Soda manufacture process

FIELD: nonferrous metallurgy and inorganic compounds technology.

SUBSTANCE: invention is dealing with processing of carbonate solution produced in complex procedure of nepheline feed into alumina and soda products. Manufacture of soda comprises dissolving double salt in evaporation-concentrated carbonate solution, which is further concentrated to form soda suspension, which is divided, by the aid of hydraulic classification method, into two streams. Each of them is separated into soda and soda mother liquor. Soda mother liquors are combined and treated to separate potassium sulfate. Potassium sulfate mother liquor is concentrated to give double salt suspension. Precipitated double salt is separated. Purity of soda product is 98-98.5%.

EFFECT: increased purity of soda product.

3 dwg

 

The invention relates to ferrous metallurgy, particularly to a method of processing carbonate solution formed by integrated processing of nepheline raw material for alumina and soda products, and can be used in the chemical industry.

There is a method used for processing carbonate solution obtained in the processing of the Kola nepheline concentrate (for example, M. Varlamov, Benkovski SV, Krichevsky EL and other Production of soda and potash by integrated processing of nepheline raw materials. Moscow: Khimiya, 1977, p.82-98), which can be taken as a prototype of the proposed method.

Technological scheme of processing of the carbonate solution by this method by polythermal of parki is shown in figure 1. According to this method, weak carbonate solution is subjected concentrating the residue to the density of the liquid phase 1280-1300 kg/m3without isolating the precipitated salts. One stripped off solution is mixed with the circulating double salt (K2CO3·Na2CO3with the dissolution of the latter, and the resulting solution pariveda on soda residue to the density of the liquid phase 1480-1500 kg/m3with the release of soda solution. Suspension soda is divided into centrifuges. The mother liquor of the soda after clearing the potassium sulfate is supplied to the residue of the double salt, where privae the Xia to achieve the density of the liquid phase 1640-1660 kg/m 3emitting precipitated double salt. Selected precipitated double salt is returned to the beginning of the process where it is mixed with one stripped off carbonate solution, and from the mother liquor of the double salt by cooling to a temperature of 55-60° excels in sediment polutorapolnye potash (K2CO3·1,5H2O).

In accordance with the requirements of GOST 10689-75 "technical Soda ash from nepheline raw materials" main indicators, practically defining the quality of commercial soda are the content of the basic substance (PA2CO3), the content of potassium carbonate (K2CO3and the content of potassium sulfate (K2SO4).

The disadvantages of the method include that it is not possible to get high quality soda and soda always contains a sufficiently large number of particles (sulphate of potash 0,7-1,5% potassium carbonate and 2.1%to 2.6%), which significantly limits the range of applications and markets such soda. Technological scheme of the prototype does not allow stable and guaranteed to produce soda 1st grade (content2CO3not more than 2.3% and the content of K2SO4not more than 1.2%) and even more so to meet the increasing demands of consumers (content2CO3not more than 2.0% and the content of K2SO4not more than 0.5%).

Technical adaca invention is to improve the quality of soda, obtaining stable soda 1st grade in accordance with GOST 10689-75, the increase in the content of the basic substance to 98,0-98,5%.

This object is achieved by a method of producing soda ash from carbonate solution formed by integrated processing of nepheline raw materials, including the dissolution of double salts in one stripped off carbonate solution, evaporation of the resulting solution with formation of a suspension of soda, branches separated sludge ash, the allocation of potassium sulfate of soda of liquor from obtaining liquor of potassium sulfate. Suspension soda by hydraulic classification is divided into two streams, a suspension of each thread independently divided into soda and soda liquor. Soda Queen cells each stream are mixed and served on the selection of potassium sulfate. The mother liquor of the sulfate potassium evaporated to obtain the suspension of the double salt is separated double salt is separated.

The essence of this method stems from the consideration of the solubility chart system Na

+2
2
+2
2
||FROM
2+
3
SO
2-
4
-N2(Figure 2). The solution after dissolution of double salts in pre-one stripped off the solution has a composition corresponding to the figurative point 1 (2K+=46%, SO4=1,2%) charts. As parki solution of soda residue from the solution starts to separate pure soda, the composition of the solution when it is changed by the beam from point 1 to point 2. During crystallization of soda is simultaneously the growth of existing crystals, and the formation of new centers of crystallization. So soda is obtained polydisperse.

In point 2 starts joint crystallization of sodium carbonate and potassium sulfate. The composition of the liquid phase varies along the curve co-crystallization from point 2 to point 3. Released from the solution of sodium carbonate and potassium sulfate crystallize or already existing crystals of pure soda, or form separate crystals. From this it follows that the larger crystals have a lower relative content of potassium sulfate in sodium than small.

The analysis of the diagram of solubility and of the processes occurring during evaporation, it is necessary that the source of sulphate of potash to soda is a joint crystallization with sodium carbonate with viparita the AI solution, as a source of potassium carbonate in the soda is only uterine soda solution (as in the process of evaporation is not achieved field or line of crystallization potassium carbonate or double salt) and potassium carbonate in the soda due to a lack of full, followed by the separation of soda liquor from the soda by centrifugation.

For solving the problem of simultaneous reduction in the ash content of potassium carbonate and potassium sulfate is proposed soda suspension apply for classifying device of any design. This can be hydraulic classifiers with adjustable speed drain or hydrocyclones. As a result of classification suspension soda is divided into two streams. The mode of operation of the classifier is selected depending on the required quality of the resulting ash and may vary widely known techniques. The solid phase of the condensed product (soda-1) is a larger and more homogeneous particle size distribution of the material, which in addition, is that it contains a smaller amount of potassium sulfate, better separated from the liquid phase by centrifugation because of higher porosity (fraction of free volume between the particles in a unit volume of the layer), thereby reducing its content of potassium carbonate. The solid phase of the upper discharge (soda-2) smaller, worse otdelaetsya liquid phase by centrifugation and therefore contains more potassium sulfate and potassium carbonate.

Figure 3 shows the flow chart of processing of the carbonate solution by the claimed method.

Manufacture of soda by the claimed method, implemented in the branch "Pikalevo alumina" JSC "metallurg" from January 2003 showed the following results. Steadily turns out soda 1 St grade the following composition: the content of Na2CO3- 98,0-98.3%of the content To2CO3- 1.3 to 1.7% and the content of K2SO4- 0.2%to 0.5%. Get soda in the 2nd grade has the following composition: content PA2CO3- 94,3-96,7%, the content To2CO3- to 1.8-2.7% and the content of K2SO4- 1,2-3,1%.

The advantage of the proposed method is that it provides a practical opportunity to steadily produce soda with performance significantly better than defined Gosudarstvennom standard, it is possible to vary the performance of the technological scheme depending on the needs of the different varieties of soda.

The method of producing soda ash from carbonate solution formed by integrated processing of nepheline raw materials, including the dissolution of double salts in one stripped off carbonate solution, evaporation of the resulting solution with formation of a suspension of soda, Department of separated sludge ash, the allocation of potassium sulfate of soda of liquor, getting the mother liquor from which lipata potassium, characterized in that the suspension soda by hydraulic classification is divided into two streams, a suspension of each thread independently divided into soda and soda liquor, soda Queen cells each stream are mixed and served on the selection of potassium sulfate, the mother liquor of the sulfate potassium evaporated to obtain the suspension of the double salt is separated double salt is separated.



 

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