Method for co-extracting vanadium and chromium from high-chromium vanadium slag and application thereof

Abstract

The application provides a method for co-extracting vanadium and chromium from high-chromium vanadium slag and application thereof. The method comprises the following steps: roasting high-chromium vanadium slag and calcium salt to obtain roasted clinker, leaching the roasted clinker with a leaching agent to obtain a leaching solution, cooling the leaching solution to obtain sodium orthovanadate and a crystallization mother liquor; adding calcium oxide to the crystallization mother liquor to obtain a chromium-containing solution, performing first reduction on the chromium-containing solution to obtain chromium hydroxide, and performing first calcination on the chromium hydroxide to obtain chromium trioxide; mixing the sodium orthovanadate, water and carbon dioxide to obtain sodium metavanadate, sequentially performing transformation and second reduction on the sodium metavanadate, and performing second calcination to obtain a reduction clinker; mixing the reduction clinker, washing water and sodium bicarbonate mother liquor to obtain a sodium-containing solution and primary vanadium trioxide, and washing the primary vanadium trioxide to obtain vanadium trioxide. The application realizes high-value conversion of high-chromium vanadium slag, and simultaneously considers simplicity and economy, and no high ammonia nitrogen, high salt water and ammonia-containing waste gas are generated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metallurgical chemical industry, and particularly relates to a method for co-extracting vanadium and chromium from high-chromium vanadium slag and application thereof. BACKGROUND

[0002] Vanadium is an important rare metal element, known as industrial monosodium glutamate. Due to its high tensile strength, hardness and fatigue resistance, it has become one of the most common and effective strengthening elements for micro-alloying. The main products of vanadium include vanadium pentoxide, vanadium trioxide, vanadium-nitrogen alloy, vanadium-iron alloy, vanadium-aluminum alloy, etc., which are widely used in steel, chemical industry, national defense, electronics, manufacturing, energy storage, medicine, catalysis and other fields. However, chromium often occurs in vanadium ore, and the two have similar physical and chemical properties, making separation very difficult. The resource utilization of vanadium-chromium slag, especially high-chromium slag, has always been a problem hindering the development of the vanadium industry. Although many researchers have tried, they have not achieved good results.

[0003] CN112430740A discloses a method for strengthening vanadium-chromium separation by using calcium salt and manganese salt to co-roast vanadium slag. The method mixes vanadium slag, calcium salt and manganese salt, then high-temperature roasts, leaches, precipitates with ammonium salt, calcines to obtain vanadium pentoxide, then reacts leaching residue, graphite powder and calcium oxide at 1600℃ to obtain chromium-iron alloy, and recycles manganese salt from mother liquor by electrolysis to realize cyclic utilization. However, this method inevitably produces high ammonia-nitrogen and high-sulfur wastewater and ammonia-containing tail gas, and the electrolytic recovery of manganese requires high equipment and the obtained chromium-iron alloy has many impurities.

[0004] CN114854988A discloses a method for selectively separating vanadium and chromium from vanadium-chromium material using CO2. The method uses carbon dioxide to selectively oxidize vanadium in vanadium-chromium-containing raw materials to achieve vanadium-chromium separation. The specific steps are as follows: mix vanadium-chromium material and carbonate, press into briquettes, put into a shaft furnace and pass in carbon dioxide for roasting, cool and crush, dissolve to obtain vanadium-containing solution and chromium-containing residue, recover vanadium from vanadium-containing solution by precipitation method, and prepare chromium alloy from chromium-containing residue. Vanadium is oxidized at the same time as part of the chromium, and the oxidized chromium will enter the product and wastewater, not only reducing the product quality, but also increasing the difficulty of wastewater treatment. This method also has high ammonia-nitrogen and high-sulfur wastewater and ammonia-containing tail gas.

[0005] CN110358920A discloses a method for separating vanadium from vanadium-chromium waste residue, which comprises the following steps: grinding the vanadium-chromium waste residue, mixing the ground residue with a reducing agent composed of water, sodium sulfite and sodium bisulfite in a sealed reactor, mixing the reduced slurry with concentrated sulfuric acid to obtain a vanadium-rich liquid and a chromium-containing leaching residue, and then precipitating vanadium from the vanadium-rich liquid by using an ammonium salt to obtain a vanadium product. This method avoids high-temperature roasting of vanadium-chromium waste residue and has lower energy consumption than traditional processes, but 5-20% of vanadium is not leached, which not only wastes resources but also causes unnecessary trouble for the subsequent treatment of chromium-containing leaching residue, and the fate of the chromium-containing waste residue is not mentioned.

[0006] CN109207728A discloses a method for extracting chromium and vanadium from chromium-containing vanadium residue by high-temperature roasting, which uses a mixture of calcium salt and sodium salt as an additive during the roasting of vanadium-chromium residue to convert vanadium in the chromium-containing vanadium residue into calcium vanadate and chromium into sodium chromate, and then uses water to leach the roasted material to obtain a chromium-containing leaching solution and a vanadium-rich roasted material. The vanadium-rich roasted material is leached with an ammonium salt solution or a sodium salt solution to obtain a vanadium-containing leaching solution and waste residue. However, due to the uncontrollable nature of the reaction, sodium vanadate may also be produced during the roasting process, resulting in poor separation of vanadium and chromium.

[0007] Therefore, most technical personnel have invested a lot of research in the separation of vanadium and chromium from vanadium-chromium waste residue, but the problems of high-salt high-ammonia-nitrogen wastewater and ammonia-containing waste gas emission have not been solved, and the separation of vanadium and chromium is poor, with vanadium being prepared only as di vanadium pentoxide and chromium residue being prepared only as chromium-iron alloy or being harmlessly treated. How to convert vanadium-chromium residue, especially high-chromium vanadium residue, into high-value-added products without generating three wastes has become an urgent problem for technical personnel in the field. SUMMARY

[0008] The purpose of the present application is to provide a method for co-extracting vanadium and chromium from high-chromium vanadium residue and its application.

[0009] To achieve this purpose, the present application adopts the following technical solutions:

[0010] One of the purposes of the present application is to provide a method for co-extracting vanadium and chromium from high-chromium vanadium residue, which comprises the following steps:

[0011] (1) roasting high-chromium vanadium residue with calcium salt to obtain roasted material, and then leaching the roasted material with a leaching agent to obtain a leaching solution, and cooling the leaching solution to obtain sodium orthovanadate and a crystallization mother liquor;

[0012] (2) adding calcium oxide to the crystallization mother liquor obtained in step (1) to obtain a chromium-containing solution, and then performing a first reduction on the chromium-containing solution to obtain chromium hydroxide, and then performing a first calcination on the chromium hydroxide to obtain chromium sesquioxide;

[0013] (3) mixing the sodium orthovanadate, water and carbon dioxide obtained in step (2) to obtain sodium metavanadate, sequentially performing transformation and second reduction on the sodium metavanadate to obtain a reduced clinker, mixing the reduced clinker, washing water and sodium bicarbonate mother liquor to obtain a sodium-containing solution and primary vanadic oxide, and washing the primary vanadic oxide to obtain vanadic oxide.

[0014] The present application provides a method for co-extracting vanadium and chromium from high-chromium vanadium slag, which converts the high-chromium vanadium slag into vanadic oxide and vanadic oxide products, realizes high-value conversion of high-chromium vanadium slag, and simultaneously considers simplicity and economy without generating high ammonia nitrogen, high salt water and ammonia-containing waste gas.

[0015] The method provided by the present application separates vanadium and sodium according to the solubility difference between vanadium and chromium and sodium salt and calcium salt, successfully prepares vanadic oxide and vanadic oxide products by introducing reducing agents and transformation agents, and realizes high-value utilization of high-chromium vanadium slag. Compared with the traditional method, the present application eliminates the introduction of sulfur and ammonium, avoids the generation of high salt and high ammonia nitrogen wastewater from the source, and realizes zero discharge of wastewater and solid waste through the closed cycle of sodium salt and transformation agent. In addition, the entire system does not generate ammonia-containing waste gas. The entire process is simple to operate, has high conversion rate and low cost, the required equipment is conventional equipment in the chemical industry, the industrial process is easy to implement, and the economic and environmental benefits are significant.

[0016] The products obtained by the method provided by the present application have high purity, the purity of the vanadic oxide product meets the requirements of class I qualified products in HG / T 2775-2010, and the purity of the vanadic oxide product meets the requirements of grade V2O366 in GB / T 40301-2021.

[0017] As a preferred technical solution of the present application, the calcium salt in step (1) includes calcium oxide and / or calcium carbonate.

[0018] Preferably, the total calcium to total vanadium molar ratio in the roasting in step (1) is (1-1.4):1, wherein the molar ratio can be 1:1, 1.1:1, 1.2:1, 1.3:1 or 1.4:1, etc., but is not limited to the listed values, and other values not listed within this range are also applicable.

[0019] Preferably, the temperature of the roasting is 700-1000°C, wherein the temperature can be 700°C, 750°C, 800°C, 850°C, 900°C, 950°C or 1000°C, etc., but is not limited to the listed values, and other values not listed within this range are also applicable.

[0020] As a preferred technical solution of the present application, the leaching in step (1) includes mixing the roasting clinker, the extraction agent, calcium vanadate, the reducing mother liquor and sodium bicarbonate.

[0021] The leaching agent of step (1) comprises any one or a combination of at least two of sodium carbonate, sodium bicarbonate or sodium hydroxide, wherein the typical but non-limiting examples of the combination include a combination of sodium carbonate and sodium bicarbonate, a combination of sodium bicarbonate and sodium hydroxide, or a combination of sodium carbonate and sodium hydroxide, etc.

[0022] Preferably, the total sodium and total vanadate molar ratio in the reaction system is controlled to be (1-1.4): 1 in the leaching of step (1), wherein the molar ratio can be 1:1, 1.1:1, 1.2:1, 1.3:1 or 1.4:1, etc., but not only limited to the listed values, and other values not listed within the range of values are also applicable.

[0023] Preferably, the temperature of the leaching of step (1) is 20-80°C, wherein the temperature can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C, etc., but not only limited to the listed values, and other values not listed within the range of values are also applicable, preferably 20-50°C.

[0024] As a preferred technical solution of the present application, the amount of calcium oxide added in step (2) is controlled to make the total calcium and total vanadate molar ratio in the reaction system be (1-1.4): 1, wherein the molar ratio can be 1:1, 1.1:1, 1.2:1, 1.3:1 or 1.4:1, etc., but not only limited to the listed values, and other values not listed within the range of values are also applicable.

[0025] Preferably, calcium oxide is added to the crystallization mother liquor of step (2) to obtain a chromium-containing solution and calcium vanadate.

[0026] Preferably, the calcium vanadate is used for the leaching of step (1).

[0027] As a preferred technical solution of the present application, the first reduction uses a first reducing agent.

[0028] Preferably, the first reducing agent comprises any one or a combination of at least two of formic acid, oxalic acid, formaldehyde, hydrazine hydrate, methanol or ethanol, wherein the typical but non-limiting examples of the combination include a combination of formic acid and oxalic acid, a combination of oxalic acid and formaldehyde, a combination of formaldehyde and hydrazine hydrate, a combination of hydrazine hydrate and methanol, or a combination of methanol and ethanol, etc.

[0029] Preferably, the amount of the first reducing agent added is to make all the high-valence chromium be converted into trivalent chromium.

[0030] Preferably, calcium oxide is added to the crystallization mother liquor of step (2) to obtain a chromium-containing solution and a reduction mother liquor.

[0031] Preferably, the reduction mother liquor is used for the leaching of step (1).

[0032] Preferably, the temperature of the first calcination of step (2) is 900-1600 °C, wherein the temperature can be 900 °C, 1000 °C, 1100 °C, 1200 °C, 1300 °C, 1400 °C, 1500 °C, or 1600 °C, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0033] As a preferred technical solution of the present application, the transformation agent is used in step (3).

[0034] Preferably, the transformation agent includes any one or a combination of at least two of aluminum oxide, aluminum hydroxide, or aluminum phosphate, wherein the combination typically but non-limiting examples include a combination of aluminum oxide and aluminum hydroxide, a combination of aluminum hydroxide and aluminum phosphate, or a combination of aluminum oxide and aluminum phosphate, etc.

[0035] Preferably, the molar ratio of total aluminum to total sodium in the reaction system is controlled to be (1-1.4):1 in the transformation, wherein the molar ratio can be 1:1, 1.1:1, 1.2:1, 1.3:1, or 1.4:1, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0036] As a preferred technical solution of the present application, the second reducing agent is used in step (3).

[0037] Preferably, the second reducing agent of step (3) includes any one or a combination of at least two of hydrogen, CO, coal gas, or natural gas, wherein the combination typically but non-limiting examples include a combination of hydrogen and CO, a combination of CO and coal gas, or a combination of coal gas and natural gas, etc.

[0038] Preferably, the temperature of the second reducing agent addition for reduction of step (2) is 600-900 °C, wherein the temperature can be 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, or 900 °C, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0039] As a preferred technical solution of the present application, the temperature of the second calcination of step (3) is 600-1000 °C, wherein the temperature can be 600 °C, 700 °C, 800 °C, 900 °C, or 1000 °C, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0040] Preferably, the washing of step (3) is countercurrent washing.

[0041] As a preferred technical scheme of the present application, carbon dioxide is introduced into the sodium-containing solution in step (3), and the pH is controlled to be 10.0-12.0, wherein the pH can be 10.0, 10.2, 10.4, 10.6, 10.8, 11.0, 11.2, 11.4, 11.6, 11.8 or 12.0, etc., but is not limited to the listed values, and other values not listed in the range are also applicable, to obtain a transformation agent and a recovery mother liquor.

[0042] Preferably, the transformation agent is used in the transformation of step (3).

[0043] Preferably, carbon dioxide is continuously introduced into the recovery mother liquor, and the pH is controlled to be 7.0-9.0, wherein the pH can be 7.0, 7.2, 7.4, 7.6, 7.8, 8.0, 8.2, 8.4, 8.6, 8.8 or 9.0, etc., but is not limited to the listed values, and other values not listed in the range are also applicable, to obtain sodium bicarbonate and a sodium bicarbonate mother liquor.

[0044] Preferably, the sodium bicarbonate is used in the leaching of step (1).

[0045] The second object of the present application is to provide an application of the method for co-extracting vanadium and chromium from high-chromium vanadium slag according to the first object, which is applied to the field of metallurgical chemical technology.

[0046] Compared with the prior art, the present application has the following beneficial effects:

[0047] (1) The method provided by the present application directly converts high-chromium vanadium slag into high-value chromium trioxide and vanadium trioxide products. The present application does not require the introduction of sulfur and ammonium, thereby avoiding the generation of high-salt and high-ammonia-nitrogen wastewater from the source, and achieving zero discharge of wastewater and solid waste through the closed circulation of sodium salt and transformation agent. In addition, the entire system does not generate ammonia-containing waste gas. The entire process is simple to operate, has high conversion rate and low cost, the required equipment is conventional equipment in the chemical field, the industrial process is easy to implement, and the economic and environmental benefits are significant.

[0048] (2) The products obtained by the method provided by the present application have high purity, the purity of the chromium trioxide product meets the requirements of the I-class qualified product in HG / T 2775-2010, and the purity of the vanadium trioxide product meets the requirements of the V2O366 grade in GB / T 40301-2021. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 is a flowchart of the method for co-extracting vanadium and chromium from high-chromium vanadium slag in embodiments 1-10 of the present application. DETAILED DESCRIPTION

[0050] The technical solutions of the present application are further illustrated below by specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations on the present application.

[0051] Embodiment 1

[0052] The present embodiment provides a method for co-extracting vanadium and chromium from high-chromium vanadium slag as shown in the flow chart, which comprises the following steps: Figure 1 The method for co-extracting vanadium and chromium from high-chromium vanadium slag as shown in the flow chart, which comprises the following steps:

[0053] (1) roasting the high-chromium vanadium slag and calcium salt at 900℃, controlling the molar ratio of total calcium to total vanadium in the reaction system to be 1.2:1, mixing the roasted clinker with leaching agent, calcium vanadate, reduction mother liquor and sodium bicarbonate, controlling the molar ratio of total sodium to total vanadate in the reaction system to be 1.1:1, leaching at 40℃ to obtain leaching tailings and leaching liquor, cooling and crystallizing the leaching liquor to obtain sodium orthovanadate and crystallization mother liquor;

[0054] (2) adding calcium oxide to the crystallization mother liquor, controlling the molar ratio of total calcium to total vanadate in the reaction system to be 1.1:1, obtaining calcium vanadate and chromium-containing solution, adding formic acid to the chromium-containing solution to convert all high-valence chromium into trivalent chromium, obtaining reduction mother liquor and chromium hydroxide, returning the reduction mother liquor to step (1), and calcining the chromium hydroxide to obtain chromium sesquioxide;

[0055] (3) mixing the sodium orthovanadate obtained in step (1), water and carbon dioxide to convert the sodium orthovanadate into sodium metavanadate, and uniformly mixing with a conversion agent, controlling the molar ratio of total aluminum to total sodium in the reaction system to be 1-1.2:1, and then calcining with hydrogen at 750℃ to obtain reduction clinker; mixing the obtained reduction clinker, washing water and sodium bicarbonate mother liquor to obtain sodium-containing solution and primary chromium sesquioxide, countercurrently washing the primary chromium sesquioxide with water to obtain chromium sesquioxide product, passing carbon dioxide into the obtained sodium-containing solution to control the pH to be 11, obtaining conversion agent and recovery mother liquor, returning the conversion agent to step (3), and continuously passing carbon dioxide into the recovery mother liquor to control the pH to be 8, obtaining sodium bicarbonate and sodium bicarbonate mother liquor.

[0056] Embodiment 2

[0057] The present embodiment provides a method for co-extracting vanadium and chromium from high-chromium vanadium slag as shown in the flow chart, which comprises the following steps: Figure 1 The method for co-extracting vanadium and chromium from high-chromium vanadium slag as shown in the flow chart, which comprises the following steps:

[0058] (1) roasting the high-chromium vanadium slag and calcium salt at 1000℃, controlling the molar ratio of total calcium to total vanadium in the reaction system to be 1.1:1, mixing the roasted clinker with leaching agent, calcium vanadate, reduction mother liquor and sodium bicarbonate, controlling the molar ratio of total sodium to total vanadate in the reaction system to be 1.2:1, leaching at 50℃ to obtain leaching tailings and leaching liquor, cooling and crystallizing the leaching liquor to obtain sodium orthovanadate and crystallization mother liquor;

[0059] (2) adding calcium oxide to the crystallization mother liquor, controlling the molar ratio of total calcium to total vanadate in the reaction system to be 1.2:1, to obtain calcium vanadate and a chromium-containing solution, adding oxalic acid to the chromium-containing solution to convert all high-valence chromium into trivalent chromium, to obtain a reduction mother liquor and chromium hydroxide, returning the reduction mother liquor to step (1), and calcining the chromium hydroxide to obtain chromium sesquioxide;

[0060] (3) mixing the sodium orthovanadate obtained in step (1), water and carbon dioxide to convert the sodium orthovanadate into sodium metavanadate and mix the sodium metavanadate with the conversion agent, controlling the molar ratio of total aluminum to total sodium in the reaction system to be 1.1:1, and then calcining with CO at 800°C to obtain reduction clinker, mixing the reduction clinker obtained, washing water and sodium bicarbonate mother liquor to obtain a sodium-containing solution and primary vanadium sesquioxide, washing the primary vanadium sesquioxide with water in countercurrent to obtain vanadium sesquioxide product, introducing carbon dioxide into the obtained sodium-containing solution to control the pH to be 10 to obtain a conversion agent and a recovery mother liquor, returning the conversion agent to step (3), and continuously introducing carbon dioxide into the recovery mother liquor to control the pH to be 7 to obtain sodium bicarbonate and sodium bicarbonate mother liquor.

[0061] Example 3

[0062] The present embodiment provides a method for co-extracting vanadium and chromium from high-chromium vanadium slag as shown in the flowchart, the method comprising the following steps: Figure 1 The flowchart shows a method for co-extracting vanadium and chromium from high-chromium vanadium slag, the method comprising the following steps:

[0063] (1) calcining the high-chromium vanadium slag and calcium salt at 700°C, controlling the molar ratio of total calcium to total vanadium in the reaction system to be 1.3:1, mixing the calcined clinker with leaching agent, calcium vanadate, reduction mother liquor and sodium bicarbonate, controlling the molar ratio of total sodium to total vanadate in the reaction system to be 1.1:1, leaching at 20-50°C to obtain leaching tailings and leaching liquor, and cooling and crystallizing the leaching liquor to obtain sodium orthovanadate and crystallization mother liquor;

[0064] (2) adding calcium oxide to the crystallization mother liquor, controlling the molar ratio of total calcium to total vanadate in the reaction system to be 1.1:1, to obtain calcium vanadate and a chromium-containing solution, adding formaldehyde to the chromium-containing solution to convert all high-valence chromium into trivalent chromium, to obtain a reduction mother liquor and chromium hydroxide, returning the reduction mother liquor to step (1), and calcining the chromium hydroxide to obtain chromium sesquioxide;

[0065] (3) mixing the sodium orthovanadate, water and carbon dioxide obtained in step (1) to convert the sodium orthovanadate into sodium metavanadate and mix the sodium metavanadate with the conversion agent uniformly, controlling the molar ratio of total aluminum and total sodium in the reaction system to be 1.3:1, then calcining with coal gas at 600℃ to obtain reduced clinker, mixing the reduced clinker, washing water and sodium bicarbonate mother liquor to obtain a sodium-containing solution and primary vanadic oxide, washing the primary vanadic oxide with water in countercurrent to obtain vanadic oxide product, passing carbon dioxide into the obtained sodium-containing solution to control the pH to be 12 to obtain conversion agent and recovery mother liquor, returning the conversion agent to step (3), continuously passing carbon dioxide into the recovery mother liquor to control the pH to be 8.5 to obtain sodium bicarbonate and sodium bicarbonate mother liquor.

[0066] Example 4

[0067] This example is identical to Example 1 except that the molar ratio of total sodium and total vanadate in the reaction system in step (1) is replaced by 1:1.

[0068] Example 5

[0069] This example is identical to Example 1 except that the molar ratio of total calcium and total vanadate in the reaction system in step (2) is replaced by 1.4:1.

[0070] Example 6

[0071] This example is identical to Example 1 except that the molar ratio of total aluminum and total sodium in the reaction system in step (3) is replaced by 1:1.

[0072] Example 7

[0073] This example is identical to Example 1 except that the pH of the solution is controlled to be 9.0 when recovering sodium bicarbonate in step (3).

[0074] Example 8

[0075] This example is identical to Example 1 except that the molar ratio of total sodium and total vanadate in the reaction system in step (1) is replaced by 1.7:1.

[0076] Example 9

[0077] This example is identical to Example 1 except that the molar ratio of total calcium and total vanadate in the reaction system in step (2) is replaced by 0.7:1.

[0078] Example 10

[0079] This example is identical to Example 1 except that the molar ratio of total aluminum and total sodium in the reaction system in step (3) is replaced by 0.8:1.

[0080] The purity of the chromium trioxide and vanadium trioxide products of Examples 1-10 was tested, and the test results are shown in Table 1.

[0081] Table 1

[0082] Purity of chromium trioxide Purity of vanadium trioxide Example 1 98.8％ 66.7％ Example 2 98.8％ 66.7％ Example 3 98.5％ 66.4％ Example 4 98.3％ 66.2％ Example 5 98.5％ 66.7％ Example 6 98.4％ 66.1％ Example 7 98.6％ 66.5％ Example 8 96.3％ 64.7％ Example 9 85％ 66.5％ Example 10 98.3％ 62.1％

[0083] It can be seen from the above table that the purity of the chromium trioxide prepared in Examples 1-7 all meet the requirements of the Class I qualified product in HG / T 2775-2010, and the purity of the vanadium trioxide products prepared in Examples 1-7 all meet the requirements of the V2O366 grade in GB / T 40301-2021. Among them, compared with Example 1, in Example 5, too much calcium oxide is added in step (2), which results in a large amount of residual calcium oxide and enters the calcium vanadate in the form of solid phase, and enters the leaching tailings in the vanadium-chromium dissolution, which does not affect the purity of the chromium trioxide, but affects the energy consumption and the utilization rate of calcium, that is, it adversely affects the economy. Compared with Example 1, in Example 7, the pH of the mother liquor in step (3) is too high, which results in only a small amount of sodium bicarbonate being crystallized and precipitated, which does not affect the purity of sodium bicarbonate, but affects the recovery rate of sodium, that is, it adversely affects the economy.

[0084] The content of the chromium trioxide in Example 8 of the present application does not meet the requirements of the Class I qualified product in HG / T 2775-2010, and the vanadium content of the obtained vanadium trioxide product also does not meet the requirements of the V2O366 grade in GB / T 40301-2021.

[0085] The purity of the chromium trioxide in Example 9 of the present application does not meet the requirements of the Class I qualified product in HG / T 2775-2010, and the purity of the obtained vanadium trioxide product meets the requirements of the V2O366 grade in GB / T 40301-2021. In addition, the amount of calcium oxide added in Example 9 is seriously insufficient, vanadium is not completely precipitated, and vanadium is still contained in the chromium-containing solution, which will affect the quality of the chromium trioxide product.

[0086] The chromium trioxide in Example 10 of the present application meets the requirements of the Class I qualified product in HG / T 2775-2010, and the purity of the obtained vanadium trioxide product does not meet the requirements of the V2O366 grade in GB / T 40301-2021. In addition, compared with Example 1, in Example 10, the amount of the transformation agent is insufficient, sodium metavanadate cannot be completely converted into vanadium trioxide, which results in part entering the vanadium trioxide product, thereby reducing the quality.

[0087] The method provided by the application realizes the separation of vanadium and sodium according to the solubility difference between vanadium and chromium and sodium salt and calcium salt, and successfully prepares chromium sesquioxide and vanadium sesquioxide products by introducing a reducing agent and a transformation agent, and realizes the high-value utilization of high-chromium vanadium slag. Compared with the traditional method, the application eliminates the introduction of sulfur and ammonium, avoids the generation of high-salt and high-ammonia nitrogen wastewater from the source, and realizes zero discharge of wastewater and solid waste through the closed cycle of sodium salt and transformation agent. In addition, the entire system does not produce ammonia-containing waste gas. The entire process is simple to operate, has high conversion rate and low cost, the required equipment is conventional equipment in the chemical field, the industrial process is easy to realize, and the economic and environmental benefits are significant; the product obtained by the method provided by the application has high purity, the purity of the chromium sesquioxide product meets the requirements of HG / T 2775-2010 for type I qualified products, and the purity of the vanadium sesquioxide product meets the requirements of GB / T 40301-2021 for grade V2O366.

[0088] The applicant declares that the above is only a specific embodiment of the application, but the protection scope of the application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the application, which can be easily thought of by any person skilled in the art, falls within the protection scope and disclosure scope of the application.

Claims

1. A method for high-chromium vanadium slag vanadium-chromium co-extraction, characterized in that, The method comprises the following steps: (1) roasting high-chromium vanadium slag and calcium salt to obtain roasted clinker, and then leaching the roasted clinker with a leaching agent to obtain a leaching solution, and cooling the leaching solution to obtain sodium orthovanadate and a crystallization mother liquor; (2) adding calcium oxide to the crystallization mother liquor obtained in step (1) to obtain a chromium-containing solution and calcium vanadate, and performing first reduction on the chromium-containing solution to obtain chromium hydroxide and a reduction mother liquor, and performing first calcination on the chromium hydroxide to obtain chromium sesquioxide; (3) mixing sodium orthovanadate obtained in step (1), water and carbon dioxide to obtain sodium metavanadate, and then mixing the sodium metavanadate and a transformation agent, and sequentially performing transformation and second reduction, and then performing second calcination to obtain reduction clinker, and mixing the reduction clinker, washing water and sodium bicarbonate mother liquor to obtain a sodium-containing solution and primary vanadic oxide, and washing the primary vanadic oxide to obtain vanadic oxide; the transformation agent comprises any one or a combination of at least two of aluminum oxide, aluminum hydroxide or aluminum phosphate; In step (1), the molar ratio of total sodium to total vanadate in the reaction system is controlled to be (1-1.4):1; in step (2), the amount of calcium oxide added is controlled to make the molar ratio of total calcium to total vanadate in the reaction system be (1-1.4):1; and in step (3), the molar ratio of total aluminum to total sodium in the reaction system is controlled to be (1-1.4):

1.

2. The method of claim 1, wherein, The calcium salt in step (1) comprises calcium oxide and / or calcium carbonate.

3. The method of claim 1, wherein, In the roasting in step (1), the molar ratio of total calcium to total vanadium in the reaction system is controlled to be (1-1.4):

1.

4. The method of claim 1, wherein, The roasting temperature is 700-1000°C.

5. The method of claim 1, wherein, The leaching in step (1) comprises mixing the roasted clinker, the leaching agent, calcium vanadate, the reduction mother liquor and sodium bicarbonate.

6. The method of claim 1, wherein, The leaching agent in step (1) comprises any one or a combination of at least two of sodium carbonate, sodium bicarbonate or sodium hydroxide.

7. The method of claim 1, wherein, The leaching temperature in step (1) is 20-80°C.

8. The method of claim 7, wherein, The leaching temperature in step (1) is 20-50°C.

9. The method of claim 1, wherein, The first reducing agent comprises any one or a combination of at least two of formic acid, oxalic acid, formaldehyde, hydrazine hydrate, methanol or ethanol.

10. The method of claim 9, wherein, The amount of the first reducing agent is controlled to make all high-valence chromium be converted into trivalent chromium.

11. The method of claim 9, wherein, The first calcination temperature in step (2) is 900-1600°C.

12. The method of claim 1, wherein, The second reducing agent in step (3) comprises any one or a combination of at least two of hydrogen, CO, coal gas or natural gas.

13. The method of claim 1, wherein, The second reducing agent is added at a temperature of 600-900°C.

14. The method of claim 13, wherein, The second calcination temperature in step (3) is 600-1000°C.

15. The method of claim 13, wherein, The washing in step (3) is countercurrent washing.

16. The method of claim 1, wherein, Carbon dioxide is introduced into the sodium-containing solution to control the pH to be 10.0-12.0, so as to obtain a transformation agent and a recovery mother liquor.

17. The method of claim 1, wherein, The transformation agent is used for the transformation in step (3).

18. The method of claim 1, wherein, Carbon dioxide is continuously introduced into the recovery mother liquor to control the pH to be 7.0-9.0, so as to obtain sodium bicarbonate and a sodium bicarbonate mother liquor.

19. The method of claim 18, wherein, The sodium bicarbonate is used for the leaching in step (1).

20. The method of claim 18, wherein, ​ 21. The method of claim 20, wherein, ​ 22. Use of a process for vanadium-chromium co-extraction from high-chromium vanadium slag according to any one of claims 1 to 21, characterized in that, The method of high-chromium vanadium slag vanadium-chromium co-extraction is applied to the technical field of metallurgical chemical industry.

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