Method for removing iron from spent denitration catalyst and recovering denitration catalyst powder

Abstract

The present invention relates to the technical field of hazardous waste recycling and utilization, and discloses a method for removing iron from a waste denitration catalyst and recovering denitration catalyst powder. The method comprises: (1) pre-treating the waste denitration catalyst; (2) placing the pre-treated waste denitration catalyst in an acidic solution for ultrasonic treatment, and then removing and drying; (3) ball-milling the solid product obtained in step (2), then mixing the ball-milled product with an alkaline solution for reaction, followed by solid-liquid separation and washing the solid portion; (4) reacting the product obtained in step (3) with a reducing acid solution in a magnetic stirring device, then performing solid-liquid separation and washing and drying the solid portion, wherein the reaction conditions include: a temperature of 30 to 90° C. and a reaction time of 1 to 4 hours. The method can deeply remove iron from the waste denitration catalyst and can significantly restore and increase the specific surface area of ​​the recovered denitration catalyst powder.

Description

Technical Field

[0001] The present invention relates to the technical field of hazardous waste recycling, and in particular to a method for removing iron from a waste denitration catalyst and recovering denitration catalyst powder. Background Art

[0002] Selective catalytic reduction (SCR) denitrification technology is currently the most mature flue gas denitrification technology. As the core of SCR denitrification technology, SCR denitrification catalysts can become inactivated during use due to metal poisoning or ash accumulation and clogging. Current catalyst regeneration processes can effectively restore the activity of denitrification catalysts. However, after multiple regeneration cycles, structural damage to the denitrification catalyst is inevitable. When the denitrification catalyst is damaged to the point where it cannot be regenerated, recycling becomes an inevitable option. Spent denitrification catalysts contain 75% to 90% by weight of TiO2, 4% to 10% by weight of WO3, 0.5% to 1.5% by weight of V2O5, as well as structural auxiliary components such as SiO2 and Al2O3. Their recycling not only helps alleviate environmental pressure but also effectively recovers valuable titanium, tungsten, and vanadium metal resources. In recent years, with the in-depth promotion of the "three reforms" of coal-fired power and the ultra-low emission transformation of coking, steel and cement industries, denitrification catalysts have been more widely used. At the same time, they are also facing more complex operating conditions such as low temperature, high dust and high sulfur, as well as more severe risks of heavy metal poisoning (Fe, As, Pb, etc.), which has significantly increased the content of toxic substances in spent denitrification catalysts. On the other hand, during the regeneration process of denitrification catalysts, inorganic acids are widely used to wash deactivated denitrification catalysts to restore their activity. The acid solution will corrode the iron box of the denitrification catalyst and release water-soluble iron compounds. These iron compounds will further penetrate into the denitrification catalyst, and as the number of regenerations increases, the iron content in the spent denitrification catalyst will also accumulate significantly. This also poses new challenges to the removal of iron and other impurity elements during the recovery of spent denitrification catalysts.

[0003] Conventional denitrification catalyst iron removal processes are primarily categorized into two main categories: physical and chemical methods. Physical methods typically involve magnetic separation, which primarily utilizes the magnetism of iron for separation. Iron can exist in waste denitrification catalysts in two forms: solid, non-acid-soluble magnetic iron, and acid-soluble iron. Even severely poisoned waste denitrification catalysts typically have an iron content in the range of 0.1% to 3% by weight. This iron content range is crucial to the economic value of magnetic separation. It is generally believed that magnetic separation is only meaningful when the raw material iron content exceeds 5% by weight and the magnetic iron content is high. Chemical methods primarily involve pickling, which effectively removes iron impurities but requires precise control of factors such as acid concentration, treatment time, and temperature. Furthermore, pickling produces a large amount of waste acid, along with the loss of other valuable metals, requiring further treatment to avoid environmental pollution. In actual production, conventional physical / chemical cleaning has limited effects on the removal of poisoning elements such as iron, and it is difficult to meet the needs of deep removal of poisoning elements such as iron in specific scenarios, especially for special application scenarios such as coking, steel and cement, and the treatment of waste catalysts with high content of poisoning elements such as iron after multiple regenerations, which in turn affects the quality of the recovered waste catalyst powder.

[0004] Currently, conventional iron removal processes for spent denitrification catalysts include soot blowing, cleaning, grinding, magnetic separation, pickling, and drying. For details, please refer to CN 113458122 A, CN 113546689 A, and CN 108993617 A. However, due to the more severe accumulation of toxic substances and repeated regeneration under complex operating conditions, existing methods may not be able to completely and effectively remove spent denitrification catalysts with high levels of toxic elements such as iron. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problem that the prior art cannot effectively remove iron from waste denitration catalysts with high iron content, and to provide a method for removing iron from waste denitration catalysts and recovering denitration catalyst powder. The method can deeply remove iron from waste denitration catalysts and can significantly restore and increase the specific surface area of ​​the recovered denitration catalyst powder.

[0006] In order to achieve the above object, the first aspect of the present invention provides a method for removing iron from a spent denitration catalyst, the method comprising the following steps:

[0007] (1) Pre-treating the spent denitrification catalyst;

[0008] (2) placing the pretreated spent denitrification catalyst into an acidic solution, mixing it, and then ultrasonically treating it, and then taking it out and drying it;

[0009] (3) ball-milling the solid product obtained in step (2), then mixing the ball-milled product with an alkaline solution to react, followed by solid-liquid separation and washing the solid portion;

[0010] (4) reacting the product obtained in step (3) with a reducing acid solution in a magnetic stirring device, and then separating the solid and liquid and washing and drying the solid portion.

[0011] Preferably, in the spent denitration catalyst of step (1), the content of iron calculated as Fe2O3 is 0.1-3 wt%, the content of silicon calculated as SiO2 is 2.5-9 wt%, and the content of aluminum calculated as Al2O3 is 0.5-4 wt%; and / or

[0012] The specific surface area of ​​the spent denitrification catalyst is 30-50m 2 / g.

[0013] Preferably, in step (1), the pretreatment includes physical cleaning and high-pressure water cleaning.

[0014] Preferably, in step (2), the acid in the acidic solution is selected from one or more of sulfuric acid, hydrochloric acid and phosphoric acid; and / or

[0015] The concentration of the acidic solution is 0.1-2 mol / L.

[0016] Preferably, in step (2), the ultrasonic treatment conditions include: ultrasonic frequency of 10 to 80 kHz, and ultrasonic time of 10 to 30 min.

[0017] Preferably, in step (3), the alkali in the alkaline solution is selected from one or more of sodium hydroxide, ammonia water and ammonium carbonate; and / or

[0018] In step (3), the concentration of the alkaline solution is 1.5 to 3 mol / L; and / or

[0019] In step (3), the solid-liquid ratio of the ball-milled product to the alkaline solution is 1 g: 2-5 mL.

[0020] Preferably, in step (3), the reaction conditions include: temperature of 80-130° C., and time of 1-4 h.

[0021] Preferably, in step (4), the concentration of the reducing acid solution is 0.1 to 2 mol / L; and / or

[0022] The reducing acid in the reducing acid solution is selected from one or more of formic acid, sulfurous acid and oxalic acid; and / or

[0023] The solid-to-liquid ratio of the product obtained in step (3) to the reducing acid solution is 1 g: 4-7 mL.

[0024] Preferably, in step (4), the magnetic stirrer in the magnetic stirring device is a gear-type magnetic stirrer.

[0025] Preferably, in step (4), the reaction conditions include: temperature of 30 to 90° C., and time of 1 to 4 h.

[0026] A second aspect of the present invention provides a recovered denitration catalyst powder prepared by the method described above.

[0027] Preferably, the specific surface area of ​​the recovered denitration catalyst powder is 80 to 95 m 2 / g; and / or

[0028] In the recovered denitration catalyst powder, the iron content calculated as Fe2O3 is ≤50 ppm, the silicon content calculated as SiO2 is ≤1 weight%, and the aluminum content calculated as Al2O3 is ≤0.5 weight%.

[0029] Compared with the prior art, the present invention has at least the following advantages:

[0030] (1) The present invention creatively proposes a method of combining pickling and magnetic adsorption for deep iron removal. A two-step iron removal process is adopted, namely, ultrasonic-assisted pre-iron removal and pickling and stirring combined with magnetic adsorption for deep iron removal. The iron removal efficiency reaches more than 95%, which completely solves the problem of incomplete impurity removal of existing waste denitrification catalysts containing high levels of toxic elements such as iron;

[0031] (2) The present invention achieves significant recovery of the specific surface area of ​​spent denitration catalyst powder while deeply removing iron. The recovered catalyst finally obtained has higher purity and specific surface area and can be directly used to prepare new catalyst powder without further processing.

[0032] (3) The present invention achieves the synergistic removal of impurity elements such as Al and Si in the waste denitrification catalyst powder while deeply removing iron. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of a gear-type magnetic stirring bar.

[0034] Figure 2 This is a real picture of a gear-type magnetic stirring bar. DETAILED DESCRIPTION

[0035] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0036] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0037] The method for removing iron from a waste denitration catalyst provided by the present invention comprises the following steps:

[0038] (1) Pre-treating the spent denitrification catalyst;

[0039] (2) placing the pretreated spent denitration catalyst in an acidic solution for ultrasonic treatment, and then taking it out and drying it;

[0040] (3) ball-milling the solid product obtained in step (2), then mixing the ball-milled product with an alkaline solution to react, followed by solid-liquid separation and washing the solid portion;

[0041] (4) reacting the product obtained in step (3) with a reducing acid solution in a magnetic stirring device, and then separating the solid and liquid and washing and drying the solid portion.

[0042] In the present invention, the spent denitration catalyst contains a large amount of iron, with the iron on the surface of the spent denitration catalyst and in the pores of the spent denitration catalyst existing in the form of ferric oxide and ferrosoferric oxide. Furthermore, the spent denitration catalyst also contains certain silicon and aluminum impurities.

[0043] In a specific embodiment, in the spent denitration catalyst of step (1), the content of iron calculated as Fe2O3 is 0.1-3 wt%, the content of silicon calculated as SiO2 is 2.5-9 wt%, and the content of aluminum calculated as Al2O3 is 0.5-4 wt%.

[0044] In a specific embodiment, the specific surface area of ​​the spent denitration catalyst may be 30-50 m 2 / g.

[0045] In the method of the present invention, the waste denitration catalyst is pretreated, and then the waste denitration catalyst is pickled with ultrasonic wave in a dilute acid solution to remove iron, silicon, aluminum and other impurity elements on the surface of the waste denitration catalyst, thereby completing the pre-iron removal process of the waste denitration catalyst; after ball milling, the ball milling product is reacted with an alkaline solution of a specific concentration under specific conditions, thereby adjusting the pore structure of the waste denitration catalyst, improving the exposure state of iron, making it easier to remove the iron in the pores in the subsequent treatment process, and removing silicon and aluminum impurities at the same time; then the waste denitration catalyst powder is mixed with a reducing acid in a magnetic stirrer for reaction, and the reducing acid can remove the Fe in the pores. 3+ Reduced to acid-soluble Fe 2+ And dissolve and remove under stirring, and can make the unreduced more magnetic Fe 3+ It is adsorbed onto the magnetic stirrer in the suspension, achieving deep removal of iron from the spent denitrification catalyst.

[0046] In the present invention, the pretreatment can be conventional in the art. In a specific embodiment, the pretreatment includes physical cleaning and high-pressure water washing. Physical cleaning of the spent denitrification catalyst can be performed by blowing it with compressed air to remove fly ash attached to the surface. The purpose of high-pressure water washing is to ensure that residues in the pores are completely removed.

[0047] In the present invention, the acidic solution in step (2) can be any conventional choice in the art, as long as it can dissolve the ferroferric oxide and ferroferric dioxide on the surface of the spent denitration catalyst. In a specific embodiment, the acid in the acidic solution can be selected from one or more of sulfuric acid, hydrochloric acid, and phosphoric acid.

[0048] In the present invention, to prevent the loss of V and W in the spent denitration catalyst due to acid dissolution, the concentration of the acidic solution in step (2) should not be too high, and a dilute acid can be used. In a specific embodiment, the concentration of the acidic solution can be 0.1 to 2 mol / L, for example, 0.1 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, or 2 mol / L.

[0049] In the present invention, since the denitration catalyst after pretreatment is in the form of a block, the acidic solution only needs to cover the denitration catalyst, and there is no specific solid-liquid ratio requirement, that is, there is no special restriction on the solid-liquid ratio of the pretreated waste denitration catalyst and the acidic solution in step (2).

[0050] In a specific embodiment, the ultrasonic frequency of the ultrasonic treatment may be 10 to 80 kHz, and the ultrasonic time of the ultrasonic treatment may be 10 to 30 minutes.

[0051] In the present invention, in order to appropriately change the pore structure of the spent denitration catalyst and improve the iron removal rate, in step (3), the concentration of the alkaline solution and the reaction conditions can be controlled within an appropriate range.

[0052] In a specific embodiment, the concentration of the alkaline solution may be 1.5 to 3 mol / L.

[0053] In a specific embodiment, the reaction temperature may be 80 to 130° C., and the reaction time may be 1 to 4 hours.

[0054] In the present invention, the alkali in the alkaline solution can be a conventional choice in the art. In a specific embodiment, the alkali in the alkaline solution is selected from one or more of sodium hydroxide, ammonia water and ammonium carbonate.

[0055] In a preferred embodiment, in order to appropriately change the pore structure of the spent denitration catalyst and improve the iron removal rate, in step (3), the concentration of the alkaline solution can be 1.5 to 3 mol / L.

[0056] In a preferred embodiment, the solid-to-liquid ratio of the ball-milled product to the alkaline solution in step (3) can be 1 g: 2-5 mL.

[0057] In step (3), the solid-liquid separation method is filter pressing; the washing method is water washing. The water washing process is to stir and wash the filter cake obtained by filter pressing in water, and then filter to obtain denitration catalyst powder, wherein the solid-liquid ratio is controlled to be 2-5 ml / g, the water washing temperature is 20-60°C, and the water washing time is 0-30 minutes. The purpose of water washing is to remove the alkaline solution remaining on the surface of the spent denitration catalyst filter cake.

[0058] In the present invention, the reducing acid in the reducing acid solution can be selected from one or more of formic acid, sulfurous acid and oxalic acid, as long as it can reduce Fe in ferroferric oxide and ferric oxide. 3+ That's it.

[0059] In a specific embodiment, the concentration of the reducing acid solution in step (4) can be 0.1 to 2 mol / L.

[0060] In the present invention, in order to improve the iron removal rate, in a preferred embodiment, the solid-liquid ratio of the product obtained in step (3) to the reducing acid solution can be 1 g: 4 to 7 mL.

[0061] In the present invention, in order to increase the amount of magnetic iron adsorbed on the magnetic stirring bar, improve the iron removal rate, and deeply remove the iron in the waste catalyst, in a preferred embodiment, in step (4), the magnetic stirring bar in the magnetic stirring device is as follows Figure 1 and Figure 2A gear-type magnetic stirring bar with a larger surface area is shown.

[0062] In the present invention, in order to improve the removal effect of iron, silicon and aluminum, in a preferred embodiment, the reaction conditions of step (4) include: temperature of 30 to 90° C. and time of 1 to 4 hours.

[0063] The method of the present invention further comprises: mixing the liquid portions obtained after solid-liquid separation in step (2), step (3) and step (4) and recovering V and W to achieve resource recycling. In a specific embodiment, the process is: mixing the liquid portions obtained after solid-liquid separation in step (2), step (3) and step (4), adjusting the pH to 12, so that the Fe impurities in the mixed liquid are precipitated as Fe(OH)3, then adding MgSO4 solution, so that the Si and Al impurities in the mixed liquid are precipitated as MgSiO3 precipitate and Al(OH)3 precipitate, and then filtering and separating the precipitates, with almost no loss of V and W during the impurity removal process; then adjusting the pH value of the impurity-removed solution to 3, and then extracting and stripping the impurity-removed solution to obtain a high-purity vanadium- and tungsten-containing solution, which can achieve resource recycling of 98% of V and 99% of W.

[0064] The second aspect of the present invention provides a recovered denitration catalyst powder prepared by the method described above. The recovered denitration catalyst powder has a large specific surface area and high purity.

[0065] In a specific embodiment, the specific surface area of ​​the recovered denitration catalyst powder is 80 to 95 m 2 / g.

[0066] In a specific embodiment, in the recovered denitration catalyst powder, the iron content calculated as Fe2O3 is ≤50ppm, the silicon content calculated as SiO2 is ≤1wt%, and the aluminum content calculated as Al2O3 is ≤0.5wt%.

[0067] The present invention will be described in detail below through examples, but the scope of protection of the present invention is not limited thereto. In the following examples, the raw materials used are all common commercial products.

[0068] In the following examples, X-ray fluorescence spectrometry (XRF) was used to determine and calculate the content of iron in the spent denitration catalyst as Fe2O3: 2.6 wt %, silicon as SiO2: 6.15 wt %, and aluminum as Al2O3: 3.38 wt %; its specific surface area was 39.27 m 2 / g.

[0069] Example 1

[0070] (1) Physically clean the entire waste denitrification catalyst by blowing it with compressed air to remove fly ash attached to the surface. Subsequently, the physically cleaned waste denitrification catalyst is washed with high-pressure water to ensure that the residue in the pores is completely removed.

[0071] (2) The waste denitrification catalyst after high-pressure water cleaning is placed in a pickling tank to cover the waste denitrification catalyst, and dilute sulfuric acid with a concentration of 0.5 mol / L is added, and ultrasonic assisted pickling is used. The ultrasonic frequency is controlled at 50 kHz and the duration is controlled at 20 min. Then the waste denitrification catalyst is taken out and dried, and the solid part obtained is washed with deionized water to remove iron and other impurity elements such as silicon and aluminum on the surface of the waste denitrification catalyst, thereby completing the pre-iron removal process of the waste denitrification catalyst.

[0072] (3) The waste denitration catalyst after pre-iron removal is put into a ball mill, and water is added in a mass ratio of 2:1 to crush and ball-mill the waste denitration catalyst to obtain a waste denitration catalyst slurry. The obtained waste denitration catalyst slurry is transferred to another reaction container, and a NaOH solution with a concentration of 2 mol / L is added to carry out an alkaline leaching reaction. The solid-liquid ratio of the waste denitration catalyst slurry to the NaOH solution is controlled to be 1 g:5 mL, the reaction temperature is 100 ° C, and the reaction time is 2 h. The pore structure of the waste denitration catalyst slurry is adjusted to improve the exposure state of iron.

[0073] (4) The slurry after the alkali leaching reaction in step (3) is filtered and the filter cake is stirred and washed with water. The solid-liquid ratio of the filter cake to water is 1g:4mL, the washing temperature is 40°C, and the washing time is 20min. The alkali solution remaining on the surface of the waste denitration catalyst filter cake is removed. After filtration, the washed filter cake is mixed with oxalic acid in a magnetic stirrer for reaction. The magnetic stirrer in the magnetic stirrer is a gear-type magnetic stirrer with a large surface area, which can make the magnetic iron in the suspension be adsorbed on the magnetic stirrer while stirring. The acid concentration is 1 mol / L, the reaction time is 2 h, and the reaction temperature is 60 ° C to achieve deep removal of iron in the waste catalyst slurry. The waste denitrification catalyst slurry after acid washing is then filtered and the filter cake is stirred and washed with water. The solid-liquid ratio of the filter cake to water is 1 g:4 mL, the washing temperature is 40 ° C, and the washing time is 20 min to ensure that the filter cake does not contain acid ions. After filtration, the washed filter cake is dried to obtain the final recovered powder, which can be directly used as a preparation of new catalyst powder.

[0074] (5) The liquid portion obtained by solid-liquid separation after acid washing in step (2), the liquid portion obtained by filter pressing the slurry after alkaline leaching reaction in step (3) in step (4), and the liquid portion obtained by filter pressing the waste denitration catalyst slurry after acid washing in step (4) are mixed, and the pH value is adjusted to 12 to precipitate impurities such as Fe in the mixed liquid, and then 20% by mass of MgSO4 solution is added in a ratio of 15:1 by volume of the mixed liquid to the MgSO4 solution to precipitate impurities such as Si and Al in the mixed liquid, and there is almost no loss of V and W during the impurity removal process; after filtration, the pH value of the impurity-removed solution is adjusted to 3, and then the impurity-removed solution is extracted (the extractant is a kerosene solution of TOA trioctylamine and isodecyl alcohol, the TOA volume fraction is 12%, and the isodecyl alcohol volume fraction is 6%) and back-extracted (the back-extraction agent is 1 mol / L NaOH solution) to obtain a high-purity vanadium and tungsten solution. The V and W contents in the solution were measured using an inductively coupled plasma emission spectrometer (ICP), thereby calculating the recovery rate, achieving resource recovery of 98% of V and 99% of W.

[0075] In the embodiment, the recovery rate of V = the content of V in the high-purity vanadium- and tungsten-containing solution / the content of V in the original mixed solution x 100%;

[0076] W recovery rate = W content in high-purity vanadium- and tungsten-containing solution / W content in original mixed solution x 100%;

[0077] The contents of V and W in the original mixed solution are the contents of V and W in the mixed solution after mixing the liquid portion obtained by solid-liquid separation after acid washing in step (2), the liquid portion obtained by filter pressing the slurry after the alkali leaching reaction in step (3) in step (4), and the liquid portion obtained by filter pressing the waste denitration catalyst slurry after acid washing in step (4).

[0078] Example 2

[0079] (1) Physically clean the entire waste denitrification catalyst by blowing it with compressed air to remove fly ash attached to the surface. Subsequently, the physically cleaned waste denitrification catalyst is washed with high-pressure water to ensure that the residue in the pores is completely removed.

[0080] (2) The waste denitrification catalyst after high-pressure water cleaning is placed in a pickling tank to cover the waste denitrification catalyst, and dilute sulfuric acid with a concentration of 2 mol / L is added, and ultrasonic assisted pickling is used. The ultrasonic frequency is controlled at 80 kHz and the duration is controlled at 10 min. The waste denitrification catalyst is then taken out and dried, and the solid part obtained is washed with deionized water to remove iron, silicon, aluminum and other impurity elements on the surface of the waste denitrification catalyst, thereby completing the pre-iron removal process of the waste denitrification catalyst.

[0081] (3) The waste denitration catalyst after pre-iron removal was put into a ball mill, and water was added according to a mass ratio of 2:1 between the waste denitration catalyst and water for crushing and ball milling to obtain a waste denitration catalyst slurry. The obtained waste denitration catalyst slurry was transferred to another reaction container, and a NaOH solution with a concentration of 1.5 mol / L was added for alkaline leaching reaction. The solid-liquid ratio of the waste denitration catalyst slurry to the NaOH solution was controlled to be 1 g:2 mL, the reaction temperature was 120 ° C, and the reaction time was 4 h. The pore structure of the waste denitration catalyst slurry was adjusted to improve the exposure state of iron.

[0082] (4) The slurry after the alkali leaching reaction in step (3) is filtered and the filter cake is stirred and washed with water. The solid-liquid ratio of the filter cake to water is 1g:4mL, the washing temperature is 40°C, and the washing time is 20min. The alkali solution remaining on the surface of the waste denitration catalyst filter cake is removed. After filtration, the washed filter cake is mixed with oxalic acid in a magnetic stirrer for reaction. The magnetic stirrer in the magnetic stirrer is a gear-type magnetic stirrer with a large surface area, which can make the magnetic iron in the suspension be adsorbed on the magnetic stirrer while stirring. Oxalic acid The concentration is 0.5 mol / L, the reaction time is 2 h, and the reaction temperature is 60 ° C to achieve deep removal of iron in the waste catalyst slurry. The waste denitrification catalyst slurry after acid washing is filter-filtered and the filter cake is stirred and washed with water. The solid-liquid ratio of the filter cake to water is 1 g:4 mL, the washing temperature is 40 ° C, and the washing time is 20 min to ensure that the filter cake does not contain acid ions. After filtration, the washed filter cake is dried to obtain the final recovered powder, which can be directly used as a preparation of new catalyst powder.

[0083] (5) The liquid portion obtained by solid-liquid separation after acid washing in step (2), the liquid portion obtained by filter pressing the slurry after alkaline leaching reaction in step (3) in step (4), and the liquid portion obtained by filter pressing the waste denitration catalyst slurry after acid washing in step (4) are mixed, and the pH value is adjusted to 12 to precipitate impurities such as Fe in the mixed liquid, and then 20% by mass of MgSO4 solution is added in a ratio of 15:1 by volume of the mixed liquid to the MgSO4 solution to precipitate impurities such as Si and Al in the mixed liquid, and there is almost no loss of V and W during the impurity removal process; after filtration, the pH value of the impurity-removed solution is adjusted to 3, and then the impurity-removed solution is extracted (the extractant is a kerosene solution of TOA trioctylamine and isodecyl alcohol, the TOA volume fraction is 12%, and the isodecyl alcohol volume fraction is 6%) and back-extracted (the back-extraction agent is 1 mol / L NaOH solution) to obtain a high-purity vanadium and tungsten solution. The V and W contents in the solution were measured using an inductively coupled plasma emission spectrometer (ICP), thereby calculating the recovery rate, achieving resource recovery of 96% of V and 98% of W.

[0084] Example 3

[0085] (1) Physically clean the entire waste denitrification catalyst by blowing it with compressed air to remove fly ash attached to the surface. Subsequently, the physically cleaned waste denitrification catalyst is washed with high-pressure water to ensure that the residue in the pores is completely removed.

[0086] (2) The waste denitrification catalyst after high-pressure water cleaning is placed in a pickling tank to cover the waste denitrification catalyst, and dilute sulfuric acid with a concentration of 1 mol / L is added, and ultrasonic assisted pickling is used. The ultrasonic frequency is controlled at 30 kHz and the duration is controlled at 30 min. The waste denitrification catalyst is then taken out and dried, and the solid part obtained is washed with deionized water to remove iron and other impurity elements such as silicon and aluminum on the surface of the waste denitrification catalyst, thereby completing the pre-iron removal process of the waste denitrification catalyst.

[0087] (3) The waste denitration catalyst after pre-iron removal is put into a ball mill, and water is added according to a mass ratio of 2:1 between the waste denitration catalyst and water for crushing and ball milling to obtain a waste denitration catalyst slurry. The obtained waste denitration catalyst slurry is transferred to another reaction container, and a NaOH solution with a concentration of 3 mol / L is added for alkaline leaching reaction. The solid-liquid ratio of the waste denitration catalyst slurry to the NaOH solution is controlled to be 1 g:4 mL, the reaction temperature is 80 ° C, and the reaction time is 3 h. The pore structure of the waste denitration catalyst slurry is adjusted to improve the exposure state of iron.

[0088] (4) The slurry after the alkali leaching reaction in step (3) is filtered and the filter cake is stirred and washed with water. The solid-liquid ratio of the filter cake to water is 1g:4mL, the washing temperature is 40°C, and the washing time is 20min. The alkali solution remaining on the surface of the waste denitration catalyst filter cake is removed. After filtration, the washed filter cake is mixed with oxalic acid in a magnetic stirrer for reaction. The magnetic stirrer in the magnetic stirrer is a gear-type magnetic stirrer with a large surface area, which can make the magnetic iron in the suspension be adsorbed on the magnetic stirrer while stirring. The acid concentration is 2 mol / L, the reaction time is 2 h, and the reaction temperature is 60 ° C to achieve deep removal of iron in the waste catalyst slurry. The waste denitrification catalyst slurry after acid washing is then filtered and the filter cake is stirred and washed with water. The solid-liquid ratio of the filter cake to water is 1 g:4 mL, the washing temperature is 40 ° C, and the washing time is 20 min to ensure that the filter cake does not contain acid radical ions. After filtration, the washed filter cake is dried to obtain the final recovered powder, which can be directly used as a preparation of new catalyst powder.

[0089] (5) The liquid portion obtained by solid-liquid separation after acid washing in step (2), the liquid portion obtained by filter pressing the slurry after alkaline leaching reaction in step (3) in step (4), and the liquid portion obtained by filter pressing the waste denitration catalyst slurry after acid washing in step (4) are mixed, and the pH value is adjusted to 12 to precipitate impurities such as Fe in the mixed liquid, and then 20% by mass of MgSO4 solution is added in a ratio of 15:1 by volume of the mixed liquid to the MgSO4 solution to precipitate impurities such as Si and Al in the mixed liquid, and there is almost no loss of V and W during the impurity removal process; after filtration, the pH value of the impurity-removed solution is adjusted to 3, and then the impurity-removed solution is extracted (the extractant is a kerosene solution of TOA trioctylamine and isodecyl alcohol, the TOA volume fraction is 12%, and the isodecyl alcohol volume fraction is 6%) and back-extracted (the back-extraction agent is 1 mol / L NaOH solution) to obtain a high-purity vanadium and tungsten solution. The V and W contents in the solution were measured using an inductively coupled plasma emission spectrometer (ICP), thereby calculating the recovery rate, achieving resource recovery of 97% of V and 98% of W.

[0090] Comparative Example 1

[0091] The method of Example 1 is followed, except that no alkali leaching reaction is performed in step (3).

[0092] Specific operations include:

[0093] (1) Physically clean the spent denitrification catalyst by using compressed air to remove fly ash attached to the surface. Subsequently, the physically cleaned spent denitrification catalyst is cleaned with high-pressure water to ensure that the residue in the pores is completely removed.

[0094] (2) The waste denitrification catalyst after high-pressure water cleaning is placed in a pickling tank to cover the waste denitrification catalyst, and dilute sulfuric acid with a concentration of 0.5 mol / L is added, and ultrasonic assisted pickling is used. The ultrasonic frequency is controlled at 50 kHz and the duration is controlled at 20 min. Then the waste denitrification catalyst is taken out and dried, and the solid part obtained is washed with deionized water to remove iron and other impurity elements such as silicon and aluminum on the surface of the waste denitrification catalyst, thereby completing the pre-iron removal process of the waste denitrification catalyst.

[0095] (3) The waste denitration catalyst after pre-deironing is put into a ball mill, and water is added according to a mass ratio of 2:1 between the waste denitration catalyst and water, and the mixture is crushed and ball-milled to obtain a waste denitration catalyst slurry.

[0096] (4) The waste denitration catalyst slurry of step (3) is filtered and the filter cake is stirred and washed with water. The solid-liquid ratio of the filter cake to water is 1g:4mL, the washing temperature is 40°C, and the washing time is 20min. The alkali solution remaining on the surface of the waste denitration catalyst filter cake is removed. After filtration, the washed filter cake is mixed with oxalic acid in a magnetic stirrer for reaction. The magnetic stirrer in the magnetic stirrer is a gear-type magnetic stirrer with a large surface area, which can make the magnetic iron in the suspension be adsorbed on the magnetic stirrer while stirring. The concentration of oxalic acid is 1mol / L, the reaction time is 2h, and the reaction temperature is 60°C. The deep removal of iron in the waste catalyst slurry is achieved. Then, the waste denitration catalyst slurry after acid washing is filtered and the filter cake is stirred and washed with water. The solid-liquid ratio of the filter cake to water is 1g:4mL, the washing temperature is 40°C, and the washing time is 20min to ensure that the filter cake does not contain acid radical ions. After filtration, the washed filter cake is dried to obtain the final recovered powder.

[0097] (5) The liquid portion obtained by solid-liquid separation after acid washing in step (2), the liquid portion obtained by filter pressing the slurry after alkaline leaching reaction in step (3) in step (4), and the liquid portion obtained by filter pressing the waste denitration catalyst slurry after acid washing in step (4) are mixed, and the pH value is adjusted to 12 to precipitate impurities such as Fe in the mixed liquid, and then 20% by mass of MgSO4 solution is added in a ratio of 15:1 by volume of the mixed liquid to the MgSO4 solution to precipitate impurities such as Si and Al in the mixed liquid, and there is almost no loss of V and W during the impurity removal process; after filtration, the pH value of the impurity-removed solution is adjusted to 3, and then the impurity-removed solution is extracted (the extractant is a kerosene solution of TOA trioctylamine and isodecyl alcohol, the TOA volume fraction is 12%, and the isodecyl alcohol volume fraction is 6%) and back-extracted (the back-extraction agent is 1 mol / L NaOH solution) to obtain a high-purity vanadium and tungsten solution. The V and W contents in the solution were measured using an inductively coupled plasma emission spectrometer (ICP), thereby calculating the recovery rate, achieving resource recovery of 93% of V and 95% of W.

[0098] Comparative Example 2

[0099] The method of Example 1 was followed, except that the reaction in step (4) was carried out in a device without magnetic stirring, i.e., the reaction was not stirred.

[0100] Comparative Example 3

[0101] The method of Example 1 was followed, except that in step (4), the reaction temperature was room temperature (25°C).

[0102] Comparative Example 4

[0103] The method of Example 1 was followed, except that in step (4), the reaction time was 0.5 h.

[0104] Test Case

[0105] The iron content (iron as ferric oxide) and the silicon (silicon as silicon dioxide) and aluminum (aluminum as aluminum oxide) in the recovered powders obtained in the examples and comparative examples were tested and calculated using X-ray fluorescence spectrometry (XRF). The results are shown in Table 1.

[0106] Table 1

[0107] Example No. Iron content (ppm) Silicon content (weight %) Aluminum content (weight %) Example 1 50 0.93 0.47 Example 2 70 1.25 0.73 Example 3 85 1.18 0.93 Comparative Example 1 1390 3.97 2.25 Comparative Example 2 1850 1.07 0.93 Comparative Example 3 830 1.98 1.47 Comparative Example 4 970 2.35 1.82

[0108] From the results in Table 1, it can be seen that the iron content in the recovered powder obtained after removing iron from the spent denitration catalyst using the method described in the present invention is significantly reduced, and the silicon and aluminum contents are also low.

[0109] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for removing iron from a spent denitration catalyst, characterized in that: The method comprises the following steps: (1) Pretreatment of spent denitrification catalyst; (2) placing the pretreated spent denitrification catalyst in an acidic solution for ultrasonic treatment, and then taking it out and drying it; (3) ball-milling the solid product obtained in step (2), then mixing the ball-milled product with an alkaline solution to react, followed by solid-liquid separation and washing the solid portion; (4) reacting the product obtained in step (3) with a reducing acid solution in a magnetic stirring device, followed by solid-liquid separation and washing and drying the solid portion, wherein the reaction conditions include: a temperature of 30 to 90° C. and a reaction time of 1 to 4 hours; In step (1), the pretreatment includes physical dust removal and high-pressure water cleaning; In step (4), the magnetic stirrer in the magnetic stirring device is a gear-type magnetic stirrer.

2. The method according to claim 1, characterized in that In the spent denitration catalyst of step (1), the content of iron calculated as Fe2O3 is 0.1-3 wt%, the content of silicon calculated as SiO2 is 2.5-9 wt%, and the content of aluminum calculated as Al2O3 is 0.5-4 wt%; and / or The specific surface area of ​​the spent denitrification catalyst is 30-50m 2 / g.

3. The method according to claim 1 or 2, characterized in that In step (2), the acid in the acidic solution is selected from one or more of sulfuric acid, hydrochloric acid and phosphoric acid; and / or The concentration of the acidic solution is 0.1-2 mol / L.

4. The method according to claim 1 or 2, characterized in that In step (2), the ultrasonic treatment conditions include: ultrasonic frequency of 10-80 kHz, and ultrasonic time of 10-30 min.

5. The method according to claim 1, wherein In step (3), the alkali in the alkaline solution is selected from sodium hydroxide and / or ammonia water; and / or In step (3), the concentration of the alkaline solution is 1.5-3 mol / L; and / or In step (3), the solid-liquid ratio of the ball-milled product to the alkaline solution is 1 g: 2~5 mL.

6. The method according to claim 1, characterized in that In step (3), the reaction conditions include: temperature of 80-130° C. and time of 1-4 h.

7. The method according to claim 1 or 2, characterized in that In step (4), the concentration of the reducing acid solution is 0.1-2 mol / L; and / or The reducing acid in the reducing acid solution is selected from one or more of formic acid, sulfurous acid and oxalic acid; and / or The solid-to-liquid ratio of the product obtained in step (3) to the reducing acid solution is 1 g:4~7 mL.

8. The recovered denitration catalyst powder prepared by the method according to any one of claims 1 to 7.

9. The method for recovering denitration catalyst powder according to claim 8, wherein: The specific surface area of ​​the recovered denitration catalyst powder is 80-95m 2 / g; and / or In the recovered denitration catalyst powder, the iron content calculated as Fe2O3 is ≤50 ppm, the silicon content calculated as SiO2 is ≤1 weight%, and the aluminum content calculated as Al2O3 is ≤0.5 weight%.

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