A process for vanadium extraction by roasting and leaching of composite salts from coal shale.

Abstract

This invention discloses a vanadium extraction process for shale coal through composite salt roasting and leaching, relating to the fields of mineral processing and metallurgy. The invention includes the following steps: Step 1: Crushing vanadium-bearing shale coal ore to below 3mm, preheating at 350℃ for 30min, roasting at 650~700℃ for oxidative decarburization for 40~60min, then cooling and grinding to a particle size less than 0.07mm to obtain decarburized powder. The flue gas generated during roasting is used for preheating the vanadium-bearing shale coal ore after dust removal. Step 2: Mixing the decarburized powder from Step 1 with composite additives in a certain proportion and placing it in a disc granulator for pelletizing. This invention reduces the emission of harmful gases during shale coal roasting by employing a decarburization followed by oxidative roasting process, using sodium sulfate instead of chlorine-containing roasting agents, and improving the vanadium conversion rate by adding steel slag powder and manganese dioxide to catalyze the oxidation of low-valent vanadium. The resulting vanadium-bearing leachate contains fewer impurity ions and has a high water leaching rate; it also has good industrial feasibility and is easy to promote on a large scale.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing and metallurgical technology, and in particular relates to a vanadium extraction process for shale coal composite salt roasting-leaching. Background Technology

[0002] Vanadium-bearing coal is one of my country's main vanadium mineral resources. With the expanding use of vanadium in industries such as iron and steel smelting, aerospace, chemical industry and batteries, the market demand for vanadium is increasing day by day. In order to transform the resource advantages of vanadium-bearing coal into economic advantages, a large number of explorations, developments and scientific research have been carried out.

[0003] Vanadium-bearing coal shale has a complex composition, with diverse forms and valence states of vanadium. Studies show that the main component of vanadium-bearing coal shale is quartz, followed by carbonaceous and clay minerals (kaolinite, mica-like minerals, etc.), and also pyrite, garnet minerals, and dolomite. Vanadium in coal shale is mainly precipitated as V. 3+ Al with isomorphic form of six-coordinate substitution 3+ It exists within the mica lattice and has a robust structure.

[0004] To extract vanadium from coal shale, the following steps must be taken: detach low-valent vanadium from the mica lattice; use an appropriate oxidizing atmosphere to transform acid- and alkali-insoluble trivalent vanadium V(III) and tetravalent vanadium V(IV) into water-soluble pentavalent vanadium V(V), facilitating vanadium leaching; combine the high-valent vanadium with appropriate reactants to form stable vanadium-containing compounds; and select suitable leaching conditions to transfer the vanadium-containing compounds from the solid to the liquid, separating them from the residue.

[0005] Currently, the existing technologies for vanadium extraction from coal roasting mainly include:

[0006] Chinese invention patent document CN101260459B discloses a "vanadium extraction roasting process from shale coal," specifically involving a vanadium extraction roasting process from shale coal. The technical solution is as follows: First, vanadium-containing shale coal ore with a V₂O₅ grade of 0.7–1.3 wt% is crushed to 0–3 mm, decarbonized, and then 10–17 wt% NaCl and 3–7 wt% Na₂CO₃ are added to the ore. Next, 1–3 wt% FeVO₃ is added to the ore, and the mixture is homogenized and ground to 100–150 mesh. Then, the temperature is raised to 730–880℃ for 0.5–2.5 hours, and roasted at a constant temperature for 1–2 hours, followed by natural cooling to obtain roasted ore. The decarbonization rate is 70–80 wt%, and the vanadium conversion rate is over 90%.

[0007] Chinese invention patent document CN102162041A discloses "a method for roasting vanadium-containing coal using a rotary hearth furnace". The invention involves mixing, crushing, and finely grinding vanadium-containing raw materials with additives, then adding a binder and mixing evenly to form raw material balls. After drying the raw material balls, they are placed in a rotary hearth furnace for oxidative roasting. The temperature of the effective roasting zone in the rotary hearth furnace is controlled at 750℃~900℃, the oxygen content is controlled at 3%~15%, and the residence time of the raw material balls in the effective roasting zone is controlled at 1~4 hours. This process oxidizes the low-valent vanadium in the coal to pentavalent vanadium. The roasted clinker is then cooled and used for V2O5 leaching.

[0008] Chinese invention patent document CN104561608A discloses a method for vanadium extraction by mixed roasting of carbonaceous shale and biomass. The method includes the following steps: selecting shale, grinding, grading by particle size, drying, and mixing the shale; using corn stalks as biomass, cutting them into sections, drying them at a constant temperature in a drying oven, and then pulverizing them using a pulverizer; using Na2CO3 and CaCO3 as additives, grinding the two agents separately; mixing the carbonaceous shale, corn stalk powder, and additives to obtain a mixture; turning on the high-temperature resistance furnace program control device, placing the mixture into the high-temperature resistance furnace for reaction, and cooling the reactants to room temperature to obtain the vanadium-enriched material.

[0009] However, current roasting processes have problems such as the reaction of additives with vanadium oxides to produce harmful gases such as hydrogen chloride and chlorine, which pollute the environment and corrode equipment. Furthermore, the vanadium leaching rate is not high, and there are difficulties in the subsequent treatment of tailings. Summary of the Invention

[0010] The purpose of this invention is to provide a vanadium extraction process through roasting and leaching of composite salts from coal stone, in order to solve the existing problems: the current roasting process has the problem of harmful gases such as hydrogen chloride and chlorine being generated by the reaction of additives with vanadium oxides, which pollutes the environment and corrodes the equipment, and the vanadium leaching rate is not high, resulting in difficulties in the subsequent treatment of tailings.

[0011] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0012] This invention relates to a vanadium extraction process for shale coal composite salt roasting-leaching, comprising the following steps:

[0013] Step 1: Crush the vanadium-bearing coal ore to less than 3mm, preheat it at 350℃ for 30min, roast it at 650~700℃ for oxidation and decarburization for 40~60min, then cool and grind it to a particle size of less than 0.07mm to obtain decarburized powder. The flue gas generated during roasting is used to preheat the vanadium-bearing coal ore after dust removal.

[0014] Step 2: Mix the decarbonized powder from Step 1 with the composite additive in a certain proportion, place it in a disc granulator for pelletizing, and control the pellet size to be 12-20mm to obtain pellet material.

[0015] Step 3: Put the pellets into the pusher kiln, preheat at 350℃ for 30 minutes, blow in air, and oxidize and roast at 750~800℃ for 1~2 hours. After the reaction, the low-valent vanadium is oxidized to the pentavalent, and roasted clinker is obtained. The flue gas generated during the roasting process is used to preheat the pellets after dust removal.

[0016] Step 4: Grind the roasted clinker obtained in Step 3 to a particle size of less than 0.09 mm, and then perform two water leaching processes. After water leaching, solid and liquid separation is performed to obtain water leaching residue and water leaching liquid.

[0017] Step 5: Extract the aqueous extract obtained in Step 4 with organic phase A, then back-extract and recrystallize to obtain sodium vanadate. Organic phase A and back-extraction solution are recycled. The extracted aqueous extract is used to absorb and purify the flue gas exhaust gas from Step 1 and Step 3.

[0018] Step Six: Dissolve the sodium vanadate obtained in Step Five in hot water at 50℃, controlling the sodium vanadate solution concentration to 1~1.5 mol / L. Add 3 mol / L sulfuric acid to adjust the pH of the solution to 5.5, then continue heating to 85℃. Add a certain proportion of melamine, stir for 5 min, add 3 mol / L sulfuric acid to adjust the pH of the solution to 2, and maintain the temperature for 40 min. During all reactions, maintain the stirring speed at 400 r / min. Filter to obtain the supernatant, wash the vanadium-containing precipitate with distilled water to obtain a vanadium-containing filter cake. The vanadium-containing filter cake is dried and calcined at 550℃ for 120 min to obtain vanadium pentoxide product.

[0019] Furthermore, in step two, the amount of composite additive added is 5-8 wt% of the decarbonized powder.

[0020] Furthermore, the composite additive is composed of sodium carbonate, sodium sulfate, converter steel slag powder, and manganese dioxide;

[0021] The sodium carbonate content is 50-60 wt%, the sodium sulfate content is 20-30 wt%, the converter steel slag powder content is 10-25 wt%, and the manganese dioxide content is 10-25 wt%.

[0022] Furthermore, the conditions for water immersion in step four are: immersion temperature 85 ℃, immersion time 30 ~ 60 min, liquid-to-solid ratio 3 ~ 4 L / kg, and stirring speed 200 r / min.

[0023] Furthermore, in step five, the extraction of organic phase A is carried out by preparing dodecyltrimethylammonium chloride, n-hexanol, and sulfonated kerosene in a volume ratio of 3:1:2.

[0024] Furthermore, step five, which involves extraction, back-extraction, and recrystallization, includes the following steps:

[0025] The aqueous extract was extracted twice with organic phase A, and then back-extracted with 2 mol / L sodium carbonate solution to obtain a back-extract. Sodium vanadate crystals were obtained by cooling the back-extract to 5 °C.

[0026] Furthermore, in step six, the molar ratio of melamine to sodium vanadate is 1:4 to 1:3.

[0027] Furthermore, the V2O5 content in the vanadium-bearing coal ore is greater than 0.8 wt%.

[0028] The present invention has the following beneficial effects:

[0029] 1. This invention adopts a decarbonization followed by oxidation roasting process, and uses sodium sulfate instead of chlorine-containing roasting agent, which reduces the emission of harmful gases during the roasting of coal stone. By adding steel slag powder and manganese dioxide to catalyze the oxidation of low-valent vanadium, the vanadium conversion rate is improved. The resulting vanadium-containing leachate has fewer impurity ions and a high water leaching rate.

[0030] 2. The quaternary ammonium salt extractant used in this invention has good solubility, is easy to prepare, and has a single-stage extraction rate of over 91%, which simplifies the process, reduces production costs, and has significant economic benefits.

[0031] 3. This invention uses melamine as a vanadium precipitant to react with vanadium to generate vanadium precipitate, allowing most of the vanadium to enter the precipitate, thus achieving effective vanadium precipitation in high-concentration vanadium solution with a precipitation rate of more than 98%. The amount of melamine used as the vanadium precipitant is small, the cost is low, and no ammonia nitrogen wastewater is generated, making it environmentally friendly.

[0032] 4. The roasting-leaching vanadium extraction process of the present invention can obtain vanadium pentoxide products with V2O5 content ≥ 98.5% wt, leaching rate ≥ 90%, and total recovery rate ≥ 81%. It has good industrial feasibility and is easy to promote on a large scale. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0035] 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.

[0036] Example 1

[0037] A vanadium extraction process for shale coal composite salt roasting-leaching is described in this embodiment as follows: Figure 1 As shown;

[0038] A sample of vanadium-bearing coal from Hubei Province has a vanadium content of 0.85% by weight and a carbon content of 15.23%.

[0039] To achieve this, follow these steps:

[0040] (1) The vanadium-containing coal ore is crushed to less than 3 mm, preheated at 350℃ for 30 min, roasted at 650℃ for 60 min, then cooled and ground to a particle size of less than 0.07 mm to obtain decarbonized powder. The flue gas generated during the roasting process is used to preheat the vanadium-containing coal ore after dust removal.

[0041] (2) Mix the decarburized powder from the previous step with the additives (sodium carbonate, sodium sulfate, converter steel slag powder, and manganese dioxide in a mass ratio of 6:2:1:1) until uniform; the amount of the composite additive added is 5 wt% of the decarburized powder. The additives are mixed in a certain proportion and placed in a disc granulator for pelletizing, controlling the pellet size to be 12-20 mm, to obtain pellet material;

[0042] (3) The pellets are placed in a pusher kiln, preheated at 350℃ for 30 min, air is blown in, and oxidized and roasted at 780℃ for 2 h. After the reaction, the low-valent vanadium is oxidized to the pentavalent, and roasted clinker is obtained. The flue gas generated during the roasting process is used to preheat the pellets after dust removal.

[0043] (4) Grind the roasted clinker obtained in the previous step to a particle size of less than 0.09 mm, and then perform two water leaching processes. The leaching temperature is 85 ℃, the leaching time is 40 min, the liquid-solid ratio is 3 L / kg, and the stirring speed is 200 r / min. After water leaching, the solid and liquid are separated to obtain water leaching residue and water leaching liquid.

[0044] (5) The aqueous extract obtained in the previous step is extracted twice with organic phase A (dodecyltrimethylammonium chloride, n-hexanol and sulfonated kerosene in a volume ratio of 3:1:2). Then, the extracted organic phase A is back-extracted with 2 mol / L sodium carbonate solution to obtain back-extract. The back-extract is cooled to 5 °C to obtain sodium vanadate crystals. Organic phase A and back-extract are recycled. The extracted aqueous extract is used to absorb and purify the flue gas tail gas in steps one and three.

[0045] (6) Dissolve the sodium vanadate obtained in the previous step in hot water at 50°C, control the concentration of the sodium vanadate solution to be 1~1.5 mol / L, add 3 mol / L sulfuric acid to adjust the pH of the solution to 5.5, and then continue heating to 85°C. Add melamine with 32% (molar ratio) sodium vanadate, stir for 5 min, add 3 mol / L sulfuric acid to adjust the pH of the solution to 2, and keep warm for 40 min. During all reactions, the stirring speed is maintained at 400 r / min. Filter to obtain the supernatant, wash the vanadium-containing precipitate with distilled water to obtain a vanadium-containing filter cake. The vanadium-containing filter cake is dried and calcined at 550°C for 120 min to obtain vanadium pentoxide product.

[0046] In this embodiment, vanadium pentoxide product with V2O5 content of 98.59% wt, leaching rate of 91.37%, and total recovery rate of 82.52% was obtained.

[0047] Example 2

[0048] A vanadium extraction process for shale coal composite salt roasting-leaching is described in this embodiment as follows: Figure 1 As shown;

[0049] A sample of vanadium-bearing coal from Hunan Province has a vanadium content of 0.93% by weight and a carbon content of 15.62%.

[0050] To achieve this, follow these steps:

[0051] (1) The vanadium-containing coal ore is crushed to less than 3 mm, preheated at 350°C for 30 min, roasted at 680°C for oxidative decarburization for 50 min, then cooled and ground to a particle size of less than 0.07 mm to obtain decarburized powder. The flue gas generated during the roasting process is used to preheat the vanadium-containing coal ore after dust removal.

[0052] (2) Mix the decarburized powder from the previous step with the additives (sodium carbonate, sodium sulfate, converter steel slag powder, and manganese dioxide in a mass ratio of 6:1.5:1.5:1) evenly; the amount of the composite additive added is 5 wt% of the decarburized powder. The additives are mixed in a certain proportion and placed in a disc granulator for pelletizing, controlling the pellet size to be 12-20 mm, to obtain pellet material;

[0053] (3) The pellets are placed in a pusher kiln, preheated at 350℃ for 30 min, air is blown in, and oxidized and roasted at 780℃ for 2 h. After the reaction, the low-valent vanadium is oxidized to the pentavalent, and roasted clinker is obtained. The flue gas generated during the roasting process is used to preheat the pellets after dust removal.

[0054] (4) Grind the roasted clinker obtained in the previous step to a particle size of less than 0.09 mm, and then perform two water leaching processes. The leaching temperature is 85 ℃, the leaching time is 40 min, the liquid-solid ratio is 3 L / kg, and the stirring speed is 200 r / min. After water leaching, the solid and liquid are separated to obtain water leaching residue and water leaching liquid.

[0055] (5) The aqueous extract obtained in the previous step is extracted twice with organic phase A (dodecyltrimethylammonium chloride, n-hexanol and sulfonated kerosene in a volume ratio of 3:1:2). Then, the extracted organic phase A is back-extracted with 2 mol / L sodium carbonate solution to obtain back-extract. The back-extract is cooled to 5 °C to obtain sodium vanadate crystals. Organic phase A and back-extract are recycled. The extracted aqueous extract is used to absorb and purify the flue gas tail gas in steps one and three.

[0056] (6) Dissolve the sodium vanadate obtained in the previous step in hot water at 50°C, control the concentration of the sodium vanadate solution to be 1~1.5 mol / L, add 3 mol / L sulfuric acid to adjust the pH of the solution to 5.5, and then continue heating to 85°C. Add melamine with 36% (molar ratio) sodium vanadate, stir for 5 min, add 3 mol / L sulfuric acid to adjust the pH of the solution to 2, and keep warm for 40 min. During all reactions, the stirring speed is maintained at 400 r / min. Filter to obtain the supernatant, wash the vanadium-containing precipitate with distilled water to obtain a vanadium-containing filter cake. The vanadium-containing filter cake is dried and calcined at 550°C for 120 min to obtain vanadium pentoxide product.

[0057] In this embodiment, vanadium pentoxide product with V2O5 content of 98.56% wt, leaching rate of 90.97%, and total recovery rate of 81.86% was obtained.

[0058] Example 3

[0059] A vanadium extraction process for shale coal composite salt roasting-leaching is described in this embodiment as follows: Figure 1 As shown;

[0060] A sample of vanadium-bearing coal from Guangxi Province has a vanadium content of 0.89% by weight and a carbon content of 15.91%.

[0061] To achieve this, follow these steps:

[0062] (1) The vanadium-containing coal ore is crushed to less than 3 mm, preheated at 350℃ for 30 min, roasted at 680℃ for oxidative decarburization for 50 min, then cooled and ground to a particle size of less than 0.07 mm to obtain decarburized powder. The flue gas generated during the roasting process is used to preheat the vanadium-containing coal ore after dust removal.

[0063] (2) Mix the decarburized powder from the previous step with the additives (sodium carbonate, sodium sulfate, converter steel slag powder, and manganese dioxide in a mass ratio of 6:1.5:1.5:1.5) until homogeneous; the amount of the composite additive added is 6 wt% of the decarburized powder. The additives are mixed in a certain proportion and placed in a disc granulator for pelletizing, controlling the pellet size to be 12-20 mm to obtain pellet material;

[0064] (3) The pellets are placed in a pusher kiln, preheated at 350℃ for 30 minutes, air is blown in, and oxidized and roasted at 800℃ for 2 hours. After the reaction, the low-valent vanadium is oxidized to the pentavalent, and roasted clinker is obtained. The flue gas generated during the roasting process is used to preheat the pellets after dust removal.

[0065] (4) Grind the roasted clinker obtained in the previous step to a particle size of less than 0.09 mm, and then perform two water leaching processes. The leaching temperature is 85 ℃, the leaching time is 40 min, the liquid-solid ratio is 3 L / kg, and the stirring speed is 200 r / min. After water leaching, the solid and liquid are separated to obtain water leaching residue and water leaching liquid.

[0066] (5) The aqueous extract obtained in the previous step is extracted twice with organic phase A (dodecyltrimethylammonium chloride, n-hexanol and sulfonated kerosene in a volume ratio of 3:1:2). Then, the extracted organic phase A is back-extracted with 2 mol / L sodium carbonate solution to obtain back-extract. The back-extract is cooled to 5 °C to obtain sodium vanadate crystals. Organic phase A and back-extract are recycled. The extracted aqueous extract is used to absorb and purify the flue gas tail gas in steps one and three.

[0067] (6) Dissolve the sodium vanadate obtained in the previous step in hot water at 50°C, control the concentration of the sodium vanadate solution to be 1~1.5 mol / L, add 3 mol / L sulfuric acid to adjust the pH of the solution to 5.5, and then continue heating to 85°C. Add melamine with 35% (molar ratio) sodium vanadate, stir for 5 min, add 3 mol / L sulfuric acid to adjust the pH of the solution to 2, and keep warm for 40 min. During all reactions, the stirring speed is maintained at 400 r / min. Filter to obtain the supernatant, wash the vanadium-containing precipitate with distilled water to obtain a vanadium-containing filter cake. The vanadium-containing filter cake is dried and calcined at 550°C for 120 min to obtain vanadium pentoxide product.

[0068] In this embodiment, vanadium pentoxide product with V2O5 content of 98.92% wt, leaching rate of 91.11%, and total recovery rate of 82.25% was obtained.

[0069] Example 4

[0070] A vanadium extraction process for shale coal composite salt roasting-leaching is described in this embodiment as follows: Figure 1 As shown;

[0071] Includes the following steps:

[0072] Step 1: Crush the vanadium-bearing coal ore to less than 3mm, preheat it at 350℃ for 30min, roast it at 650~700℃ for oxidation and decarburization for 40~60min, then cool and grind it to a particle size of less than 0.07mm to obtain decarburized powder. The flue gas generated during roasting is used to preheat the vanadium-bearing coal ore after dust removal.

[0073] Here, the V2O5 content in the vanadium-bearing coal ore is greater than 0.8 wt%;

[0074] Step 2: Mix the decarbonized powder from Step 1 with the composite additive in a certain proportion, place it in a disc granulator for pelletizing, and control the pellet size to be 12-20mm to obtain pellet material.

[0075] The amount of composite additive can be 5-8 wt% of the decarbonized powder.

[0076] The composite additive is specifically composed of sodium carbonate, sodium sulfate, converter steel slag powder, and manganese dioxide;

[0077] The sodium carbonate content can be 50-60 wt%, the sodium sulfate content can be 20-30 wt%, the converter steel slag powder content can be 10-25 wt%, and the manganese dioxide content can be 10-25 wt%.

[0078] Step 3: Place the pellets into a pusher kiln, preheat at 350°C for 30 minutes, blow in air, and oxidize and roast at 750~800°C for 1~2 hours. After the reaction, the low-valent vanadium is oxidized to the pentavalent, and roasted clinker is obtained. The flue gas generated during the roasting process is used to preheat the pellets after dust removal.

[0079] The roasting process mainly involves the following reactions:

[0080] V₂O₃ + O₂ → V₂O₅

[0081] V₂O₅ + Na₂CO₃ → NaVO₃ + CO₂↑

[0082] Step 4: Grind the roasted clinker obtained in Step 3 to a particle size of less than 0.09 mm, and then perform two water leaching processes. After water leaching, solid and liquid separation is performed to obtain water leaching residue and water leaching liquid.

[0083] Here, the conditions for water immersion are: immersion temperature 85 ℃, immersion time 30 ~ 60 min, liquid-solid ratio 3 ~ 4 L / kg, and stirring speed 200 r / min;

[0084] Step 5: Extract the aqueous extract obtained in Step 4 with organic phase A, then back-extract and recrystallize to obtain sodium vanadate. Organic phase A and back-extraction solution are recycled. The extracted aqueous extract is used to absorb and purify the flue gas exhaust gas from Step 1 and Step 3.

[0085] The organic phase A for extraction is prepared by mixing dodecyltrimethylammonium chloride, n-hexanol, and sulfonated kerosene in a volume ratio of 3:1:2.

[0086] In this embodiment, the extraction, back-extraction, and recrystallization process specifically includes the following steps:

[0087] The aqueous extract was extracted twice with organic phase A, and then back-extracted with 2 mol / L sodium carbonate solution to obtain back-extract. Sodium vanadate crystals were obtained by cooling the back-extract to 5 °C.

[0088] Step Six: Dissolve the sodium vanadate obtained in Step Five in 50°C hot water, controlling the sodium vanadate solution concentration to 1~1.5 mol / L. Add 3 mol / L sulfuric acid to adjust the pH of the solution to 5.5, then continue heating to 85°C. Add a certain proportion of melamine, stir for 5 min, add 3 mol / L sulfuric acid to adjust the pH of the solution to 2, and maintain the temperature for 40 min. During all reactions, maintain the stirring speed at 400 r / min. Filter to obtain the supernatant, wash the vanadium-containing precipitate with distilled water to obtain a vanadium-containing filter cake. The vanadium-containing filter cake is dried and calcined at 550°C for 120 min to obtain vanadium pentoxide product.

[0089] The molar ratio of melamine to sodium vanadate can be 1:4 to 1:3, and no specific limit is made here.

[0090] In summary, this invention reduces the emission of harmful gases during the roasting of coal by employing a decarbonization followed by oxidation roasting process and replacing chlorine-containing roasting agents with sodium sulfate. By adding steel slag powder and manganese dioxide to catalyze the oxidation of low-valent vanadium, the vanadium conversion rate is improved, resulting in a vanadium-containing leachate with fewer impurity ions and a high water leaching rate.

[0091] The quaternary ammonium salt extractant used has good solubility, is easy to prepare, and has a single-stage extraction rate of over 91%, which simplifies the process, reduces production costs, and has significant economic benefits.

[0092] Melamine is used as a vanadium precipitant to react with vanadium to form vanadium precipitate, allowing most of the vanadium to enter the precipitate. This achieves effective vanadium precipitation of high-concentration vanadium solution with a precipitation rate of more than 98%. The amount of melamine used as the vanadium precipitant is small, the cost is low, and no ammonia nitrogen wastewater is generated, making it environmentally friendly.

[0093] Moreover, it has good industrial feasibility and is easy to promote on a large scale.

[0094] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0095] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A kind of stone coal composite salt roasting-leaching vanadium extraction process, it is characterized in that, Includes the following steps: Step 1: Crush the vanadium-bearing coal ore to less than 3mm, preheat it at 350℃ for 30min, roast it at 650~700℃ for oxidation and decarburization for 40~60min, then cool and grind it to a particle size of less than 0.07mm to obtain decarburized powder. The flue gas generated during roasting is used to preheat the vanadium-bearing coal ore after dust removal. Step 2: Mix the decarbonization powder from Step 1 with the composite additive in a certain proportion, and place it in a disc granulator for pelletizing. Control the pellet size to be 12-20mm to obtain pellet material; wherein, the amount of composite additive added is 5-8 wt% of the decarbonization powder. Step 3: Put the pellets into the pusher kiln, preheat at 350℃ for 30 minutes, blow in air, and oxidize and roast at 750~800℃ for 1~2 hours. After the reaction, the low-valent vanadium is oxidized to the pentavalent, and roasted clinker is obtained. The flue gas generated during the roasting process is used to preheat the pellets after dust removal. Step 4: Grind the roasted clinker obtained in Step 3 to a particle size of less than 0.09 mm, and then perform two water leaching processes. After water leaching, solid and liquid separation is performed to obtain water leaching residue and water leaching liquid. Step 5: Extract the aqueous extract obtained in Step 4 with organic phase A, then back-extract and recrystallize to obtain sodium vanadate. Organic phase A and back-extraction solution are recycled. The extracted aqueous extract is used to absorb and purify the flue gas exhaust gas from Step 1 and Step 3. Step Six: Dissolve the sodium vanadate obtained in Step Five in 50°C hot water, controlling the sodium vanadate solution concentration to 1~1.5 mol / L. Add 3 mol / L sulfuric acid to adjust the pH of the solution to 5.5, then continue heating to 85°C. Add a certain proportion of melamine, stir for 5 min, add 3 mol / L sulfuric acid to adjust the pH of the solution to 2, and keep warm for 40 min. During all reactions, maintain the stirring speed at 400 r / min. Filter to obtain the supernatant, wash the vanadium-containing precipitate with distilled water to obtain a vanadium-containing filter cake. After drying, calcine the vanadium-containing filter cake at 550°C for 120 min to obtain vanadium pentoxide product; wherein, the molar ratio of melamine to sodium vanadate is 1:4~1:

3. The composite additive is composed of sodium carbonate, sodium sulfate, converter steel slag powder, and manganese dioxide. The sodium carbonate content is 50-60 wt%, the sodium sulfate content is 20-30 wt%, the converter steel slag powder content is 10-25 wt%, and the manganese dioxide content is 10-25 wt%.

2. The vanadium extraction process by roasting and leaching composite salts from coal as described in claim 1, characterized in that, The conditions for water immersion in step four are: immersion temperature 85 ℃, immersion time 30 ~ 60 min, liquid-to-solid ratio 3 ~ 4 L / kg, and stirring speed 200 r / min.

3. The vanadium extraction process by roasting and leaching composite salts from coal as described in claim 1, characterized in that, In step five, the organic phase A to be extracted is prepared by mixing dodecyltrimethylammonium chloride, n-hexanol, and sulfonated kerosene in a volume ratio of 3:1:

2.

4. The vanadium extraction process by roasting and leaching composite salts from coal as described in claim 3, characterized in that, Step five involves extraction, back-extraction, and recrystallization, which includes the following steps: The aqueous extract was extracted twice with organic phase A, and then back-extracted with 2 mol / L sodium carbonate solution to obtain a back-extract. Sodium vanadate crystals were obtained by cooling the back-extract to 5 °C.

5. The vanadium extraction process for shale coal composite salt roasting-leaching as described in claim 1, characterized in that, The V2O5 content in the vanadium-bearing coal ore is greater than 0.8 wt%.

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