Method for preparing potassium nitrate and ammonium chloride employing double decomposition reaction

Abstract

A method for preparing potassium nitrate and ammonium chloride employing double decomposition reaction comprises the following steps: dissolving ammonium nitrate and potassium chloride in water according to a defined ratio at 110 DEG C, continuously adding potassium chloride and water, heating while stirring to ensure that potassium nitrate is in supersaturation state, after stopping heating, cooling the solution in a vacuum cooling crystallizer to 36-40 DEG C to separate potassium nitrate crystal, placing the potassium nitrate crystal in a centrifugal machine with a filter cloth lining to obtain coarse potassium nitrate, then washing the potassium nitrate with cold water, drying to obtain the finished potassium nitrate; in addition, adding ammonium nitrate in mother solution I and cleaning solution to adjust solution concentration so that ammonium chloride can reach supersaturation state, using a vacuum concentration device to perform negative pressure evaporation, separating and precipitating ammonium chloride by centrifuging and obtaining a solid ammonium chloride product, wherein, when dissolving ammonium nitrate and potassium chloride, the ratio of ammonium ion to chlorine ion is 1:2 and when using the centrifugal machine to obtain the coarse potassium nitrate, the separated mother solution is another mother solution I sharing the same saturation point of potassium nitrate and ammonium chloride. The solution of feed liquid circular reaction overcomes the defects of the prior art that the price of potassium nitrate used in reaction is high, the resource of potassium nitrate is in short supply and the cost of devices used in ion-exchange method is high, thus being applicable to the production of potassium nitrate.

Description

technical field [0001] The invention relates to a method for producing potassium nitrate and ammonium chloride by metathesis reaction. Background technique [0002] Potassium nitrate is an important inorganic chemical product. Industrial potassium nitrate is mainly used to make black gunpowder, fireworks, matches, glass products and optical glass, etc. Agricultural potassium nitrate is a high-quality compound fertilizer. For a long time, potassium nitrate The market is in short supply and is a product in short supply. Domestic potassium nitrate production methods mainly include: sodium nitrate-potassium chloride conversion method, mixing sodium nitrate and potassium chloride to an appropriate concentration, reacting at 80-90°C, and then evaporating while separating out sodium chloride and separating out Sodium chloride: properly dilute the mother liquor to prevent the precipitation of sodium salt, and then cool to about 5°C to precipitate the product potassium nitrate. Afte...

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Problems solved by technology

Domestic potassium nitrate production methods mainly include: sodium nitrate-potassium chloride conversion method, mixing sodium nitrate and potassium chloride to an appropriate concentration, reacting at 80-90°C, and then evaporating while separating out sodium chloride and separating out Sodium chloride: properly dilute the mother liquor to prevent the precipitation of sodium salt, and then cool to about 5°C to precipitate the product potassium nitrate. After the crude product is centrifugally filtered and washed, potassium nitrate can be obtained. The product can be recrystallized to obtain industrial grade potassium nitrate. Disadvantages The price of sodium nitrate is high and resources are tight, and the use value and economic value of the by-product sodium chloride are low. In addition, due to the accumulation of impurities in the mother liquor, the mother liquor needs to be discharged regularly, which also affects the yield of potassium nitrate.

The ammonium nitrate-potassium chloride conversion method was first successfully developed by the French Auby company. The reaction of ammonium nitrate and potassium chloride produces potassium nitrate and by-product ammonium chloride. After the reaction, the solution is composed of potassium chloride, ammonium nitrate, and potassium nitrate. , ammonium chloride composition, from the analysis of the phase diagram, it can be seen that the isothermal diagram is divided into four phase crystallization regions. When the temperature is lowered, the content of potassium nitrate in the mixed solution is large, and the crystallization region increases. If reasonable process conditions are selected, the temperature can be reduced. Most of the potassium nitrate in the solution is crystallized, and then the ammonium chloride is crystallized by selecting appropriate conditions, so as to achieve the purpose of separating potassium nitrate and ammonium chloride. This method also has the problem of impurity accumulation. The main impurity is potassium chloride. Sodium chloride, but can be crystallized with the by-product ammonium chloride, the existing process is set in an open direct evaporation container, consumes a large amount of steam, the thermal efficiency is very low, the amount of steam directly taken away by the heated steam is large, not Conducive to energy saving and consumption reduction, the output is small, the whole unit operation takes a long time, and the product appearance and content are slightly poor, so recrystallization is necessary to improve product quality

The ion exchange method uses cation exchange resin as the exchange medium, uses ammonium nitrate and potassium chloride as raw materials, and completes the production of potassium nitrate and ammonium chloride through the process of adding potassium and washing potassium. The disadvantage is that the concentration of potassium nitrate in the exchange liquid is low, and the evaporation cost High; the concentration of recovered ammonium chloride is also low, the energy consumption of evaporation is high, and the equipment requirements are relatively high. Titanium, titanium-molybdenum-nickel alloy or other synthetic materials are required, and the cost is high

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