CN111485106A - Method for recovering titanium, vanadium and tungsten in waste denitration catalyst - Google Patents

Abstract

The invention discloses a method for recovering titanium, vanadium and tungsten in waste denitration catalysts. The method first pretreats waste denitration catalysts, and then leaches vanadium elements in waste catalysts through acid leaching reduction; _3. H ₂ O-NaOH leaches the tungsten element in the waste catalyst; the recovered filter residue is acid-dissolved, washed with water, dried and calcined to obtain TiO ₂ products; the recovered vanadium and tungsten leaching solutions are respectively extracted, back-extracted, chemical precipitation, Calcination produces V ₂ O ₅ and WO ₃ . The method of the invention realizes that the leaching rate of V and W elements in the waste denitration catalyst can reach up to 99.3% and 83.6%, realizes high-efficiency leaching and separation, and forms a recovery technology of Ti, V and W in a complete set of waste denitration catalysts, wherein TiO ₂ The recovery rate of V ₂ O ₅ and WO ₃ products can reach 95.2%, and the purity is 92.4%, respectively.

Description

A kind of recovery method of titanium, vanadium and tungsten in waste denitration catalyst

technical field

The invention relates to a method for recovering titanium, vanadium and tungsten in waste SCR denitration catalysts, and belongs to the technical field of waste catalyst recovery.

Background technique

The selective catalytic reduction (SCR) flue gas de-pinning process has been widely used in the denitration engineering of coal-fired power plants due to its high denitration efficiency and good selectivity. In an ideal situation, the denitration SCR catalyst can be used for a long time, but the fly ash will block the micropores of the catalyst and the compounds from the toxic flue gas will cause the catalyst to gradually deactivate during operation, shortening its service life. With the focus of emission reduction in my country's "13th Five-Year Plan" and the promotion of SCR denitration work in coal-fired power plants, cement, steel and other industries, the annual waste volume of waste denitration SCR catalysts will be as high as 250,000 to 300,000 cubic meters in the next few years.

At present, the treatment methods of waste SCR denitration catalysts mainly include incineration, landfill and recycling. If the waste SCR denitration catalyst is disposed of by incineration and landfill, it will not only require a lot of land resources, but also cannot effectively solve the environmental pollution risk of toxic substances. In addition, the SCR denitration catalyst itself contains WO ₃ , V ₂ O ₅ and TiO ₂ are precious resources, and the discarding of waste SCR denitration catalysts will also cause a huge waste of valuable metal resources.

If the useful substances or substances that cause serious pollution to the environment are extracted and recycled from the waste SCR denitration catalyst through physical and chemical methods, it will not only solve the environmental pollution risk of toxic substances, but also avoid the waste of valuable metal resources. However, the current waste SCR denitration catalyst recovery technology has the defect that the valuable metals titanium, vanadium and tungsten cannot achieve high leaching rate at the same time.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a recovery method of titanium, vanadium and tungsten in a waste SCR denitration catalyst for the above-mentioned technical problems, the recovery method realizes the efficient separation and leaching of titanium, vanadium and tungsten elements in the waste SCR denitration catalyst, and The total recovery technology of titanium, vanadium and tungsten in waste SCR denitration catalysts is also proposed.

The technical scheme of the present invention is:

A method for recovering titanium, vanadium and tungsten in a waste denitration catalyst, the method specifically comprises the following steps:

(1) Under high temperature and high pressure conditions, the pretreated waste denitration catalyst is immersed in a reaction kettle containing an acid and a reducing agent at a liquid-solid ratio of 20:1 to react, and after the vanadium element in the denitration catalyst is leached, filter to obtain filter residue and vanadium leachate;

(2) under high temperature and high pressure conditions, the filter residue treated in step (1) is immersed in a reaction kettle containing alkali and auxiliary agent to react, and after leaching the tungsten element in the denitration catalyst, filter to obtain filter residue and tungsten leachate;

(3) after drying the filter residue treated in step (2), adjusting pH with acid, washing with water, drying and calcining to obtain TiO ₂ ;

(4) carry out four countercurrent extractions and three countercurrent back-extractions after adjusting the pH to 1.5～2 of the vanadium leaching solution after the acid leaching reduction treatment in step (1), after the extraction, under high temperature conditions, to the back-extraction water containing vanadium element adding an oxidant to the phase to carry out oxidation reaction, after the reaction, the pH of the reaction solution is adjusted to 1-2 with NH ₃ ·H ₂ O, and then filtered, washed with water and calcined to obtain V ₂ O ₅ ;

(5) performing four countercurrent extractions and three countercurrent back-extractions after adjusting the pH of the tungsten leaching solution after the high-pressure alkali leaching treatment in step (2) to 2 to 3, and evaporating and crystallizing the back-extracted water phase after the extraction, and then calcining, WO ₃ is obtained.

Wherein, in step (1), the pretreatment of the waste denitration catalyst refers to: washing the waste denitration catalyst with high-pressure water for 30 minutes to remove dust and other impurities; after removing dust and other impurities, placing the waste denitration catalyst in a planetary Ball mill in a ball mill and pass through a 200-mesh sieve to obtain a waste denitration catalyst recovery material.

Wherein, in step (1), the high temperature condition is 160-180° C., the acid is H ₂ SO ₄ with a volume fraction of 8%-11%, and the reducing agent is Na ₂ SO ₃ .

Wherein, in step (2), the high temperature condition is 200～250℃, the reaction time is 2～4h, the alkali is NaOH with a concentration of 0.5mol/L, and the auxiliary agent is: NH ₃ ·H with a concentration of 5～8mol/L ₂ O.

Wherein, in step (3), the acid is H ₂ SO ₄ with a volume fraction of 8%, the pH is adjusted to below 5, and the calcination temperature is 550°C.

Wherein, in step (4), the extraction liquid used in the four countercurrent extractions is a mixed solution whose mass fraction is 15%P _204-10 %TBP-75% kerosene, and the extraction time is 6～10min; The extraction solution was H ₂ SO ₄ with a concentration of 1.5 mol/L, the back-extraction time was 10-30 min, the oxidant was KClO ₃ , and the calcination temperature was 500°C.

Wherein, in step (5), the extraction liquid used for four countercurrent extractions is a mixed solution whose mass fraction is 20%N ₂₃₅ +15%TBP+65% kerosene, and the extraction time is 8～10min, and the extraction liquid used for three countercurrent extractions is The extraction solution was NH ₃ ·H ₂ O with a concentration of 4 mol/L, the back-extraction time was 6-8 min, and the calcination temperature was 300°C.

Beneficial effects: the recovery method of the present invention realizes the efficient separation and leaching of Ti, V and W elements in the waste SCR denitration catalyst, the leaching rates of V and W in the present invention can reach 99.3% and 83.6% respectively, and the recovery rate of _TiO2 It reaches 95.2%, the purity is 92.4%, and the recovery rates of V ₂ O ₅ and WO ₃ products reach 72.5% and 75.4%, respectively, which not only solves the environmental pollution risk of toxic substances, but also realizes the resource utilization of valuable metals use.

Description of drawings

Fig. 1 is the flow chart of the inventive method;

Fig. 2 is the XRD spectrogram of the vanadium recovery product that the inventive method obtains;

Fig. 3 is the XRD spectrogram of the tungsten recovery product obtained by the inventive method;

Figure 4 shows the XRD patterns of the recovered product _TiO2 at different temperatures.

Detailed ways

The sample taken in the embodiment of the present invention is a waste SCR vanadium-tungsten-titanium-based denitration catalyst in a power plant, and the content of main oxides in the waste catalyst is determined by XRF, as shown in Table 1.

As shown in Figure 1, the recovery method of titanium, vanadium and tungsten in the waste denitration catalyst of the present invention, the method specifically comprises the following steps:

(1) Rinse the waste SCR denitration catalyst with high-pressure water for 30 minutes to remove dust and other impurities, place the denitration catalyst from which dust and other impurities are removed, and place it in a planetary ball mill for ball milling for 8 hours, and pass through a 200-mesh sieve to obtain the waste denitration catalyst recycling material;

(2) Under the condition of high temperature of 160～180℃, weigh 4 g of the waste denitration catalyst pretreated in step (1) and immerse it into a H ₂ SO ₄ solution with a mass fraction of 8% to 11% at a liquid-solid ratio of 20:1 The H ₂ SO ₄ solution contains Na ₂ SO ₃ , and the mixture with a liquid-solid ratio of 20:1 was placed in a 100 mL high-pressure reactor for 10 h to leaching the vanadium element in the waste denitration catalyst, and the leaching was carried out for filtration treatment , to separate vanadium, tungsten and titanium, and use ICP-OES to measure the content of vanadium in the filtrate;

(3) Under the condition of high temperature of 200～250℃, immerse the filter residue processed in step (2) in a mixed solution of 5～8mol/LNH ₃ ·H ₂ O and 0.5mol/L NaOH, put it in a 100mL autoclave The reaction is carried out for 2 to 4 hours to leaching the tungsten element in the waste denitration catalyst, and after leaching, the tungsten element is filtered to separate the tungsten element and the titanium element, and the content of the tungsten element in the filtrate is determined by ICP-OES;

(4) Dry the filter residue after the filtration treatment in step (3) at 120°C, and then adjust the pH to below 5 (dissolved by sulfuric acid) with H ₂ SO ₄ with a volume fraction of 8%, and shake in a water bath for 5 hours at a constant temperature of 25° C. , washed with water, dried, and calcined in a muffle furnace at 550 °C for 3 h to obtain TiO ₂ products;

(5) after adjusting the pH of the vanadium leaching solution after the acid leaching reduction treatment in step (2) to 1.5～2, use 15%P _204-10 %TBP-75% kerosene as the extraction agent to carry out four countercurrent extractions, and the extraction time is 6 ~ 10min, then use the H ₂ SO ₄ solution with a concentration of 1.5mol/L as the back-extracting agent, and carry out 3-stage counter-current back-extraction on the organic phase loaded with tetravalent vanadium after counter-current extraction at room temperature, and the back-extraction time is 10 ～30min, then add KClO ₃ solution to oxidize tetravalent vanadium to pentavalent vanadium, boil until the solution turns yellow, use NH ₃ ·H ₂ O to adjust pH to 1～2, obtain precipitated ammonium polyvanadate, and then filter and filter After washing with water, then calcined at 500 °C for 2 h in a muffle furnace to obtain V ₂ O ₅ product;

(6) after adjusting the pH of the tungsten leaching solution after the high-pressure alkali leaching treatment in step (3) to 2～3, use 20%N ₂₃₅ +15%TBP+65% kerosene as the extraction agent to carry out four countercurrent extractions, and the extraction time is For 8-10 minutes, use 4 mol/L NH ₃ ·H ₂ O solution as the back-extracting agent, and carry out counter-current back-extraction three times at room temperature for the loaded organic phase after counter-current extraction, and the back-extraction time is 6-8 minutes. The back-extracted water phase is evaporated and crystallized, and after crystallization, it is calcined in a muffle furnace at 300° C. for 2 hours to obtain WO ₃ product.

Table 1 Main oxide components of waste SCR denitration catalyst

Example 1

The above-mentioned waste SCR denitration catalysts are treated by the following steps in sequence:

(1) Rinse the waste SCR denitration catalyst with high-pressure water for 30 minutes to remove dust and other impurities, place the denitration catalyst from which dust and other impurities are removed, and place it in a planetary ball mill for ball milling for 8 hours, and pass through a 200-mesh sieve to obtain the waste denitration catalyst recycling material.

(2) Under the condition of high temperature of 160～180℃, weigh 4 g of the waste denitration catalyst pretreated in step (1), and immerse it into H ₂ SO ₄ with a mass fraction of 8% to 11% at a liquid-solid ratio of 20:1 In the solution, the H ₂ SO ₄ solution contains Na ₂ SO ₃ , and the mixture with a liquid-solid ratio of 20:1 was placed in a 100 mL high pressure reactor for 10 hours to leaching the vanadium element in the waste denitration catalyst, and filtered after leaching. Treatment, to separate vanadium element, tungsten element, titanium element, select ICP-OES to carry out vanadium element leaching content determination, vanadium element leaching concentration is shown in Table 2.

(3) after adjusting the pH of the vanadium leaching solution after the acid leaching reduction treatment in step (2) to 1.5～2, use 15%P _204-10 %TBP-75% kerosene as the extraction agent to carry out four countercurrent extractions, and the extraction time is 6 ~ 10min, then use the H ₂ SO ₄ solution with a concentration of 1.5mol/L as the back-extracting agent, and carry out 3-stage counter-current back-extraction on the organic phase loaded with tetravalent vanadium after counter-current extraction at room temperature, and the back-extraction time is 10 ～30min, then add KClO ₃ solution to oxidize tetravalent vanadium to pentavalent vanadium, boil until the solution turns yellow, use NH ₃ ·H ₂ O to adjust pH to 1～2, obtain precipitated ammonium polyvanadate, and then filter and filter After washing with water, and then calcined in a muffle furnace at ₅₀₀ °C for 2 h to obtain a V ₂ O ₅ product, which was characterized by XRD, as shown in Figure ₂ .

Comparative Example 1

The waste denitration catalyst was immersed in the autoclave with liquid-solid ratios of 10:1, 30:1, 40:1, and 50:1 to react, and the remaining conditions were the same as those in Example 1. The vanadium leaching rate was as shown in Table 2, and the V ₂ O ₅ The recovery rate is shown in Table 3.

Table 2 Effects of different liquid-solid ratios on vanadium leaching solution concentration and vanadium leaching rate

Table 3 Effects of different liquid-solid ratios on V ₂ O ₅ recovery

The results in Table 2 show that the vanadium leaching rate increases with the increase of the liquid-solid ratio in the process of increasing the liquid-solid ratio from 10:1 to 20:1. When the liquid-solid ratio exceeds 20:1, the vanadium leaching rate decreases. Trend, when the liquid-solid ratio is 20:1, the vanadium leaching rate can reach 99.3%. The increase of the liquid-solid ratio within a certain range can improve the vanadium leaching rate. Because the liquid-solid ratio is too low, the resulting solution has a high viscosity, which is not conducive to the dissolution process of the low vanadium salt VOSO ₄ , and may increase the slurry agglomeration. However, if the liquid-solid ratio is too high, the vanadium leaching rate decreases, which may be due to the uneven reaction between the excess acid solution and the solid phase at the bottom of the reactor, resulting in incomplete conversion of V ₂ O ₅ to VOSO ₄ , and if the liquid-solid ratio is too high, the vanadium solution in the leaching solution The decrease of the concentration is not conducive to the subsequent treatment, so the optimal liquid-solid ratio is 20:1.

Figure 2 is the XRD pattern of the recovery of V ₂ O ₅ from the vanadium leaching solution by organic extraction after leaching vanadium element under the condition of the optimum liquid-solid ratio of 20:1. As can be seen from Figure 2, the calcined vanadium recovery product appears at the diffraction angles of 15.34°, 20.26°, 25.56°, 31.00°, etc. V ₂ O ₅ diffraction peaks appear, which are consistent with the X-ray diffraction standard (JCPDS No. The diffraction peaks of 41-1426) are basically the same, and the intensity of the diffraction peaks is high, and the impurity peaks are few, indicating that the crystal purity of V ₂ O ₅ is high.

Example 2

The above-mentioned waste SCR denitration catalysts are treated by the following steps in sequence:

(1) Rinse the waste SCR denitration catalyst with high-pressure water for 30 minutes to remove dust and other impurities, place the denitration catalyst from which dust and other impurities are removed, and place it in a planetary ball mill for ball milling for 8 hours, and pass through a 200-mesh sieve to obtain the waste denitration catalyst recycling material.

(2) Under the condition of high temperature of 160～180℃, weigh 4 g of the waste denitration catalyst pretreated in step (1), and immerse it into H ₂ SO ₄ with a mass fraction of 8% to 11% at a liquid-solid ratio of 20:1 In the solution, the H ₂ SO ₄ solution contains Na ₂ SO ₃ , and the mixture with a liquid-solid ratio of 20:1 was placed in a 100 mL high pressure reactor for 10 hours to leaching the vanadium element in the waste denitration catalyst, and filtered after leaching. In order to separate vanadium, tungsten and titanium elements, ICP-OES was used to determine the leaching content of vanadium elements.

(3) Under the condition of high temperature of 200～250℃, immerse the filter residue processed in step (2) in a mixed solution of 5～8mol/LNH ₃ ·H ₂ O and 0.5mol/L NaOH, put it in a 100mL autoclave The reaction was carried out for 2 to 4 hours to leach the tungsten element in the waste denitration catalyst. After leaching, the tungsten element was filtered to separate the tungsten element and the titanium element. The tungsten element leaching content in the filtrate was determined by ICP-OES. .

(4) after adjusting the pH of the tungsten leaching solution after the high-pressure alkali leaching treatment in step (3) to 2～3, use 20%N ₂₃₅ +15%TBP+65% kerosene as the extraction agent to carry out four countercurrent extractions, and the extraction time is For 8-10 minutes, use 4 mol/L NH ₃ ·H ₂ O solution as the back-extracting agent, and carry out counter-current back-extraction three times at room temperature for the loaded organic phase after counter-current extraction, and the back-extraction time is 6-8 minutes. The back-extracted water phase was evaporated and crystallized, and after crystallization, it was calcined in a muffle furnace at 300 °C for 2 h to obtain a WO ₃ product. The obtained WO ₃ was characterized by XRD, as shown in Figure 3.

Comparative Example 2

In step (3), the concentration of NH ₃ ·H ₂ O in the 100mL autoclave was 0-4 mol/L, and the remaining conditions were the same as those in Example 1, the tungsten leaching rate was shown in Table 4 below, and the recovery rate of WO ₃ was shown in Table 5. Show.

Table 4 Effects of different NH ₃ ·H ₂ O concentrations on tungsten leaching rate

Table 5 Effects of different NH ₃ ·H ₂ O concentrations on the recovery of WO ₃

Increasing the concentration of NH ₃ ·H ₂ O in the leaching solution can increase the concentration of NH ₄ ⁺ in the leaching solution, and NH ₄ ⁺ can enhance the destructive ability of the solid phase structure (filter residue), thereby improving the tungsten leaching rate.

Figure 3 is an XRD pattern of WO ₃ recovered from the tungsten leaching solution by an organic extraction method after leaching tungsten element under the condition that the concentration of NH ₃ ·H ₂ O is 7 mol/L. As can be seen from Figure ₃ , the tungsten recovery product after calcination at 500°C for 2h has diffraction peaks of WO3 at diffraction angles of 23.08°, 23.71°, 24.10°, 28.76°, etc., which are consistent with the X-ray diffraction standard. The diffraction peak heights of (JCPDS No. 20-1324) are consistent. At the same time, the intensity of diffraction peaks and the number of impurity peaks indicate that the crystal purity of WO ₃ is relatively high.

Example 3

The above-mentioned waste SCR denitration catalysts are treated by the following steps in sequence:

(1) Rinse the waste SCR denitration catalyst with high-pressure water for 30 minutes to remove dust and other impurities, place the denitration catalyst from which dust and other impurities are removed, and place it in a planetary ball mill for ball milling for 8 hours, and pass through a 200-mesh sieve to obtain the waste denitration catalyst recycling material.

(2) Under the condition of high temperature of 160～180℃, weigh 4 g of the waste denitration catalyst pretreated in step (1), and immerse it into H ₂ SO ₄ with a mass fraction of 8% to 11% at a liquid-solid ratio of 20:1 In the solution, the H ₂ SO ₄ solution contains Na ₂ SO ₃ , and the mixture with a liquid-solid ratio of 20:1 was placed in a 100 mL high pressure reactor for 10 hours to leaching the vanadium element in the waste denitration catalyst, and filtered after leaching. In order to separate vanadium, tungsten and titanium elements, ICP-OES was used to determine the leaching content of vanadium elements.

(3) Under the condition of high temperature of 160°C and 250°C, the filter residue treated in step (2) was immersed in a mixed solution containing 5-8 mol/L NH ₃ ·H ₂ O and 0.5 mol/L NaOH, and placed under high pressure in 100 mL. React in the reaction kettle for 2 to 4 hours to leach out the tungsten element in the waste denitration catalyst. After leaching, the tungsten element is filtered to separate the tungsten element and the titanium element. ICP-OES is used to determine the tungsten element leaching content.

(4) Dry the filter residue after the filtration treatment in step (3) at 120°C, and then adjust the pH to below 5 (dissolved by sulfuric acid) with H ₂ SO ₄ with a volume fraction of 8%, and shake in a water bath for 5 hours at a constant temperature of 25° C. , washed with water, dried, and calcined in a muffle furnace at 550 °C for 3 h to obtain a TiO ₂ product. The obtained TiO ₂ was characterized by XRD. The XRD comparison spectra of TiO ₂ at 160 °C and 250 °C are shown in Figure 4. At the optimal tungsten leaching temperature, more tungsten can be leached, and the resulting titanium dioxide has a higher purity.

(5) After adjusting the pH of the tungsten leaching solution after the high-pressure alkali leaching treatment in step (3) to 2～3, use 20%N ₂₃₅ +15%TBP+65% kerosene as the extraction agent to carry out four countercurrent extractions, and the extraction time is For 8-10 minutes, use 4 mol/L NH ₃ ·H ₂ O solution as the back-extracting agent, and carry out counter-current back-extraction three times at room temperature for the loaded organic phase after counter-current extraction, and the back-extraction time is 6-8 minutes. The back-extracted water phase is evaporated and crystallized, and after crystallization, it is calcined in a muffle furnace at 300° C. for 2 hours to obtain WO ₃ product.

Comparative Example 3

In step (3), the high temperature condition is 150-190° C., and other conditions are the same as those in Example 1. The tungsten leaching rate is shown in Table 6 below, and the WO ₃ recovery rate is shown in Table 7.

Table 6 Effects of different temperatures on tungsten leaching rate

Table 7 shows the effect of different temperatures on the recovery rate of WO ₃

When the reaction temperature was increased from 150℃ to 200℃, the tungsten leaching rate increased rapidly, and when the reaction temperature exceeded 200℃, the tungsten leaching rate changed slowly. It can be seen from the molecular thermal motion that other conditions remain unchanged. With the increase of temperature, the motion speed of molecules and ions increases correspondingly, and at the same time, the viscosity of the solution decreases and the dissolution process of WO ₃ is accelerated. Therefore, it can be seen from Table 7 that the temperature between 200 and At 250 °C, the recovery rate of WO ₃ can reach 75.4%.

Based on the above results, it can be seen that the processes of Example ₁ , Example ₂ and Example ₃ of the present invention can achieve efficient leaching and separation _of titanium, tungsten and tungsten in waste SCR catalysts. It has the effect of high purity and high recovery rate.

Claims (7)

1. the recovery method of titanium, vanadium and tungsten in a waste denitration catalyst, is characterized in that, the method specifically comprises the steps: (1) Under high temperature and high pressure conditions, the pretreated waste denitration catalyst is immersed in a reaction kettle containing an acid and a reducing agent at a liquid-solid ratio of 20:1 to react, and after the vanadium element in the denitration catalyst is leached, filter to obtain filter residue and vanadium leachate; (2) under high temperature and high pressure conditions, the filter residue treated in step (1) is immersed in a reaction kettle containing alkali and auxiliary agent to react, and after leaching the tungsten element in the denitration catalyst, filter to obtain filter residue and tungsten leachate; (3) after drying the filter residue treated in step (2), adjusting pH with acid, washing with water, drying and calcining to obtain TiO ₂ ; (4) carry out four countercurrent extractions and three countercurrent back-extractions after adjusting the pH to 1.5～2 of the vanadium leaching solution after the acid leaching reduction treatment in step (1), after the extraction, under high temperature conditions, to the back-extraction water containing vanadium element adding an oxidant to the phase to carry out oxidation reaction, after the reaction, the pH of the reaction solution is adjusted to 1-2 with NH ₃ ·H ₂ O, and then filtered, washed with water and calcined to obtain V ₂ O ₅ ; (5) performing four countercurrent extractions and three countercurrent back-extractions after adjusting the pH of the tungsten leaching solution after the high-pressure alkali leaching treatment in step (2) to 2 to 3, and evaporating and crystallizing the back-extracted water phase after the extraction, and then calcining, WO ₃ is obtained. 2. the recovery method of titanium, vanadium and tungsten in waste denitration catalyst according to claim 1, is characterized in that: in step (1), after the pretreatment of waste denitration catalyst refers to: waste denitration catalyst is carried out with high pressure water Rinse to remove dust and other impurities; after removing dust and other impurities, place the waste denitration catalyst in a planetary ball mill for ball milling and sieve to obtain the waste denitration catalyst recovery material. 3. the recovery method of titanium, vanadium and tungsten in waste denitration catalyst according to claim 1, is characterized in that: in step (1), high temperature condition is 160～180 ℃, and acid is 8%～11% by volume fraction of H ₂ SO ₄ , and the reducing agent is Na ₂ SO ₃ . 4. the recovery method of titanium, vanadium and tungsten in waste denitration catalyst according to claim 1, is characterized in that: in step (2), high temperature condition is 200～250 ℃, reaction time is 2～4h, and alkali is concentration It is 0.5mol/L NaOH, and the auxiliary agent is: NH ₃ ·H ₂ O with a concentration of 5-8 mol/L. 5. The method for recovering titanium, vanadium and tungsten in the waste denitration catalyst according to claim 1, wherein in step (3), the acid is H ₂ SO ₄ with a volume fraction of 8%, and the pH is adjusted to 5 Hereinafter, the firing temperature is 550°C. 6. the recovery method of titanium, vanadium and tungsten in the waste denitration catalyst according to claim 1, is characterized in that: in step (4), the used extraction liquid of four countercurrent extractions is that mass fraction is 15%P _204-10 %TBP-75% kerosene mixture, the extraction time is 6-10min; the back-extraction used in the three countercurrent back-extractions is H ₂ SO ₄ with a concentration of 1.5mol/L, the back-extraction time is 10-30min, and the oxidant is KClO _3. The calcination temperature is 500℃. 7. the recovery method of titanium, vanadium and tungsten in the waste denitration catalyst according to claim 1, is characterized in that: in step (5), the used extraction liquid of four countercurrent extractions is that mass fraction is 20%N ₂₃₅ +15 The mixed solution of %TBP+65% kerosene, the extraction time is 8-10min, the back-extraction liquid used for the three countercurrent back-extractions is NH ₃ ·H ₂ O with a concentration of 4mol/L, the back-extraction time is 6-8min, the calcination temperature is 300°C.

Images