Molten salt production method for co-producing high-purity magnesium hydroxide, magnesium carbonate and nitrogen-potassium fertilizer

Abstract

The invention discloses a molten salt production method for co-producing high-purity magnesium hydroxide, magnesium carbonate and a nitrogen-potassium fertilizer, and relates to the technical field ofchemical product production. The method comprises the following steps: refining magnesium nitrate, adding ammonia water for reacting to obtain a magnesium hydroxide product, reacting a mother solution with ammonium carbonate, performing precipitating to obtain a basic magnesium carbonate product, reacting the mother solution with potassium chloride to obtain crude potassium nitrate, performing refining to obtain molten-salt-grade potassium nitrate, and finally concentrating and crystallizing the mother solution to obtain the nitrogen-potassium fertilizer. The method disclosed by the inventionhas the beneficial effects that a co-production process and a magnesium hydroxide production process supplement each other, existing resources are utilized at the maximum efficiency to obtain the maximum yield, the waste of raw materials is reduced, the commodity additional value is improved, the process raw material utilization rate is high, the product purity is high, and the economic benefit is considerable.

Description

technical field [0001] The invention specifically relates to the technical field of chemical product production, in particular to a molten salt production method for co-producing high-purity magnesium hydroxide, magnesium carbonate and nitrogen and potassium fertilizers. Background technique [0002] At present, the by-products of producing molten salt grade potassium nitrate at home and abroad are basically magnesium chloride and ammonium chloride. The production process is simple, the chloride ion in the product cannot be eradicated, and the purity of the obtained magnesium hydroxide product is not high, resulting in low added value of the product. There is an urgent need for a co-production process that is matched with the production of high-end magnesium hydroxide and high-purity magnesium carbonate from the by-product of molten salt grade potassium nitrate. There is also a domestic patent application (patent number CN109721082A) that proposes a production plan that is ...

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Problems solved by technology

There is also a domestic patent application (patent number CN109721082A) that proposes a production plan that is similar to this patent, but lacks scientific basis. For example, the patent proposes to use solid magnesium oxide to react with 96% concentrated nitric acid to produce magnesium nitrate products, and through filtration, This is unreasonable, concentrated nitric acid reacts with solid magnesium oxide, due to the violent reaction, the temperature is too high, on the one hand, the reaction product is basically solid, so there is no theory of filtration, on the other hand, the temperature exceeds the decomposition temperature of nitric acid. A large amount of nitrogen oxide poisonous and harmful gas will be produced during the reaction

Moreover, the patent only undergoes the step of magnesium precipitation by reacting with ammonia water to form magnesium hydroxide precipitation. Due to the interference of ammonium ions, usually only 80-90% of magnesium ions can be removed, while molten salt grade potassium nitrate requires a purity of 99.8%. Above, the content of magnesium ions must be less than 0.001%, and the content of chloride ions must be less than 0.01%. This patent only removes 80-90% of magnesium ions, and the purity and magnesium ion content of potassium nitrate produced in subsequent steps are difficult to meet the requirements. Require

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