The method of producing cryolite

 

(57) Abstract:

The invention relates to the production of the recovery of cryolite for aluminum smelters. The method of producing cryolite comprises mixing toradoltoradol solution and aluminate solution in the continuous mode, crystallization, dehydration and drying of cryolite. Aluminate solution fed to the mixing depending on the concentrations in toradoltoradol solution of sodium bicarbonate and sodium fluoride, their ratio, flow rate of solution and the concentration of aluminum oxide in the aluminate solution. This invention improves the yield and quality of the product. 3 table.

The invention relates to the production of the recovery of cryolite for aluminum smelters. Obtaining the recovery of cryolite for aluminum smelters based on a mixture of gas cleaning ftoridoboraty solutions with sodium aluminate solution.

A method of obtaining cryolite from fluorinated Stamicarbon solutions of the gas treatment plant by precipitation of sodium aluminate solution at elevated temperature, in which the process is conducted with an excess of fluoride by 10-50% relative to the stoichiometric who SSR 415955, 01 F 7/54, 1979. [1]).

The disadvantage of this method is low removing fluoride (67-70%), low productivity of the process.

A known method of producing cryolite, including the processing gas treatment toradoltoradol solution of carbonate-bearing compound and aluminate solution, followed by the separation of the selected product, in which the processing toradoltoradol solution of carbonate-bearing connection lead to mass relationship of sodium carbonate to bicarbonate of 0.1-0.9 (A. C. the USSR 1090661, C 01 F 7/54, 1984. [2]).

The technical essence, the presence of similar features this decision was made as the nearest equivalent.

The disadvantages of the known solutions: low output fluoride, cryolite, the need for advance preparation (processing CO2-containing gas) gas treatment toradoltoradol solution, the regulation process is only one technological option that to achieve high technical and economic indicators are not enough.

There is no dosing aluminate solution, the most important parameter of the process of obtaining the recovery of cryolite.

Precision dosing of al is e) aluminate solution:

- worsens the chemical composition of cryolite (reduced fluorine content) due to the formation of finely dispersed fractions hydroaluminocarbonate sodium and aluminium hydroxide;

- due to the formation of these impurities deteriorate the physical properties of cryolite: decreases the speed of lightening and filtering cryolite pulp; increased loss of cryolite from the upper discharge cryolite thickener, which, in turn, leads to intensive overgrowing pipelines and gas treatment apparatus of the cryolite.

Lack (nepodozirana) aluminate solution does not allow to link in the cryolite, the maximum amount of sodium fluoride from the gas cleaning solutions, resulting in:

- represented a loss of cryolite;

- to increase the concentration of sodium fluoride in solutions supplied to the gas purification, as a consequence to the increased concentration of sodium fluoride in solutions coming from the gas purification by crystallization (melting) of cryolite, which also leads to deterioration of physical properties of cryolite (size, velocity sedimentation, and filtration).

The task of the invention is to increase the output and quality of the product, increase the technical and economic indicators of Protech deadweight loss.

The technical result of the proposed technology is to optimize the dosage of aluminate solution supplied to the crystallization of cryolite, taking into account the ratio of the concentration of sodium bicarbonate to sodium fluoride in toradoltoradol solution, the values of the concentrations of these components in toradoltoradol solution and in the mother solution, the concentration of aluminum oxide in the aluminate solution.

This technical result is achieved in that in the method of producing cryolite comprising mixing toradoltoradol solution and aluminate solution, crystallization, dehydration and drying of cryolite, the process is conducted in a continuous mode, aluminate solution fed to the mixing depending on the concentrations in toradoltoradol solution of sodium bicarbonate and sodium fluoride, their ratio, flow rate of solution, the concentration of aluminum oxide in the aluminate solution and support the flow of aluminate solution, DMC/h:

when

< / BR>
if CMNaF5, CNaF=7;

5<CNaF<6, CNaF=6;

6CMNaF8, CNaF=4;

CMNaF>8, CNaF=2;

when

< / BR>
ifMPanso3<6, CNaHCO3=8;

6SMPansoB>3=3;

when

< / BR>
ifMPanso36, C1NaHCO3=6;

6<WITHPanso38, C1NaHCO3=4;

8<WITHPanso3101Panso3=2;

WITHMPanso3>101Panso3=0;

where Ql2ABOUT3the flow rate supplied to the crystallization of cryolite aluminate solution, DM3per hour;

VNaF - consumption toradoltoradol solution supplied to the crystallization, m3per hour;

WITHpNaF - concentration of sodium fluoride in toradoltoradol solution supplied to the crystallization, g/DM3;

WITHpPanso3the concentration of sodium bicarbonate in toradoltoradol solution supplied to the crystallization, g/DM5;

l2ABOUT3the concentration of aluminum oxide aluminate in the solution supplied to the crystallization, g/DM3;

WITHMNaF - residual concentration of sodium fluoride in the mother solution, g/DM3;

WITHMPanso3residual concentration of sodium bicarbonate in the mother solution, g/DM3;

NaF - concentration sodium fluoride taken depending on its residual concentration in the mother solution, g/DM;

CNaHO3C3;

- coefficient accounting for the molecular weights of the reactants involved in the reaction of cryolithozone;

- coefficient accounting for the molecular weights of the reactants involved in the reaction of cryolithozone;

1000 is the conversion factor from m3in DM3.

The multiplier (1+0,07) is a condence interval of values in which a reliability of 95% are plotted the results of all experiments. The presence of this interval due to inaccuracies when measuring and adjusting process parameters of cooking cryolite, error analysis solutions, as well as the oscillation module aluminate solution.

The proposed solution is characterized by the following distinctive from the nearest similar features:

- the process is conducted in a continuous mode;

- consumption of aluminate solution support depending on the concentrations in toradoltoradol solution of sodium bicarbonate and sodium fluoride, consumption of this solution and the concentration of aluminum oxide in the aluminate solution;

depending on the ratios of the concentrations in toradoltoradol solution of sodium bicarbonate and sodium fluoride consumption aluminate solution is determined toride sodium.

The use of the above together the hallmarks provides rapid response to the races concentrations in gazoochistnoe and the mother solution, stabilizes the operation of the node cooking cryolite in the conditions of non-stationary process by quickly bring the system to the optimal technological parameters.

Thus, the proposed solution meets the patentability criteria of "novelty."

The comparison of the proposed technical solutions with the closest analogue and other known solutions in the areas identified in the search process, shows the following:

a well - known method of producing cryolite, including the processing gas treatment toradoltoradol solution of carbonate-bearing compound and aluminate solution, followed by the separation of the selected product, in which the processing toradoltoradol solution of carbonate-bearing connection lead to mass relationship of sodium carbonate to sodium bicarbonate 0,1-0,9 [2];

a well - known method of producing cryolite from fluorinated Stamicarbon solutions of the gas treatment plant by precipitation of sodium aluminate solution, the process'm the Nata sodium 5-10 g/l [1];

a well - known method of producing cryolite, including handling fluorinated gases with an alkaline solution and boiling with obtaining pulp cryolite, Department of cryolite from the alkaline solution and the feed solution to the processing of fluorine-containing exhaust gases, in which part of alkali saturated solution after processing gases are mixed with the pulp of cryolite at a ratio of 0.1-4):1 (A. C. the USSR 925866, C 01 F 7/54, 1982. [3]).

The proposed solution is characterized by a well-known features:

- cryolite mixture toradoltoradol solution of aluminate solution, crystallization, dehydration and drying [1, 2, 3];

- the process to a residual concentration of sodium bicarbonate 5-10 g/l [1] (partially in the inventive intervals).

The proposed solution is also characterized not previously known features:

- consumption of aluminum solution is selected depending on the size of the residual concentration in the mother solution of sodium fluoride and sodium bicarbonate in various limits;

- consumption of aluminate solution is selected depending on the ratio of sodium bicarbonate to sodium fluoride in toradoltoradol solution in various limits.

So oshimi when you use them to get more high technical and economic indicators:

stabilization;

operational optimization of technological parameters of the process of cooking cryolite;

- improving the extraction of aluminium and fluorine in the secondary cryolite, indicating its compliance with the patentability criteria of "inventive step".

Examples.

All of the examples at a constant level was maintained for the following technological parameters.

1. The number toradoltoradol solution on boiling cryolite 110 m3/hour.

2. The concentration of Al2ABOUT3in aluminate solution 290g/DM3.

3. The fluorine content in the received cryolite 44%.

4. Removing fluoride cryolite was determined by the ratio of the number of fluorine, actually translated in cryolite (by difference concentrations of NaF in the original and the mother solution), the amount of fluoride that can be translated in cryolite at a concentration of NaF in the mother solution, equal to 6 g/DM3.

5. In the examples compare two options:

Option 1 - existing dosage aluminate solution;

Option 2 - the proposed method of dosage.

< / BR>
In table.1.1 of the cases, when the concentration of NaF in the fallopian dissolve the<WITHNaF<6; 6SMNaF8.

From table. 1-3 it is seen that the proposed method of calculating the dosage of aluminate solution allows to obtain the best technical and economic indicators of cooking cryolite due to more rapid achievement and maintenance of optimal concentration of NaF in the mother solution.

Conducted pilot testing of the proposed technology at the Krasnoyarsk and Irkutsk aluminium smelters, which confirmed its effectiveness.

It should also be noted that the scope of application of the proposed method is not limited to the cryolite from gas cleaning ftoridoboraty solutions of aluminum smelters. This method applies to those cases where the crystallization of cryolite is from ftoridoboraty solutions obtained in any other way, for example:

by mixing solutions of sodium fluoride and sodium bicarbonate;

- decomposition of crematoria sodium soda flowing through reaction

Na2SiF6+4Na2CO3+2H2O=6NaF+4NaHCO3+SiO2< / BR>
Ftoridoboraty solution may have the following composition, g/DM3: NaF - 10-40; PA2CO3- 3-12; Panso3- 12-50.

The application of the proposed S="ptx2">

SOURCES OF INFORMATION

1. A. C. the USSR 415955, C 01 F 7/54, 1979.

2. A. C. the USSR 1090661, C 01 F 7/54, 1984.

3. A. C. the USSR 925866, C 01 F 7/54, 1982.

1. The method of producing cryolite comprising mixing toradoltoradol solution and aluminate solution, crystallization, dehydration and drying of cryolite, wherein the process is conducted in a continuous mode, aluminate solution fed to the mixing depending on the concentrations in toradoltoradol solution of sodium bicarbonate and sodium fluoride, their ratio, flow rate of solution and the concentration of aluminum oxide in the aluminate solution and support the flow of aluminate solution, DM3/h:

when

< / BR>
ifMNaF5, CNaF= 7;

5<WITHNaF<6, CNaF= 6;

6SMNaF8, CNaF= 4;

WITHMNaF>8, CNaF= 2;

when

< / BR>
ifMNaHCO3<6, CNaHCO3= 8,

6SMNaHCO38, CNaHCO3= 6;

8<WITHNaHCO310, CNaHCO3= 4;

WITHMNaHCO3>10, CNaHCO3= 3;

when

< / BR>
ifMNaHCO36, C1NaHCO3= 6;

6<WITHNaHCO38, C1NaHCO3= 4;

8<WITHNaHCO310, C1NaHCO3= 2;

WITHMNaHCO3>10, Cthe target, DM3/h;

V NaF - consumption toradoltoradol solution supplied to the crystallization, m3/h;

WITHRNaF - concentration of sodium fluoride in toradoltoradol solution supplied to the crystallization, g/DM3;

WITHRPanso3the concentration of sodium bicarbonate in toradoltoradol solution supplied to the crystallization, g/DM3;

Al2O3the concentration of aluminum oxide aluminate in the solution supplied to the crystallization, g/DM3;

WITHMNaF - residual concentration of sodium fluoride in the mother solution, g/DM3;

WITHMPanso3residual concentration of sodium bicarbonate in the mother solution, g/DM3;

C NaF - concentration sodium fluoride taken depending on its residual concentration in the mother solution, g/DM3;

CNaHCO3C1NaHCO3- the concentration of sodium bicarbonate is taken depending on its residual concentration in the mother solution, g/DM3;

- coefficient accounting for the molecular weights of the reactants involved in the reaction of cryolithozone;

- coefficient accounting for the molecular weights of the reactants involved in the reaction cryolithozone is which with reliability of 95% are plotted the results of all experiments.

 

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FIELD: nonferrous metallurgy; processing of sodium sulfate solutions.

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4 tbl, 2 ex

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EFFECT: optimized process flowsheet.

1 tbl

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2 ex

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1 tbl, 5 ex

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3 cl, 1 tbl, 2 ex

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