively separated 3 , the extraction and separation operation is complex and cumbersome: due to the mutual solubility between isoamyl alcohol and TBP and water, there will be the phenomenon that TBP contains isoamyl alcohol and isoamyl alcohol contains TBP, resulting in unsatisfactory extraction effect and separation process. Complex, separation of HCl and HNO 3 The process of the process has become the main part of the whole potassium nitrate production process, and the separation cost is high; (3) the consumption of extractant is large: the method adopts isoamyl alcohol to extract HCl, and the distribution coefficient of HCl in isoamyl alcohol and water is about 0.058~0.57, That is, isoamyl alcohol has a better selectivity to HCl when the HCl concentration is higher, but usually the HCl concentration in the potassium nitrate crystallization mother liquor is not high, so the extraction rate of isoamyl alcohol to hydrochloric acid is low, and isoamyl alcohol is in water. Solubility is bigger, and part isoamyl alcohol is dissolved in aqueous phase and causes loss during extraction, therefore, to reach certain extraction effect, the consumption of isoamyl alcohol is big, causes production cost height; (4) the concentration of by-product hydrochloric acid is very low , is 7.5% to 8.5%, and contains impurity HNO 3 , although the hydrochloric acid with a concentration of about 20% can be obtained through further concentration, the concentrated hydrochloric acid still cannot be sold as a product, and the concentration operation needs to consume a large amount of energy, and there is also the problem of high energy consumption. The by-product hydrochloric acid contains HNO 3 also caused raw material NO 3 - waste of

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