Comprehensive utilization method of waste catalyst

Abstract

The invention relates to the technical field of hazardous waste utilization, in particular to a comprehensive utilization method of a waste catalyst. The method specifically comprises the following steps: sequentially carrying out oxidizing roasting, wet ball milling and pressure leaching on the waste catalyst to obtain a first leaching solution and leaching residues; the first leachate is extracted in a multi-stage counter-current extraction mode, molybdenum and tungsten in the first leachate are extracted, and back extraction is conducted to obtain back extraction liquid containing molybdenum and tungsten; the strip liquor is subjected to standing deoiling, evaporation concentration and multi-stage counter-current extraction vanadium removal in sequence, and raffinate and vanadium-containing strip liquor are obtained; the raffinate mainly contains molybdate radicals and tungstate radicals; determining a separation mode according to different molar ratios of molybdenum and tungsten; carrying out acid leaching on the leaching residues by utilizing a sulfuric acid solution at normal temperature and normal pressure to obtain a second leaching solution; and a cobalt extraction agent and a nickel extraction agent are respectively used for extraction, and a cobalt sulfate product and a nickel sulfate product are obtained after reverse extraction and evaporative crystallization. According to the method provided by the invention, metal resources such as vanadium, tungsten, cobalt, molybdenum and nickel in the waste catalyst can be recycled.

Description

Technical Field

[0001] The present application relates to the technical field of hazardous waste utilization, and in particular to a method for comprehensive utilization of waste catalysts. Background Art

[0002] In the production process of petrochemical products, a large amount of vanadium, tungsten, cobalt, molybdenum, and nickel-based waste catalysts are used. For example, when ethylene and propylene obtained from the cracking of petroleum hydrocarbons are used as polymerization raw materials, they must first be selectively hydrogenated. The hydrogenation catalyst used is generally cobalt, molybdenum, and nickel active components supported on alumina. For example, hydrogenation catalysts are used in the refining of cracked gasoline; cobalt-molybdenum conversion catalysts are also used in methanol production; tungsten and nickel catalysts are often used in cracking reactors; vanadium-tungsten catalysts are often used in flue gas purification.

[0003] After a certain number of years of use, the catalyst will lose its activity and need to be replaced. According to the National List of Hazardous Wastes, the replaced waste catalysts belong to the HW50 category of waste catalysts and need to be treated as hazardous wastes. The commonly used treatment method is safe landfill disposal, but this method will cause waste of resources. In addition, the metal resources in the waste catalysts can also be recycled. The recycling is usually only for a specific metal or a single type of catalyst, and cannot be applied to the recycling of waste catalysts containing multiple types of metals such as vanadium, tungsten, cobalt, molybdenum, and nickel.

[0004] Therefore, in order to further improve the recovery efficiency of metal resources in waste catalysts, it is urgent to find a method to simultaneously recover multiple types of metals in waste catalysts. Summary of the invention

[0005] The present application provides a method for comprehensive utilization of waste catalysts. The method provided in the present application can recover metal resources such as vanadium, tungsten, cobalt, molybdenum, nickel, etc. in waste catalysts. The method can be applied to the treatment of waste catalysts of a single type or multiple types and waste catalysts containing various metals at the same time, with high recovery rate, high product purity and wide application range.

[0006] In the first aspect, the present application provides a method for comprehensive utilization of waste catalysts, which adopts the following technical scheme:

[0007] A method for comprehensive utilization of waste catalysts, the method specifically comprising the following steps:

[0008] The waste catalyst is subjected to oxidation roasting, wet ball milling, and pressure leaching in sequence to obtain a first leaching solution and leaching residue; the first leaching solution is used for recovering molybdenum, tungsten, and vanadium; the leaching residue is used for recovering nickel and cobalt;

[0009] For the first leachate:

[0010] The first leachate is extracted by multi-stage countercurrent extraction, molybdenum and tungsten are extracted therein, and then stripping solution containing molybdenum and tungsten is obtained after stripping; the stripping solution is sequentially placed for deoiling, evaporated and concentrated, and subjected to multi-stage countercurrent extraction to remove vanadium, to obtain a raffinate and a stripping solution containing vanadium;

[0011] The raffinate mainly contains molybdate and tungstate. Different separation methods are determined according to the molar ratio of molybdenum to tungsten, specifically:

[0012] A. When the molybdenum content is close to the tungsten content, that is, the molar ratio of the two is 0.2-5: first evaporation and concentration are adopted to make the tungsten with a larger content crystallize out in the form of ammonium paratungstate. At this time, the ammonium paratungstate crystals still contain a small amount of ammonium molybdate, which needs to be further removed by dissolution-ion exchange steps, and then evaporated and crystallized to obtain a pure ammonium paratungstate product; at the same time, the concentrated mother liquor in the first step of evaporation and concentration is mainly ammonium molybdate, containing a small amount of ammonium paratungstate. The concentrated mother liquor is extracted to remove tungsten and then evaporated and crystallized to obtain a pure ammonium molybdate product;

[0013] B. When the molybdenum content is much greater than the tungsten content, that is, the molar ratio of the two is greater than 5: directly use the extraction method to remove tungsten, and then evaporate and crystallize after tungsten removal to obtain pure ammonium molybdate product;

[0014] C. When the molybdenum content is much less than the tungsten content, that is, the molar ratio of the two is less than 0.2: directly use ion exchange to remove molybdenum, and then evaporate and crystallize after removing molybdenum to obtain pure ammonium paratungstate product;

[0015] For the leached residue: the leached residue is subjected to acid leaching with a sulfuric acid solution at normal temperature and pressure to obtain a second leaching solution; a cobalt extractant and a nickel extractant are used for extraction respectively, and a cobalt sulfate product and a nickel sulfate product are obtained after back extraction, evaporation and crystallization.

[0016] Optionally, the spent catalyst contains any one or more of molybdenum, tungsten, vanadium, nickel and cobalt.

[0017] Optionally, the V2O5 concentration in the raffinate can be reduced to below 0.01 g / L.

[0018] Optionally, the vanadium removal rate in the raffinate reaches more than 99%.

[0019] Optionally, (NH4)2SO4 is added to the vanadium-containing stripping solution at pH=8-9 to cause double decomposition reaction to obtain ammonium metavanadate crystals.

[0020] Optionally, the second leachate is first extracted with the cobalt extractant, and a cobalt sulfate product is obtained after back extraction, evaporation and crystallization; and the raffinate obtained after the back extraction is extracted with a nickel extractant, and a nickel sulfate product is obtained after back extraction, evaporation and crystallization.

[0021] Optionally, a corresponding extractant is selected according to the nickel and cobalt contents in the second leaching solution.

[0022] Optionally, when the Co / Ni content is greater than 1 / 5, the selected extractant is P204; when 1 / 10 is less than the Co / Ni content and less than 1 / 5, the selected extractant is P507; when the Co / Ni content is less than 1 / 10, the selected extractant is Cyanex272.

[0023] In summary, the present application includes at least one of the following beneficial technical effects:

[0024] 1. The comprehensive utilization method of waste catalysts in the present application has a wide range of applications. It can be used not only for the treatment of single metal waste catalysts, but also for the treatment of waste catalysts containing multiple metals such as vanadium, tungsten, cobalt, molybdenum, and nickel. It has a high metal recovery rate and high product purity.

[0025] 2. Use a combination of alkali leaching / acid leaching to leach different metals separately, which can reduce subsequent separation costs, improve product purity, and avoid mutual interference between metals during separation and recovery.

[0026] 3. The extraction performance of molybdenum, tungsten, vanadium, nickel and cobalt with different extractants, determine the extractant with the highest comprehensive efficiency, optimize various extraction indicators, combine with box extraction or tubular extraction equipment, and achieve the goal of step-by-step separation of precious metal elements in complex multi-metal solutions by accurately controlling reaction parameters, thereby improving the recovery rate.

[0027] 4. Washing the acid leaching filter press residue and the purification residue can further improve the recovery rate. At the same time, the purification residue washing liquid can also be used for acid leaching residue washing, and finally returned to the acid leaching reactor for treatment.

[0028] 5. Through alkali leaching of molybdenum, tungsten and vanadium waste catalysts and extraction of molybdenum from the low-vanadium raffinate, the sodium salt is converted into sodium hydroxide through causticization, and then returned to high-pressure alkali leaching to form a closed-loop circulation of the aqueous phase based on "leaching-extraction-crystallization", thereby improving the recycling rate of water, alkali and ammonia, the alkali conversion rate of the low-vanadium raffinate reaches more than 80%, and the recycling rate of ammonia reaches more than 70%, thereby reducing wastewater generation and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A flow chart of the method for comprehensive utilization of waste catalysts provided in this application. DETAILED DESCRIPTION

[0030] Before describing the embodiments of the present application in detail, it should be understood that the terms used herein are only used for the purpose of describing specific embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by ordinary technicians in the field to which the terms belong.

[0031] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of this application, unless otherwise specified, the meaning of "plurality" is two or more.

[0032] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0033] In the present application, the terms "comprise" or "include" are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0034] The present application provides a method for comprehensive utilization of waste catalysts. The waste catalysts are subjected to oxidation roasting, wet ball milling, and pressure leaching in sequence to obtain a first leaching solution and leaching residues; the first leaching solution is used to recover molybdenum, tungsten, and vanadium; the leaching residues are used to recover nickel and cobalt;

[0035] For the first leachate:

[0036] The first leachate is extracted by multi-stage countercurrent extraction, molybdenum and tungsten are extracted therein, and then stripping solution containing molybdenum and tungsten is obtained after stripping; the stripping solution is sequentially placed for deoiling, evaporated and concentrated, and subjected to multi-stage countercurrent extraction to remove vanadium, to obtain a raffinate and a stripping solution containing vanadium;

[0037] The raffinate mainly contains molybdate and tungstate. Different separation methods are determined according to the molar ratio of molybdenum to tungsten, specifically:

[0038] A. When the molybdenum content is close to the tungsten content, that is, the molar ratio of the two is 0.2-5: first evaporation and concentration are adopted to make the tungsten with a larger content crystallize out in the form of ammonium paratungstate. At this time, the ammonium paratungstate crystals still contain a small amount of ammonium molybdate, which needs to be further removed by dissolution-ion exchange steps, and then evaporated and crystallized to obtain a pure ammonium paratungstate product; at the same time, the concentrated mother liquor in the first step of evaporation and concentration is mainly ammonium molybdate, containing a small amount of ammonium paratungstate. The concentrated mother liquor is extracted to remove tungsten and then evaporated and crystallized to obtain a pure ammonium molybdate product;

[0039] B. When the molybdenum content is much greater than the tungsten content, that is, the molar ratio of the two is greater than 5: directly use the extraction method to remove tungsten, and then evaporate and crystallize after tungsten removal to obtain pure ammonium molybdate product;

[0040] C. When the molybdenum content is much less than the tungsten content, that is, the molar ratio of the two is less than 0.2: directly use ion exchange to remove molybdenum, and then evaporate and crystallize after removing molybdenum to obtain pure ammonium paratungstate product;

[0041] For the leached residue: the leached residue is subjected to acid leaching with a sulfuric acid solution at normal temperature and pressure to obtain a second leaching solution; a cobalt extractant and a nickel extractant are used for extraction respectively, and a cobalt sulfate product and a nickel sulfate product are obtained after back extraction, evaporation and crystallization.

[0042] In a specific embodiment, Figure 1 As shown, a method for comprehensive utilization of waste catalysts specifically comprises the following steps:

[0043] (1) Oxidation roasting

[0044] The waste catalysts (containing molybdenum, tungsten, vanadium, nickel, and cobalt) are transported from the temporary storage to the raw material intermediate warehouse, and the heavy oil and other organic matter on the surface of the waste catalysts are removed by direct combustion in a rotary kiln. The combustion temperature is 600-700°C and the roasting time is 1.5-2.5h.

[0045] The flue gas generated by the combustion of heavy oil on the surface of the waste catalyst enters the secondary combustion chamber and is secondary burned with natural gas as fuel. The combustion temperature is 1050-1150℃ and the residence time is greater than 2 seconds, so that the flue gas is fully burned. The flue gas after the secondary high-temperature combustion is desulfurized using the double alkali method and discharged through the exhaust pipe to meet the standards.

[0046] Among them, the reaction equations involved in the above-mentioned oxidation roasting are specifically as follows: 2MoS2+7O2=2MoO3+4SO2; NiS+3O2=2NiO+2SO2; 2CoS+3O2=2CoO+2SO2.

[0047] (2) Ball milling-pressure alkali leaching

[0048] The waste catalyst treated in step (1) is transported to a silo, and then enters a wet ball mill from the silo for wet ball milling. The slurry after ball milling flows to a batching tank by gravity, and then an appropriate amount of water and alkali (such as sodium hydroxide and sodium carbonate, the weight ratio of the two is (1-2):1, the total concentration is 30%) is added, and the liquid-solid ratio is (5-10):1. The slurry is then pumped to a leaching kettle for heating and leaching, and the leached residue is discharged.

[0049] The leachate flows by gravity into the leachate storage tank and is pumped to the subsequent molybdenum, tungsten and vanadium recovery processes.

[0050] The leached residue is used in the subsequent nickel and cobalt recovery process.

[0051] (3) Recovery of molybdenum, tungsten and vanadium

[0052] This step includes alkaline extraction, washing, stripping agent preparation, stripping and other processes.

[0053] 1) Molybdenum and tungsten extraction

[0054] The leachate obtained in step (2) is sent to an extraction tank, and after multi-stage countercurrent extraction, the molybdenum in the leachate is extracted first; the impurities phosphorus, silicon and most of the vanadium remain in the raffinate; if there is tungsten in the solution, it is extracted together with the molybdenum. The loaded organic phase is washed with pure water, the washing water is combined with the raffinate, and the washed loaded organic phase is subjected to multi-stage countercurrent stripping to obtain a molybdenum-containing stripping solution and an organic phase after stripping.

[0055] 2) Extraction to remove vanadium: The molybdenum-containing stripping solution obtained by molybdenum-tungsten extraction is first placed in a stripping solution storage tank for deoiling, and then evaporated and concentrated in a multi-effect evaporator to cause hybridization reaction between the molybdate and vanadate therein; after multi-stage countercurrent extraction, the vanadium removal rate is more than 99%, and the V2O5 concentration in the raffinate can be reduced to below 0.01g / L.

[0056] 3) Molybdenum and tungsten separation: The raffinate mainly contains molybdate and tungstate. Different separation methods are determined according to the molar ratio of molybdenum to tungsten:

[0057] A. When the molybdenum content is close to the tungsten content, that is, the molar ratio of the two is 0.2-5: the efficiency of direct extraction to remove tungsten is low, and evaporation and concentration are used first to make the tungsten with a higher content crystallize out in the form of ammonium paratungstate. At this time, the ammonium paratungstate crystals still contain a small amount of ammonium molybdate, which needs to be further removed through the dissolution-ion exchange step, and then evaporated and crystallized to obtain pure ammonium paratungstate products;

[0058] At the same time, the concentrated mother liquor in the first step of evaporation and concentration is mainly ammonium molybdate (containing a small amount of ammonium paratungstate). After the mother liquor is extracted to remove tungsten, it is evaporated and crystallized to obtain a pure ammonium molybdate product.

[0059] B. When the molybdenum content is much greater than the tungsten content, that is, the molar ratio of the two is greater than 5: the tungsten can be directly removed by extraction, and then evaporated and crystallized to obtain pure ammonium molybdate products;

[0060] C. When the molybdenum content is much smaller than the tungsten content, that is, the molar ratio of the two is less than 0.2: the molybdenum can be directly removed by ion exchange, and then evaporated and crystallized to obtain pure ammonium paratungstate product.

[0061] (4) Ammonium molybdate and ammonium paratungstate crystals

[0062] The ammonium molybdate solution is pumped to the crystallizer, and the molybdenum in the solution is crystallized in the form of ammonium dimolybdate through evaporation concentration-cooling crystallization. After crystallization, the slurry is filtered through a bucket filter to obtain wet MSA and evaporated crystallization mother liquor. The wet MSA is transferred to the drying process, and the evaporated crystallization mother liquor flows into the mother liquor storage tank. The reaction is as follows:

[0063] (NH4)2MoO4+H2O=(NH4)2MoO7·2H2O+2NH3.

[0064] The evaporated crystallization mother liquor is pumped to the acid precipitation crystallization kettle, sulfuric acid is added in the crystallization kettle while stirring, and the pH is adjusted to 2-3. The molybdenum in the solution will be crystallized in the form of ammonium tetramolybdate, and the wet ammonium tetramolybdate and crystallization mother liquor are obtained by filtering through a tipping bucket filter. The reaction is as follows:

[0065] 4(NH4)2MoO4+3H2SO4=(NH4)2Mo4O 13 ·2H2O+3(NH4)2SO4+H2O.

[0066] The ammonium tetramolybdate obtained by acid precipitation is dissolved in a re-dissolution reactor to obtain an ammonium molybdate solution which is returned to the evaporation and crystallization process, and the mother liquor of acid precipitation enters the recovery process.

[0067] (5) Vanadium precipitation

[0068] The residual solution from molybdenum extraction enters the vanadium precipitation reactor. When pH=8-9, the vanadium in the solution is mainly in the form of V4O 12 4- (VO3 - ) exists in the form of. When (NH4)2SO4 is added to the vanadium solution, a double decomposition reaction will occur, and the reaction formula is as follows:

[0069] 2NaVO3+(NH4)2SO4=2NH4VO3+Na2SO4.

[0070] In this process, factors such as the amount of ammonium salt added (ammonium addition coefficient) and the pH value of vanadium precipitation are controlled to obtain white or light yellow ammonium metavanadate (PFSA) crystals.

[0071] (6) Nickel and cobalt recovery (acid leaching-filter pressing-purification)

[0072] The leached residue obtained in step (2) mainly contains nickel and cobalt, and needs to be subjected to acid leaching to recover nickel and cobalt.

[0073] After acidic leaching with a sulfuric acid solution of about 10% concentration at normal pressure and temperature, nickel ions and cobalt ions are mainly present in the leaching solution, which is filtered, separated, washed and purified to obtain a solution containing nickel and cobalt with relatively less impurities.

[0074] (7) Cobalt extraction

[0075] The leaching solution obtained in step (6) is extracted with a cobalt extractant, and then stripped, evaporated and crystallized to obtain a cobalt sulfate product.

[0076] (8) Nickel extraction

[0077] The raffinate obtained in step (7) is extracted with a nickel extractant, and then stripped, evaporated and crystallized to obtain a nickel sulfate product.

[0078] Among them, in order to save the cost of extraction reagents, the extraction of cobalt and nickel uses the following extraction agents for different cobalt-nickel ratios: when the Co / Ni content is greater than 1 / 5, the selected extraction agent is P204; when 1 / 10 is less than the Co / Ni content and less than 1 / 5, the selected extraction agent is P507; when the Co / Ni content is less than 1 / 10, the selected extraction agent is Cyanex272.

[0079] In order to ensure product purity and separation effect while taking into account the cost of use, different extraction agents are selected according to the above conditions.

[0080] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. The embodiments described below are exemplary and are only used to explain the present application, and cannot be interpreted as limiting the present application.

[0081] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0082] The present application is further described in detail below in conjunction with the embodiments and test results.

[0083] Example 1

[0084] This embodiment provides a method for comprehensive utilization of waste catalysts. The object is a waste catalyst containing molybdenum, tungsten, vanadium, nickel and cobalt, with a weight of 100 kg. Among them, the molybdenum content is 5 kg, the tungsten content is 0.5 kg, the vanadium content is 1 kg, the nickel content is 2 kg, and the cobalt content is 1 kg.

[0085] The comprehensive utilization method of the above-mentioned waste catalyst specifically comprises the following steps:

[0086] (1) Oxidation roasting

[0087] The waste catalyst is transferred from the temporary storage to the raw material intermediate warehouse, and the heavy oil and other organic matter on the surface of the waste catalyst is removed by direct combustion in a rotary kiln. The combustion temperature is 65°C and the roasting time is 2h.

[0088] The flue gas generated by the combustion of heavy oil on the surface of the waste catalyst enters the secondary combustion chamber and is secondary burned with natural gas as fuel. The combustion temperature is 1100℃ and the residence time is greater than 2 seconds, so that the flue gas is fully burned. The flue gas after the secondary high-temperature combustion is desulfurized using the double alkali method and discharged through the exhaust pipe to meet the standards.

[0089] (2) Ball milling-pressure alkali leaching

[0090] The spent catalyst treated in step (1) is transported to a silo, and then enters a wet ball mill from the silo for wet ball milling. The milled slurry flows by gravity to a batching tank, and then 700 kg of water and 300 kg of alkali (150 kg each of sodium hydroxide and sodium carbonate) are added. The slurry is then pumped to a leaching kettle for heating and leaching, and the leached residue is discharged.

[0091] The leachate flows by gravity into the leachate storage tank and is pumped to the subsequent molybdenum, tungsten and vanadium recovery processes.

[0092] The leached residue is used in the subsequent nickel and cobalt recovery process.

[0093] (3) Recovery of molybdenum, tungsten and vanadium

[0094] 1) Molybdenum and tungsten extraction

[0095] The leachate obtained in step (2) is sent to an extraction tank, and after multi-stage countercurrent extraction, the molybdenum in the leachate is extracted first; the impurities phosphorus, silicon and most of the vanadium remain in the raffinate; if there is tungsten in the solution, it is extracted together with the molybdenum. The loaded organic phase is washed with pure water, the washing water is combined with the raffinate, and the washed loaded organic phase is subjected to multi-stage countercurrent stripping to obtain a molybdenum-containing stripping solution and an organic phase after stripping.

[0096] 2) Extraction to remove vanadium: The molybdenum-containing stripping solution obtained by molybdenum-tungsten extraction is first placed in a stripping solution storage tank for deoiling, and then evaporated and concentrated in a multi-effect evaporator to cause hybridization reaction between the molybdate and vanadate therein; after multi-stage countercurrent extraction, the vanadium removal rate is more than 99%, and the V2O5 concentration in the raffinate can be reduced to below 0.01g / L.

[0097] 3) Molybdenum and tungsten separation: The raffinate mainly contains molybdate and tungstate. Different separation methods are determined according to the molar ratio of molybdenum to tungsten:

[0098] A. When the molybdenum content is close to the tungsten content, the efficiency of direct extraction to remove tungsten is low. Evaporation and concentration are used first to make the tungsten with a higher content crystallize in the form of ammonium paratungstate. At this time, the ammonium paratungstate crystals still contain a small amount of ammonium molybdate, which needs to be further removed through the dissolution-ion exchange step, and then evaporation and crystallization can obtain pure ammonium paratungstate products;

[0099] At the same time, the concentrated mother liquor in the first step of evaporation and concentration is mainly ammonium molybdate (containing a small amount of ammonium paratungstate). After the mother liquor is extracted to remove tungsten, it is evaporated and crystallized to obtain pure ammonium molybdate product;

[0100] B. When the molybdenum content is much greater than the tungsten content, the tungsten can be directly removed by extraction, and then evaporated and crystallized to obtain pure ammonium molybdate products;

[0101] C. When the molybdenum content is much smaller than the tungsten content, the ion exchange method can be used to directly remove the molybdenum. After the molybdenum is removed, evaporation and crystallization are performed to obtain pure ammonium paratungstate products.

[0102] In this embodiment, the molybdenum content is 5kg and the tungsten content is 0.5kg, which belongs to Class B. That is, when the molybdenum content is much greater than the tungsten content, the tungsten can be directly removed by extraction, and then evaporated and crystallized to obtain a pure ammonium molybdate product.

[0103] (4) Ammonium molybdate and ammonium paratungstate crystals

[0104] The ammonium molybdate solution is pumped to the crystallizer, and the molybdenum in the solution is crystallized in the form of ammonium dimolybdate through evaporation concentration-cooling crystallization. After crystallization, the slurry is filtered through a bucket filter to obtain wet MSA and evaporated crystallization mother liquor. The wet MSA is transferred to the drying process, and the evaporated crystallization mother liquor flows into the mother liquor storage tank.

[0105] The evaporated crystallization mother liquor is transported to the acid precipitation crystallization kettle by a pump, sulfuric acid is added to the crystallization kettle while stirring, and the pH is adjusted to 2-3. The molybdenum in the solution will crystallize out in the form of ammonium tetramolybdate, and the wet ammonium tetramolybdate and crystallization mother liquor are obtained by filtering through a tipping bucket filter.

[0106] The ammonium tetramolybdate obtained by acid precipitation is dissolved in a re-dissolution reactor to obtain an ammonium molybdate solution which is returned to the evaporation and crystallization process, and the mother liquor of acid precipitation enters the recovery process.

[0107] Finally, the following products were obtained: 10 kg of ammonium molybdate product; 0.81 kg of ammonium paratungstate product.

[0108] The details are as follows:

[0109] The molecular weight of ammonium molybdate is 196, and the vanadium content is 48.98%. The raw material molybdenum is 5kg, and the yield is 98%, i.e. 4.9kg, corresponding to the mass of ammonium metavanadate is 10kg.

[0110] The molecular weight of ammonium paratungstate is 3132, and the tungsten content is 58.75%. The raw material tungsten is 0.5kg, and the yield is 95%, i.e. 0.475kg, corresponding to the mass of ammonium paratungstate is 0.81kg.

[0111] (5) Vanadium precipitation

[0112] The residual solution from molybdenum extraction enters the vanadium precipitation reactor. When pH=8-9, the vanadium in the solution is mainly in the form of V4O12 4- (VO3 - ) exists in the form of. Adding (NH4)2SO4 to the vanadium solution will cause a double decomposition reaction. In this process, the amount of ammonium salt added (ammonium addition coefficient) and the pH value of vanadium precipitation are controlled to obtain white or light yellow ammonium metavanadate (PFSA) crystals, 2.2kg.

[0113] The details are as follows:

[0114] The molecular weight of ammonium metavanadate is 117, and the vanadium content is 43.59%;

[0115] The raw material vanadium is 1 kg, and the yield is 96%, i.e. 0.96 kg, corresponding to the mass of ammonium metavanadate 2.2 kg.

[0116] (6) Nickel and cobalt recovery (acid leaching-filter pressing-purification)

[0117] The leached residue obtained in step (2) mainly contains nickel and cobalt, and needs to be subjected to acid leaching to recover nickel and cobalt.

[0118] After acidic leaching with a sulfuric acid solution of about 10% concentration at normal pressure and temperature, nickel ions and cobalt ions are mainly present in the leaching solution, which is filtered, separated, washed and purified to obtain a solution containing nickel and cobalt with relatively less impurities.

[0119] (7) Cobalt extraction

[0120] The leaching solution obtained in step (6) was extracted with a cobalt extractant (P204), and then subjected to stripping, evaporation and crystallization to obtain a cobalt sulfate product, 2.55 kg.

[0121] The details are as follows:

[0122] Cobalt sulfate molecular weight 155, cobalt content 38%;

[0123] The raw material cobalt is 1 kg, and the yield is 97%, i.e. 0.97 kg, corresponding to a mass of 2.55 kg of cobalt sulfate.

[0124] (8) Nickel extraction

[0125] The raffinate obtained in step (7) was extracted with a nickel extractant (P204), and after back extraction, evaporation and crystallization, a nickel sulfate product of 5.16 kg was obtained.

[0126] The details are as follows:

[0127] Nickel sulfate molecular weight 154, nickel content 37.6%;

[0128] The raw material nickel is 2kg, and the yield is 97%, i.e. 1.94kg, corresponding to a mass of 5.16kg nickel sulfate.

[0129] Comparative Example

[0130] This comparative example provides a method for comprehensive utilization of waste catalysts. The object is a waste catalyst containing molybdenum, tungsten, vanadium, nickel and cobalt, with a weight of 100 kg. Among them, the molybdenum content is 5 kg, the tungsten content is 0.5 kg, the vanadium content is 1 kg, the nickel content is 2 kg, and the cobalt content is 1 kg.

[0131] The above method specifically comprises the following steps:

[0132] Directly using 10% concentration of sulfuric acid for leaching, the leaching solution is used to extract and separate molybdenum, tungsten, vanadium, nickel and cobalt, with corresponding recovery rates of 85%, 88%, 82%, 90% and 91% respectively; the product purity cannot meet the standard.

[0133] From the above, it can be seen that the comprehensive utilization method of waste catalysts provided by the present application has significantly better recovery efficiency of each metal than the method in the prior art in the comparative example. Among them, the recovery rate of each metal in the comprehensive utilization method of the present application is greater than 95%, and the purity meets the relevant product standards. At the same time, in the ammonium molybdate solution, the vanadium and tungsten removal rate reaches more than 99%, the vanadium and tungsten concentration is less than 0.01g / L, and the molybdenum direct recovery rate is greater than 95%.

[0134] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for comprehensive utilization of waste catalysts, characterized in that: The method specifically comprises the following steps: The waste catalyst is subjected to oxidation roasting, wet ball milling, and pressure leaching in sequence to obtain a first leaching solution and leaching residue; the first leaching solution is used for recovering molybdenum, tungsten, and vanadium; the leaching residue is used for recovering nickel and cobalt; For the first leachate: The first leachate is extracted by multi-stage countercurrent extraction, molybdenum and tungsten are extracted therein, and then stripping solution containing molybdenum and tungsten is obtained after stripping; the stripping solution is sequentially placed for deoiling, evaporated and concentrated, and subjected to multi-stage countercurrent extraction to remove vanadium, to obtain a raffinate and a stripping solution containing vanadium; The raffinate mainly contains molybdate and tungstate. Different separation methods are determined according to the molar ratio of molybdenum to tungsten, specifically: A. When the molybdenum content is close to the tungsten content, that is, the molar ratio of the two is 0.2-5: first evaporation and concentration are adopted to make the tungsten with a larger content crystallize out in the form of ammonium paratungstate. At this time, the ammonium paratungstate crystals still contain a small amount of ammonium molybdate, which needs to be further removed by dissolution-ion exchange steps, and then evaporated and crystallized to obtain a pure ammonium paratungstate product; at the same time, the concentrated mother liquor in the first step of evaporation and concentration is mainly ammonium molybdate, containing a small amount of ammonium paratungstate. The concentrated mother liquor is extracted to remove tungsten and then evaporated and crystallized to obtain a pure ammonium molybdate product; B. When the molybdenum content is much greater than the tungsten content, that is, the molar ratio of the two is greater than 5: directly use the extraction method to remove tungsten, and then evaporate and crystallize after tungsten removal to obtain pure ammonium molybdate product; C. When the molybdenum content is much less than the tungsten content, that is, the molar ratio of the two is less than 0.2: directly use ion exchange to remove molybdenum, and then evaporate and crystallize after removing molybdenum to obtain pure ammonium paratungstate product; For the leached residue: the leached residue is subjected to acid leaching with a sulfuric acid solution at normal temperature and pressure to obtain a second leaching solution; a cobalt extractant and a nickel extractant are used for extraction respectively, and a cobalt sulfate product and a nickel sulfate product are obtained after back extraction, evaporation and crystallization.

2. The method for comprehensive utilization of waste catalyst according to claim 1, characterized in that: The spent catalyst contains any one or more of molybdenum, tungsten, vanadium, nickel and cobalt.

3. The method for comprehensive utilization of waste catalyst according to claim 1, characterized in that: The V2O5 concentration in the raffinate can be reduced to below 0.01 g / L.

4. The method for comprehensive utilization of waste catalyst according to claim 1, characterized in that: The vanadium removal rate in the raffinate reaches more than 99%.

5. The method for comprehensive utilization of waste catalyst according to claim 1, characterized in that: The vanadium-containing stripping solution is added with (NH4)2SO4 under the condition of pH=8-9 to cause double decomposition reaction to obtain ammonium metavanadate crystals.

6. The method for comprehensive utilization of waste catalysts according to claim 1, characterized in that: The second leachate is first extracted with the cobalt extractant, and a cobalt sulfate product is obtained after back extraction, evaporation and crystallization; and the raffinate obtained after the back extraction is extracted with a nickel extractant, and a nickel sulfate product is obtained after back extraction, evaporation and crystallization.

7. The method for comprehensive utilization of waste catalyst according to claim 1, characterized in that: According to the nickel and cobalt contents in the second leaching solution, a corresponding extractant is selected.

8. The method for comprehensive utilization of waste catalysts according to claim 7, characterized in that: When the Co / Ni content is greater than 1 / 5, the selected extractant is P204; when 1 / 10 is less than the Co / Ni content and less than 1 / 5, the selected extractant is P507; when the Co / Ni content is less than 1 / 10, the selected extractant is Cyanex272.

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