Method for preparing industrial potassium nitrate by virtue of recrystallization method

Abstract

The invention discloses a method for preparing industrial potassium nitrate from a potassium nitrate crude product by virtue of the recrystallization method, and relates to the technical field of inorganic chemical industry. A 2 to 5-stage continuous crystallization manner is adopted, and a crystallization device is formed by connecting a flash evaporator and liquid phases of 2 to 5 crystallizers in series, wherein the temperature of a potassium nitrate crude product solution is 70 to 78 DEG C, and the saturation of the potassium nitrate crude product solution is 90 to 91 percent; the temperature of a flash evaporator solution is 59 to 67 DEG C, the corresponding flash steam temperature is 54 to 61 DEG C, and the flash steam pressure is 112 to 156 mm Hg; the temperature of a liquid phase outlet of the final crystallizer is 17 to 19 DEG C, the corresponding flash steam temperature is 16 to 18 DEG C, and the flash steam pressure is 14 to 15 mm Hg; the flash steam rate is 22 to 27 percent, and the potassium nitrate crystallization rate is 79 to 84 percent. The industrial potassium nitrate state standard GB 1918-2011 is executed to produce high-class and first-class industrial potassium nitrate.

Description

Technical field [0001] The invention relates to the technical field of inorganic chemical industry, and relates to a method for preparing industrial potassium nitrate by a recrystallization method. Background technique [0002] Industrial potassium nitrate has a wide range of industrial uses. Used in the manufacture of fireworks, black gunpowder, matches, and medicines, as catalysts, ceramic glazes, and glass clarifiers. In recent years, with the development of regenerative solar energy utilization, potassium nitrate is used as a raw material for heat carrier high-temperature molten salt, and the demand continues. Increase. [0003] (1) In "Purification of Agricultural Potassium Nitrate to Produce Industrial Potassium Nitrate" (Zhang Gang et al. Fertilizer Design, Volume 41, No. 4, 2003.08), agricultural potassium nitrate was used as raw material, after dissolution, impurity removal and filtration, natural cooling , centrifugation, dehydration and drying, etc., to obtain i...

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Problems solved by technology

[0003] (1) In "Purification of Agricultural Potassium Nitrate to Produce Industrial Potassium Nitrate" (Zhang Gang et al. Fertilizer Design, Volume 41, No. 4, 2003.08), agricultural potassium nitrate was used as raw material, after dissolution, impurity removal and filtration, natural cooling , centrifugation, dehydration and drying, etc., to obtain industrial products, the disadvantage is that it does not involve the multi-stage crystallization method of the present invention

[0004] (2) In "New Process for Production of Industrial Potassium Nitrate by Cooling and Crystallization" (Zhang Gang et al. Hunan Chemical Industry, Volume 32, No. 45, 2005.10), a spiral plate heat exchanger is used for potassium nitrate crystallization to cool and produce industrial potassium nitrate, It has the advantages of no fouling, high heat transfer coefficient, low energy consumption, large production capacity, small equipment volume, convenient operation, etc. The disadvantage is that it does not involve the multi-stage crystallization method of the present invention

[0005] (3) In "Technology Research on Production of High-purity Potassium Nitrate by Ion Exchange Method" (Pan Mingwang et al. Hebei Chemical Industry, No. 2, 2000), ammonium nitrate and potassium chloride were used as raw materials to produce high-purity nitric acid by ion exchange method The technique of potassium is easy to operate and good in stability, but the disadvantage is that it does not involve the multistage crystallization method of the present invention

[0006] (4) In the "Production Technology Development of Potassium Nitrate by Potassium Chloride-Ammonium Nitrate Double Decomposition" (Chen Mingliang et al. Chemical Fertilizer Industry, Volume 26, No. 6, 1999), potassium nitrate and chloride were determined by phase diagram and experiment The crystallization condition of ammonium, when potassium nitrate crystallization temperature is 0 ℃, crystallization rate > 60%, when ammonium chloride crystallization temperature is 60 ℃, crystallization rate > 60%, insufficient is not related to the multistage crystallization method of the present invention

[0007] (5) In "The Effect of Temperature on the Production Process of Potassium Nitrate by Metathesis Method (Zhao Qiwen. Salt Lake Research, Volume 9, No. 3, 2001.09), in the process of making potassium nitrate by double decomposition method using ammonium nitrate and potassium chloride as raw materials, The crystallization temperature of ammonium chloride is not lower than 60°C, and the crystallization temperature of potassium nitrate is generally 20°C to 25°C, which can be considered to be raised to 30°C to 40°C. The disadvantage is that it does not involve the multi-stage crystallization method of the present invention

[0018] ③The operating temperature control range of the crystallizer is different

Multi-stage crystallization is a well-known technology, and it is difficult to express the characteristics of multi-stage crystallization systems only by proposing the range of series and certain stage parameters

The 2-5 stage multi-stage crystallization system proposed by the present invention respectively proposes 2, 3, 4, and 5-stage continuous crystallization parameters, and the system characteristics of multi-stage crystallization, such as crystallizer volume, crystallizer internal circulation, etc. The change is obvious; while the comparative patent has no corresponding grading parameters and multi-level features

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