Comprehensive dealkalization method for vanadium extraction waste slag

Abstract

The invention discloses a comprehensive dealkalization method for vanadium extraction waste slag, which comprises the following steps: mixing the vanadium extraction waste slag with a calcium additive, a carbonaceous reducing agent and sodium nitrite for pelletizing, decomposing a sodium-containing solid solution in the vanadium extraction waste slag by adopting a roasting process, and leaching a sodium-containing phase in the waste slag by adopting a hydrothermal leaching process, thereby achieving the purpose of dealkalization. And drying the leaching residues to obtain a sodium-removed iron-containing material, recycling the sodium-removed iron-containing material for an iron-making process, and performing multi-effect evaporation on the leaching solution to form a sodium-containing product which can be directly sold. The process equipment is simple, operation is easy and convenient, recycling of the vanadium extraction waste slag in iron and steel enterprises can be achieved, meanwhile, the process is high in energy utilization rate, little in environmental pollution and low in operation and maintenance cost, large-scale recycling of the vanadium extraction waste slag can be achieved, and good economic benefits and social benefits are achieved.

Description

Technical Field

[0001] The present application relates to the field of comprehensive utilization of solid wastes, and in particular to a comprehensive dealkalization method for vanadium-extracting waste slag. Background Art

[0002] Sodium roasting is the main process for vanadium production. The vanadium slag obtained by sodium roasting contains a large amount of alkali metals and cannot be directly used for ironmaking. At present, the amount of vanadium slag produced by the steel industry is increasing year by year. Vanadium slag contains valuable elements such as Fe, V, Ti, Mn, and Cr, among which V2O5 is 1%~3%, Fe2O3 is 30%~40%, and Cr2O3 is 3~6%, which are all scarce strategic metal resources in the country. However, due to the high content of harmful elements such as alkali metals and the complex mineral structure, there is no economic, environmentally friendly and effective treatment method so far. In addition to existing in a free state, most of these alkali metals exist in a complex silicate structure, making it difficult to remove alkali metals from the slag; in addition, the vanadium slag contains high-priced vanadium and chromium, which are potentially harmful to the environment, making it difficult to recycle the vanadium slag. At present, most of the vanadium slag is stored in the open air, which not only occupies the site, but also the high-priced vanadium and high-priced chromium in it will pollute the environmental water, which is extremely harmful to human health and has prominent environmental problems. Therefore, it is urgent to solve the problem of comprehensive recycling of vanadium extraction waste slag, extract the valuable elements therein, reduce the environmental burden, and realize the comprehensive recycling of resources.

[0003] Currently, many experimental studies have been conducted on the comprehensive recycling of vanadium slag in the published patents and literature, including pyrometallurgy, hydrometallurgy and direct utilization. Pyrometallurgy can realize the recycling of some valuable elements in vanadium slag, but it has high energy consumption and large pollution; the hydrometallurgy process mainly includes direct acid leaching, oxygen pressure acid leaching and multi-combination acid leaching. Although the process is simple and the energy consumption is low, the acid consumption is large, the process is complex and the investment cost is high; the direct utilization method is mainly used to make specific functional materials such as vanadium titanium black porcelain, but the amount is small and the valuable elements are not utilized, resulting in a waste of resources.

[0004] Patent CN101838743B discloses a "method for recovering iron, vanadium, chromium and gallium from vanadium extraction tailings". The patent mixes the vanadium extraction tailings with a reducing agent, calcium oxide and a binder to form pellets, first directly reduces them to form metallized pellets, and then separates them through electric furnace smelting to obtain vanadium-chromium-gallium pig iron. This method requires two high-temperature treatments, has high requirements for equipment, and requires a large investment. It also has high energy consumption and serious pollution. A large amount of tailings is still produced after treatment, and the vanadium extraction tailings cannot be completely recycled. Moreover, this method does not involve dealkalization.

[0005] Patent CN105018734B discloses "a method for the simultaneous separation of iron, vanadium and manganese in vanadium extraction tailings". This patent converts trivalent vanadium into pentavalent soluble vanadate by adding sodium salt (one or more of sodium chloride, sodium carbonate, sodium hydroxide and sodium sulfate), and then allows vanadium to enter the solution through grinding and leaching. The leached slag is subjected to magnetic separation to obtain iron concentrate and manganese-rich tailings. The vanadium-containing solution is subjected to vanadium precipitation, separation and calcination to obtain vanadium oxide. However, this method adds sodium salt in order to convert low-valent vanadium into high-valent soluble vanadium, thereby achieving vanadium separation. This method does not involve dealkalization, and the final problem of manganese-rich tailings treatment still needs to be solved.

[0006] Patent CN115354156B discloses "a method for removing alkali metals from vanadium tailings by calcination roasting-leaching". The method comprises the following steps: mixing vanadium tailings with additives (one or more of lime, slaked lime, quicklime), a binder and water to form granules, and then oxidative roasting to volatilize free simple alkali metal oxides into flue gas. The calcifying agent can transform the complex solid solution containing alkali metals into a calcium-containing solid solution and a simple sodium-containing silicate structure. The simple sodium-containing silicate structure is removed by leaching, thereby achieving the purpose of dealkalization. The method has a high processing temperature and high energy consumption. The sodium-containing flue gas and volatiles formed during the roasting process are easily solidified and ringed in the roasting equipment, affecting the normal operation of the roasting process.

[0007] Patent CN117187577A discloses "a method for extracting vanadium from sodium-containing vanadium tailings and removing sodium from them and recycling them". This patent uses titanium dioxide waste acid and sodium-containing vanadium tailings for mixed ball milling for leaching treatment, and obtains iron-rich material, gypsum and mineral processing water through flotation separation, filtration and dehydration. The mineral processing water is enriched and extracted with sodium, vanadium and magnesium through multiple cycles. This method uses waste acid and vanadium tailings for mixed ball milling, which is easy to cause acid corrosion to the ball milling equipment, reduce the service life of the ball milling equipment, and increase operating costs. During the treatment process, valuable metals in the vanadium tailings will be leached in large quantities, resulting in a large amount of enrichment of metal elements in the leachate, making the treatment of the leachate a difficult problem.

[0008] In addition to the above patents, patent CN109182734A proposes "a method for removing sodium from tailings of vanadium-titanium magnetite sodium roasting and vanadium extraction by dilute acid heap leaching", patent CN117230306B proposes "a method and system for treating vanadium extraction waste slag by side-blowing furnace melting method", patent CN116654981A proposes "a method for calcification and dealkalization of sodium-based vanadium extraction tailings, vanadium extraction and preparation of high-purity barium vanadate", patent CN115305351B proposes "a method for strengthening the reduction and volatilization of vanadium extraction tailings to remove alkali metals", patent CN115216635B proposes "a method for strengthening the calcification roasting-leaching of vanadium extraction tailings to remove alkali metals", and patent CN115261608B proposes "a method and system for improving the strength of tailings pellets and strengthening reduction and dealkalization". Although the above patents have their own characteristics, they all have shortcomings. Most of them have problems such as complex procedures, high energy consumption, high operating costs, and inability to achieve industrial application.

[0009] If the alkali metals in the waste slag can be effectively removed, the process can be simplified, and the operation and maintenance costs can be reduced, a large amount of vanadium extraction waste slag can be recycled for iron ore blending. Therefore, it is still necessary to propose a new treatment process for the dealkalization of vanadium extraction waste slag in order to simplify the operation, reduce energy consumption and costs, and realize industrial application. Summary of the invention

[0010] The purpose of the present invention is to solve the problems that the current vanadium extraction waste slag cannot be used on a large scale, the investment and operation cost is high, the energy consumption is large, the equipment investment is high, and the environmental pollution is serious. The method can realize the efficient dealkalization of the vanadium extraction waste slag, and can recycle the valuable metals in the vanadium extraction waste slag, so that the vanadium extraction waste slag can be recycled within the factory area without being dumped or sold at a low price, thereby reducing environmental pollution and social burden. At the same time, the equipment requirements are low, the operation is simple, and the vanadium extraction waste slag generated by the enterprise can be processed on a large scale.

[0011] In order to achieve the above object, the present invention provides a comprehensive dealkalization method for vanadium extraction waste slag, which comprises the following steps: (1) The vanadium extraction waste slag, calcifying agent, carbonaceous reducing agent and sodium nitrite are fully mixed in a weight ratio of 10: 0.2-0.5: 0.2-1.5: 0.3-1.5 and then pelletized, wherein the calcifying agent is lime or limestone, and the carbonaceous reducing agent is coke powder, lignite or semi-coke; (2) calcining and decomposing the pellets prepared in step (1); the calcination temperature is set to 700-900°C, and the calcination time is 0.5-4 h; The main reactions that may occur during the roasting process are: 4NaNO2=2Na2O+4NO(g)+O2(g) (1) 2NaFe(SiO3)2+3Na2O=Fe2O3+4Na2SiO3 (2) 2C+O2(g)=2CO(g) (3) Sodium nitrite will decompose to form sodium oxide during the roasting process. Sodium oxide can decompose complex silicates into simple silicates at a relatively low temperature, thereby converting complex alkali metal silicates in vanadium extraction waste into simple and easily soluble alkali metal silicates during the roasting process, which is convenient for subsequent dissolution and leaching. The carbonaceous reducing agent can form a local reducing atmosphere inside the pellets, reduce the oxidation of vanadium-containing minerals and other phases, thereby reducing the loss in the subsequent leaching process, allowing the vanadium-containing minerals to return to the ironmaking process with the leached slag, reducing the loss of vanadium in the waste slag, and thus improving the recovery rate of vanadium; (3) crushing the material after roasting and decomposition in step (2); (4) subjecting the crushed material in step (3) to hydrothermal leaching, and obtaining leaching residue and leaching liquid by solid-liquid separation; the weight ratio of the crushed material to water is 1:4-10; the hydrothermal leaching temperature is 60-90°C, and the leaching time is 10-60 min; (5) The leaching liquid after the solid-liquid separation in step (4) is subjected to multi-effect evaporation to obtain a sodium-containing product, and the leaching residue after the solid-liquid separation in step (4) is washed and dried to obtain a sodium-free iron-containing material. The iron-containing material can be returned to the ironmaking process for continued circulation, and the sodium-containing product can be directly exported.

[0012] Specifically, the vanadium extraction waste slag, calcifying agent, carbonaceous reducing agent and sodium nitrite are mixed in a weight ratio of 10:0.2:1.0:0.5.

[0013] The comprehensive dealkalization method for vanadium extraction waste slag includes one or more of the following (1)-(6): (1) The vanadium extraction waste slag is the residue discharged after the vanadium slag is subjected to sodium roasting to extract vanadium; (2) In step (1), pelletizing is performed on a disc pelletizing machine; (3) The pelletizing particle size range is 6 to 15 mm; (4) The heat generated during the roasting process in step (2) is recovered through a waste heat boiler to generate hot water and hot steam; (5) In step (3), the crushing is carried out on a closed-circuit crushing device; (6) In step (3), the crushed particle size is 0.2-0.4 mm.

[0014] More specifically, the chemical composition of the vanadium extraction slag contains 25-45% TFe, 7-10% MnO, 7-10% TiO2, 7-10% Cr2O3, 8-15% SiO2, 1.5-2% V2O5, and 4-6% Na2O.

[0015] The hot water and hot steam used in the hydrothermal leaching process of step (4) are provided by the waste heat boiler in step (2), and the hydrothermal leaching process no longer consumes additional energy.

[0016] The heat required for the multiple-effect evaporation process in step (5) comes from the hot steam supplied by the waste heat boiler in step (2).

[0017] The steam generated by the multi-effect evaporation in step (5) is condensed and refluxed to the waste heat boiler in step (2), and the entire process is realized in a closed loop using water.

[0018] The beneficial effects of the present invention include: The invention provides a comprehensive dealkalization method for vanadium extraction waste slag. Sodium nitrite is used as an additive. Sodium nitrite decomposes at high temperature to produce Na2O, which can decompose the complex silicate structure in the vanadium extraction waste slag into sodium silicate with a simple structure. Then, the sodium silicate can be leached out through water leaching treatment, thereby realizing the removal of alkali in the vanadium extraction waste slag. Meanwhile, in the invention, a carbonaceous reducing agent is added to inhibit the oxidation of elements such as vanadium, thereby reducing the leaching of the valuable element vanadium during the water leaching process. The process method provided by the invention adopts simple equipment and process, can achieve efficient removal of alkali metals at lower roasting and leaching temperatures, has less equipment investment, and has lower operation and maintenance costs. Meanwhile, water circulation can be realized inside the process, thereby reducing the waste of water resources, reducing energy consumption by recovering heat in the roasting process, saving costs, and improving economic benefits. According to the invention, the iron-containing materials obtained after treating the vanadium extraction waste slag can be fully used in the ironmaking process, thereby realizing the circulation of the vanadium extraction waste slag inside the factory, reducing the harm of the external discharge accumulation to the environment, and improving the comprehensive recycling value of the vanadium extraction waste slag. The comprehensive dealkalization method for vanadium extraction waste slag provided by the invention can be widely applied to the comprehensive recycling process of vanadium extraction waste slag, thus reducing the environmental burden on enterprises and having good economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention provides a process flow chart of the comprehensive dealkalization method for vanadium extraction waste slag. DETAILED DESCRIPTION

[0020] The present invention is further illustrated and described below in conjunction with embodiments, but the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the present invention and embodiments, all other inventions and embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0022] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0023] Example 1: A comprehensive dealkalization method for vanadium extraction waste slag The vanadium extraction waste slag used in this embodiment is the slag discharged after the vanadium slag is subjected to sodium roasting and vanadium extraction, and its chemical composition is 37.22% TFe, 9.46% MnO, 7.74% TiO2, 7.89% Cr2O3, 8.47% SiO2, V2O51.58%, 5.35% Na2O, and its main components are iron oxide, nepheline, ilmenite, etc., and it also contains a large amount of metal elements such as manganese, chromium, vanadium, etc.; in this embodiment, coke powder (with a fixed carbon content of >85%) is selected as the reducing agent.

[0024] like Figure 1 As shown, the specific implementation steps are as follows: (1) The vanadium extraction waste slag, calcium oxide, coke powder and sodium nitrite are fully mixed in a mass ratio of 10:0.2:1.0:0.5 and then pelletized on a disc pelletizer. The pellet size ranges from 7 to 10 mm. (2) The pellets prepared in step (1) are conveyed into a tunnel furnace by a belt, the temperature in the tunnel furnace is set to 750°C, and the roasting time is 2 hours; the heat generated during the roasting process is recovered by a waste heat boiler to generate hot water and hot steam; (3) crushing the material after roasting and decomposition in step (2) to a particle size of 0.2 mm on a closed-circuit crushing device; (4) conveying the crushed material in step (3) into a stirring tank for hydrothermal leaching at a weight ratio of crushed material to water of 1:6, the water leaching temperature is 60-70°C, the stirring time is 30 minutes, the slurry after stirring is discharged from the slurry discharge port, and the leaching residue and the leaching liquid are obtained by solid-liquid separation; the hot water and hot steam used in the hydrothermal leaching process are provided by the waste heat boiler in step (2); (5) The leaching liquid after the solid-liquid separation in step (4) is subjected to multi-effect evaporation to obtain a sodium-containing material, and the leaching residue after the solid-liquid separation in step (4) is washed and dried to obtain a de-sodiumated iron-containing material. The heat required for the multi-effect evaporation process comes from the hot steam supplied by the waste heat boiler in step (2), and the steam generated by the multi-effect evaporation is refluxed to the waste heat boiler in step (2) through condensation.

[0025] The sodium removal rate of the iron-containing material after treatment by this process reaches more than 90%, and can be directly returned to the iron-making process for utilization.

[0026] Example 2: A comprehensive dealkalization method for vanadium extraction waste slag The vanadium extraction waste slag used in this embodiment is the slag discharged after the vanadium slag is subjected to sodium roasting and vanadium extraction, and its chemical composition is 32.78% TFe, 10.23% MnO, 8.56% TiO2, 7.45% Cr2O3, 9.62% SiO2, 1.43% V2O5, 4.48% Na2O, and its main components are iron oxide, nepheline, ilmenite, etc., and it also contains a large amount of metal elements such as manganese, chromium, and vanadium; in this embodiment, blue charcoal (with a fixed carbon content of> 80%) is selected as a reducing agent; the specific implementation steps are as follows: (1) The vanadium extraction waste slag, calcium carbonate, semi-coke and sodium nitrite are fully mixed in a mass ratio of 10:0.3:0.3:0.7 and then pelletized on a disc pelletizer. The pellet size ranges from 8 to 12 mm. (2) The pellets prepared in step (1) are conveyed into a tunnel furnace by a belt, the temperature in the tunnel furnace is set to 900° C., and the roasting time is 1 hour; the heat generated during the roasting process is recovered by a waste heat boiler to generate hot water and hot steam; (3) crushing the material after roasting and decomposition in step (2) to a particle size of 0.4 mm on a closed-circuit crushing device; (4) The crushed material in step (3) is transferred to a stirring tank for hydrothermal leaching at a weight ratio of crushed material to water of 1:8, the water leaching temperature is 70-80°C, the stirring time is 20 min, and the stirred slurry is separated into leaching residue and leaching liquid by solid-liquid separation; the hot water and hot steam used in the hydrothermal leaching process are provided by the waste heat boiler in step (2); (5) The leaching liquid after the solid-liquid separation in step (4) is subjected to multi-effect evaporation to obtain a sodium-containing material, and the leaching residue after the solid-liquid separation in step (4) is washed and dried to obtain a de-sodiumated iron-containing material. The heat required for the multi-effect evaporation process comes from the hot steam supplied by the waste heat boiler in step (2), and the steam generated by the multi-effect evaporation is refluxed to the waste heat boiler in step (2) through condensation.

[0027] The sodium removal rate of the iron-containing material after treatment by this process reaches more than 85%, and can be directly returned to the iron-making process for utilization; the sodium-containing product after multi-effect evaporation is mainly sodium silicate.

Claims

1. A comprehensive dealkalization method for vanadium extraction waste slag, characterized in that: The method comprises the following steps: (1) The vanadium extraction waste slag, calcifying agent, carbonaceous reducing agent and sodium nitrite are fully mixed in a weight ratio of 10: 0.2-0.5: 0.2-1.5: 0.3-1.5 and then pelletized, wherein the calcifying agent is lime or limestone, and the carbonaceous reducing agent is coke powder, lignite or semi-coke; (2) calcining and decomposing the pellets prepared in step (1); the calcination temperature is set to 700-900°C, and the calcination time is 0.5-4 h; (3) crushing the material after roasting and decomposition in step (2); (4) subjecting the crushed material in step (3) to hydrothermal leaching, and obtaining leaching residue and leaching liquid by solid-liquid separation; the weight ratio of the crushed material to water is 1:4-10; the hydrothermal leaching temperature is 60-90°C, and the leaching time is 10-60 min; (5) The leaching liquid after the solid-liquid separation in step (4) is subjected to multi-effect evaporation to obtain a sodium-containing product, and the leaching residue after the solid-liquid separation in step (4) is washed and dried to obtain a sodium-free iron-containing material.

2. The comprehensive dealkalization method for vanadium extraction waste slag according to claim 1, characterized in that: The vanadium extraction waste slag, calcifying agent, carbonaceous reducing agent and sodium nitrite are mixed at a weight ratio of 10:0.2:1.0:0.

5.

3. The comprehensive dealkalization method for vanadium extraction waste slag according to claim 1 or 2, characterized in that: Includes one or more of the following (1)-(6): (1) The vanadium extraction waste slag is the residue discharged after the vanadium slag is subjected to sodium roasting to extract vanadium; (2) In step (1), pelletizing is performed on a disc pelletizing machine; (3) The pelletizing particle size range is 6 to 15 mm; (4) The heat generated during the roasting process in step (2) is recovered through a waste heat boiler to generate hot water and hot steam; (5) In step (3), the crushing is carried out on a closed-circuit crushing device; (6) In step (3), the crushed particle size is 0.2-0.4 mm.

4. The comprehensive dealkalization method for vanadium extraction waste slag according to claim 3, characterized in that: The chemical composition of the vanadium extraction waste slag contains 25-45% TFe, 7-10% MnO, 7-10% TiO2, 7-10% Cr2O3, 8-15% SiO2, 1.5-2% V2O5, and 4-6% Na2O.

5. The comprehensive dealkalization method for vanadium extraction waste slag according to claim 3, characterized in that: The hot water and hot steam used in the hydrothermal leaching process of step (4) are provided by the waste heat boiler in step (2), and the hydrothermal leaching process no longer consumes additional energy.

6. The comprehensive dealkalization method for vanadium extraction waste slag according to claim 3, characterized in that: The heat required for the multiple-effect evaporation process in step (5) comes from the hot steam supplied by the waste heat boiler in step (2).

7. The comprehensive dealkalization method for vanadium extraction waste slag according to claim 6, characterized in that: The steam generated by the multi-effect evaporation in step (5) is refluxed to the waste heat boiler in step (2) through condensation.

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