GB2194941A

GB2194941A - Process for recovering vanadium values

Info

Publication number: GB2194941A
Application number: GB8621799A
Authority: GB
Inventors: Susanna Andreevna Amirova; Olga Gennadievna Kremneva; Leonid Andreevich Smirnov; Anatoly Anatolievi Filippenkov; Lev Efimovich Kolpakov; Jury Stepanovich Schekalev; Anatoly Kuzmich Shashin; Irek Nsyrovich Gubaidullin
Original assignee: PERM POLT I; URALSKY INST CHERNYKH METALL
Current assignee: PERM POLT I; URALSKY INST CHERNYKH METALL
Priority date: 1986-09-10
Filing date: 1986-09-10
Publication date: 1988-03-23
Anticipated expiration: 2006-09-10
Also published as: GB2194941B; DE3632847A1; FR2604428B1; FR2604428A1; GB8621799D0; JPS63100019A

Abstract

A process for recovering vanadium values from vanadium-containing slags comprises forming a charge consisting of a mixture comprising 10 to 40% by weight of soda and 90 to 60% by weight of a vanadium-containing slag which comprises, by weight: calcium oxide 3 to 40% magnesium oxide 2 to 15% vanadium oxide 14 to 30% silica 12 to 32% the balance being oxides of one or more of Fe, Cr, Mn, Ti, Al and P, and the molar ratio of silica to the sum of the calcium oxide and the magnesium oxide being from 0.75 to 0.85, calcining the charge in an oxidising atmosphere, leaching the calcined charge, separating the resulting solution from the solids and recovering vanadium values from the solution.

Description

SPECIFICATION Process for recovering vanadium values The present invention relates to the art of chemistry and metallurgy, more particularly, to processes for producing vanadium pentoxide which is useful in the manufacture of vanadium alloys, hardeners and catalysts. The basic raw materials for the production of vanadium pentoxide are vanadium-containing slags obtained in the metallurgy by processing titanomagnetite ores incorporating 0.5 to 2% by mass of vanadium.

In the Soviet Union there has been developed and commercially implemented the process of a comprehensive treatment of titanomagnetite ores comprising simultaneously recovering iron and vanadium therefrom by a pyrometallurgical way. A similar scheme is used for processing of titanomagnetite ores in SAR and China (cf. K.M.Sokolova "Manufacture and Consumption Abroard", Bulletin of the Institute "Chermetinformatsija", 1981, issue 10 (894), p.3-15). In accordance with this scheme titanomagnetite ores are processed into a vanadium iron which is further reprocessed, by way of oxidation with a gaseous oxidizing agent in converters, into a steel and a vanadium slag. The resulting vanadium slag is the starting material for the production of vanadium pentoxide.

The process for producing vanadium pentoxide from converter slags consists in the following steps: preparation of the slag to calcination (crushing, grinding, separation, mixing with a reactant), oxidizing calcination, leaching of the calcined charge by means of a solvent (water, solutions of acids and alkalis), precipitation of vanadium pentoxide from solutions, drying, melting and granulation of the resulting vanadium pentoxide.

Other processes for producing vanadium pentoxide from roscoelite, carnotite, patronite and polymetallic ores, bauxites and phosphorites substantially reproduce the major steps of this scheme.

The most simple embodiment of a hydrometallurgical process for recovering vanadium from titanomagnetites has been developed and implemented in Finland (cf. N.L.Lyakishev et al. "Vanadium in Ferrous Metallurgy", Moscow, Metallurgizdat, 1983, p.192). A small amount of oxides of silicon and calcium in the starting ore makes it possible to obtain an iron-vanadium concentrate containing, per cent by mass: 67-67.7 Fe, 0.58 SiO2, 2.8 TiO2, 0.98-1.12 V205, 0.2 CaO.

From this concentrate vanadium is recovered while omitting the stage of a pyrometallurgical enrichment. This prior art process resides substantially in an oxidizing roasting of pellets containing soda (2%) and a subsequent production of sodium vanadate, wherefrom after conventional operations (precipitation, washing, drying, melting) a product is obtained which contains 95% and more of vanadium pentoxide; the degree of vanadium recovery is 77.5%. However, this process is unique as regards the compliance of the starting composition with the process requirements. In most cases titanomagnetites feature higher concentrations of calcium oxide and silica, wherefore such technology is inapplicable to the processing thereof.

For such case a process has been developed for producing vanadium pentoxide from a converter vanadium slag involving preparation of the starting vanadium-containing slag to calcination, roasting thereof in the presence of a reactive additive, leaching of the roasted charge, separation of the resulting vanadium solution from the cake, precipitation of vanadium pentoxide, its drying and melting (cf. N.P.Lyakishev et al., "Vanadium in Ferrous Metallurgy", Moscow, "Metallurgizdat" Publishing House, 1983, p.31). In doing so, extracted into the aqueous solution are 65-85% of vanadium. However, along with vanadium, aluminates, titanates, silicates also pass into solution thus forming soluble glass which is hydrolyzed with the formation of a colloidal precipitate. This impairs filtration of pulp and contaminates the final vanadium pentoxide with oxides of silicon, aluminium and other elements.The thus-prepared product contains 80-85% and, at best, 87-88.00/0 of vanadium pentoxide. This process necessitates, to ensure a high degree of recovery of vanadium into vanadium pentoxide, an optimal observance of a number of basic parameters characterizing the starting materials and the process on the whole.

Thus, the vanadium slag, as regards its chemical and mineralogical composition, particle size, porosity, mechanical strength, density and the like, should have high characteristics when preconditioned for roasting (separation into phases, disintegration), during the roasting (lowering of sintering ability), upon leaching (increase of vanadium extraction, better filtering ability of the pulp). For this reason, a proper selection of the starting charge and vanadium slag composition is of a great significance.

It is an object of the present invention to produce vanadium pentoxide from such a charge which would make it possible to obtain a higher purity of vanadium-containing solutions and to improve quality of the final product.

This object is accomplished by a process for producing vanadium pentoxide comprising preparation of a charge by intermixing a vanadium slag and soda, calcination of the charge in an oxidizing atmosphere, leaching of the calcined charge, separation of the resulting vanadium solution from the cake and precipitation of vanadium pentoxide from this solution, wherein, according to the present invention, the charge is prepared by mixing 10-40Yo by mass of soda and 60-90% by mass of a vanadium slag having the following composition, per cent by mass: calcium oxide 3 to 40 magnesium oxide 2 to 15 vanadium oxide 14 to 30 silicon oxide * 12 to 32 oxides of iron, titanium, chromium, manganese, aluminium, phosphorus the balance, wherein the mass ratio of SiO2:(CaO+MgO) is equal to 0.75-0.85.

An embodiment of this process resides in that into the charge incorporating the abovementioned vanadium slag and soda 3 to 15% by mass of the cake obtained in the stage of leaching of the calcined charge are introduced.

The present invention makes it possible to increase the degree of recovery of vanadium from the charge into the final product by 1-2% and to elevate the rate of filtration of aqueous vanadium-containing solutions by 5 to 10 times.

A detailed description of the process according to the present invention is given hereinbelow.

For the production of vanadium pentoxide a vanadium slag is used which is produced in purging of vanadium irons with an oxidizing agent in oxygen converters using magnesium-and/or calcium-containing materials as a flux.

The vanadium slag has the following composition, % by mass: calcium oxide 3 to 40 magnesium oxide 2 to 15 vanadium oxide 14 to 30 silicon oxide 12 to 32 oxides of iron, titanium, chromium, manganese, aluminium, phosphorus the balance.

The above-mentioned oxides are chosen within the above-specified limits so that the mass ratio of SiO2:(CaO+MgO) in the slag be equal to 0.75-0.85. This ratio of silicon oxide to the total of oxides of calcium and magnesium in the slag facilitates the formation of thermodynamically more stable and durable silicates which, upon an aqueous leaching of the calcined charge, enable preparation of solutions with a smaller content of impurities of silicon, manganese and other elements. Furthermore, the above-mentioned ratio of SiO2:(CaO+MgO) makes it possible to substantially reduce a high intensity of suspension formation characteristic for the prior art processes and lowering the degree of vanadium recovery.

The vanadium slag of the above-mentioned pomposition is disintegrated and mixed with soda ash in the following proportions, % by mass: soda 10 to 40 vanadium slag 60 to 90 These proportions of the charge components, i.e. vanadium slag and soda are defined by the fact that at a content of soda in the charge of less than 10% by mass the degree of recovery of vanadium from the calcined charge into the solution does not exceed 60% which necessitates an additional recovery stage such as an acid leaching stage which results in a considerable contamination of the final product with impurities of, for example, manganese and phosphorus.

An increased content of soda in the charge above 40% is inexpedient, since it does not result in a higher degree of vanadium recovery and does not improve quality of the final product, while in some cases it causes undesirable phenomena of the charge sintering and lowers the calcination productivity.

The content of vanadium oxide in the vanadium slag is selected due to the fact that at a content of vanadium oxide below 14% the rates of consumption of reactants per ton of the final product are noticeably increased, while at a content of vanadium oxide above 30% the degree of vanadium recovery is lowered due to an increased intensity of the charge sintering upon its calcination.

The charge of the above-specified composition is calcined at a temperature within the range of from 700 to 800"C. The calcined charge is leached with, for example water, at a temperature of 70 to 90"C and the resulting pulp is filtered. The filtration proceeds at a high rate.

A high rate of the pulp filtration, as well as the required purity of the solution obtained after the pulp filtration are ensured only at the above-mentioned composition of the slag, wherein the content of oxides should be the following, per cent by mass: caclium oxide-3-40, magnesium oxide-2-15, vanadium oxide-14-30, silicon oxide-12-32, the balance being oxides of iron, titanium, chromium, manganese, aluminium, phosphorus.

After the pulp filtration a cake and vanadium-containing solutions are obtained. To obtain vanadium pentoxide of a high purity grade, the vanadium-containing solutions can be preliminarily treated with aluminium salts, e.g. aluminium chloride aluminium sulphate or alum. Vanadium from solutions is precipitated as ammonium vanadate. The resulting precipitate of ammonium vanadate is filtered, washed, dried, calcined in an oxidizing atmosphere and then melted at a temperature of from 670 to 720"C to give, as a result, vanadium pentoxide.

To reduce losses of vanadium with the cake (refuse) and, hence, to increase the total recovery of vanadium from slags, into the charge containing vanadium slag and soda 3-15% by mass of the cake resulting from the stage of leaching of the calcined charge and containing 1-39G by mass of vanadium pentoxide are introduced.

The above-specified amount of the cake additive is defined by the fact that the addition of the cake in an amount of less than 3% do not provide any substantial effect on the increase of vanadium recovery, whereas its amount above 15% lowers productivity of the charge calcination and contaminates the final product.

The process for producing vanadium pentoxide according to the present invention, as compared to the prior art processes, has the following advantages: -it increases the degree of vanadium recovery from the charge into the final product by 1-2%; -it raises the rate of filtration of a vanadium-containing pulp from 1-5 m3 of solution/m2.h; -it lowers the content of impurities in vanadium solutions and in the final product by 1.5-2 times; -it lowers costs of production of 1 t of the final vanadium pentoxide.

Described hereinbelow is the best mode for carrying out the process according to the present invention.

A charge is prepared by mixing 25-30% by mass of soda ash and 70-75 R6 by mass of a vanadium slag containing, per cent by mass: calcium oxide 9-15 magnesium oxide 4-6 silicon oxide 12-15 vanadium oxide 14-20 oxides of Fe, Mn, Ti, Cr, Al, P the balance.

In the vanadium siag the mass ratio of silicon dioxide to the total of Ca and Mg oxides-SiO2:(CaO+MgO) is within the range of from 0.75 to 0.85. The resulting charge is calcined in the air at a temperature of 740-760"C. The calcined charge is leached with water at a ratio of the solid and liquid phases S:L= 1(2-4) and at a temperature of 70-80 C. The thus-prepared pulp is filtered to separate the residue-cake containing 1-3% of vanadium pentoxide. The resulting solution containing 25-65 g/l of vanadium pentoxide is treated at a temperature of 80-95"C with ammonium salts such as ammonium sulphate at a pH=2.0-2.5 which is maintained during precipitation by the addition of an inorganic acid, e.g. sulphuric acid.The formed precipitate of ammonium vanadate is filtered-off, washed with water, dried at a temperature of 100-150"C, calcined in an oxidizing atmosphere at a temperature of 250-450"C and melted at a temperature of 670-720"C. The final (molten) vanadium pentoxide contains, per cent by mass: V205-95.3, V204-1.2, impurities of Fe, Si, Mn, S, P, Cr-the balance. The degree of recovery of V205 into the aqueous solution is 91-94%.

For the production of a high-purity vanadium pentoxide (above 98.0%), into a filtered solution containing 25-65 g/l of V205 aluminium salts are added, e.g. aluminium alum, along with ammonium salts. In this case, silicon and other impurities are precipitated and the precipitate is removed by filtration.

An inorganic acid is added to the filtered solution and ammonium vanadate is precipitated at a pH=2.0-2.5, the precipitate is then calcined to give the final product containing, % by mass: V205-99.8, V204-0.1, impurities of Fe, Si, Mn, S, P, Cr-the balance.

For a better understanding of the present invention, some specific examples illustrating the production of vanadium pentoxide are given hereinbelow.

Example 1 A charge is prepared by mixing 10% by mass of soda ash and 90% by mass of a vanadium slag containing, % by mass: calcium oxide 3 magnesium oxide 15 silicon oxide 15 vanadium oxide 28 oxides of Fe, Ti, Cr, Mn, Al, P the balance.

In the vanadium slag the mass ratio of SiO2:(CaO+MgO)==0.85. The resulting charge is calcined in the air at the temperature of 700"C. The calcined charge is leached with water at the solid-to-liquid ratio S:L=1:4 and at the temperature of 75"C. The obtained pulp is filtered. The solid residue (cake) contains 3% by mass of vanadium pentoxide.

The filtered-off solution contains 64 g/l of vanadium pentoxide which is precipitated by ammonium sulphate at a pH=2.0-2.2 in the form of ammonium vanadate. The precipitate of ammonium vanadate is filtered-off, washed, dried at a temperature of 140-150"C, calcined at a temperature within the range of from 300 to 450"C and melted at a temperature of from 680 to 720"C. The final (molten) product contains, % by mass: V205-94.0, V204-1 .0, impurities of Fe, Si, Cr, Mn, S, P-the balance.

Example 2 A charge is prepared by mixing 20% by mass of soda ash and 80% by mass of a vanadium slag containing, % by mass: calcium oxide 11 magnesium oxide 5 silicon oxide 12 vanadium oxide 30 oxides of Fe, Ti, Cr, Mn, Al, P the balance.

In the vanadium slag the mass ratio of SiO2:(CaO+MgO)==0.75. The prepared charge is calcined in the air at the temperature of 700"C. The calcined charge is leached with water at the solid-to-liquid ratio S:L= 1:4 and at the temperature of 80"C. The resulting pulp is filtered. The obtained solution contains 69 g/l of vanadium pentoxide and the cake contains 3% of vanadium pentoxide. Vanadium pentoxide in the solution is precipitated by means of ammonium sulphate at a pH= 2.4-2.5 as ammonium vanadate. The precipitate of ammonium vanadate is filtered-off, washed, dried at a temperature of 140-1500C, calcined at a temperature within the range of from 320 to 440"C and melted at a temperature of 680-720"C.

The final (molten) product-vanadium pentoxide contains, per cent by mass: V205-94.5, V204-O.9, impurities of Fe, Si, Mn, Cr, S, P-the balance.

Example 3 A charge is prepared by mixing 40% by mass of soda ash and 60% by mass of a vanadium slag containing, % by mass: calcium oxide 40 magnesium oxide 2 silicon oxide 32 vanadium oxide 14 oxides of Fe, Ti, Cr, Mn, Al, P the balance.

In the vanadium slag the mass ratio of Si02:(CaO+MgO)==0.75. The charge is calcined at the temperature of 800 C. The calcined charge is leached with water at the ratio of S:L= 1:4 and at the temperature of 90"C. The obtained pulp is filtered. The solid residue (cake) contains 1% of vanadium pentoxide.

The filtered-off solution contains 32.5 g/l of vanadium pentoxide which is precipitated by means of ammonium sulphate at a pH=1.9-2.1 as ammonium vanadate.

The precipitate of ammonium vanadate is filtered-off washed, dried at the temperature of 150"C, calcined at a temperature of from 380 to 430 C and melted at a temperature of from 680 to 720"C.

The final (fused) product-vanadium pentoxide contains, 96 by mass: V205=95.1, V204=0.4, impurities of Fe, Si, Mn, Cr, S, P-the balance.

Example 4 A charge is prepared by mixing 25% by mass of soda ash and 75% by mass of a vanadium slag containing, % by mass: calcium oxide 15 magnesium oxide 5 silicon oxide 16 vanadium oxide 25 oxides of Fe, Ti, Cr, Mn, Al,- P the balance.

In the vanadium slag the mass ratio of SiO2:(CaO+MgO)==0.80. The charge is calcined at the temperature of 750"C. The calcined charge is leached with water at the S:L= 1:3 and at the temperature of 80"C. The resulting pulp is filtered. The solid residue (cake) contains 2.1% of vanadium pentoxide and the filtered-off solution-32.5 g/l of V2O5. Vanadium pentoxide from the solution is precipitated by means of ammonium sulphate at a pH=2.0-2.2.

Then the operations described in Examples 1 through 3 are repeated and the final product thus obtained contains, 96 by mass: V205=94.8, V2O4-0.8, impurities of Fe, Si, Mn, Cr, S, P-the balance.

Example 5 To the charge described in Example 2 hereinbefore 3% by mass of the cake produced after water leaching are added. Further operations and parameters of the charge calcination, filtration, precipitation and other operations are similar to those described in Example 2.

The final vanadium pentoxide contains, % by mass: V2O5=94.4, V204-0.9, impurities of Fe, Si, Mn, Cr, S, P-the balance.

Example 6 To the charge described in Example 3 hereinbefore 15% by mass of the cake obtained after water leaching are added. Further operations, parameters of the charge calcination, filtration, precipitation and other operations are similar to those described in Example 3.

The final vanadium pentoxide contains, % by mass: V205=95.0, V204=0.4, impurities of Fe, Si, Mn, Cr, S, P-the balance.

Example 7 To the charge described in Example 4 8% by mass of the cake obtained after water leaching are added. Further operations and parameters of the charge calcination, filtration, precipitation and other operations are similar to those of Example 4.

The final vanadium pentoxide contains, % by mass: V205=94.9, V204=0.7, impurities of Fe, Si, Mn, Cr, S, P-the balance.

The present invention makes it possible: (1) to increase recovery of vanadium from a slag into the final product by 1-2%; (2) to increase the rate of filtration of a vanadium-containing pulp to 35 m3/m2.h; (3) reduce the amount of impurities in the final product; (4) reduce the material consumption per ton of the final product.

Claims

1. A process for recovering vanadium values from vanadium-containing slags, which comprises forming a charge consisting of a mixture comprising 10 to 40% by weight of soda and 90 to 60% by weight of a vanadium-containing slag which comprises by weight: calcium oxide 3 to 40% magnesium oxide 2 to 15% vanadium oxide 14 to 30% silica 12 to 32% the balance being oxides of one or more of Fe, Cr, Mn, Ti, Al and P, and the molar ratio of silica to the sum of the calcium oxide and the magnesium oxide being from 0.75 to 0.85, calcining the charge in an oxidising atmosphere, leaching the calcined charge, separating the resulting solution from the solids and recovering vanadium values from the solution.

2. A process according to claim 1, in which the charge subjected to calcination additionally comprises from 3 to 15% by weight of leached solids from a previous run.

3. A process for recovering vanadium values substantially as herein described in any of the Examples.

4. Vanadium values when obtained by the process claimed in any of the preceding claims.