Method for efficiently recycling residual alkali in tungsten ore decomposition liquid

Abstract

The invention discloses a method for efficiently recycling residual alkali in tungsten ore decomposition liquid. The method comprises the following steps: step S1, evaporation and concentration; step S2, salting-out crystallization; s3, cooling, filtering and separating; the solution obtained after tungsten ore is decomposed and filtered in the step S1 is transferred into a multi-effect evaporator to be evaporated and concentrated, solid sodium hydroxide is supplemented to be dissolved to generate heat in the step S2 to be evaporated, meanwhile, sodium tungstate crystals are separated out through a salting-out crystallization method, the defect that the steam consumption of a direct evaporation crystallization method is large is overcome, and the yield of the product is improved. The direct recovery rate of sodium tungstate and sodium hydroxide is greatly improved, the production cost is saved, and the economic benefits of enterprises are increased; in the step S3, the sodium hydroxide mother liquor is returned to the tungsten ore decomposition procedure, sodium hydroxide is recycled through alkali concentration, salting-out and crystallization, the use amount of the auxiliary material solid sodium hydroxide is greatly reduced, the use amount of environment-friendly neutralization added acid is reduced, the salt content in production wastewater is reduced, and economic benefits are increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of tungsten smelting, and particularly relates to a method for efficiently recycling residual alkali in tungsten ore decomposition liquid. Background Art

[0002] Tungsten resources mainly exist in the forms of wolframite and scheelite. With the decreasing amount of wolframite resources, scheelite resources have become the main tungsten ore species. After the pressure leaching and boiling process with excessive alkali is achieved, the production capacity and scale of scheelite smelting have been greatly improved. Due to the use of the excessive alkali process, although a large part of the alkali is consumed during the leaching process, after the reaction ends, the amount of residual alkali in the leaching liquid is still very high, and the concentration of residual alkali sodium hydroxide ranges from 60 - 150 g / L.

[0003] Too much residual alkali will have an impact on the subsequent process:

[0004] Firstly, the main process flow of modern tungsten smelting is the ion exchange method. Excessive alkali has an adverse effect on the adsorption of ion exchange, and the tungstate adsorption resin is affected. Acidic extraction requires a large amount of acid to neutralize the residual alkali.

[0005] Secondly, these excessive alkalis finally remain in the solution, and a large amount of acid must be consumed to neutralize the excessive alkali to meet the discharge standard of the waste liquid. Therefore, excessive residual alkali not only has an adverse effect on production, but also when a large amount of acid is added for neutralization treatment, the salt content of the treated wastewater is high, which makes the tungsten smelting industry gradually attach importance to the recovery of residual alkali.

[0006] Currently, the main method for recovering sodium hydroxide from the sodium tungstate alkali pressure leaching solution in tungsten smelting is the concentration crystallization method. Its principle is to evaporate and concentrate the sodium tungstate pressure leaching solution, thereby increasing the concentration of sodium tungstate in the solution. Sodium tungstate precipitates in the form of crystals, and finally the separation of sodium tungstate and sodium hydroxide is achieved.

[0007] Although the concentration crystallization method can realize the closed-loop recycling of the recovered alkali solution, in order to ensure the balance of the alkali water volume in the alkali boiling system, the solution volume generally needs to be concentrated to less than 1 / 6 of the original solution volume. To improve the direct recovery rate of sodium tungstate, the higher the concentration of sodium hydroxide in the recovered alkali solution, the better. However, after the alkali concentration increases to 300 g / L, as the concentration of sodium tungstate increases, the boiling point increases, and the fluidity of the high-concentration solution is poor. The number of sodium tungstate crystals formed increases, and it is easy to block the pipes and heat exchangers during the triple-effect evaporation process, seriously affecting the crystallization efficiency. The sodium tungstate crystals also cause serious wear to the equipment of the triple-effect evaporation system and block the pipelines, greatly shortening the service life of the equipment. The steam energy consumption consumed for separating and recovering sodium hydroxide from the concentrated solution by the concentration crystallization method is relatively large. Especially in the later stage of evaporation, the higher the alkali content in the solution, the higher the solution boiling point, and more steam is required.

[0008] Based on this, the present invention provides a method for efficiently recycling residual alkali in tungsten ore decomposition liquid. Summary of the Invention

[0009] In view of the above situation, to overcome the defects of the prior art, the present invention provides a method for efficiently recycling the remaining alkali in a tungsten ore decomposition solution, effectively solving the problems raised in the background art.

[0010] To achieve the above object, the present invention provides the following technical solution: A method for efficiently recycling the remaining alkali in a tungsten ore decomposition solution, comprising the following steps:

[0011] Step S1, evaporation and concentration: Transfer the solution obtained after filtering the tungsten ore decomposition into a multi-effect evaporator for evaporation, and evaporate and concentrate it until the concentration of sodium hydroxide is NaOH>260 g / L. Filter to obtain sodium tungstate crystals and concentrated solution. The sodium tungstate crystals are dissolved in water and returned to the main process.

[0012] Step S2, salting-out crystallization: Transfer the concentrated solution into a single-effect evaporator, and gradually add solid sodium hydroxide to the evaporator. The amount of solid sodium hydroxide added is 0.5-1.0 times the mass of sodium hydroxide in the solution, and stir for 1-2 hours.

[0013] Step S3, cooling, filtering and separation: Cool the mixture obtained in step S2 to 20-40 °C and then filter and separate to obtain sodium tungstate crystals and sodium hydroxide mother liquor; the sodium tungstate crystals are dissolved into a sodium tungstate solution and returned to the main process for preparing ammonium paratungstate, and the sodium hydroxide mother liquor is returned to the tungsten ore decomposition process.

[0014] Preferably, in step S1, the solution obtained after filtering the tungsten ore decomposition is transferred into a multi-effect evaporator for evaporation, the steam pressure is less than 0.5 mpa, and the negative pressure of the three-effect is 0.02-0.05 mpa.

[0015] Preferably, in step S2, solid sodium hydroxide is added to the concentrated solution, and the amount of solid sodium hydroxide added is 0.6-1.0 times the mass of sodium hydroxide in the solution.

[0016] Preferably, after the mixture obtained in step S3 is cooled, it is filtered and separated. The separation is centrifugal separation, and after separation, the ratio of tungsten to alkali in the sodium tungstate solution formed by dissolving the sodium tungstate crystals is greater than 50:1.

[0017] Preferably, the alkali concentration of the sodium hydroxide mother liquor obtained in step S3 is greater than 500 g / L.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. After the solution obtained from the decomposition and filtration of tungsten ore in step S1 of the present invention is transferred to a multiple-effect evaporator for evaporation and concentration, in step S2, heat is generated by adding solid sodium hydroxide for dissolution and evaporation. Meanwhile, sodium tungstate crystals are precipitated by the salting-out crystallization method, which makes up for the deficiency of large steam consumption in the direct evaporation crystallization method, greatly improves the direct recovery rates of sodium tungstate and sodium hydroxide, saves production costs, and increases the economic benefits of the enterprise.

[0020] 2. In step S3 of the present invention, the sodium hydroxide mother liquor is returned to the tungsten ore decomposition process, and sodium hydroxide is recovered by alkali concentration and salting-out crystallization, which greatly reduces the consumption of solid sodium hydroxide as auxiliary materials, reduces the amount of acid added for environmental protection neutralization, reduces the salt content in production wastewater, and increases economic benefits.

[0021] 3. In step S3 of the present invention, the solution is cooled and solid-liquid separated to obtain sodium tungstate crystals. The sodium tungstate crystals are dissolved to form a sodium tungstate solution with very low impurity content. The sodium tungstate solution with low alkali and low impurities enters the main process for ion exchange, which increases the ion exchange adsorption capacity and the concentration of desorbed ammonium tungstate, correspondingly reduces the consumption of various auxiliary materials for ion exchange and the power consumption in the evaporation crystallization process, improves the quality of ammonium paratungstate products, and increases the economic benefits of the enterprise.

[0022] 4. The method of the present invention realizes the closed-loop circulation of alkali, realizes the efficient recovery and utilization of tungsten and alkali, and has high direct recovery rates of sodium tungstate and alkali.

[0023] 5. The method of the present invention is simple to operate, has low energy consumption, and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention.

[0025] In the drawings:

[0026] Figure 1 It is a schematic flow chart of a method for efficiently recovering residual alkali in a tungsten ore decomposition solution of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] By Figure 1Provided that the present invention relates to a method for efficiently recycling residual alkali in a tungsten ore decomposition solution, which comprises the following steps:

[0029] Step S1, evaporation and concentration: Transfer the solution obtained after filtering the tungsten ore decomposition into a multi-effect evaporator for evaporation, and evaporate and concentrate it until the concentration of sodium hydroxide is NaOH > 260 g / L. Filter to obtain sodium tungstate crystals and concentrated solution. The sodium tungstate crystals are dissolved in water and returned to the main process.

[0030] Step S2, salting-out crystallization: Transfer the concentrated solution into a single-effect evaporator, and gradually add solid sodium hydroxide to the evaporator. The amount of solid sodium hydroxide added is 0.5 - 1.0 times the mass of sodium hydroxide in the solution, and stir for 1 - 2 hours.

[0031] Step S3, cooling, filtering and separation: Cool the mixture obtained in Step S2 to 20 - 40 °C and then filter and separate to obtain sodium tungstate crystals and sodium hydroxide mother liquor. The sodium tungstate crystals are dissolved into a sodium tungstate solution and returned to the main process for preparing ammonium paratungstate, and the sodium hydroxide mother liquor is returned to the tungsten ore decomposition process.

[0032] In Step S1 of this embodiment, the solution obtained after filtering the tungsten ore decomposition is transferred into a multi-effect evaporator for evaporation. The steam pressure is less than 0.5 mpa, and the negative pressure of the third effect is 0.02 - 0.05 mpa.

[0033] In Step S2 of this embodiment, solid sodium hydroxide is added to the concentrated solution. The amount of solid sodium hydroxide added is 0.6 - 1.0 times the mass of sodium hydroxide in the solution.

[0034] In Step S3 of this embodiment, the obtained mixture is cooled and then filtered and separated. The separation is centrifugal separation. After separation, the sodium tungstate crystals are dissolved into a sodium tungstate solution with a tungsten-alkali ratio greater than 50:1.

[0035] In Step S3 of this embodiment, the sodium hydroxide mother liquor has an alkali concentration greater than 500 g / L.

[0036] After the tungsten ore is decomposed by alkali and the residual alkali in the filtered and separated decomposition solution is concentrated, filtered and separated, solid caustic soda is added to the separated solution, stirred and then cooled, and solid-liquid separation is carried out. The residual alkali in the tungsten ore alkali decomposition solution is fully recovered, and high-purity sodium tungstate crystals are prepared. First, compared with the traditional evaporation and concentration for recycling residual alkali, this method greatly reduces steam energy consumption. Second, the volume of the solution changes little before and after the concentration and thickening process of the tungsten ore decomposition solution, and most of the impurities in the decomposition solution remain in the solution, and the separated sodium tungstate crystals have high purity. Third, the residual alkali recovered by the method provided by the present invention has a high concentration and a small volume, can all be returned to the tungsten ore decomposition and alkali preparation process, forming a closed-loop cycle of residual alkali. The impurities in the residual alkali enter the slag phase during the alkali boiling process to achieve the purpose of impurity removal. Through this method, the recovery rate of residual alkali in the tungsten ore decomposition solution is ≥ 98%.

[0037] Example 1:

[0038] Take 5 m3 of the solution obtained after decomposing and filtering tungsten ore. The concentration of WO3 is 150 g / L and the concentration of sodium hydroxide solution is 90 g / L. Transfer the solution to a multi-effect evaporator for evaporation. When the evaporation is concentrated to a concentration of NaOH: 270 g / L containing sodium hydroxide, transfer the solution to a single-effect evaporator, add 303 kg of solid sodium hydroxide, stir for 1.5 hours, and cool to 33 °C to obtain 1.5 m 3 mixed solution, and take a sample to detect that the concentration of sodium hydroxide is 502 g / L.

[0039] Example 2:

[0040] Take 6 m 3 of the solution obtained after decomposing and filtering tungsten ore. The concentration of WO3 is 140 g / L and the concentration of sodium hydroxide solution is 75 g / L. Transfer the solution to a multi-effect evaporator for evaporation. When the evaporation is concentrated to a concentration of NaOH: 280 g / L containing sodium hydroxide, transfer the solution to a single-effect evaporator, add 315 kg of solid sodium hydroxide, stir for 1.5 hours, and cool to 28 °C to obtain 1.5 m 3 mixed solution, and take a sample to detect that the concentration of sodium hydroxide is 510 g / L.

[0041] Example 3:

[0042] Take 5 m 3 of the solution obtained after decomposing and filtering tungsten ore. The concentration of WO3 is 140 g / L and the concentration of sodium hydroxide solution is 80 g / L. Transfer the solution to a multi-effect evaporator for evaporation. When the evaporation is concentrated to a concentration of NaOH: 280 g / L containing sodium hydroxide, transfer the solution to a single-effect evaporator, add 300 kg of solid sodium hydroxide, stir for 1.5 hours, and cool to 30 °C to obtain 1.4 m 3 mixed solution, and take a sample to detect that the concentration of sodium hydroxide is 501 g / L.

[0043] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0044] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for efficiently recovering excess alkali in tungsten ore decomposition liquid, comprising the following steps: Step S1, evaporation and concentration: the solution obtained after decomposition and filtration of the tungsten ore is transferred to a multi-effect evaporator for evaporation, and the solution is evaporated and concentrated to a concentration of sodium hydroxide of NaOH>260g / L, and sodium tungstate crystals and concentrated solution are obtained by filtration, and the sodium tungstate crystals are dissolved in water and then returned to the main process; Step S2, salting out and crystallizing: transferring the concentrated solution into a single-effect evaporator, gradually adding solid sodium hydroxide into the evaporator, wherein the amount of solid sodium hydroxide added is 0.5 to 1.0 times the mass of sodium hydroxide in the solution, and stirring for 1 to 2 hours; Step S3, cooling, filtering and separating: the mixed solution obtained in step S2 is cooled to 20-40°C and then filtered and separated to obtain sodium tungstate crystals and sodium hydroxide mother liquor; the sodium tungstate crystals are dissolved into sodium tungstate solution and returned to the main process for preparing ammonium paratungstate, and the sodium hydroxide mother liquor is returned to the decomposition process of tungsten ore.

2. The method for efficiently recovering excess alkali in tungsten ore decomposition liquid according to claim 1, characterized in that: In the step S1, the solution obtained after decomposition and filtration of the tungsten ore is transferred to a multiple-effect evaporator for evaporation, the steam pressure is less than 0.5 MPa, and the triple-effect negative pressure is 0.02-0.05 MPa.

3. The method for efficiently recovering excess alkali in tungsten ore decomposition liquid according to claim 2, characterized in that: In step S2, solid sodium hydroxide is added to the concentrated solution, and the amount of solid sodium hydroxide added is 0.6 to 1.0 times the mass of the sodium hydroxide in the solution.

4. The method for efficiently recovering excess alkali in tungsten ore decomposition liquid according to claim 1, characterized in that: The mixed solution obtained in step S3 is cooled and filtered for separation. The separation is centrifugal separation. After separation, the sodium tungstate crystals are dissolved into a sodium tungstate solution with a tungstate-alkali ratio greater than 50:

1.

5. The method for efficiently recovering excess alkali in tungsten ore decomposition liquid according to claim 1, characterized in that: The alkali concentration of the sodium hydroxide mother liquor obtained in step S3 is greater than 500 g / L.

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