RU2163885C2 - Method of processing soda and potash-containing solution - Google Patents

Abstract

FIELD: nonferrous metallurgy. SUBSTANCE: solution originates from processing of nepheline ores into silica and soda and potash-containing solutions. Soda- potash double salt obtained in soda and potash solution evaporation stage, instead of being returned into the beginning of process, is subjected to conversion by a part of initial soda and potash solution at 95-100 C to precipitate anhydrous sodium carbonate and produce mother conversion solution with density 1.48-1.49 t/cu.m enriched with potassium carbonate and potassium sulfate and characterized by potassium molar index 66-72%. This solution is further diluted with condensate or with part of initial soda and potash solution to reduce density to 1.41-1.42 t/cu.m and simultaneously cooled to 35-40 C, which gives rise to precipitation of potassium chloride. Potassium chloride-free mother solution is then returned into the beginning of process (evaporation stage). EFFECT: improved quality of soda product and reduced consumption of steam. 4 dwg

Description

 The method relates to non-ferrous metallurgy, specifically to the processing of soda ash solution obtained by processing nepheline ore into alumina and soda ash products.

 The closest analogue (prototype) of the proposed method can be considered the method used for processing soda-cultivating solution obtained by processing Kola nepheline concentrate. The molar index of potassium from the sum of alkalis in soda-potash solution is 35-37%. "Production of soda ash and potash in the integrated processing of nepheline raw materials." Authors: Varlamov M.L., Benkovsky S.V., Krachevskaya E.L., Romanchikov I.V. et al. "Chemistry" M.1977 (p. 82-98).

The technological scheme of processing soda-paste solution by this method by polythermal evaporation is shown in FIG. 1. According to this method, the initial soda-potash solution mixed with a reverse double soda-potash salt (Na ₂ CO ₃ · K ₂ CO ₃ ) is subjected to concentrating evaporation to a density of 1.28-1.30 t / m ³ without precipitating salts in the multi-case evaporated battery with a flow rate of 0.3 tons of steam per 1 m ^{3 one} stripped off water. The stripped off solution is then subjected to the second stage of evaporation until the density of the solution reaches 1.49 -1.51 t / m ³ with the precipitation of anhydrous soda in a 3-body evaporated battery with a flow rate of 0.55 t of steam per 1 m ^{3 of} stripped off water. The mother liquor obtained after separation from carbonate soda is subjected to the third stage of evaporation to achieve a solution density of 1.66-1.68 t / m ³ with the precipitation of double soda potash salt (Na ₂ CO ₃ · K ₂ CO ₃ ) in a double-shell evaporator a battery with a flow rate of 0.7 tons of steam per 1 m ^{3 one} stripped off water. The double salt recovered in the precipitate is returned to the beginning of the technological cycle, where it is mixed with the initial soda-liquor solution at the stage of its concentration evaporation.

From the mother liquor of the double salt by vacuum evaporation and cooling to 55-60 ^o C precipitate potato sesame (K ₂ CO ₃ · 1,5H ₂ O).

 The aim of the proposed method is to improve the quality of the obtained commercial soda due to its purification from potassium sulfate and to reduce the consumption of steam in the technological cycle by reducing the specific flow of solutions and the amount of evaporated water at the stages of soda and double salt extraction.

This goal is achieved by the fact that, instead of returning to the beginning of the technological cycle, the double salt is subjected to conversion with a portion of the initial soda-liquor solution, carbonate soda is precipitated and a mother liquor is enriched in potash and potassium sulfate, from which it is then diluted to a density of 1.40-1 , 42 t / m ³ and cooling to 35-40 ^o C produce precipitate in the form of an independent product salable potassium sulfate (K ₂ SO ₄ ).

The technological scheme of the new method proposed for the processing of soda-paste solution by polythermal evaporation is shown in FIG. 2. According to this method, the double salt is subjected to conversion at a temperature of 95-100 ^o C part of the original soda-paste solution, dosed based on obtaining (after the conversion of the double salt and subsequent precipitation of anhydrous soda) mother liquor with a density of 1.48-1.49 t / m ³ and a molar index of potassium of the total alkali in solution of 66-72%. Potassium sulfate is separated from the mother liquor of the conversion of the double salt after it has been diluted with condensate or the original soda mixture to a density of 1.41-1.42 t / m ³ and cooled to t 35-40 ^o C. And after separation of the precipitate of potassium sulfate, the mother liquor of potassium sulfate is mixed with the main part of the initial soda-liquor solution and subjected to concentrating evaporation until a solution density of 1.40 t / m ^{3 is} reached. One stripped off solution is then subjected to the second stage of evaporation until a solution density of 1.49-1.50 t / m ^{3 is} reached with the precipitation of anhydrous soda with a low content of sulfate salts in it. The mother liquor after separation of anhydrous soda from it is subjected to the third stage of evaporation until a solution density of 1.66-1.68 t / m ^{3 is} reached with the precipitation of a double salt (Na ₂ CO ₃ · K ₂ CO ₃ ). From the mother liquor after separation from the double salt, one-and-a-half potash (K ₂ CO ₃ · 1.5 H ₂ O) is isolated by vacuum evaporation and cooling of the solution to 55-60 ^o C. And the filtered double salt is subjected to conversion, as described above, at t = 95-100 ^o With a part of the initial soda-liquor solution, dosed on the basis of obtaining after conversion of the double salt of the mother liquor with a density of 1.48-1.49 t / m ³ and a molar index of potassium of the total alkali in the solution of 66-72% with allocation in precipitate of anhydrous soda.

To compare the obtained technological parameters of the process, achieved by processing soda-potting solution with new and known methods, in FIG. Figures 3 and 4 give examples of the practical implementation of the processing process using new and known methods of 140 m ³ / h of soda-seed solution obtained by processing Kola nepheline concentrate.

 It follows from them that when the soda-potash solution is processed in a new way, in comparison with the known method, due to the conversion of the double salt and the exclusion of its turnover at the beginning of the technological cycle, as well as due to the removal of potassium sulfate from the mother liquor of the conversion, all production anhydrous soda will be produced first grade instead of soda of the second grade, obtained by the known method. Potassium sulfate is removed from the technological cycle as an independent commercial product, the specific flows of solutions and the amount of evaporated water at the stages of soda and double salt extraction are reduced by 25-30%. The main amount of water is removed from the technological cycle at the stage of concentrating evaporation of the initial soda-liquor solution in multi-case evaporated batteries with a low specific steam consumption. Due to this, the total steam consumption in the technological cycle in comparison with the known method is reduced by 10%.

Claims (1)

A method of processing soda-potash solution, including polythermal evaporation of soda-potash solution in evaporation batteries with the release of anhydrous soda, double soda-potash and potash separated from evaporated mother liquors, characterized in that the double soda-potash salt is subjected to conversion with a portion of the original soda-potash solution at 95-100 ^o C, precipitated with release of anhydrous sodium carbonate and the conversion yield of the mother liquor density 1.48 - 1.49 t / m ³ enriched potassium sulfate and potassium carbonate, with a molar potassium index of the amount of alkali solution in 66 - 72%, followed by dilution of the stock solution or the condensation part of the original soda and potash solution to a density of 1.41 - 1.42 t / m ³ and cooling the dilute solution to 35 - 40 ^o C with the release of a sulphate precipitate potassium.

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