RU2259947C2 - Method of dehydrating solutions of calcium or magnesium chloride - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method comprises dehydrating solutions of calcium chloride or magnesium chloride in fluidized bed apparatus by spraying the solution in the layer through nozzles with control of granulometric composition of the dehydrated product by means of control of the spraying intensity, separating a portion of the finishing product and its processing by means of initial solution to produce suspension. In order to processing the portion of the finishing product, the initial solution is used that is composed of admixture that is difficulty soluble in the concentrated solution of the finishing product, the suspension produced is separated to extract nonsoluble admixtures, and the solution is directed to the dehydration in the fluidized bed apparatus. In order to processing a portion of the finishing product, the initial solution is used that is composed of such compositions as sodium chloride, potassium chloride, calcium sulfate , and calcium or magnesium hydroxy acid.

EFFECT: simplified process.

2 cl, 2 tbl, 2 ex

Description

The invention relates to techniques for the dehydration of solutions of calcium chloride or magnesium chloride.

A known method of dehydration of solutions of magnesium chloride in a fluidized bed apparatus by spraying a solution in a fluidized bed through nozzles, followed by processing the dehydrated product with a neutral or acidified magnesium chloride initial solution, taken in an amount that ensures the content of magnesium chloride in the target product is not less than 50% (see RF patent No. 2140872, class C 01 F 5/34, publ. 10.11.99, bull. No. 31).

The known method allows to obtain a conditioned product from an initial solution with a content of 32.0-33.9% MgCl ₂ , from which alkali metal chlorides (NaCl, KCl) are pre-isolated, for example, by evaporation.

A known method of dehydration of solutions of calcium chloride or magnesium chloride in a single-chamber apparatus of a fluidized bed by spraying the source solution through nozzles with the regulation of the particle size distribution of the dehydrated product by the degree of spraying, separating the target product and processing the finely divided classes of the target product with the initial solution to obtain a suspension that is sprayed in the layer through the nozzles (see RF patent No. 2181693, class C 01 F 5/34, 11/44, publ. 04/27/2002, bull. No. 12 - prototype).

The known method allows to obtain conditioned products from stock solutions, from which impurities of sodium chloride and (or) potassium chloride, calcium sulfate, etc. are previously separated by evaporation of the stock solution.

The task of the invention is to obtain a dehydrated granular product from the initial solution without pre-evaporation to isolate impurities.

The problem is solved in that, in contrast to the known method, including dehydration of solutions of calcium chloride or magnesium chloride in a fluidized bed apparatus by spraying the solution in the layer through nozzles with regulation of the particle size distribution of the dehydrated product by the degree of atomization, separation of the product and its processing with the initial solution to obtain suspensions, according to the proposed method for processing take solutions containing impurities, sparingly soluble in concentrated solutions of the target product, gender the studied suspension is separated with the release of insoluble impurities, and the solution is sent to dehydration in a fluidized bed apparatus.

For processing take solutions containing impurities such compounds as sodium chloride, potassium chloride, calcium sulfate, calcium hydroxide (magnesium), etc. In this case, part of the product is taken in an amount that provides concentrated solutions of calcium chloride or magnesium chloride, and mainly use finely divided fractions of the target product.

The essence of the method is as follows. In contrast to the known method, part of the target product is treated with initial solutions containing impurities that are hardly soluble in concentrated solutions of calcium chloride or magnesium chloride.

As a rule, to obtain calcium chloride or magnesium chloride, natural brines, by-products or effluents from industries, for example, synthetic carnallite, soda (white seas), or natural ores (sylvinite-carnallite) are used. The resulting solutions contain sodium chloride, potassium chloride, calcium sulfate, calcium hydroxide (magnesium) as impurities. Before the production of the target product, these solutions are subjected to multi-stage evaporation and other technological operations for cleaning solutions of these impurities (see, for example, M.E. Pozin. Technology of mineral salts, vol. 1. Chemistry, 1970, pp. 272-278 and .743-746). For final processing, as a rule, solutions with a basic substance content of 25-30% are supplied.

Our studies have shown that the task of cleaning solutions of calcium chloride or magnesium chloride can be solved by treating part of the dehydrated product with solutions. The product, dissolving in the initial solution, salifies the impurities of salts from solutions with the formation of a suspension. The reaction of dissolving and salting out the salts is exothermic and the resulting suspension is self-heating. The flow rate of the dehydrated product fed to the treatment of the initial solution depends on the content of calcium chloride or magnesium chloride in the initial solution and the final processing temperature. As a rule, the concentration of the final solution should be close to saturation in the target component (the saturation coefficient is 0.95-0.98). Tables 1 and 2 show the solubility of impurities in the presence of calcium chloride or magnesium chloride at various temperatures depending on the concentration of the target product, indicating the type of solid phase formed as a result of processing part of the target product with the initial solution. The chemical composition of the solid phase varies widely and depends only on the type of feedstock.

Table 1
Solubility of sodium chloride and potassium chloride in the presence of calcium chloride Temperature,
° C Mass fraction in the liquid phase,% The composition of the solid phase Kcl NaCl CaCl ₂ 25 12.60 3.62 10.69 1,2 3.98 5.08 25,50 1,2 0.34 3.08 44.38 1,2,3 fifty 7.70 9.95 16,48 1,2 3.40 6.00 28.15 1,2 0.75 4.73 41.84 1,2 0.48 4.03 55.02 1,2,4 100 10.30 16.15 13.07 1,2 4.80 11.01 27.60 1,2 3.43 9.58 30.31 1,2 1,07 2.81 59.68 1,2,4

Notes:

1. Symbols: 1 - NaCl, 2 - KCl, 3 - CaCl ₂ · 6Н ₂ О, 4 - CaCl ₂ · 2H ₂ O.

2. The solubility of Ca (OH) ₂ and Mg (OH) ₂ in solution at 50 ° C at various concentrations of calcium chloride is 0.07-0.61%.

table 2
Solubility of sodium chloride and potassium chloride in the presence of magnesium chloride Temperature ° C Mass fraction in the liquid phase,% The composition of the solid phase NaCl Kcl MgCl ₂ 10 12.57 6.59 9.50 1,2 5.42 4.73 18.59 1,2 1.92 2.67 25.43 1,2,3 1.09 0.57 29.66 1.3 0.68 2.63 26.08 2,3 0.27 0,07 34.78 1,3,4 twenty 13.85 8.33 7.60 1,2 1.88 3.23 25.44 1,2,3 1.42 1.29 28.30 1.3 0.35 0.08 35.22 1,3,4 40 12.82 10.34 8.49 1,2 1.88 4.06 26,42 1,2,3 1,61 3.99 26.94 2,3 0.43 0.20 35.84 1.3 60 1.96 4.95 27.30 1,2,3 0.34 0.27 37.37 1,3,4 100 7.01 12.85 16,48 1,2 2.00 6.40 30.11 1,2,3 0.46 0.49 41.90 1.3,4

Notes:

1. Legend: 1 - NaCl, 2 - KCl, 3 - KCl · MgCl ₂ · 6H ₂ O, 4 - MgCl ₂ · 6H ₂ O.

2. The solubility of CaSO ₄ in dilute solutions of magnesium chloride of the carnallite factory 0.7-0.9%, in concentrated 0.3-0.5%.

From the above data it is seen that in order to obtain conditioned products, it is sufficient to raise the final concentration of the initial solution for calcium chloride to 50%, and for magnesium chloride to 35% as a result of processing part of the target product with this solution.

The suspension obtained by processing part of the target product with an initial solution is subjected to separation in a known manner (thickening, hydroclassification, filtration) to obtain a solution that is sprayed in a layer of a fluidized bed apparatus through nozzles to control the particle size distribution of the dehydrated product. The target product is classified. Non-target fractions and cyclone dust are used for treatment with the initial solution, however, part of the target fractions can also be used for processing.

The solid phase isolated from the suspension is used as an anti-icing preparation in the main production, or it is treated with the initial solution to increase the extraction of the target product and discarded.

The method is as follows. The initial solutions of calcium chloride or magnesium chloride, containing impurities insoluble in concentrated solutions of the target product, are dehydrated in a fluidized bed apparatus by spraying the solution in the layer through nozzles with control of the particle size distribution of the dehydrated product by the degree of spray. Part of the dehydrated product is separated and treated with a stock solution to obtain a suspension of impurities in concentrated solutions of calcium chloride or magnesium chloride. The suspension is separated, for example, by thickening and filtration. The liquid phase - solutions of calcium chloride or magnesium chloride, purified from impurities, are dehydrated in a fluidized bed apparatus instead of the initial solution using part of the target product in the subsequent stages of the process. The solid phase (sodium chloride, potassium chloride, calcium sulfate, calcium hydroxide, magnesium hydroxide, etc.), as a rule, is washed with the initial solution and used in the main production.

In the starting period for processing the initial solution containing impurities, sparingly soluble in concentrated solutions of calcium chloride or magnesium chloride, an unsatisfactory target product can be used.

Examples of the method

Example 1

1000 parts by weight a solution of calcium chloride composition: CaCl ₂ - 30.02%, NaCl - 8.90%, KCl - 2.50%, Ca (OH) ₂ - 0.50%, H ₂ O - 58.08, was treated at 50 ° C for 45 minutes with part of the target product composition: CaCl ₂ - 84.90%, NaCl - 6.5%, KCl - 0.8%, Ca (OH) ₂ - 0.15%, H ₂ O - 7, 65% taken in the amount of 660 parts by weight The suspension was thickened and the solid phase was filtered. Received 1556 parts by weight the liquid phase, which was submitted for dehydration to a single-chamber apparatus of a fluidized bed at a temperature of 180 ° C with a solution being fed through pneumatic nozzles at an air pressure of 3 atm. Received 1006 parts by weight the target product of the above composition, which was classified and fractions + 3 mm and - 1 mm in the amount of 660 wt.h. used to treat the initial solution in order to purify it from sodium chloride, potassium chloride and calcium hydroxide. The solid phase after drying was used as an anti-icing preparation.

Example 2

1000 parts by weight a solution of magnesium chloride composition: MgCl ₂ - 25.1%, NaCl - 1.9%, KCl - 3.5%, CaSO ₄ - 0.9%, H ₂ O - 68.6%, was treated at 20 ° C within 45 minutes, part of the target product of the composition: MgCl ₂ - 56.2%, NaCl - 0.62%, KCl - 0.36%, CaSO ₄ - 0.60%, H ₂ O - 42.22%, taken in the amount of 310 parts by weight The suspension was filtered and received 1248 wt.h. the liquid phase, which was applied for dehydration to a single-chamber apparatus of a fluidized bed at a temperature of 130 ° C with a solution being supplied to the layer through pneumatic nozzles at an air pressure of 2.5 ati. Received 753 parts by weight the target product of the above composition, part of which without classification in the amount of 310 wt.h. subjected to stock solution treatment as described above. The solid phase was washed with the initial solution and sent to the main cycle of the carnallite factory.

Claims (3)

1. The method of dehydration of solutions of calcium chloride or magnesium chloride in a fluidized bed apparatus by spraying a solution in a layer through nozzles with control of the particle size distribution of the dehydrated product by the degree of atomization, separation of part of the target product and its processing with the original solution to obtain a suspension, characterized in that for processing part the target product using a source solution containing impurities that are hardly soluble in a concentrated solution of the target product, the resulting suspension is separated with Highlighted insolubles, and the solution continues to dewatering in a fluidized bed apparatus. 2. The method according to claim 1, characterized in that for the treatment of part of the target product, an initial solution is used containing impurities such as sodium chloride, potassium chloride, calcium sulfate, calcium or magnesium hydroxide. 3. The method according to claim 1, characterized in that the part of the target product that provides a concentrated solution of calcium chloride or magnesium chloride is taken for treatment with the initial solution, while finely dispersed fractions of the target product are mainly used.