Method for recycling sodium salt and process water by sodium salt roasting-water leaching vanadium extraction of vanadium slag

Abstract

The invention belongs to the technical field of vanadium extraction metallurgy, and particularly relates to a method for recycling sodium salt and process water through vanadium slag sodium salt roasting-water leaching vanadium extraction, which comprises the following steps of: a) uniformly mixing vanadium slag and sodium salt, and then performing sodium salt roasting; b) soaking the sodium modified clinker in water; c) precipitating the leachate to remove silicon; d) reducing the silicon-removed liquid to remove chromium, and carrying out reduced pressure evaporation; e) introducing CO2 into the dechromed concentrated vanadium liquid to adjust the pH value, and adding a solvating-out agent to obtain a primary crystal substance and a separated liquid; f) performing distillation separation on the separated liquid to obtain a solventing-out agent and primary crystallization mother liquor, returning the solventing-out agent to the step e), and returning the primary crystallization mother liquor to the step b); dissolving a primary crystal substance and adding an ammonium compound to precipitate vanadium; and g) introducing CO2 into the vanadium precipitation supernatant to adjust the pH to crystallize sodium bicarbonate so as to obtain sodium bicarbonate solid and secondary crystallization mother liquor, returning the sodium bicarbonate solid to the step a), and returning the secondary crystallization mother liquor to the step f). The method provided by the invention has good economic benefits and environmental benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of vanadium extraction metallurgy, and particularly relates to a method for sodium roasting of vanadium slag and water leaching to extract vanadium and recycle sodium salt and process water. Background Art

[0002] Vanadium slag is the main raw material for the production of vanadium oxide. The traditional industrial production process is sodium roasting and water leaching to extract vanadium. During the sodium roasting process of vanadium slag, part of the chromium reacts with sodium salts to form water-soluble sodium chromate, which enters the solution during the sodium clinker water leaching process, forming an alkaline leachate of sodium vanadate containing chromium; after the leachate is dephosphorized with calcium chloride, sulfuric acid is used to adjust the pH of the leachate to ≈ 2 and ammonium sulfate is added to precipitate vanadium to obtain the intermediate product ammonium polyvanadate. The vanadium precipitation wastewater mainly contains Na + NH4 + 、SO4 2- 、V 5+ Cr 6+ 、SiO3 2- etc., by adding reducing agents such as sodium metabisulfite, sodium bisulfite or sodium sulfite to V 5+ Cr 6+ Restore to V 4+ Cr 3+, The solution is then adjusted to a pH of 7-9 using sodium hydroxide, allowing vanadium, chromium, and silicon to precipitate, forming a vanadium-chromium reduction sludge. After separating the vanadium, chromium, and silicon, the solution is further adjusted to a pH of approximately 12 using sodium hydroxide. Ammonia is then removed by stripping, absorbed with sulfuric acid, and recycled for vanadium precipitation. The deammoniated wastewater is evaporated, concentrated, and crystallized to produce sodium sulfate as a solid waste. The condensate produced during the evaporation process contains a certain concentration of ammonia, which is produced during the clinker leaching cycle, impacting the leaching process. For every ton of vanadium pentoxide produced, approximately 2.5-3 tons of sodium sulfate as a solid waste are generated. In the existing sodium roasting-water leaching process for vanadium extraction, sodium roasting consumes a large amount of sodium carbonate and the water treatment process is complex, resulting in high vanadium oxide production costs. The treatment of vanadium precipitation wastewater produces a large amount of sodium sulfate as a solid waste, posing a significant environmental risk. Achieving low-cost recycling of sodium salts and process water, reducing vanadium oxide production costs, and minimizing the generation of sodium sulfate as a solid waste from water treatment are key challenges facing the vanadium industry.

[0003] To achieve the recycling of sodium salts during the vanadium slag extraction process, Publication No. CN 116837230A provides a method for clean vanadium extraction from vanadium slag and its application. The main technical concept involves using calcium oxide to remove silicon and phosphorus from the sodium-containing leachate, then using the calcium oxide to precipitate vanadium, producing an intermediate product, calcium vanadate, and a vanadium precipitation mother liquor. The vanadium precipitation mother liquor is then passed through CO2 to crystallize sodium bicarbonate, which is then returned to the roasting process as a sodium-forming additive. The sodium bicarbonate mother liquor is separated to remove chromium and then recycled for clinker leaching. The calcium vanadate is leached with sodium bicarbonate, evaporated and concentrated to produce solid sodium metavanadate. This solid is then mixed with an aluminum additive, reduced at high temperature, and leached to separate vanadium and sodium. The sodium-containing solution is then passed through CO2 to crystallize sodium bicarbonate, which is then returned to the roasting process as a sodium-forming additive. This process achieves the recycling of sodium salts, but it also presents challenges such as a lengthy process flow and high water evaporation.

[0004] Publication No. CN 116854109A provides a method for producing sodium carbonate and ammonium sulfate from sodium sulfate. The main technical concept involves dissolving the sodium sulfate and mixing it with ammonium bicarbonate, causing a double decomposition reaction to produce solid sodium bicarbonate. The crystallization mother liquor is then evaporated and crystallized to produce a mixed salt of sodium sulfate and ammonium sulfate, which is then separated to produce ammonium sulfate. The sodium bicarbonate can be recycled as a sodium-forming additive for vanadium slag roasting. A small amount of ammonium sulfate can be recycled as an ammonium salt in the vanadium precipitation process, with the majority of the ammonium sulfate being sold externally. While this method achieves the recycling of sodium salts, it also presents challenges such as a longer vanadium oxide production process and the addition of ammonium sulfate as a byproduct.

[0005] The problem of how to achieve low-cost recycling of sodium salt and process water based on the existing vanadium slag sodium roasting-water leaching vanadium extraction production process, reduce the cost of vanadium oxide production process and reduce the generation of sodium sulfate as solid waste in water treatment remains to be solved. At present, there are no relevant technical reports that can effectively solve the above problems and have prospects for industrial application. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a method for sodium roasting of vanadium slag and water leaching of vanadium to recycle sodium salt and process water. This method can achieve direct recycling of sodium salt and process water, reduce sodium salt consumption and wastewater evaporation and concentration treatment volume, reduce the production cost of vanadium oxide, and avoid the generation of sodium sulfate as solid waste in water treatment.

[0007] The present invention provides a method for sodium roasting of vanadium slag and water leaching to extract vanadium, which recycles sodium salt and process water, comprising the following steps:

[0008] a) mixing vanadium slag and sodium salt and then performing sodium roasting to obtain sodium clinker; wherein the sodium salt includes sodium carbonate and / or sodium bicarbonate;

[0009] b) subjecting the sodium-treated clinker to water leaching and solid-liquid separation to obtain a leaching residue and a leachate;

[0010] c) adding sodium aluminate to the leachate to perform precipitation and desiliconization, and performing solid-liquid separation to obtain desiliconized slag and desiliconized liquid;

[0011] d) adding a chromium removal agent to the desiliconized liquid to perform reduction and chromium removal, evaporating under reduced pressure and performing solid-liquid separation to obtain chromium hydroxide solid and dechromized concentrated vanadium liquid; wherein the chromium removal agent comprises one or more of formaldehyde, methanol, ethanol and glucose;

[0012] e) introducing CO2 into the dechromized concentrated vanadium solution to adjust the pH, adding a solvent to crystallize sodium bicarbonate and sodium metavanadate, and performing solid-liquid separation to obtain a primary crystal and a separated liquid; wherein the solvent comprises methanol and / or ethanol;

[0013] f) distilling and separating the separated liquid to obtain a solvent and a primary crystallization mother liquor; the solvent is returned to step e) for recycling; the primary crystallization mother liquor is returned to step b) for water immersion;

[0014] Dissolving the primary crystals and adding ammonium compounds to precipitate vanadium, and performing solid-liquid separation to obtain ammonium metavanadate solid and vanadium precipitation supernatant; wherein the ammonium compounds include one or more of ammonium carbonate, ammonium bicarbonate and ammonia water;

[0015] g) introducing CO2 into the upper layer of the vanadium precipitation liquid to adjust the pH and crystallize sodium bicarbonate, performing solid-liquid separation to obtain sodium bicarbonate solid and secondary crystallization mother liquor; the sodium bicarbonate solid is returned to step a) for mixing with the vanadium slag and then sodiumization and roasting; the secondary crystallization mother liquor is returned to step f) to participate in dissolving the primary crystals.

[0016] Preferably, in step a), the mass ratio of the sodium salt calculated as Na2O to the vanadium slag calculated as V2O5 is (0.93-1.05):1.

[0017] Preferably, in step a), the temperature of the sodium calcination is 780-830° C., and the time is 60-120 min.

[0018] Preferably, in step c), the molar ratio of the sodium aluminate calculated as Al to the leachate calculated as Si is (0.6-1):1.

[0019] Preferably, in step c), the reaction temperature of the precipitation silicon removal is 50-80° C., the reaction pH is 9-10.5, and the reaction time is 10-60 min.

[0020] Preferably, in step d), the reaction temperature for the reduction and chromium removal is 150-250° C., and the reaction time is 1-4 hours.

[0021] Preferably, in step e), the pH value of the dechromized concentrated vanadium solution is adjusted to 7-9 by CO2; the volume ratio of the solvent to the dechromized concentrated vanadium solution is (0.5-1):1; and the crystallization temperature is 15-30°C.

[0022] Preferably, in step f), the solution Na after the primary crystals are dissolved + The concentration is 35-50g / L.

[0023] Preferably, in step f), NH4 + The molar ratio of the ammonium compound to the primary crystallization compound is (2.8-3.5):1; the reaction temperature of the vanadium precipitation is 10-20° C., the reaction pH is 9.3-9.8, and the reaction time is 3-5 h.

[0024] Preferably, in step g), the pH value of the vanadium precipitation upper layer solution is adjusted to 7.5-8.5 by CO2.

[0025] Compared with the prior art, the present invention provides a method for sodium roasting of vanadium slag and water leaching to extract vanadium and recycle sodium salt and process water, comprising the following steps: a) mixing vanadium slag with sodium salt and then performing sodium roasting to obtain sodium clinker; wherein the sodium salt comprises sodium carbonate and / or sodium bicarbonate; b) leaching the sodium clinker in water, performing solid-liquid separation, and obtaining leaching residue and leachate; c) adding sodium aluminate to the leachate for precipitation and silicon removal, performing solid-liquid separation, and obtaining silicon-removed slag and silicon-removed liquid; d) adding a chromium removal agent to the silicon-removed liquid for reduction and chromium removal, performing reduced pressure evaporation and solid-liquid separation, and obtaining chromium hydroxide solid and dechromated concentrated vanadium liquid; wherein the chromium removal agent comprises one or more of formaldehyde, methanol, ethanol and glucose; e) introducing CO2 into the dechromated concentrated vanadium liquid to adjust the pH, and then adding a dissolving agent to crystallize sodium bicarbonate and sodium metavanadate. f) distilling and separating the separated liquid to obtain a solvent and a primary crystallization mother liquor; the solvent is returned to step e) for recycling; the primary crystallization mother liquor is returned to step b) to participate in water leaching; the primary crystallization is dissolved and an ammonium compound is added to precipitate vanadium, and the solid-liquid separation is performed to obtain ammonium metavanadate solid and a vanadium precipitation upper layer liquid; wherein the ammonium compound comprises one or more of ammonium carbonate, ammonium bicarbonate and ammonia water; g) CO2 is introduced into the vanadium precipitation upper layer liquid to adjust the pH and crystallize sodium bicarbonate, and the solid-liquid separation is performed to obtain sodium bicarbonate solid and a secondary crystallization mother liquor; the sodium bicarbonate solid is returned to step a) for mixing with vanadium slag and then sodiumization and roasting; the secondary crystallization mother liquor is returned to step f) to participate in dissolving the primary crystallization. The method provided by the present invention can achieve direct recycling of sodium salt and process water, reducing sodium salt consumption and wastewater evaporation and concentration processing volume, lowering vanadium oxide production costs, and avoiding the generation of sodium sulfate as solid waste from water treatment. More specifically, it has at least the following beneficial effects:

[0026] (1) The step-by-step impurity removal method of removing silicon first and then removing chromium is adopted to improve the purity of chromium hydroxide and facilitate the secondary utilization of chromium resources.

[0027] (2) The vanadium and sodium are separated from the dechromized concentrated vanadium liquid and then recycled for leaching sodium clinker, which greatly reduces the amount of process water evaporation and concentration, and avoids the problem of poor working environment caused by the recycling of ammonia-containing process water for leaching clinker.

[0028] (3) The secondary crystallization mother liquor is circulated to dissolve the mixture of sodium bicarbonate and sodium metavanadate, eliminating the treatment processes such as deammoniation of vanadium precipitation wastewater and absorption of ammonia-containing gas.

[0029] (4) The sodium salt in the solution system is recovered in the form of sodium bicarbonate and recycled for sodium roasting of vanadium slag, which reduces the amount of added sodium salt, creates conditions for reducing the cost of preparing vanadium oxide from vanadium slag, and avoids the generation of solid waste sodium sulfate. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0031] Figure 1 It is a process flow chart provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] The present invention provides a method for sodium roasting of vanadium slag and water leaching to extract vanadium and recycle sodium salt and process water. Figure 1 As shown, the following steps are included:

[0034] a) mixing vanadium slag and sodium salt and then performing sodium roasting to obtain sodium clinker; wherein the sodium salt includes sodium carbonate and / or sodium bicarbonate;

[0035] b) subjecting the sodium-treated clinker to water leaching and solid-liquid separation to obtain a leaching residue and a leachate;

[0036] c) adding sodium aluminate to the leachate to perform precipitation and desiliconization, and performing solid-liquid separation to obtain desiliconized slag and desiliconized liquid;

[0037] d) adding a chromium removal agent to the desiliconized liquid to perform reduction and chromium removal, evaporating under reduced pressure and performing solid-liquid separation to obtain chromium hydroxide solid and dechromized concentrated vanadium liquid; wherein the chromium removal agent comprises one or more of formaldehyde, methanol, ethanol and glucose;

[0038] e) introducing CO2 into the dechromized concentrated vanadium solution to adjust the pH, adding a solvent to crystallize sodium bicarbonate and sodium metavanadate, and performing solid-liquid separation to obtain a primary crystal and a separated liquid; wherein the solvent comprises methanol and / or ethanol;

[0039] f) distilling and separating the separated liquid to obtain a solvent and a primary crystallization mother liquor; the solvent is returned to step e) for recycling; the primary crystallization mother liquor is returned to step b) for water immersion;

[0040] Dissolving the primary crystals and adding ammonium compounds to precipitate vanadium, and performing solid-liquid separation to obtain ammonium metavanadate solid and vanadium precipitation supernatant; wherein the ammonium compounds include one or more of ammonium carbonate, ammonium bicarbonate and ammonia water;

[0041] g) introducing CO2 into the upper layer of the vanadium precipitation liquid to adjust the pH and crystallize sodium bicarbonate, performing solid-liquid separation to obtain sodium bicarbonate solid and secondary crystallization mother liquor; the sodium bicarbonate solid is returned to step a) for mixing with the vanadium slag and then sodiumization and roasting; the secondary crystallization mother liquor is returned to step f) to participate in dissolving the primary crystals.

[0042] In the method provided herein, in step a), the vanadium slag is mixed with the sodium salt and then roasted. This allows the vanadium in the vanadium slag to react with the sodium salt to form soluble sodium vanadate, facilitating the dissolution of the vanadium into the solution during the subsequent water leaching process. Furthermore, during the roasting process, a small amount of chromium in the vanadium slag reacts with the sodium to form water-soluble sodium chromate.

[0043] In the method provided by the present invention, in step a), the vanadium slag is preferably obtained by vanadium extraction and blowing from vanadium-containing molten iron in a converter; the main components of the vanadium slag preferably include V2O5, FeO, SiO2, TiO2, CaO, MgO, MnO and Cr2O3, wherein the content of V2O5 is generally 10-20wt%; the particle size of the vanadium slag is preferably ≤300μm, more preferably ≤200μm, further preferably ≤150μm, and most preferably ≤125μm (120 mesh).

[0044] In the method provided by the present invention, in step a), the mass ratio of the sodium salt calculated as Na2O to the vanadium slag calculated as V2O5 is preferably (0.93-1.05):1, specifically 0.93:1, 0.94:1, 0.95:1, 0.96:1, 0.97:1, 0.98:1, 0.99:1, 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1 or 1.05:1.

[0045] In the method provided by the present invention, in step a), the temperature of the sodium calcination is preferably 780-830°C, specifically 780°C, 785°C, 790°C, 795°C, 800°C, 805°C, 810°C, 815°C, 820°C, 825°C or 830°C; the time of the sodium calcination is preferably 60-120 min, specifically 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min, 95 min, 100 min, 105 min, 110 min, 115 min or 120 min.

[0046] In the method provided by the present invention, in step a), after completing the sodium roasting, the obtained sodium clinker is preferably ground. The particle size of the ground sodium clinker is preferably ≤300 μm, more preferably ≤200 μm, further preferably ≤150 μm, and most preferably ≤125 μm (120 mesh).

[0047] In the method provided herein, in step b), the sodium-treated clinker is leached in water, dissolving the water-soluble sodium vanadate in the clinker into a solution to produce a leachate. Because the primary crystallization mother liquor, after separation of vanadium and sodium, is subsequently recycled for clinker leaching, the sodium and vanadium concentrations in the leachate are higher than those in conventional processes, facilitating the subsequent crystallization and separation of sodium and vanadium from the solution.

[0048] In the method provided by the present invention, in step c), the main impurity elements contained in the leaching solution are chromium, silicon and phosphorus.

[0049] In the method provided by the present invention, in step c), the molar ratio of the sodium aluminate calculated as Al to the leachate calculated as Si is preferably (0.6-1):1, specifically 0.6:1, 0.65:1, 0.7:1, 0.75:1, 0.8:1, 0.85:1, 0.9:1, 0.95:1 or 1:1; the reaction temperature of the precipitation removal of silicon is preferably 50-80°C, specifically 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C; the reaction temperature of the precipitation removal of silicon is preferably 50-80°C, specifically 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C; The pH value is preferably 9 to 10.5, specifically 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10, 10.1, 10.2, 10.3, 10.4, or 10.5. The reaction time for the precipitation desiliconization is preferably 10 to 60 minutes, specifically 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, or 60 minutes. In the present invention, when the amount of sodium aluminate used is calculated at a molar ratio of Al / Si = 0.6 to 1, the silicon concentration of the desiliconized solution can be reduced to below 0.05 g / L, meeting the technical requirements for subsequent weakly alkaline ammonium vanadium precipitation.

[0050] In the method provided by the present invention, in step d), the chromium removal agent is selected as an organic reagent composed of three elements: C, H, and O. This is to avoid the chromium removal agent introducing sulfur, NH3, etc., which affect sodium salt, process water circulation, and ammonia volatilization and deteriorate the operating environment. The reaction products of the chromium removal process are mainly chromium hydroxide, sodium carbonate, and sodium hydroxide. No new impurity ions are introduced into the solution system, which avoids the problem that traditional chromium removal technology generally uses sulfur-containing reducing agents such as sodium metabisulfite, sodium sulfite, sodium bisulfite, sodium sulfide, and sodium sulfhydride to introduce sulfur, affecting the recovery of sodium salt in the form of sodium bicarbonate or sodium carbonate and the process water circulation. In the chromium removal process, trivalent chromium combines with phosphate to form a chromium phosphate precipitate, which enters the by-product chromium hydroxide. This reaction can control the phosphorus concentration of the solution system to be maintained within a smaller fluctuation range and will not be enriched. The chromium removal slurry is cooled and concentrated by reduced pressure evaporation to create conditions for subsequent vanadium and sodium crystallization separation.

[0051] In the method provided by the present invention, in step d), the reaction temperature of the reduction chromium removal is preferably 150-250°C to improve the chromium removal rate and control the oxidation product of the chromium removal agent to be carbonate, specifically 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C or 250°C; the reaction time of the reduction chromium removal is preferably 1-4h, specifically 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h.

[0052] In the method provided by the present invention, in step d), the volume of the dechromized concentrated vanadium solution is preferably 70-80% of the volume of the desiliconized solution, specifically 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79% or 80%; the Cr concentration of the dechromized concentrated vanadium solution is preferably controlled at ≤0.1 g / L, specifically 0.01 g / L, 0.02 g / L, 0.03 g / L, 0.04 g / L, 0.05 g / L, 0.06 g / L, 0.07 g / L, 0.08 g / L, 0.09 g / L or 0.1 g / L.

[0053] In the method provided herein, in step e), CO2 is passed through the dechromized concentrated vanadium solution to adjust the solution pH. This is to convert some of the sodium vanadate salt into sodium bicarbonate, which has a lower solubility, thereby facilitating the crystallization and separation of sodium ions from the solution. Simultaneously, sodium pyrovanadate is converted into sodium metavanadate. Because the solubility of sodium bicarbonate and sodium metavanadate decreases with decreasing temperature and they are insoluble in organic solvents such as methanol and ethanol, lowering the solution temperature and adding an organic solvent can help increase the solution's supersaturation and promote the crystallization of sodium bicarbonate and sodium metavanadate.

[0054] In the method provided by the present invention, in step e), the pH value of the dechromized concentrated vanadium solution is preferably adjusted to 7 to 9 by CO2, specifically 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9 or 9; the volume ratio of the solvent to the dechromized concentrated vanadium solution is preferably (0.5 to 1):1, specifically the crystallization temperature is preferably 15-30°C, specifically 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C (room temperature), 26°C, 27°C, 28°C, 29°C or 30°C.

[0055] In the method provided by the present invention, in step f), the separated liquid after separating the sodium bicarbonate and sodium metavanadate solids contains a solvent. Since the boiling point, specific heat capacity, and latent heat of vaporization of the solvents methanol and ethanol are much smaller than those of water, the energy required for distilling and separating the solvent is less than that for evaporating process water, which can reduce the evaporation and concentration cost of process water. The solvent separated by distillation can be recycled for the next round of sodium bicarbonate and sodium metavanadate crystallization. The primary crystallization mother liquor after separating the solvent has a low concentration of vanadium and sodium ions and can be recycled for leaching sodium clinker, reducing the amount of fresh water used for immersion.

[0056] In the method provided by the present invention, in step f), the primary crystallization product is a mixture of sodium bicarbonate and sodium metavanadate. By using ammonium bicarbonate, ammonium carbonate, ammonia water or the like to precipitate vanadium, the vanadium in the sodium metavanadate can be combined with ammonium ions to form ammonium metavanadate precipitate, thereby achieving the separation of vanadium and sodium, while avoiding the introduction of SO4 by using ammonium salts such as ammonium sulfate and ammonium chloride to precipitate vanadium. 2- 、Cl - Affects the circulation of sodium salt and process water.

[0057] In the method provided by the present invention, in step f), the solution Na after the primary crystals are dissolved + The concentration is preferably 35 to 50 g / L, specifically 35 g / L, 36 g / L, 37 g / L, 38 g / L, 39 g / L, 40 g / L, 41 g / L, 42 g / L, 43 g / L, 44 g / L, 45 g / L, 46 g / L, 47 g / L, 48 g / L, 49 g / L or 50 g / L; the pH value of the vanadium precipitation reaction is preferably 9.3 to 9.8, specifically 9.3, 9.4, 9.5, 9.6, 9.7 or 9.8. In the present invention, it is preferred to control the Na content of the vanadium precipitation solution. +The concentration is 35-50 g / L and the reaction pH is 9.3-9.8, because the solubility of sodium bicarbonate is relatively small, and a higher pH value of vanadium precipitation can increase the CO3 2- concentration, and correspondingly reduce HCO3 - concentration to avoid a large amount of sodium ions crystallizing out in the form of sodium bicarbonate during the vanadium precipitation process.

[0058] In the method provided by the present invention, in step f), the reaction time, reaction temperature and amount of ammonium compound used in the vanadium precipitation can be selected and determined according to the vanadium precipitation rate index of the weak alkaline ammonium salt vanadium precipitation test. + The molar ratio of the ammonium compound calculated as V to the primary crystallized product calculated as V is preferably (2.8-3.5):1, specifically 2.8:1, 2.9:1, 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1 or 3.5:1; the reaction temperature of the vanadium precipitation is preferably 10-20°C, specifically 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, 16°C, 17°C, 18°C, 19°C or 20°C; the reaction time of the vanadium precipitation is preferably 3-5h, specifically 3h, 3.5h, 4h, 4.5h or 5h.

[0059] In the method provided by the present invention, in step g), the upper layer of vanadium precipitation solution mainly contains Na + NH4 + 、CO3 2- 、HCO3 - VO3 - The purpose of passing CO2 into the upper layer of vanadium precipitation is to lower the pH value of the solution and make the CO3 2- Converted to HCO3 - . Since the solubility of sodium bicarbonate is much smaller than that of sodium carbonate, ammonium carbonate, ammonium bicarbonate and sodium vanadate, the sodium ions in the solution will crystallize out in the form of sodium bicarbonate, thereby realizing the recovery of sodium salt in the solution. The recovered sodium bicarbonate is returned to the sodium roasting process of step a) as a sodium-forming additive for recycling. Sodium bicarbonate decomposes into sodium carbonate during the high-temperature roasting process, which has the same function as the conversion of vanadium achieved by roasting with sodium carbonate in the existing vanadium slag. The secondary crystallization mother liquor after separating sodium bicarbonate contains a certain amount of ammonium bicarbonate, which is circulated for dissolving the primary crystals composed of sodium bicarbonate and sodium metavanadate and precipitating vanadium, thereby realizing the low-cost recycling of ammonium salts.

[0060] In the method provided by the present invention, in step g), the pH value of the vanadium precipitation upper layer liquid is preferably adjusted to 7.5-8.5 by CO2, specifically 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4 or 8.5.

[0061] For the purpose of greater clarity, the present invention is described in detail with reference to the following examples.

[0062] Example 1

[0063] 600g of converter vanadium slag (main chemical components: V2O5 14.97wt%, SiO2 14.93wt%, TiO2 11.38wt%, CaO 2.21wt%, MgO 2.94wt%, MnO 7.80wt%, Cr2O3 2.89wt%; particle size -120 mesh, i.e., the undersize after passing a 120-mesh sieve) was added with 137g of sodium bicarbonate and 58g of sodium carbonate according to a Na2O / V2O5 mass ratio of 0.94. The slag was calcined at 820°C in a muffle furnace for 90min to obtain 735.4g of sodium clinker. The sodium clinker was ground to -120 mesh and added to a Büchner funnel containing filter paper. 90°C tap water was then added to cover the slag surface, and the slag was soaked for 8min before being drained. Leaching was repeated several times in the same manner to obtain 1540mL of leachate and 562.2g of leached residue. The chemical composition of the leachate was: V 29.92 g / L, Na 25.02 g / L, Cr 2.23 g / L, Si 0.68 g / L, and P 0.03 g / L. The V content of the leached residue was 0.76 wt%, and the vanadium leaching rate was 91.51%. Based on an Al / Si molar ratio of 0.81, 2.5 g of sodium aluminate was added to the leachate. The solution was heated to 80°C in a water bath and stirred at a pH of 10.39 for 30 minutes to desiliconize. After completion of the desiliconization reaction, the solid-liquid separation and washing were performed to obtain 1590 mL of desiliconized solution with a Si content of 0.03 g / L. The desiliconized liquid and 1.8g formaldehyde were added to a 3L pressure reactor, heated to 160°C and kept at this temperature for 3h to remove chromium. After the dechromium reaction was completed, the pressure was released and the temperature was evaporated and cooled to 40°C under negative pressure. The solid-liquid separation was performed to obtain 1210mL of dechromized concentrated vanadium liquid with a Cr content of 0.05g / L. The dechromized concentrated vanadium liquid was naturally cooled to room temperature, the pH was adjusted to 8.28 by CO2, 700mL of ethanol was added, and the crystallization was stirred for 120min. The precipitated sodium bicarbonate and sodium metavanadate crystals were filtered to obtain 155.60g of a mixed solid of sodium bicarbonate and sodium metavanadate. The filtrate was distilled of ethanol in a constant temperature water bath at 85°C to obtain 1130mL of a primary crystallization mother liquor with the following solution components: V 4.25g / L and Na 3.74g / L. The mixed solid of sodium bicarbonate and sodium metavanadate was dissolved in water to obtain 820mL of Na + The concentration of vanadium precipitation solution is 41.82g / L; according to NH4 +Calculated at a molar ratio of vanadium / V = 3, 115g of ammonium carbonate was added to the vanadium precipitation solution, and the precipitation reaction was carried out at 10°C and pH = 9.51 for 4 hours with stirring. After the precipitation reaction, the solid and liquid were separated to obtain 85.68g of ammonium metavanadate and 860mL of the vanadium precipitation supernatant. Among them, the ammonium metavanadate contained 43.27wt% of V and 0.02wt% of Na; the chemical composition of the vanadium precipitation supernatant was: V 4.18g / L, Na 39.86g / L and NH4 + The pH of the solution was adjusted to 8.36 by passing CO2 into the upper layer of the vanadium precipitate. Sodium bicarbonate was crystallized under stirring and solid-liquid separation was performed to obtain 60.13 g of solid sodium bicarbonate and secondary crystallization mother liquor.

[0064] Sodium bicarbonate is recycled as a sodium-forming additive for the next round of vanadium slag roasting; the primary crystallization mother liquor is recycled as a leaching agent for the next round of sodium-forming clinker leaching; and the secondary crystallization mother liquor is recycled to dissolve the mixed solid of sodium bicarbonate and sodium metavanadate and then precipitate vanadium.

[0065] Example 2

[0066] 600g of converter vanadium slag (main chemical components: V2O5 14.97wt%, SiO2 14.93wt%, TiO2 11.38wt%, CaO 2.21wt%, MgO 2.94wt%, MnO 7.80wt%, Cr2O3 2.89wt%; particle size -120 mesh) was added with 126g of sodium bicarbonate and 80g of sodium carbonate, calculated according to a Na2O / V2O5 mass ratio of 1.04. The slag was calcined at 800°C in a muffle furnace for 90 minutes to obtain 739.7g of sodium clinker. The sodium clinker was ground to -120 mesh and added to a Büchner funnel containing filter paper. Then, tap water at approximately 90°C was added to cover the slag surface, soaked for 8 minutes, and then drained. The leaching process was repeated several times to obtain 1520mL of leachate and 578.1g of leached residue. The chemical composition of the leachate was: V 30.52 g / L, Na 29.06 g / L, Cr 2.48 g / L, Si 0.76 g / L, and P 0.03 g / L. The V content of the leached residue was 0.68 wt%, and the vanadium leaching rate was 92.19%. Based on an Al / Si molar ratio of 0.80, 2.7 g of sodium aluminate was added to the leachate. The solution was heated to 70°C in a water bath and stirred at a pH of 10.48 for 30 minutes to desiliconize. After completion of the desiliconization reaction, the solid-liquid separation and washing were performed to obtain 1580 mL of desiliconized solution with a Si content of 0.02 g / L. The desiliconized liquid and 2g of ethanol were added to a 3L pressure reactor, heated to 190°C and kept at this temperature for 4h to remove chromium. After the dechromium reaction was completed, the pressure was released and the temperature was evaporated and cooled to 40°C under negative pressure. The solid-liquid separation was performed to obtain 1190mL of dechromized concentrated vanadium liquid with a Cr content of 0.08g / L. The dechromized concentrated vanadium liquid was naturally cooled to room temperature, the pH was adjusted to 8.32 by CO2, 900mL of ethanol was added, and the crystallization was stirred for 120min. The precipitated sodium bicarbonate and sodium metavanadate crystals were filtered to obtain 178.43g of a mixed solid of sodium bicarbonate and sodium metavanadate. The filtrate was distilled of ethanol under a constant temperature water bath at 85°C to obtain 1080mL of a primary crystallization mother liquor with the following solution components: V 3.96g / L and Na 3.52g / L. The mixed solid of sodium bicarbonate and sodium metavanadate was dissolved in water to obtain 880mL of Na + The concentration of vanadium precipitation solution is 45.87g / L; according to NH4 + The vanadium precipitation solution was added with 75 mL of aqueous ammonia (28% by mass) and 96 g of ammonium bicarbonate, and the vanadium precipitation reaction was carried out at 15°C and pH 9.48 for 5 hours with stirring. After the reaction, the solid and liquid were separated to obtain 85.06 g of ammonium metavanadate and 1000 mL of the supernatant solution. The ammonium metavanadate contained 43.18 wt% of V and 0.03 wt% of Na. The chemical composition of the supernatant solution was: 4.76 g / L of V, 0.34 g / L of Na, and NH4 +The pH of the solution was adjusted to 8.38 by passing CO2 through the upper layer of the vanadium precipitate. Sodium bicarbonate was crystallized under stirring and solid-liquid separation was performed to obtain 63.80 g of solid sodium bicarbonate and secondary crystallization mother liquor.

[0067] Sodium bicarbonate is recycled as a sodium-forming additive for the next round of vanadium slag roasting; the primary crystallization mother liquor is recycled as a leaching agent for the next round of sodium-forming clinker leaching; and the secondary crystallization mother liquor is recycled to dissolve the mixed solid of sodium bicarbonate and sodium metavanadate and then precipitate vanadium.

[0068] Example 3

[0069] 600g of converter vanadium slag (main chemical components: V2O5 14.97wt%, SiO2 14.93wt%, TiO2 11.38wt%, CaO 2.21wt%, MgO 2.94wt%, MnO 7.80wt%, Cr2O3 2.89wt%; particle size -120 mesh) was added with 148g of sodium bicarbonate and 62g of sodium carbonate according to a Na2O / V2O5 mass ratio of 1.01. The slag was calcined at 800°C in a muffle furnace for 90 minutes to obtain 740.9g of sodium clinker. The sodium clinker was ground to -120 mesh and added to a Büchner funnel containing filter paper. Then, tap water at approximately 90°C was added to cover the slag surface, soaked for 8 minutes, and then drained. The leaching process was repeated several times to obtain 1500mL of leachate and 574.2g of leached residue. The chemical composition of the leachate was: V 30.83 g / L, Na 28.91 g / L, Cr 2.51 g / L, Si 0.72 g / L, and P 0.03 g / L. The V content of the leached residue was 0.71 wt%, and the vanadium leaching rate was 91.90%. Based on an Al / Si molar ratio of 0.79, 2.5 g of sodium aluminate was added to the leachate. The solution was heated to 60°C in a water bath and stirred at a pH of 10.44 for 30 minutes to desiliconize. After completion of the desiliconization reaction, the solid-liquid separation and washing were performed to obtain 1550 mL of desiliconized solution with a Si content of 0.02 g / L. The desiliconized liquid and 2g of glucose were added to a 3L pressure reactor, heated to 150°C and kept at this temperature for 3h to remove chromium. After the dechromium reaction was completed, the pressure was released and the temperature was evaporated and cooled to 40°C under negative pressure. The solid-liquid separation was performed to obtain 1170mL of dechromized concentrated vanadium liquid with a Cr content of 0.06g / L. The dechromized concentrated vanadium liquid was naturally cooled to room temperature, the pH was adjusted to 8.37 by CO2, 1000mL of methanol was added, and the crystallization was stirred for 120min. The precipitated sodium bicarbonate and sodium metavanadate crystals were filtered to obtain 172.06g of a mixed solid of sodium bicarbonate and sodium metavanadate. The filtrate was distilled of methanol under a constant temperature water bath at 75°C to obtain 1120mL of a primary crystallization mother liquor with the following solution components: V 4.41g / L and Na 4.06g / L. The mixed solid of sodium bicarbonate and sodium metavanadate was dissolved in water to obtain 930mL of Na+ The concentration of vanadium precipitation solution is 41.73g / L; according to NH4 + Calculated at a molar ratio of vanadium / V = 3, 115g of ammonium carbonate was added to the vanadium precipitation solution, and the precipitation reaction was carried out at 15°C and pH = 9.56 with stirring for 5 hours. After the precipitation reaction, the solid and liquid were separated to obtain 82.97g of ammonium metavanadate and 990mL of the vanadium precipitation supernatant. The ammonium metavanadate contained 43.24wt% of V and 0.02wt% of Na. The chemical composition of the vanadium precipitation supernatant was: V 4.82g / L, Na 39.19g / L, and NH4 + The pH of the solution was adjusted to 8.32 by passing CO2 through the upper layer of the vanadium precipitate. Sodium bicarbonate was crystallized under stirring and solid-liquid separation was performed to obtain 59.02 g of solid sodium bicarbonate and secondary crystallization mother liquor.

[0070] Sodium bicarbonate is recycled as a sodium-forming additive for the next round of vanadium slag roasting; the primary crystallization mother liquor is recycled as a leaching agent for the next round of sodium-forming clinker leaching; and the secondary crystallization mother liquor is recycled to dissolve the mixed solid of sodium bicarbonate and sodium metavanadate and then precipitate vanadium.

[0071] In summary, the present invention provides a method for sodium slag roasting and water leaching to extract vanadium, recycling sodium salts and process water. The sodium slag leachate is treated for impurities and separated into a mixture of sodium bicarbonate and sodium metavanadate, and then recycled to leach sodium clinker. The sodium bicarbonate and sodium metavanadate mixture is ammoniumized to precipitate vanadium, and the upper layer of the vanadium precipitation liquid is crystallized into sodium bicarbonate and then recycled to dissolve the mixture of sodium bicarbonate and sodium metavanadate. Sodium bicarbonate is then recycled as a sodium slag additive for sodium roasting of the vanadium slag. The method provided by the present invention achieves the recycling of media such as sodium, ammonium, and process water, reduces the cost of vanadium extraction from vanadium slag, avoids the generation of sodium sulfate as a solid waste from water treatment, and enhances the competitiveness of the vanadium oxide production industry from vanadium slag.

[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for sodium roasting of vanadium slag and water leaching to extract vanadium and recycle sodium salt and process water, characterized in that: The following steps are involved: a) mixing vanadium slag and sodium salt and then performing sodium roasting to obtain sodium clinker; wherein the sodium salt includes sodium carbonate and / or sodium bicarbonate; b) subjecting the sodium-treated clinker to water leaching and solid-liquid separation to obtain a leaching residue and a leachate; c) adding sodium aluminate to the leachate to perform precipitation and desiliconization, and performing solid-liquid separation to obtain desiliconized slag and desiliconized liquid; d) adding a chromium removal agent to the desiliconized liquid to perform reduction and chromium removal, evaporating under reduced pressure and performing solid-liquid separation to obtain chromium hydroxide solid and dechromized concentrated vanadium liquid; wherein the chromium removal agent comprises one or more of formaldehyde, methanol, ethanol and glucose; e) introducing CO2 into the dechromized concentrated vanadium solution to adjust the pH, adding a solvent to crystallize sodium bicarbonate and sodium metavanadate, and performing solid-liquid separation to obtain a primary crystal and a separated liquid; wherein the solvent comprises methanol and / or ethanol; f) distilling and separating the separated liquid to obtain a solvent and a primary crystallization mother liquor; the solvent is returned to step e) for recycling; the primary crystallization mother liquor is returned to step b) for water immersion; Dissolving the primary crystals and adding ammonium compounds to precipitate vanadium, and performing solid-liquid separation to obtain ammonium metavanadate solid and vanadium precipitation supernatant; wherein the ammonium compounds include one or more of ammonium carbonate, ammonium bicarbonate and ammonia water; g) introducing CO2 into the upper layer of the vanadium precipitation liquid to adjust the pH and crystallize sodium bicarbonate, performing solid-liquid separation to obtain sodium bicarbonate solid and secondary crystallization mother liquor; the sodium bicarbonate solid is returned to step a) for mixing with the vanadium slag and then sodiumization and roasting; the secondary crystallization mother liquor is returned to step f) to participate in dissolving the primary crystals.

2. The method according to claim 1, characterized in that In step a), the mass ratio of the sodium salt calculated as Na2O to the vanadium slag calculated as V2O5 is (0.93-1.05):

1.

3. The method according to claim 1, characterized in that In step a), the sodium calcination temperature is 780-830° C. and the time is 60-120 min.

4. The method according to claim 1, wherein In step c), the molar ratio of the sodium aluminate calculated as Al to the leachate calculated as Si is (0.6-1):

1.

5. The method according to claim 1, wherein In step c), the reaction temperature of the precipitation silicon removal is 50-80° C., the reaction pH value is 9-10.5, and the reaction time is 10-60 min.

6. The method according to claim 1, characterized in that In step d), the reaction temperature for the reduction and chromium removal is 150-250° C., and the reaction time is 1-4 hours.

7. The method according to claim 1, characterized in that In step e), the pH value of the dechromized concentrated vanadium solution is adjusted to 7-9 by CO2; the volume ratio of the solvent to the dechromized concentrated vanadium solution is (0.5-1):1; and the crystallization temperature is 15-30°C.

8. The method according to claim 1, characterized in that In step f), the solution Na after the primary crystals are dissolved + The concentration is 35-50g / L.

9. The method according to claim 1, characterized in that In step f), NH4 + The molar ratio of the ammonium compound to the primary crystallization compound is (2.8-3.5):1; the reaction temperature of the vanadium precipitation is 10-20° C., the reaction pH is 9.3-9.8, and the reaction time is 3-5 h.

10. The method according to claim 1, characterized in that In step g), the pH value of the vanadium precipitation upper layer solution is adjusted to 7.5-8.5 by CO2.

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