Cyclic extraction and recovery method for tungsten in SCR denitration waste catalyst

Abstract

The invention relates to a cyclic extraction and recovery method for tungsten in an SCR denitration waste catalyst, and belongs to the technical field of recovery of SCR catalysts. Comprising the following steps: physically cleaning, crushing and grinding the SCR denitration waste catalyst to obtain SCR denitration waste catalyst powder, uniformly mixing the SCR denitration waste catalyst powder with a NaOH solution, reacting to leach tungsten, and carrying out solid-liquid separation on slurry obtained after the reaction to obtain a tungsten-containing sodium hydroxide alkaline leaching solution; transforming the organic phase through Na2CO3, performing multi-stage counter-current extraction on the tungsten-containing sodium hydroxide alkaline leachate to be treated to obtain a first tungsten-loaded organic phase, and performing single-stage neutralization washing on the first tungsten-loaded organic phase by using a detergent to obtain a second tungsten-loaded organic phase; and carrying out multi-stage centrifugal countercurrent washing on the second tungsten-loaded organic phase by using pure water to obtain a third tungsten-loaded organic phase, carrying out multi-stage countercurrent reverse extraction on the third tungsten-loaded organic phase to obtain a tungsten-loaded reverse extraction solution, and evaporating and concentrating the tungsten-loaded reverse extraction solution to obtain a tungsten product. The method is high in tungsten recovery rate and low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of SCR catalyst recovery, and in particular to a cyclic extraction and recovery method for tungsten in a SCR denitration waste catalyst. Background Art

[0002] In recent years, with the strengthening of the control of flue gas pollutant emissions, the country's ultra-low emission standards for boiler flue gas have become increasingly stringent. Selective catalytic reduction (SCR) is the mainstream technology for flue gas denitrification in thermal power plants. It is the most efficient, mature and widely used denitrification technology. This technology widely uses catalysts with TiO2 as the carrier and rare metal oxides such as WO3 and V2O5 as the active ingredients.

[0003] During the use of SCR denitration catalyst, there are many factors that will cause its activity to decrease and its life to shorten. It needs to be regenerated or replaced before it can continue to be used. SCR catalyst can generally be regenerated for 3 to 4 cycles. After that, it will be discarded because the catalyst structure is damaged or the regeneration cost will be higher than that of fresh catalyst and cannot be regenerated indefinitely. SCR denitration waste catalyst is a pollutant harmful to the environment and has been listed in the "National Hazardous Waste List". It cannot be landfilled. It contains valuable metals such as tungsten, vanadium and titanium. It is a valuable metal resource. Recycling tungsten, vanadium and titanium can generate considerable economic benefits. At the same time, after the waste catalyst is treated, it is converted from hazardous solid waste to tungsten, vanadium and titanium products for reuse, which has good environmental benefits. The existing SCR denitration waste catalyst treatment technology uses acidic or alkaline solution leaching to separate the vanadium and tungsten elements in the SCR denitration waste catalyst, and then uses extraction or ion exchange to recover them. Since the research on the recovery of SCR denitrification waste catalysts in my country has just started, most of the proposed technical solutions are still unable to truly and efficiently recover components such as vanadium, tungsten / molybdenum and titanium. Problems such as high cost, low recovery rate, low product utilization value and difficulty in industrial application still exist.

[0004] Zhang Guiqing et al. disclosed in Chinese patent CN1110991A a method for directly extracting tungsten from caustic soda (sodium hydroxide) leachate of tungsten ore to prepare ammonium tungstate solution, which mainly includes using quaternary ammonium salt extractants in an alkaline system of sodium carbonate or sodium hydroxide to obtain carbonate and bicarbonate-type quaternary ammonium salt extractants through transformation, using pure water to elute impurities in the extracted load after extraction, and then using one or more of ammonium bicarbonate, sodium bicarbonate and ammonia water for back extraction to obtain the corresponding product solution, and the extractant after back extraction is regenerated by sodium hydroxide solution and returned to the extraction system for process circulation. In this method, the extraction of tungsten is carried out under alkaline conditions (pH>8), and the carbonate of high molecular weight quaternary ammonium is used as the extractant, so it is collectively referred to as quaternary ammonium carbonate alkaline extraction method. This process has a regeneration step, and the regeneration process not only consumes NaOH, but also adds a process, which is not conducive to industrial production; at the same time, the natural sedimentation and phase separation of the two phases in the extraction process of this process is slow, which increases the difficulty of industrial promotion and application. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide a cyclic extraction and recovery method for tungsten in SCR denitrification waste catalyst to solve at least one of the following technical problems: 1. Most of the existing SCR denitrification waste catalyst recovery methods cannot truly and efficiently recover tungsten, and the cost is too high, the recovery rate is low, the product utilization value is small, and it is difficult to apply industrially; 2. The existing quaternary ammonium carbonate alkaline extraction method is used to recover tungsten in SCR denitrification waste catalysts, and there is a regeneration step. The regeneration process not only consumes NaOH, but also adds a process step, resulting in complicated process flows, high costs, and is not conducive to industrial production.

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

[0007] The present invention provides a cyclic extraction and recovery method for tungsten in a waste SCR denitration catalyst, comprising the following steps:

[0008] S1: physically cleaning, crushing and grinding the SCR denitration waste catalyst to obtain SCR denitration waste catalyst powder;

[0009] S2: The SCR denitration waste catalyst powder is mixed evenly with the NaOH solution and reacted to leach tungsten. The slurry after the reaction is separated into solid and liquid to obtain a tungsten-containing sodium hydroxide alkaline leachate;

[0010] S3: transforming the organic phase by using a Na2CO3 solution, and using the transformed organic phase to perform multi-stage countercurrent extraction on the tungsten-containing sodium hydroxide alkaline leachate to be treated to obtain a first tungsten-loaded organic phase and a residual solution after tungsten extraction;

[0011] S4: using a detergent to perform single-stage neutralization washing on the first tungsten-loaded organic phase to obtain a second tungsten-loaded organic phase;

[0012] S5: using pure water to perform multi-stage centrifugal countercurrent water washing on the second tungsten-loaded organic phase to obtain a third tungsten-loaded organic phase;

[0013] S6: using a stripping agent to perform multi-stage countercurrent stripping on the third tungsten-loaded organic phase to obtain a tungsten-loaded stripping solution and a blank organic phase;

[0014] S7: Evaporating and concentrating the loaded tungsten stripping solution to obtain a corresponding tungsten product.

[0015] Furthermore, in step S3, the organic phase comprises an extractant, a modifier and a diluent, and the volume percentage of each component is 10-50% of the extractant, 10-20% of the modifier, and 30-80% of the diluent.

[0016] Furthermore, in step S3, the extractant is a carbonate of methyltrialkylammonium, each alkyl group of which contains 8 to 12 carbon atoms; the modifier is a C8 to C12 high carbon alcohol, and the diluent is D80 solvent oil.

[0017] Furthermore, in step S3, the number of extraction stages of the multi-stage countercurrent extraction is 2 to 10, and during the multi-stage countercurrent extraction process, the volume flow ratio of the organic phase and the sodium hydroxide alkaline leachate in each stage of countercurrent extraction is 1 / 5 to 5 / 1.

[0018] Furthermore, in step S4, the detergent is a sodium bicarbonate solution, and the concentration range of the sodium bicarbonate solution is 0.2 to 1.2 mol / L.

[0019] Furthermore, in step S4, during the single-stage neutralization and washing process, the volume flow ratio of the first tungsten-loaded organic phase to the sodium bicarbonate solution is 5 to 10 / 1.

[0020] Furthermore, in step S5, the washing stages of the multi-stage centrifugal countercurrent washing are 2 to 5 stages.

[0021] Furthermore, in step S5, during the multi-stage centrifugal countercurrent washing process, the volume flow ratio of the second tungsten-loaded organic phase and the water phase in each stage of centrifugal countercurrent washing is 10 to 20 / 1.

[0022] Furthermore, in step S6, the stripping agent is one or both of sodium tungstate and sodium metatungstate; or one or both of ammonium tungstate and ammonium metatungstate.

[0023] Furthermore, in step S6, the number of stages of the multi-stage countercurrent stripping is 2 to 10, and in the process of the multi-stage countercurrent stripping, the volume flow ratio of the third tungsten-loaded organic phase and the stripping agent in each stage of countercurrent stripping is 1 to 20 / 1.

[0024] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0025] 1. The present invention firstly uses a caustic soda leaching method to use a sodium hydroxide solution to leach tungsten from the SCR denitration waste catalyst to obtain a tungsten-containing sodium hydroxide alkaline leachate, and then uses a transformed methyltrialkylammonium carbonate extractant to separate and extract tungsten under alkaline conditions, and obtains a tungsten-free methyltrialkylammonium bicarbonate blank organic phase after multi-stage extraction, single-stage neutralization washing, pure water washing and back extraction. Since a large amount of free sodium hydroxide exists in the tungsten-containing sodium hydroxide alkaline leachate, sufficient reaction conditions are provided for the tungsten-free methyltrialkylammonium bicarbonate blank organic phase to be converted into the methyltrialkylammonium carbonate organic phase. Therefore, the tungsten-free methyltrialkylammonium bicarbonate blank organic phase after back extraction does not need to be regenerated separately, and can be directly subjected to extraction reaction, so that the regeneration and conversion of the organic phase and the extraction are carried out simultaneously, thereby reducing the process operation, shortening the process flow, and reducing the cost of recovering tungsten.

[0026] 2. The tungsten in the SCR denitrification waste catalyst is recovered by the cyclic extraction and recovery method of tungsten in the SCR denitrification waste catalyst of the present invention, without the need for a separate regeneration step, with low cost. At the same time, the tungsten recovery rate can reach more than 99%, and the product purity meets the needs of evaporation and crystallization to produce tungsten related products.

[0027] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0029] Figure 1 The figure is a schematic diagram of the process flow of cyclic extraction and recovery of tungsten in the SCR denitration waste catalyst of the present invention. DETAILED DESCRIPTION

[0030] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0031] The present invention provides a cyclic extraction and recovery method for tungsten in a waste SCR denitration catalyst, comprising the following steps:

[0032] S1: physically cleaning, crushing and grinding the SCR denitration waste catalyst to obtain SCR denitration waste catalyst powder;

[0033] S2: The SCR denitration waste catalyst powder is mixed evenly with the NaOH solution and reacted to leach tungsten. The slurry after the reaction is separated into solid and liquid to obtain a tungsten-containing sodium hydroxide alkaline leachate;

[0034] S3: transforming the organic phase by using a Na2CO3 solution, and using the transformed organic phase to perform multi-stage countercurrent extraction on the tungsten-containing sodium hydroxide alkaline leachate to be treated to obtain a first tungsten-loaded organic phase and a residual solution after tungsten extraction;

[0035] S4: using a detergent to perform single-stage neutralization washing on the first tungsten-loaded organic phase to obtain a second tungsten-loaded organic phase;

[0036] S5: using pure water to perform multi-stage centrifugal countercurrent water washing on the second tungsten-loaded organic phase to obtain a third tungsten-loaded organic phase;

[0037] S6: using a stripping agent to perform multi-stage countercurrent stripping on the third tungsten-loaded organic phase to obtain a tungsten-loaded stripping solution and a blank organic phase;

[0038] S7: Evaporate and concentrate the loaded tungsten stripping solution to obtain the corresponding tungsten product. Figure 1 shown.

[0039] Most of the existing SCR denitrification waste catalyst recovery methods cannot truly and efficiently recover tungsten. They are too costly, have low recovery rates, have low product utilization value, and are difficult to apply industrially. The existing quaternary ammonium carbonate alkaline extraction method is used to recover tungsten from SCR denitrification waste catalysts. There is a regeneration step, which not only consumes NaOH, but also adds a process step, resulting in complicated process flows, high costs, and is not conducive to industrial production. The invention firstly uses a caustic soda leaching method to use a sodium hydroxide solution to achieve leaching of tungsten in a SCR denitration waste catalyst, and obtains a tungsten-containing sodium hydroxide alkaline leachate, and then uses a transformed methyltrialkylammonium carbonate extractant to separate and extract tungsten under alkaline conditions, and obtains a tungsten-free methyltrialkylammonium bicarbonate blank organic phase after multi-stage extraction, single-stage neutralization washing, pure water washing and back extraction. Since a large amount of free sodium hydroxide exists in the tungsten-containing sodium hydroxide alkaline leachate, sufficient reaction conditions are provided for the tungsten-free methyltrialkylammonium bicarbonate blank organic phase, so that the tungsten-free methyltrialkylammonium bicarbonate blank organic phase is converted into the methyltrialkylammonium carbonate organic phase. Therefore, the tungsten-free methyltrialkylammonium bicarbonate blank organic phase after back extraction does not need to be regenerated separately, and can be directly subjected to extraction reaction, so that the regeneration conversion and extraction of the organic phase are carried out simultaneously, thereby reducing process operations, shortening the process flow, and reducing the cost of recovering tungsten.

[0040] Specifically, in step S2, the SCR denitration waste catalyst powder is evenly mixed with the NaOH solution and then reacted, that is, the tungsten in the SCR denitration waste catalyst is leached out by a caustic soda leaching method using a sodium hydroxide solution to obtain a tungsten-containing sodium hydroxide alkaline leaching solution, wherein the tungsten-containing sodium hydroxide alkaline leaching solution is a solution obtained by leaching and separating the tungsten element in the SCR denitration waste catalyst. Among them, the sodium hydroxide is generally 3-6 times the theoretical amount.

[0041] Specifically, in step S3, the organic phase contains an extractant, a modifier and a diluent, and the volume percentage of each component is 10-50% of the extractant, 10-20% of the modifier, and 30-80% of the diluent, wherein the extractant is a carbonate of methyltrialkylammonium, each alkyl group contains 8-12 carbon atoms; the modifier is a C8-C12 high-carbon alcohol, and the diluent is D80 solvent oil. Before extraction, the organic phase is first transformed with a Na2CO3 solution to obtain CO3 2- The method comprises the following steps: a) preparing an organic phase, wherein the concentration of the Na2CO3 solution is 2mol / L-3mol / L, and the volume flow ratio of the organic phase to the Na2CO3 solution is O / A=1 / 1-1 / 2. The methyltrialkylammonium chloride in the organic phase is converted into the carbonate of methyltrialkylammonium through multi-stage cross-current mixing of the Na2CO3 solution and the organic phase.

[0042] Specifically, in the multi-stage countercurrent extraction process in step S3, the volume flow ratio of the transformed organic phase and the tungsten-containing sodium hydroxide alkaline leaching solution is O / A=1 / 5~5 / 1, and the number of extraction stages is 2~10 stages; the residual solution after tungsten extraction is a strong alkaline solution containing part of sodium carbonate, to which quicklime is added by lime causticization method to convert it into sodium hydroxide, which is returned to the leaching system for recycling.

[0043] Specifically, in step S4, the detergent for single-stage neutralization washing is a sodium bicarbonate solution, wherein the concentration range of the sodium bicarbonate solution is 0.2-1.2 mol / L. This step is a single-stage neutralization washing process, wherein the volume flow ratio of the first tungsten-loaded organic phase and the detergent is O / A=5-10 / 1. It should be noted that in the multi-stage countercurrent extraction process of step S3, side reactions occur, not only the target tungstate forms an extractant with the organic phase, but also the free hydroxide in the residual liquid after tungsten extraction forms an extractant with the organic phase. The extractant formed by the hydroxide and the organic phase will consume part of the stripping liquid in the later stage stripping process, reducing the stripping efficiency; therefore, adding a single-stage neutralization washing step before stripping and treating the tungsten-loaded organic phase in advance can significantly improve the stripping efficiency of the later stage. The neutralization washing water produced after washing is an aqueous solution containing a small amount of sodium carbonate. The method of freezing crystallization and sodium precipitation is adopted to obtain pure water and byproduct sodium carbonate that can be reused in the preparation of washing liquid in step S4.

[0044] Specifically, in step S5, the second tungsten-loaded organic phase is subjected to multi-stage centrifugal countercurrent washing with pure water, the washing stages are 2 to 5, and the volume flow ratio of the second tungsten-loaded organic phase and the water phase in each washing stage is O / A=10 to 20 / 1.

[0045] Specifically, in step S6, the stripping agent is one or both of sodium bicarbonate solution or ammonium bicarbonate solution, wherein the concentration range of sodium bicarbonate solution or ammonium bicarbonate solution is 0.5-3 mol / L, and the stripping in this step is a multi-stage countercurrent stripping process, the stripping stage is 2-10 stages, and the volume flow ratio of the third tungsten-loaded organic phase and the stripping agent in each stage is O / A=1-20 / 1. The tungsten-loaded stripping solution generated after the stripping is one or both of sodium tungstate and sodium metatungstate; or one or both of ammonium tungstate and ammonium metatungstate, and then evaporated and concentrated to obtain the corresponding tungsten product.

[0046] It should be noted that the blank organic phase generated after the stripping in step S6 is a blank organic phase of bicarbonate of methyltrialkylammonium that does not contain tungsten, which needs to be converted into a carbonate organic phase of methyltrialkylammonium after reacting with a sodium hydroxide solution before it can be used in the extraction process. Since a large amount of free sodium hydroxide exists in the alkaline sodium hydroxide leachate containing tungsten, a large amount of free sodium hydroxide is always in the residual solution after tungsten extraction during the circulation process, which provides sufficient reaction conditions for the blank organic phase of bicarbonate of methyltrialkylammonium that almost does not contain tungsten, so that it is converted into a carbonate organic phase of methyltrialkylammonium. Therefore, the blank organic phase of bicarbonate of methyltrialkylammonium that does not contain tungsten after stripping does not need to be regenerated separately, and can be directly subjected to extraction reaction, so that the regeneration conversion and extraction of the organic phase are carried out simultaneously; that is, compared with the existing quaternary ammonium carbonate alkaline extraction technology, the present invention does not require transformation and regeneration treatment of the extractant, and can be directly recycled, eliminating the regeneration step that must be implemented in the past, reducing process operations, shortening the process flow, and reducing the cost of recovering tungsten.

[0047] The tungsten in the SCR denitration waste catalyst is recovered by the tungsten cyclic extraction and recovery method of the present invention, without the need for a separate regeneration step, with low cost, a tungsten recovery rate of more than 99%, and product purity that meets the needs of evaporation and crystallization to produce tungsten-related products.

[0048] Example 1

[0049] This embodiment provides a method for recycling and extracting tungsten from a waste SCR denitration catalyst, comprising the following steps:

[0050] S1: physically cleaning, crushing and grinding the SCR denitration waste catalyst to obtain SCR denitration waste catalyst powder;

[0051] S2: SCR denitration waste catalyst powder is mixed with NaOH solution and reacted to leach tungsten. The slurry after the reaction is separated into solid and liquid to obtain tungsten-containing sodium hydroxide alkaline leachate;

[0052] The amount of NaOH used is 5 times the theoretical amount;

[0053] S3: transforming the organic phase by using a Na2CO3 solution, and using the transformed organic phase to perform a five-stage countercurrent extraction on the tungsten-containing sodium hydroxide alkaline leachate to be treated to obtain a first tungsten-loaded organic phase and a residual solution after tungsten extraction;

[0054] The organic phase contains an extractant, a modifier and a diluent, and the components are calculated by volume percentage as follows: the extractant is N263: 20%, the modifier is octanol: 10%, and the diluent is D80 solvent oil: 70%. N263 is a methyltrialkylammonium chloride. Before extraction, the organic phase is pre-mixed with a 2.5 mol / L Na2CO3 solution at a ratio of O / A=1 / 1 by multi-stage cross-flow mixing to convert the methyltrialkylammonium chloride in the organic phase into the carbonate of methyltrialkylammonium;

[0055] The tungsten-containing sodium hydroxide alkaline leachate contains 35.18 g / L WO3 and 49.33 g / L NaOH. The leachate is mixed with the organic phase for 5-stage countercurrent extraction. The volume flow ratio of the organic phase and the tungsten-containing sodium hydroxide alkaline leachate is O / A=1 / 1, and the first tungsten-loaded organic phase and the residual solution after tungsten extraction are obtained. The residual solution after tungsten extraction contains 0.14 g / L WO3 and 48.57 g / L NaOH.

[0056] S4: using a detergent to perform single-stage neutralization washing on the first tungsten-loaded organic phase to obtain a second tungsten-loaded organic phase;

[0057] The concentration of the sodium bicarbonate solution used is 0.25 mol / L, and the volume flow ratio of the first tungsten-loaded organic phase and the sodium bicarbonate solution is O / A=10 / 1.

[0058] S5: using pure water to perform three-stage centrifugal countercurrent water washing on the second tungsten-loaded organic phase, wherein the volume flow ratio of the second tungsten-loaded organic phase and the water phase in each stage of washing is O / A=15 / 1, to obtain a third tungsten-loaded organic phase;

[0059] S6: using a stripping agent to perform five-stage tungsten stripping on the third tungsten-loaded organic phase to obtain a tungsten-loaded stripping solution and a blank organic phase;

[0060] The stripping agent is 2 mol / L ammonium bicarbonate solution, and the volume flow ratio of the third tungsten-loaded organic phase and the stripping agent in each stripping stage is O / A=10 / 1, and the tungsten-loaded stripping solution and the blank organic phase are obtained. The blank organic phase is directly used in the back extraction system without further conversion into CO3 2- type.

[0061] S7: Evaporating and concentrating the loaded tungsten stripping solution to obtain a corresponding tungsten product.

[0062] Example 2

[0063] This embodiment provides a method for recycling and extracting tungsten from a waste SCR denitration catalyst, comprising the following steps:

[0064] S1: physically cleaning, crushing and grinding the SCR denitration waste catalyst to obtain SCR denitration waste catalyst powder;

[0065] S2: SCR denitration waste catalyst powder is mixed with NaOH solution and reacted to leach tungsten. The slurry after the reaction is separated into solid and liquid to obtain tungsten-containing sodium hydroxide alkaline leachate;

[0066] The amount of NaOH used is 6 times the theoretical amount;

[0067] S3: transforming the organic phase by using a Na2CO3 solution, and using the transformed organic phase to perform a five-stage countercurrent extraction on the tungsten-containing sodium hydroxide alkaline leachate to be treated to obtain a first tungsten-loaded organic phase and a residual solution after tungsten extraction;

[0068] The organic phase contains an extractant, a modifier and a diluent, and the components are calculated by volume percentage as follows: the extractant is N263: 30%, the modifier is isooctyl alcohol: 20%, and the diluent is D80 solvent oil: 50%. Before extraction, the organic phase is pre-mixed with a 2.5 mol / L Na2CO3 solution at a ratio of O / A=1 / 1 by multi-stage cross-flow, so that the methyltrialkylammonium chloride in the organic phase is converted into methyltrialkylammonium carbonate;

[0069] The tungsten-containing sodium hydroxide alkaline leachate contains WO3 52.32g / L and NaOH 90.58g / L. The leachate is mixed with the organic phase for 5-stage countercurrent extraction. The volume flow ratio of the organic phase to the sodium hydroxide alkaline leachate is O / A=2 / 1, and the first tungsten-loaded organic phase and the residual solution after tungsten extraction are obtained. The residual solution after tungsten extraction contains WO3 0.26g / L and NaOH 88.79g / L.

[0070] S4: using a detergent to perform single-stage neutralization washing on the first tungsten-loaded organic phase;

[0071] The concentration of the sodium bicarbonate solution used is 0.4 mol / L, and the volume flow ratio of the first tungsten-loaded organic phase and the sodium bicarbonate solution is O / A=8 / 1, thereby obtaining a second tungsten-loaded organic phase;

[0072] S5: using pure water to perform five-stage centrifugal countercurrent water washing on the second tungsten-loaded organic phase, wherein the volume flow ratio of the second tungsten-loaded organic phase and the water phase in each stage of washing is O / A=12 / 1, to obtain a third tungsten-loaded organic phase;

[0073] S6: using a stripping agent to perform 8-stage tungsten stripping on the third tungsten-loaded organic phase to obtain a tungsten-loaded stripping solution and a blank organic phase;

[0074] The stripping agent is 2.5 mol / L ammonium bicarbonate solution. The volume flow ratio of the third tungsten-loaded organic phase and the stripping agent in each stripping stage is O / A=10 / 1. The tungsten-loaded stripping solution and the blank organic phase are obtained. The blank organic phase is directly used in the back extraction system without further conversion into CO3. 2- type.

[0075] S7: Evaporating and concentrating the loaded tungsten stripping solution to obtain a corresponding tungsten product.

[0076] Comparative Example 1

[0077] This comparative example provides a cyclic extraction and recovery method for tungsten in a waste SCR denitration catalyst, comprising the following steps:

[0078] S1: physically cleaning, crushing and grinding the SCR denitration waste catalyst to obtain SCR denitration waste catalyst powder;

[0079] S2: SCR denitration waste catalyst powder is mixed with NaOH solution and reacted to leach tungsten. The slurry after the reaction is separated into solid and liquid to obtain tungsten-containing sodium hydroxide alkaline leachate;

[0080] The amount of NaOH used is 6 times the theoretical amount;

[0081] S3: using an organic phase to perform five-stage countercurrent extraction on the tungsten-containing sodium hydroxide alkaline leachate to be treated to obtain a first tungsten-loaded organic phase and a residual solution after tungsten extraction;

[0082] The organic phase contains an extractant, a modifier and a diluent, and the components are calculated by volume percentage as follows: the extractant is N263: 60%, the modifier is isooctyl alcohol: 20%, and the diluent is D80 solvent oil: 20%. Before extraction, the organic phase is pre-mixed with a 2.5 mol / L Na2CO3 solution at a ratio of O / A=1 / 1 for multi-stage cross-flow mixing to convert the methyltrialkylammonium chloride in the organic phase into the carbonate of methyltrialkylammonium.

[0083] The tungsten-containing sodium hydroxide alkaline leachate contains WO3 52.32g / L and NaOH 90.58g / L. The leachate is mixed with the organic phase for 5-stage countercurrent extraction. The volume flow ratio of the organic phase to the sodium hydroxide alkaline leachate is O / A=6 / 1, and the first tungsten-loaded organic phase and the residual solution after tungsten extraction are obtained. The residual solution after tungsten extraction contains WO3 0.08g / L and NaOH 87.92g / L.

[0084] S4: using a detergent to perform single-stage neutralization washing on the first tungsten-loaded organic phase;

[0085] The concentration of the sodium bicarbonate solution used is 1.5 mol / L, and the volume flow ratio of the first tungsten-loaded organic phase and the sodium bicarbonate solution is O / A=12 / 1, thereby obtaining a second tungsten-loaded organic phase;

[0086] S5: using pure water to perform five-stage centrifugal countercurrent water washing on the second tungsten-loaded organic phase, wherein the volume flow ratio of the second tungsten-loaded organic phase and the water phase in each stage of washing is O / A=8 / 1, to obtain a third tungsten-loaded organic phase;

[0087] S6: using a stripping agent to perform 8-stage tungsten stripping on the third tungsten-loaded organic phase to obtain a tungsten-loaded stripping solution and a blank organic phase;

[0088] The stripping agent is 0.4 mol / L ammonium bicarbonate solution, and the volume flow ratio of the third tungsten-loaded organic phase and the stripping agent in each stripping stage is O / A=22 / 1, and the tungsten-loaded stripping solution and the blank organic phase are obtained. The blank organic phase is directly used in the back extraction system without further conversion into CO3 2- type.

[0089] S7: Evaporating and concentrating the loaded tungsten stripping solution to obtain a corresponding tungsten product.

[0090] Comparative Example 2

[0091] This comparative example provides a cyclic extraction and recovery method for tungsten in a waste SCR denitration catalyst, comprising the following steps:

[0092] S1: physically cleaning, crushing and grinding the SCR denitration waste catalyst to obtain SCR denitration waste catalyst powder;

[0093] S2: The SCR denitration waste catalyst powder is mixed evenly with the NaOH solution and reacted to leach tungsten. The slurry after the reaction is separated into solid and liquid to obtain a tungsten-containing sodium hydroxide alkaline leachate;

[0094] The amount of NaOH used is 6 times the theoretical amount;

[0095] S3: using an organic phase to perform five-stage countercurrent extraction on the tungsten-containing sodium hydroxide alkaline leachate to be treated to obtain a first tungsten-loaded organic phase and a residual solution after tungsten extraction;

[0096] The organic phase contains an extractant, a modifier and a diluent, and the components are calculated by volume percentage as follows: the extractant is N263: 30%, the modifier is isooctyl alcohol: 20%, and the diluent is D80 solvent oil: 50%. Before extraction, the organic phase is pre-mixed with a 2.5 mol / L Na2CO3 solution at a ratio of O / A=1 / 1 for multi-stage cross-flow mixing to convert the methyltrialkylammonium chloride in the organic phase into methyltrialkylammonium carbonate.

[0097] The tungsten-containing sodium hydroxide alkaline leachate contains WO3 52.32g / L and NaOH 90.58g / L. The leachate is mixed with the organic phase for 5-stage countercurrent extraction. The volume flow ratio of the organic phase to the sodium hydroxide alkaline leachate is O / A=2 / 1, and the first tungsten-loaded organic phase and the residual solution after tungsten extraction are obtained. The residual solution after tungsten extraction contains WO3 0.28g / L and NaOH 88.65g / L.

[0098] S4: using pure water to perform five-stage centrifugal countercurrent water washing on the first tungsten-loaded organic phase, wherein the volume flow ratio of the first tungsten-loaded organic phase and the water phase in each stage of washing is O / A=12 / 1, to obtain a second tungsten-loaded organic phase;

[0099] S6: using a stripping agent to perform 8-stage tungsten stripping on the second tungsten-loaded organic phase to obtain a tungsten-loaded stripping solution and a blank organic phase;

[0100] The stripping agent is 2.5 mol / L ammonium bicarbonate solution. The volume flow ratio of the third tungsten-loaded organic phase and the stripping agent in each stripping stage is O / A=10 / 1. The tungsten-loaded stripping solution and the blank organic phase are obtained. The blank organic phase is directly used in the back extraction system without further conversion into CO3. 2- type.

[0101] S7: Evaporating and concentrating the loaded tungsten stripping solution to obtain a corresponding tungsten product.

[0102] Comparative Example 3

[0103] This comparative example provides a method for extracting and recovering tungsten from a waste SCR denitration catalyst, comprising the following steps:

[0104] S1: physically cleaning, crushing and grinding the SCR denitration waste catalyst to obtain SCR denitration waste catalyst powder;

[0105] S2: SCR denitration waste catalyst powder is mixed evenly with alkaline solution and reacted to leach tungsten. The slurry after the reaction is separated into solid and liquid to obtain alkaline leaching solution containing tungsten;

[0106] S3: using an organic phase to perform five-stage countercurrent extraction on the tungsten-containing alkaline leachate to be treated to obtain a first tungsten-loaded organic phase and a residual solution after tungsten extraction;

[0107] The tungsten-containing alkaline leachate contains 50.62 g / L of WO3. The leachate is mixed with the organic phase and subjected to 5-stage countercurrent extraction. The volume flow ratio of the organic phase to the alkaline leachate is O / A=2 / 1, and the first tungsten-loaded organic phase and the residual solution after tungsten extraction are obtained. The residual solution after tungsten extraction contains 0.22 g / L of WO3.

[0108] S4: using pure water to perform five-stage centrifugal countercurrent water washing on the first tungsten-loaded organic phase, wherein the volume flow ratio of the first tungsten-loaded organic phase and the water phase in each stage of washing is O / A=15 / 1, to obtain a second tungsten-loaded organic phase;

[0109] S6: using a stripping agent to perform 8-stage tungsten stripping on the second tungsten-loaded organic phase to obtain a tungsten-loaded stripping solution and a stripped organic phase;

[0110] The stripping agent is a mixed solution of ammonia water and ammonium bicarbonate, and the volume flow ratio of the third tungsten-loaded organic phase and the stripping agent in each stage of stripping is O / A=10 / 1, thereby obtaining a tungsten-loaded stripping solution and an organic phase after stripping.

[0111] S7: Use sodium hydroxide solution to perform single-stage regeneration treatment on the organic phase after stripping to obtain CO3 2- Type blank organic phase;

[0112] The sodium hydroxide solution is generally 1-2 mol / L, and the volume flow ratio of the organic phase and the sodium hydroxide solution after stripping is O / A=1 / 1, and a blank organic phase is obtained and returned to the extraction system for recycling.

[0113] S8: Evaporating and concentrating the loaded tungsten stripping solution to obtain the corresponding tungsten product.

[0114] Table 1 shows the recovery rate, extraction rate, product purity and operating reagent cost of tungsten recovered in the embodiments of the present invention and the comparative example. It can be seen from Table 1 that by using the tungsten cyclic extraction and recovery method for tungsten in SCR denitration waste catalyst of the present invention, the tungsten recovery rate can reach more than 99%, which is significantly higher than the comparative example; at the same time, when the extraction rate and purity are equivalent, the cost of recovering tungsten by the method of the present invention is significantly reduced.

[0115] Comparative Example 4

[0116] This comparative example provides a cyclic extraction and recovery method for tungsten in a waste SCR denitration catalyst, comprising the following steps:

[0117] S1: physically cleaning, crushing and grinding the SCR denitration waste catalyst to obtain SCR denitration waste catalyst powder;

[0118] S2: The SCR denitration waste catalyst powder is mixed evenly with the NaOH solution and reacted to leach tungsten. The slurry after the reaction is separated into solid and liquid to obtain a tungsten-containing sodium hydroxide alkaline leachate;

[0119] The amount of NaOH used is twice the theoretical amount;

[0120] S3: transforming the organic phase by using a Na2CO3 solution, and using the transformed organic phase to perform a five-stage countercurrent extraction on the tungsten-containing sodium hydroxide alkaline leachate to be treated to obtain a first tungsten-loaded organic phase and a residual solution after tungsten extraction;

[0121] The organic phase contains an extractant, a modifier and a diluent, and the components are calculated by volume percentage as follows: the extractant is N263: 20%, the modifier is isooctyl alcohol: 10%, and the diluent is D80 solvent oil: 70%. Before extraction, the organic phase is pre-mixed with a 2.5 mol / L Na2CO3 solution at a ratio of O / A=1 / 1 for multi-stage cross-flow mixing to convert the methyltrialkylammonium chloride in the organic phase into methyltrialkylammonium carbonate;

[0122] The tungsten-containing sodium hydroxide alkaline leachate contains WO3 26.32g / L and NaOH 11.43g / L. The leachate is mixed with the organic phase for 5-stage countercurrent extraction. The volume flow ratio of the organic phase to the sodium hydroxide alkaline leachate is O / A=1 / 1, and the first tungsten-loaded organic phase and the residual solution after tungsten extraction are obtained. The residual solution after tungsten extraction contains WO3 0.12 / L and NaOH 10.57g / L.

[0123] S4: using a detergent to perform single-stage neutralization washing on the first tungsten-loaded organic phase;

[0124] The concentration of the sodium bicarbonate solution used is 0.25 mol / L, and the volume flow ratio of the first tungsten-loaded organic phase and the sodium bicarbonate solution is O / A=10 / 1, thereby obtaining a second tungsten-loaded organic phase;

[0125] S5: using pure water to perform five-stage centrifugal countercurrent water washing on the second tungsten-loaded organic phase, wherein the volume flow ratio of the second tungsten-loaded organic phase and the water phase in each stage of washing is O / A=12 / 1, to obtain a third tungsten-loaded organic phase;

[0126] S6: using a stripping agent to perform five-stage tungsten stripping on the third tungsten-loaded organic phase to obtain a tungsten-loaded stripping solution and a blank organic phase;

[0127] The stripping agent is 2 mol / L ammonium bicarbonate solution, and the volume flow ratio of the third tungsten-loaded organic phase and the stripping agent in each stripping stage is O / A=10 / 1, and the tungsten-loaded stripping solution and the blank organic phase are obtained. The blank organic phase is directly used in the back extraction system without further conversion into CO3 2- type.

[0128] S7: Evaporating and concentrating the loaded tungsten stripping solution to obtain a corresponding tungsten product.

[0129] Table 1 shows the relevant parameters of tungsten recovery in the examples and comparative examples.

[0130] Table 1 is the relevant parameter characterization of tungsten recovery in the examples and comparative examples

[0131] Yield / % Extraction rate / % Cost / ton purity / % Example 1 99.32 99.60 450 99.5 Example 2 99.18 99.50 852 99.3 Comparative Example 1 46.54 99.85 4400 99.4 Comparative Example 2 80.62 99.46 745 99.2 Comparative Example 3 81.39 99.57 8512 99.3

[0132] Note: The costs in the above embodiments and comparative examples are calculated based on the auxiliary reagents consumed in each stage of production operation; the higher the yield, the less raw material liquid is required to produce 1 ton of product, and the corresponding production cost is also lower. Conversely, the lower the yield, the more raw material liquid is required to produce 1 ton of product, and the corresponding production cost will also increase; the concentration of WO3 in the leachate and changes in other conditions will also cause fluctuations in production costs;

[0133] Although the cost of Comparative Example 2 is slightly lower than that of Example 2, due to its low yield, a large amount of resources will be wasted. Considering the recycling and other costs, its comprehensive cost is much higher than that of Example 2.

[0134] In Comparative Example 4, since the actual amount of sodium hydroxide used in the leaching process is relatively small, firstly, the leaching efficiency will be reduced and the concentrations of various indicators of the leachate will be low. Secondly, due to the lack of free sodium hydroxide in the leachate, the tungsten-loaded organic phase will not be able to be completely transformed during the extraction process, and can only complete a limited number of extractions, and cannot complete the complete cyclic extraction process. At this time, the entire tungsten recovery process needs to be restarted, and thus the yield, extraction rate, cost, purity and other data of the cyclically recovered tungsten cannot be calculated; if the extraction needs to continue, it is necessary to increase the regeneration step, and add sodium hydroxide solution from the outside to regenerate the blank organic phase, then the cost required to complete the cyclic extraction process will be greatly increased, about 8,500 yuan / ton.

[0135] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for recycling tungsten from SCR denitration waste catalyst by extraction, characterized in that: The following steps are involved: S1: physically cleaning, crushing and grinding the SCR denitration waste catalyst to obtain SCR denitration waste catalyst powder; S2: The SCR denitration waste catalyst powder is mixed evenly with the NaOH solution and reacted to leach tungsten. The slurry after the reaction is separated into solid and liquid to obtain a tungsten-containing sodium hydroxide alkaline leachate; S3: transforming the organic phase by using a Na2CO3 solution, and using the transformed organic phase to perform multi-stage countercurrent extraction on the tungsten-containing sodium hydroxide alkaline leachate to be treated to obtain a first tungsten-loaded organic phase and a residual solution after tungsten extraction; S4: using a detergent to perform single-stage neutralization washing on the first tungsten-loaded organic phase to obtain a second tungsten-loaded organic phase; S5: using pure water to perform multi-stage centrifugal countercurrent water washing on the second tungsten-loaded organic phase to obtain a third tungsten-loaded organic phase; S6: using a stripping agent to perform multi-stage countercurrent stripping on the third tungsten-loaded organic phase to obtain a tungsten-loaded stripping solution and a blank organic phase; S7: Evaporating and concentrating the loaded tungsten stripping solution to obtain a corresponding tungsten product.

2. The cyclic extraction recovery method according to claim 1, characterized in that: In step S3, the organic phase contains an extractant, a modifier and a diluent, and the volume percentage of each component is: 10-50% of the extractant, 10-20% of the modifier, and 30-80% of the diluent.

3. The cyclic extraction recovery method according to claim 2, characterized in that: In step S3, the extractant is a carbonate of methyltrialkylammonium, each alkyl group of which contains 8 to 12 carbon atoms; the modifier is a C8 to C12 high carbon alcohol, and the diluent is D80 solvent oil.

4. The cyclic extraction recovery method according to claim 3, characterized in that: In step S3, the number of extraction stages of the multi-stage countercurrent extraction is 2 to 10. During the multi-stage countercurrent extraction, the volume flow ratio of the organic phase and the sodium hydroxide alkaline leachate in each stage of countercurrent extraction is 1 / 5 to 5 / 1.

5. The cyclic extraction recovery method according to claim 4, characterized in that: In step S4, the detergent is a sodium bicarbonate solution, and the concentration range of the sodium bicarbonate solution is 0.2-1.2 mol / L.

6. The cyclic extraction recovery method according to claim 5, characterized in that: In step S4, during the single-stage neutralization and washing process, the volume flow ratio of the first tungsten-loaded organic phase to the sodium bicarbonate solution is 5 to 10 / 1.

7. The cyclic extraction recovery method according to claim 6, characterized in that: In step S5, the washing stages of the multi-stage centrifugal countercurrent washing are 2 to 5 stages.

8. The cyclic extraction recovery method according to claim 7, characterized in that: In step S5, during the multi-stage centrifugal countercurrent washing process, the volume flow ratio of the second tungsten-loaded organic phase and the water phase in each stage of centrifugal countercurrent washing is 10-20 / 1.

9. The cyclic extraction recovery method according to claim 8, characterized in that: In step S6, the stripping agent is one or both of sodium tungstate and sodium metatungstate; or one or both of ammonium tungstate and ammonium metatungstate.

10. The cyclic extraction recovery method according to claim 9, characterized in that: In step S6, the number of the multi-stage countercurrent stripping is 2 to 10. During the multi-stage countercurrent stripping, the volume flow ratio of the third tungsten-loaded organic phase and the stripping agent in each stage of countercurrent stripping is 1 to 20 / 1.

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