FI78278B - FOERFARANDE FOER FRAMSTAELLNING AV VANADIUMPENTOXID. - Google Patents

Description

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Process for the preparation of vanadium pentoxide

The present invention relates to chemistry and metallurgy, more particularly to processes for the preparation of vanadium pentoxide which can be used in the preparation of vanadium alloys, hardeners and catalysts. The basic raw materials for the production of vanadium pentoxide are vanadium-containing slags formed in the metallurgy of titanium magnetite ores containing 0.5-2% by weight of vanadium.

In the Soviet Union, a comprehensive treatment method for titanium magnetite ore has been developed and exploited commercially, in which iron and vanadium are recovered from this ore by the pyrometallurgical method. A similar formula is used for the treatment of titanium magnetite ores in EAT and China (cf. K. M. Sokolova: "Manufacture and Consumption

Abroad "," Chermetinformatsija "Institute Bulletin, 1981, No. 10 (894), pp. 3-15). According to this method, titanium magnetite ores are converted into vanadium-containing iron, which is then further processed by oxidation with a gaseous oxidant in converters to steel and vanadium slag. The vanadium slag obtained is a starting material for the preparation of vanadium pentoxide.

The process for preparing vanadium pentoxide from a converter slag comprises the following steps: preparation of the slag for calcination (crushing, grinding, separation, mixing with a reagent), oxidative calcination, extraction of the calcined charge with a solvent (water, acids and bases) , precipitation of vanadium pentoxide from solutions, drying, melting and granulation of the vanadium pentoxide obtained.

Other methods for preparing vanadium pentoxide from roscoelite, carnotite, patronite and multi-metal ores, bauxite and phosphorites essentially follow the main steps of this formula.

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The simplest embodiment of a hydrometallurgical method for the recovery of vanadium from titanium magnetites has been developed and implemented in Finland (cf. N.L. Lyakishev et al .: "Vanadium in Ferrous Metallurgy", Moscow, Metallurgical, 1983, p. 192). The small amount of silicon and calcium oxides in the starting ore makes it possible to obtain an iron-vanadium concentrate containing by weight: 67-67.7 Fe, 0.58 SiO2 »2.8 TiO2, 0.98-1.12 V2O5, 0.2 CaO . Vanadium is recovered from this concentrate by omitting the pyro-metallurgical enrichment step. This known method is based mainly on the oxidative roasting of soda-containing (2%) pellets and the consequent production of sodium vanadate, which, after the usual operations (precipitation, washing, drying, melting), yields a product containing 95% or more vanadium pentoxide; the degree of vanadium yield is 77.5%. However, this method is unique in terms of the suitability of the starting composition for the process requirements. In most cases, titanium magnetites have higher concentrations of calcium oxide and silica, which is why such a technique cannot be used to treat them.

For this case, a method has been developed for preparing vanadium pentoxide from a vanadium-containing converter slag by preparing a vanadium-containing starting slag for calcination, roasting in the presence of a reaction additive, extracting the roasted batch, separating the resulting vanadium solution from the cake, precipitating, drying (cf. NP Lyakishev et al .: "Vanadium in Ferrous Metallurgy", Moscow, "Metallurgizdaf 'Publishing Company, 1983, p. 31) .In this way 65-85% of vanadium is extracted into the aqueous solution. aluminates, titanates and silicates to form a soluble glass which is hydrolysed to form a colloidal precipitate, which impairs the filtration of the pulp and leaves impurities of silicon, aluminum and other elements in the final vanadium pentoxide 3 80278 and 80-85% and at best 87-88t0% vanadium pentoxide.Here go In order to obtain a good yield of vanadium pentoxide from vanadium, it is necessary to ensure that many parameters for the starting materials and the process as a whole are optimal. Thus, the properties of vanadium slag in terms of its chemical and mineral composition, particle size, porosity, mechanical strength, density and the like should be good when treated for roasting (phase separation, grinding), during roasting (reduction of sintering capacity, better sludge filtration). For this reason, proper selection of the starting charge and vanadium slag is very important.

It is an object of the present invention to prepare vanadium pentoxide from a charge which makes it possible to obtain cleaner solutions containing vanadium and to improve the quality of the final product.

This object is achieved by a process for the preparation of vanadium pentoxide in which a charge is prepared by mixing vanadium slag and soda, this charge is calcined in an oxidizing atmosphere, the calcined charge is extracted, the vanadium solution obtained is separated from the cake and vanadium pentoxide is precipitated from this solution. -% soda ash and 60-90% by weight of vanadium slag having the following composition in weight percent: - calcium oxide 3-40 - magnesium oxide 2-15 - vanadium oxide 14-30 - silica 12 - 32 - iron, titanium, chromium, manganese , the remainder of the oxides of aluminum and phosphorus, Λ 78278 with a weight ratio of S1O2: (CaO + MgO) of 0.75 to 0.85.

According to one embodiment of this method, 3 to 15% by weight of cake obtained by extracting the calcined batch is added to a charge containing the above-mentioned vanadium slag and soda.

The present invention makes it possible to increase the yield of vanadium from the batch to the final product by 1-2% and to increase the filterability of aqueous solutions containing vanadium by 5-10 times.

The method according to the invention is explained in detail below.

Vanadium slag is used to produce vanadium pentoxide, which is obtained by deaerating vanadium-containing iron with an oxidizing agent in oxygen converters using magnesium- and / or calcium-containing substances as a flux.

Vanadium slag has the following composition in weight percent: - calcium oxide 3-40 - magnesium oxide 2-15 - vanadium oxide 14-30 - silica 12-32 - the remainder oxides of iron, titanium, chromium, manganese, aluminum and phosphorus.

The above oxides are selected within the limits specified above so that the weight ratio of S1O2: (CaO + MgO) is 0.75 to 0.85. This ratio of silica to the sum of calcium and magnesium oxides in the slag facilitates the formation of the most thermodynamically stable and stable silicates which, when the calcined charge is extracted with water, make it possible to obtain solutions containing low levels of silicon, manganese and other elemental impurities. In addition, the above - mentioned ratio of SiO: (CaO +

MgO) makes it possible to substantially reduce the high suspension formation intensity inherent in the prior art methods and to reduce the yield of vanadium.

Vanadium slag having the above composition is ground and mixed with soda in the following proportions, expressed as a percentage by weight: - soda 10 to 40 - vanadium slag 60 to 90.

These amounts of batch components, i.e. vanadium slag and soda, are determined by the fact that when the amount of soda in the batch is less than 10% by weight, the vanadium yield from the calcined batch to the solution does not exceed 60%, requiring an additional recovery step such as acidic extraction, resulting in less impurities in the final product. , such as manganese and phosphorus. An amount of soda greater than 40% in the batch is inappropriate because it does not result in a higher vanadium yield and does not improve the quality of the final product, while in some cases causing undesired sintering of the batch and lowering the calcination yield.

Said vanadium oxide content in the vanadium slag is chosen because when the vanadium oxide content is less than 14%, the reagent consumption per tonne of final product increases considerably, while when the vanadium oxide content increases above 30%, the vanadium yield decreases due to higher sintering of the charge.

The batch having the above composition is calcined at a temperature in the range of 700-800 ° C. The calcined charge is extracted, for example, with water at a temperature of 70-90 ° C and the resulting slurry is filtered. Filtering happens very quickly.

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The high rate of leaching of the slurry as well as the required purity of the solution obtained after filtration of the slurry is only achieved when the composition of the slag is as mentioned above, i.e. the oxide concentrations should be as follows by weight: calcium oxide: 3-40, magnesium oxide: 2-15 , vanadium oxide: 14-30, silica: 12-32, the rest being oxides of iron, titanium, chromium, manganese, aluminum and phosphorus.

After filtration of the slurry, filter cake and solutions containing vanadium are obtained. In order to obtain very pure vanadium pentoxide, the vanadium-containing solutions can be pretreated with aluminum salts, for example aluminum chloride, aluminum sulphate, i.e. alum. Vanadium precipitates from solutions as ammonium vanadate. The resulting ammonium vanadate precipitate is filtered, washed, dried, calcined in an oxidizing atmosphere and then melted at 670-720 ° C to give vanadium pentoxide.

In order to reduce the vanadium loss (waste material) associated with the filter cake and thus increase the total vanadium yield from the slag, 3-15% by weight of cake obtained from the extraction step of the calcined batch and containing 1-3% by weight is added to the charge containing vanadium slag and soda. vanadium pentoxide.

The above amount of cake addition is due to the fact that if the cake is added less than 3%, the addition has no significant effect on the increase of vanadium yield, while if it is added more than 15%, the charge calcination yield decreases and there are more impurities in the final product.

The advantages of the vanadium pentoxide production process of the present invention over the prior art processes are as follows: it increases the degree of vanadium yield from the batch to the final product by 1-2%; - it increases the filtration rate of the vanadium-containing slurry from 1-5 m · * solution / m ^ .h to 25-35 m-Vm ^ .h; - it reduces the amount of impurities in the vanadium solutions and in the final product by 1.5-2 times; - it reduces the production costs of 1 tonne of finished vanadium pentoxide.

The following describes a preferred embodiment of the method of the present invention.

The batch is prepared by mixing 25-30% by weight of soda ash and 70-75% by weight of vanadium slag, containing by weight: - calcium oxide 9-15 - magnesium oxide 4-6 - silica 12 - 15 - vanadium oxide 14 - 20 - the rest Fe-, Mn- , Ti, Cr, Al, P oxides.

In vanadium slag, the weight ratio of silica to the total amount of Ca and Mg oxides - S1O2: (CaO + MgO) - is in the range of 0.75-0.85. The resulting batch is calcined in air at a temperature of 740-760 ° C. The calcined batch is extracted with water in a solid to liquid phase ratio of S: (2-4) and at a temperature of 70-80 ° C. The slurry treated in this way is filtered to separate the residue and the cake containing 1-3% vanadium pentoxide. The resulting solution containing 25 to 65 g / l of vanadium pentoxide is treated at 80 to 95 ° C with ammonium salts, such as ammonium sulfate, at a pH of 2.0 to 2.5, which value is maintained during the precipitation by adding an inorganic acid. , for example sulfuric acid. The ammonium vanadate product formed is filtered, washed with water, dried at 100-150 ° C, calcined in an oxidizing atmosphere at 250-450 ° C and melted at 670-720 ° C. The final product, molten vanadium pentoxide, contains in weight percent: V2O5: 95.3, v2 ° 4: 1 * 2, Fe, Si, Mn, S, P, Cr impurities. The yield of V 2 O 5 in aqueous solution is 91-94%.

In order to obtain very pure (more than 98.0%) vanadium pentoxide, an aluminum salt and, for example, aluminum sulphate, with ammonium salts are added to a filtered solution containing 25-26 g / l of V 2 O 5. In this case, silicon and other impurities precipitate and the precipitate is removed by filtration.

An inorganic acid is added to the filtered solution and ammonium vanadate is precipitated at pH 2.0-2.5, after which the precipitate is then calcined to give the final product containing by weight: V2O5: 99.8, V2O4: 0.1, Fe, Si -, Mn, S, P and Cr impurities: remainder.

In order that the present invention may be better understood, the following are some specific examples which illustrate the preparation of vanadium pentoxide.

Example 1

The batch is prepared by mixing 10% by weight of soda ash and 90% by weight of vanadium slag, containing by weight: - calcium oxide 3 - magnesium oxide 15 - silica 15 - vanadium oxide 28 - the remainder Fe, Ti, Cr, Mn, Al and P- oxides.

In vanadium slag, the weight ratio of S1O2: (CaO + MgO) is 0.85.

The resulting batch is calcined in air at a temperature of 700 ° C. The calcined batch is extracted with water so that the solid phase to liquid phase ratio is S: L * 1: 4 and the temperature is 75 ° C. The resulting slurry is filtered. The solid residue (cake) contains 3% by weight of vanadium pentoxide.

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The filtered solution contains 64 g / l of vanadium pentoxide, which is precipitated with ammonium sulphate at pH 2.0-2.2 to ammonium vanadate. The ammonium vanadate precipitate is filtered, washed, dried at 140-150 ° C and melted at 680-720 ° C. The final product (melt) contains by weight: V2O5: 94.0, V2O4: 1.0, Fe, Si, Cr, Mn, S and P impurities: the remainder.

Example 2

The batch is prepared by mixing 20% by weight of soda ash and 80% by weight of vanadium slag, containing by weight: - calcium oxide 11 - magnesium oxide 5 - silica 12 - vanadium oxide 30 - the remainder Fe, Ti, Cr, Mn, Al and P- oxides.

In vanadium slag, the weight ratio SiO 2: (CaO + MgO) is 0.75.

The resulting batch is calcined in air at a temperature of 700 ° C. The calcined batch is extracted with water in a solid phase to liquid phase ratio of S: L of 1: 4 and temperature of 80 ° C. The resulting slurry is filtered. The resulting solution contains 69 g / l of vanadium pentoxide, and the cake contains 3% by weight of vanadium pentoxide. Vanadium pentoxide in solution is precipitated with ammonium sulfate at pH 2.4-2.5 to ammonium vanadate. The ammonium vanadate precipitate is filtered, washed, dried at 140-150 ° C, calcined at 320-440 ° C and melted at 680-720 ° C.

The final product (molten) vanadium pentoxide contains by weight: V2O5: 94.5, V2O4: 0.9, Fe, Si, Cr, Mn, S and P impurities: the remainder.

Example 3

The batch is prepared by mixing 40% by weight of soda and 60% by weight of vanadium slag, containing by weight: 10 78278 - calcium oxide 40 - magnesium oxide 2 - silica 32 - vanadium oxide 14 - the remainder of Fe, Ti, Cr, Μη, Al and P-oxides.

In vanadium slag, the weight ratio of S1O2: (CaO + MgO) is 0.75. The batch is calcined at 800 ° C. The calcined charge is extracted with water at a S: L ratio of 1: 4 and a temperature of 90 ° C. The resulting slurry is filtered. The solid residue (cake) contains 1% by weight of vanadium pentoxide.

The filtered solution contains 32.5 g / l of vanadium pentoxide, which is precipitated with ammonium sulphate at pH 1.9-2.1 to ammonium vanadate.

The ammonium vanadate precipitate is filtered, washed, dried at 150 ° C, calcined at 380-430 ° C and melted at 680-720 ° C.

The final product (molten) vanadium pentoxide contains in weight percent: V2O5: 95.1, V2O4: 0.4, Fe, Si, Cr, Mn, S and P impurities: the remainder.

Example 4

The batch is prepared by mixing 25% by weight of soda ash and 75% by weight of vanadium slag, containing by weight: - calcium oxide 15 - magnesium oxide 5 - silica 16 - vanadium oxide 25 - the remainder Fe, Ti, Cr, Mn, Al and P- oxides.

In vanadium slag, the weight ratio SiO 2: (CaO + MgO) is 0.80. The batch is calcined at 750 ° C. The calcined charge is extracted with water at a S: L ratio of 1: 3 and a temperature of 80 ° C.

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The resulting slurry is filtered. The solid residue (cake) contains 2.1% by weight of vanadium pentoxide and the filtered solution contains 32.5 g / l V2O5. Vanadium pentoxide in solution is precipitated with ammonium sulfate at a pH of 2.0-2.2.

The steps described in Examples 1 to 3 are then repeated and the final product thus obtained contains, by weight: V2O5: 94.8, V2O4: 0.8, Fe, Si, Cr, Mn, S and P impurities: the remainder.

Example 5

To the charge described in Example 2 above is added 3% by weight of a cake obtained after extraction with water. Other procedures and parameters regarding batch calcination, filtration, precipitation, and other procedures are similar to those described in Example 2.

The final vanadium pentoxide contains, by weight: V2O5: 94.4, V2O4: 0.9, Fe, Si, Cr, Mn, S and P impurities: the remainder.

Example 6

To the charge described in Example 3 above is added 15% by weight of the cake obtained after extraction with water. Other operations and parameters regarding batch calcination, filtration, precipitation, and other operations are similar to those described in Example 3.

The final vanadium pentoxide contains, by weight: V2O5: 95.0, V2O4: 0.4, Fe, Si, Cr, Mn, S and P impurities: the remainder.

Example 7

To the charge described in Example 4 above is added 8% by weight of a cake obtained after extraction with water. Other operations and parameters regarding batch calcination, filtration, precipitation, and other operations are similar to those described in Example 4.

The final vanadium pentoxide contains, by weight: V205: 94.9, V204: 0.7, Fe, Si, Cr, Mn, S and P impurities: the remainder.

The present invention makes it possible to: (1) increase the yield of vanadium from slag to the final product by 1-2%; (2) increase the filtration rate of the vanadium-containing slurry to 35 m 2 / m 2 .h; (3) reduce the amount of impurities in the final product; (4) reduce material consumption per tonne of final product.

Claims (2)

13 78278 A process for preparing vanadium pentoxide, which comprises preparing a charge by mixing a vanadium slag and soda, calcining it in an oxidizing atmosphere, extracting the calcined charge, separating the resulting vanadium solution from the cake and precipitating the vanadium pentoxide from the solution, characterized in that the charge is prepared by mixing 10-40% soda and 60-90% by weight of vanadium slag having the following chemical composition in weight percent: - calcium oxide 3-40 - magnesium oxide 2-15 - vanadium oxide 14-30 - silica 12-32 - the remainder Fe, Cr, Mn, Ti, Al and P-oxides with a total weight ratio of silica to calcium and magnesium oxides in the slag of 0.75 to 0.85. Process according to Claim 1, characterized in that the batch contains 3 to 15% by weight of cake obtained in the extraction step of the calcined batch.