CN108611503B - Method for decomposing wolframite and preparing tungsten oxide and tungsten powder by oxygen pressure - Google Patents

Method for decomposing wolframite and preparing tungsten oxide and tungsten powder by oxygen pressure Download PDF

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CN108611503B
CN108611503B CN201810361940.1A CN201810361940A CN108611503B CN 108611503 B CN108611503 B CN 108611503B CN 201810361940 A CN201810361940 A CN 201810361940A CN 108611503 B CN108611503 B CN 108611503B
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陈星宇
刘旭恒
赵中伟
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Central South University
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Abstract

The invention relates to a method for decomposing wolframite by oxygen pressure and preparing tungsten oxide and tungsten powder, which takes the wolframite as a raw material and comprises the following steps: (1) carrying out oxygen pressure leaching reaction; (2) filtering and washing; (3) extracting and decomposing hydrogen peroxide to extract tungsten; (4) extracting and decomposing hydrogen peroxide for multiple times to purify tungstic acid; (5) calcining pure tungstic acid to prepare tungsten trioxide; (6) and (3) preparing tungsten oxide and tungsten powder by spray pyrolysis of a peroxytungstic acid solution. The acid decomposition reagent adopted by the method is cheap and easy to obtain, so that the tungsten ore decomposition cost is greatly reduced; acid is adopted to decompose under the condition of oxygen pressure, no dangerous waste alkali cooking residue is generated, and the production and operation cost of enterprises is greatly reduced; hydrogen peroxide is used as an extractant of tungstic acid, ammonia nitrogen wastewater is not generated, a process for generating ammonia nitrogen wastewater for years in tungsten smelting is eliminated, and the environmental protection cost is greatly reduced; directly produce various tungsten end products (tungsten oxide) and tungsten powder, and improve the added value of products of tungsten smelting enterprises.

Description

Method for decomposing wolframite and preparing tungsten oxide and tungsten powder by oxygen pressure
Technical Field
The invention relates to the field of chemical production, in particular to a method for decomposing wolframite by oxygen pressure and preparing tungsten oxide and tungsten powder.
Background
At present, the mainstream technology for industrially treating wolframite is to firstly use sodium hydroxide to press and boil to obtain a crude sodium tungstate solution and alkaline boiled slag. The crude sodium tungstate solution is diluted by adding a large amount of water and then converted into an ammonium tungstate solution by an ion exchange technology, and the ammonium tungstate solution is also converted by adopting a solvent extraction method. This mainstream technology currently faces several serious problems: firstly, alkali such as sodium hydroxide or sodium carbonate is consumed for alkali pressure cooking, the price of the reagents is expensive at present, and particularly the price of the sodium hydroxide reaches 5000-6000 RMB/ton, so that the decomposition cost of the wolframite is high; secondly, alkaline pressure boiling generates alkaline boiling slag which is listed as a national hazardous waste catalogue at present, tungsten smelting enterprises cannot process the alkaline boiling slag randomly and must give the alkaline boiling slag to qualified enterprises for paid processing, and the country also collects 2000 yuan/ton of environment-friendly tax on the generated dangerous alkaline boiling slag, so that the cost of tungsten smelting is greatly increased; thirdly, in order to produce tungsten products with qualified impurity content, ammonia reagents such as ammonia water or ammonium chloride and the like are also required to be used as transformation reagents in the existing tungsten smelting process, so that a large amount of ammonia nitrogen wastewater is inevitably generated in the production process, and the environment is polluted. In order to solve the economic and environmental problems faced by the current tungsten smelting, a new tungsten smelting technology needs to be developed urgently.
In order to reduce the decomposition cost of tungsten ore and not generate dangerous waste alkali boiling slag and can not adopt an alkaline reagent to decompose the wolframite, only an acidic reagent can be adopted to decompose the tungsten ore. In fact, hydrochloric acid and nitric acid have long been used for decomposing wolframite, but the decomposition effect is limited; the bin and the like adopt sulfuric acid to decompose the mixed black-white tungsten ore, and the black tungsten ore in the mixed black-white tungsten ore is not decomposed partially under the optimized experimental conditions. Tungsten ore is converted into tungstic acid after acid decomposition. In order to prepare a qualified tungsten product, the tungstic acid generated by conversion is usually dissolved by ammonia water to obtain an ammonium tungstate solution, and ammonium carbonate is also used for dissolving the tungstic acid to obtain the ammonium tungstate solution. When the acid decomposition residue is subjected to ammonia or ammonium carbonate dissolution washing, ammonia-nitrogen-containing wastewater is inevitably generated. Ammonium tungstate obtained by dissolution is dissolved and then is evaporated and crystallized to prepare APT, a large amount of ammonia-containing steam is generated in the process, and a special device is needed for absorbing ammonia gas. Some enterprises adopt hydrochloric acid to absorb ammonia gas and then merge the ammonia gas into the wastewater to form high-concentration ammonia nitrogen wastewater. The crystallization mother liquor is a saturated ammonium tungstate solution, and ammonia nitrogen wastewater can be generated when tungsten is treated and recovered. At present, the environmental protection is extremely strict to the discharge control of the ammonia nitrogen wastewater in tungsten smelting, the discharge of the ammonia nitrogen wastewater reaching the standard is required, the input of ammonia nitrogen wastewater treatment is required to be increased, and the production cost of enterprises is inevitably increased. In addition, in order to produce the subsequent tungsten product (tungsten oxide), tungsten powder or tungsten carbide, the initial product APT of tungsten must be subjected to a calcination process. And a large amount of ammonia-containing waste gas is generated in the calcining process, the air can be directly polluted without treatment, and the ammonia-containing waste gas can be discharged after being absorbed by a special device and subjected to harmless treatment. Therefore, the existing tungsten smelting process cannot avoid the generation of ammonia nitrogen, so that the ammonia nitrogen pollution is inevitably caused to a certain extent.
In the traditional tungsten smelting process based on the acid method, ammonia is introduced to facilitate the separation of tungstic acid from other impurities. The ammonia water or ammonium carbonate is a weak base, so that other impurities are difficult to dissolve while the tungstic acid is dissolved, and the selective dissolution of the tungstic acid is facilitated. Since ammonia causes ammonia nitrogen pollution and cannot be used, and researches have long shown that hydrogen peroxide has strong complexing ability to tungsten, a certain amount of hydrogen peroxide is added in the process of acid decomposition of tungsten ore to form soluble peroxytungstic acid, so that the influence of tungstic acid wrapping formed in the decomposition process on the acid decomposition of the scheelite is avoided. Patent document CN105200246A describes that a mixed solution of sodium tungstate and sodium molybdate can be dissolved and acid-decomposed with hydrogen peroxide to obtain a mixed acid of tungstic acid and molybdic acid. The tungstic acid and molybdic acid dissolved by the hydrogen peroxide are relatively pure, only contain sodium ions which are not easy to wash, and have no other impurities, so the hydrogen peroxide is relatively easy to dissolve. The invention mainly aims to separate tungsten and molybdenum according to the stability difference of peroxytungstic acid and peroxymolybdic acid in an acid solution, and a tungsten purification method is not involved.
The Fengguan and the like are prepared by adding a certain amount of hydrogen peroxide into a sodium tungstate solution, regulating the acidity of the solution, and then decomposing peroxytungstate radicals, and then preparing tungstic acid, Guo-jin and the like are prepared by mixing tungstic acid and hydrogen peroxide into a precursor solution with the concentration of only 0.005 mol/L, and then the precursor solution is sprayed onto an ITO glass substrate at 250 ℃ through ultrasonic spray pyrolysis to obtain a tungstic acid film firstly, and then the tungstic acid film can be obtained through subsequent heat treatment at 550 ℃, and the essence of the process is a method for preparing the tungstic acid film through spray pyrolysis.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for extracting tungsten from wolframite.
Specifically, the invention provides a method for decomposing wolframite and preparing tungsten oxide and tungsten powder by oxygen pressure, and the flow diagram of the method can be referred to as figure 1.
The method comprises the following steps:
(1) oxygen pressure leaching reaction: adding wolframite into an acid solution, and carrying out leaching reaction under the condition of introducing oxygen;
(2) filtering and washing: filtering the reaction product obtained in the step (1) to obtain decomposition slag and leachate; adding acid into the leachate, and returning to the step (1) to be used as a raw material for leaching reaction;
(3) hydrogen peroxide extraction-decomposition extraction of tungsten: washing the decomposition residue obtained in the step (2), mixing the decomposition residue with a hydrogen peroxide solution to perform tungsten extraction reaction, and filtering a reaction product to obtain a peroxytungstic acid solution; heating the peroxytungstic acid solution or introducing SO2Until the peroxytungstic acid is completely decomposed to separate out tungstic acid;
(4) extracting hydrogen peroxide for multiple times, decomposing and purifying tungstic acid: detecting the impurity content in the tungstic acid obtained in the step (3), directly using the tungstic acid in the subsequent step if the impurity content meets the standard requirement, adding a hydrogen peroxide solution and repeating the operation of the step (3) at least once if the impurity content exceeds the standard requirement until the tungstic acid with the impurity content meeting the standard requirement is obtained;
treating the tungstic acid with the impurity content meeting the standard requirement by adopting the following steps (5) or steps (6) to (7):
(5) calcining pure tungstic acid to prepare tungsten trioxide: calcining tungstic acid with impurity content meeting the standard to obtain powdery tungsten trioxide;
(6) spray pyrolysis of a peroxytungstic acid solution to prepare tungsten oxide and tungsten powder: mixing tungstic acid with impurity content meeting the standard requirement with a hydrogen peroxide solution to perform tungsten extraction reaction to obtain a pure peroxytungstic acid solution;
(7) carrying out ultrasonic spray pyrolysis on the pure peroxytungstic acid solution under a non-reducing condition to obtain superfine spherical tungsten trioxide; and/or carrying out ultrasonic spray pyrolysis on the pure peroxytungstic acid solution under a reducing condition to obtain superfine spherical blue tungsten oxide, purple tungsten oxide and/or tungsten powder.
The grade of the raw material wolframite is 10-70%; the particle size of the wolframite is less than 300 mu m.
In the oxygen pressure leaching reaction in the step (1), the acid is sulfuric acid, hydrochloric acid or nitric acid with the concentration of 50-500 g/L, a certain amount of solid tungstic acid can be added in the reaction process, the addition amount is 0-20% of the weight of the wolframite, the liquid-solid ratio of the reaction in the step is preferably 3: 1-10: 1, oxygen is introduced in the step to control the pressure to be 0.1-10 Mpa, as a preferred scheme, the reaction in the step (1) can be carried out at the temperature of 110-200 ℃ and the oxygen pressure of 0.1-10 Mpa, and the reaction time is preferably 1-6 hours.
In the filtration washing in the step (2) of the present invention: adding a certain amount of acid into the leachate to make the concentration of the acid liquor the same as that of the acid adopted in the step (1), and then returning to the step (1) to be used as a raw material for leaching reaction.
In the step (3) of extracting and decomposing the tungsten by using the hydrogen peroxide, the method comprises the following steps: the mass concentration of the hydrogen peroxide solution is 5-30%; the preferred molar ratio of the added amount of the hydrogen peroxide to the tungstic acid in the decomposition residue is 0.5-2: 1. As a preferable scheme, the extraction reaction is carried out for 10min to 2.0h at the temperature of 10 to 40 ℃. After the extraction reaction is finished, filtering the product to obtain a peroxytungstic acid solution and insoluble residues; if the insoluble slag also contains undecomposed wolframite, the insoluble slag can return to the leaching procedure of the step (1) for secondary leaching reaction. Then heating the peroxytungstic acid solution to 50-90 ℃, or directly introducing SO into the peroxytungstic acid solution2And controlling the concentration of sulfuric acid in the solution to be 0.5 mol/L-2.0 mol/L until the peroxytungstic acid is completely decomposed, and then the tungstic acid can be separated out.
The operation of extracting-decomposing and purifying tungstic acid by hydrogen peroxide for multiple times in the step (4) of the invention can be seen in different repetition times of the raw materials. When the wolframite grade is high, the impurity content in the tungstic acid crystal obtained in the step (3) can directly meet the standard requirement, and the tungstic acid crystal is directly used in the subsequent step, so that the purification process can be directly omitted; and (3) when the grade of the wolframite is low, if the impurity content in the tungstic acid crystal obtained in the step (3) exceeds the standard requirement, adding a hydrogen peroxide solution into the tungstic acid crystal, repeating the step (3) at least once, namely purifying by adopting hydrogen peroxide until the tungstic acid crystal with the impurity content meeting the standard requirement is obtained. According to the invention, after the impurity content in the tungstic acid crystal is controlled in the step (4), the calcination or pyrolysis is carried out in the subsequent steps, so that the final product has good yield and purity, the energy is saved, and the equipment is protected.
The standard of the impurity content can be manually made according to industrial production specifications or actual requirements of products, and the invention is not particularly limited. As a preferable scheme of the invention, the tungstic acid can be qualified when the content of impurity elements in the obtained tungstic acid meets the national standard GB/T10116-2007.
The qualified tungstic acid prepared by the steps has two optional modes for preparing the tungsten oxide product. Wherein, in the first mode, as described in the step (5), the tungsten trioxide is directly obtained by calcination; in the second mode, tungsten oxide and tungsten powder are prepared by spray pyrolysis as described in steps (6) to (7).
In the preparation of tungsten trioxide by calcining pure tungstic acid in the step (5) of the invention: the calcining temperature is 750-900 ℃. In the step, tungstic acid with impurity content meeting the standard requirement is calcined to prepare the powdery tungsten trioxide.
In the preparation of tungsten oxide and tungsten powder by spray pyrolysis of the peroxytungstic acid solution in the step (6) of the invention: adding the tungstic acid with the impurity content meeting the standard requirement into the hydrogen peroxide solution again (the mass concentration is 5-30%), and reacting to obtain the pure peroxytungstic acid solution (wherein WO)3The concentration is about 10 to 350 g/L).
In the step (7), the pure peroxytungstic acid solution is subjected to ultrasonic spray pyrolysis to obtain a superfine spherical product. Specifically, the ultrasonic spray pyrolysis can be carried out under non-reducing conditions to obtain ultrafine spherical tungsten trioxide; or under the reducing condition to obtain the superfine spherical blue tungsten oxide, or purple tungsten oxide, or tungsten powder.
In practical operation, inert gas (such as nitrogen or argon) can be introduced during ultrasonic spray pyrolysis, and the purpose of introducing the inert gas is to carry the inert gas into the solution for pyrolysis, as a preferable scheme, the spraying speed is 10-200 ml/min, the gas flow rate is 150-600 ml/L, the pyrolysis temperature is 500-900 ℃, and the superfine spherical tungsten trioxide powder can be obtained.
In practical operation, reducing gas (such as hydrogen) can be introduced during ultrasonic spray pyrolysis, so that pyrolysis is carried out under the reducing condition, as a preferred scheme, the spraying rate is 10-200 ml/min, the hydrogen flow rate is 50-600 ml/L, the pyrolysis temperature is 500-900 ℃, and ultrafine spherical purple tungsten oxide powder or ultrafine spherical blue oxide powder can be obtained.
The invention provides a brand-new method for decomposing wolframite and preparing tungsten oxide and tungsten powder by oxygen pressure, which has the following main advantages:
firstly, an acid decomposition reagent is cheap and easy to obtain, particularly, the decomposition reagent sulfuric acid is 200-500 yuan/ton, which is only 10% of the cost of a sodium hydroxide reagent, so that the decomposition cost of tungsten ore is greatly reduced;
secondly, acid is decomposed under the condition of oxygen pressure, no dangerous waste alkali cooking residue is generated, and the production and operation cost of enterprises is greatly reduced;
thirdly, hydrogen peroxide is used as an extractant of the tungstic acid, ammonia nitrogen wastewater is not generated, the process of continuously generating ammonia nitrogen wastewater for many years in tungsten smelting is eliminated, and the environmental protection cost is greatly reduced;
fourthly, the invention directly produces various tungsten end products (tungsten oxide) and tungsten powder, thereby improving the added value of products of tungsten smelting enterprises.
Drawings
FIG. 1 is a flow chart of the method of the present invention; in the drawings, the dashed arrows and the dashed boxes represent alternative parallel process routes.
Detailed Description
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Example 1
The embodiment provides a method for decomposing wolframite by oxygen pressure and preparing tungsten oxide and tungsten powder, the method adopts 40% grade wolframite with 120 μm granularity as raw material, the method specifically comprises the following steps:
(1) oxygen pressure leaching reaction, namely adding wolframite into sulfuric acid solution with the concentration of 200 g/L, wherein the liquid-solid ratio of the system is 6:1, introducing oxygen to control the oxygen pressure to be 5Mpa, and performing leaching reaction for 3 hours at the temperature of 150 ℃ to convert 99.4 percent of tungsten into tungstic acid;
(2) filtering and washing: filtering the reaction product obtained in the step (1) to obtain decomposition slag and leachate; supplementing sulfuric acid into the leachate, and returning to the step (1) to be used as a raw material for leaching reaction;
(3) hydrogen peroxide extraction-decomposition extraction of tungsten: washing the decomposed residue obtained in the step (2), mixing the washed decomposed residue with a hydrogen peroxide solution with the mass concentration of 30%, wherein the molar ratio of the added amount of hydrogen peroxide to tungstic acid in the decomposed residue is 1.5:1, carrying out tungsten extraction reaction for 1h at the temperature of 35 ℃, filtering a reaction product to obtain a tungstic acid peroxide solution and insoluble residue, and returning the insoluble residue containing undecomposed wolframite to the leaching process of the step (1) for secondary leaching reaction; heating the peroxytungstic acid solution to 80 ℃ until the peroxytungstic acid is completely decomposed to separate out tungstic acid; through detection, the content of impurity elements in the obtained tungstic acid meets the national standard GB/T10116-2007, and the tungstic acid can be directly used in the subsequent steps;
(4) washing the tungstic acid obtained in the step (3), and mixing the tungstic acid with a hydrogen peroxide solution with the mass concentration of 20% at the temperature of 25 ℃ for reaction for 1h to obtain a pure peroxytungstic acid solution again;
(5) and (3) carrying out ultrasonic spray pyrolysis on the pure peroxytungstic acid solution obtained in the step (4) under the conditions of introducing nitrogen, spraying speed of 120ml/min, nitrogen flow rate of 400 ml/L and pyrolysis temperature of 700 ℃ to obtain ultrafine spherical tungsten trioxide powder, wherein the content of impurities in the tungsten trioxide is detected to meet the requirements of national standard GB/T3457-grade 2013 (0-grade product).
Example 2
The embodiment provides a method for decomposing wolframite by oxygen pressure and preparing tungsten oxide and tungsten powder, the method adopts the wolframite with the grade of 10% and the granularity of 160 mu m as the raw material, and the method specifically comprises the following steps:
(1) oxygen pressure leaching reaction, namely adding wolframite into sulfuric acid solution with the concentration of 120 g/L, wherein the liquid-solid ratio of the system is 10:1, and performing leaching reaction for 1 hour at the temperature of 180 ℃ and under the condition of controlling the oxygen pressure to be 10Mpa, so that 99.5 percent of tungsten is converted into tungstic acid;
(2) filtering and washing: filtering the reaction product obtained in the step (1) to obtain decomposition slag and leachate; supplementing sulfuric acid into the leachate, and returning to the step (1) to be used as a raw material for leaching reaction;
(3) hydrogen peroxide extraction-decomposition extraction of tungsten: washing the decomposed residue obtained in the step (2), mixing the washed decomposed residue with a hydrogen peroxide solution with the mass concentration of 30%, wherein the molar ratio of the added amount of hydrogen peroxide to tungstic acid in the decomposed residue is 1:1, carrying out tungsten extraction reaction for 10min at the temperature of 40 ℃, filtering a reaction product to obtain a tungstic acid peroxide solution and insoluble residue, and returning the insoluble residue containing undecomposed wolframite to the leaching process of the step (1) for secondary leaching reaction; directly introducing SO into peroxytungstic acid solution2Controlling the concentration of sulfuric acid in the solution to be 1.5 mol/L until the peroxytungstic acid is completely decomposed to separate out tungstic acid;
(4) dissolving hydrogen peroxide for multiple times, decomposing and purifying tungstic acid: adding a hydrogen peroxide solution with the mass concentration of 30% into the tungstic acid obtained in the step (3), and repeating the operation of the step (3) once to obtain the tungstic acid with the impurity content meeting the standard requirement; when the content of impurity elements in the obtained tungstic acid meets the national standard GB/T10116-;
(5) washing the tungstic acid obtained in the step (4), and mixing the tungstic acid with a hydrogen peroxide solution with the mass concentration of 25% at the temperature of 30 ℃ for reaction for 1h to obtain a pure peroxytungstic acid solution again;
(6) and (3) carrying out ultrasonic spray pyrolysis on the pure peroxytungstic acid solution obtained in the step (5) under the conditions of introducing hydrogen, the spray rate being 120ml/min, the hydrogen flow rate being 350 ml/L and the pyrolysis temperature being 500 ℃ to obtain superfine spherical blue tungsten oxide powder, wherein the content of impurities in the blue tungsten trioxide meets the requirements of the national standard GB/T3457-.
Example 3
The embodiment provides a method for decomposing wolframite by oxygen pressure and preparing tungsten oxide and tungsten powder, wherein the method adopts 70% grade wolframite with 60 μm granularity as raw materials, and the method specifically comprises the following steps:
(1) adding wolframite into sulfuric acid solution with the concentration of 160 g/L, adding solid tungstic acid accounting for 10% of the wolframite mass, wherein the liquid-solid ratio of the system is 4:1, introducing oxygen, carrying out leaching reaction for 5 hours at 150 ℃ under the condition of controlling the oxygen pressure of 6MPa, and converting 99.3% of tungsten into tungstic acid;
(2) filtering and washing: filtering the reaction product obtained in the step (1) to obtain decomposition slag and leachate; supplementing sulfuric acid into the leachate, and returning to the step (1) to be used as a raw material for leaching reaction;
(3) hydrogen peroxide extraction-decomposition extraction of tungsten: washing the decomposed residue obtained in the step (2), mixing the washed decomposed residue with a hydrogen peroxide solution with the mass concentration of 5%, wherein the molar ratio of the added amount of hydrogen peroxide to tungstic acid in the decomposed residue is 1:1, carrying out tungsten extraction reaction for 2 hours at the temperature of 10 ℃, filtering reaction products to obtain a tungstic acid peroxide solution and insoluble residue, and returning the insoluble residue containing undecomposed wolframite to the leaching process of the step (1) for secondary leaching reaction; directly introducing SO into peroxytungstic acid solution2The concentration of sulfuric acid in the solution is controlled to be 0.5 mol/L until the peroxytungstic acid is completely decomposed to separate out the tungstic acid, and the content of impurity elements in the obtained tungstic acid is detected to be in accordance with the national standard GB/T10116-;
(4) washing the tungstic acid obtained in the step (3), and mixing the tungstic acid with a hydrogen peroxide solution with the mass concentration of 25% at the temperature of 30 ℃ for reaction for 1h to obtain a pure peroxytungstic acid solution again;
(5) and (3) carrying out ultrasonic spray pyrolysis on the pure peroxytungstic acid solution obtained in the step (4) under the conditions of introducing hydrogen, the spray rate being 150ml/min, the hydrogen flow rate being 400 ml/L and the pyrolysis temperature being 800 ℃ to obtain ultrafine spherical purple tungsten oxide powder, wherein the content of impurities in the purple tungsten oxide meets the requirements of national standard GB/T3457-.
Example 4
The embodiment provides a method for decomposing wolframite by oxygen pressure and preparing tungsten oxide and tungsten powder, the method adopts 55% grade wolframite with 90 μm granularity as raw material, the method specifically comprises the following steps:
(1) adding wolframite into sulfuric acid solution with the concentration of 120 g/L, adding solid tungstic acid accounting for 10% of the wolframite mass, wherein the liquid-solid ratio of the system is 4:1, introducing oxygen, carrying out leaching reaction for 5 hours at 150 ℃ under the condition of controlling the oxygen pressure of 6MPa, and converting 99.2% of tungsten into tungstic acid;
(2) filtering and washing: filtering the reaction product obtained in the step (1) to obtain decomposition slag and leachate; supplementing sulfuric acid into the leachate, and returning to the step (1) to be used as a raw material for leaching reaction;
(3) hydrogen peroxide extraction-decomposition extraction of tungsten: washing the decomposed residue obtained in the step (2), mixing the washed decomposed residue with a hydrogen peroxide solution with the mass concentration of 5%, wherein the molar ratio of the added amount of hydrogen peroxide to tungstic acid in the decomposed residue is 1:1, carrying out tungsten extraction reaction for 2 hours at the temperature of 10 ℃, filtering reaction products to obtain a tungstic acid peroxide solution and insoluble residue, and returning the insoluble residue containing undecomposed wolframite to the leaching process of the step (1) for secondary leaching reaction; directly heating to 90 ℃ until the peroxytungstic acid is completely decomposed to separate out the tungstic acid; through detection, the content of impurity elements in the obtained tungstic acid meets the national standard GB/T10116-;
(4) washing the tungstic acid obtained in the step (3), and mixing the tungstic acid with a hydrogen peroxide solution with the mass concentration of 25% at the temperature of 30 ℃ for reaction for 1h to obtain a pure peroxytungstic acid solution again;
(5) and (3) carrying out ultrasonic spray pyrolysis on the pure peroxytungstic acid solution obtained in the step (4) under the conditions of introducing hydrogen, the spray rate of 110ml/min, the hydrogen flow rate of 600 ml/L and the pyrolysis temperature of 1050 ℃ to obtain superfine spherical tungsten powder, wherein the content of impurities in the tungsten powder meets the requirements of national standard GB/T3458-.
Example 5
The embodiment provides a method for decomposing wolframite by oxygen pressure and preparing tungsten oxide and tungsten powder, the method adopts the raw material of the wolframite with the grade of 35% and the granularity of 120 mu m, and the method specifically comprises the following steps:
(1) oxygen pressure leaching reaction, namely adding wolframite into sulfuric acid solution with the concentration of 200 g/L, wherein the liquid-solid ratio of the system is 5:1, introducing oxygen, performing leaching reaction for 4 hours at the temperature of 200 ℃ and under the condition of controlling the oxygen pressure of 8MPa, and converting 99.6 percent of tungsten into tungstic acid;
(2) filtering and washing: filtering the reaction product obtained in the step (1) to obtain decomposition slag and leachate; supplementing sulfuric acid into the leachate, and returning to the step (1) to be used as a raw material for leaching reaction;
(3) hydrogen peroxide extraction-decomposition extraction of tungsten: washing the decomposed residue obtained in the step (2), mixing the washed decomposed residue with a hydrogen peroxide solution with the mass concentration of 5%, wherein the molar ratio of the added amount of hydrogen peroxide to tungstic acid in the decomposed residue is 1:1, carrying out tungsten extraction reaction for 2 hours at the temperature of 10 ℃, filtering reaction products to obtain a tungstic acid peroxide solution and insoluble residue, and returning the insoluble residue containing undecomposed wolframite to the leaching process of the step (1) for secondary leaching reaction; directly introducing SO into peroxytungstic acid solution2The concentration of sulfuric acid in the solution is controlled to be 0.5 mol/L until the peroxytungstic acid is completely decomposed to separate out the tungstic acid, and the content of impurity elements in the obtained tungstic acid is detected to be in accordance with the national standard GB/T10116-;
(4) and (4) washing the tungstic acid obtained in the step (3), and calcining at 850 ℃ for 4.0h to obtain yellow tungsten oxide. The detected impurity content in the yellow tungsten trioxide meets the requirements of the national standard GB/T3457-2013 (0-grade product).
Although the invention has been described in detail hereinabove by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that many modifications and improvements can be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims (7)

1. A method for decomposing wolframite and preparing tungsten oxide and tungsten powder by oxygen pressure is characterized by comprising the following steps:
(1) oxygen pressure leaching reaction: adding wolframite into an acid solution, and carrying out leaching reaction under the condition of introducing oxygen;
the grade of the wolframite is 10-70%; the particle size of the wolframite is less than 300 mu m;
the acid is sulfuric acid, hydrochloric acid or nitric acid with the concentration of 50-500 g/L;
the reaction is carried out at the temperature of 110-200 ℃ and under the condition of introducing oxygen and controlling the pressure to be 0.1-10 Mpa; adding solid tungstic acid with the mass being 0-20% of that of the wolframite into the reaction process for reaction;
(2) filtering and washing: filtering the reaction product obtained in the step (1) to obtain decomposition slag and leachate; adding acid into the leachate, and returning to the step (1) to be used as a raw material for leaching reaction;
(3) hydrogen peroxide extraction-decomposition extraction of tungsten: washing the decomposition residue obtained in the step (2), mixing the decomposition residue with a hydrogen peroxide solution to perform tungsten extraction reaction, and filtering a reaction product to obtain a peroxytungstic acid solution; heating the peroxytungstic acid solution to 50-90 ℃ or introducing SO2Until the peroxytungstic acid is completely decomposed to separate out tungstic acid; said introduction of SO2The concentration of sulfuric acid in the solution is controlled to be 0.1 mol/L-2.0 mol/L;
(4) extracting hydrogen peroxide for multiple times, decomposing and purifying tungstic acid: detecting the impurity content in the tungstic acid obtained in the step (3), directly using the tungstic acid in the subsequent step if the impurity content meets the standard requirement, adding a hydrogen peroxide solution and repeating the operation of the step (3) at least once if the impurity content exceeds the standard requirement until the tungstic acid with the impurity content meeting the standard requirement is obtained;
treating the tungstic acid with the impurity content meeting the standard requirement by adopting the following steps (5) or steps (6) to (7):
(5) calcining pure tungstic acid to prepare tungsten trioxide: calcining part of tungstic acid crystals with impurity content meeting the standard requirement to obtain powdery tungsten trioxide;
(6) spray pyrolysis of a peroxytungstic acid solution to prepare tungsten oxide and tungsten powder: mixing the tungstic acid with the impurity content meeting the standard requirement with a hydrogen peroxide solution again to carry out tungsten dissolution reaction to obtain a pure peroxytungstic acid solution;
(7) carrying out ultrasonic spray pyrolysis on the pure peroxytungstic acid solution under a non-reducing condition to obtain superfine spherical tungsten trioxide; and/or carrying out ultrasonic spray pyrolysis on the pure peroxytungstic acid solution under a reducing condition to obtain superfine spherical blue tungsten oxide, purple tungsten oxide and/or tungsten powder.
2. The method according to claim 1, wherein in the step (3), the mass concentration of the hydrogen peroxide solution is 5-30%, and the molar ratio of the amount of hydrogen peroxide in the hydrogen peroxide solution to tungstic acid in decomposition slag is 0.5-2: 1;
and/or the extraction reaction is carried out at the temperature of 10-40 ℃.
3. The method according to claim 1, wherein in the step (3), the mass concentration of the hydrogen peroxide solution is 5-30%, and the molar ratio of the amount of hydrogen peroxide in the hydrogen peroxide solution to tungstic acid in decomposition slag is 0.5-2: 1;
and/or the extraction reaction is carried out at the temperature of 10-40 ℃.
4. The method according to any one of claims 1 to 3, wherein the temperature of the calcination in the step (5) is 750 to 900 ℃.
5. The method according to any one of claims 1 to 3, wherein inert gas is introduced during the ultrasonic spray pyrolysis in the step (7), the spraying rate is 10 to 200ml/min, the gas flow rate is 150 to 600 ml/L, and the pyrolysis temperature is 500 to 900 ℃ to obtain the ultrafine spherical tungsten trioxide powder.
6. The method according to any one of claims 1 to 3, wherein hydrogen is introduced during the ultrasonic spray pyrolysis in the step (7), the spraying rate is 10 to 200ml/min, the hydrogen flow rate is 50 to 600 ml/L, and the pyrolysis temperature is 500 to 900 ℃, so that the ultrafine spherical purple tungsten oxide powder and/or the ultrafine spherical blue oxide powder are obtained.
7. The method according to any one of claims 1 to 3, wherein hydrogen is introduced during the ultrasonic spray pyrolysis in the step (7), the spraying rate is 10 to 200ml/min, the hydrogen flow rate is 100 to 800 ml/L, and the pyrolysis temperature is 900 to 1100 ℃, so that the ultrafine spherical tungsten powder is obtained.
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