Granulated mixture to produce aluminium by electrolysis (options) and how you can get

 

(57) Abstract:

Use: production of aluminium by electrolysis, specifically: granulated mixture for aluminium electrolysis cells (options) and how you can get it. Effect: reduction of losses granular Tortola in the electrolysis of aluminium by increasing the dissolution rate of the pellets. The inventive adjustment of the composition of the electrolyte known in the mixture containing calcium fluoride and a mixture of the fluorides of sodium and aluminum and/or their compounds, the new is that it contains a mixture of the fluorides of sodium and aluminum and/or their connections with the ratio NaF/AlF3not exceeding 0,86 in the following ratio of ingredients, wt.%: Caf30.1 to about 30.0; a mixture of the fluorides of sodium and aluminum and/or their connections with the ratio NaF/AlF3not more than 0.85 rest. To maintain the level of electrolyte aluminium electrolysis cells in granular mixture containing calcium fluoride and a mixture of the fluorides of sodium and aluminum and/or their compounds, the new is that it contains a mixture of the fluorides of sodium and aluminum and/or their connections with the ratio NaF/AlF3equal to 0,85-1,60 in the following ratio of ingredients, wt.%: Caf20,1-20,0, a mixture of the fluorides of sodium and alumina introduction into the electrolyte aluminum electrolytic comprising a mixture of fluoride salts, crushing, moisture, granulation and drying, it is new that as fluoride salts used aluminum fluoride and/or sodium fluoride, and/or cryolite, the mixing is carried out in the presence of calcium fluoride, and grinding salts are fraction content of not more than 8 μm in an amount of not less than 10 wt.%. 3 S. p. f-crystals, 1 table.

The invention relates to ferrous metallurgy, namely the production of aluminum by electrolysis.

Known electrolyte to produce aluminium containing 49-55% of sodium fluoride, 36-42% aluminum fluoride at a molar ratio of 2,6-2,85, calcium fluoride of 1.5-5% magnesium fluoride. The total content of the additives is not more than 9% (Typical technological design service aluminium electrolysis cells with lateral electrical power supply. YOU, 1975, S. 14).

The downside of it is the increased consumption of fluoride salts in the process of the cell.

A method of obtaining granulated cryolite to introduce into the electrolyte aluminum electrolytic pasta humidity 18-25% in countercurrent rotating drum furnace with internal heating, including heating the paste at a linear speed framerect 30-40oC/min

However, upon receipt of the product by this method significant energy consumption and loss of fluorine in the process, limited technological possibilities of application of the obtained granulated product.

Known electrolyte to produce aluminium adopted for the prototype,containing, by weight. aluminum fluoride 30-40; calcium fluoride 1-7; fluoride magnesium 1-6; aluminium chloride 0.5 to 3; alumina 1-10; sodium fluoride else, when this molar ratio NaF/AlF3(cryolite ratio) is from 2.4 to 3.4 [1] To adjust the composition of the electrolyte and maintain its preset level in the electrolyzer periodically immersed cryolite with cryolite ratio of 1.63-3 and aluminum fluoride. The use of this electrolyte reduces fluoride salts due to partial replacement of the fluoride of aluminum chloride.

However, due to evaporation, pylones and hydrolysis increased consumption of fluoride salts.

Closest to the proposed method of obtaining a granulated mixture for the electrolytic production of aluminum is the way in which powdered fluoride salt mix, crushed to content fraction is not more than 8 μm in cakradatta significant loss of fluoride salts due to evaporation and hydrolysis.

The problem is solved in that for adjusting the composition of the electrolyte known in the mixture containing calcium fluoride and a mixture of the fluorides of sodium and aluminum and/or their compounds, the new is that it contains a mixture of the fluorides of sodium and aluminum and/or their connections with the ratio NaF/AlF3not more than 0.85 in the following ratio of ingredients, wt. Caf20.1 to about 30.0; a mixture of the fluorides of sodium and aluminum and/or their connections with the ratio NaF/AlF3not more than 0.85 rest.

To maintain the level of electrolyte aluminium electrolysis cells in granular mixture containing calcium fluoride and a mixture of the fluorides of sodium and aluminum and/or their compounds, the new is that it contains a mixture of the fluorides of sodium and aluminum and/or their connections with the ratio NaF/ALF3equal to 0,85-1,60 in the following ratio of ingredients, wt. Caf20,1-20,0; a mixture of the fluorides of sodium and aluminum and/or their connections with the ratio NaF/AlF30,85-1,60 else.

In a known method of obtaining a granulated mixture for introduction into the electrolyte aluminum electrolytic cells comprising a mixture of fluoride salts, crushing, moisture, granulation and drying, it is new that as fluoride salts IP is calcium fluoride, and grinding salts are fraction content of not more than 8 μm in an amount of not less than 10 wt.

Calcium fluoride reduces the loss of fluoride by dissolving aluminum pellets in the electrolyte due to the weight of the granules and by increasing the surface tension of the melt in the place of dissolution of the granules. The contents of fractions 8 μm should be at least 10% to make the material was granulated.

When the ratio NaF/AlF3more than 0.85 correction of electrolyte becomes difficult, as a corrective agent (AlF3in the electrolyte is deposited a significant amount of NaF, which causes an increase in the level of the electrolyte, which can cause upset technologies.

The reduction in the content of Caf2in grains less than 0.1% does not reduce the loss of granules at the dissolution, and the increase of its content more than 30% may cause increased its content in the electrolyte is more than the allowed value. It is possible weighting of the electrolyte, floating aluminum in the electrolytic cell and the disorder of the process.

When reducing NaF/AlF3less than 0.85 introduction of granules in the electrolyte reduces the efficiency of the fusion levels, and the increase of this ratio is the technology.

The decrease in the content Caf2while maintaining the electrolyte level less than 0.1% will increase the loss of fluorine from the melting of the granules, and the increase in its content of more than 20% may cause the ascent of the metal in the electrolytic cell and the disorder of technology.

Example 1. To prepare the mixture to adjust the composition of the electrolyte was mixed 2997 g of pure aluminum fluoride and 3 g (0.1%) calcium fluoride (fluorite concentrate). The total weight of the mixture of 3 kg of the resulting mixture was ground in a vibrating mill to fraction content of less than 8 μm, equal to 16% and Then the mixture was granulated. The degree of moisture in the granulation was 22% of the Obtained granules were dried at a temperature of 350oC. the Pellets are durable.

250 g industrial electrolyte melt in stilografica crucible at a temperature of 960oSince it was loaded with 30 g of the obtained granules. After complete dissolution of the granules electrolyte froze and weighed. Loss of granules was 10.2%

Example 2. Mixed 2.1 kg fluoride of aluminium and 0.9 kg of calcium fluoride (fluorite concentrate). The resulting mixture was ground in a vibrating mill to fraction content of less than 8 μm,equal to 10% Then the mixture was granulated. Moisture level was 24% in industrial electrolyte at 960oC. Loss of granules was 5.6%

Example 3. Same as in example 2, only the content of particles less than 8 μm was 8% Material not granulated.

Example 4. Aluminum fluoride technical mixed with technical cryolite in General the ratio of sodium fluoride to aluminum fluoride in the mixture is equal to 0.6 and added 15% calcium fluoride. The total weight of the mixture of 3 kg of the resulting mixture was ground until a fraction content of less than 8 μm, equal to 16% and was granulated. Next, as in example 1. Loss of granules when dissolved in the electrolyte was 6.5%

Example 5. For preparation of the charge to maintain the level of electrolyte was mixed technical aluminum fluoride and sodium fluoride in a ratio of NaF/AlF3equal to 1.6 and added 20% calcium fluoride (fluorite concentrate). The total weight of the mixture of 3 kg of a Mixture of crushed before fraction content of less than 8 μm, equal to 20% Then the powder was granulated. Pellets were moistened to 22% Drying was carried out at 350oC. the Dried granules in the amount of 30 g was loaded into the melt industrial electrolyte 250 g 960oC. After melting of the granules melt froze and weighed. Losses during melting was 2.4%

The table shows, characterization composition of the electrolyte aluminum electrolytic containing calcium fluoride and a mixture of sodium fluoride (NaF) and aluminum (AlF3and/or their compounds, characterized in that it contains a mixture of the fluorides of sodium and aluminum and/or their connections with the ratio NaF/AlF3not more than 0.85 in the following ratio of ingredients, wt.

Calcium fluoride CaF20,1 30,0

The mixture of the fluorides of sodium and aluminum and/or their connections with the ratio NaF/AlF3not more than 0.85 Rest

2. Granulated mixture containing calcium fluoride and a mixture of sodium fluoride, NaF, and aluminum AlF3and / or their compounds, characterized in that it contains a mixture of the fluorides of sodium and aluminum and/or their connections with the ratio NaF/AlF3equal to 0,85 1,60, in the following ratio of ingredients, wt.

Calcium fluoride CaF20,1 20,0%

The mixture of the fluorides of sodium and aluminum and/or their connections with the ratio NaF/AlF30,85 1,60 Else

3. A method of obtaining a granulated mixture for introduction into the electrolyte aluminum electrolytic cells comprising a mixture of fluoride salts, crushing, moisture, granulation and drying, characterized in that as fluoride salts used aluminum fluoride and/or sodium fluoride and /or their compounds, the mixing is carried out in p is at least 10 wt.

 

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FIELD: nonferrous metallurgy; processing of sodium sulfate solutions.

SUBSTANCE: the invention is pertaining to the field of nonferrous metallurgy, in particular, to processing of sodium sulfate solutions, which are released into a slime storage after a gas cleaning treatment electrolysis of bodies by production of aluminum. The method of processing of sodium sulfate solutions produced after the gas purification of the electrolysis bodies at production of aluminum provides for the gases purification from sulfuric oxides and fluorides by their sprinkling with a sodium sulfate solution in the washers, extraction from the solution after the gas purification of the fundamental quantity of sodium fluoride in the form of cryolite. The sodium sulfate solution purified from cryolite is in addition purified from sodium fluoride by its treatment at the temperature of 95-105°С within 1.5-2.0 hours with a lime milk injected into the sodium sulfate solution at the rate of stoichiometric binding of fluorine contained in the solution in CaF2. The sodium sulfate solution purified from fluorine is further subjected to a concentrating evaporation till achieving the density of a product solution of 1.37±0.02 g/l and extract a sodium sulfate from it into the sediment a in the form of berkeyit salt by introduction in the product solution of a carbonate soda till achieving the concentration of the titratabic alkali in the mother liquor of 215-230 g/l Na2Ot and the density of the solution in the suspension up to 1.35±0.02 g/l at stirring of the suspension at temperature of 95-100°С within 30-40 minutes. The invention ensures a more complete extraction of sodium sulfate from the product sodium sulfate solution in the form of berkeyit salt purified from sodium fluoride.

EFFECT: the invention ensures a more complete extraction of sodium sulfate from the product sodium sulfate solution in the form of berkeyit salt purified from sodium fluoride.

FIELD: mining industry.

SUBSTANCE: method comprises charging cryolite in rinsing water, washing it at stirring, and dehydration of washed product. Washing is continued until content of sodium sulfate achieves 45-65% that in initial cryolite, which requires time from 5 to 60 min at rinsing water temperature 25 to 70°C and water-to-cryolite weight ratio (3-10):1.

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4 tbl, 2 ex

FIELD: mining industry.

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EFFECT: optimized process flowsheet.

1 tbl

FIELD: chemistry.

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EFFECT: invention allows for obtaining cryolite and ammonium chloride at the same time.

2 ex

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EFFECT: reduced costs, high quality.

4 cl, 1 dwg

FIELD: chemistry.

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1 tbl, 5 ex

FIELD: metallurgy.

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3 cl, 1 tbl, 2 ex

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EFFECT: obtainment of high-quality return fluorine-containing product.

5 cl, 1 tbl, 1 ex

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1 ex, 2 tbl

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2 cl, 3 tbl

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2 cl, 2 ex

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2 cl

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1 tbl

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12 cl, 7 ex, 3 dwg

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11 cl, 5 dwg, 1 tbl

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3 cl, 1 dwg, 1 tbl

FIELD: chemistry.

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EFFECT: recycling wastes, extracting valuable components from wastes and returning said components into the technological process.

5 cl, 1 tbl, 2 ex

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