A method for selectively separating vanadium and chromium from vanadium-chromium residue

Abstract

The application belongs to the technical field of metallurgy, and particularly discloses a method for selectively separating vanadium and chromium from vanadium-chromium slag, which specifically comprises the following steps: mixing vanadium-chromium slag with mixed salt to obtain composite mixed raw material, wherein the mixed salt is a mixture of sodium salt and calcium salt, or a mixture of sodium salt and magnesium salt; under an oxygen atmosphere, the composite mixed raw material is selectively oxidized and roasted at 850-950 DEG C for 1-4h, so that vanadium is converted into water-soluble sodium vanadate and / or sodium-calcium composite vanadate capable of releasing vanadium, to obtain composite roasted clinker; water is used as leaching agent to water soak the composite roasted clinker, and then solid-liquid separation is performed, so that vanadium and chromium are separated. The application can effectively shorten the process flow, realize efficient separation of vanadium and chromium, and effectively reduce the production cost.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically the field of vanadium-chromium separation, and specifically relates to a method for selectively separating vanadium and chromium from vanadium-chromium slag. Background Technology

[0002] Vanadium and chromium are both important strategic metals with irreplaceable applications in fields such as steel metallurgy, aerospace, chemical catalysis, and new energy batteries. Vanadium-chromium slag is rich in vanadium and chromium, but vanadium and chromium in vanadium-chromium slag often coexist in the form of spinel, oxides, or complex solid solutions. The phase structure is stable, making it difficult to achieve efficient vanadium recovery through direct leaching.

[0003] The traditional method for separating and extracting vanadium from vanadium-chromium slag is the calcination-roasting-acid leaching process. This process converts vanadium into water-insoluble calcium vanadate during roasting, followed by acid leaching to extract the vanadium into the solution. While this process achieves selective leaching of vanadium, leaving most of the chromium in the slag phase, the acid leaching process consumes a large amount of acid, increasing production costs. Furthermore, the acidic medium can corrode the leaching equipment.

[0004] Chinese patent CN103614566A discloses a method for extracting vanadium and chromium from converter vanadium-chromium slag. The method involves two steps: roasting with Na2CO3 and water leaching, which converts vanadium and chromium into water-soluble sodium vanadate and sodium chromate in stages, ultimately achieving comprehensive extraction of vanadium and chromium. However, this method requires two stages of roasting and two leaching processes, resulting in a long process flow. Furthermore, chromium ultimately enters the leaching solution, requiring subsequent vanadium-chromium separation and chromium-containing solution treatment, making the operation complex.

[0005] Therefore, how to shorten the process flow, achieve efficient separation of vanadium and chromium, and reduce production costs is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a method for selectively separating vanadium and chromium from vanadium-chromium slag. This invention can effectively shorten the process flow, achieve efficient separation of vanadium and chromium, and effectively reduce production costs.

[0007] The technical solution of this invention is implemented as follows:

[0008] A method for selectively separating vanadium and chromium from vanadium-chromium slag specifically includes the following steps:

[0009] S1: Mix vanadium-chromium slag with mixed salt to obtain a composite mixed raw material, wherein the mixed salt is a mixture of sodium salt and calcium salt, or a mixture of sodium salt and magnesium salt;

[0010] S2: Under an oxygen atmosphere, the composite raw materials are selectively oxidized and roasted at 850-950℃ for 1-4 hours to convert vanadium into water-soluble sodium vanadate and / or sodium-calcium composite vanadate that can release vanadium, thus obtaining composite roasted clinker.

[0011] S3: Water is used as a leaching agent to leach the composite roasted clinker, followed by solid-liquid separation, thereby achieving the separation of vanadium and chromium.

[0012] Furthermore, the vanadium-chromium slag is one or more of the following: vanadium-chromium reduction slag, chromium-containing vanadium slag, vanadium-chromium smelting slag, and vanadium-containing solid waste.

[0013] Furthermore, the sodium salt is one or more of sodium carbonate, sodium hydroxide, and sodium oxide.

[0014] Furthermore, the calcium salt is one or more of calcium carbonate, calcium oxide, calcium hydroxide, and limestone.

[0015] Furthermore, the magnesium salt is one or more of magnesium carbonate, magnesium oxide, magnesium hydroxide, magnesite, dolomite, and lightly calcined magnesium powder.

[0016] Furthermore, in step S1, based on the amount of total vanadium and total chromium in the vanadium-chromium slag, when sodium salt and calcium salt are used as mixed salts, the amount of sodium salt and calcium salt added simultaneously satisfies: 0.94≤n(Na) / n(V+Cr)≤1.76, 0.05≤n(Ca) / n(Cr)≤0.89.

[0017] When sodium and magnesium salts are used as a mixed salt, the amounts of sodium and magnesium salts added must simultaneously satisfy the following conditions: 0.94≤n(Na) / n(V+Cr)≤1.76, 0.05≤n(Mg) / n(Cr)≤0.89.

[0018] Furthermore, the composite raw materials need to be ball-milled and mixed before calcination.

[0019] Furthermore, in step S2, the oxygen atmosphere is a gas containing oxygen, and the volume fraction of oxygen in the gas is ≥15%.

[0020] Furthermore, in step S3, the volume-to-mass ratio of water to composite roasted clinker is (1~10) mL:1 g.

[0021] Furthermore, in step S3, the water immersion temperature is 75-90℃, and the immersion time is 1.5-2.5h.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. This invention regulates the phase transformation behavior of vanadium and chromium in vanadium-chromium slag during the oxidative roasting process by controlling the amount of sodium salt and calcium or magnesium salt added. Specifically, it converts vanadium in the vanadium-chromium slag into water-soluble vanadates (such as sodium vanadate and sodium-calcium composite vanadate), and stably retains chromium in the leaching residue as a poorly soluble chromium-containing phase (such as Cr2O3, FeCr2O4, MgCr2O4, Fe-Cr composite spinel, Mg-Cr composite spinel or chromium-containing solid solution), thereby achieving selective leaching of vanadium and solid-phase fixation of chromium during the water leaching stage, and thus achieving efficient separation of vanadium and chromium.

[0024] 2. This invention employs a water leaching method, avoiding acid consumption and equipment corrosion, effectively reducing production costs and improving the production environment. Simultaneously, this invention increases the vanadium leaching rate in vanadium-chromium slag and reduces the chromium content in the leachate, directly obtaining a high-vanadium, low-chromium leachate (vanadium leaching rate >80%, chromium leaching rate <5%). This effectively reduces the pressure on subsequent chromium removal and solution purification, and minimizes the risk of generating chromium-containing wastewater.

[0025] 3. This invention can achieve selective extraction of vanadium with only one roasting and one water immersion, effectively shortening the process flow, reducing equipment investment and production energy consumption, and is suitable for industrial production. Attached Figure Description

[0026] Figure 1 - The effect of sodium carbonate addition on vanadium-chromium leaching rate. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0028] Example 1

[0029] After drying the chromium-vanadium slag, Na₂CO₃ with n(Na) / n(V+Cr) = 0.384~2.306 was added, and the mixture was stirred evenly before ball milling. After being stirred evenly, the mixture was placed in an oxidative roasting furnace and roasted in an oxygen atmosphere at a temperature of 850℃ for 2 hours. The resulting roasted clinker was crushed to 100 mesh (>99%), and then leached with water as the leaching agent at a volume-to-mass ratio of 2 mL: 1 g at a water leaching temperature of 80℃ for 2 hours. After leaching, high-vanadium filtrate and high-chromium tailings were obtained. The residual vanadium and residual chromium content of the vanadium tailings were measured to obtain the vanadium-chromium leaching rate.

[0030] The results are as follows Figure 1As shown in the figure, with the increase of the n(Na) / n(V+Cr) molar ratio, the leaching rates of both vanadium and chromium continuously increase, indicating that vanadium and chromium are oxidized and converted into water-soluble salts during sodium roasting, exhibiting obvious simultaneous dissolution characteristics. When the molar ratio increases from 0.38 to 1.15, the vanadium leaching rate rapidly increases from about 32% to about 90%, while the chromium leaching rate also increases from about 1% to about 6%. Further increasing the sodium salt ratio gradually stabilizes the vanadium leaching rate at around 95%, while the chromium leaching rate further increases rapidly to nearly 60%. This indicates that although sodium roasting alone can achieve efficient vanadium leaching, it inevitably promotes the formation of water-soluble chromates of chromium, which then enters the leachate, making it difficult to achieve selective separation of vanadium and chromium during the roasting-water leaching stage.

[0031] Example 2

[0032] After drying the chromium-vanadium slag, sodium carbonate and calcium carbonate were added, with n(Na) / n(V+Cr)=1.384 and n(Ca) / (Cr)=0.170. After mixing evenly, the mixture was ball-milled and then placed in an oxidative roasting furnace for roasting under an oxygen atmosphere at a temperature of 900℃ for 2 hours. The resulting roasted clinker was crushed to 100 mesh (>99%) and then leached with water as the leaching agent at a volume-to-mass ratio of 2mL:1g at a water leaching temperature of 80℃ for 2 hours. After leaching, a high-vanadium filtrate and a high-chromium tailings were obtained. The residual vanadium and residual chromium content of the vanadium tailings were measured to obtain the vanadium-chromium leaching rate.

[0033] Example 3

[0034] This embodiment is the same as Embodiment 2, except that the amounts of sodium carbonate and calcium carbonate added are different, where n(Na) / n(V+Cr)=1.384 and n(Ca) / (Cr)=0.099.

[0035] Example 4

[0036] This embodiment is the same as Embodiment 2, except that the amount of sodium carbonate and calcium carbonate added is different, where n(Na) / n(V+Cr)=1.384 and n(Ca) / (Cr)=0.197.

[0037] Example 5

[0038] This embodiment is the same as Embodiment 2, except that the amount of sodium carbonate and calcium carbonate added is different, where n(Na) / n(V+Cr)=1.384 and n(Ca) / (Cr)=0.296.

[0039] Example 6

[0040] This embodiment is the same as Embodiment 2, except that the amount of sodium carbonate and calcium carbonate added is different, where n(Na) / n(V+Cr)=1.384 and n(Ca) / (Cr)=0.494.

[0041] Example 7

[0042] This embodiment is the same as Embodiment 2, except that the amount of sodium carbonate and calcium carbonate added is different, where n(Na) / n(V+Cr)=1.384 and n(Ca) / (Cr)=0.889.

[0043] Example 8

[0044] This embodiment is the same as Embodiment 2, except that the amounts of sodium carbonate and calcium carbonate added are different, where n(Na) / n(V+Cr)=1.175 and n(Ca) / (Cr)=0.197.

[0045] Example 9

[0046] This embodiment is the same as Embodiment 2, except that the amount of sodium carbonate and calcium carbonate added is different, where n(Na) / n(V+Cr)=1.537 and n(Ca) / (Cr)=0.197.

[0047] Example 10

[0048] This embodiment is the same as Embodiment 2, except that the amounts of sodium carbonate and calcium carbonate added are different, where n(Na) / n(V+Cr)=1.763 and n(Ca) / (Cr)=0.197.

[0049] Example 11

[0050] This embodiment is the same as Embodiment 2, except that the vanadium-chromium slag is a vanadium-chromium reduction slag.

[0051] Example 12

[0052] This embodiment is the same as Embodiment 2, except that the calcination temperature is 850℃.

[0053] Example 13

[0054] This embodiment is the same as Embodiment 2, except that the calcination temperature is 950℃.

[0055] Example 14

[0056] This embodiment is the same as Embodiment 2, except that magnesium carbonate is used instead of calcium carbonate.

[0057] Example 15

[0058] This embodiment is the same as Embodiment 2, except that calcium oxide is used instead of calcium carbonate, where n(Na) / n(V+Cr)=1.384 and n(Ca) / (Cr)=0.170.

[0059] Example 16

[0060] This embodiment is the same as Embodiment 2, except that calcium oxide is used instead of calcium carbonate, where n(Na) / n(V+Cr)=1.384 and n(Ca) / (Cr)=0.253.

[0061] Example 17

[0062] This embodiment is the same as embodiment 2, except that limestone is used instead of calcium carbonate, where n(Na) / n(V+Cr)=1.384 and n(Ca) / (Cr)=0.170.

[0063] Example 18

[0064] This embodiment is the same as Embodiment 2, except that limestone is used instead of calcium carbonate, where n(Na) / n(V+Cr)=1.384 and n(Ca) / (Cr)=0.253.

[0065] Comparative Example 1

[0066] This embodiment is the same as Embodiment 2, except that the amounts of sodium carbonate and calcium carbonate added are different, where n(Na) / n(V+Cr)=0.705 and n(Ca) / (Cr)=0.197.

[0067] Comparative Example 2

[0068] This embodiment is the same as Embodiment 2, except that the amounts of sodium carbonate and calcium carbonate added are different, where n(Na) / n(V+Cr)=2.351 and n(Ca) / (Cr)=0.197.

[0069] Comparative Example 3

[0070] This embodiment is the same as Embodiment 2, except that the amounts of sodium carbonate and calcium carbonate added are different, where n(Na) / n(V+Cr)=1.384 and n(Ca) / (Cr)=0.03.

[0071] Comparative Example 4

[0072] This embodiment is the same as Embodiment 2, except that the amount of sodium carbonate and calcium carbonate added is different, where n(Na) / n(V+Cr)=1.384 and n(Ca) / (Cr)=1.283.

[0073] Comparative Example 5

[0074] This embodiment is the same as Embodiment 2, except that the calcination temperature is 800℃.

[0075] Comparative Example 6

[0076] This embodiment is the same as Embodiment 2, except that the calcination temperature is 1000℃.

[0077] The vanadium leaching rates and chromium leaching rates of Examples 2-18 and Comparative Examples 1-6 are shown in the table below:

[0078] Example 2 Vanadium-chromium slag Calcium carbonate 900 1.39 0.170 92.47 1.39 Example 3 Vanadium-chromium slag Calcium carbonate 900 1.384 0.099 88.76 1.67 Example 4 Vanadium-chromium slag Calcium carbonate 900 1.384 0.197 91.64 1.58 Example 5 Vanadium-chromium slag Calcium carbonate 900 1.384 0.296 95.13 1.38 Example 6 Vanadium-chromium slag Calcium carbonate 900 1.384 0.494 92.64 1.02 Example 7 Vanadium-chromium slag Calcium carbonate 900 1.384 0.889 80.55 0.87 Example 8 Vanadium-chromium slag Calcium carbonate 900 1.175 0.197 89.25 2.18 Example 9 Vanadium-chromium slag Calcium carbonate 900 1.537 0.197 97.29 2.14 Example 10 Vanadium-chromium slag Calcium carbonate 900 1.763 0.197 97.23 4.09 Example 11 Vanadium-chromium reducing slag Calcium carbonate 900 1.39 0.170 90.34 1.55 Example 12 Vanadium-chromium slag Calcium carbonate 850 1.384 0.197 86.17 2.34 Example 13 Vanadium-chromium slag Calcium carbonate 950 1.384 0.197 89.64 4.78 Example 14 Vanadium-chromium slag Magnesium carbonate 900 1.39 0.170 92.35 1.37 Example 15 Vanadium-chromium slag Calcium oxide 900 1.384 0.170 91.06 1.52 Example 16 Vanadium-chromium slag Calcium oxide 900 1.384 0.253 93.21 1.43 Example 17 Vanadium-chromium slag limestone 900 1.384 0.170 90.98 1.60 Example 18 Vanadium-chromium slag limestone 900 1.384 0.253 93.48 1.47 Comparative Example 1 Vanadium-chromium slag Calcium carbonate 900 0.705 0.197 65.23 3.52 Comparative Example 2 Vanadium-chromium slag Calcium carbonate 900 2.351 0.197 98.02 12.62 Comparative Example 3 Vanadium-chromium slag Calcium carbonate 900 1.384 0.030 90.37 7.23 Comparative Example 4 Vanadium-chromium slag Calcium carbonate 900 1.384 1.283 69.42 0.63 Comparative Example 5 Vanadium-chromium slag Calcium carbonate 800 1.384 0.197 76.35 11.09 Comparative Example 6 Vanadium-chromium slag Calcium carbonate 1000 1.384 0.197 84.27 9.35

[0079] As can be seen from the table above: (1) As can be seen from Examples 3-7 and Comparative Examples 3-4, under the conditions of a certain amount of sodium carbonate added (i.e., n(Na) / n(V+Cr)=1.384) and a roasting temperature of 900℃, as the amount of calcium salt added (n(Ca) / n(Cr)) increased from 0.03 to 1.283, the chromium leaching rate continuously decreased from 7.23% to 0.63%; while the vanadium leaching rate showed a fluctuating change of first slightly decreasing (90.37%→88.76%), then increasing (to 95.13%), and then significantly decreasing (to 80.55% and 69.42%). This indicates that the addition of calcium salt changed the phenomenon of simultaneous oxidation and simultaneous dissolution of vanadium and chromium in the single sodium roasting process, and an appropriate amount of calcium salt can effectively inhibit the dissolution of chromium and promote its solidification in the leaching residue as a sparingly soluble phase; however, excessive calcium salt will promote the transformation of vanadium into a sparingly leached phase, resulting in a significant decrease in the vanadium leaching rate. Therefore, the amount of calcium salt added needs to be controlled within an appropriate range to ensure efficient vanadium leaching while simultaneously achieving the solidification and retention of chromium in the slag.

[0080] (2) As shown in Examples 4, 8-10 and Comparative Examples 1-2, under the conditions of n(Ca) / n(Cr)=0.197 and calcination temperature of 900℃, as n(Na) / n(V+Cr) increases from 0.705 to 2.351, the vanadium leaching rate increases from 65.23% to 98.02%, indicating that increasing the amount of sodium salt is beneficial to the oxidative decomposition of the vanadium-containing phase and the formation of the water-leached vanadium-containing phase. At the same time, the chromium leaching rate shows a trend of first decreasing and then increasing with the increase of sodium salt. When n(Na) / n(V+Cr) increases from 0.705 to 1.384, the chromium leaching rate decreases from 3.52% to 1.58%; as the ratio further increases to 1.537, 1.763 and 2.351, the chromium leaching rate increases to 2.14%, 4.09% and 12.62%, respectively. The above results indicate that insufficient sodium salt addition leads to incomplete vanadium phase transformation, resulting in a low vanadium leaching rate. Conversely, excessive sodium salt addition promotes the conversion of chromium to water-soluble chromates, significantly increasing the chromium leaching rate. This further suggests the need to control the addition amounts of sodium and calcium salts to promote efficient vanadium conversion and water leaching while inhibiting the conversion of soluble chromates. This ensures that chromium is primarily retained in the leaching residue as a sparingly soluble chromium-containing phase, thereby improving the selective separation of vanadium and chromium.

[0081] (3) As shown in Examples 4, 12-13, and Comparative Examples 5-6, under the conditions of n(Na) / n(V+Cr)=1.384 and n(Ca) / n(Cr)=0.197, the roasting temperature has a significant impact on the selective phase transformation of vanadium and chromium and the subsequent water leaching behavior. When the roasting temperature increases from 800℃ to 850℃ and 900℃, the vanadium leaching rate increases from 76.35% to 86.17% and 91.64%, while the chromium leaching rate decreases from 11.09% to 2.34% and 1.58%. This indicates that appropriately increasing the roasting temperature is beneficial to the oxidative decomposition of vanadium-containing phases in vanadium-chromium slag and the formation of soluble vanadates, while also promoting the transformation of chromium into insoluble chromium-containing phases and their retention in the leaching slag. When the roasting temperature was further increased to 950℃ and 1000℃, the vanadium leaching rate decreased to 89.64% and 84.27%, respectively, while the chromium leaching rate increased to 4.78% and 9.35%, respectively. This indicates that excessively high roasting temperatures weaken the selective conversion of vanadium and chromium, promote further oxidation of chromium to form water-soluble chromates, and may also cause clinker sintering, liquid phase formation, or the formation of vanadium-containing phases that are difficult to leach in water, thus leading to a decrease in vanadium leaching rate and an increase in chromium leaching rate. Therefore, when the amount of sodium and calcium salts added is constant, the roasting temperature should be controlled within a suitable range to balance efficient water leaching of vanadium and solid-phase retention of chromium.

[0082] Finally, it should be noted that the above embodiments of the present invention are merely illustrative examples and not intended to limit the implementation of the invention. Those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A method for selectively separating vanadium and chromium from vanadium-chromium slag, characterized in that, Specifically, the following steps are included: S1: Mix vanadium-chromium slag with mixed salt to obtain a composite mixed raw material, wherein the mixed salt is a mixture of sodium salt and calcium salt, or a mixture of sodium salt and magnesium salt; S2: Under an oxygen atmosphere, the composite raw materials are selectively oxidized and roasted at 850-950℃ for 1-4 hours to convert vanadium into water-soluble sodium vanadate and / or sodium-calcium composite vanadate that can release vanadium, thus obtaining composite roasted clinker. S3: Water is used as a leaching agent to leach the composite roasted clinker, followed by solid-liquid separation, thereby achieving the separation of vanadium and chromium.

2. A method for selectively separating vanadium and chromium from vanadium-chromium slag according to claim 1, characterized in that, The vanadium-chromium slag is one or more of the following: vanadium-chromium reduction slag, chromium-containing vanadium slag, vanadium-chromium smelting slag, and vanadium-containing solid waste.

3. A method for selectively separating vanadium and chromium from vanadium-chromium slag according to claim 1, characterized in that, The sodium salt is one or more of sodium carbonate, sodium hydroxide, and sodium oxide.

4. A method for selectively separating vanadium and chromium from vanadium-chromium slag according to claim 1, characterized in that, The calcium salt is one or more of calcium carbonate, calcium oxide, calcium hydroxide, and limestone.

5. A method for selectively separating vanadium and chromium from vanadium-chromium slag according to claim 1, characterized in that, The magnesium salt is one or more of magnesium carbonate, magnesium oxide, magnesium hydroxide, magnesite, dolomite, and lightly calcined magnesium powder.

6. A method for selectively separating vanadium and chromium from vanadium-chromium slag according to claim 1, characterized in that, In step S1, based on the amount of total vanadium and total chromium in the vanadium-chromium slag, when sodium salt and calcium salt are used as mixed salts, the amount of sodium salt and calcium salt added simultaneously satisfies: 0.94≤n(Na) / n(V+Cr)≤1.76, 0.05≤n(Ca) / n(Cr)≤0.

89. When sodium and magnesium salts are used as a mixed salt, the amounts of sodium and magnesium salts added must simultaneously satisfy the following conditions: 0.94≤n(Na) / n(V+Cr)≤1.76, 0.05≤n(Mg) / n(Cr)≤0.

89.

7. A method for selectively separating vanadium and chromium from vanadium-chromium slag according to claim 1, characterized in that, The composite raw materials need to be ball-milled and mixed before roasting.

8. A method for selectively separating vanadium and chromium from vanadium-chromium slag according to claim 1, characterized in that, In step S2, the oxygen atmosphere is a gas containing oxygen, and the volume fraction of oxygen in the gas is ≥15%.

9. A method for selectively separating vanadium and chromium from vanadium-chromium slag according to claim 1, characterized in that, In step S3, the volume-to-mass ratio of water to composite roasted clinker is (1~10) mL:1 g.

10. A method for selectively separating vanadium and chromium from vanadium-chromium slag according to claim 1, characterized in that, In step S3, the water immersion temperature is 75-90℃ and the immersion time is 1.5-2.5h.

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