RU2562989C1 - Method of preparing vanadium oxide - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method comprises the following steps: mixing vanadium slag with calcium oxide or limestone to form a mixed material; roasting the obtained mixed material to obtain a calcined clinker; leaching the calcined slag using an oxalate solution with $$C_2{O}_4^{2-}$$

ion concentration of 35-70 g/l at 80-90°C; separating the liquid and solid phases after the leaching reaction to obtain a vanadium-containing liquid leaching product and residual slag; performing treatment to remove silicon from the vanadium-containing liquid leaching product, as a result of which concentration of silicon in the vanadium-containing liquid leaching product becomes less than 0.1 g/l, and then adding ammonium oxalate to the vanadium-containing liquid leaching product to control the molar ratio of $$N{H}_4^{+}$$

to TV in the range of 2-3.5, as a result of which ammonium metavanadate is precipitated and filtered to obtain ammonium metavanadate and liquid wastes; oxidising the ammonium metavanadate, calcination and deamination with preparation of vanadium pentoxide or with further preparation of vancium trioxide via a reduction reaction.

EFFECT: use of vanadium slag with high calcium and phosphorus content, low reagent consumption and cost of the product.

10 cl, 3 ex

Description

FIELD OF THE INVENTION

The present invention relates to the field of production of vanadium oxide, in particular, relates to a method for the preparation of vanadium oxide.

State of the art

The main raw material for the preparation of vanadium oxide, as a rule, is vanadium slag. Currently, vanadium slag used in industrial production is mainly ordinary vanadium slag with a low CaO content, i.e. CaO / V ₂ O ₅ ≤0,15; however, for vanadium slag with a high content of calcium and phosphorus (i.e., CaO / V ₂ O ₅ ≥0.16, P≥0.06%), the method for extracting vanadium by roasting with sodium and leaching with water is not suitable due to the high content CaO, and the method for extracting vanadium by calcining and leaching with sulfuric acid is not suitable because of the high phosphorus content. For this reason, a method of extracting vanadium (in the form of a vanadium compound) from vanadium slag with a high content of calcium and phosphorus has not yet been implemented in industry.

Basically, there are two ways to extract vanadium from vanadium slag, i.e. a method for extracting vanadium by firing with sodium; and a method for extracting vanadium with lime calcination. Patent documents CN 85102378, CN 201110082443.6, CN 201110197357.X, CN 86108218 and CN 200810001589.1 disclose methods for preparing vanadium oxide by firing with sodium, the residual slag obtained by firing with sodium and leaching with water from vanadium slag contains V ⁵⁺ and ⁶⁺ , which are hazardous waste and difficult to recycle; residual slag cannot be returned to the blast furnace for smelting cast iron for reuse, as contains about 6% sodium oxide; The sodium sulfate by-product generated during wastewater treatment is inconvenient for storage, as It contains vanadium, chromium and ammonium sulfates and is readily soluble in water. The indicated application for the extraction of vanadium by firing with sodium from vanadium slag is very affected due to the aforementioned problems.

The Chinese patent documents CN 200710202445.8, CN 200810305602.2, CN 200810305603.7, and CN 200810305601.8 disclose methods for the preparation of vanadium oxide by calcining and leaching of sulfuric acid from vanadium slag, while these methods are applicable only to low phosphorus vanadium slag and can not be applied at present vanadium slag with a high content of calcium and phosphorus; the use of sulfuric acid for leaching requires a very low content of metallic iron in fine powders of vanadium slag, which increases the complexity of the control; and residual slag must be reused after removal of calcium sulfate from the slag.

Chinese patent document CN 201210066735 discloses a method for extracting vanadium by leaching the clinker of vanadium slag using ammonium carbonate, i.e. the implementation of leaching using 200-800 g / l of a solution of ammonium carbonate with a ratio of liquid and solid phase (ml: g) in the range of 5: 1-30: 1 at 60-98 ° C, while this method has the disadvantage associated with a large consumption of leaching agent, and the decomposition of large quantities of ammonium carbonate can adversely affect working conditions.

Thus, there is an urgent need for a method for preparing vanadium oxide from vanadium slag with a high content of calcium and phosphorus in an efficient and economical manner.

SUMMARY OF THE INVENTION

Given at least one of the aforementioned disadvantages of the prior art, the present invention provides a method by which vanadium oxide can be obtained from vanadium slag with a high content of calcium and phosphorus.

в интервале 35-70 г/л при 80-90°С; осуществление разделения жидкой и твердой фазы после завершения реакции выщелачивания с получением ванадийсодержащего жидкого продукта выщелачивания и остаточного шлака; осуществление обработки по удалению кремния из ванадийсодержащего жидкого продукта выщелачивания, в результате которой концентрация кремния в ванадийсодержащем жидком продукте выщелачивания составляет менее 0,1 г/л и затем добавление оксалата аммония в ванадийсодержащий жидкий продукт выщелачивания для регулирования молярного отношения $$N{H}_4^{+}$$

к TV в интервале 2-3,5, осуществляя таким образом осаждение и фильтрацию метаванадата аммония с получением метаванадата аммония и жидких отходов; осуществление окисления метаванадата аммония, кальцинации и дезаминирования с приготовлением пентоксида ванадия или с приготовлением далее триоксида ванадия посредством реакции восстановления.The present invention provides a method for preparing vanadium oxide. The specified method comprises the steps of: mixing vanadium slag with calcium oxide or limestone to form a mixed material, with a mass ratio of CaO to V ₂ O ₅ 5 in the mixed material in the range of 0.25-0.65; firing the mixed material to produce calcined clinker; leaching of calcined clinker by using an oxalate solution with an ion concentration $$C_2{O}_{\mathrm{four}}^{2-}$$

in the range of 35-70 g / l at 80-90 ° C; the implementation of the separation of the liquid and solid phase after the completion of the leaching reaction to obtain a vanadium-containing liquid leaching product and residual slag; processing to remove silicon from the vanadium-containing liquid leaching product, resulting in a silicon concentration in the vanadium-containing liquid leaching product is less than 0.1 g / l and then adding ammonium oxalate to the vanadium-containing liquid leaching product to control the molar ratio $$N{H}_{\mathrm{four}}^{+}$$

to TV in the range of 2-3.5, thereby precipitating and filtering ammonium metavanadate to produce ammonium metavanadate and liquid wastes; the oxidation of ammonium metavanadate, calcination and deamination with the preparation of vanadium pentoxide or with the preparation of further vanadium trioxide through a reduction reaction.

Compared with the prior art, the present invention has advantages in the preparation of vanadium oxide from vanadium slag with a high content of calcium and phosphorus and allows the cyclic use of liquid waste and residual slag. Thus, in the present invention, vanadium oxide can be prepared from ordinary vanadium slag with a high content of calcium and phosphorus, which, in addition to meeting environmental requirements, can also reduce the consumption of reagents and the cost of production.

The implementation of the invention

Hereinafter, a method for preparing vanadium oxide according to the present invention will be described in detail together with exemplary embodiments.

в интервале 35-70 г/л при 80-90°C; осуществление разделения жидкой и твердой фазы после завершения реакции выщелачивания с получением ванадийсодержащего жидкого продукта выщелачивания и остаточного шлака; осуществление обработки по удалению кремния из ванадийсодержащего жидкого продукта выщелачивания, в результате которой концентрация кремния в ванадийсодержащем жидком продукте выщелачивания составляет менее 0,1 г/л и затем, добавление оксалата аммония в ванадийсодержащий жидкий продукт выщелачивания для регулирования молярного отношения $$N{H}_4^{+}$$

к TV в интервале 2-3,5, осуществляя таким образом осаждение и фильтрацию метаванадата аммония с получением метаванадата аммония и жидких отходов; и проведение окисления метаванадата аммония, кальцинации и дезаминирования с приготовлением пентоксида ванадия или с приготовлением далее триоксида ванадия посредством реакции восстановления. В настоящем документе на стадии выщелачивания кальцинированного клинкера, контролируя температуру взвеси в интервале 80-95°C, можно получить высокую растворимость и степень диссоциации и тем самым можно увеличить выход ванадия. Для выщелачивания применяют оксалат, так как растворимость оксалата кальция меньше, чем растворимость метаванадата кальция, пированадата кальция и ортованадата кальция, и раствор оксалата способен не разлагаться в значительных количествах при нагревании; предпочтительно оксалат может содержать оксалат аммония, и ионы аммония в оксалате аммония можно использовать повторно в процессе осаждения ванадия.The method of preparing vanadium oxide according to the present invention contains the following steps, carried out sequentially: mixing vanadium slag with calcium oxide or limestone to form mixed with a mass ratio of CaO to V ₂ O ₅ in the mixed material in the range of 0.25-0.65, thus to control that vanadium present in calcined and calcined clinker is predominantly in the form of calcium metavanadate, as calcium metavanadate is better soluble in water than calcium pyrovanadate and calcium orthovanadate, which is more favorable for leaching; firing the mixed material to produce calcined clinker; leaching of calcined clinker by using an oxalate solution with an ion concentration $$C_2{O}_{\mathrm{four}}^{2-}$$

in the range of 35-70 g / l at 80-90 ° C; the implementation of the separation of the liquid and solid phase after the completion of the leaching reaction to obtain a vanadium-containing liquid leaching product and residual slag; processing to remove silicon from the vanadium-containing liquid leaching product, as a result of which the silicon concentration in the vanadium-containing liquid leaching product is less than 0.1 g / l and then adding ammonium oxalate to the vanadium-containing liquid leaching product to control the molar ratio $$N{H}_{\mathrm{four}}^{+}$$

to TV in the range of 2-3.5, thereby precipitating and filtering ammonium metavanadate to produce ammonium metavanadate and liquid wastes; and the oxidation of ammonium metavanadate, calcination and deamination with the preparation of vanadium pentoxide or with the preparation of further vanadium trioxide through a reduction reaction. In this document, at the stage of leaching of calcined clinker, by controlling the temperature of the suspension in the range of 80-95 ° C, it is possible to obtain high solubility and degree of dissociation, and thereby the yield of vanadium can be increased. Oxalate is used for leaching, since the solubility of calcium oxalate is less than the solubility of calcium metavanadate, calcium pyrovanadate and calcium orthovanadate, and the oxalate solution can not decompose in significant quantities when heated; preferably, the oxalate may contain ammonium oxalate, and the ammonium ions in ammonium oxalate can be reused in the vanadium precipitation process.

In one example embodiment of the present invention, the calcining temperature in the calcining step is preferably in the range of 800-900 ° C, and the calcining time is preferably in the range of 60-300 minutes at which the desired result and firing efficiency can be obtained.

In one example of an embodiment of the present invention, the particle sizes of vanadium slag in the mixed material formation step and the particle sizes of calcined slag in the leached calcined clinker stage are not more than 0.1 mm. Vanadium slag is pulverized to obtain particles no larger than 0.1 mm in size, as a result of which the ferrovanadium spinel in vanadium slag can be sufficiently exposed, which contributes to the oxidation of ferrovanadium spinel and also promotes contact interaction of ferrovanadium spinel with limestone. Calcined clinker is pulverized to obtain particles no larger than 0.1 mm in order to increase the specific surface area of the slag particles, which contributes to the dissolution of calcium metavanadate.

In one example embodiment of the present invention, the oxalate solution contains sodium oxalate with a concentration of less than or equal to 35 g / l (i.e., ≤35 g / l), and ammonium oxalate with a concentration of less than or equal to 65 g / l (i.e. e. ≤65 g / l), which can provide a condition under which sodium oxalate and ammonium oxalate do not crystallize at 30-40 ° C.

In one example embodiment of the present invention, in the leaching stage of the calcined clinker, the ratio of liquid to solid phase is in the range of 3: 1-6: 1 ml / g.

In one example embodiment of the present invention, at the stage of separating the liquid and the solid phase, the temperature of the separated suspension is controlled in the range of 70-95 ° C, which can provide a condition under which vanadium in the solution may not precipitate prematurely in the form of metavanadate.

In one example embodiment of the present invention, in the steps of precipitating and filtering ammonium metavanadate to produce ammonium metavanadate and liquid wastes, the temperature of the dissolved system is controlled at 30-40 ° C. The indicated temperature before filtering ammonium metavanadate is controlled at a level of 30-40 ° C, because sodium oxalate is easily crystallized and mixed with ammonium metavanadate if the temperature is too low, which affects the purity of ammonium metavanadate; if the temperature is too high, the solubility of ammonium metavanadate may increase and the deposition rate of vanadium may decrease.

In one example embodiment of the present invention, the method further includes returning the residual slag to the blast furnace after sintering the residual slag.

In one example of an embodiment of the present invention, the method further comprises partially evaporating and condensing the liquid waste to produce condensate and a vanadium-containing concentrate, the condensate being used to wash the residual slag obtained in the liquid and solid phase separation step, and the vanadium-containing concentrate is returned to the calcined leach stage clinker as a leaching agent, which can increase the recovery of vanadium. Preferably, the total vanadium content (hereinafter referred to as “TV” hereinafter) in the vanadium-containing concentrate is less than 2 g / l. In this document, the amount of water resulting from the evaporation and condensation of liquid waste must be controlled in accordance with the amount of water for washing the residual slag, and usually about 6-8 m ^{3 of} liquid waste is needed for evaporation if one ton of vanadium pentoxide is obtained, in addition , the remaining concentrate contains oxalate, which is completely returned to the leaching stage as a leaching agent.

Further, according to the method of the present invention, ammonium metavanadate can not be washed, because the sodium content in the ammonium metavanadate obtained by precipitation is very low and ammonium oxalate can decompose into gaseous ammonia and carbon dioxide, which volatilize during the preparation of vanadium trioxide or vanadium pentoxide and do not affect the quality of the product.

Further, at the stage of separation of the solid and liquid phases of the present invention, to obtain a significant cleaning effect, sodium aluminate can also be added to the vanadium-containing liquid leachate obtained in the leaching process in order to remove silicon.

Further, in another example of an embodiment of the present invention, a method for preparing vanadium oxide can also be carried out as follows:

a) preparation of raw materials: mixing vanadium slag with a particle size of less than 0.1 mm with calcium oxide or limestone to form a mixed material in which the amount of calcium oxide or limestone is such that it provides a mass ratio of CaO to V ₂ O ₅ in the mixed material within 0.25-0.65;

b) calcium calcination: oxidation and calcination of the mixed material at a constant temperature of 800-900 ° C for 60-300 minutes to obtain calcined clinker;

с концентрацией в интервале 35-70 г/л, и подвергают выщелачиванию при температуре суспензии в интервале 80-95°C с перемешиванием, в котором соотношение жидкой и твердой фазы (мл:г) в процессе выщелачивания находится предпочтительно в интервале 3:1-6:1. Предпочтительно указанный оксалат представляет собой смесь оксалата натрия и оксалата аммония, в котором концентрация оксалата натрия меньше или равна 35 г/л и концентрация оксалата аммония меньше или равна 65 г/л;c) oxalate leaching: calcined clinker is ground into a powder with a particle size of not more than 0.1 mm, added to an oxalate solution containing ions $$C_2{O}_{\mathrm{four}}^{2-}$$

with a concentration in the range of 35-70 g / l, and subjected to leaching at a temperature of the suspension in the range of 80-95 ° C with stirring, in which the ratio of liquid to solid phase (ml: g) during the leaching is preferably in the range of 3: 1- 6: 1. Preferably, said oxalate is a mixture of sodium oxalate and ammonium oxalate, in which the concentration of sodium oxalate is less than or equal to 35 g / l and the concentration of ammonium oxalate is less than or equal to 65 g / l;

d) separation of the liquid and solid phases: filtering and washing the obtained vanadium-containing liquid leachate and residual slag after the leaching process is completed, and preferably the suspension temperature during filtration is 70-95 ° C;

к TV в пределах 2-3,5, осуществляя таким образом осаждение и фильтрацию метаванадата аммония с получением метаванадата аммония и жидких отходов. В настоящем документе температуру растворенной системы контролируют предпочтительно в интервале 30-40°C в процессе осаждения метаванадата аммония до стадии фильтрации;e) purification and recovery of vanadium: the implementation of the method of removing silicon from the vanadium-containing liquid leaching product, resulting in a silicon concentration in the vanadium-containing liquid leaching product is less than 0.1 g / l; adding ammonium oxalate to the liquid leach product that has been subjected to silicon removal treatment to control the molar ratio $$N{H}_{\mathrm{four}}^{+}$$

to TV within 2-3.5, thereby precipitating and filtering ammonium metavanadate to produce ammonium metavanadate and liquid wastes. Herein, the temperature of the dissolved system is preferably controlled in the range of 30-40 ° C. during the precipitation of ammonium metavanadate prior to the filtration step;

f) oxidative calcination or reduction: the oxidation, calcination and deamination of ammonium metavanadate with the preparation of vanadium pentoxide or further preparation of vanadium trioxide through a reduction reaction;

g) treatment of waste slag and liquid waste: returning the residual slag to the blast furnace for reuse after sintering the residual slag; liquid waste after partial evaporation and condensation is returned to stage d) for washing the residual slag as washing water, and the concentrate is returned to stage c) for leaching clinker as a leaching agent.

The exemplary embodiments of the present invention will be set forth below in connection with particular examples. These examples are provided only to illustrate the present invention and in no way limit the present invention.

Example 1

100 g of ordinary vanadium slag (containing 17.2% V ₂ O ₅ , 1.84% CaO and 0.04% P) with a particle size of not more than 0.1 mm are uniformly mixed with 5 g of calcium oxide, the CaO / V ratio ₂ O ₅ in the mixed material is 0.4; the mixed material is fired in a muffle furnace for 180 minutes at a firing temperature of 850 ° C with air aeration; the resulting calcined clinker is pulverized to a particle size of not more than 0.1 mm, added to 400 ml of an oxalate solution, which consists of 35 g / l sodium oxalate and 40 g / l ammonium oxalate, and leached for 120 minutes at a suspension temperature of 90 ° C with stirring; after the leaching reaction is completed, the liquid and solid phases are separated to obtain a vanadium-containing liquid leachate and residual slag, the total vanadium content (ie, “TV”) in the residual slag being 0.95% by mass, and the degree of leaching of vanadium is 89 ,8%; 0.8 g of sodium aluminate are added to the liquid leachate, stirred for 20 minutes and then filtered to obtain a filtrate; 10 g of ammonium oxalate are added to the obtained filtrate and stirred for 1 hour, and then filtered after cooling the obtained filtrate to ambient temperature and settled for 12 hours, thereby obtaining ammonium metavanadate and liquid waste in which the TV content is 0.94 g / l; ammonium metavanadate is subjected to oxidative calcination at 500 ° C for 5 hours, and the resulting sample contains 99.3% V ₂ O ₅ .

The liquid wastes are evaporated and condensed to produce water and condensed liquid wastes, and the resulting water is used to wash the residual slag obtained by leaching in the following method to obtain vanadium-containing wash water. Vanadium-containing wash water and oxalate are added to the condensed liquid waste for use as a leaching agent in the following method.

Example 2

100 g of ordinary vanadium slag (containing 17.2% V ₂ O ₅ , 1.84% CaO and 0.04% P) with a particle size of not more than 0.1 mm are uniformly mixed with 3 g of calcium oxide, the CaO / V ratio ₂ O ₅ in the mixed material is 0.28; the mixed material is fired in a muffle furnace for 60 minutes at a firing temperature of 900 ° C with air aeration; the resulting calcined clinker is crushed into a powder with a particle size of not more than 0.1 mm, added to 600 ml of a solution of oxalate, which consists of 30 g / l of sodium oxalate and 25 g / l of ammonium oxalate, and leached for 120 minutes at a suspension temperature of 95 ° C with stirring; after the leaching reaction is completed, the liquid and solid phases are separated to obtain a vanadium-containing liquid leach product and residual slag, in which the total vanadium content (ie, “TV”) in the residual slag is 1.01% by mass, and the degree of leaching of vanadium is 89.5%; 0.8 g of sodium aluminate are added to the liquid leachate, stirred for 20 minutes and then filtered to obtain a filtrate; 18 g of ammonium oxalate are added to the obtained filtrate and stirred for 1 hour, and then filtered after cooling the obtained filtrate to ambient temperature and settled for 12 hours, ammonium metavanadate and liquid waste are obtained in which the content of TU is 1.28 g / l; ammonium metavanadate is subjected to oxidative calcination at 500 ° C for 5 hours and the resulting sample contains 98.9% V ₂ O ₅ .

The liquid wastes are evaporated and condensed to produce water and condensed liquid wastes, and the resulting water is used to wash the residual slag obtained by leaching in the following method to obtain vanadium-containing wash water. Vanadium-containing wash water and oxalate are added to the condensed liquid waste for use as a leaching agent in the following method.

Example 3

100 g vanadium slag with a high content of calcium and phosphorus (containing 15.7% V ₂ O ₅ , 9.53% CaO and 0.28% P and the CaO / V ₂ O ₅ ratio is 0.57) with a particle size of not more than 0.1 mm is fired in a muffle furnace for 300 minutes at a firing temperature of 800 ° C with air aeration; the resulting calcined clinker is pulverized to a particle size of not more than 0.1 mm, added to 500 ml of an oxalate solution, which consists of 35 g / l sodium oxalate and 65 g / l ammonium oxalate, and leached for 120 minutes at suspension temperature 80 ° C with stirring; after the leaching reaction is completed, the liquid and solid phases are separated to obtain a vanadium-containing liquid leachate and residual slag, the total vanadium content (ie, “TV”) in the residual slag being 1.06% by mass, and the leaching degree of vanadium is 88 %; 0.8 g of sodium aluminate are added to the liquid leachate, stirred for 20 minutes and then filtered to obtain a filtrate; 7 g of ammonium oxalate are added to the obtained filtrate and stirred for 1 hour, and then filtered after cooling the obtained filtrate to ambient temperature and settled for 12 hours, thereby obtaining ammonium metavanadate and liquid waste in which the TV content is 0.82 g / l; ammonium metavanadate is subjected to oxidative calcination at 500 ° C for 5 hours, and the resulting sample contains 99.2% V ₂ O ₅ .

The liquid waste is evaporated and condensed to produce water and condensed liquid waste, and the resulting water is used to wash the residual slag obtained by leaching in the following method to produce vanadium-containing wash water. Vanadium-containing wash water and oxalate are added to the condensed liquid waste for use as a leaching agent in the following method.

In conclusion, in the above method for preparing vanadium oxide of the present invention, vanadium oxide is prepared from vanadium slag by calcining and oxalate leaching, and vanadium oxide can be prepared from ordinary vanadium slag and vanadium slag with a high content of calcium and phosphorus, which, in addition to meeting environmental requirements solves the problem of using vanadium slag with a high content of calcium and phosphorus as a raw material for the extraction of vanadium.

Although the present invention has been described in connection with several exemplary embodiments, those skilled in the art should appreciate that various modifications can be made to the above embodiments within the spirit and scope of the appended claims.

Claims (10)

1. A method of preparing vanadium oxide, comprising the steps of: mixing vanadium slag with calcium oxide or limestone to form a mixed material, with a mass ratio of CaO to V ₂ O ₅ in the mixed material in the range of 0.25-0.65;
calcining the mixed material to produce calcined clinker;
leached calcined clinker with oxalate solution with ion concentration

in the range of 35-70 g / l at 80-95 ° C;
carry out the separation of the liquid and solid phases after the completion of the leaching reaction to obtain a vanadium-containing liquid leaching product and residual slag;
a treatment is carried out to remove silicon from the vanadium-containing liquid leaching product, whereby the silicon concentration in the vanadium-containing liquid leaching product is less than 0.1 g / l, and then ammonium oxalate is added to the vanadium-containing liquid leaching product to control the molar ratio

to the total content of vanadium (TV) in the range of 2-3.5, thereby precipitating and filtering ammonium metavanadate to obtain ammonium metavanadate and liquid wastes; and
ammonia metavanadate is subjected to oxidation, calcination and deamination with the preparation of vanadium pentoxide or with the preparation of further vanadium trioxide through a reduction reaction. 2. The method of preparation of vanadium oxide according to claim 1, in which the firing temperature at the stage of firing is 800-900 ° C, and the firing time is 60-300 minutes. 3. The method of preparing vanadium oxide according to claim 1, in which the vanadium slag at the stage of formation of the mixed material and the calcined clinker at the stage of leaching the calcined clinker has a particle size of not more than 0.1 mm 4. The method of preparation of vanadium oxide according to claim 1, in which the oxalate solution contains sodium oxalate in a concentration of less than or equal to 35 g / l, and ammonium oxalate in a concentration of less than or equal to 65 g / l. 5. The method of preparation of vanadium oxide according to claim 1, in which the ratio of the liquid phase to the solid phase at the stage of leaching of calcined clinker is in the range of 3: 1-6: 1 ml / g 6. The method of preparation of vanadium oxide according to claim 1, in which at the stage of separation of liquid and solid phase, the temperature of the separated suspension is controlled in the range of 70-95 ° C. 7. The method of preparation of vanadium oxide according to claim 1, in which at the stages of separation and filtration of ammonium metavanadate to obtain ammonium metavanadate and liquid waste, the temperature of the dissolved system is controlled in the range of 30-40 ° C. 8. The method of preparation of vanadium oxide according to claim 1, in which the vanadium slag is a vanadium slag having a high content of calcium and phosphorus, or vanadium slag obtained in steelmaking. 9. A method of preparing vanadium oxide according to claim 1, which further includes returning the residual slag to the blast furnace after sintering the residual slag. 10. The method of preparation of vanadium oxide according to claim 1 or 9, which further includes the partial evaporation and condensation of liquid waste to produce condensate and a vanadium-containing concentrate, the above condensate being used to wash the residual slag obtained in the liquid and solid phase separation stage and vanadium-containing the concentrate is returned to the leaching stage of calcined clinker as a leaching agent.