A method for recycling waste SCR denitration catalyst to prepare titanium tungsten powder and vanadium product

Abstract

The present invention relates to a method for recovering and preparing titanium-tungsten powder and vanadium products from waste SCR denitration catalysts, comprising activating pretreated waste SCR denitration catalyst powder and then subjecting it to high-pressure leaching with a mixed alkali solution. After the leaching is completed, solid-liquid separation is performed to obtain a leaching residue mainly composed of titanium dioxide and tungsten trioxide and a leachate containing vanadium elements; the leaching residue is further pickled, washed with water, and dried to obtain the reused titanium-tungsten powder; the leachate is pH-adjusted to precipitate vanadium, filtered, and dried to obtain the vanadium product. The main component of the mixed alkali solution used in the present invention is ammonia water, to which a low content of sodium ions is added, which inhibits the reaction between the waste catalyst and the alkali solution and reduces the amount of acid generated during subsequent treatment. By mixing the produced leachate with the waste acid solution in the subsequent process, adjusting the pH to precipitate and recover the vanadium component, the generation of pollutants in the waste SCR denitration catalyst recovery process is reduced, thereby achieving low-cost and green recovery of waste SCR denitration catalyst resources.

Description

Technical Field

[0001] The present invention relates to the field of waste SCR denitration catalyst recovery, and in particular to a method for recovering waste SCR denitration catalyst to prepare titanium tungsten powder and vanadium products, belonging to the field of flue gas denitration and material recycling. Background Art

[0002] Selective Catalytic Reduction (SCR) technology is used to achieve NO x An effective way to achieve ultra-low emissions, where the catalyst is the core component of SCR technology and can reduce NO x The activation energy of decomposition is to use NH3 as reducing agent to reduce NO x It is reduced to N2, which has the advantages of simple system, reliable operation and high denitrification efficiency. The service life of denitrification catalyst is 2-3 years. During use, the complex composition of flue gas will cause various catalysts to be deactivated and scrapped.

[0003] Waste SCR denitrification catalysts, listed as hazardous waste in the National Hazardous Waste Catalog, contain key elements such as vanadium, tungsten, and titanium, which are strategic national metal resources and possess extremely high recycling value. In recent years, the government has encouraged the safe disposal of waste SCR denitrification catalysts, enabling the reuse of these strategic metal resources, resulting in both economic benefits and reduced environmental pollution.

[0004] Patent CN111270076A discloses a method for recovering titanium-tungsten powder from waste SCR denitration catalysts, which includes steps such as dust and impurity removal, crushing, ball milling, alkali leaching, filtration, and drying to obtain vanadium-tungsten and titanium products. However, the leaching temperature of a high-concentration mixed solution of ammonia and hydrogen peroxide is higher than 200°C, causing rapid decomposition of the ammonia and hydrogen peroxide in the solution. This not only reduces the leaching rate of the mixed solution for valuable metals, but also increases alkali consumption and energy consumption, which greatly hinders the industrial recovery of catalysts. Patent CN109295313B discloses a method for recovering titanium-tungsten powder from waste SCR denitration catalysts, which includes pretreatment, grinding, ultrasonic acid activation, cooling and dilution, glass fiber filtration, slurry reconstitution, solid-liquid separation, washing and drying, and calcination to obtain titanium-tungsten powder. The overall process is simple and avoids the complex process and high cost caused by the step-by-step extraction of titanium and tungsten metal components. However, the acid solution used is extremely concentrated, and there is no indication of the recovery process for the vanadium element in the filtrate and the waste liquid, which poses a serious environmental hazard. Patent CN112823938A discloses a method for recycling a denitration catalyst, which includes pretreatment, ammonia dissolution, microwave treatment, solid-liquid separation, crushing, ball milling, drying, distillation and other processes to obtain titanium dioxide and a mixed product of vanadium and tungsten respectively. The ammonia dissolution process is enhanced by microwave treatment, resulting in expensive equipment and difficulty in industrial production. At the same time, the subsequent distillation process obtains a mixed powder of ammonium tungstate and ammonium metavanadate, which needs to be further purified and separated before it can be used again, further increasing the complexity of the process. Summary of the Invention

[0005] The present invention provides a method for recycling waste SCR denitration catalysts to prepare titanium tungsten powder and vanadium products. The waste SCR denitration catalysts are pre-treated by dust removal, crushing, grinding, etc., and then activated and subjected to high-pressure leaching with a mixed alkali solution. The metal leaching rate of the waste SCR denitration catalyst is improved by the coordinated action of ammonia water and additives in the mixed solution. After solid-liquid separation, a leaching residue component mainly containing titanium dioxide and tungsten trioxide and a leaching solution containing metavanadate are obtained. The leaching residue is further pickled, washed with water, and dried to obtain a carrier. The vanadium product is obtained by precipitating vanadium in the leaching solution, filtering, and drying. The remaining solution is evaporated and crystallized to recover ammonia and crystalline salt for secondary use. The main purpose of the present invention is to solve the following technical problems in the relevant technology: first, to improve the recycling rate of waste SCR denitration catalysts and reduce environmental pollution; second, by using a mixed alkali solution, the reaction between the carrier and the solution in the alkali leaching process is reduced, thereby simplifying the subsequent process flow and cost.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for recovering waste SCR denitration catalyst to prepare titanium tungsten powder and vanadium products, the method comprising the following steps:

[0008] The waste SCR denitration catalyst powder obtained after pretreatment is immersed in hydrogen peroxide at a solid-liquid ratio of (1-10):1 for activation treatment, and then leached in a mixed alkaline solution at a solid-liquid ratio of (1-5):30, and reacted in a high-pressure reactor with magnetic stirring for 0.5-4 hours;

[0009] The mixture obtained in step (1) is subjected to solid-liquid separation to obtain a leach residue and a leachate. The leach residue is acid-washed and dried to obtain titanium-tungsten powder. The leachate is reused multiple times to achieve a certain vanadium concentration. The pH of the leachate is adjusted, the temperature is lowered, vanadium is precipitated, and the vanadium product is obtained by filtration and drying. The remaining waste liquid is evaporated and crystallized to recover ammonia and crystallized salt for secondary use.

[0010] The pre-treatment mentioned includes dust removal, crushing and grinding:

[0011] The dust removal process involves blowing 0.5MPa high-pressure air, followed by a 0.5MPa-1.0MPa high-pressure air stream to remove dust from the surface of the spent catalyst modules. The modules are then washed with 4-8MPa high-pressure circulating water for 10-60 minutes before drying to remove dust clogged in the pores of the denitration catalyst. Crushing involves mechanically crushing the cleaned spent SCR denitration catalyst into pieces of 1-10mm. Grinding involves grinding the spent SCR denitration catalyst sheets to an average particle size of 10-50μm, producing spent SCR denitration catalyst powder to facilitate the reaction between the reactants.

[0012] The oxidant used in the activation treatment process is a hydrogen peroxide solution with a concentration of 4-10 mol / L and a temperature below 50°C. The valence states of the vanadium element in the waste denitration catalyst mainly include +4 and +3, among which the +4 valence vanadium is more easily reacted with the alkali solution to form ammonium metavanadate. The activation treatment process can oxidize most of the vanadium existing in the +3 valence to the +4 valence. The selective leaching of vanadium elements in the waste catalyst by the mixed alkali solution is further improved, and the time required for the reaction is further reduced. Since the dissolution rate of tungsten trioxide, silicon dioxide, etc. in ammonia water is relatively slow, the leaching rate of tungsten and silicon elements can be further reduced by reducing the reaction time, which is beneficial to the vanadium leaching reaction. In addition, the added oxidant is mainly a hydrogen peroxide solution, which decomposes slowly during the reaction at low temperatures and decomposes into water and oxygen after the reaction is completed, thereby avoiding the further introduction of other impurity elements into the leaching residue.

[0013] The main component of the mixed alkali solution is NH3·H2O, to which one or more compounds such as Na2CO3, NaCl, and NaOH are added, and a mixture of more than one. The concentration of NH3·H2O in the mixed alkali solution is 2-8 mol / L, and the addition of Na2CO3 / NaCl / NaOH makes the sodium ion concentration in the mixed alkali solution 0.1-1.0 mol / L. The single ammonia leaching system has a low leaching rate for vanadium in the waste SCR denitration catalyst, and a high concentration of ammonia is required to achieve the leaching of vanadium. Not only does it cause equipment corrosion and environmental pollution problems, but the high concentration of ammonia causes part of the vanadate produced by the reaction to remain in the leaching residue in the form of precipitates. The mixed alkali solution leaching system increases the leaching rate of vanadium and reduces the concentration of ammonia by adding low-concentration, more reactive sodium compounds. At the same time, the coordinated effect between ammonia and additives in the mixed alkali solution reduces the reaction between the solution and the carrier, which has great advantages in simplifying subsequent processing steps and reducing costs.

[0014] The leaching reaction temperature is 100-180°C, the pressure is 0.4-1 MPa, and the stirring speed is 100-300 rad / min. High temperature can promote the thermodynamics of the reaction between ammonia and the valuable metal elements in the waste SCR denitration catalyst, and stirring further improves the reaction kinetics and the leaching rate.

[0015] The main reactions that may occur during the leaching process are as follows:

[0016] V2O5+2NH3·H2O=2NH4VO3+H2O (1)

[0017] 2NH4VO3+Na2CO3=2NaVO3+(NH4)2CO3 (2)

[0018] 2NH4VO3+NaCl=2NaVO3+NH4Cl (3)

[0019] 2NH4VO3+NaOH=2NaVO3+NH3·H2O (4)

[0020] The solid-liquid separation method is centrifugation, and the centrifugal speed is 1000-1200rad / min. By repeatedly reusing the separated leachate, the content of valuable metal elements in the mixed alkali solution is further increased. The mixed alkali solution can be used multiple times.

[0021] The acid used in the pickling process is one or more of HCl, HNO₃, and H₂SO₄, with a concentration of 1-3 mol / L, a solid-to-liquid ratio of 1:2-5, a temperature of 40-90°C, and a reaction time of 0.5-1.5 hours. The pickling process allows a very small amount of sodium titanate contained in the leached residue to react with the acid solution to form titanic acid, which is retained in the precipitate. It also removes other impurities in the leached residue, such as aluminum and silicon. Furthermore, the sodium ion content in the leached residue is low, allowing the pickling solution to be reused multiple times. The pickling solution produced in subsequent processes can be used to adjust the pH of the leachate to recover the vanadium in the leachate as ammonium metavanadate precipitation, reducing the corrosiveness and pollution of the wastewater, lowering costs, and allowing for multiple uses of the added substances.

[0022] The drying temperature is 120-200°C and the drying time is 30-60 minutes. The drying process not only removes the acid and water contained in the leaching residue, but also decomposes the titanic acid in the leaching residue into titanium dioxide at high temperature, thereby obtaining regenerated titanium tungsten powder for recycling.

[0023] The evaporation and crystallization temperature is 110-200°C, and the ammonia gas and crystallized salt produced by the evaporation and crystallization are reused. The evaporation and crystallization process causes compounds such as ammonia water in the solution to decompose at high temperatures into ammonia gas and water vapor, which are then recovered to produce ammonia water for secondary use. The crystallized salt produced by the evaporation and crystallization process can also be used multiple times and then classified and recovered after component testing.

[0024] Key technical points of the present invention:

[0025] 1. The leaching process of the present invention first adopts hydrogen peroxide activation treatment at low temperature, which ensures the activation effect of hydrogen peroxide on metal elements such as vanadium and tungsten in the waste SCR denitration catalyst, further reduces the amount of hydrogen peroxide used, reduces the treatment cost and equipment requirements of the waste catalyst, reduces resource waste, and improves the leaching rate of valuable metals in the leaching process.

[0026] 2. This invention utilizes a weak alkaline leaching system to produce titanium, tungsten powder, and vanadium products, ensuring carrier cleanliness. This not only allows for unimpeded leaching of valuable metals but also eliminates the need for complex silicon removal processes, saving significant amounts of acid, reducing equipment requirements, and lowering production costs. Furthermore, ammonia and vanadium products are recovered separately by distillation and recycled in the production process, lowering production costs and minimizing environmental pollution.

[0027] 3. The present invention adds a low concentration of sodium salt to ammonia water to obtain a mixed alkali solution for leaching, thereby improving the leaching rate of valuable metal elements in the discarded SCR denitration catalyst during the leaching process. At the same time, the low concentration of sodium ions is not easy to react with the carrier components such as TiO2 and SiO2, thereby ensuring the cleanliness and specific surface area of the carrier. In addition, the use of a weakly alkaline mixed leaching solution also reduces the amount of acid used in the subsequent pickling process. By repeatedly using the alkali solution and acid solution, the consumption of alkali solution and the output of wastewater in the reaction process are reduced, thereby improving the utilization rate of materials. This solves the problem that the existing method of separating and recovering valuable metals using ammonia water has a low leaching rate, resulting in a complex waste catalyst resource separation and recovery process, large alkali consumption, and large wastewater output.

[0028] The common feature of existing technologies is that they only focus on how to recover titanium and tungsten powder, and none of them mention the recovery of related resources in the waste liquid. The outstanding feature of the present invention is that it not only recovers titanium and tungsten powder, but also solves the problem of recovering other resources such as waste liquid from discarded SCR denitration catalysts.

[0029] The beneficial technical effects of the present invention are:

[0030] (1) Titanium tungsten powder is prepared from waste SCR denitration catalysts, simplifying the waste SCR denitration catalyst recovery process. At the same time, it reduces the output of waste liquid, lowers costs and reduces environmental pollution risks.

[0031] (2) By controlling the sodium salt concentration, reaction temperature and reaction time, the reaction between the vanadium element and the mixed alkali solution is enhanced, while the reaction between the alkali solution and the carrier is inhibited, thereby recovering the waste SCR denitrification catalyst in a relatively energy-saving manner.

[0032] (3) Alkali neutralization and precipitation are used to separate vanadium and tungsten components. The obtained products such as ammonium vanadate have the same economic value as vanadium pentoxide. Then, ammonia water and sodium salt are recycled for a second time through evaporation and crystallization, saving resources and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A flow chart was prepared for the method of the present invention. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. A person skilled in the art can fully understand the present invention without the description of these details. The present invention covers any substitutions, modifications, equivalent methods and solutions made within the spirit and scope of the present invention as defined by the claims.

[0035] Implementation Case 1

[0036] like Figure 1 A method for recovering waste SCR denitration catalysts to prepare titanium-tungsten powder includes dust removal, crushing, grinding, activation treatment, high-pressure leaching with mixed alkali solution, filtration, pickling and filtration to obtain leaching residue, further recycling the leachate multiple times to increase the content of elements such as vanadium and tungsten, adjusting the pH, precipitating vanadium, and drying to obtain a vanadium product, and washing and drying the leaching residue to obtain titanium-tungsten powder.

[0037] Pretreatment includes dust removal, crushing, and grinding. Dust removal involves blowing 0.5MPa high-pressure air, followed by high-pressure circulating water washing for 30 minutes and drying to remove dust from the denitration catalyst surface and dust trapped in its pores. The water pressure is set at 4MPa. Crushing involves mechanically crushing the denitration catalyst waste after dust removal to 3-5mm diameters. Grinding involves grinding the waste SCR denitration catalyst flakes to an average particle size of 30-50μm, producing a waste SCR denitration catalyst powder to facilitate the reaction between the reactants. The pretreated powder is activated in a 2mol / L hydrogen peroxide solution at a solid-to-liquid ratio of 1:0.4. It is then added to a mixed alkaline solution (5mol / L NH3·H2O, 0.2mol / L NaOH) at a solid-to-liquid ratio of 1:20. The reaction is carried out in a reactor at 160°C for 3 hours. After cooling, the solution is filtered to obtain a leachate and leach residue. The ammonia concentration in the leachate is maintained above 4mol / L for recycling.

[0038] The filtered leaching residue and 2 mol / L HCl were then added to a stirred reactor at a liquid-to-solid ratio of 5:1. After the reaction was set at 50°C for 1 hour, the acid solution and leaching residue were filtered. The leaching residue was then dried at 150°C for 60 minutes to obtain the titanium-tungsten powder product. The acid concentration in the leaching solution was maintained at 3 mol / L and then reused. After multiple reuses, the leaching solution was neutralized with a mixed alkaline solution to a pH ≥ 10 and a temperature ≤ 20°C. Ammonium vanadate and ammonium tungstate were then precipitated, filtered, and dried to obtain the vanadium and tungsten products.

[0039] Implementation Case 2

[0040] like Figure 1 A method for recovering waste SCR denitration catalysts to prepare titanium-tungsten powder includes dust removal, crushing, grinding, activation treatment, high-pressure leaching with mixed alkali solution, filtration, pickling and filtration to obtain leaching residue, further recycling the leachate multiple times to increase the content of elements such as vanadium and tungsten, adjusting the pH, precipitating vanadium, and drying to obtain a vanadium product, and washing and drying the leaching residue to obtain titanium-tungsten powder.

[0041] Pretreatment includes dust removal, crushing, and grinding. Dust removal involves blowing 0.8 MPa high-pressure air, followed by high-pressure circulating water washing for 30 minutes and drying to remove dust from the denitration catalyst surface and dust trapped in its pores. The water pressure is set at 0.8 MPa. Crushing involves mechanically crushing the denitration catalyst waste after dust removal to 3-5 mm. Grinding involves grinding the waste SCR denitration catalyst flakes to an average particle size of 10-30 μm, producing a waste SCR denitration catalyst powder to facilitate the reaction between the reactants. The pretreated powder is activated in a 1 mol / L hydrogen peroxide solution at a solid-to-liquid ratio of 1:0.5. It is then added to a mixed alkaline solution (6 mol / L NH3·H2O, 0.4 mol / L NaCO3) at a solid-to-liquid ratio of 1:15. The reaction is carried out in a reactor at 180°C for 2 hours. After cooling, the solution is filtered to obtain a leachate and leach residue. The ammonia concentration in the leachate is maintained above 5 mol / L for recycling.

[0042] The filtered leaching residue and 1.5 mol / L HCl were then added to a stirred reactor at a liquid-to-solid ratio of 5:1. The reaction temperature was set at 60°C for 1 hour, and the acid solution and leaching residue were filtered to obtain the obtained solution. The leaching residue was then dried at 150°C for 30 minutes to obtain the titanium-tungsten powder product. The acid concentration in the leaching solution was maintained at 1 mol / L and then reused. After multiple reuses, the leaching solution was neutralized with a mixed alkaline solution to a pH ≥ 10 and a temperature ≤ 20°C. Ammonium vanadate and ammonium tungstate were then precipitated, filtered, and dried to obtain the vanadium and tungsten products.

[0043] Implementation Case 3

[0044] like Figure 1 A method for recovering waste SCR denitration catalysts to prepare titanium-tungsten powder includes dust removal, crushing, grinding, activation treatment, high-pressure leaching with mixed alkali solution, filtration, pickling and filtration to obtain leaching residue, further recycling the leachate multiple times to increase the content of elements such as vanadium and tungsten, adjusting the pH, precipitating vanadium, and drying to obtain a vanadium product, and washing and drying the leaching residue to obtain titanium-tungsten powder.

[0045] Pretreatment includes dust removal, crushing, and grinding. Dust removal involves blowing 0.6 MPa high-pressure air, followed by high-pressure circulating water washing for 60 minutes and drying to remove dust from the denitration catalyst surface and dust trapped in its pores. The water pressure is set at 1.0 MPa. Crushing involves mechanically crushing the denitration catalyst waste after dust removal to 5-8 mm. Grinding involves grinding the waste SCR denitration catalyst flakes to an average particle size of 10-30 μm, producing a waste SCR denitration catalyst powder to facilitate the reaction between the reactants. The pretreated powder is activated in a 2 mol / L hydrogen peroxide solution at a solid-to-liquid ratio of 1:0.3. It is then added to a mixed alkaline solution (8 mol / L NH₃·H₂O, 0.4 mol / L NaOH) at a solid-to-liquid ratio of 1:10. The reaction is carried out in a reactor at 180°C for 1 hour. After cooling, the solution is filtered to obtain a leachate and residue. The ammonia concentration in the leachate is maintained above 4 mol / L for recycling.

[0046] The filtered leached residue and 1.5 mol / L HNO3 were then added to a stirred reactor at a liquid-to-solid ratio of 5:1. The reaction temperature was set at 60°C for 0.5 h, and the acid solution and leached residue were filtered to obtain the obtained acid solution. The leached residue was then dried at 150°C for 50 min to obtain the titanium-tungsten powder product. The acid concentration in the leached solution was maintained at 1 mol / L and then reused. After multiple reuses, the leached solution was neutralized with a mixed alkaline solution to a pH ≥ 10 and a temperature ≤ 20°C. Ammonium vanadate and ammonium tungstate were then precipitated, filtered, and dried to obtain the vanadium and tungsten products.

[0047] Implementation Case 4

[0048] like Figure 1 A method for recovering waste SCR denitration catalysts to prepare titanium-tungsten powder includes dust removal, crushing, grinding, activation treatment, high-pressure leaching with mixed alkali solution, filtration, pickling and filtration to obtain leaching residue, further recycling the leachate multiple times to increase the content of elements such as vanadium and tungsten, adjusting the pH, precipitating vanadium, and drying to obtain a vanadium product, and washing and drying the leaching residue to obtain titanium-tungsten powder.

[0049] Pretreatment includes dust removal, crushing, and grinding. Dust removal involves blowing 0.7 MPa high-pressure air, followed by high-pressure circulating water washing for 40 minutes and drying to remove dust from the denitration catalyst surface and dust trapped in its pores. The water pressure is set at 1.0 MPa. Crushing involves mechanically crushing the denitration catalyst waste after dust removal to 4-8 mm. Grinding involves grinding the waste SCR denitration catalyst flakes to an average particle size of 10-30 μm, producing a waste SCR denitration catalyst powder to facilitate the reaction between the reactants. The pretreated powder is activated in a 2 mol / L hydrogen peroxide solution at a solid-to-liquid ratio of 1:0.2. It is then added to a mixed alkaline solution (7 mol / L NH3·H2O, 0.2 mol / L NaOH) at a solid-to-liquid ratio of 1:20. The reaction is carried out in a reactor at 140°C for 2 hours. After cooling, the solution is filtered to obtain a leachate and leach residue. The ammonia concentration in the leachate is maintained above 4 mol / L for recycling.

[0050] The filtered leaching residue and 2 mol / L HNO3 were then added to a stirred reactor at a liquid-to-solid ratio of 5:1. The reaction temperature was set at 50°C for 0.5 hours, and then the acid solution and leaching residue were filtered to obtain the leaching residue. The leaching residue was then dried at 150°C for 60 minutes to obtain the titanium-tungsten powder product. The acid concentration in the leaching solution was maintained at 1 mol / L and then reused. After multiple reuses, the leaching solution was neutralized with a mixed alkaline solution to a pH ≥ 10 and a temperature ≤ 10°C. Ammonium vanadate and ammonium tungstate were then precipitated, filtered, and dried to obtain the vanadium and tungsten products.

[0051] Implementation Case 5

[0052] like Figure 1 A method for recovering waste SCR denitration catalysts to prepare titanium-tungsten powder includes dust removal, crushing, grinding, activation treatment, high-pressure leaching with mixed alkali solution, filtration, pickling and filtration to obtain leaching residue, further recycling the leachate multiple times to increase the content of elements such as vanadium and tungsten, adjusting the pH, precipitating vanadium, and drying to obtain a vanadium product, and washing and drying the leaching residue to obtain titanium-tungsten powder.

[0053] Pretreatment includes dust removal, crushing, and grinding. Dust removal involves blowing 0.8 MPa high-pressure air, followed by a 60-minute high-pressure circulating water wash followed by drying to remove dust from the denitration catalyst surface and dust trapped in its pores. The water pressure is set at 0.5 MPa. Crushing involves mechanically crushing the denitration catalyst waste after dust removal to 5-8 mm. Grinding involves grinding the waste SCR denitration catalyst flakes to an average particle size of 10-30 μm, producing a waste SCR denitration catalyst powder to facilitate the reaction between the reactants. The pretreated powder is activated in a 4 mol / L hydrogen peroxide solution at a solid-to-liquid ratio of 1:0.1. It is then added to a mixed alkaline solution (7 mol / L NH3·H2O, 0.2 mol / L NaOH, and 0.2 mol / L NaCl) at a solid-to-liquid ratio of 1:15. The reaction is carried out in a reactor at 160°C for 2 hours. After cooling, the solution is filtered to obtain a leachate and leach residue. The ammonia concentration in the leachate is maintained above 4 mol / L and is recycled.

[0054] The filtered leaching residue and 2 mol / L HCl were then added to a stirred reactor at a liquid-to-solid ratio of 6:1. The reaction temperature was set at 50°C for 1 hour, and the acid solution and leaching residue were filtered to obtain the leaching residue. The leaching residue was then dried at 120°C for 60 minutes to obtain the titanium-tungsten powder product. The acid concentration in the leaching solution was maintained at 1 mol / L and then reused. After multiple reuses, the leaching solution was neutralized with a mixed alkaline solution to a pH ≥ 10 and a temperature ≤ 10°C. Ammonium vanadate and ammonium tungstate were then precipitated, filtered, and dried to obtain the vanadium and tungsten products.

[0055] Implementation Case 6

[0056] like Figure 1 A method for recovering waste SCR denitration catalysts to prepare titanium-tungsten powder includes dust removal, crushing, grinding, activation treatment, high-pressure leaching with mixed alkali solution, filtration, pickling and filtration to obtain leaching residue, further recycling the leachate multiple times to increase the content of elements such as vanadium and tungsten, adjusting the pH, precipitating vanadium, and drying to obtain a vanadium product, and washing and drying the leaching residue to obtain titanium-tungsten powder.

[0057] Pretreatment includes dust removal, crushing, and grinding. Dust removal involves blowing 0.6 MPa high-pressure air, followed by a 60-minute high-pressure circulating water wash followed by drying to remove dust from the denitration catalyst surface and dust trapped in its pores. The water pressure is set at 0.6 MPa. Crushing involves mechanically crushing the denitration catalyst waste after dust removal to 5-8 mm. Grinding involves grinding the waste SCR denitration catalyst flakes to an average particle size of 10-20 μm, producing a waste SCR denitration catalyst powder to facilitate the reaction between the reactants. The pretreated powder is activated in a 1 mol / L hydrogen peroxide solution at a solid-to-liquid ratio of 1:0.4. It is then added to a mixed alkaline solution (5 mol / L NH3·H2O, 0.2 mol / L NaOH) at a solid-to-liquid ratio of 1:15. The reaction is carried out in a reactor at 140°C for 3 hours. After cooling, the solution is filtered to obtain a leachate and residue. The ammonia concentration in the leachate is maintained above 4 mol / L for recycling.

[0058] The filtered leached residue and 2 mol / L HSO4 were then added to a stirred reactor at a liquid-to-solid ratio of 6:1. The reaction temperature was set at 50°C for 1 hour, and the acid solution and leached residue were filtered to obtain the leached residue. The leached residue was then dried at 120°C for 40 minutes to obtain the titanium-tungsten powder product. The acid concentration in the leached solution was maintained at 1 mol / L and then reused. After multiple reuses, the leached solution was neutralized with a mixed alkaline solution to a pH ≥ 10 and a temperature ≤ 10°C. Ammonium vanadate and ammonium tungstate were then precipitated, filtered, and dried to obtain the vanadium and tungsten products.

[0059] Implementation Case 7

[0060] like Figure 1 A method for recovering waste SCR denitration catalysts to prepare titanium-tungsten powder includes dust removal, crushing, grinding, activation treatment, high-pressure leaching with mixed alkali solution, filtration, pickling and filtration to obtain leaching residue, further recycling the leachate multiple times to increase the content of elements such as vanadium and tungsten, adjusting the pH, precipitating vanadium, and drying to obtain a vanadium product, and washing and drying the leaching residue to obtain titanium-tungsten powder.

[0061] Pretreatment includes dust removal, crushing, and grinding. Dust removal involves blowing 0.5 MPa high-pressure air, followed by a 60-minute high-pressure circulating water wash followed by drying to remove dust from the denitration catalyst surface and dust trapped in its pores. The water pressure is set at 0.8 MPa. Crushing involves mechanically crushing the denitration catalyst waste after dust removal to a size of 4-8 mm. Grinding involves grinding the waste SCR denitration catalyst flakes to an average particle size of 10-40 μm, producing a waste SCR denitration catalyst powder to facilitate the reaction between the reactants. The pretreated powder is activated in a 3 mol / L hydrogen peroxide solution at a solid-to-liquid ratio of 1:0.1. It is then added to a mixed alkaline solution (5 mol / L NH3·H2O, 0.2 mol / L NaOH) at a solid-to-liquid ratio of 1:20. The reaction is carried out in a reactor at 140°C for 3 hours. After cooling, the solution is filtered to obtain a leachate and residue. The ammonia concentration in the leachate is maintained above 4 mol / L for recycling.

[0062] The filtered leached residue and 2 mol / L HSO4 were then added to a stirred reactor at a liquid-to-solid ratio of 3:1. The reaction temperature was set at 50°C for 1 hour, and the acid solution and leached residue were filtered to obtain the leached residue. The leached residue was then dried at 130°C for 60 minutes to obtain the titanium-tungsten powder product. The acid concentration in the leached solution was maintained at 0.8 mol / L and then reused. After multiple reuses, the leached solution was neutralized with a mixed alkaline solution to a pH ≥ 11 and a temperature ≤ 10°C. Ammonium vanadate and ammonium tungstate were then precipitated, filtered, and dried to obtain the vanadium and tungsten products.

[0063] Implementation Case 8

[0064] like Figure 1 A method for recovering waste SCR denitration catalysts to prepare titanium-tungsten powder includes dust removal, crushing, grinding, activation treatment, high-pressure leaching with mixed alkali solution, filtration, pickling and filtration to obtain leaching residue, further recycling the leachate multiple times to increase the content of elements such as vanadium and tungsten, adjusting the pH, precipitating vanadium, and drying to obtain a vanadium product, and washing and drying the leaching residue to obtain titanium-tungsten powder.

[0065] Pretreatment includes dust removal, crushing, and grinding. Dust removal involves blowing 0.9 MPa high-pressure air, followed by a 60-minute high-pressure circulating water wash followed by drying to remove dust from the denitration catalyst surface and dust trapped in its pores. The water pressure is set at 1.5 MPa. Crushing involves mechanically crushing the denitration catalyst waste after dust removal to 5-10 mm. Grinding involves grinding the waste SCR denitration catalyst flakes to an average particle size of 20-40 μm, producing a waste SCR denitration catalyst powder to facilitate the reaction between the reactants. The pretreated powder is activated in a 1.5 mol / L hydrogen peroxide solution at a solid-to-liquid ratio of 1:2. It is then added to a mixed alkaline solution (8 mol / L NH3·H2O, 1 mol / L NaCl) at a solid-to-liquid ratio of 1:6. The reaction is carried out in a reactor at 160°C for 5 hours. After cooling, the solution is filtered to obtain a leachate and leach residue. The ammonia concentration in the leachate is maintained above 4 mol / L for recycling.

[0066] The filtered leaching residue and 2 mol / L HCl were then added to a stirred reactor at a liquid-to-solid ratio of 2:1. The reaction temperature was set at 70°C for 1 hour, and the acid solution and leaching residue were filtered to obtain the leaching residue. The leaching residue was then dried at 200°C for 20 minutes to obtain the titanium-tungsten powder product. The acid concentration in the leaching solution was maintained at 0.8 mol / L and then reused. After multiple reuses, the leaching solution was neutralized with a mixed alkaline solution to a pH ≥ 11 and a temperature ≤ 10°C. Ammonium vanadate and ammonium tungstate were then precipitated, filtered, and dried to obtain the vanadium and tungsten products.

[0067] Implementation Case 9

[0068] like Figure 1 A method for recovering waste SCR denitration catalysts to prepare titanium-tungsten powder includes dust removal, crushing, grinding, activation treatment, high-pressure leaching with mixed alkali solution, filtration, pickling and filtration to obtain leaching residue, further recycling the leachate multiple times to increase the content of elements such as vanadium and tungsten, adjusting the pH, precipitating vanadium, and drying to obtain a vanadium product, and washing and drying the leaching residue to obtain titanium-tungsten powder.

[0069] Pretreatment includes dust removal, crushing, and grinding. Dust removal involves blowing 1.0 MPa high-pressure air, followed by high-pressure circulating water washing for 20 minutes and drying to remove dust from the denitration catalyst surface and dust trapped in its pores. The water pressure is set at 1.8 MPa. Crushing involves mechanically crushing the denitration catalyst waste after dust removal to 6-10 mm. Grinding involves grinding the waste SCR denitration catalyst flakes to an average particle size of 10-20 μm, producing a waste SCR denitration catalyst powder to facilitate the reaction between the reactants. The pretreated powder is activated in a 3.5 mol / L hydrogen peroxide solution at a solid-to-liquid ratio of 1:0.2. It is then added to a mixed alkaline solution (5 mol / L NH3·H2O, 0.6 mol / L NaCl) at a solid-to-liquid ratio of 1:10. The reaction is carried out in a reactor at 160°C for 5 hours. After cooling, the solution is filtered to obtain a leachate and leach residue. The ammonia concentration in the leachate is maintained above 4 mol / L for recycling.

[0070] The filtered leaching residue and 1.5 mol / L HCl were then added to a stirred reactor at a liquid-to-solid ratio of 4:1. The reaction temperature was set at 30°C for 1 hour, and the acid solution and leaching residue were filtered to obtain the leaching residue. The leaching residue was then dried at 180°C for 30 minutes to obtain the titanium-tungsten powder product. The acid concentration in the leaching solution was maintained at 0.8 mol / L and then reused. After multiple reuses, the leaching solution was neutralized with a mixed alkaline solution to a pH ≥ 11 and a temperature ≤ 10°C. Ammonium vanadate and ammonium tungstate were then precipitated, filtered, and dried to obtain the vanadium and tungsten products.

[0071] Implementation Case 10

[0072] like Figure 1 A method for recovering waste SCR denitration catalysts to prepare titanium-tungsten powder includes dust removal, crushing, grinding, activation treatment, high-pressure leaching with mixed alkali solution, filtration, pickling and filtration to obtain leaching residue, further recycling the leachate multiple times to increase the content of elements such as vanadium and tungsten, adjusting the pH, precipitating vanadium, and drying to obtain a vanadium product, and washing and drying the leaching residue to obtain titanium-tungsten powder.

[0073] Pretreatment includes dust removal, crushing, and grinding. Dust removal involves blowing 0.7 MPa high-pressure air, followed by high-pressure circulating water washing for 35 minutes and drying to remove dust from the denitration catalyst surface and dust trapped in its pores. The water pressure is set at 1.4 MPa. Crushing involves mechanically crushing the denitration catalyst waste after dust removal to a size of 4-7 mm. Grinding involves grinding the waste SCR denitration catalyst flakes to an average particle size of 10-30 μm, producing a waste SCR denitration catalyst powder to facilitate the reaction between the reactants. The pretreated powder is activated in a 4 mol / L hydrogen peroxide solution at a solid-to-liquid ratio of 1:0.1. It is then added to a mixed alkaline solution (4 mol / L NH₃·H₂O, 0.3 mol / L NaCO₃) at a solid-to-liquid ratio of 1:30. The reaction is carried out in a reactor at 160°C for 3 hours. After cooling, the solution is filtered to obtain a leachate and leach residue. The ammonia concentration in the leachate is maintained above 4 mol / L for recycling.

[0074] The filtered leaching residue and 2 mol / L HNO3 were then added to a stirred reactor at a liquid-to-solid ratio of 5:1. The reaction temperature was set at 60°C for 1 hour, and the acid solution and leaching residue were filtered to obtain the leaching residue. The leaching residue was then dried at 180°C for 30 minutes to obtain the titanium-tungsten powder product. The acid concentration in the leaching solution was maintained at 0.5 mol / L and then reused. After multiple reuses, the leaching solution was neutralized with a mixed alkaline solution to a pH ≥ 10 and a temperature ≤ 15°C. Ammonium vanadate and ammonium tungstate were then precipitated, filtered, and dried to obtain the vanadium and tungsten products.

Claims

1. A method for recovering titanium, tungsten and vanadium products from waste SCR denitration catalysts, characterized in that: The following steps are involved: (1) The waste SCR denitration catalyst powder obtained after pretreatment was immersed in a hydrogen peroxide solution at a solid-liquid ratio of 1: (0.1-1) for activation treatment, and then leached in a mixed alkaline solution at a solid-liquid ratio of (1-5): 30, and reacted in a high-pressure reactor with magnetic stirring for 0.5-4 hours; (2) subjecting the mixture obtained in step (1) to solid-liquid separation to obtain leaching residue and leaching liquid, and subjecting the leaching residue to pickling and drying to obtain titanium-tungsten powder; reusing the leaching liquid multiple times to allow vanadium to reach a certain concentration, adjusting the pH of the leaching liquid after cooling to precipitate vanadium, and obtaining a vanadium product after drying; and recovering ammonia and crystalline salt from the remaining waste liquid through evaporation and crystallization for secondary utilization; The main component of the mixed alkali solution in step (1) is NH3·H2O, and one or more of Na2CO3, NaCl, and NaOH are added; the concentration of NH3·H2O is 2-6 mol / L, and the addition of Na2CO3 / NaCl / NaOH makes the sodium ion concentration in the mixed alkali solution 0.1-1.0 mol / L.

2. The method for recovering titanium, tungsten and vanadium products from waste SCR denitration catalyst according to claim 1, characterized in that: The pretreatment includes dust removal, crushing and grinding. The waste SCR denitration catalyst module is air-dust-removed and then washed with high-pressure circulating water for 10-60 minutes before being dried. It is mechanically crushed to 1-10 mm and then ground into powder with an average particle size of 10-50 μm. The air pressure of the air dust removal is 0.5-1.0 MPa, and the water pressure of the high-pressure circulating water washing is 4-8 MPa.

3. The method for recovering titanium, tungsten and vanadium products from waste SCR denitration catalyst according to claim 1, characterized in that: The mixed alkali solution leaching temperature is 100-180° C., the pressure is 0.4-1 MPa, and the stirring speed is 100-300 r / min.

4. The method for recovering waste SCR denitration catalyst to prepare titanium tungsten powder and vanadium products according to claim 1, characterized in that The solid-liquid separation method in step (2) is centrifugation, and the centrifugal speed is 1000-1200 r / min.

5. The method for recovering waste SCR denitration catalyst to prepare titanium, tungsten powder and vanadium products according to claim 1, characterized in that: The acid in the pickling solution in step (2) is one or more of HCl, HNO3, and H2SO4, with a concentration of 1-3 mol / L, a solid-liquid ratio of 1:(2-5), a temperature of 40-90°C, and a reaction time of 0.5-1.5h.

6. The method for recovering titanium, tungsten and vanadium products from waste SCR denitration catalysts according to claim 1, characterized in that: In the step (2), the drying temperature is 120-200° C., and the drying time is 30-60 min.

7. The method for recovering waste SCR denitration catalyst to prepare titanium tungsten powder and vanadium products according to claim 1, characterized in that: The acid wash solution obtained by acid washing and filtration in step (2) is used to adjust the pH of the leachate to 7-8.5, and then the temperature is lowered to below 20° C. to generate ammonium metavanadate precipitate, which is filtered and dried to obtain the vanadium product.

8. The method for recovering waste SCR denitration catalyst to prepare titanium tungsten powder and vanadium products according to claim 1, characterized in that: The evaporation and crystallization temperature of the waste liquid in step (2) is 90-200° C., and the ammonia gas and crystallized salt produced by evaporation and crystallization are reused for a second time.

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