A method for efficiently extracting and separating vanadium, tungsten, and titanium from waste SCR catalysts

Abstract

The present invention belongs to the field of recycling of hazardous solid waste, and relates to a method for efficiently extracting and separating vanadium, tungsten, and titanium from waste SCR catalysts. The method comprises the following steps: obtaining waste SCR catalyst powder; mixing the waste SCR catalyst powder with a roasting agent step by step and roasting to obtain a roasted material; wherein the roasting agent is a mixture of at least two basic substances, and at least one of the basic substances is a strong basic substance; adding the roasted material into a leaching agent for leaching reaction, and performing solid-liquid separation after leaching to obtain a leached residue and a leachate. The leachate is a mixed solution of metal element compounds soluble in the leaching agent, and the leached residue is a metal element compound insoluble in the leaching agent. The present invention is efficient and rapid, with increased extraction amounts of vanadium and tungsten, reduced costs, and is easy to industrialize, having potential industrial application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of recycling of hazardous solid waste, and relates to a method for efficiently extracting and separating vanadium, tungsten, and titanium from waste SCR catalysts. Background Art

[0002] Waste SCR denitration catalysts contain important metal resources such as vanadium, tungsten, and titanium, and have great recycling value. According to the current market price, the recycling of these valuable metal resources will generate an output value of hundreds of millions of yuan. Therefore, the recycling of waste SCR denitration catalysts has important economic, environmental, and social benefits.

[0003] Currently, the method for recycling vanadium and tungsten from waste SCR denitration catalysts involves direct large - batch mixing of solids for roasting reactions, resulting in poor reaction effects. For example, in the patent application with the application number CN112390285A and the title "A Method for Recycling Vanadium - Titanium - Based Waste Catalysts", under the action of a reducing agent, the waste catalyst and chlorine are subjected to a chlorination reaction at high temperature to generate gaseous chlorides. The gaseous chlorides are subjected to fractional condensation to obtain solid phases containing W and Mo, and a liquid phase containing Ti and V respectively; then a vanadium - removing reagent is added to the liquid phase containing Ti and V, and distilled to obtain a solid phase containing V and pure TiCl4;

[0004] Adding a single roasting agent in the roasting reaction makes the required environmental temperature high at the beginning of the reaction, and the heating process is time - consuming and energy - consuming. For example, in the patent application with the application number 2016107978809 and the title "A Method for Recycling Waste SCR Catalysts", a roasting aid is added to the waste SCR catalyst. The roasting aid is sodium carbonate. The mixture is synchronously pulverized and stirred evenly to obtain a mixed material, which is roasted. After roasting, it is impregnated with deionized water, filtered to obtain a filtrate and a filter residue. Calcium fluoride is added to the filtrate to precipitate vanadium, tungsten, and molybdenum. The filter residue is washed with dilute hydrochloric acid, separated, the precipitate is dissolved by hydrochloric acid impregnation, precipitated with ammonia water, the residue is dissolved with ammonia water, the filtrate is ammonium paratungstate / or ammonium molybdate, and the filter residue is ammonium metavanadate;

[0005] The existing methods for recycling vanadium and tungsten also have the problem of low leaching rate in actual production. For example, in the patent application with the application number CN105648219A and the title "A Process Method for Recycling Vanadium from Honeycomb - Type Waste SCR Catalysts", the waste catalyst is crushed, washed with water to remove dust and debris, dried and ground into powder, then leached under high temperature and pressure. After solid - liquid separation, a filter residue and a leaching solution are obtained. The filter residue is washed with deionized water to remove sodium, tungsten, and vanadium, and the washing water is recycled. Hydrochloric acid is added to the leaching solution, silicon impurities are filtered out, hydrochloric acid is added again, ion - exchanged and desorbed to obtain a solution containing ammonium paratungstate and ammonium metavanadate. Ammonium salt is added to the mixed solution, and after solid - liquid separation and drying, ammonium metavanadate is precipitated and crystallized. However, in actual production, the leaching rate is low, resulting in low value and hindering feasibility.

[0006] Therefore, there is a need to design a method for efficiently extracting and separating vanadium, tungsten, and titanium from waste SCR catalysts to improve the above problems. Summary of the Invention

[0007] The purpose of the present invention is to overcome the defects of the prior art and provide a method for efficiently extracting and separating vanadium, tungsten, and titanium from waste SCR catalysts.

[0008] The present invention provides a method for efficiently extracting and separating vanadium, tungsten, and titanium from waste SCR catalysts, which includes the following steps:

[0009] S1, obtaining waste SCR catalyst powder;

[0010] S2, mixing the waste SCR catalyst powder with a roasting agent step by step, roasting to obtain a roasted material; wherein, the roasting agent is a mixture of at least two alkaline substances, and at least one of the alkaline substances is a strong alkaline substance;

[0011] S3, adding the roasted material into a leaching agent for leaching reaction, and performing solid-liquid separation after leaching to obtain a leaching residue and a leaching solution. The leaching solution is a mixed solution of metal element compounds soluble in the leaching agent, and the leaching residue is a metal element compound insoluble in the leaching agent;

[0012] Further, the waste SCR catalyst is a waste SCR denitration catalyst of a vanadium-tungsten system;

[0013] Further, in step S1, the particle size of the waste SCR catalyst powder is below 100 mesh;

[0014] Further, in step S2, the method of step-by-step mixing is as follows:

[0015] Dividing the waste SCR catalyst powder and the roasting agent into several small portions respectively and mixing them in one-to-one correspondence to obtain several portions of mixed materials;

[0016] Mixing several portions of the mixed materials as a whole again;

[0017] Further, the dosage of the roasting agent is 10%-100% of the mass of the waste SCR catalyst;

[0018] Further, the roasting agent is a mixture of a strong alkaline substance and an alkali metal salt;

[0019] The alkali metal element in the alkali metal salt is the same as the metal element in the strong alkaline substance;

[0020] Preferably, the alkali metal element is sodium;

[0021] The alkali metal salt is selected from any one of carbonates and bicarbonates;

[0022] Furthermore, in the roasting agent, the mass ratio of the alkali metal salt to the strong base substance is 0.25 - 4:1;

[0023] Furthermore, in step S2, the roasting is carried out in a stepwise manner, specifically as follows:

[0024] After the mixed material undergoes the first roasting reaction at the first roasting temperature, the temperature is raised to the second roasting temperature for the second roasting reaction;

[0025] Preferably, the conditions for the first roasting reaction are:

[0026] The first roasting temperature is 500 - 600 °C, and the time for the first roasting reaction is 0.5 - 2 h;

[0027] The second roasting temperature is 700 - 850 °C, and the time for the second roasting reaction is 0.5 - 2 h;

[0028] Furthermore, in step S3, the leaching agent is water, and the solid-liquid mass ratio of the roasted material to the leaching agent is 1:2 - 4;

[0029] Furthermore, in step S3, the conditions for the leaching reaction are: heating the leaching system at 40 - 60 °C, and the leaching time is 3 - 5 h;

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] The method for efficiently extracting and separating vanadium, tungsten, and titanium from waste SCR catalysts of the present invention is efficient and rapid, reduces costs, improves the extraction amounts of vanadium and tungsten, is easy to industrialize, and has potential industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The following drawings are only schematic illustrations and explanations of the present invention and are not used to limit the scope of the present invention, where:

[0033] Figure 1 : Schematic flow chart of the method for efficiently extracting and separating vanadium, tungsten, and titanium from waste SCR catalysts of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] In order to make the objectives, technical solutions, design methods, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below through specific embodiments with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] As Figure 1 shown, the present invention provides a method for efficiently extracting and separating vanadium, tungsten, and titanium from waste SCR catalysts, and the method includes the following steps:

[0036] S1. Obtain waste SCR catalyst powder;

[0037] The waste SCR catalyst is a waste SCR denitration catalyst of a vanadium-tungsten system; the particle size of the waste SCR catalyst powder is below 100 mesh;

[0038] S2. Mix the waste SCR catalyst powder and the roasting agent step by step, and roast to obtain a roasted material; wherein, the roasting agent is a mixture of at least two basic substances, and at least one of the basic substances is a strong basic substance;

[0039] The method of step-by-step mixing is as follows:

[0040] Divide the waste SCR catalyst powder and the roasting agent into several small portions respectively and mix them one by one to obtain several portions of mixed materials;

[0041] Mix several portions of the mixed materials as a whole again;

[0042] The dosage of the roasting agent is 10%-100% of the mass of the waste SCR catalyst;

[0043] The roasting agent is a mixture of a strong basic substance and an alkali metal salt;

[0044] The alkali metal element in the alkali metal salt is the same as the metal element in the strong basic substance;

[0045] The alkali metal element is sodium; the alkali metal salt is selected from any one of carbonates and bicarbonates;

[0046] In the roasting agent, the mass ratio of the alkali metal salt to the strong basic substance is 0.25-4:1;

[0047] The roasting is step-by-step roasting. After the mixed material is subjected to the first roasting reaction at the first roasting temperature, it is heated to the second roasting temperature for the second roasting reaction;

[0048] The conditions of the first roasting reaction are: the first roasting temperature is 500-600°C, and the time of the first roasting reaction is 0.5-2h; the second roasting temperature is 700-850°C, and the time of the second roasting reaction is 0.5-2h;

[0049] S3. Add the roasted material to the leaching agent for leaching reaction. After leaching is completed, perform solid-liquid separation to obtain a leaching residue and a leaching solution. The leaching solution is a mixed solution of metal element compounds soluble in the leaching agent, and the leaching residue is a metal element compound insoluble in the leaching agent;

[0050] The leaching agent is water, and the solid-liquid mass ratio of the roasted material to the leaching agent is 1:2-4;

[0051] The conditions for the leaching reaction are as follows: heating the leaching system at 40 - 60°C, and the leaching time is 3 - 5 h;

[0052] Example 1: The waste SCR denitration catalyst of the vanadium-tungsten system was subjected to cleaning, drying, mechanical crushing, and fine grinding pretreatment to obtain waste SCR catalyst powder with a particle size of less than 70 mesh. 100 g of the waste SCR catalyst was weighed and mixed step by step with 20 g of sodium carbonate and 20 g of sodium hydroxide. Specifically, 100 g of the waste SCR catalyst powder was divided into several small portions and mixed one-to-one with 20 g of sodium carbonate and 20 g of sodium hydroxide respectively to obtain several portions of mixed materials. Then, several portions of the mixed materials were mixed together again for roasting reaction. During the roasting process, the reaction was carried out at 500°C for 1 h in a muffle furnace first, and then at 700°C for 1 h to obtain roasted materials. The roasted materials were mixed with water according to a solid-liquid mass ratio of 1:3 and subjected to water leaching reaction at 40°C for 3 h. After the water leaching reaction, solid-liquid separation was carried out. The leaching solution was a mixed solution of sodium salts containing tungsten and vanadium, and the leaching residue was sodium titanate solid;

[0053] According to the above specific process steps, the following results were obtained: the vanadium leaching rate was 88.95%, and the tungsten leaching rate was 88.47%;

[0054] Example 2

[0055] The waste SCR denitration catalyst of the vanadium-tungsten system was subjected to cleaning, drying, mechanical crushing, and fine grinding pretreatment to obtain waste SCR catalyst powder with a particle size of less than 100 mesh. First, 100 g of the waste SCR catalyst was weighed and mixed step by step with 30 g of sodium carbonate and 10 g of sodium hydroxide. Specifically, 100 g of the waste SCR catalyst powder was divided into several small portions and mixed one-to-one with 30 g of sodium carbonate and 10 g of sodium hydroxide respectively to obtain several portions of mixed materials. Then, several portions of the mixed materials were mixed together again for roasting reaction. During the roasting process, the reaction was carried out at 600°C for 0.5 h in a muffle furnace first, and then at 700°C for 1.5 h to obtain roasted materials. The roasted materials were mixed with water according to a solid-liquid mass ratio of 1:4 and subjected to water leaching reaction at 50°C for 3 h. After the water leaching reaction, solid-liquid separation was carried out. The leaching solution was a mixed solution of sodium salts containing tungsten and vanadium, and the leaching residue was sodium titanate solid;

[0056] According to the above specific process steps, the following results were obtained: the vanadium leaching rate was 92.86%, and the tungsten leaching rate was 92.42%;

[0057] Example 3

[0058] The waste SCR denitration catalyst of the vanadium-tungsten system is subjected to cleaning, drying, mechanical pulverization, and fine grinding pretreatment to obtain waste SCR catalyst powder with a particle size of less than 200 mesh. Weigh 20 g of the waste SCR catalyst and mix it with 6 g of sodium carbonate and 2 g of sodium hydroxide step by step. Specifically, first divide 20 g of the waste SCR catalyst powder, 6 g of sodium carbonate, and 2 g of sodium hydroxide into several small portions and mix them in one-to-one correspondence to obtain several portions of mixed materials. Then, mix several portions of the mixed materials together again and carry out a roasting reaction. During the roasting process, first react at 600 °C in a muffle furnace for 0.5 h, and then react at 700 °C for 1.5 h to obtain roasted materials. Mix the roasted materials with water according to a solid-liquid mass ratio of 1:4 and carry out a water leaching reaction at 60 °C for 4 h. After the water leaching reaction is completed, carry out solid-liquid separation. The leaching solution is a mixed solution of sodium salts containing tungsten and vanadium, and the leaching residue is sodium titanate solid;

[0059] According to the above specific process steps, the following results are obtained: the vanadium leaching rate is 93.23%, and the tungsten leaching rate is 94.23%;

[0060] Comparative Example 1: The roasting agent is sodium carbonate, and other reaction conditions are the same as those in this application;

[0061] The waste SCR denitration catalyst of the vanadium-tungsten system is subjected to cleaning, drying, mechanical pulverization, and fine grinding pretreatment to obtain waste SCR catalyst powder with a particle size of less than 100 mesh. Weigh 100 g of the waste SCR catalyst and mix it with 40 g of sodium carbonate for a roasting reaction. During the roasting process, first react at 600 °C in a muffle furnace for 0.5 h, and then react at 700 °C for 1.5 h to obtain roasted materials. Mix the roasted materials with water according to a solid-liquid mass ratio of 1:4 for a water leaching reaction for 4 h. After the water leaching reaction is completed, carry out solid-liquid separation. The leaching solution is a mixed solution of sodium salts containing tungsten and vanadium, and the vanadium leaching rate is 78.53%, and the tungsten leaching rate is 82.38%;

[0062] Comparative Example 2: The roasting reaction is at one temperature, and other reaction conditions are the same as those in this application;

[0063] The waste SCR denitration catalyst of the vanadium-tungsten system is subjected to cleaning, drying, mechanical pulverization, and fine grinding pretreatment to obtain waste SCR catalyst powder with a particle size of less than 100 mesh. Weigh 100 g of the waste SCR catalyst and mix it with 30 g of sodium carbonate and 10 g of sodium hydroxide for a roasting reaction. During the roasting process, react at 700 °C for 2 h to obtain roasted materials. Mix the roasted materials with water according to a solid-liquid mass ratio of 1:4 for a water leaching reaction for 4 h. After the water leaching reaction is completed, carry out solid-liquid separation. The leaching solution is a mixed solution of sodium salts containing tungsten and vanadium, and the vanadium leaching rate is 72.33%, and the tungsten leaching rate is 78.47%;

[0064] Comparative Example 3: The roasting agent is a mixture of sodium carbonate and sodium chloride, and other reaction conditions are the same as those of the present application;

[0065] The waste SCR denitration catalyst of the vanadium-tungsten system is subjected to cleaning, drying, mechanical crushing, and fine grinding pretreatment to obtain waste SCR catalyst powder, and the particle size of the waste SCR catalyst powder is below 100 mesh; 100 g of the waste SCR catalyst is weighed and mixed with 30 g of sodium carbonate and 10 g of sodium chloride for roasting reaction. During the roasting process, the reaction is carried out at 600 °C in a muffle furnace for 0.5 h, and then at 700 °C for 1.5 h to obtain the roasted material. The roasted material is mixed with water according to a solid-liquid mass ratio of 1:4 for water leaching reaction for 4 h. After the water leaching reaction is completed, solid-liquid separation is carried out, and the leaching solution is a mixed solution of sodium salts containing tungsten and vanadium. The vanadium leaching rate is 75.72%, and the tungsten leaching rate is 85.23%;

[0066] Comparative Example 4: The mixing ratio of the roasting agent as sodium carbonate and sodium hydroxide is not within the range set in the present application, and other reaction conditions are the same as those of the present application;

[0067] The waste SCR denitration catalyst of the vanadium-tungsten system is subjected to cleaning, drying, mechanical crushing, and fine grinding pretreatment to obtain waste SCR catalyst powder, and the particle size of the waste SCR catalyst powder is below 100 mesh; 100 g of the waste SCR catalyst is weighed and mixed with 35 g of sodium carbonate and 5 g of sodium chloride for roasting reaction. During the roasting process, the reaction is carried out at 600 °C in a muffle furnace for 1 h, and then at 700 °C for 1 h to obtain the roasted material. The roasted material is mixed with water according to a solid-liquid mass ratio of 1:4 for water leaching reaction for 4 h. After the water leaching reaction is completed, solid-liquid separation is carried out, and the leaching solution is a mixed solution of sodium salts containing tungsten and vanadium. The vanadium leaching rate is 52.56%, and the tungsten leaching rate is 61.84%;

[0068] Therefore, in Example 1, Example 2, and Example 3, by mixing the waste SCR catalyst powder with the roasting agent step by step and roasting step by step, a roasted material is obtained. The roasting agent is a mixture of at least two basic substances, and at least one of the basic substances is a strong base substance. The roasted material is added to the leaching agent for leaching reaction. After the leaching is completed, solid-liquid separation is carried out to obtain a leaching residue and a leaching solution. The leaching solution is a mixed solution of sodium salts containing tungsten and vanadium. The vanadium and tungsten leaching rates separated from the mixed solution of sodium salts of tungsten and vanadium are between 89% and 94%; when the roasting agent in Comparative Examples 1-4 is a single roasting agent, or the roasting reaction is at one temperature, or at least one of the roasting agent mixtures is not a strong base substance, or the mixing ratio of the roasting agent is different, the vanadium and tungsten leaching rates are between 52% and 80%. By using the method of the present application, it is efficient and rapid, and the vanadium and tungsten leaching rates obtained from the waste SCR catalyst are increased by 10%-30%;

[0069] As can be seen from Example 2 and Example 3, the vanadium and tungsten contents extracted and separated from the waste SCR catalyst powder with a particle size of less than 200 mesh are close to those extracted and separated from the waste SCR catalyst powder with a particle size of less than 100 mesh, and both can improve the extraction and separation of vanadium and tungsten contents. Therefore, the particle size of the waste SCR catalyst powder is less than 100 mesh;

[0070] It is worth noting that in the process method for extracting and separating vanadium and tungsten from waste SCR denitration catalysts of the present invention, the waste SCR catalyst powder and the roasting agent are mixed step by step and roasted step by step to obtain a roasted material; the step-by-step mixing of the waste SCR catalyst powder and the roasting agent is conducive to uniform mixing, and the step-by-step roasting is conducive to the full reaction of roasting; the roasting agent is a mixture of at least two basic substances, and at least one of the basic substances is a strong base substance. During the step-by-step roasting reaction process, after the mixed material is subjected to the first roasting reaction at the first roasting temperature, the temperature is raised to the second roasting temperature for the second roasting reaction; it saves energy consumption and time, effectively increases the reaction amount between the roasting agent and the waste SCR catalyst. The roasted material is added to the leaching agent for leaching reaction. After leaching is completed, solid-liquid separation is carried out to obtain a leaching residue and a leaching solution. The leaching solution is a mixed solution of metal element compounds soluble in the leaching agent, that is, a mixed solution of sodium salts containing tungsten and vanadium; among them, the roasting agent of the present invention is a mixture of at least two basic substances, compared with the roasting agent in the prior art, sodium hydroxide is added, and two roasting temperature environments are set, which saves energy consumption and makes full use of the time during the heating process, enabling some reactions to proceed in advance, saving time costs, making the extraction and separation of vanadium, tungsten, and titanium from waste SCR catalysts efficient and rapid. The leaching agent can meet the requirements by using water, reducing costs, reducing costs and increasing efficiency, improving the extraction amounts of vanadium and tungsten, being easy to industrialize, and having potential industrial application prospects.

[0071] The various embodiments of the present invention have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art in the technical field without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other ordinary technical personnel in the technical field to understand the embodiments disclosed herein.

Claims

1. A method for efficiently extracting and separating vanadium, tungsten and titanium from waste SCR catalysts, characterized in that: The method comprises the following steps: S1, obtaining spent SCR catalyst powder; S2, mixing the waste SCR catalyst powder with a calcining agent in steps, and calcining to obtain a calcined material; The waste SCR catalyst is a waste SCR denitration catalyst of a vanadium-tungsten system; The amount of the calcining agent is 10%-100% of the mass of the waste SCR catalyst; The calcining agent is a mixture of a strong base substance and an alkali metal salt; The alkali metal element in the alkali metal salt is the same as the metal element in the strong base substance; The alkali metal element is sodium; The alkali metal salt is selected from any one of carbonate and bicarbonate; In the calcining agent, the mass ratio of the alkali metal salt to the strong base substance is 0.25-4:1; The step-by-step mixing method is: Dividing the waste SCR catalyst powder and the calcining agent into several small portions and mixing them one by one to obtain several portions of mixed materials; Mixing several portions of the mixed materials again as a whole; The calcination is performed in steps, specifically: After the mixed material is subjected to a first calcination reaction at a first calcination temperature, the temperature is raised to a second calcination temperature for a second calcination reaction; The conditions of the first calcination reaction are: The first calcination temperature is 500-600°C, and the first calcination reaction time is 0.5-2h; The second calcination temperature is 700-850°C, and the second calcination reaction time is 0.5-2h; S3, adding the roasted material to a leaching agent to carry out a leaching reaction, and after the leaching is completed, performing solid-liquid separation to obtain leaching residue and leaching liquid, wherein the leaching liquid is a mixed solution of metal element compounds soluble in the leaching agent, and the leaching residue is a metal element compound insoluble in the leaching agent; The leaching agent is water; The solid-liquid mass ratio of the roasted material to the leaching agent is 1:2-4; The conditions of the leaching reaction are: the leaching reaction temperature is 40-60° C., and the leaching reaction time is 3-5 hours.

2. A method for efficiently extracting and separating vanadium, tungsten and titanium from a waste SCR catalyst according to claim 1, characterized in that: In step S1, the particle size of the spent SCR catalyst powder is less than 100 meshes.

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