Method for separating vanadium and molybdenum from waste SCR (Selective Catalytic Reduction) denitration catalyst alkaline leaching solution

Abstract

The invention discloses a method for separating vanadium and molybdenum from waste SCR denitration catalyst alkaline leaching liquid, and belongs to the technical field of vanadium and molybdenum separation.The method comprises the steps that a waste SCR denitration catalyst and alkaline liquor are mixed, wet-ground and leached, and the alkaline leaching liquid and high-titanium powder are obtained through filtering; adding an impurity removing agent into the alkaline leaching solution to remove impurities, and filtering to obtain a purified solution; calcium oxide is added into the purified liquid for calcification and vanadium precipitation, and calcium vanadate and a molybdenum-rich solution are obtained through filtering; the molybdenum-rich solution is subjected to evaporation concentration, cooling crystallization and filtering, sodium molybdate and recycled alkali liquor are obtained, the recycled alkali liquor is circulated to the leaching procedure, the technology combining wet grinding leaching with chemical precipitation and physical crystallization is adopted, efficient separation is achieved through the reaction characteristics of vanadium, molybdenum and calcium oxide, the process is simple, and operation is convenient and fast. The method is high in vanadium and molybdenum recovery rate, good in product purity, free of wastewater discharge in medium circulation, low in cost, environmentally friendly and suitable for industrial production, and an effective way is provided for resource utilization of the waste SCR catalyst.

Description

Technical Field

[0001] This invention relates to the field of vanadium-molybdenum separation technology, specifically a method for separating vanadium and molybdenum from the alkaline leaching solution of spent SCR denitrification catalyst. Background Technology

[0002] With the steady advancement of dual-carbon goals and policy guidance, the sustainable development of valuable resources, such as the regeneration and recycling of spent SCR catalysts, has become a research focus. For SCR catalysts deactivated due to dust blockage and alkali metal poisoning, purging and low-concentration acid leaching can restore their catalytic activity. However, SCR catalysts whose structure is damaged and cannot be regenerated are rich in valuable elements such as Ti, W, V, and Mo. To reduce resource waste, appropriate methods are needed for their effective recovery. Currently, alkaline leaching is widely used for the separation and recovery of TiO2 support and active components such as V and W from spent SCR catalysts. However, W in the alkaline leaching solution has similar properties to V and Mo, making separation difficult.

[0003] The recovery of vanadium (W), vanadium (V), and molybdenum (Mo) from spent SCR catalysts has significant economic and environmental value. However, due to their similar forms in the leachate, traditional separation methods are often inefficient or costly. Exploring new, more efficient, environmentally friendly, and economical vanadium-molybdenum separation technologies to effectively separate and recover vanadium and molybdenum from spent SCR catalysts, thereby improving production efficiency and product quality while reducing costs and environmental impact, and achieving resource recycling, is of significant resource and environmental importance.

[0004] CN104831075A discloses a method for separating and purifying vanadium and molybdenum from waste vanadium-molybdenum SCR catalysts. The method involves pretreating the catalyst to obtain titanium slag and a vanadium-molybdenum solution; extracting and separating the vanadium-molybdenum solution, then acidifying and further treating the resulting molybdenum-rich raffinate to obtain molybdic acid; back-extracting the obtained vanadium-rich organic phase, followed by a two-stage extraction process to extract vanadium, and then back-extracting again to obtain a vanadium-rich solution. This vanadium-rich solution is then further treated to produce vanadium pentoxide. While this method can separate, recover, and purify vanadium and molybdenum from industrially waste vanadium-molybdenum SCR catalysts, it requires multiple extraction and back-extraction processes, resulting in a long overall process flow, high equipment requirements, high energy consumption, and the generation of large amounts of wastewater that require treatment, leading to high environmental costs.

[0005] CN114574699A describes a method for preparing ammonium metavanadate and ammonium molybdate from a vanadium-molybdenum-containing solution. This method achieves stepwise separation of vanadium and molybdenum in the solution by adding a calcium source in stages, and similarly uses a calcium source to separate molybdenum from the alkaline solution, thus obtaining ammonium metavanadate and ammonium molybdate products. While this method can prepare ammonium metavanadate and ammonium molybdate from a vanadium-molybdenum-containing solution, the stepwise separation using calcium sources only produces calcium vanadate and calcium molybdate. Stepwise addition of ammonium sources is still required to prepare ammonium metavanadate and ammonium molybdate, and a large amount of ammonia nitrogen wastewater is generated that needs treatment. The entire process requires strict operational control, and the separation of vanadium and molybdenum is not complete.

[0006] Although these methods have made some progress in laboratory-scale research in recent years, they still face some challenges in practical industrial applications, including improving separation efficiency, reducing costs, reducing environmental pollution, and the feasibility of large-scale application. Summary of the Invention

[0007] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0008] Therefore, the purpose of this invention is to provide a method for separating vanadium and molybdenum from the alkaline leaching solution of waste SCR denitrification catalyst. This method has a simple and easy-to-operate process, high resource utilization rate, good separation effect of vanadium and molybdenum, high recovery rate of vanadium and molybdenum, and high purity of the obtained calcium vanadate and sodium molybdate. The entire separation process uses recycled media with no wastewater discharge, which is in line with the concept of green environmental protection.

[0009] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution: A method for separating vanadium and molybdenum from the alkaline leaching solution of spent SCR denitrification catalyst, comprising the following steps: S1. The waste SCR denitrification catalyst is mixed with alkaline solution and then wet-milled and leached. After the reaction is completed, the alkaline leaching solution and high titanium powder are obtained by solid-liquid separation. S2. Add a purification agent to the alkaline leaching solution obtained in step S1 to carry out a purification reaction. After the reaction is completed, the purified solution and the purified mud are obtained by solid-liquid separation. S3. Add calcium oxide to the purified liquid obtained in step S2 to carry out calcification and vanadium precipitation reaction. After the reaction is completed, calcium vanadate and molybdenum-rich solution are obtained by solid-liquid separation. S4. The molybdenum-rich solution obtained in step S3 is evaporated and concentrated, then cooled and crystallized. After the reaction is completed, sodium molybdate and recycled alkali solution are obtained by solid-liquid separation. The recycled alkali solution is returned to the wet milling leaching process in step S1 for recycling.

[0010] As a preferred embodiment of the method for separating vanadium and molybdenum from the alkaline leaching solution of waste SCR denitrification catalyst according to the present invention, in step S1, the waste SCR denitrification catalyst is derived from the flue gas denitrification process of thermal power plants, cement plants or glass plants.

[0011] As a preferred embodiment of the method for separating vanadium and molybdenum from the alkaline leaching solution of a waste SCR denitrification catalyst according to the present invention, in step S1, the waste SCR denitrification catalyst has a TiO content of 50-90%, a V2O content of 0.5-5%, a MoO3 content of 1-10%, and a SiO2 content of 5-20%.

[0012] As a preferred embodiment of the method for separating vanadium and molybdenum from the alkaline leaching solution of a waste SCR denitrification catalyst according to the present invention, in step S1, the alkaline solution is a sodium hydroxide solution, a potassium hydroxide solution, or a mixture of both.

[0013] As a preferred embodiment of the method for separating vanadium and molybdenum from the alkaline leaching solution of waste SCR denitrification catalyst according to the present invention, in step S1, the liquid-to-solid ratio of wet milling is 3-10:1, the wet milling reaction temperature is 20-50℃, and the reaction time is 0.5-1h.

[0014] As a preferred embodiment of the method for separating vanadium and molybdenum from the alkaline leaching solution of waste SCR denitrification catalyst according to the present invention, in step S1, after the wet grinding reaction is completed, the slurry is transferred to a high-pressure reactor for high-temperature and high-pressure reaction. The gas for the high-temperature and high-pressure reaction is oxygen or compressed air, the reaction temperature is 120-180℃, the pressure is 0.4-0.8MPa, and the reaction time is 1-3h.

[0015] In a preferred embodiment of the method for separating vanadium and molybdenum from the alkaline leaching solution of waste SCR denitrification catalyst according to the present invention, in step S2, the impurity removal agent is one or more of polymagnesium sulfate, polyaluminum sulfate, and polyferric sulfate.

[0016] As a preferred embodiment of the method for separating vanadium and molybdenum from the alkaline leaching solution of waste SCR denitrification catalyst according to the present invention, in step S2, the amount of impurity removal agent added is 1-5% of the volume of the alkaline leaching solution, the impurity removal reaction temperature is 40-80℃, and the reaction time is 1-2h.

[0017] As a preferred embodiment of the method for separating vanadium and molybdenum from the alkaline leaching solution of waste SCR denitrification catalyst according to the present invention, in step S3, the amount of calcium oxide added is 1-3 times the molar amount of V2O5 in the purification solution, the calcification precipitation reaction temperature is 90-100℃, and the reaction time is 2-4h.

[0018] As a preferred embodiment of the method for separating vanadium and molybdenum from the alkaline leaching solution of waste SCR denitrification catalyst according to the present invention, in step S4, the evaporation and concentration method is forced circulation evaporation, falling film evaporation or scraped evaporation, the liquid volume at the end of evaporation is 20-40% of the purified liquid volume, the cooling and crystallization temperature is 30-50℃, and the crystallization time is 2-4h.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. The method for separating vanadium and molybdenum from the alkaline leaching solution of waste SCR denitrification catalyst provided by the present invention, compared with the acid leaching method, uses a combination of wet grinding alkaline leaching and high temperature and high pressure alkaline leaching to treat the waste SCR denitrification catalyst, which results in a higher leaching rate of vanadium and molybdenum, while less dissolution of impurity metals (such as Fe and Al), and a higher leaching rate of Si in the waste SCR denitrification catalyst, which can more effectively increase the Ti content in high titanium powder. 2. The method for separating vanadium and molybdenum from the alkaline leaching solution of waste SCR denitrification catalyst provided by the present invention has a short reaction process. It recovers vanadium and molybdenum metals from waste SCR denitrification catalyst by combining chemical leaching, chemical precipitation and physical evaporation crystallization, avoiding a large amount of energy loss caused by high-temperature roasting. At the same time, the medium in the whole process is completely recycled, which is more beneficial to environmental protection and can realize industrial production. 3. The method for separating vanadium and molybdenum from the alkaline leaching solution of waste SCR denitrification catalyst provided by the present invention utilizes the different reaction conditions of vanadium and molybdenum with calcium oxide at different alkaline concentrations, and takes advantage of the characteristic that vanadium preferentially reacts with calcium oxide over molybdenum to achieve efficient separation of vanadium and molybdenum, avoiding the need to treat a large amount of organic wastewater caused by traditional extraction and other methods. 4. The method for separating vanadium and molybdenum from the alkaline leaching solution of waste SCR denitrification catalyst provided by the present invention produces calcium vanadate, which can be directly used as a raw material for producing high-purity ammonium metavanadate. The processing method is simple and economical. The sodium molybdate prepared by evaporation, concentration and crystallization has a low content of impurity elements and can be sold directly as a product. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and detailed embodiments. 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. Wherein: Figure 1 The present invention provides a flowchart of a method for separating vanadium and molybdenum from the alkaline leaching solution of a spent SCR denitrification catalyst. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] Figure 1 The diagram shown is a flowchart of a method for separating vanadium and molybdenum from the alkaline leaching solution of a spent SCR denitrification catalyst, provided by the present invention. The following is a description of the method in conjunction with... Figure 1 Examples 1-7 and Comparative Examples 1-4 provide a detailed description of the specific steps and technical effects of the above-described method for separating vanadium and molybdenum from the alkaline leaching solution of spent SCR denitrification catalyst. Example 1

[0023] Waste SCR denitrification catalyst with a TiO2 content of 70%, V2O5 content of 2%, MoO3 content of 6%, and SiO2 content of 10% was selected as raw material. It was mixed with a 16% sodium hydroxide solution at a liquid-to-solid ratio of 5:1 and then fed into a vertical mill for wet milling at 30℃ for 0.6 hours. After wet milling, the slurry was pumped into a high-temperature, high-pressure reactor for leaching at 160℃ and 0.6 MPa for 2 hours. After leaching, solid-liquid separation was performed. High-titanium powder and leachate were obtained. 3% polymagnesium sulfate (by liquid volume) was added to the leachate for impurity removal reaction at 70℃ for 1 hour. After the impurity removal reaction, solid-liquid separation was performed to obtain impurity-removed sludge and purified liquid. Calcium oxide (1.5 times the molar amount of V2O5) was added to the purified liquid, and vanadium precipitation was carried out at 95℃ for 3 hours. After solid-liquid separation, calcium vanadate and molybdenum-rich solution were obtained. The molybdenum-rich solution was evaporated to 30% of the volume of the purified liquid. After evaporation, the liquid was cooled to 40℃ for crystallization for 4 hours. Sodium molybdate and recycled alkali solution were obtained after solid-liquid separation. Example 2

[0024] Waste SCR denitration catalyst with a TiO2 content of 60%, V2O5 content of 4%, MoO3 content of 8%, and SiO2 content of 14% was selected as raw material. It was mixed with a 14% potassium hydroxide solution at a liquid-to-solid ratio of 4:1 and then fed into a vertical mill for wet milling at 40℃ for 0.8 hours. After wet milling, the slurry was pumped into a high-temperature, high-pressure reactor for leaching at 170℃ and 0.6 MPa for 2 hours. After leaching, solid-liquid separation was performed. High-titanium powder and leachate were obtained. 3% polyaluminum sulfate (by liquid volume) was added to the leachate for impurity removal reaction at 80℃ for 1.5 hours. After the impurity removal reaction, solid-liquid separation was performed to obtain impurity-removed sludge and purified liquid. Calcium oxide (twice the molar amount of V2O5) was added to the purified liquid, and vanadium precipitation was carried out at 98℃ for 2 hours. After solid-liquid separation, calcium vanadate and molybdenum-rich solution were obtained. The molybdenum-rich solution was evaporated to 40% of the purified liquid volume. After evaporation, the solution was cooled to 50℃ for crystallization for 4 hours. Sodium molybdate and recycled alkali solution were obtained after solid-liquid separation. Example 3

[0025] Waste SCR denitrification catalyst with a TiO2 content of 80%, V2O5 content of 3.5%, MoO3 content of 7%, and SiO2 content of 12% was selected as raw material. It was mixed with a 10% sodium hydroxide solution at a liquid-to-solid ratio of 8:1 and then fed into a vertical mill for wet milling at 50℃ for 1 hour. After wet milling, the slurry was pumped into a high-temperature, high-pressure reactor for leaching at 180℃ and 0.8 MPa for 3 hours. After leaching, a solid-liquid reaction was carried out. High-titanium powder and leachate were obtained by separation. 4% polyferric sulfate (by liquid volume) was added to the leachate for impurity removal reaction at 40℃ for 1 hour. After the impurity removal reaction, solid-liquid separation yielded impurity-removed sludge and purified liquid. Calcium oxide (1 molar amount of V2O5) was added to the purified liquid, and vanadium precipitation was carried out at 90℃ for 2 hours. After solid-liquid separation, calcium vanadate and molybdenum-rich solution were obtained. The molybdenum-rich solution was evaporated to 20% of the purified liquid volume. After evaporation, the solution was cooled to 30℃ for crystallization for 2 hours. Sodium molybdate and recycled alkali solution were obtained by solid-liquid separation. Example 4

[0026] Waste SCR denitrification catalyst with a TiO2 content of 75%, V2O5 content of 2.5%, MoO3 content of 8%, and SiO2 content of 8% was selected as raw material. It was mixed with a 24% potassium hydroxide solution at a liquid-to-solid ratio of 7:1 and then fed into a vertical mill for wet milling at 30℃ for 1 hour. After wet milling, the slurry was pumped into a high-temperature, high-pressure reactor for leaching at 120℃ and 0.4 MPa for 1 hour. After leaching, solid-liquid separation was performed. High-titanium powder and leachate were obtained. 1% polyaluminum sulfate (by liquid volume) was added to the leachate for impurity removal at 40°C for 1 hour. After the impurity removal reaction, solid-liquid separation yielded impurity-removed sludge and purified liquid. Calcium oxide (3 times the molar amount of V2O5) was added to the purified liquid, and vanadium precipitation was carried out at 100°C for 4 hours. After solid-liquid separation, calcium vanadate and molybdenum-rich solution were obtained. The molybdenum-rich solution was evaporated to 40% of the purified liquid volume. After evaporation, the solution was cooled to 50°C for crystallization for 2 hours. Sodium molybdate and recycled alkali solution were obtained after solid-liquid separation. Example 5

[0027] Waste SCR denitrification catalyst with a TiO2 content of 55%, V2O5 content of 5%, MoO3 content of 10%, and SiO2 content of 15% was selected as raw material. It was mixed with a 28% sodium hydroxide solution at a liquid-to-solid ratio of 10:1 and then fed into a vertical mill for wet milling at 25℃ for 1 hour. After wet milling, the slurry was pumped into a high-temperature, high-pressure reactor for leaching at 180℃ and 0.8 MPa for 2 hours. After leaching, a solid-liquid reaction was carried out. High-titanium powder and leachate were obtained by separation. 4% polymagnesium sulfate (by liquid volume) was added to the leachate for impurity removal reaction at 80℃ for 1 hour. After the impurity removal reaction, solid-liquid separation was performed to obtain impurity-removed sludge and purified liquid. Calcium oxide (twice the molar amount of V2O5) was added to the purified liquid, and vanadium precipitation was carried out at 90℃ for 2 hours. After solid-liquid separation, calcium vanadate and molybdenum-rich solution were obtained. The molybdenum-rich solution was evaporated to 40% of the volume of the purified liquid. After evaporation, the solution was cooled to 45℃ for crystallization for 3 hours. Sodium molybdate and recycled alkali solution were obtained by solid-liquid separation. Example 6

[0028] Waste SCR denitrification catalyst with a TiO2 content of 65%, V2O5 content of 1.5%, MoO3 content of 6%, and SiO2 content of 14% was selected as raw material. It was mixed with a 20% potassium hydroxide solution at a liquid-to-solid ratio of 3:1 and then fed into a vertical mill for wet milling at 45℃ for 0.8 hours. After wet milling, the slurry was pumped into a high-temperature, high-pressure reactor for leaching at 170℃ and 0.7 MPa for 2.5 hours. After leaching, solid-liquid separation was performed. High-titanium powder and leachate were obtained. 2.5% polyaluminum sulfate (by volume) was added to the leachate for impurity removal at 70°C for 1.5 hours. After the impurity removal reaction, solid-liquid separation was performed to obtain impurity-removed sludge and purified liquid. Calcium oxide (1.6 times the molar amount of V2O5) was added to the purified liquid, and vanadium precipitation was carried out at 97°C for 3 hours. After solid-liquid separation, calcium vanadate and molybdenum-rich solution were obtained. The molybdenum-rich solution was evaporated to 35% of the volume of the purified liquid. After evaporation, the solution was cooled to 38°C for crystallization for 3 hours. Sodium molybdate and recycled alkali solution were obtained after solid-liquid separation. Example 7

[0029] Waste SCR denitration catalyst with a TiO2 content of 90%, V2O5 content of 1%, MoO3 content of 4%, and SiO2 content of 5% was selected as raw material. It was mixed with an 18% sodium hydroxide solution at a liquid-to-solid ratio of 5:1 and then fed into a vertical mill for wet milling at 35℃ for 0.8 hours. After wet milling, the slurry was pumped into a high-temperature, high-pressure reactor for leaching at 160℃ and 0.6 MPa for 2 hours. After leaching, solid-liquid separation was performed to obtain… High-titanium powder and leachate were added. 2.2% polymagnesium sulfate (by volume) was added to the leachate for impurity removal reaction at 55°C for 1 hour. After the impurity removal reaction, solid-liquid separation was performed to obtain impurity-removed sludge and purified liquid. Calcium oxide (1.5 times the molar amount of V2O5) was added to the purified liquid, and vanadium precipitation was carried out at 94°C for 2 hours. After solid-liquid separation, calcium vanadate and molybdenum-rich solution were obtained. The molybdenum-rich solution was evaporated to 40% of the volume of the purified liquid. After evaporation, the liquid was cooled to 50°C for crystallization for 3 hours. Sodium molybdate and recycled alkali solution were obtained after solid-liquid separation.

[0030] Comparative Example 1 For the comparison of leaching effects, only wet milling leaching reaction was carried out, and high-temperature and high-pressure leaching reaction was not carried out in the autoclave. The other conditions were the same as in Example 1.

[0031] Comparative Example 2 For the comparison of impurity removal effects, calcium carbonate was added for the impurity removal reaction, and the other conditions were the same as in Example 3.

[0032] Comparative Example 3 The vanadium-molybdenum separation effect was compared. No calcium oxide was added to precipitate vanadium, and only evaporation crystallization was performed. The other conditions were the same as in Example 5.

[0033] Comparative Example 4 In the comparison of vanadium-molybdenum separation effects, only calcium oxide was added to precipitate vanadium, without evaporation and crystallization, and the other conditions were the same as in Example 7.

[0034] The purity of the calcium vanadate and molybdate prepared in Examples 1-7 and Comparative Examples 1-4 was tested by atomic absorption spectrometry, and the specific test results are shown in Table 1.

[0035] V₂O₅ recovery rate = n / n₀ × 100%. n₀ is the molar amount of V₂O₅ in the leachate. n is the actual molar amount of V₂O₅ recovered from calcium vanadate.

[0036] MoO3 recovery rate = n / n0 × 100%. n0 is the molar amount of MoO3 in the leachate. n is the actual molar amount of MoO3 recovered from molybdate.

[0037] Table 1. Purity test content of vanadium-rich crystals and tungstates prepared in Examples 1-7 and Comparative Examples 1-4.

[0038]

[0039] After testing, Examples 1-7 demonstrated that by using waste denitrification catalyst for alkaline leaching, and then removing impurities from the leachate, calcium oxide was first added for calcification to precipitate vanadium and recover V2O5, followed by evaporation and crystallization to recover MoO3. This achieved efficient leaching, purification, and collection of vanadium and molybdenum. The resulting calcium vanadate and molybdate have the advantages of high yield, high output value, and high purity, making the process for selling the products to downstream processing plants simpler.

[0040] In Comparative Example 1, the spent denitrification catalyst was only subjected to wet grinding and alkaline leaching, without high-temperature and high-pressure leaching in an autoclave. This resulted in only the vanadium and molybdenum, which are easily leached from the surface of the spent denitrification catalyst, reacting with the alkaline solution. The vanadium and molybdenum, which have lower activity and more stable structures in the remaining catalysts, could not react and leach out of the solution because the reaction conditions were not met. Therefore, the recovery rates of vanadium and molybdenum were relatively low.

[0041] In Comparative Example 2, after changing the impurity removal agent, the leachate contained a large amount of silicates and arsenates. If these impurity salts were not removed, they would crystallize and precipitate together with vanadium and molybdenum during the separation process at the downstream end. A large amount of silicates would also seriously affect the solid-liquid separation effect. Calcium carbonate has a relatively stable structure and is difficult to react with silicates, so the impurity removal effect cannot be achieved. Therefore, it is very necessary to use a suitable impurity removal agent for impurity removal.

[0042] In Comparative Example 3, only calcium oxide was added to precipitate vanadium without evaporation and concentration. Vanadium in the purified solution could only be precipitated out in the form of calcium vanadate. However, sodium molybdate in the purified solution has a high solubility and does not react with calcium oxide under low alkaline conditions, thus failing to achieve the purpose of molybdenum recovery.

[0043] In the comparative examples, only evaporation and crystallization were performed without the addition of calcium oxide to precipitate vanadium. Since vanadium and molybdenum have similar structures, their solubility in the same alkaline solution is basically the same, and the separation of vanadium and molybdenum cannot be achieved by simple evaporation, concentration and enrichment.

[0044] Although the present invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, as long as there is no structural conflict, the features in the disclosed embodiments can be combined with each other in any manner. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for separating vanadium and molybdenum from the alkaline leaching solution of spent SCR denitrification catalyst, characterized in that, The steps are as follows: S1. The waste SCR denitrification catalyst is mixed with alkaline solution and then wet-milled and leached. After the reaction is completed, the alkaline leaching solution and high titanium powder are obtained by solid-liquid separation. S2. Add a purification agent to the alkaline leaching solution obtained in step S1 to carry out a purification reaction. After the reaction is completed, the purified solution and the purified mud are obtained by solid-liquid separation. S3. Add calcium oxide to the purified liquid obtained in step S2 to carry out calcification and vanadium precipitation reaction. After the reaction is completed, calcium vanadate and molybdenum-rich solution are obtained by solid-liquid separation. S4. The molybdenum-rich solution obtained in step S3 is evaporated and concentrated, then cooled and crystallized. After the reaction is completed, sodium molybdate and recycled alkali solution are obtained by solid-liquid separation. The recycled alkali solution is returned to the wet milling leaching process in step S1 for recycling.

2. The method for separating vanadium and molybdenum from the alkaline leaching solution of a spent SCR denitrification catalyst according to claim 1, characterized in that, In step S1, the waste SCR denitrification catalyst comes from the flue gas denitrification process of thermal power plants, cement plants or glass plants.

3. The method for separating vanadium and molybdenum from the alkaline leaching solution of a spent SCR denitrification catalyst according to claim 1, characterized in that, In step S1, the waste SCR denitrification catalyst contains 50-90% TiO, 0.5-5% V2O, 1-10% MoO3, and 5-20% SiO2.

4. The method for separating vanadium and molybdenum from the alkaline leaching solution of a spent SCR denitrification catalyst according to claim 1, characterized in that, In step S1, the alkaline solution is a sodium hydroxide solution, a potassium hydroxide solution, or a mixture of both.

5. The method for separating vanadium and molybdenum from the alkaline leaching solution of a spent SCR denitrification catalyst according to claim 1, characterized in that, In step S1, the liquid-to-solid ratio of wet milling is 3-10:1, the wet milling reaction temperature is 20-50℃, and the reaction time is 0.5-1h.

6. The method for separating vanadium and molybdenum from the alkaline leaching solution of a spent SCR denitrification catalyst according to claim 1, characterized in that, In step S1, after the wet grinding reaction is completed, the slurry is transferred to a high-pressure reactor for high-temperature and high-pressure reaction. The gas used in the high-temperature and high-pressure reaction is oxygen or compressed air. The reaction temperature is 120-180℃, the pressure is 0.4-0.8MPa, and the reaction time is 1-3h.

7. The method for separating vanadium and molybdenum from the alkaline leaching solution of a spent SCR denitrification catalyst according to claim 1, characterized in that, In step S2, the impurity removal agent is one or more of polymagnesium sulfate, polyaluminum sulfate, and polyferric sulfate.

8. The method for separating vanadium and molybdenum from the alkaline leaching solution of a spent SCR denitrification catalyst according to claim 1, characterized in that, In step S2, the amount of impurity removal agent added is 1-5% of the volume of the alkaline leaching solution, the impurity removal reaction temperature is 40-80℃, and the reaction time is 1-2h.

9. The method for separating vanadium and molybdenum from the alkaline leaching solution of a spent SCR denitrification catalyst according to claim 1, characterized in that, In step S3, the amount of calcium oxide added is 1-3 times the molar amount of V2O5 in the purification solution, the calcification and vanadium precipitation reaction temperature is 90-100℃, and the reaction time is 2-4h.

10. The method for separating vanadium and molybdenum from the alkaline leaching solution of a spent SCR denitrification catalyst according to claim 1, characterized in that, In step S4, the evaporation and concentration methods are forced circulation evaporation, falling film evaporation, or scraped evaporation. The liquid volume at the end of the evaporation is 20-40% of the purified liquid volume. The cooling and crystallization temperature is 30-50℃, and the crystallization time is 2-4 hours.

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