Process method for synergistically extracting vanadium and tungsten in waste SCR (Selective Catalytic Reduction) denitration catalyst

Abstract

The invention provides a process method for synergistically extracting vanadium and tungsten in a waste SCR (Selective Catalytic Reduction) denitration catalyst. The process method comprises the following steps: (1) carrying out surface purification on the denitration catalyst and then soaking the denitration catalyst in acid liquor; (2) crushing the treated catalyst until D90 is less than or equal to 50 microns; (3) dipping the powder into alkali liquor for reaction, and then adding sodium sulfide and calcium oxide for continuous reaction; (4) separating the alkaline-leached slurry to obtain a filtrate I, adjusting the filtrate to be alkalescent, adding a desiliconizing agent and a selective inhibitor, and separating to obtain a filtrate II; adjusting the filtrate to be weakly acidic, adding diammonium hydrogen phosphate and modified activated carbon loaded nano zero-valent iron for reaction, separating to obtain filtrate III, and performing membrane filtration; (5) performing counter-current extraction on the feed liquid and an extracting agent; and (6) the extraction phase and a back extraction agent are subjected to back extraction, and back extraction liquid containing vanadium and tungsten is obtained. According to the method, the co-extraction risk of impurities is reduced, the formula of the extraction agent is optimized, specific recognition of W and V is enhanced, and generation of interface floccules is eliminated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hazardous waste resource utilization, and particularly relates to a synergistic and efficient extraction method for tungsten and vanadium elements in waste selective catalytic reduction (SCR) de-NOx catalysts of coal-fired power plants, and is particularly suitable for industrialized process methods of waste de-NOx catalysts with significantly increased impurity element contents due to differences in coal types. BACKGROUND

[0002] As the mainstream technology in the field of flue gas de-NOx, selective catalytic reduction (SCR) has been widely used in de-NOx practices in China. Among them, V2O5-WO3 / TiO2 is the most commonly used SCR de-NOx catalyst. In actual operation, due to mechanical wear and tear and blockage caused by ash in coal, as well as the decrease in catalyst activity caused by heavy metals contained in coal, the catalyst needs to be replaced in less than 3 years, and some catalysts are severely deactivated and have large strength damage, and cannot be regenerated and utilized. W and V contained in the catalyst are important industrial raw materials, which are less distributed in nature and expensive, so recycling and reusing waste SCR de-NOx catalysts have important economic and environmental significance.

[0003] The recovery of waste SCR de-NOx catalysts usually adopts high-temperature and high-pressure leaching process to obtain leaching solution rich in W and V. Solvent extraction method has become the mainstream technology in the field of resource recycling of waste de-NOx catalysts due to its advantages of simple operation, high selectivity, excellent separation efficiency, and recyclable extractant. However, due to the diversity of coal types used in coal-fired power plants or the addition of other solid wastes for blending combustion, the impurity element contents in the used waste SCR de-NOx catalysts have significant differences. High-ash, high-sulfur, and high-arsenic coal types will intensify the deposition of ash on the surface of the catalyst, the toxication of heavy metals, and the mechanical wear and tear during the combustion process, resulting in a 3-5-fold increase in the impurity contents of Si, As, and P in the waste de-NOx catalysts compared with conventional samples. In the traditional recovery process, the leached impurity elements will compete with W and V to occupy the organic extraction sites, resulting in a decrease in the amount of organic extraction. With the increase in the recycling times of the extractant, these impurity ions will gradually enrich in the extractant, not only leading to the rapid failure of the extractant, but also causing a large amount of flocculent accumulation at the interface of the organic phase and the aqueous phase, resulting in difficulties in phase separation, a sharp decrease in extraction efficiency, and even the poisoning or failure of the extractant, forcing the production line to stop and clean, and seriously threatening the stability of the continuous production of the industry.

[0004] At present, the industry has significant shortcomings in the treatment of high-impurity waste denitration catalysts: (1) direct mixing or disposal: most manufacturers lack effective impurity removal methods, so they directly crush high-impurity waste denitration catalysts and mix them into new catalyst raw materials, resulting in uneven dispersion of active components of the new catalyst and reduced resistance to poisoning; some enterprises even choose to landfill, causing waste of strategic metal resources and environmental risks; (2) research disconnection: existing laboratory researches mostly use simplified simulated leaching solutions (such as ammonium metavanadate / ammonium paratungstate system), which are significantly different from actual high-impurity industrial leaching solutions; even if some researches use actual waste denitration catalyst leaching solutions, they often ignore the actual impact of flocs on industrial continuous production due to small sample batches, hindering the promotion of industrial application. SUMMARY

[0005] To solve the above-mentioned technical problems, the purpose of the present application is to provide a process method for synergistically and efficiently extracting vanadium and tungsten from waste SCR denitration catalysts.

[0006] To achieve the above-mentioned purposes of the present application, the technical solutions adopted by the present application are as follows:

[0007] The present application provides a process method for synergistically extracting vanadium and tungsten from waste SCR denitration catalysts, comprising the following steps:

[0008] (1) surface purification and pre-impurity removal treatment: after surface purification, the waste SCR denitration catalyst is soaked in an acid solution to remove soluble impurities on the surface of the catalyst;

[0009] (2) fractional crushing: the catalyst after pre-impurity removal treatment is crushed to a particle size D 90 ≤50μm to obtain catalyst powder;

[0010] (3) alkali leaching reaction: the catalyst powder is immersed in an alkali solution for a period of time, and then sodium sulfide and calcium oxide are added and the reaction continues;

[0011] (4) multi-stage deep impurity removal: the slurry after alkali leaching is subjected to solid-liquid separation to obtain filtrate one, the pH value of the obtained filtrate one is adjusted to weak alkaline, a desiliconizing agent and a selective inhibitor are added, and the reaction is carried out for a period of time, then solid-liquid separation is carried out to obtain filtrate two;

[0012] Then, the pH value of the filtrate two is adjusted to weakly acidic, diammonium hydrogen phosphate and modified activated carbon loaded with nano zero-valent iron are added, and the reaction is carried out for a period of time under stirring, then solid-liquid separation is carried out to obtain filtrate three, and the filtrate three is subjected to membrane filtration to remove suspended particles;

[0013] (5) multi-stage countercurrent extraction: the leaching solution after membrane filtration is subjected to countercurrent extraction with a composite extractant to obtain an extraction phase;

[0014] (6) Stripping: the extraction phase obtained in step (5) is subjected to stripping with a stripping agent to obtain a stripping solution containing vanadium and tungsten.

[0015] In some embodiments, in step (1), the surface-cleaned catalyst is immersed in an acid solution at 40-60°C for 30-60 min, and then washed with water;

[0016] Preferably, the acid solution is selected from one or more of citric acid, oxalic acid or sulfuric acid;

[0017] More preferably, the concentration of the acid solution is 0.1-0.5 mol / l.

[0018] In some embodiments, in step (2), the pre-decontamination treated catalyst is first coarsely ground to a particle size D 90 ≤5 mm, and then finely ground after adding a dispersant to a particle size D 90 ≤50 μm.

[0019] Preferably, the dispersant is selected from a polycarboxylate dispersant;

[0020] More preferably, the amount of the dispersant is 0.5-1.0% of the total amount of the catalyst.

[0021] In some embodiments, in step (3), the alkali leaching reaction is carried out at 100-160°C, the alkali solution is selected from one or more of KOH aqueous solution, Na2CO3 aqueous solution or NaOH aqueous solution, and the concentration of the alkali solution is preferably 0.5-4.0 mol / L;

[0022] Preferably, the alkali leaching reaction is carried out with microwave assistance, the power of the microwave assistance is 300-600 W, and the frequency is 2.45 GHz;

[0023] More preferably, the amount of the sodium sulfide is 0.1-0.5 wt% of the weight of the catalyst powder, and the amount of the calcium oxide is 0.5-1.5 wt% of the weight of the catalyst powder.

[0024] In some embodiments, in step (4), a desiliconizing agent and a selective inhibitor are added to the filtrate I, and the mixture is reacted at 40-70°C for 40-120 min; the desiliconizing agent is selected from one or more of 5%-20% magnesium sulfate, calcium chloride or polyaluminum chloride; and the selective inhibitor is selected from polyacrylamide or polyethylene glycol.

[0025] Preferably, the pH value of the filtrate I is adjusted to 8.5-11.0.

[0026] and / or,

[0027] adding diammonium hydrogen phosphate and modified activated carbon supported nano zero-valent iron to the filtrate two, and stirring and reacting at room temperature for 60-90 min, followed by solid-liquid separation, and filtering the obtained filtrate three through a filter membrane with a pore size of 0.2-0.5 μm;

[0028] Preferably, the pH value of the filtrate two is adjusted to 4.5-5.5;

[0029] More preferably, the diammonium hydrogen phosphate is used in an amount of 1-3% of the filtrate two, and the modified activated carbon supported nano zero-valent iron is used in an amount of 0.5-2.0 g / L.

[0030] In some embodiments, in step (5), the composite extractant comprises trioctylamine, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and white oil; wherein the proportion of trioctylamine is 15-20 wt%, and the proportion of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is 3-5 wt%.

[0031] Preferably, the composite extractant is mixed in the following manner:

[0032] a. washing the white oil with 5-10% ammonium carbonate, followed by water washing, for standby;

[0033] b. washing the trioctylamine with acid solution in a mass ratio of 1:1, for standby;

[0034] c. mixing the 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt with the components treated in steps a and b, to obtain a pretreated extractant;

[0035] d. protonating the pretreated extractant obtained in step c with acid solution, to obtain the composite extractant;

[0036] More preferably, in step d, the mass ratio of the pretreated extractant to the acid solution is 1:1, and the protonation time is 5-30 min.

[0037] Further preferably, in step b, the acid solution is selected from a 5-10% sulfuric acid solution, and in step d, the acid solution is selected from a 5-10% sulfuric acid solution, a nitric acid solution or a phosphoric acid solution.

[0038] In some embodiments, the mass ratio of the composite extractant to the filtrate after membrane filtration is 1:5-1:15.

[0039] Preferably, the time of the countercurrent extraction is 5-30 min, and the number of stages is 3-5 stages.

[0040] More preferably, the organic phase obtained after the countercurrent extraction is washed to remove impurity elements mixed in the organic phase; preferably, one or more of desalted water, dilute sulfuric acid or dilute hydrochloric acid is used for washing.

[0041] In some embodiments, in step (6), the stripping is carried out in a stripping tank, and an electric field is applied in the mixing and clarification chamber of the stripping tank to promote the migration of metal ions into the mixing and clarification chamber.

[0042] Preferably, the voltage of the electric field is 5-10 V.

[0043] In some embodiments, the stripping agent is one or more of ammonia, ammonium carbonate or ammonium bicarbonate solution.

[0044] Preferably, the concentration of the stripping agent is 10-20%.

[0045] In some embodiments, in step (6), the organic phase obtained after the stripping is washed and then reused as the extractant in step (5).

[0046] Preferably, the washing includes two-stage countercurrent water washing and acidification with 5% sulfuric acid solution.

[0047] More preferably, after the organic phase is reused for 5-10 times, the acidified organic phase is washed with a washing liquid and then reused as the extractant in step (5), the washing liquid is preferably one or more of sodium carbonate solution, citric acid or peroxide water, and EDTA-2Na solution is added to the washing liquid.

[0048] The technical solution provided by the present application has the following beneficial effects:

[0049] The process method for extracting vanadium and tungsten from waste SCR denitration catalyst provided by the present application constructs a full-process multi-stage impurity removal process, optimizes the extractant formula to enhance the specific recognition of the extractant to W and V, and significantly reduces the co-extraction risk of impurities such as Si and As. The dual regulation mechanism significantly reduces the co-extraction rate of Si and As, and essentially eliminates the generation of interface flocculation, successfully breaking the vicious cycle of "impurity accumulation-flocculation increase-efficiency decay".

[0050] The specific composite extractant formula used in the method of the present application realizes a comprehensive recovery rate of W and V of more than 99% through a multi-stage countercurrent extraction process, and has the following unique advantages:

[0051] (1) Wide adaptability: can process waste denitration catalysts with high content of Si, As and other impurities, avoiding the reduction of resource utilization rate of waste denitration catalysts due to differences in coal types or blending.

[0052] (2) Process intensification: the stripping solution is directly used for catalyst preparation, saving the purification process.

[0053] (3) Cost advantage: The loss of extractant is greatly reduced, the continuous operation cycle of the production line is prolonged, and the shutdown loss is avoided.

[0054] The method breaks through the adaptation barrier between the laboratory simulation system and the actual industrial system, realizes an engineering leap through chemical system innovation under the premise of maintaining the traditional equipment architecture, and realizes a leap in key indicators such as recovery efficiency, operation stability and economy compared with the traditional process, thereby providing a new solution for resource treatment of waste SCR denitration catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 An embodiment of a process flow for extracting vanadium and tungsten from waste SCR denitration catalyst is shown. DETAILED DESCRIPTION

[0056] The specific embodiments of the present application will be described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The term "and / or" as can be used herein includes any and all combinations of one or more of the associated listed items.

[0058] The present application provides a process for synergistically extracting vanadium and tungsten from waste SCR denitration catalyst, as shown in Figure 1 , comprising the following steps:

[0059] (1) Surface purification and pre-decontamination treatment: compressed air is used to remove fly ash on the surface of the waste SCR denitration catalyst, and ultrasonic assisted pre-cleaning is simultaneously performed, the frequency of ultrasonic cleaning is 40-60 kHz, and the power is 500-1000 W; then acid solution is used to remove part of the soluble impurities (Si, As, etc.) in the waste SCR denitration catalyst, the reaction temperature is 40-60℃, the time is 30-60 min, and then high-pressure water (pressure ≥ 5 MPa) can be used to flush the residual acid solution and soluble impurities in the pores;

[0060] (2) Grading crushing: the washed catalyst is crushed to a particle size D 90 ≤50μm, to obtain catalyst powder;

[0061] (3) Alkali leaching reaction: after the catalyst powder is immersed in alkali solution for a period of time, sodium sulfide and calcium oxide are added and the reaction continues;

[0062] (4) Multi-stage deep impurity removal: the slurry after alkaline leaching is subjected to solid-liquid separation to obtain filtrate one, the pH value of the obtained filtrate one is adjusted to weak alkaline, then a desilication agent and a selective inhibitor are added, and after a period of reaction, solid-liquid separation is performed to obtain filtrate two;

[0063] Then, the pH value of the filtrate two is adjusted to weak acid, and diammonium hydrogen phosphate and modified activated carbon loaded nano zero-valent iron are added thereto, and after a period of reaction under stirring, solid-liquid separation is performed to obtain filtrate three, and the filtrate three is subjected to membrane filtration to remove suspended particles;

[0064] (5) Multi-stage countercurrent extraction: the filtrate after membrane filtration is subjected to countercurrent extraction with a composite extractant to obtain an extraction phase;

[0065] (6) Stripping: the extraction phase obtained in step (5) is subjected to stripping with a stripping agent to obtain a stripping solution containing vanadium and tungsten.

[0066] In the specific embodiment of the process method of the present application, the acid solution in step (1) can be selected from one or more of citric acid, oxalic acid or sulfuric acid; the concentration of the acid solution used can be 0.1-0.5 mol / l, such as 0.2 mol / l, 0.3 mol / l, 0.4 mol / l.

[0067] In some specific embodiments, in step (2), the washed catalyst is first coarsely crushed to a particle size D 90 ≤5 mm by a jaw crusher, then transferred to a ball mill for fine grinding, and a dispersing agent is added thereto for fine grinding, until the particle size D 90 ≤50 μm of the catalyst, thereby reducing energy consumption and improving the uniformity of the slurry. Specifically, the dispersing agent can be selected from polycarboxylate dispersing agent, and the addition amount is 0.5-1.0% of the total amount of the catalyst, such as 0.6%, 0.7%, 0.8%, 0.9%.

[0068] In some specific embodiments, based on the weight of the catalyst powder, in step (3), 0.5-4.0 mol / L of one or more of KOH, Na2CO3 or NaOH solution can be selected as the leaching solution, the solid-liquid ratio (catalyst powder / alkali solution) is controlled to be 5-30 mL / g, such as 10 mL / g, 15 mL / g, 20 mL / g, 25 mL / g, and the alkaline leaching reaction temperature is 100-160°C, such as 110°C, 120°C, 130°C, 140°C, 150°C. After a period of reaction, 0.1-0.5 wt% of sodium sulfide is added to the catalyst powder as an arsenic complexing precipitant to solidify the arsenic element in the powder to form AsS precipitate; at the same time, 0.5-1.5 wt% of calcium oxide is introduced to react with the silicate (SiO3 2- ) in the powder to generate CaSiO3 precipitate to remove silicon element.

[0069] Preferably, the alkali leaching reaction can be carried out under microwave-assisted conditions (power of 300-600 W, frequency of 2.45 GHz), which can shorten the time of the alkali leaching reaction by 1-2 h and increase the leaching rate of vanadium and tungsten to more than 95%.

[0070] In step (4) of the process method of the present application, the leaching solution after alkali leaching is subjected to solid-liquid separation, such as filter pressing, to separate the residue and collect the filtrate, and the filtrate is subjected to multi-stage deep impurity removal. Specifically, after adjusting the pH value of the filtrate to weak alkaline (8.5-11.0), a desiliconizing agent (one or more of 5-20% magnesium sulfate, calcium chloride or polyaluminum chloride (PAC)) is added to remove silicon, and a selective inhibitor (one or more of 1-5% polyacrylamide (PAM) or polyethylene glycol (PEG)) is added to reduce the adsorption of vanadium and tungsten during the silicon removal process. The reaction is carried out at 40-70°C for 40-120 min. After the reaction is completed, the temperature of the solution is increased by 10-30°C again, and then solid-liquid separation (such as filter pressing) is immediately started to obtain filtrate two.

[0071] In some specific embodiments, the pH value of the obtained filtrate two is adjusted to weakly acidic (4.5-5.5), 1-3% diammonium hydrogen phosphate ((NH4)2HPO4) is added to form AlPO4-FePO4 complex precipitate with Al and Fe, achieving deep removal of Al and Fe; at the same time, modified activated carbon loaded with nano zero-valent iron (the dosage is 0.5-2.0 g / L relative to the filtrate two) is added to selectively adsorb As and P, achieving deep removal of As and P. After stirring for a period of time, solid-liquid separation is performed to obtain filtrate three.

[0072] In some embodiments, the above-mentioned filtrate three is further subjected to membrane filtration to remove suspended particles before entering the extraction. Specifically, the pore size of the filtration membrane is 0.2-0.5 μm.

[0073] In step (5) of the process method of the present application, the formula of the composite extractant is trioctylamine, 1-butyl-3-methylimidazolium bis-trifluoromethanesulfonimide salt and white oil; wherein the proportion of trioctylamine is 15-20 wt%, and the proportion of 1-butyl-3-methylimidazolium bis-trifluoromethanesulfonimide salt is 3-5 wt%.

[0074] In some preferred embodiments, the composite extractant mentioned in the present application is mixed in the following way:

[0075] a. The white oil is washed with 5-10% ammonium carbonate and then washed with water for standby;

[0076] b. The trioctylamine is acid-washed with an acid solution in a mass ratio of 1:1 for standby;

[0077] c. mixing 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide salt with the components treated in steps a and b to obtain a pretreated extractant;

[0078] d. obtaining the composite extractant by protonating the pretreated extractant obtained in step c with an acid solution;

[0079] In some specific embodiments, the acid solution in step b is selected from a 5-10% sulfuric acid solution, and the acid solution in step d is selected from a 5-10% sulfuric acid solution, a nitric acid solution or a phosphoric acid solution.

[0080] In step c, the proportion of trioctyl tertiary amine is 15-20 wt%, the proportion of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide salt is 3-5 wt%, and the rest is white oil.

[0081] In step d, the mass ratio of the pretreated extractant to the acid solution is 1:1, and the protonation time is 5-30 min.

[0082] In some embodiments, the mass ratio of the composite extractant to the filtrate after membrane filtration is 1:5-1:15, the countercurrent extraction time is 5-30 min, the number of stages is 3-5, the obtained extraction phase after countercurrent extraction is washed to remove impurity elements mixed in the organic phase, and one or more of desalted water, dilute sulfuric acid or dilute hydrochloric acid is preferably used for washing.

[0083] In step (6) of the process of the present application, the stripping is carried out in a stripping tank, and the stripping operation is generally carried out in the stripping tank, which is a conventional technique in the art. Specifically, the organic phase and the stripping agent first enter the mixing chamber of the stripping tank, fully contact and mass transfer under the action of stirring, and then overflow into the mixing and clarification chamber for standing and layering. In the present application, an electric field is applied in the mixing and clarification chamber of the stripping tank during the stripping process to promote the migration of metal ions into the mixing and clarification chamber. Preferably, the voltage of the applied electric field is 5-10 V. In some specific embodiments, a pair of parallel electrodes is symmetrically arranged at the bottom or top of the mixing and clarification chamber of the stripping tank, so that the electrodes are in full contact with the liquid to promote the migration of metal ions in the solution. The cathode is placed on the side of the organic phase, and the anode is placed near the stripping agent area. Specifically, a graphite anode and a stainless steel cathode can be used.

[0084] In some specific embodiments, the stripping agent is one or more of ammonia water, ammonium carbonate solution or ammonium bicarbonate solution. Preferably, the concentration of the stripping agent is 10-20%.

[0085] In some embodiments, in step (6) of the process of the present application, the organic phase obtained after stripping is subjected to 2-stage countercurrent water washing and 5% sulfuric acid acidification, and then reused as the extractant in step (5); in order to further remove the enriched impurity elements, after the extractant is reused for 5-10 times, a deep washing is performed, that is, one or more of 5%-10% sodium carbonate solution, 2%-10% citric acid or 3%-10% H2O2 is used as the washing agent, and 0.5%-1% EDTA-2Na solution is added to the washing liquid, and then the washing liquid is reused as the extractant.

[0086] The present application will be further described in the following specific examples, but should not be understood as being limited to the present application.

[0087] In the examples, if the specific experimental steps or conditions are not specified, the corresponding conventional experimental steps or conditions can be used. If the reagents used are not specified by the manufacturer, they are all conventional reagents in the field.

[0088] The content of each element in the feed liquid was tested in the following manner:

[0089] The V and W elements were detected according to the method of GB / T 14352-2010 Chemical Analysis Method for Tungsten Ore and Molybdenum Ore.

[0090] The Na, K, Fe and As elements were detected according to the method of GB / T 34701-2017 Analysis Method for Trace Elements of Regenerated Flue Gas Denitration Catalyst.

[0091] The Si and Al elements were detected according to the method of GB / T 30902-2014 Determination of Impurity Elements in Inorganic Chemical Products by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES).

[0092] The composite extractants used in the following examples were prepared by mixing the following components:

[0093] a. The white oil was washed with 5-10% ammonium carbonate and then washed with water, and was ready for use;

[0094] b. The trioctyl tertiary amine was acid-washed with 5-10% sulfuric acid solution at a mass ratio of 1:1, and was ready for use;

[0095] c. The 1-butyl-3-methyl imidazole bis-trifluoromethanesulfonimide salt was mixed with the components treated by steps a and b to obtain a pretreated extractant;

[0096] d. The pretreated extractant obtained in step c was protonated with an acid solution (mass ratio of 1:1, 5% sulfuric acid solution) for 5 min to obtain a composite extractant.

[0097] Example 1

[0098] (1) Surface cleaning and pre-decontamination treatment: The waste SCR denitration catalyst is blown with compressed air to remove the fly ash attached to the surface, and then the waste SCR denitration catalyst after physical dust removal is pre-cleaned with ultrasonic waves at 40 kHz and 1000 W to ensure that the residues in the catalyst pores are thoroughly removed;

[0099] The cleaned waste denitration catalyst is placed in an acid washing tank to submerge the catalyst, 0.5 mol / L citric acid is added, heated to 50°C, and soaked for 30 min to remove arsenic and other impurity elements such as silicon and aluminum on the surface of the waste SCR denitration catalyst, completing the pre-decontamination process of the waste denitration catalyst, and then the residual acid and soluble impurities in the pores are washed with high-pressure water;

[0100] (2) Grading crushing: The washed waste SCR denitration catalyst is coarsely crushed to a particle size D 90 = 5 mm by a jaw crusher, then transferred to a ball mill and added with 1.0% polycarboxylate dispersant for fine grinding to a particle size D 90 = 40 μm, obtaining catalyst powder;

[0101] (3) Alkali leaching reaction: The ball-milled catalyst powder is transferred to a high-pressure reaction kettle, 4.0 mol / L NaOH solution is added, the solid-liquid ratio is controlled at 20 mL / g, heated to 120°C, and then 0.5wt% sodium sulfide and 1.0wt% calcium oxide are added to the slurry, and a microwave generator is started to assist the reaction (600 W, 2.45 GHz) for 2 h;

[0102] (4) Multi-stage deep decontamination: The slurry after alkali leaching is pressure-filtered to obtain a filtrate, which is again transferred to a reaction kettle to adjust the pH to 10.0, and 10% polyaluminum chloride (PAC) and 5% polyacrylamide (PAM) are added, and the reaction is carried out at 60°C for 60 min. After the reaction is completed, the material liquid is again heated to 80°C, and then pressure filtration is carried out to obtain a second filtrate;

[0103] Then, the second filtrate is again transferred to a reaction kettle to adjust the pH to 4.5, 1% diammonium hydrogen phosphate and 2.0 g / L modified activated carbon supported nano zero-valent iron are added, and stirred at room temperature for 60 min, and then pressure filtration is carried out again to obtain a third filtrate, which is filtered through a 0.2 μm membrane and then enters an extraction tank;

[0104] (5) Multi-stage countercurrent extraction: a composite extractant is prepared by mixing 18% trioctylamine, 3% 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imidate salt, and 79% white oil;

[0105] The countercurrent extraction is performed with the ratio of extractant to filtrated feed liquid (O / A) being 1:10, the extraction time being 5 min, and the extraction stage being 3-stage countercurrent extraction; the obtained extraction phase after the countercurrent extraction is washed with the ratio of organic phase to 0.1 mol / l dilute sulfuric acid (O / A) being 1:1;

[0106] (6) Stripping: single-stage stripping is performed with 12% ammonia water as a stripping agent, O / A ratio being 2:1, and stripping time being 5 min, and at the same time, a direct current voltage of 5 V is applied to the mixing and clarifying chamber of the stripping tank, to obtain a stripping liquid containing vanadium and tungsten and an organic phase after stripping; the stripping liquid can be directly used to prepare a new denitration catalyst or produce vanadium oxide (V2O5) or tungsten oxide (WO3) through further purification.

[0107] The organic phase after stripping is subjected to two-stage countercurrent water washing and acidification with 5% sulfuric acid solution and then reused as an extractant to the multi-stage countercurrent extraction of step (5).

[0108] It is detected that the recovery rate of vanadium is 99.25%, and the recovery rate of tungsten is 99.34%.

[0109] According to the above process, after the extractant is reused for 5 times, the organic phase after acidification and stripping is subjected to one deep washing, and the washing agent is 5% sodium carbonate solution, and at the same time, 0.5% EDTA-2Na solution is added to the washing liquid. It is detected that after the extractant is reused for 5 times, the recovery rate of vanadium is still maintained at 99.03%, and the recovery rate of tungsten is 99.12%.

[0110] Example 2

[0111] (1) Surface purification and pre-decontamination treatment: compressed air is used to blow the waste SCR denitration catalyst to remove the fly ash attached to the surface, and then the waste SCR denitration catalyst after physical dust removal is subjected to ultrasonic assisted pre-cleaning at 50 kHz and 800 W, to ensure that the residues in the pores of the catalyst are completely removed;

[0112] The cleaned waste denitration catalyst is put into an acid washing tank to immerse the catalyst, 0.3 mol / L oxalic acid is added, heated to 45℃, and the soaking time is controlled at 50 min, to remove arsenic and other impurity elements such as silicon and aluminum on the surface of the waste SCR denitration catalyst, and complete the pre-decontamination treatment process of the waste denitration catalyst, and then high-pressure water is used to direct flush the residual acid liquid and soluble impurities in the pores;

[0113] (2) Grading crushing: the flushed waste SCR denitration catalyst is coarsely crushed to a particle size D 90 = 4 mm by a jaw crusher, and then transferred to a ball mill and added with 0.7% polycarboxylate dispersant for fine grinding to a particle size D 90 = 45 μm, to obtain catalyst powder;

[0114] (3) Alkali leaching reaction: After ball milling, the catalyst powder was transferred to a high-pressure reaction kettle, 4.0 mol / L KOH solution was added, and the solid-liquid ratio was controlled at 15 mL / g. After heating to 140°C, 0.3wt% sodium sulfide and 1.2wt% calcium oxide were added to the slurry, and a microwave generator was started to assist the reaction (600W, 2.45GHz). The slurry was kept at 140°C for 1.5h;

[0115] (4) Multi-stage deep impurity removal: The slurry after alkali leaching was pressure filtered to obtain a filtrate. The filtrate was transferred to a reaction kettle again to adjust the pH to 9.0, 13% magnesium sulfate and 3% polyacrylamide (PAM) were added, and the reaction was carried out at 50°C for 90min. After the reaction, the slurry was heated to 80°C again, and then pressure filtration was carried out to obtain a second filtrate;

[0116] Then, the second filtrate was transferred to a reaction kettle again to adjust the pH to 5.0, 2% diammonium hydrogen phosphate and 1.5g / L modified activated carbon supported nano zero-valent iron were added, and the slurry was stirred at room temperature for 60min. Then, pressure filtration was carried out again to obtain a third filtrate, which was filtered through a 0.2μm membrane and then entered an extraction tank;

[0117] (5) Multi-stage countercurrent extraction: A composite extractant was prepared by mixing 16% trioctylamine, 4% 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imidate salt, and 80% white oil according to the ratio;

[0118] The extractant and the membrane-filtered slurry (O / A) were mixed at a ratio of 1:8 for countercurrent extraction, the extraction time was 5min, and the extraction series was 3-stage countercurrent extraction. The organic phase obtained after countercurrent extraction was washed with an organic phase / 0.05mol / l hydrochloric acid (O / A) ratio of 1:1;

[0119] (6) Stripping: 15% ammonium carbonate was used as a stripping agent for single-stage stripping, O / A ratio was 1.5:1, and stripping time was 10min. At the same time, a direct current voltage of 8V was applied to the mixing chamber of the stripping tank to obtain a stripping solution containing vanadium and tungsten and an organic phase after stripping. The stripping solution can be directly used to prepare new denitration catalysts or further purified to produce vanadium oxide (V2O5) or tungsten oxide (WO3).

[0120] The organic phase after stripping was subjected to two-stage countercurrent water washing and acidification with 5% sulfuric acid solution, and then reused as an extractant in step (5) for multi-stage countercurrent extraction.

[0121] After detection, the recovery rate of vanadium was 99.13%, and the recovery rate of tungsten was 99.21%.

[0122] According to the above process, the acidified back-extracted organic phase is subjected to one deep washing after the extractant is reused for 5 times, the washing agent is 5% H2O2, and 0.8% EDTA-2Na solution is added in the washing liquid. After detection, the recovery rate of vanadium is still maintained at 99.07% and the recovery rate of tungsten is 99.15% after the extractant is reused for 5 times.

[0123] Example 3

[0124] (1) Surface cleaning and pre-decontamination treatment: compressed air is used to blow the waste SCR denitration catalyst to remove the fly ash attached to the surface, and then the waste SCR denitration catalyst after physical dust removal is pre-cleaned with ultrasonic waves at 40 kHz and 1000 W to ensure that the residues in the catalyst pores are thoroughly removed;

[0125] The cleaned waste denitration catalyst is placed in an acid washing tank to immerse the catalyst, 0.2 mol / L sulfuric acid is added, heated to 55°C, and soaked for 50 min to remove arsenic and other impurity elements such as silicon and aluminum on the surface of the waste SCR denitration catalyst, and the pre-decontamination process of the waste denitration catalyst is completed, and then high-pressure water is used to direct flush the residual acid and soluble impurities in the pores;

[0126] (2) Grading crushing: the washed waste SCR denitration catalyst is coarsely crushed to a particle size D 90 = 3 mm by a jaw crusher, then transferred to a ball mill and added with 0.5% polycarboxylate dispersant for fine grinding to a particle size D 90 = 30 μm, to obtain catalyst powder;

[0127] (3) Alkali leaching reaction: the ball-milled catalyst powder is transferred to a high-pressure reaction kettle, 3.0 mol / L Na2CO3 solution is added, the solid-liquid ratio is controlled at 25 mL / g, heated to 160°C, and then 0.4 wt% sodium sulfide and 0.8 wt% calcium oxide are added in the slurry, and a microwave generator is started to assist the reaction (600 W, 2.45 GHz) for 2 h;

[0128] (4) Multi-stage deep decontamination: the slurry after alkali leaching is pressure-filtered to obtain filtrate one, which is again transferred to a reaction kettle to adjust pH = 10.5, 10% polyaluminum chloride (PAC) and 5% polyacrylamide (PAM) are added, and the reaction is carried out at 70°C for 40 min, after the reaction is completed, the material liquid is again heated to 80°C, and then pressure filtration is carried out to obtain filtrate two;

[0129] Then, the obtained filtrate two is again transferred to a reaction kettle to adjust pH = 5.5, 3% diammonium hydrogen phosphate and 0.8 g / L modified activated carbon supported nano zero-valent iron are added, stirred at room temperature for 60 min, and then pressure filtration is carried out again to obtain filtrate three, which is filtered through a 0.2 μm membrane and then enters an extraction tank;

[0130] (5) Multi-stage countercurrent extraction: according to the ratio of 19% trioctyl tertiary amine, 5% 1-butyl-3-methyl imidazole bis-trifluoromethanesulfonimide salt and 76% white oil, a composite extractant is prepared;

[0131] The countercurrent extraction is carried out with the ratio of extractant to membrane filtered feed liquid (O / A) being 1:10, the extraction time being 5 min and the extraction stage being 3-stage countercurrent extraction; the obtained extraction phase after countercurrent extraction is washed with the ratio of organic phase to 0.1 mol / l dilute sulfuric acid (O / A) being 1:1;

[0132] (6) Stripping: single-stage stripping is carried out with 10% ammonium carbonate as a stripping agent, the O / A ratio being 1:1 and the stripping time being 5 min, and at the same time, a direct current voltage of 10V is applied to the mixing and clarifying chamber of the stripping tank, to obtain a stripping liquid containing vanadium and tungsten and an organic phase after stripping; the stripping liquid can be directly used to prepare a new denitration catalyst or produce vanadium oxide (V2O5) or tungsten oxide (WO3) through further purification.

[0133] The organic phase after stripping is subjected to two-stage countercurrent water washing and acidification with 5% sulfuric acid solution and then reused as an extractant in the multi-stage countercurrent extraction of step (5).

[0134] It is detected that the final vanadium recovery rate is 99.05% and the tungsten recovery rate is 99.07%.

[0135] According to the above process, the organic phase after acidification after stripping is subjected to one deep washing after being reused for 5 times, the washing agent being 2% citric acid and 3% H2O2, and at the same time, 0.6% EDTA-2Na solution is added to the washing liquid. It is detected that after being reused for 5 times, the vanadium recovery rate of the extractant still remains at 99.01% and the tungsten recovery rate is 99.03%.

[0136] Example 4

[0137] (1) Surface purification and pre-decontamination treatment: compressed air is used to blow the waste SCR denitration catalyst to remove the fly ash attached to the surface, and then the waste SCR denitration catalyst after physical dust removal is subjected to ultrasonic assisted pre-cleaning at 40 kHz and 1000W to ensure that the residues in the pores of the catalyst are completely removed;

[0138] The cleaned waste denitration catalyst is put into an acid washing tank to immerse the catalyst, a mixed solution of 0.1 mol / L sulfuric acid and 0.1 mol / L oxalic acid (2:1) is added, heated to 60℃, and the soaking time is controlled at 30 min, to remove arsenic and other impurity elements such as silicon and aluminum on the surface of the waste SCR denitration catalyst, complete the pre-decontamination treatment process of the waste denitration catalyst, and then the high-pressure water is used to direct flush the residual acid liquid and soluble impurities in the pores.

[0139] (2) Stage crushing: the washed waste SCR denitration catalyst is coarsely crushed to a particle size D 90 = 5 mm by a jaw crusher, and then transferred to a ball mill and finely ground to a particle size D 90 = 35 μm by adding 0.8% polycarboxylate dispersant, to obtain catalyst powder;

[0140] (3) Alkali leaching reaction: the ball-milled catalyst powder is transferred to a high-pressure reaction kettle, 4.0 mol / L NaOH solution is added, the solid-liquid ratio is controlled to be 22 mL / g, the temperature is raised to 150°C, 0.5 wt% sodium sulfide and 1.0 wt% calcium oxide are added in the slurry, a microwave generator is started to assist the reaction (600 W, 2.45 GHz), and the temperature is kept for 1.5 h;

[0141] (4) Multi-stage deep impurity removal: the slurry after alkali leaching is pressure-filtered to obtain filtrate one, which is transferred again to the reaction kettle to adjust the pH to 11.0, 10% polyaluminum chloride (PAC) and 2% polyacrylamide (PAM) are added, and the reaction is carried out at 60°C for 80 min; after the reaction, the temperature of the material liquid is raised to 80°C, and then pressure filtration is immediately carried out to obtain filtrate two;

[0142] Then, the obtained filtrate two is transferred again to the reaction kettle to adjust the pH to 4.5, 2.5% diammonium hydrogen phosphate and 2.0 g / L modified activated carbon supported nano zero-valent iron are added, stirring is carried out at room temperature for 60 min, pressure filtration is carried out again to obtain filtrate three, which is filtered through a 0.2 μm membrane and then enters an extraction tank;

[0143] (5) Multi-stage countercurrent extraction: a composite extractant is prepared by mixing 20% trioctylamine, 5% 1-butyl-3-methylimidazolium bistrifluoromethanesulfonimide, and 75% white oil;

[0144] Countercurrent extraction is carried out with the extractant and the membrane-filtered material liquid (O / A) ratio being 1:5, the extraction time being 5 min, and the extraction stage being 5-stage countercurrent extraction; the organic phase / 0.2 mol / L hydrochloric acid (O / A) ratio of the obtained extraction phase after countercurrent extraction is 1:1 for washing;

[0145] (6) Stripping: 12% ammonia water is used as a stripping agent for single-stage stripping, the O / A ratio is 2:1, the stripping time is 5 min, a 7V direct current voltage is applied to the mixing and clarification chamber of the stripping tank, and the stripping liquid containing vanadium and tungsten and the organic phase after stripping are obtained; the stripping liquid can be directly used for preparing new denitration catalysts or producing vanadium oxide (V2O5) or tungsten oxide (WO3) through further purification.

[0146] After back extraction, the organic phase is subjected to two-stage countercurrent water washing and acidified with 5% sulfuric acid solution and then reused as an extractant to the multi-stage countercurrent extraction in step (5).

[0147] After testing, the recovery rate of vanadium was 99.17% and the recovery rate of tungsten was 99.32%.

[0148] Following the above process, the acidified, stripped organic phase was subjected to a deep wash using 2% citric acid and 3% H₂O₂ after the extractant was reused five times. A 0.6% EDTA-2Na solution was also added to the wash solution. Testing showed that even after the extractant was reused five times, the vanadium recovery rate remained at 99.01%, and the tungsten recovery rate remained at 99.03%.

[0149] Comparative Example 1

[0150] The process is carried out with reference to the process of Example 1, except that in step (3), sodium sulfide and calcium oxide are not added during the alkali leaching process.

[0151] After testing, the recovery rate of vanadium was 92.96%, and the recovery rate of tungsten was 85.10%.

[0152] Comparative Example 2

[0153] The process is carried out in accordance with the process of Example 1, except that the multi-stage deep impurity removal process in step (4) is not carried out.

[0154] After testing, the recovery rate of vanadium was 24.41% and the recovery rate of tungsten was 31.55%.

[0155] Comparative Example 3

[0156] The process was carried out in accordance with the process of Example 1, except that during step (4), the pH of the slurry after alkali leaching was directly adjusted to 4.5, 1% diammonium hydrogen phosphate and 2.0 g / L modified activated carbon-loaded nano-zero-valent iron were added, and after stirring at room temperature for 60 minutes, the filtrate was filtered again to obtain filtrate 3, which was then filtered through a 0.2 μm membrane and then entered the extraction tank.

[0157] After testing, the recovery rate of vanadium was 79.69% and the recovery rate of tungsten was 62.75%.

[0158] In the above example, the contents of metal elements in the slurry obtained at each stage are shown in Table 1 below:

[0159] Table 1

[0160]

[0161]

[0162]

[0163] Note: " / " in the table means that the corresponding data of the element is not tested.

[0164] From the data in Table 1 above, it can be seen that the present application uses a composite extractant formula to realize a comprehensive recovery rate of vanadium and tungsten of more than 99% through a multi-stage countercurrent extraction process; and after a multi-stage deep impurity removal step, the content of impurities such as As and Si in the feed liquid has been greatly reduced, significantly reducing the co-extraction rate of multiple impurities, and essentially eliminating the generation of interface flocculation.

Claims

1. A process for the synergistic extraction of vanadium and tungsten from spent SCR denitration catalysts, characterized in that: The following steps are involved: (1) Surface purification and pre-denitration treatment: After surface purification, the spent SCR denitration catalyst is immersed in acid solution to remove soluble impurities on the catalyst surface; (2) Gradual crushing: crush the pre-decontaminated catalyst to a particle size of D 90 ≤50μm, and catalyst powder is obtained; (3) Alkali leaching reaction: the catalyst powder is immersed in alkaline solution for a period of time, and then sodium sulfide and calcium oxide are added thereto and the reaction is continued; (4) Multi-stage deep impurity removal: The slurry after alkali leaching is subjected to solid-liquid separation to obtain filtrate 1, the pH value of the obtained filtrate 1 is adjusted to weak alkalinity, and then a desiliconizing agent and a selective inhibitor are added. After a period of reaction, solid-liquid separation is performed to obtain filtrate 2; Then, the pH value of the filtrate 2 is adjusted to be weakly acidic, diammonium hydrogen phosphate and modified activated carbon-supported nano-zero-valent iron are added thereto, and the mixture is stirred and reacted for a period of time, followed by solid-liquid separation to obtain a filtrate 3, and the filtrate 3 is filtered through a membrane to remove suspended particles; (5) Multi-stage countercurrent extraction: The feed liquid after membrane filtration is subjected to countercurrent extraction with a composite extractant to obtain an extract phase; (6) Back extraction: The extract phase obtained in step (5) is back extracted with a back extractant to obtain a back extract containing vanadium and tungsten.

2. The process according to claim 1, characterized in that: In step (1), the surface-cleaned catalyst is placed in an acid solution, soaked at 40-60° C. for 30-60 minutes, and then rinsed with water; Preferably, the acid solution is selected from one or more of citric acid, oxalic acid or sulfuric acid; More preferably, the concentration of the acid solution is 0.1 to 0.5 mol / l.

3. The process according to claim 2, characterized in that: In step (2), the catalyst after pre-decontamination treatment is first coarsely crushed to a particle size D 90 ≤5mm, then add dispersant and grind to the catalyst particle size D 90 ≤50μm; Preferably, the dispersant is selected from polycarboxylate dispersants; More preferably, the amount of the dispersant used is 0.5-1.0% of the total amount of the catalyst.

4. The process according to claim 3, characterized in that: In step (3), the alkali leaching reaction is carried out at 100-160° C., the alkali solution is selected from one or more of a KOH aqueous solution, a Na 2 CO 3 aqueous solution or a NaOH aqueous solution, and the concentration of the alkali solution is preferably 0.5-4.0 mol / L; Preferably, the alkali leaching reaction is carried out under microwave assistance, the microwave assistance power is 300-600W, and the frequency is 2.45GHz; More preferably, the amount of sodium sulfide used is 0.1-0.5 wt% of the weight of the catalyst powder, and the amount of calcium oxide used is 0.5-1.5 wt% of the weight of the catalyst powder.

5. The process according to any one of claims 1 to 4, characterized in that: In step (4), adding and to the filtrate 1, reacting at 40-70° C. for 40-120 min; Preferably, the pH value of the filtrate 1 is adjusted to 8.5-11.0; and / or, Adding diammonium hydrogen phosphate and modified activated carbon-supported nano-zero-valent iron to the second filtrate, stirring and reacting at room temperature for 60 to 90 minutes, and then performing solid-liquid separation. The resulting third filtrate is filtered through a filter membrane with a pore size of 0.2 to 0.5 μm. Preferably, the pH value of the second filtrate is adjusted to 4.5-5.5; More preferably, the amount of diammonium hydrogen phosphate used is 1-3% of the second filtrate, and the amount of modified activated carbon loaded with nano-zero-valent iron used is 0.5-2.0 g / L.

6. The process according to any one of claims 1 to 5, characterized in that: In step (5), the composite extractant comprises trioctyl tertiary amine, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide) salt and white oil; wherein the trioctyl tertiary amine accounts for 15-20 wt %, and the 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide) salt accounts for 3-5 wt %; Preferably, the composite extractant is mixed in the following manner: a. Wash the white oil with 5-10% ammonium carbonate, then wash with water and set aside; b. After acidification and washing with trioctyl tertiary amine and acid solution in a mass ratio of 1:1, set aside; c. 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is mixed with the components treated in steps a and b to obtain a pretreated extractant; d. The pretreated extractant obtained in step c is protonated with an acid solution to obtain the composite extractant; More preferably, in step d, the mass ratio of the pretreated extractant to the acid solution is 1:1, and the protonation treatment time is 5 to 30 minutes; Further preferably, the acid solution in step b is selected from 5-10% sulfuric acid solution, and the acid solution in step d is selected from 5-10% sulfuric acid solution, nitric acid solution or phosphoric acid solution.

7. The process according to claim 6, characterized in that: The mass ratio of the composite extractant to the feed liquid after membrane filtration is 1:5 to 1:15; Preferably, the countercurrent extraction time is 5 to 30 minutes, and the number of stages is 3 to 5; More preferably, the extract phase obtained after countercurrent extraction is washed to remove impurity elements contained in the organic phase; preferably, one or more of deionized water, dilute sulfuric acid or dilute hydrochloric acid is used for washing.

8. The process according to claim 7, characterized in that: In step (6), the stripping is carried out in a stripping tank, and an electric field is applied in a mixing and settling chamber of the stripping tank to promote the migration of metal ions into the mixing and settling chamber; Preferably, the voltage of the applied electric field is 5-10V.

9. The process according to claim 8, characterized in that: The stripping agent is one or more of ammonia water, ammonium carbonate or ammonium bicarbonate solution; Preferably, the concentration of the stripping agent is 10-20%.

10. The process according to claim 9, characterized in that: In step (6), the organic phase obtained after the back extraction is reused as an extractant in step (5); Preferably, the washing comprises two-stage countercurrent water washing and acidification with 5% sulfuric acid solution; More preferably, after the organic phase is reused 5 to 10 times, the acidified organic phase is washed with a washing liquid and then reused as an extractant in step (5), wherein the washing liquid is preferably selected from one or more of sodium carbonate solution, citric acid or peroxygen water, and EDTA-2Na solution is added to the washing liquid.

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