RU2305658C2 - Method of processing low-potassium soda potash solution at high content of sulfur - Google Patents

Abstract

FIELD: processing of low-potassium soda potash solutions contaminated with considerable amount of sulfate salts.

SUBSTANCE: proposed method includes preliminary concentrating evaporation of starting soda potash solution followed by evaporation till saturation with sulfate salts at precipitation of pure monohydrated soda, separation of commercial potassium sulfate from mother liquor of monohydrated soda by mixing it with mother liquor of anhydrous soda and cooling to temperature of 35-40C, separation of anhydrous soda with admixtures from mother liquor of potassium sulfate and re-crystallization of it into pure monohydrated soda. Sulfur is withdrawn from process by hydro-chemical re-crystallization of part of commercial potassium sulfate in two stages in succession. At first stage, glaserite salt (Na₂SO₄·3K₂SO₄) settles-out due to re-crystallization of commercial potassium sulfate in circulating mother liquor obtained at second stage during re-crystallization of glaserite salt. At second stage, berkeyite salt (Na₂CO₃·2Na₂SO₄) due to re-crystallization of glaserite salt in newly prepared saturated solution of pure monohydrated soda proportioned for obtaining circulating mother liquor after re-crystallization of glaserite salt at molar potassium index not exceeding 17%.

EFFECT: possibility of complex processing of soda potash solutions contaminated with considerable amount of sulfate salts.

1 dwg

Description

A method of processing a low potassium soda paste solution relates to non-ferrous metallurgy, specifically to processing a low potassium soda paste solution contaminated with a large amount of sulfate salts.

There is a method of processing low potassium soda paste solution according to the invention patent No. 2223913 of July 15, 2002. According to this method, a low-potassium soda paste solution was subjected to preconcentrating evaporation to a predetermined design density, then the solution was subjected to the second evaporation stage until the solution was saturated with sulfate salts, and pure monohydrate soda was precipitated: potassium sulfate was further separated from the mother liquor of monohydrate soda by mixing it with the mother solution anhydrous soda and a dosage in a mixed solution of the estimated amount of sodium sulfate or sulfuric acid to remove excess the amount of potassium alkali in the form of marketable potassium sulfate. From the mother liquor, after purification from potassium sulfate, dirty anhydrous soda was precipitated, subjecting the solution to the third stage of evaporation. The dirty anhydrous soda precipitated was purified from impurities of potassium sulfate and potash by recrystallizing it into monohydrate soda in the initial soda-potash solution after concentrating it.

However, this known known method is not suitable for processing a low potassium soda solution contaminated with a large amount of sulfate salts if their content in the technological cycle exceeds the content of potassium alkali in it, since the excess sulfur will be removed from the process in the form of sodium sulfate in a mixture with potassium sulfate .

The objective of the invention is to develop a new method that enables the integrated processing of low potassium soda paste solution contaminated with a large amount of sulfate salts, while obtaining high-quality commercial soda and potassium sulfate, with the release of excess sulfur from the process cycle separately in the form of birchite salt (Na ₂ CO ₂ · 2Na ₂ SO ₄ ).

This goal is achieved by the fact that in the known method of processing low-potassium soda-potash solution, including concentrating evaporation of the original soda-potash solution, its subsequent evaporation with the release of pure monohydrate carbonate soda in the precipitate, the allocation of potassium sulfate monohydrate soda from the mother liquor by mixing it with anhydrous carbonate mother liquor soda, separation of dirty anhydrous soda from a potassium sulfate mother liquor and recrystallization of dirty anhydrous soda to pure mon ogidratnuyu soda Original soda and potash solution is concentrated residue excess of sulfur contained in the original soda and potash solution above contained potassium alkali removed from the process as a separate berkeitovoy salt (Na ₂ CO ₃ · 2Na ₂ SO ₄₎ by hydro-chemical recrystallization part commodity potassium sulfate the calculated amount of a saturated solution of soda monohydrate sequentially in two steps, wherein in the first step is isolated in glazeritovuyu salt precipitate (Na ₂ SO ₄ · 3 K ₂ SO ₄₎ recrystallization of potassium sulphate in about otnom mother liquor obtained in the second step the recrystallization glazeritovoy salts, and in the second stage is isolated precipitate berkeitovuyu salt (Na ₂ CO ₃ · 2Na ₂ SO ₄₎ by recrystallization glazeritovoy salt in a newly prepared saturated pure monohydrate soda solution is metered at the rate of receipt of after recrystallization of the glaserite salt of the reverse mother liquor with a molar index of potassium of not more than 17%.

The processing of soda-liquor solution containing an excess of sulfur with unsecured potassium alkali is carried out in the following sequence.

The original soda-paste solution is subjected to a concentrated evaporation until the evaporated solution is saturated with alkaline carbonate salts. Next, the solution is subjected to the second stage of evaporation until the evaporated solution is saturated with sulfate salts, and pure monohydrate carbonate soda is precipitated. The mother liquor purified from monohydrate soda is mixed with the reverse mother liquor of anhydrous soda obtained in the subsequent processing stage of the soda-liquor solution. The solutions are mixed in the calculated ratio to obtain a mixed solution with a molar index of potassium in the range of 52-53%. The mixed solution is subjected to cooling to t 35-40 ° C with the release of precipitated commodity potassium sulfate. The mother liquor, purified from potassium sulfate, is then subjected to the third stage of evaporation until the evaporated solution is saturated with sulfate salts, and anhydrous carbonate soda precipitated in the sediment contaminated with potassium alkali and sulfate salts. Filtered in centrifuges anhydrous carbonate soda is purified from impurities of carbonate and sulfate potassium alkali by its hydrochemical recrystallization in the initial soda-paste solution, dosed in the ratio W: T = 1.5: 1, with the release of pure monohydrate soda. The mother liquor obtained after recrystallization of anhydrous soda is mixed with the main stream of the original soda-liquor solution before separation of pure monohydrate soda from it at the beginning of the technological cycle.

To remove from the process cycle an excess of sulfur unsecured with potassium alkali in the form of an independent berkeitic salt (Na ₂ CO ₃ · 2Na ₂ SO ₄ ), a part of the calculated amount of potassium sulfate is subjected to hydrochemical recrystallization in successive two stages with a specially prepared calculated amount of saturated solution of pure monohydrate soda.

In this case, at the first stage, a glaserite salt (Na ₂ SO ₄ · 3K ₂ SO ₄ ) is precipitated by recrystallization of potassium sulfate in the reverse mother liquor obtained in the second stage upon recrystallization of the glaserite salt. In the second stage, a berkeitic salt (Na ₂ CO ₃ · 2Na ₂ SO ₄ ) is precipitated by hydrochemical recrystallization of the glaserite salt obtained in the first stage in a newly prepared saturated solution from the initial monohydrate soda, dosed in the process based on the calculation of the preparation of the glaserite salt of the reverse mother liquor after recrystallization a solution with a molar index of potassium alkali of not more than 17%. The mother liquor obtained in the first stage after recrystallization of potassium sulfate with potassium alkali extracted into the solution is returned to the technological cycle of processing the soda-liquor solution to the stage of separation of anhydrous soda.

If in this method the molar index of potassium alkali in the mother liquor obtained at the stage of recrystallization of the glaserite salt exceeds 17%, the secreted berkeite salt will be contaminated with the remainder of the glaserite salt. If the molar index of potassium alkali in the mother liquor at the stage of isolation of the berkeitic salt is below 17%, the specific flow of the reverse mother liquor in the technological cycle of soda production increases.

An example of the practical implementation of the method of separation of berkeitic salt according to the proposed method with the expected balance of material flow in the production cycle is shown in figure 1.

Claims (1)

A method for the complex processing of low potassium soda-potash solution with a high sulfur content, including preconcentrating evaporation of the initial soda-potash solution, its subsequent evaporation to saturation with sulfate salts, precipitation of pure monohydrate soda, precipitation of potassium sulfate from the resulting mother liquor of monohydrate soda by mixing it with the mother liquor of monohydrate soda anhydrous soda and cooling it to a temperature of 35-40 ° C, the allocation from the mother liquor of potassium sulfate anhydrous soda with RIMES and its recrystallisation in pure monohydrate soda, characterized in that the sulfur contained in the starting nizkokaliynom soda and potash solution is withdrawn from the process through hydrochemical recrystallization part commodity potassium sulfate successively in two stages, wherein in the first stage the precipitate is isolated glazeritovuyu salt (Na ₂ SO ₄ · 3K ₂ SO ₄ ) by recrystallization of marketable potassium sulfate in the mother liquor obtained in the second stage by recrystallization of glaserite salt, and in the second stage precipitate Berkeitic salt (Na ₂ CO ₃ · 2Na ₂ SO ₄ ) by recrystallization of the glaserite salt in a newly prepared saturated solution of pure monohydrate soda, dosed based on the preparation of a reverse mother liquor with a molar potassium index of not more than 17% after recrystallization of the glaserite salt.