A method for extracting vanadium by roasting high-chromium vanadium slag with inert gas and sodium carbonate and then separating by magnetic separation

Abstract

The application discloses a method for separating and extracting vanadium from high-chromium vanadium slag after roasting by inert gas and sodium carbonate, and relates to the technical field of separating and extracting vanadium, and the process comprises the following steps: firstly, sodium carbonate is added into vanadium-chromium slag, and after mixing, the mixture is roasted to 900 DEG C under an argon atmosphere, and then the sintered sample is obtained after the furnace is cooled to room temperature; the sintered sample is crushed, and the crushed mixture is ground to 200 meshes; through a magnetic separator, chromite with strong magnetism and non-magnetic NaVO2 and NaFeO2 are obtained, so that the separation of NaVO2, NaFeO2 and FeCr2O4 is realized; the non-magnetic NaVO2 and NaFeO2 after separation are immersed in water to obtain a NaVO2 aqueous solution, and then an ammonium salt is added to obtain a vanadium precipitate. In the sodium roasting process, on one hand, vanadium sodium phases are formed through sodium roasting, and on the other hand, the oxidation of chromium into hexavalent chromium which is easily soluble in water is avoided, the oxidation of magnetite and the formation of weakly magnetic iron oxide are avoided, the strong magnetism of magnetite is retained, and conditions for subsequent magnetic separation are provided.

Description

Technical Field

[0001] This invention relates to the field of vanadium separation and extraction technology, and more specifically to a method for magnetic separation and extraction of vanadium after roasting high-chromium vanadium slag with inert gas and sodium carbonate. Background Technology

[0002] Vanadium and chromium are both important strategic metals. Vanadium and its compounds are widely used in the steel, chemical, and aerospace industries. Chromium and its compounds are also widely used in the metallurgical, refractory, and leather industries. Vanadium-bearing magnetite is an important vanadium resource, and vanadium slag containing approximately 7%-15% vanadium is obtained after ironmaking in a converter. Vanadium slag is a product of blast furnace ironmaking and oxidation in a converter of vanadium-titanium magnetite, and is a vanadium-rich raw material. The current main process for extracting vanadium from vanadium slag involves roasting the vanadium slag with sodium salts at high temperature to form water-soluble sodium vanadate, followed by water leaching of the sodium vanadate to obtain an aqueous solution, which is then subjected to ammonium salt precipitation of vanadium. Currently, single vanadium-iron ore resources are relatively scarce, and vanadium slag mostly exists in nature as vanadium-chromium iron ore.

[0003] In V-Cr slag, vanadium and chromium, with similar chemical properties, coexist in the spinel phase. During the high-temperature sodium salt oxidative roasting process to produce sodium vanadate, sodium chromate, which is also soluble in water, is formed simultaneously. In traditional processes, sodium vanadate is leached out along with water. The coexistence of sodium chromate and sodium vanadate not only complicates vanadium extraction and reduces vanadium purity but also wastes a significant amount of chromium resources. More seriously, the currently mature vanadate leaching process is not suitable for vanadium precipitation from high-chromium vanadium slag because sodium chromate in water increases the solubility of ammonium vanadate, resulting in lower vanadium precipitation efficiency.

[0004] Currently, there is a large body of research on the separation of vanadium (V) and chromium (VI) from aqueous solutions, such as chemical precipitation, solvent extraction, and ion exchange to extract vanadium and chromium from aqueous solutions, followed by two precipitation processes. These separation methods have not yet been commercially applied, mainly for two reasons: firstly, the separation process requires large amounts of acids, alkalis, and chemical reagents, resulting in high costs; secondly, it is difficult for any current separation technology to completely precipitate chromium in aqueous solutions, leading to persistent wastewater with excessive levels of hexavalent chromium, causing significant environmental pollution.

[0005] Therefore, how to provide a vanadium extraction method that avoids the formation of hexavalent chromium is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a method for vanadium extraction by magnetic separation after roasting high-chromium vanadium slag with inert gas and sodium carbonate.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for vanadium extraction by magnetic separation after roasting high-chromium vanadium slag with inert gas and sodium carbonate, the process comprising:

[0009] 1) First, sodium carbonate was added to the vanadium-chromium slag at a weight ratio of 1:1. After mixing, the mixture was calcined to 900°C under an argon atmosphere and then cooled to room temperature in the furnace to obtain a sintered sample.

[0010] 2) The sintered sample is pulverized, and the pulverized mixture is ground through a 200-mesh sieve;

[0011] 3) By separating strongly magnetic chromite and non-magnetic NaVO2 and NaFeO2 through a magnetic separator, the separation of NaVO2, NaFeO2 and FeCr2O4 is achieved.

[0012] 4) After separation, the non-magnetic NaVO2 and NaFeO2 are leached with water to obtain an aqueous solution of NaVO2. Then, ammonium salt is added to obtain vanadium precipitate. The molar ratio of the amount of ammonium salt added to the vanadium content in the aqueous solution is 1:1.1. The ammonium salt is ammonium sulfate.

[0013] Fe₂VO₄ + Na₂CO₃ → NaVO₂ (soluble in water) + CO₂ + NaFeO₂ (argon roasting of trivalent vanadium)

[0014] Fe₂VO₄ + Na₂CO₃ + O₂ → NaVO₃ (soluble in water) + CO₂ + NaFeO₂ (air roasting) Pentavalent vanadium FeCr₂O₄ + Na₂CO₃ → NaCrO₂ (insoluble in water) + CO₂ + NaFeO₂ (trivalent chromium) (argon roasting, no reaction below 900°C)

[0015] FeCr₂O₄ + Na₂CO₃ + O₂ → Na₂CrO₄ (soluble in water) + CO₂ + NaFeO₂ (traditional air roasting of hexavalent chromium)

[0016] As can be seen from the above technical solution, compared with the prior art, this invention discloses a method for magnetic separation and vanadium extraction after roasting high-chromium vanadium slag with inert gas and sodium carbonate. Considering that the conversion of trivalent chromium to hexavalent chromium requires three necessary factors, namely high temperature, alkaline environment, and oxygen atmosphere, this invention proposes a method of roasting by sodium salt with inert gas protection and heating. After roasting, non-magnetic sodium vanadate is generated, without the production of ferric oxide and sodium chromate. The high-temperature protective atmosphere also preserves the chromium and iron phases as magnetic magnetite, facilitating subsequent magnetic separation. Argon-fueled roasting results in a structure where sodium vanadate is distributed on the surface and chromite is present inside. This is because sodium vanadate has a melting point of 700℃, while chromite has a higher melting point. When the roasting temperature reaches 900℃, sodium vanadate melts, while chromite remains solid. At high temperatures, liquid and solid separation occurs. When the temperature drops to room temperature, the surface forms sodium vanadate, and the interior contains chromite.

[0017] This invention, during sodium roasting, simultaneously forms a sodium vanadium phase through sodium roasting while preventing chromium from oxidizing to water-soluble hexavalent chromium and magnetite from oxidizing to form weakly magnetic iron oxide, thus preserving the strong magnetism of magnetite and providing conditions for subsequent magnetic separation. Since sodium vanadate is mainly enriched on the surface and chromite is internal after roasting, the strongly magnetic chromite and non-magnetic sodium vanadate can be easily separated by magnetic separation after grinding. This method enables large-scale processing of high-chromium-vanadium slag, eliminating the need for water leaching and achieving separation of sodium vanadium and chromium through physical separation. Furthermore, this method does not require acids, alkalis, or other expensive chemical adsorbents, nor does it require water leaching, which is beneficial for large-scale production, conserves valuable water resources, and avoids water pollution caused by pentavalent vanadium and hexavalent chromium. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 The attached figures illustrate the vanadium extraction process provided by this invention and the conventional air roasting vanadium extraction process.

[0020] Figure 2 The attached figures show the TGDSC results of sintered samples obtained by the vanadium extraction process provided by this invention and the conventional air roasting vanadium extraction process.

[0021] Figure 3 The attached figure shows the XRD comparison results of sintered samples obtained by the vanadium extraction process provided by the present invention and the conventional air roasting vanadium extraction process. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] This embodiment uses the method of the present invention and the traditional air roasting method to extract vanadium from vanadium-chromium slag:

[0025] The method of this invention is as follows: First, sodium carbonate is added to vanadium-chromium slag and mixed evenly, then calcined at 900°C under an argon atmosphere, and then cooled to room temperature in the furnace to obtain a sintered sample; the sintered sample is pulverized, and the pulverized mixture is ground through a 200-mesh screen; strong magnetic chromite and non-magnetic NaVO2 and NaFeO2 are separated by a magnetic separator, thereby achieving the separation of NaVO2, NaFeO2 and FeCr2O4; the separated non-magnetic NaVO2 and NaFeO2 are leached with water to obtain a NaVO2 aqueous solution, and then ammonium sulfate is added to obtain vanadium precipitate, the molar ratio of the amount of ammonium sulfate added to the vanadium content in the aqueous solution is 1:1.1.

[0026] The traditional air-roasting method involves first adding sodium carbonate to vanadium-chromium slag, mixing thoroughly, and then roasting in air to 900°C. The sintered sample is then cooled to room temperature in the furnace. The sintered sample consists of water-soluble sodium vanadate and sodium chromate, and water-insoluble titanium-manganese-iron-silicon-calcium slag. This is followed by soaking in water at a ratio of 1 kg / L to obtain an aqueous solution containing sodium vanadate and sodium chromate. Finally, ammonium sulfate is added to react the sodium vanadate and ammonium sulfate in the aqueous solution to form a water-insoluble ammonium vanadate precipitate.

[0027] The flow chart after argon and air roasting is as follows: Figure 1 As shown.

[0028] TGDSC results indicate that the roasting mechanisms under argon and air atmospheres are different. Roasting sodium-vanadium-chromium slag under argon atmosphere at 700℃-900℃ results in less weight loss. Figure 2 As shown. XRD comparison of the phases formed under different atmospheres shows that the main phases under air are sodium vanadate and sodium chromate, ferric oxide; under argon, the main phases are sodium vanadate, chromite, etc. Figure 3 As shown in Tables 1 and 2, SEM revealed that the structure of vanadium slag after argon roasting consisted of sodium vanadate distributed on the surface and chromite inside. After air roasting, the structure consisted of both sodium vanadate and sodium chromate distributed on the surface, with ferric oxide inside. The reason for the argon roasting structure is that sodium vanadate has a melting point of 700℃, while chromite has a higher melting point. When the roasting temperature reaches 900℃, sodium vanadate melts, while chromite remains solid. At high temperatures, liquid and solid separation occurs. When the temperature drops to room temperature, the structure of sodium vanadate on the surface and chromite inside forms. The air-roasted structure is formed because the sodium salt and oxygen work together to promote the formation of sodium vanadate and sodium chromate. The melting points of sodium vanadate and sodium chromate are 850℃ and 792℃, respectively. When the roasting temperature reaches 900℃, both sodium vanadate and sodium chromate melt. Magnetite is oxidized to ferric oxide under the combined action of high temperature and oxygen. Liquid and solid separation occurs at high temperature. When the temperature drops to room temperature, sodium chromate and sodium vanadate form on the surface, while the internal structure is ferric oxide.

[0029] Table 1

[0030]

[0031]

[0032] Table 2

[0033] element wt% wt% Sigma Atomic percentage C 8.82 0.67 15.11 O 36.73 0.57 47.23 Na 31.09 0.40 27.82 Al 0.48 0.06 0.37 Si 1.19 0.07 0.87 Ca 0.19 0.05 0.10 Ti 0.66 0.07 0.28 V 12.20 0.22 4.93 Cr 4.21 0.16 1.66 Mn 0.92 0.11 0.35 Fe 3.51 0.15 1.29 Total: 100.00 100.00

[0034] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0035] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for vanadium extraction by magnetic separation after roasting high-chromium vanadium slag with inert gas and sodium carbonate, characterized in that the process... include: 1) First, sodium carbonate is added to vanadium-chromium slag at a molar ratio of 1:1.1 for vanadium and sodium carbonate. After mixing, the mixture is calcined to 900°C under an argon atmosphere and then cooled to room temperature in the furnace to obtain a sintered sample. 2) The sintered sample is pulverized, and the pulverized mixture is ground through a 200-mesh sieve; 3) By separating strongly magnetic chromite and non-magnetic NaVO2 and NaFeO2 through a magnetic separator, the separation of NaVO2, NaFeO2 and FeCr2O4 is achieved. 4) After separation, the non-magnetic NaVO2 and NaFeO2 are leached with water to obtain an aqueous solution of NaVO2, and then ammonium salt is added to obtain vanadium precipitate.

2. The method for separating vanadium by roasting high-chromium vanadium slag with inert gas and sodium carbonate and then magnetic separation according to claim 1, characterized in that, The sintered sample obtained in step 1) is a mixture of sodium vanadate and chromite, wherein sodium vanadate is distributed on the surface and chromite is inside.

3. The method for extracting vanadium by roasting high-chromium vanadium slag with inert gas and sodium carbonate and then magnetic separation according to claim 1, characterized in that, In step 4), the molar ratio of the amount of ammonium salt added to the vanadium content in the aqueous solution is 1:1.

1.

4. The method for separating vanadium by roasting high-chromium vanadium slag with inert gas and sodium carbonate and then magnetic separation according to claim 1, characterized in that, In step 4), the ammonium salt is ammonium sulfate.

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