RU2454369C1 - Method of producing vanadium oxide - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to vanadium oxide extraction. The method of producing vanadium oxide involves preparation of starting vanadium-containing material for burning, burning with lime treatment, leaching with sulphuric acid, separating the solid substance and liquid, precipitation of ammonium polyvanadate with an ammonium salt and removing ammonia by calcination or reduction to obtain vanadium oxide. The solid starting material used at said steps has total amount of alkali metal of not more than 0.3 wt % and total amount of Cl^- and NO₃ ^- ions of not more than 0.1 wt %, and the liquid starting material has total amount of alkali metal of not more than 0.1 g/l and total amount of of Cl^- and NO₃ ^- ions of not more than 0.1 g/l.

EFFECT: invention increases the degree of extraction of vanadium and enables to recycle waste water formed during the vanadium extraction process.

10 cl, 1 dwg, 12 tbl, 3 ex

Description

FIELD OF THE INVENTION

The present invention relates to a pure method for producing vanadium oxide and belongs to the field of vanadium oxide extraction.

State of the art

A common vanadium extraction method using a sodium salt includes the selection of common sodium salts, such as Na ₂ CO ₃ , Na ₂ SO ₄ or NaCl, as additives and firing the sodium salt with a vanadium-containing starting material at high temperature, where vanadium is in the starting material the substance is oxidized to V ⁵⁺ with atmospheric oxygen and then V ⁵⁺ binds to the sodium salt to form sodium vanadate, which is readily soluble in water; leaching the calcined product with water to dissolve sodium vanadate in solution, performing solid-liquid separation, then removing major impurities such as P, Si and so on from the solution using CaCl ₂ , adding to it ammonium salts such as (NH ₄ ) ₂ SO ₄ , NH ₄ Cl, (NH ₄ ) ₂ CO ₃ or NH ₄ NO ₃ , etc., adjusting the pH of the solution in the range of 1.5-2.5, heating the solution above 90 ° C and keeping at this temperature within 40-90 min to isolate ammonium polyvanadate from the precipitate; removing impurities such as sodium salts precipitated from ammonium polyvanadate, washing with water after filtration, drying and calcining the precipitate to remove ammonia to produce V ₂ O _5, or reducing the precipitate at high temperature with a reducing gas such as coal gas or natural gas to obtain V ₂ O ₃ . Currently, the largest number of manufacturers in the world adheres to this method of obtaining vanadium products.

This method has the following advantages: high product quality, method stability and easy control. However, the ammonium salt is used in an amount higher than the theoretical amount during the precipitation of vanadium to obtain a high-quality vanadium product, so that the wastewater after precipitation of vanadium has a high concentration of ammonia nitrogen and sodium salt and is the most difficult to process, for example, the concentration of NH ₄ ^{+ is} usually as high as 2000-8000 mg / L or even higher, and the concentration of Na ⁺ may be higher than 20 g / L. Therefore, wastewater treatment is the most difficult problem to manipulate in a vanadium extraction method using sodium salt. If the wastewater is directly returned to the leaching stage for circulation, when sodium vanadate in the calcined product (also called “calcined substance”) is continuously dissolved in water, when sodium salt cannot be discharged from the solution, then the concentration of sodium salt in the solution becomes significantly higher, the amount of salt the ammonia required to precipitate vanadium becomes significantly larger, the solution quickly becomes viscous, it becomes difficult to filter or precipitate vanadium, and in fact circulation e can be continued after 1-2 cycles, so the wastewater can not be directly circulated and reused.

Currently, there are mainly two schemes for solving the problems of wastewater pollution from the method of extraction of vanadium using sodium salt. One scheme is the removal of heavy metals, the implementation of ammonia removal and processing to remove sodium and then unloading, where the ammonia removal method mainly includes an air purification method, a membrane separation method, a magnesium ammonium phosphate precipitation method, a chemical oxidation method, a zeolite adsorption method, and a biological nitrogen removal method, and the sodium removal method mainly adheres to the crystallization concentration method. The disadvantages of this scheme include that the cost of processing to remove ammonia and treatment to remove sodium is too high to be accepted for industrial plants, probably new contaminants appear during processing and the regenerated sodium salt is a lot of impurities sodium sulfate, which will emit SO ₂ , which pollutes the environment after firing and therefore is not suitable as a firing additive. Another scheme is the removal of heavy metals, the implementation of ammonia removal and sodium removal treatments, and the return of condensed water for circulation. The difference from the first scheme is that the water of the first scheme does not circulate, but is consistent with the national standard for industrial wastewater (≤15 mg / l for ammonia nitrogen in wastewater), so it is very difficult to agree on a standard and requires a high price, although the second scheme does not discharge wastewater, a large amount of energy is consumed to evaporate the wastewater, which also has a disadvantage, high cost, and usually non-regenerable evaporated gaseous ammonia.

Therefore, there is an urgent need for solutions in the field of treatment and disposal of wastewater having a high content of ammonia nitrogen and a high content of sodium salt as a result of a method of extracting vanadium using sodium salt.

From the 1960s and 1970s, a vanadium extraction method using lime or limestone as a firing additive, commonly referred to as a vanadium extraction method using calcium salt, or a calcination vanadium extraction method that targets some of the inherited disadvantages of the vanadium extraction method using the sodium salt was investigated. including (1) a certain restriction on the CaO content (less than 1.5%) in vanadium slag, because the yield of extracted vanadium is reduced by 4.7–9%, since the content of burning of CaO in slag increases by 1%; (2) the high cost due to the large expendable amount of sodium salt and ammonium salt; and (3) environmental pollution caused by the large amount of sodium salt and ammonium salt in wastewater. The calcined product of the vanadium extraction method using the calcium salt may be leached with sulfuric acid or carbonate or bicarbonate.

In German patent application No. 2324737 and British patent application No. 1394024, a method for leaching a calcined product with liming with a solution of sodium carbonate is described. US Pat. No. 3,853,985 describes a method for leaching a calcined product with liming with ammonium carbonate or bicarbonate. The publication "Thermodynamics and kinetics of vanadium slag calcium salt roasting-carbonate leaching" (Vanadium titanium, 1997, No.6: 1-6) describes the thermodynamics and kinetics of leaching of a calcined calcined calcined carbonate and bicarbonate product. Due to the use of sodium salt and ammonium salt, the methods described in the literature also have the problem of treating wastewater with ammonia nitrogen.

UK patent application No. 1394024 also describes a method comprising leaching the calcined product with sulfuric acid or hydrochloric acid, adjusting the pH of the acidic leaching product in the range of 1.6-1.9, heating for hydrolysis and precipitation of vanadium, and drying and calcining the precipitate with obtaining a vanadium oxide product containing approximately 93.5% V ₂ O ₅ and a significant amount of impurities. The publication "Study of V ₂ O ₅ extraction process by vanadium slag lime roasting method" (Iron Steel Vanadium Titanium, 1992, 13 (6): 1-9) describes a study of the production of V ₂ O _{5 by} affecting the crushed vanadium slag calcining and sulfuric acid leaching, in which sulfuric acid is added to the obtained acid leaching product to adjust the pH to 2 and then heated to hydrolyze and precipitate vanadium to obtain a product with a purity of 93.6-93.92%. The publication "Study of V ₂ O ₅ extraction by vanadium slag calcium salt roasting-sulfuric acid leaching" describes a calcination study with liming and leaching of vanadium slag by sulfuric acid. The Tula Vanadium Plant of the Former Soviet Union, the world's first (also the only) vanadium plant, which adheres to the method: calcination with lime - leaching with sulfuric acid - precipitation of vanadium by hydrolysis, which can give the product V ₂ O ₅ with a purity of 88-94% (in average 92%) and containing the main impurities Mn, Mg and Ca, and then the melting of the product V ₂ O ₅ in vanadium - iron (ferrovanadium), also containing many impurities; therefore, the manufacturer is not competitive on the international market and mainly supplies the product to the domestic market, which is the main reason why other vanadium plants do not adhere to this method.

To improve the competitiveness of the product on the market, in Russian patent application No. 2001127026/02 and 96106854/02, a method for producing high-quality vanadium oxide from a hydrolyzed precipitate containing impurities of Mn, Ca and Mg is described. The method involves using NaOH to dissolve the hydrolyzed precipitate, then adding an ammonium salt like ammonium sulfate, along with heating, precipitating ammonium polyvanadate and calcining to produce high-quality vanadium oxide with a V ₂ O ₅ content higher than 98%. The method reduces the total amount of wastewater containing ammonia, but still requires wastewater treatment, including the removal of ammonia and the removal of sodium; therefore, there are still technical and economic difficulties of high cost and still difficulty in treating wastewater with ammonia nitrogen, the degree of vanadium extraction is further reduced to some extent due to the long processing method and complex methods.

To date, there is no corresponding publication regarding a method that can not only produce a high-quality vanadium product, but also completely solve the problem of treating and reusing waste water from vanadium extraction.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a pure process for producing vanadium oxide, in which not only can a high-quality vanadium product be obtained, but also wastewater can be circulated and reused after vanadium extraction.

The method for producing vanadium oxide in the present invention includes the following steps:

a) mixing the vanadium-containing substance with the additive to obtain a mixed substance, where the additive is CaO or limestone and the amount of additive in the mixed substance, the mass ratio of CaO / V ₂ O ₅ is 0.5-1.4: 1;

b) calcining the mixed substance at 860-950 ° C in an oxidizing atmosphere for 60-240 minutes to obtain a calcination product;

c) adding water to the calcined product to obtain a suspension, mixing and slowly adding a solution of sulfuric acid to leach the suspension while adjusting the pH in the range of 2.5-3.5;

d) removing the leach residue to obtain a leach product, exposing the leach product to a P-removing treatment to obtain a mass ratio of total V to P (hereinafter referred to as TV / P) in the leach product ≥ 1000, washing the residue with circulating water to obtain wash water used to prepare the suspension for the next leaching;

e) adding ammonium salt to the leach product after removal of P to obtain a mass ratio of NH ₃ / Mn in the leach product of 0.3-3.0: 1 (a vanadium-containing substance usually contains an amount of Mn), adjusting the pH of the solution with sulfuric acid in the range 1.5-2.5, heating at a temperature of from 90 ° C to the boiling point, keeping at this temperature for 30-120 minutes, filtering and washing, and drying the precipitate to obtain ammonium polyvanadate;

f) acting on the ammonium polyvanadate of calcination to remove ammonia to produce V ₂ O ₅ or reducing the ammonium polyvanadate to produce V ₂ O ₃ and

g) removing impurities of P, Mn and Mg in the wastewater formed in step e) to obtain concentrations of Mn ⁺² and Mg ⁺² lower than 5 g / l, respectively, and a concentration of P lower than 0.005 g / l to obtain circulation water, and returning the circulating water to step c) for preparing a suspension and to step d) for washing the residue,

where the solid starting material used in the above steps has a total amount of alkali metal of not more than 0.3 wt.% and a total amount of Cl ^- and NO ₃ ^- not more than 0.1 wt.%; the liquid starting material used in the above steps has a total amount of alkali metal of not more than 0.1 g / l and a total amount of Cl ^- and NO ₃ ^- not more than 0.1 g / l.

According to the present invention, the wastewater can be circulated and reused; in addition, the method of the invention provides calcining and leaching with sulfuric acid to produce a vanadium solution substantially free of alkali metal ions, and various starting materials (including added water) are substantially free of readily soluble alkali metal, halogen and nitrate ions, moreover, the balance of readily soluble ions can be maintained during the circulation method, the wastewater can be circulated and reused after treatment, and thus the treatment problem is avoided wastewater conventional vanadium extraction process using sodium salt.

In step a), the vanadium-containing substance can be various vanadium-containing starting materials used to produce vanadium oxide, such as vanadium slag or other vanadium-containing starting materials (such as vanadium-containing magnetite and vanadium-lead-zinc ore, etc.), preferably vanadium-containing slag.

Preferably, in step a), the mixed substance is sprayed to particles with a size of 0.1 mm or less to obtain vanadium readily oxidized in V ⁵⁺ to give vanadate.

In step b), the oxidizing atmosphere may be pure oxygen, air, or a mixture of oxygen and an inert gas. Preferably, the inert gas is nitrogen gas. In the present invention, during firing, the temperature and time suitable for firing can be selected within the range, for example, when the firing temperature is high (such as 950 ° C), the firing time can be shortened (such as 60 minutes), and when the firing temperature is low ( such as 860 ° C), the firing time may be longer (approximately 240 min).

Preferably, in step c), the calcined product is cooled and sprayed to 0.18 mm or less to facilitate leaching before suspension.

Preferably, in step c), a suspension is prepared by mixing the calcined product with water in an amount that is a multiple of 1.5-4 by weight. The water used is the washing water obtained by washing the residue, and if the washing water is insufficient, circulating water is used to replenish. The leaching solution of sulfuric acid has a concentration of 10-75%, the leaching temperature is between room temperature and 58 ° C, and the leaching time is 30-90 minutes. More preferably, the pH of the suspension is controlled in the range of 2.8-3.3 with a solution of sulfuric acid 32-65 wt.%.

During the washing of the residue, it is preferable that the washing is carried out 5-7 times, the amount of water used for each washing is preferably 20-35 wt.% Of the residue, counting on a dry basis, in order to maintain the water balance in the circulating method.

The P removal reagent can be used for P-removal treatment to satisfy TV / P≥1000.

In step e), the ammonium salt is preferably ammonium sulfate, ammonium bisulfate, ammonium carbonate or ammonium bicarbonate. Circulating water obtained from treated wastewater after vanadium precipitation contains an ammonium salt, when circulating water containing a salt such as (NH ₄ ) ₂ SO ₄ is used for leaching within the leaching condition of the present invention, NH ₄ ⁺ does not adverse effect and SO ₄ ^2- is useful for improving the degree of leaching of the calcareous calcine. Since Cl ^- and NO ₃ ^- are usually readily soluble substances that are difficult to discharge and will affect the quality of the product, and Cl ^- and NO ₃ ^- in the circulating water must be removed before using the circulating water, but the removal of Cl ^- and NO ₃ ^- is difficult and involves high costs, (therefore) ammonium chloride and ammonium nitrate cannot be used.

In step e), when the NH ₃ / Mn mass ratio is low, the deposition time will be increased, but a high quality product can be obtained; when the NH ₃ / Mn mass ratio is high, the deposition will end quickly, the energy consumption can be significantly reduced and the product yield will be increased, therefore, for the final action, the amount of added ammonium salt provides the NH ₃ / Mn mass ratio in the leachate, preferably in the range of 0.7 -1.0: 1. Since the returned circulating water contains some NH ₄ ⁺ , if the mass ratio of NH ₃ / Mn in the leachate after P removal already satisfies the above requirement, the ammonium salt is not added and vanadium is directly precipitated.

Preferably, in step e), the washing of the precipitate with water is carried out 2-4 times and the amount of water for each washing is 25-40% by weight of the precipitate, based on a dry basis.

In step g), the wastewater can be treated according to various routine methods to remove P, Mn and Mg. For example, milk of lime is used to neutralize wastewater to a pH of 9-11, the wastewater is filtered to remove major impurities such as Mn, P and Mg, while at the same time obtaining a neutralization residue of wastewater suitable as a starting material for the extraction of Mn, or Mn can be separately recovered by other reagents and then impurities like P and Mn can be removed.

The present invention has the following beneficial effects.

1. The method of the invention adheres to the liming calcination method and the sulfuric acid leaching method to produce a vanadium solution substantially free of alkali metal ions, and various starting materials (including added water) are substantially free of readily soluble alkali metal, halogen and nitrate ions, so that during circulation, the balance of readily soluble ions can be maintained and the problems of wastewater treatment of a conventional vanadium extraction method using a sodium salt can be eliminated.

2. Ammonium salt is used to obtain a high-quality vanadium oxide product, so the technical problem is solved, which cannot be obtained by the conventional method of calcination — lime leaching of a high-quality vanadium product by sulfuric acid.

3. The NH ₃ / Mn mass ratio is adjusted to control product quality and the concentration of ammonium in the solution, when such a ratio in the leach product is lower than the value specified in the present invention, an ammonium salt is added to adjust the ratio to the specified value, and then vanadium is precipitated ; when the ratio in the leachate has already reached the indicated value in the present invention, the ammonium salt is not added and vanadium is directly precipitated, and part of the NH ₄ ^{+ is} discharged together with the ammonium polyvanadate precipitate, so that the NH ₄ ⁺ concentration in the system will not continuously increase to ensure circulation and reuse.

4. Use circulating water containing a sulfate salt, such as (NH ₄ ) ₂ SO ₄ , for leaching; in the range of leaching conditions of the present invention, NH ₄ ⁺ will not have an adverse effect and SO ₄ ^2- is useful for increasing the rate of leaching of the calcareous calcine, so that water can be circulated and reused as a result.

5. The method of the invention can significantly increase the total degree of extraction (up to 85-88%) of vanadium oxide from vanadium slag, at the same time, the degree of extraction by the conventional method of vanadium extraction using sodium salt is approximately 80%; therefore, the method of the invention has an increased recovery rate of 5-8% on average compared to the conventional vanadium extraction method using the sodium salt, and the resulting vanadium product is of good quality and complies with Chinese National Standard No. GB3283-87.

6. An inexpensive substance, lime, is used to replace expensive sodium carbonate, the amount of sulfuric acid consumed is similar to the amount in the vanadium extraction method using sodium salt, and NH ₄ ^{+ is} almost completely consumed to precipitate vanadium, while the largest amount of ammonia in conventional wastewater a method for extracting vanadium using sodium salt is lost in wastewater treatment; therefore, the consumption and cost of various auxiliary and starting materials is significantly reduced.

Brief Description of the Drawings

1 is a flow chart of one preferred embodiment of the method of the present invention.

Preferred Embodiments

The present invention will now be described by the following examples.

All of the following examples follow a process sequence as shown in FIG. 1. Preferred examples are briefly described in conjunction with FIG.

First, vanadium slag and lime are mixed to obtain a mixed substance (equivalent to stage a);

the mixed substance is calcined and calcined (equivalent to step b);

a solution of sulfuric acid is used to leach the calcined product at a constant pH (equivalent to step c);

after leaching, the residue and the leaching product are separated, the residue is washed with a dilute solution of sulfuric acid, pH 3-6, and the wash water is collected to prepare a suspension (equivalent to stage d);

ammonium salt and sulfuric acid are added to the leach product to precipitate vanadium (equivalent to step e);

ammonium polyvanadate obtained by precipitation of vanadium is calcined or reduced to produce high-quality vanadium oxide (equivalent to step f);

add the wastewater obtained by precipitation of vanadium with milk of lime to neutralize, the resulting circulating water is returned for suspension or washing the residue and Mn is removed from the neutralization residue (equivalent to step g).

Example 1

The calcined product obtained according to step (1) is used, 51 cycles of the wastewater circulation test are carried out according to the method of the invention, and each cycle includes steps (2) to (5).

(1) Obtaining a firing product

Conventional vanadium slag with the composition shown in Table 1 is ground to less than 0.098 mm, 28 kg of ground vanadium slag powder is mixed with 1.96 kg of lime (ground to less than 0.1 mm) containing CaO≥98% and then the mixture is fired at 860 ° C in air for 240 minutes, cool and grind to less than 0.18 mm.

Table 1 The main components of vanadium slag (%) V ₂ O ₅ Cao MnO P K + Na 16.67 3,54 9.14 0.04 0.21

(2) Leaching of the firing product

2000 ml of water obtained by washing the remainder of the last cycle (pure water is used for the first cycle) is added to 500 g of the crushed calcined product to prepare a suspension, 10-32 wt.% Sulfuric acid solution is slowly added continuously, along with stirring during the method leaching regulate the pH in the range of 2.8-3.3, at the same time, the suspension temperature is maintained at a temperature between room temperature and 58 ° C, the reaction is carried out for 60 minutes The resulting product is filtered to obtain a leach product, the residue is washed with circulating water (pure water is used for the first cycle) 6-7 times, the water used for each time is 120 ml, the washing water is combined to prepare a leach suspension in the next cycle and the residue is dried and weighed to determine the content of TV (total vanadium), the degree of leaching of vanadium is calculated. The leachate is subjected to a P-removal treatment to satisfy the TV / P≥1000 inequality, and a vanadium precipitation procedure is carried out.

(3) Precipitation of vanadium

The ammonium salt is added to the leached product with removed P to obtain a mass ratio of NH ₃ / Mn solution in the range of 0.3-0.9, a small amount of sulfuric acid is used to adjust the pH in the range of 1.5-2.5, then the resulting the product is heated above 90 ° C, kept for 60-120 min and filtered, the precipitate is washed with discharged water containing [Na + K] ≤0.1 g / l, 3 times, the water used for each time is 30 ml, and the wash Wastewater is combined with liquid over a vanadium sludge to produce vanadium sedimentation wastewater and I.

(4) Obtaining V ₂ O _{5 by} calcination

The precipitate of ammonium polyvanadate is dried, calcined and alloyed at 500-800 ° C to obtain V ₂ O ₅ and the composition of the obtained V ₂ O _{5 is} analyzed.

(5) Wastewater treatment

A low-water lime milk is prepared, vanadium precipitation is added to the wastewater to adjust the pH of the solution in the range of 9.0-10.0 and filtered. The filtrate is adjusted to pH 5-7 with dilute sulfuric acid to obtain circulating water as residual wash water for leaching in the next cycle. The neutralization residue obtained by filtration is used as starting material for the extraction of Mn.

The above steps (2) to (5) are repeated, 500 g of the firing product is used in each cycle, the liquid-solid ratio for each cycle is 4: 1, vanadium is not precipitated after leaching in the first cycle, the leaching product is used to prepare a suspension of the second a cycle to increase the concentration of vanadium in the leachate; then, during leaching in each of the remaining cycles, the residual washing water from the last cycle is used in stage (2) and the remaining part is replenished with circulating water; Circulating water is used to wash the residue, and the missing part is replenished with clean water. Carry out 51 cycles and do not discharge waste water containing ammonia nitrogen from the system.

In addition to the first cycle without vanadium precipitation, the maximum value, minimum value and average value of the degree of extraction from the remaining cycles are presented in table 2; the maximum value, minimum value and average value for chemical compositions of the product V ₂ O ₅ from the remaining cycles are presented in table 3, table 3 also shows the metallurgical compositions No. 98 and No. 99 Chinese National Standard No. GB3283-87; the maximum value, minimum value and average value for the composition of the circulating water after the circulation treatment for the remaining cycles are presented in table 4.

table 2 The degree of extraction of vanadium in the circulation method (%) Operation Pretreatment of the starting material Leaching Vanadium precipitation Removal of ammonia by calcination Total Extraction Rate Minimum 91.42 98.47 Maximum 98.50 96.23 99.42 97.00 88.40 Average 93.48 98.97

The degree of extraction of the pre-treated starting material and the removal of ammonia by calcination in Table 2 above is obtained from long-term industrial production data.

Note: the pretreatment operation of the starting material involves spraying a mass of untreated vanadium slag, grinding and removing iron, and a small amount of vanadium is lost in this method.

Based on table 2, it can be noted that the total average degree of extraction of V ₂ O ₅ from vanadium slag by the method of the invention reaches 84.40%.

Table 3 The main components of the product V ₂ O ₅ obtained by the circulation method (%) Components V ₂ O ₅ Mn Mg Ca TFe P S Si Na ₂ O + K ₂ O Minimum 98.98 0.05 <0.01 0,03 0,07 <0.01 0.01 <0.01 0.17 Maximum 99.48 0.13 0.01 0.10 0.10 0,03 0,03 0.01 0.28 Average 99.22 0.09 0.01 0.06 0.08 0.02 0.02 0.01 0.22 GB3283-87 Metallurgical 98 > 98 ≯0.03 ≯0.05 ≯0.03 ≯0.25 ≯1.5 GB3283-87 metallurgical 99 > 99 ≯0.2 ≯0.03 ≯0.01 ≯0.15 ≯1.0

Table 3 shows that the vanadium product obtained by this method is a good quality product and complies with Chinese National Standard No. GB3283-87.

Table 4 Main components of circulating water (g / l) Line items Mn Mg NH ₄ ⁺ Na + K Ca SO ₄ ^2- P Al Si TFe TCr Minimum 1.46 1.31 1.75 0.22 0.55 17.68 <0.005 Maximum 3.22 4.29 5.94 0.39 0.83 37.16 Average 2,38 2.86 3.93 0.31 0.70 27.81 <0.005

From table 4 it can be seen that after 51 cycles of wastewater circulation there is no tendency to accumulate various impurities and the circulation and reuse of low cost vanadium extraction wastes, where K and Na are mainly from the starting material of vanadium slag and the sum of K + Na in the circulation water stabilizes within 0.2-0.4 g / l and does not increase after 51 cycles.

Example 2

A calcined substance obtained according to step (1) is obtained, 51 cycles of a wastewater circulation test are carried out according to the method of the invention, and each cycle includes steps (2) to (5).

(1) Obtaining a calcined substance

The vanadium slag shown in Table 5 is pulverized to less than 0.098 mm.

Table 5 The main components of vanadium slag (%) V ₂ O ₅ Cao Mn P K + Na 13.75 4.93 6.56 0,049 0.19

28 kg of powder of crushed vanadium slag is mixed with 1.82 kg of lime (crushed to less than 0.1 mm) containing 98% CaO, and then the mixture is calcined at 950 ° C in air for 60 minutes, cooled and crushed to less than 0 , 18 mm.

(2) Leaching of firing substance

1250 ml of the water obtained by washing the remainder of the last cycle (pure water is used for the first cycle) is added to 500 g of the ground firing product for suspension preparation, 32-65 wt.% Sulfuric acid solution is slowly added continuously, along with stirring, adjust the pH to the range of 2.8 -3.3 during the leaching process, at the same time, the suspension temperature is maintained at a temperature between room temperature and 58 ° C, the reaction is carried out for 60 minutes The resulting product is filtered to obtain a leach product, the residue is washed with circulating water (pure water is used for the first cycle) 6 times, the water used each time is 120 ml, the washing water is combined to prepare the leach suspension in the next cycle, and the residue is dried and weighed to determine the content TV (total vanadium) and the calculation of the degree of leaching of vanadium. The leachate is subjected to a P-removal treatment so that the inequality TV / P≥1000 is satisfied and the vanadium precipitation process is carried out.

(3) Precipitation of vanadium

After P removal, ammonium sulfate is added to the leachate to obtain a mass ratio of NH ₃ / Mn in the solution in the range of 0.6-3.0, a small amount of sulfuric acid is used to adjust the pH in the range of 1.5-2.5, then the resulting solution is heated above 90 ° C, kept for 60-90 minutes and filtered, the precipitate is washed with discharged water containing [Na + K] ≤0.1 g / l, 3 times, each time the water used was 30 ml, and the washing wastewater is combined with the liquid over the vanadium sludge to obtain vanadium precipitation wastewater I am.

(4) Obtaining V ₂ O _{5 by} calcination

The ammonium polyvanadate precipitate is dried, calcined and fused at 500-800 ° C to obtain V ₂ O ₅ and the composition of V ₂ O _{5 is} analyzed.

(5) Wastewater treatment

A low-water lime milk is prepared, vanadium precipitation is added to the wastewater to adjust the pH of the solution in the range of 9.0-9.5 and filtered. In the filtrate, the pH is adjusted in the range of 5-7 with diluted sulfuric acid to obtain circulating water as water for washing the residue for leaching in the next cycle. The neutralization residue obtained after filtration is used as starting material for the extraction of Mn.

The above steps (2) to (5) are repeated, 500 g of the calcined substance is used in each cycle, the liquid-solid ratio for each cycle is 4: 1, vanadium is not precipitated after leaching in the first cycle, the leaching product is used to prepare a suspension of the second cycle to increase the concentration of vanadium in the leachate, then during leaching in each of the remaining cycles, the washing water of the remainder of the last cycle is used in stage (2) and the missing part is supplemented with circulating water; circulating water is used to wash the residue and supplement the missing part with clean water. Carry out 51 cycles and do not discharge waste water containing ammonia nitrogen from the system.

Excluding the first cycle without vanadium precipitation, the maximum value, minimum value and average value of the degree of extraction in the remaining cycles are shown in table 6; the maximum value, minimum value and average value for chemical compositions of the product V ₂ O ₅ in the remaining cycles are shown in table 7; the maximum value, minimum value and average value for the composition of the circulating water after the circulation treatment for the remaining cycles are shown in table 6.

Table 6 The degree of extraction of vanadium in the circulating method (%) Operation Pretreatment of the starting material Leaching Vanadium precipitation Removal of ammonia by calcination Total Extraction Rate Minimum 90.62 98.47 Maximum 98.50 94.29 99.42 97.00 87.21 Average 92.30 98.97

The degrees of extraction of the pre-treated starting material and the removal of ammonia by calcination in the above table 6 are obtained from long-term industrial production data.

Based on table 6, it can be noted that the total average degree of extraction of V ₂ O ₅ from vanadium slag by the method of the invention reaches 87.21%.

Table 7 The main components of the product V ₂ O ₅ obtained by the circulation method (%) Line items V ₂ O ₅ Mn Mg Ca TFe P S Si Na ₂ O + K ₂ O Minimum 98.83 0.05 <0.01 0.05 0.06 <0.01 0.01 <0.01 0.14 Maximum 99.54 0.11 0.02 0.08 0.09 0.02 0,03 0.01 0.26 Average 99.24 0.08 0.01 0,07 0.08 0.02 0.02 0.01 0.20

Table 7 shows that the vanadium product obtained by this method has good product quality and complies with Chinese National Standard No. GB3283-87.

Table 8 Main components of circulating water (g / l) Position Mn Mg NH ₄ ⁺ Na + K Ca SO ₄ ^2- R Si Al TFe TCr Minimum 1.72 1.71 1.95 0.23 0.58 19.24 <0.005 Maximum 4.98 3.98 9.72 0.33 0.75 47.88 Average 3.22 2.75 5.52 0.28 0.66 32.41 <0.005

Based on table 8, it can be noted that after 51 cycles of wastewater circulation, various impurity ions do not tend to accumulate, and low-cost vanadium extraction wastewater is circulated and reused, where K and Na are present mainly from the starting material of vanadium slag and the sum of K + Na in the circulation water is stabilized within 0.2-0.4 g / l and does not increase after 51 cycles.

Example 3

A calcined substance is obtained according to step (1), 100 cycles of a wastewater circulation test are carried out according to the method of the invention, and each cycle includes steps (2) to (5).

(1) Obtaining a calcined substance

110 kg of vanadium slag with the composition shown in Table 9 are crushed to less than 0.098 mm, the powder of crushed vanadium slag is mixed with 7.7 kg of lime (crushed to less than 0.1 mm) containing 98% CaO, and then the mixture is calcined at 920 ° C in air for 150 minutes, cool and grind to less than 0.18 mm.

Table 9 The main components of vanadium slag (%) V ₂ O ₅ Cao Mn P K + Na 12.68 2.15 5.98 0.147 0.18

(2) Leaching of the calcined substance

2000 ml of water obtained by washing the remainder of the last cycle (pure water is used for the first cycle), add to 1000 g of crushed calcined material for suspension, slowly add 50-75 wt.% Sulfuric acid solution, while stirring, while the time of the leaching method, the pH is regulated in the range of 2.8-3.3, at the same time, the suspension temperature is maintained at a temperature between room temperature and 58 ° C, the reaction is carried out for 60 minutes The resulting product is filtered to obtain a leach product, the residue is washed with circulating water (pure water is used for the first cycle) 5-6 times, the water used for each time is 250 ml, the washing water is combined to prepare a leach suspension in the next cycle and the residue is dried and weighed to determine the content of TV (total vanadium) and the degree of leaching of vanadium is calculated. The leachate is subjected to P-removal treatment to obtain P satisfying the inequality TV / P≥1000, and the vanadium precipitation procedure is carried out.

(3) Precipitation of vanadium

After removal of P, ammonium sulfate is added to the leachate to obtain a mass ratio of NH ₃ / Mn in solution in the range of 0.7-0.9, a small amount of sulfuric acid is used to adjust the pH in the range of 1.5-2.5, then obtained in as a result, the product is heated above 90 ° C, kept for 30-60 minutes and filtered, the precipitate is washed with discharged water containing [Na + K] ≤0.1 g / l, 3 times, and each time the water used is 60 ml, and washing wastewater is combined with the liquid over the vanadium sludge to obtain vanadium precipitation wastewater and I.

(4) Obtaining V ₂ O _{5 by} calcination

The ammonium polyvanadate precipitate is dried, calcined and fused at 500-800 ° C. to obtain V ₂ O ₅ , and the composition of V ₂ O _{5 is} analyzed.

(5) Wastewater treatment

A low-water lime milk is prepared, vanadium precipitation is added to the wastewater to adjust the pH of the solution in the range of 9.0-10.0, and is filtered. In the filtrate, adjust the pH in the range of 5-7 with dilute sulfuric acid to obtain circulating water as the washing water of the leach residue in the next cycle. The neutralized residue obtained by filtration is used as starting material for the extraction of Mn.

The above steps (2) to (5) are repeated, 1000 g of the calcined substance is used in each cycle, the liquid-solid ratio for each cycle is 2: 1, vanadium is not precipitated after leaching in the first cycle, the leaching product is used to prepare the suspension in a second cycle to increase the concentration of vanadium in the leachate; then during leaching in each of the remaining cycles, water for washing the remainder of the last cycle is used in stage (2) and the missing part is supplemented with circulating water; circulating water is used to wash the residue and supplement the missing part with clean water. Carry out 100 cycles and do not unload wastewater containing ammonia nitrogen from the system.

Excluding the first cycle without vanadium precipitation, the maximum value, minimum value and average value of the degree of extraction in the remaining cycles are shown in table 10; the maximum value, minimum value and average value for the chemical composition of the product V ₂ O ₅ in the remaining cycles are shown in table 11 and the maximum value, minimum value and average value for the composition of the circulation water after circulation treatment for the remaining cycles are shown in table 12.

Table 10 The degree of extraction of vanadium in the circulation method (%) Procedure Pretreated starting material Leaching Vanadium precipitation Removal of ammonia by calcination Total Extraction Rate Minimum 89.97 98.76 Maximum 98.50 92.61 99.45 97.00 86.39 Average 91.31 99.02

The degree of extraction of the pre-treated starting material and the removal of ammonia by calcination in the above table are obtained from long-term industrial production data.

Based on table 10, it can be noted that the total average degree of extraction by the method of the invention of V ₂ O ₅ from vanadium slag reaches 86.39%.

Table 11 The main components of the product V ₂ O ₅ obtained by the circulation method (%) Position V ₂ O ₅ Mn Mg Ca TFe P S Si Na ₂ O + K ₂ O Minimum 98.85 0.06 <0.01 0,03 0.05 <0.01 0.01 <0.01 0.16 Maximum 99.35 0.12 0.02 0.09 0.10 0.01 0,03 0.02 0.29 Average 99.12 0.09 0.01 0.05 0.08 0.01 0.01 0.01 0.20

Table 11 demonstrates that the vanadium product obtained by this method is of good quality and complies with Chinese National Standard No. GB3283-87.

Table 12 The main components of the circulating water (g / l) Position Mn Mg NH ₄ ⁺ Na + K Ca SO ₄ ^2- P Si Al TFe TCr Minimum 0.21 0.47 1,56 0.19 0.32 9.08 <0.005 Maximum 0.53 1.01 2,33 0.37 0.59 12.24 Average 0.36 0.72 1.91 0.27 0.44 10.53 <0.005

Based on table 12, it can be noted that after 100 cycles of wastewater circulation, various impurity ions do not tend to accumulate and low-cost vanadium extraction wastewater is circulated and reused, where K and Na are present mainly from the starting material of vanadium slag , and the sum of K + Na in the circulation water stabilizes within 0.2-0.4 g / l and does not increase after 100 cycles.

Claims (10)

1. The method of producing vanadium oxide, comprising the following stages:
but. mixing the vanadium-containing substance with the additive to obtain a mixed substance, where the additive is CaO or limestone, and the amount of the additive has a mass ratio of CaO / V ₂ O ₅ in the mixed substance equal to (0.5-1.4): 1;
b. calcining the mixed substance at 860-950 ° C in an oxidizing atmosphere for 60-240 minutes to obtain a calcination product;
from. adding water to the calcined product to prepare the suspension, mixing and slowly adding a solution of sulfuric acid to leach the suspension, while adjusting the pH in the range of 2.5-3.5;
d. removing the residue after leaching to obtain a leach product, exposing the leach product to a P-removing treatment to obtain a mass ratio of total V to P in the leach product of ≥1000, washing the residue with circulating water to obtain a wash water used to prepare a suspension in the next leach;
E. the addition of an ammonium salt in the leach product with the removed P to obtain a mass ratio of NH ₃ / Mn in the leach product of (0.3-3.0): 1, adjusting the pH of the solution with sulfuric acid in the range of 1.5-2.5 heating to a temperature of 90 ° C to a boiling point, keeping at this temperature for 30-120 minutes, filtering and washing and drying the precipitate to obtain ammonium polyvanadate;
f. exposure of the ammonium polyvanadate to calcination to remove ammonia to produce V ₂ O _5; or the reduction of ammonium polyvanadate to produce V ₂ O ₃ ; and
g. removal of impurities P, Mn and Mg in the wastewater formed in stage e, with obtaining concentrations of Mn ²⁺ and Mg ²⁺ lower than 5 g / l, respectively, and a concentration of P lower than 0.005 g / l, with obtaining circulating water and returning the circulating water to stage c for preparing the suspension and to stage d for washing the residue, where the solid starting material used in the above stages has a total amount of alkali metal of not more than 0.3 wt.% and a total amount of Cl ^- and NO ₃ ^- not more than 0.1 wt.%, And the liquid starting material used in in the above steps, has a total amount of alkali metal of not more than 0.1 g / L, and the total amount of Cl ^- and NO ₃ ^- is not more than 0.1 g / L. 2. The method of producing vanadium oxide according to claim 1, where the mixed substance obtained in stage a has a particle size of 0.1 mm or less. 3. The method of producing vanadium oxide according to claim 1, where in step c, the calcined product is cooled and sprayed to a size of 0.18 mm or less before preparing the suspension. 4. The method of producing vanadium oxide according to claim 1, where in step c, the concentration of the sulfuric acid solution is 10-75 wt.%, The leaching temperature is from room temperature to 58 ° C and the leaching time is 30-90 minutes 5. The method of producing vanadium oxide according to claim 1, where the circulating water obtained in stage g is returned to stage d to wash the residue to obtain washing water, the washing water is returned to stage c for leaching and suspension, if the washing water is insufficient, apply circulating water to replenish. 6. The method of producing vanadium oxide according to claim 1 or 5, where in step c, the mass ratio of the total amount of water for preparing the suspension to the calcined product is (1.5-4): 1. 7. The method of producing vanadium oxide according to claim 1, where during washing the residue, the number of washes is 5-7 times, and the amount of water used for each washing is 20-35 wt.% Of the residue, based on a dry base. 8. The method of producing vanadium oxide according to claim 1, where in stage e, the amount of added ammonium salt provides a mass ratio of NH ₃ / Mn in the leachate in the range (0.7-1.0): 1. 9. The method of producing vanadium oxide according to claim 1 or 8, wherein in step e, the ammonium salt is ammonium sulfate, ammonium bisulfate, ammonium carbonate or ammonium bicarbonate. 10. The method of producing vanadium oxide according to claim 1, where in stage e, the water for washing the precipitate is discharged water or process water, the number of washes is 2-4 and the amount of water used for each washing is 25-40% of the precipitate, counting on a dry basis.

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