A method for efficiently separating vanadium, chromium and iron from vanadium slag

Abstract

The invention discloses a method for efficiently separating vanadium, chromium and iron from vanadium slag, comprising the following steps: S1: grinding, grading and magnetically separating iron from vanadium slag to obtain vanadium-containing chromium fine powder; S2: sequentially performing oxidation roasting and atmospheric pressure acid leaching on the vanadium-containing chromium fine powder obtained in step S1; S3: performing liquid-solid separation on the acid leaching solution obtained in step S2 by suction filtration to obtain a filter cake and a filtrate, wherein the filter cake is sequentially washed and dried for chromium recovery; and the filtrate is used to recover vanadium through chemical precipitation. The invention separates vanadium, chromium and iron from vanadium slag through processes such as grinding and grading, magnetic separation, oxidation roasting and atmospheric pressure acid leaching. After the vanadium slag is subjected to grinding and grading treatment, the recovery rate of iron reaches more than 80%, and the recovery rate of finely ground magnetically separated iron reaches more than 10%, thereby achieving iron separation. In the optimal experimental results, the vanadium leaching rate is 97% and the chromium leaching rate is 0.5%. This process has the advantages of low equipment investment, simple operation and easy industrialization.

Description

Technical Field

[0001] The invention relates to separation and recovery of valuable metals by utilizing vanadium slag, belongs to the field of hydrometallurgical chemical industry, and particularly relates to a method for efficiently separating vanadium, chromium and iron from vanadium slag. Background Art

[0002] Vanadium and chromium are rare metals with high melting points. As important strategic resources, they are widely used in the three fields of steel metallurgy, ferroalloys and chemical industry. Vanadium-titanium magnetite is currently the most important and economical vanadium resource. The concentrate of vanadium-titanium magnetite is processed by blast furnace and converter to produce vanadium slag, which enriches vanadium.

[0003] At present, the main methods for extracting vanadium from vanadium slag produced by vanadium-titanium magnetite are: sodium roasting water leaching method and calcium roasting acid leaching method. The sodium roasting water leaching method is the mainstream process for extracting vanadium from vanadium slag. This method mainly adds sodium agents such as Na2SO4, Na2CO3, NaCl, NaOH to the vanadium slag, performs oxidative roasting, and converts the vanadium-containing phase in the vanadium slag into sodium vanadate, which is then leached out by water. Although the sodium roasting water leaching method is relatively simple in process, the addition of a large amount of sodium salt not only consumes a large amount of auxiliary materials and is costly, but also easily causes the softening and sintering of silica sand and the ringing of the kiln body, and at the same time hinders the further oxidation of vanadium, resulting in a low vanadium conversion rate. Generally, the single vanadium conversion rate is only 70%. In addition, the vanadium precipitation process produces a large amount of sodium-containing wastewater, which has high treatment costs. The calcification roasting and acid leaching process is to mix vanadium slag powder with calcifying agents such as CaCO3 and CaO, and then roast it at high temperature to convert the vanadium-containing phase into calcium vanadate, and then extract vanadium by acid leaching. Calcium silicate will be formed during the calcification roasting process, which will wrap part of the vanadium and reduce the leaching rate of vanadium.

[0004] Prior art 201310296932.0 discloses a method for extracting vanadium by activating high-calcium and high-phosphorus vanadium slag using nitric acid. Concentrated nitric acid is used to remove iron and calcium, and then acid leaching is performed again to extract vanadium. This method not only consumes a large amount of nitric acid and increases costs, but also increases energy consumption.

[0005] Prior art 201510763421.4 discloses a method for extracting vanadium and chromium from vanadium slag at low temperature and normal pressure. The vanadium in the vanadium slag is converted into sodium vanadate and the chromium is converted into sodium chromate by sodium reaction, and then the vanadium and chromium are extracted. However, the leaching rate of vanadium and chromium is only about 85%, and vanadium and chromium cannot be effectively utilized.

[0006] Prior art 201710551972.3 discloses a method for extracting chromium and vanadium from chromium-vanadium slag by a high-temperature roasting method, in which vanadium and chromium are extracted from vanadium slag by a combination of sodiumization and calcification roasting, wherein vanadium and chromium enter the acid leaching solution at the same time, and vanadium and chromium cannot be separated in one step. The subsequent separation of vanadium and chromium is more complicated and costly.

[0007] Therefore, the above-mentioned prior arts all have the following problems: 1) vanadium and chromium are simultaneously converted into soluble substances, the leaching solution contains vanadium and chromium, the leaching solution impurity removal is complicated, and the removal of chromium will result in the loss of some vanadium; 2) the vanadium leaching rate is low, resulting in a waste of resources. Summary of the invention

[0008] The object of the present invention is to provide a method for efficiently separating iron, vanadium and chromium, wherein the method comprises the steps of grinding classification, magnetic separation, oxidation roasting and acid leaching at normal pressure to obtain iron and vanadium products and prepare chromium raw materials respectively.

[0009] The present invention is achieved through the following technical solutions:

[0010] A method for efficiently separating vanadium, chromium and iron from vanadium slag comprises the following steps:

[0011] S1: Grinding, classifying and magnetically separating the vanadium slag to obtain vanadium-chromium-containing fine powder;

[0012] S2: the vanadium-chromium-containing fine powder obtained in step S1 is subjected to oxidation roasting and atmospheric pressure acid leaching in sequence;

[0013] S3: The acid leaching liquid obtained in step S2 is filtered to separate liquid from solid to obtain a filter cake and a filtrate. The filter cake is washed and dried in sequence for chromium recovery; and the filtrate is chemically precipitated to recover vanadium.

[0014] Preferably, in step S1, the mass contents of the main components in the vanadium slag are as follows: V2O5: 12% to 18%, TFe (total iron): 25% to 35%, CaO: 3% to 5%, MgO: 1% to 3%, MnO: 5% to 10%, Cr2O3: 4.5% to 12%, SiO2: 13% to 18%, and the remainder is impurities.

[0015] Preferably, in step S1, the vanadium slag is ground and classified to recover iron, and then further finely ground and magnetically separated to recover excess iron. The grinding mesh is controlled to 80-200 mesh, and the coarse-grained iron is recovered by 80-120 mesh screening. The fine powder below 120 mesh is recovered by magnetic separation, and the magnetic separation tailings are used as vanadium-chromium-containing fine powder. In actual operation, the particle size above 80-120 mesh is directly used as coarse-grained iron.

[0016] Different materials have different mechanical strengths, which results in different crushability. This is manifested in that for the same grinding time, the material with higher mechanical strength has a larger particle size. Compared with other materials in vanadium slag, pig iron has a greater mechanical strength, resulting in a coarser particle size under the same grinding conditions. By controlling the screening particle size, most of the iron can be removed.

[0017] Preferably, in step S2, the vanadium-chromium-containing fine powder obtained in step S1 is ground to a size of less than 400 meshes, and then oxidative roasting and atmospheric pressure acid leaching are performed in sequence. The fine grinding can be used as a mechanical activation process to reduce the particle size of the vanadium-chromium-containing fine powder to less than 400 meshes, which can increase the vanadium leaching rate in the subsequent acid leaching process.

[0018] Preferably, in step S2, the oxidation roasting temperature is 650-900°C, and the oxidation roasting time is 2-5h; the acid leaching temperature is 40-80°C, and the reaction time is 2-6h.

[0019] Preferably, in step S2, the acid leaching agent is one or more of nitric acid, sulfuric acid and hydrochloric acid, preferably nitric acid. The hydrochloric acid and sulfuric acid cannot be recycled, while nitric acid is easy to recycle and has good economic benefits. In actual operation, the amount of nitric acid is preliminarily determined based on the content of metal elements in the vanadium slag that can be oxidized by nitric acid and converted into ions, and then optimized through conditional tests, characterized by the vanadium leaching rate, to obtain the final amount of nitric acid for leaching.

[0020] Preferably, in step S3, the filter cake is subjected to reduction roasting and magnetic separation to recover chromium, and the filtrate is subjected to hydrolysis to precipitate vanadium, alkali dissolution to remove slag, ammonium salt precipitation of vanadium and calcination to obtain vanadium pentoxide.

[0021] Preferably, in step S3, the filter cake is washed 2-3 times with water, and the amount of washing water is 0.5-1.0 times the amount of slag.

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

[0023] The present invention provides a method for efficiently separating iron, vanadium and chromium from vanadium slag, which can effectively separate iron, vanadium and chromium from vanadium slag through grinding classification, magnetic separation, oxidative roasting and acid leaching at normal pressure. Grinding classification and magnetic separation are mainly used to separate iron, while oxidative roasting and acid leaching at normal pressure are mainly used to separate vanadium and chromium. The above method has a short process flow, and the key is that the process operation is simple and the equipment investment is small. Not only can iron be separated in one step, but vanadium and chromium can also be separated efficiently. Furthermore,

[0024] (1) About grinding, grading and magnetic separation process: The purpose of conventional grinding and grading is only to control the particle size. The raw material of the present invention is high-vanadium slag, which contains pig iron. Since pig iron is ductile, the particle size after grinding is relatively coarse. The vanadium slag is graded after grinding, and the coarse particle size is the iron product. The remaining fine particle size is obtained by magnetic separation to obtain residual iron, and the iron yield can reach more than 90%.

[0025] (2) Regarding the oxidation roasting process: the vanadium slag powder after iron removal is fully oxidized and roasted to oxidize the low-valent (Ш and Ⅳ) vanadium in the vanadium slag into high-valent vanadium (V) clinker. The high-valent vanadium clinker is subjected to normal pressure acid leaching and solid-liquid separation. The vanadium enters the acid leaching liquid and the chromium remains in the acid leaching slag, thus achieving vanadium-chromium separation. In the optimal experimental results, the vanadium leaching rate is 97% and the chromium leaching rate is 0.5%.

[0026] The reaction equations involved in the oxidation process of vanadium during roasting are shown in equations (1) to (3):

[0027] 4FeV2O4+O2=2Fe2O3+4V2O3 (1)

[0028] V2O3+O2=V2O5 (2)

[0029] 4M2VO4+O2=8MO+2V2O5 (M is magnesium, manganese, calcium, etc.) (3)

[0030] The reaction equation involved in the nitric acid leaching process is shown in formula (4):

[0031] V2O5+2HNO3=2VO2NO3+H2O (4)

[0032] Since vanadium and chromium in vanadium slag mainly exist in spinel structure, appropriate roasting conditions are controlled to make vanadium oxidize and migrate to the outside of the spinel structure, while chromium remains inside the spinel. Then, vanadium enters the acid leaching solution through leaching, while chromium remains in the slag phase.

[0033] (3) About the acid leaching process: The reagent used in the atmospheric pressure acid leaching of the present invention is nitric acid, which can leach low-valent vanadium. The leaching rate of vanadium is high, and the waste acid can be recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 The present invention is a flow chart of the method for efficiently separating vanadium, chromium and iron from vanadium slag. DETAILED DESCRIPTION

[0036] The following will describe the technical solutions and technical problems solved in the embodiments of the present invention in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0037] The main components and contents of the vanadium slag in the embodiment and the comparative example are as follows: TiO2: 9.82%, TFe: 27.55%, CaO: 3.92%, MgO: 1.34%, MnO: 9.79%, Al2O3: 2.46%, SiO2: 16.10%, and the remainder is impurities.

[0038] Example 1

[0039] A method for efficiently separating vanadium, chromium and iron from vanadium slag, the flow chart of which is as follows Figure 1 As shown, the following steps are included:

[0040] 200g of vanadium slag was ground for 10min, then passed through an 80-mesh sieve, and the sieved residue was 45.5g of iron. The sieved residue was further ground for 5min for magnetic separation to obtain 10.3g of iron concentrate and 140.6g of tailings;

[0041] Take the above tailings and grind them to less than 400 mesh, then carry out oxidation roasting, the roasting temperature is 700℃, the roasting time is 2h, then grind the roasted clinker, take 100g of vanadium slag roasted clinker, 150g of nitric acid with a mass concentration of 60% and 300g of water, add them into a 1000ml beaker respectively, slowly heat up from room temperature, react for 2 hours, the reaction temperature is 70℃, stir while acid leaching, and the stirring speed is 300r / min. After the reaction is completed, solid-liquid separation is carried out, the filter cake is washed, dried, ground and sieved, and then analyzed and tested, mainly analyzing the leaching rate of vanadium and chromium. Chromium mainly exists in the filter cake, and the subsequent reduction roasting-magnetic separation process can be used to recover chromium. Compared with the initial vanadium slag, the chromium leaching rate is 1.5%; vanadium mainly exists in the filtrate, and is subsequently recovered by chemical precipitation, and the vanadium leaching rate is 95.6%. Compared with vanadium slag, the iron recovery rate is 91.02%.

[0042] Example 2

[0043] 200g of vanadium slag was ground for 10min, then passed through a 100-mesh sieve, and the sieved residue was 48.3g of iron. The sieved residue was further ground for 5min for magnetic separation to obtain 7.8g of iron concentrate and 140.9g of tailings.

[0044] Take the above tailings and grind them to less than 400 mesh, then carry out oxidation roasting, the roasting temperature is 750 ℃, the roasting time is 2h, then grind the roasted clinker, take vanadium slag roasted clinker 100g, nitric acid 200g with a mass concentration of 60% and water 300g respectively, add them into a 1000ml beaker, slowly heat up from room temperature, react for 2 hours, the reaction temperature is 75 ℃, stir while acid leaching, and the stirring speed is 300r / min. After the reaction is completed, solid-liquid separation is carried out, the filter cake is washed, dried, ground and sieved, and then analyzed and tested. The leaching rate of vanadium is 96.3%, and the leaching rate of chromium is 1.0%. Compared with vanadium slag, the iron recovery rate is 91.60%.

[0045] Example 3

[0046] 200g of vanadium slag was ground for 15min, then passed through an 80-mesh sieve, and the sieved residue was 40.9g of iron. The sieved residue was further ground for 5min for magnetic separation to obtain 13.3g of iron concentrate and 142.4g of tailings;

[0047] Take the above tailings and grind them to less than 400 mesh, then carry out oxidation roasting, the roasting temperature is 800 ℃, the roasting time is 2h, then grind the roasted clinker, take vanadium slag roasted clinker 100g, nitric acid 150g with a mass concentration of 60% and water 300g, add them into a 1000ml beaker respectively, slowly heat up from room temperature, react for 2 hours, the reaction temperature is 70 ℃, stir while acid leaching, and the stirring speed is 300r / min. After the reaction is completed, solid-liquid separation is carried out, the filter cake is washed, dried, ground and sieved, and then analyzed and tested. The leaching rate of vanadium is 96.3%, and the leaching rate of chromium is 0.8%. Compared with vanadium slag, the iron recovery rate is 90.60%.

[0048] Example 4

[0049] 200g of vanadium slag was ground for 15min, then passed through a 100-mesh sieve, and the sieved residue was 44.2g of iron. The sieved residue was further ground for 5min for magnetic separation to obtain 10.5g of iron concentrate and 143.6g of tailings;

[0050] Take the above tailings and grind them to less than 400 mesh, then carry out oxidation roasting, the roasting temperature is 800 ℃, the roasting time is 2h, then grind the roasted clinker, take vanadium slag roasted clinker 100g, nitric acid 200g with a mass concentration of 60% and water 350g respectively, add them into a 1000ml beaker, slowly heat up from room temperature, react for 2 hours, the reaction temperature is 70 ℃, stir while acid leaching, and the stirring speed is 300r / min. After the reaction is completed, solid-liquid separation is carried out, the filter cake is washed, dried, ground and sieved, and then analyzed and tested. The leaching rate of vanadium is 97.3%, and the leaching rate of chromium is 0.53%. Compared with vanadium slag, the iron recovery rate is 90.75%.

[0051] Example 5

[0052] 200g of vanadium slag was ground for 15min, then passed through a 100-mesh sieve, and the sieved residue was 43.9g of iron. The sieved residue was further ground for 5min for magnetic separation to obtain 10.8g of iron concentrate and 143.1g of tailings.

[0053] Take the above tailings and grind them to less than 400 mesh, then carry out oxidation roasting, the roasting temperature is 850℃, the roasting time is 2h, then grind the roasted clinker, take 100g of vanadium slag roasted clinker, 200g of nitric acid with a mass concentration of 60% and 350g of water, add them into a 1000ml beaker respectively, slowly heat up from room temperature, react for 2 hours, the reaction temperature is 70℃, stir while acid leaching, and the stirring speed is 300r / min. After the reaction is completed, solid-liquid separation is carried out, the filter cake is washed, dried, ground and sieved, and then analyzed and tested. The leaching rate of vanadium is 96.1%, and the leaching rate of chromium is 0.61%. Compared with vanadium slag, the iron recovery rate is 90.95%.

[0054] Example 6

[0055] 200g of vanadium slag was ground for 10min, then passed through an 80-mesh sieve, and the sieved residue was 45.51g of iron. The sieved residue was further ground for 5min for magnetic separation to obtain 9.8g of iron concentrate and 142.1g of tailings.

[0056] Take the above tailings and grind them to less than 400 mesh, then carry out oxidation roasting, the roasting temperature is 900 ℃, the roasting time is 2h, then grind the roasted clinker, take vanadium slag roasted clinker 100g, nitric acid 200g with a mass concentration of 60% and water 300g respectively, add them into a 1000ml beaker, slowly heat up from room temperature, react for 2 hours, the reaction temperature is 80 ℃, stir while acid leaching, and the stirring speed is 300r / min. After the reaction is completed, solid-liquid separation is carried out, the filter cake is washed, dried, ground and sieved, and then analyzed and tested. The leaching rate of vanadium is 95.1%, and the leaching rate of chromium is 0.49%. Compared with vanadium slag, the iron recovery rate is 92.10%.

[0057] Comparative Example 1

[0058] 200g of vanadium slag was ground for 10min, then passed through an 80-mesh sieve, and the sieved residue was 44.98g of iron. The sieved residue was further ground for 5min for magnetic separation to obtain 9.5g of iron concentrate and 145.52g of tailings.

[0059] Take the above tailings and grind them to less than 200 mesh, then perform oxidation roasting, the roasting temperature is 700℃, the roasting time is 2h, then grind the roasted clinker, take 100g of vanadium slag roasted clinker, 150g of nitric acid with a mass concentration of 60% and 300g of water, add them into a 1000ml beaker respectively, slowly heat up from room temperature, react for 2 hours, the reaction temperature is 70℃, stir while acid leaching, and the stirring speed is 300r / min. After the reaction is completed, solid-liquid separation is performed, the filter cake is washed, dried, ground and sieved, and the vanadium and chromium are detected. Chromium mainly exists in the filter cake, and the chromium can be recovered by reduction roasting-magnetic separation process later. Compared with the initial vanadium slag, the chromium leaching rate is 1.20%; vanadium mainly exists in the filtrate, and is subsequently recovered by chemical precipitation, and the vanadium leaching rate is 89.31%.

[0060] Comparative Example 2

[0061] 200g of vanadium slag was ground for 10min, then passed through an 80-mesh sieve, and the sieved residue was 44.98g of iron. The sieved residue was further ground for 5min for magnetic separation to obtain 9.5g of iron concentrate and 145.52g of tailings.

[0062] Take the above tailings and grind them to less than 325 mesh, then perform oxidation roasting, the roasting temperature is 700℃, the roasting time is 2h, then grind the roasted clinker, take 100g of vanadium slag roasted clinker, 150g of nitric acid with a mass concentration of 60% and 300g of water, add them into a 1000ml beaker respectively, slowly heat up from room temperature, react for 2 hours, the reaction temperature is 70℃, stir while acid leaching, and the stirring speed is 300r / min. After the reaction is completed, solid-liquid separation is performed, the filter cake is washed, dried, ground and sieved, and the vanadium and chromium are detected. Chromium mainly exists in the filter cake, and the chromium can be recovered by reduction roasting-magnetic separation process later. Compared with the initial vanadium slag, the chromium leaching rate is 1.38%; vanadium mainly exists in the filtrate, and is subsequently recovered by chemical precipitation, and the vanadium leaching rate is 93.78%.

[0063] The applicant has found that the key to improving the vanadium leaching rate is to mechanically activate (finely grind) the vanadium-containing chromium fine powder after separating the iron. In Comparative Examples 1 and 2, after separating the iron, the tailings were ground to 200 mesh and 325 mesh, respectively. Compared with the examples, the vanadium leaching rate was reduced. However, the chromium entered the filtrate from the filter cake, and the leaching rate was significantly increased.

[0064] The above is 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 the scope of protection of the present invention.

Claims

1. A method for efficiently separating vanadium, chromium and iron from vanadium slag, characterized in that: The following steps are involved: S1: Grinding, classifying and magnetically separating the vanadium slag to obtain vanadium-chromium-containing fine powder; In the step S1, the grinding mesh is controlled to be 80-200 mesh, the coarse-grained iron is recovered by 80-120 mesh screening, the fine powder below 120 mesh is recovered by magnetic separation, and the magnetic separation tailings are used as vanadium-chromium-containing fine powder; S2: grinding the vanadium-chromium-containing fine powder obtained in step S1 to a size of less than 400 mesh, and then sequentially performing oxidative roasting and atmospheric pressure acid leaching; S3: The acid leaching liquid obtained in step S2 is filtered to separate liquid from solid to obtain a filter cake and a filtrate. The filter cake is washed and dried in sequence for chromium recovery; and the filtrate is chemically precipitated to recover vanadium.

2. The method according to claim 1, characterized in that In step S1, the mass contents of the main components in the vanadium slag are as follows: V2O5: 12% to 18%, TFe: 25% to 35%, CaO: 3% to 5%, MgO: 1% to 3%, MnO: 5% to 10%, Cr2O3: 4.5% to 12%, SiO2: 13% to 18%, and the remainder is impurities.

3. The method according to claim 1, characterized in that: In the step S2, the oxidation roasting temperature is 650-900°C, and the oxidation roasting time is 2-5h; the acid leaching temperature is 40-80°C, and the reaction time is 2-6h.

4. The method according to claim 1, characterized in that: In step S2, the reagent for atmospheric pressure acid leaching is nitric acid.

5. The method according to claim 1, characterized in that In step S3, chromium is recovered from the filter cake by reduction roasting and magnetic separation.

6. The method according to claim 5, characterized in that The filter cake is washed 2-3 times with water volume being 0.5-1.0 times of the slag volume.

7. The method according to claim 1, characterized in that In step S3, the filtrate is subjected to hydrolysis to precipitate vanadium, alkali dissolution to remove slag, ammonium salt precipitation of vanadium and calcination to obtain vanadium pentoxide.

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