Comprehensive utilization method of flue gas electric precipitation ash

Abstract

The invention relates to the technical field of glass melting furnace flue gas treatment, and discloses a comprehensive utilization method of flue gas electric precipitation ash. The comprehensive utilization method comprises the following steps: mixing the flue gas electric precipitation ash with water to obtain ash slurry; an oxidizing agent is added into the soot slurry, the soot slurry is adjusted to be alkaline, then a first reaction and solid-liquid separation are conducted under the first heating condition, and a vanadium-containing solution and filter residues are obtained; adjusting the vanadium-containing solution to be acidic by adopting a sulfuric acid solution, then carrying out a second reaction under a second heating condition, and carrying out solid-liquid separation to obtain vanadium pentoxide and filtrate; adjusting the filtrate to be neutral, and treating the neutral solution through a resin column to obtain a sodium sulfate solution; and performing evaporative crystallization on the sodium sulfate solution to obtain anhydrous sodium sulfate. According to the method, vanadium, sodium and sulfate radicals in the flue gas electric precipitation ash are recycled, vanadium pentoxide is obtained, meanwhile, a sodium sulfate product with the high purity is obtained, and high economic benefits and environmental benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas treatment in glass furnaces, and particularly to a comprehensive utilization method for the electric dust removal ash of flue gas. Background Art

[0002] During the production process of melting and burning in glass factories, flue gas is generated. The main pollutants in the flue gas are particulate matter, nitrogen oxides, and sulfur dioxide. Among them, petroleum coke contains heavy metal elements such as vanadium and nickel. In glass factories using petroleum coke as fuel, vanadium pentoxide and nickel trioxide are generated after combustion. Therefore, the flue gas contains vanadium pentoxide, nickel trioxide, and heavy metal oxides. The electric dust removal ash of glass factories is the dust collected from the flue gas through an electrostatic precipitator. These dusts have complex compositions, mainly composed of fly ash from fuel combustion and fly dust from glass raw materials. The fly dust of glass raw materials contains silicon dioxide, sodium oxide, calcium oxide, etc., and the fly ash contains heavy metals such as lead and chromium and other trace harmful substances. Due to the different fuels used in glass factories, there are certain differences in the composition and properties of the electric dust removal ash of flue gas generated by different glass factories or even different fuels in the same glass factory.

[0003] However, at present, the electric dust removal ash of flue gas in glass factories has not been effectively utilized for resource recovery, and there are many technical problems. On the one hand, its composition is complex and fluctuates greatly, which brings great challenges to the subsequent treatment process. Some existing treatment technologies are often designed for materials with relatively single components and are difficult to adapt to the complex and changeable characteristics of electric dust removal ash, resulting in low treatment efficiency and unstable product quality. On the other hand, from the perspective of separation and recovery, it is very difficult to efficiently separate and purify the valuable components in it. For example, for the heavy metals in it, the traditional separation methods have high costs, low recovery rates, and are prone to secondary pollution; for some useful oxides, there is also a lack of economically feasible large-scale enrichment and reuse technologies. These technical bottlenecks limit the resource utilization process of the electric dust removal ash of flue gas in glass factories, and new technological breakthroughs are urgently needed to achieve its effective utilization. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problem that the valuable metals in the electric dust removal ash of flue gas in the prior art have not been effectively utilized, and provide a comprehensive utilization method for the electric dust removal ash of flue gas. This method adopts a simple process, fully recovers vanadium and nickel in the electric dust removal ash of flue gas, obtains nickel-vanadium concentrate slag and commercially available vanadium pentoxide products, and at the same time fully recovers sodium and sulfate radicals in the electric dust removal ash of flue gas to obtain a sodium sulfate product with a relatively high purity, which has high economic benefits and also alleviates the environmental pressure, having high environmental benefits.

[0005] To achieve the above purpose, the present invention provides a comprehensive utilization method for the electric dust removal ash of flue gas, and this comprehensive utilization method includes:

[0006] Mix the flue gas electric dust removal ash with water to obtain an ash slurry;

[0007] Add an oxidant to the ash slurry, adjust the ash slurry to be alkaline, and then carry out a first reaction under the first heating condition, followed by solid-liquid separation to obtain a vanadium-containing solution and a filter residue;

[0008] Adjust the vanadium-containing solution to be acidic with a sulfuric acid solution, and then carry out a second reaction under the second heating condition, followed by solid-liquid separation to obtain vanadium pentoxide and a filtrate;

[0009] Adjust the filtrate to be neutral, and then treat the obtained neutral solution through a resin column to obtain a sodium sulfate solution;

[0010] Carry out evaporation crystallization on the sodium sulfate solution to obtain anhydrous sodium sulfate.

[0011] Preferably, the flue gas electric dust removal ash contains 46-55 wt% of sulfur oxides, 10-15 wt% of vanadium pentoxide, 8-12 wt% of sodium oxide, and 3-5 wt% of nickel oxide.

[0012] Preferably, the weight ratio of the dosage of the flue gas electric dust removal ash to water is 1:(3-8).

[0013] Preferably, the oxidant is hydrogen peroxide and / or sodium hypochlorite.

[0014] Preferably, the dosage of the oxidant is 0.1-0.5 times the weight of the flue gas electric dust removal ash.

[0015] Preferably, use sodium hydroxide to adjust the ash slurry to be alkaline, and the dosage of sodium hydroxide is 0.6-0.9 times the weight of the flue gas electric dust removal ash.

[0016] Preferably, the process of adjusting the ash slurry to be alkaline includes: adjusting the pH value of the ash slurry to 8-9.

[0017] Preferably, the process of adding an oxidant to the ash slurry and adjusting the ash slurry to be alkaline includes: first adjusting the ash slurry to be alkaline, then adding the oxidant, and then continuing to adjust the ash slurry to be alkaline.

[0018] Preferably, the conditions of the first reaction include: the temperature is 60-70 °C and the time is 40-80 min.

[0019] Preferably, the content of V2O7 in the vanadium-containing solution 4- is 2-3 wt%, and the content of sodium sulfate is 15-25 wt%.

[0020] Preferably, the filter residue contains vanadium and nickel, and the total content of vanadium and nickel is 2-3 wt%.

[0021] Preferably, the process of adjusting the vanadium-containing solution to acidic with sulfuric acid solution includes: adjusting the pH value of the vanadium-containing solution to 1.8 - 2.2 with sulfuric acid solution.

[0022] Preferably, the conditions of the second reaction include: the temperature is 85 - 95 °C and the time is 30 - 60 min.

[0023] Preferably, the concentration of sodium sulfate in the filtrate is 18 - 22 wt%, and the concentration of vanadium is 0.01 - 0.02 wt%.

[0024] Preferably, the process of adjusting the filtrate to neutral includes: adjusting the pH value of the filtrate to 6 - 7.

[0025] Preferably, the resin column is a D201 resin column.

[0026] Preferably, the concentration of sodium sulfate in the sodium sulfate solution is 18 - 22 wt%, and the concentration of vanadium < 1 ppm.

[0027] Preferably, the conditions of the evaporation and crystallization include: the temperature is 35 - 50 °C, the pressure is normal pressure, and the time is 100 - 400 min.

[0028] Compared with the prior art, the present invention has at least the following technical effects:

[0029] After obtaining the soot slurry in the method of the present invention, most of the cation and anion impurities in the soot slurry are removed by a specific method first, while most of the vanadium, sulfate radical, and sodium ions are left in the solution. After solid-liquid separation, the impurities are left in the filter residue, and at the same time, the filter residue contains part of vanadium and nickel. Therefore, the filter residue is directly sold as a nickel-vanadium concentrate slag product; then the vanadium-containing solution is subjected to hydrolysis precipitation by a specific method to obtain vanadium pentoxide precipitation, which can be directly sold as crude vanadium pentoxide. The sulfate radical, sodium ions, and a small amount of residual vanadium in the soot slurry enter the filtrate, and a filtrate containing a large amount of sodium sulfate is obtained; then the small amount of residual vanadium in the filtrate is removed by resin to obtain a purified sodium sulfate solution, and sodium sulfate products with a purity of more than 99% can be obtained by evaporation and crystallization. Moreover, the vanadium in the present invention can be recycled 100%, and most of the vanadium is recycled into high-value vanadium pentoxide products. Thus, the present invention realizes the recycling of flue gas electrostatic precipitator ash, turning waste into treasure, having high economic and environmental benefits, and the method is simple in operation, low in cost, and strong in applicability. Description of the Drawings

[0030] Figure 1 is a process schematic diagram of the comprehensive utilization method of the flue gas electrostatic precipitator ash of the present invention. Detailed Embodiments

[0031] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for illustrating and explaining the present invention, and are not used to limit the present invention.

[0032] In the ranges disclosed herein, the endpoints and any values are not limited to the exact 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, between the endpoint values of each range, between the endpoint value of each range and a single point value, and between single point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0033] As Figure 1 shown, a comprehensive utilization method of flue gas electric dust removal ash provided by the present invention includes the following steps:

[0034] Mix the flue gas electric dust removal ash with water to obtain an ash slurry;

[0035] Add an oxidant to the ash slurry, adjust the ash slurry to be alkaline, and then carry out a first reaction under the first heating condition, followed by solid-liquid separation to obtain a vanadium-containing solution and a filter residue;

[0036] Adjust the vanadium-containing solution to be acidic with a sulfuric acid solution, and then carry out a second reaction under the second heating condition, followed by solid-liquid separation to obtain vanadium pentoxide and a filtrate;

[0037] Adjust the filtrate to be neutral, and then treat the obtained neutral solution through a resin column to obtain a sodium sulfate solution;

[0038] Evaporate and crystallize the sodium sulfate solution to obtain anhydrous sodium sulfate.

[0039] The flue gas electric dust removal ash described in the present invention mainly comes from the electric dust removal ash collected by the electric dust removal purification of flue gas in a glass factory. In one embodiment, the flue gas electric dust removal ash mainly contains 46 - 55 wt% of sulfur oxides, 10 - 15 wt% of vanadium pentoxide, 8 - 12 wt% of sodium oxide, and 3 - 5 wt% of nickel oxide. Among them, the sulfur oxides mainly include sulfates, metal polysulfates, and other sulfur-containing oxides; nickel mainly exists in the form of nickel sesquioxide and nickel spinel in the flue gas electric dust removal ash.

[0040] In the present invention, the purpose of mixing the flue gas electric dust removal ash with water is to dissolve and leach the components in the flue gas electric dust removal ash to form soluble ions, which is convenient for separating different components subsequently to obtain different products.

[0041] In the present invention, the ash slurry contains Fe 2+ 、Fe 3+, Ni 2+ , Ca 2+ , Mg 2+ , Al 3+ and other cations and SiO3 2- , PO4 3- , SO4 2- and other anions; In the flue gas electric dust removal ash, part of the Fe 2+ , Fe 3+ , Ni 2+ , Ca 2+ , Mg 2+ , Al 3+ and other cations and part of SiO3 2- , PO4 3- , SO4 2- and other anions form salts, and the other part exists in the form of higher valence oxides, and the composition is relatively complex.

[0042] When the flue gas electric dust removal ash is mixed with water, vanadium exists in the form of in the ash slurry, sulfur exists in the form of SO4 2- , and sodium exists in the form of Na + .

[0043] In some embodiments, the weight ratio of the amount of the flue gas electric dust removal ash to the amount of water can be 1:(3-8). Limiting the usage ratio of the flue gas electric dust removal ash to water within this range can effectively dissolve the components of the flue gas electric dust removal ash and improve the recovery rates of elements such as vanadium and sodium.

[0044] In the present invention, an oxidant is added to the ash slurry, and the ash slurry is adjusted to be alkaline, and then a first reaction is carried out under the first heating condition, followed by solid-liquid separation to obtain a vanadium-containing solution and a filter residue. The purpose of this step is to separate vanadium, sulfate, and sodium from other elements, and remove the Fe 2+ , Fe 3+ , Ni 2+ , Ca 2+ , Mg 2+ , Al 3+ and other cation impurities and SiO3 2- , PO4 3- and other anion impurities to achieve primary purification and facilitate the subsequent obtaining of vanadium pentoxide and sodium sulfate products.

[0045] In the present invention, adding an oxidant to the ash slurry can oxidize Fe 2+ to Fe 3+ , facilitating Fe 3+, hydroxide precipitate is generated. In one embodiment, the oxidant is hydrogen peroxide and / or sodium hypochlorite, preferably hydrogen peroxide. In another embodiment, the dosage of the oxidant is 0.1 - 0.5 times the weight of the flue gas electrostatic precipitator ash.

[0046] In the present invention, the purpose of adjusting the soot slurry to be alkaline is to make Fe 3+ , Ni 2+ , Ca 2+ , Mg 2+ , Al 3+ and other cationic impurities and SiO3 2- , PO4 3- and other anionic impurities generate precipitates under heating conditions, so as to be separated from soluble vanadium, sulfate radical, and sodium.

[0047] In some embodiments, the process of adjusting the soot slurry to be alkaline includes: adjusting the pH value of the soot slurry to 8 - 9. Adjusting the pH value of the soot slurry to this range can improve the precipitation effect of impurity ions and the separation effect of impurity ions from soluble vanadium, sulfate radical, and sodium.

[0048] In a more preferred embodiment, adding an oxidant to the soot slurry and the process of adjusting the soot slurry to be alkaline include: first adjusting the soot slurry to be alkaline, then adding the oxidant, and then continuing to adjust the soot slurry to be alkaline. By adopting this method, the impurity ions can achieve stepwise precipitation, that is, first adjusting the soot slurry to be alkaline can make the ions that are easy to precipitate precipitate first, then adding the oxidant, and then continuing to adjust the soot slurry to be alkaline can make the impurity ions that are difficult to precipitate continue to precipitate under subsequent heating conditions, so that each impurity ion can achieve orderly precipitation and improve the impurity removal effect.

[0049] In some embodiments, sodium hydroxide is used to adjust the soot slurry to be alkaline, and the dosage of sodium hydroxide is 0.6 - 0.9 times the weight of the flue gas electrostatic precipitator ash. Using sodium hydroxide to adjust the pH of the soot slurry will not introduce impurities and has a low price. The dosage of sodium hydroxide is the total dosage of sodium hydroxide used to adjust the soot slurry.

[0050] In some embodiments, the conditions of the first reaction include: the temperature is 60 - 70 °C and the time is 40 - 80 min. In the present invention, after the first reaction, the vanadium is soluble vanadium V2O7 4- , while Fe 2+ , Ni 2+ , Mg 2+ and other cations produce hydroxide precipitates, and PO4 3- and Ca 2+Generate insoluble Ca3(PO4)2 precipitate, SiO3 2- and Al 3+ Generate Al2(SiO3)3 precipitate, and the main reactions that occur are as follows:

[0051] 2Fe 2+ +H2O2+2H + →2Fe 3+ +2H2O

[0052] Fe 3+ +3OH - +2H + →Fe(OH)3↓

[0053] Mg 2+ +2OH - →Mg(OH)2↓

[0054] Ni 2+ +2OH - →Ni(OH)2↓

[0055] 3Ca 2+ +2PO4 3- →Ca3(PO4)3↓

[0056] 2Al 3+ +3SiO3 2- →Al2(SiO3)3↓。

[0057] In the present invention, the method for solid-liquid separation after the first reaction can be pressure filtration. In some embodiments, the filter residue obtained contains vanadium and nickel, and the total content of vanadium and nickel (vanadium and nickel refer to elements) is 2-3 wt%, and it can be directly sold as a nickel-vanadium concentrate slag product and used as a raw material for smelting nickel matte or for extracting vanadium by pyrometallurgical processes. In other embodiments, the content of V2O7 4- (soluble vanadium) in the obtained vanadium-containing solution is 2-3 wt%, and the content of sodium sulfate is 15-25 wt%.

[0058] In the present invention, the vanadium-containing solution is adjusted to be acidic with a sulfuric acid solution, and then a second reaction is carried out under the second heating condition, followed by solid-liquid separation to obtain vanadium pentoxide and a filtrate. The purpose of this step is to enable V2O7 4- to precipitate through hydrolysis under acidic environment and heating conditions (for example, it can be steam heating) to obtain vanadium pentoxide precipitate, and the vanadium pentoxide crude product can be obtained after separation. In this step, when the vanadium-containing solution is neutralized with acid for hydrolysis precipitation of vanadium, the form of vanadium gradually changes, and the reactions are as follows:

[0059]

[0060] In one embodiment, the process of adjusting the vanadium-containing solution to be acidic with sulfuric acid solution includes: adjusting the pH value of the vanadium-containing solution to 1.8 - 2.2 with sulfuric acid solution. Adjusting the pH value of the vanadium-containing solution to this range can form vanadium pentoxide precipitate more stably and improve the recovery rate of vanadium. Further, the sulfuric acid solution is a dilute sulfuric acid solution, and the concentration can be 20wt%.

[0061] Adjusting the pH value of the vanadium-containing solution with sulfuric acid solution can supplement sulfate ions, which is convenient for forming more sodium sulfate products during the subsequent evaporation and crystallization process and improving the recovery rate of sodium. In the present invention, since the flue gas electrostatic precipitator ash contains more sulfate and sodium, only a small amount of sulfate ions need to be added in this step to achieve the full recovery of sulfate and sodium ions.

[0062] In some embodiments, the temperature of the second reaction is 85 - 95°C. During the heat preservation period, through regular analysis, the reaction ends until the concentration of vanadium in the vanadium-containing solution is reduced to between 0.01 - 0.02%. At this time, the solution is colorless or slightly light yellow. In some embodiments, the reaction time required for the second reaction to reduce the concentration of vanadium in the vanadium-containing solution to 0.01 - 0.02% is 30 - 60 min.

[0063] In the present invention, the method of solid-liquid separation after the second reaction can be pressure filtration. In the vanadium pentoxide solid obtained by solid-liquid separation, the purity of V2O5 can reach 80% and it can be directly sold as crude vanadium pentoxide. The concentration of sodium salts in the filtrate obtained by solid-liquid separation basically remains unchanged. At this time, the filtrate is mainly a sodium sulfate solution, but contains a small amount of vanadium oxygen ion impurities. In some embodiments, the concentration of sodium sulfate in the filtrate can be 18 - 22wt%, and the concentration of vanadium element can be 0.01 - 0.02wt%.

[0064] In the present invention, the filtrate is adjusted to be neutral, and then the obtained neutral solution is processed through a resin column to obtain a sodium sulfate solution. The purpose of this step is to further remove a small amount of vanadium in the sodium sulfate solution, which is convenient for obtaining sodium sulfate crystals with higher purity by subsequent evaporation and crystallization.

[0065] In one embodiment, the process of adjusting the filtrate to be neutral includes: adjusting the pH value of the filtrate to 6 - 7. In the present invention, before the resin column treatment, adjusting the pH value of the filtrate to be neutral first can achieve acid-base balance, make the sulfate and sodium reach balance, which is convenient for better crystallization of sodium sulfate, and at the same time prevent equipment corrosion.

[0066] In the present invention, the function of the resin column is to prevent vanadium from passing through, thereby removing vanadium in the filtrate. In a preferred embodiment, the resin column is a D201 resin column; using this resin column can improve the vanadium removal effect.

[0067] In a specific embodiment, the process of treating the obtained neutral solution through a resin column includes: passing the solution through a D201 resin column, controlling the flow rate during the process, and detecting at the outlet until the sodium sulfate solution at the outlet is colorless and transparent and no vanadium ions can be detected, which is considered qualified. At this time, the concentration of vanadium is less than <1 ppm, and the resin column treatment process ends. In one embodiment, the concentration of sodium sulfate in the sodium sulfate solution is 18-22 wt%, and the concentration of vanadium is <1 ppm.

[0068] In the present invention, the evaporation and crystallization are carried out in a double-effect evaporation system. In one embodiment, the conditions for the evaporation and crystallization include: the temperature is 35-50 °C, the pressure is atmospheric pressure, and the time is 100-400 min. The crystalline product obtained by evaporation and crystallization is anhydrous sodium sulfate, and the purity can reach more than 99%. The condensed water generated during the evaporation process can be recycled to achieve zero discharge.

[0069] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited thereto.

[0070] In the following examples, unless otherwise specified, the raw materials used are common commercially available products.

[0071] Example 1

[0072] The flue gas electric dust removal ash used in this example contains 50 wt% of sulfur oxides (including iron sulfate, sodium sulfate, calcium sulfate, magnesium sulfate, sodium thiosulfate), 12 wt% of vanadium pentoxide, 10 wt% of sodium oxide, and 3 wt% of nickel oxide (including nickel sesquioxide and nickel tetroxide).

[0073] S1. Dissolution and leaching

[0074] Weigh 2 tons of flue gas electric dust removal ash and dissolve it in 10 tons of water, and stir evenly to obtain an ash slurry.

[0075] S2. Primary purification

[0076] The solution containing Fe 2+ 、Fe 3+ 、Ni 2+ 、Ca 2+ 、Mg 2+ 、Al 3+ and other cations and SiO3 2- 、PO4 3- 、SO4 2-The soot slurry containing anions is pumped into a stirring tank, and NaOH is added to adjust the pH value of the soot slurry to 8.5. About 400 kg of hydrogen peroxide is added, and the pH value of the soot slurry is continuously adjusted to stabilize it at 8.5. Heating is started, and the temperature is controlled within 65 °C for continuous reaction for 1 hour. After the ripening reaction ends, Fe 2+ , Ni 2+ , Mg 2+ and other cations form hydroxide precipitates, PO4 3- and Ca 2+ form insoluble Ca3(PO4)2 precipitate, SiO3 2- and Al 3+ form Al2(SiO3)3 precipitate. This process consumes 1500 kg of solid NaOH.

[0077] S3. Filtration and separation of the filtrate

[0078] The preliminarily purified slurry is subjected to solid-liquid separation through a filter press to obtain 2000 kg of filter residue with a water content of 60%. The filter residue contains about 2.5% of vanadium and nickel, and is directly sold as a nickel-vanadium concentrate slag product. The recovery rate of vanadium in the filter residue is about 20%. The separated vanadium-containing solution is light yellow, and the content of soluble vanadium V2O7 4- in the solution is 2.5%, and the content of sodium sulfate is 20%.

[0079] S4. Hydrolysis precipitation of the filtrate

[0080] The above vanadium-containing solution is added to a purification stirring tank, and the pH value of the solution is adjusted to 2.0 with 20% dilute sulfuric acid, heated to 90 °C and kept warm. Through regular analysis, until the vanadium concentration in the solution is reduced to between 0.015%, the purification reaction ends, and the reaction time is about 40 minutes. At this time, the solution is colorless or slightly light yellow, and finally hydrated vanadium pentoxide brick-red precipitate, that is, red cake, is produced. In this step, when the vanadium-containing solution is hydrolyzed and precipitated by adding acid for neutralization, the form of vanadium gradually changes, and the reaction is as follows:

[0081]

[0082] S5. Filtration and separation

[0083] The above solution containing red cake is filtered through a filter press to separate the red cake and the filtrate. The total weight of the separated red cake is 2000 kg, and the water content is 60%. The purity of V2O5 in the red cake solid is about 80% (the recovery rate of vanadium in the red cake is about 80%). At this time, the filtrate contains 20% wt of sodium sulfate but contains 0.015% of vanadium oxygen ion impurities.

[0084] S6. Purification and vanadium removal of the filtrate

[0085] Adjust the pH value of the filtrate to 6.5, then pass the filtrate through a D201 resin column and conduct detection at the outlet. The sodium sulfate solution at the outlet is colorless and transparent, and no vanadium ions can be detected. At this time, the concentration of vanadium is less than <1 ppm, and the concentration of sodium sulfate is about 20%. This sodium sulfate solution can be used as the evaporation crystallization preparation solution.

[0086] S7. Evaporation Crystallization

[0087] Pump the sodium sulfate solution into a double-effect evaporation system for evaporation crystallization. Control the crystallization temperature at 40 °C and the crystallization time at 240 min. The obtained crystalline product is anhydrous sodium sulfate with a purity of 99.5%. The condensed water generated during the evaporation process can be recycled back to the workshop for reuse, achieving zero discharge.

[0088] S8. Centrifugal Drying and Packing

[0089] The centrifugal dryer dries and packs the sodium sulfate crystals.

[0090] In this embodiment, 100% of the vanadium in the flue gas electrostatic precipitator ash is recovered. Among them, a small part of the vanadium enters the filter residue and is directly sold as a nickel-containing vanadium concentrate slag product, and the recovery rate of vanadium in the filter residue is 20%; most of the vanadium enters the high-value product red cake, and the recovery rate of vanadium in the red cake is 80%.

[0091] Example 2

[0092] The flue gas electrostatic precipitator ash used in this embodiment contains 50 wt% of sulfur oxides (including ferric sulfate, sodium sulfate, calcium sulfate, magnesium sulfate, sodium thiosulfate), 15 wt% of vanadium pentoxide, 10 wt% of sodium oxide, and 5 wt% of nickel oxide (including nickel sesquioxide and nickel ferrite).

[0093] S1. Dissolution and Leaching

[0094] Dissolve 2 tons of the weighed flue gas electrostatic precipitator ash in 6 tons of water and stir evenly to obtain an ash slurry.

[0095] S2. Primary Purification

[0096] The solution containing cations such as Fe 2+ 、Fe 3+ 、Ni 2+ 、Ca 2+ 、Mg 2+ 、Al 3+ and anions such as SiO3 2- 、PO4 3- 、SO4 2-The ashed slurry containing anions is pumped into a stirring tank, and NaOH is added to adjust the pH value of the ashed slurry to 8.5. Approximately 400 kg of hydrogen peroxide is added, and the pH value of the ashed slurry is continuously adjusted to stabilize it at 8.5. Heating is started, and the temperature is controlled within 65 °C for continuous reaction for 2 hours. After the ripening reaction ends, Fe 2+ , Ni 2+ , Mg 2+ and other cations form hydroxide precipitates, PO4 3- and Ca 2+ form insoluble Ca3(PO4)2 precipitate, SiO3 2- and Al 3+ form Al2(SiO3)3 precipitate. This process consumes 1500 kg of solid NaOH. If less water is added, the reaction time doubles, and the stability of equipment operation is poor. The pipeline is prone to blockage, the motor load increases, and it is prone to overload.

[0097] S3. Filtration and separation of the filtrate

[0098] The primary purified slurry is subjected to solid-liquid separation through a filter press, obtaining 2000 kg of filter residue with a water content of 60%. The filter residue contains approximately 2.5% vanadium and nickel, and is directly sold as a nickel-vanadium concentrate slag product. The recovery rate of vanadium in the filter residue is approximately 20%. The separated vanadium-containing solution is light yellow, and the content of soluble vanadium V2O7 4- in the solution is 3.7%, and the content of sodium sulfate is 30%.

[0099] S4. Hydrolysis precipitation of the filtrate

[0100] The above-mentioned vanadium-containing solution is added to a purification stirring tank, and the pH value of the solution is adjusted to 2.0 with 20% dilute sulfuric acid, heated to 80 °C and kept warm. Through regular analysis, until the vanadium concentration in the solution is reduced to between 0.015%, the purification reaction ends, and the reaction time is approximately 60 minutes. At this time, the solution is colorless or slightly light yellow, and finally hydrated vanadium pentoxide brick-red precipitate, namely red cake, is produced. In this step, when the vanadium-containing solution is hydrolyzed and precipitated by adding acid for neutralization, the form of vanadium gradually changes, and the reaction is as follows:

[0101]

[0102] S5. Filtration and separation

[0103] The above-mentioned solution containing red cake is filtered through a filter press to separate the red cake and the filtrate. The total weight of the separated red cake is 2000 kg, with a water content of 60%. The purity of V2O5 in the red cake solid is approximately 77% (the recovery rate of vanadium in the red cake is approximately 80%). At this time, the filtrate contains 30% wt of sodium sulfate but contains 0.015% of vanadium oxygen ion impurities.

[0104] S6. Purification of the filtrate to remove vanadium

[0105] Adjust the pH value of the filtrate to 6.5, then pass the filtrate through a D201 resin column and conduct detection at the outlet. The sodium sulfate solution at the outlet is colorless and transparent, and no vanadium ions can be detected. At this time, the concentration of vanadium is less than <1 ppm, and the concentration of sodium sulfate is about 20%. This sodium sulfate solution can be used as a preparation solution for evaporation and crystallization.

[0106] S7. Evaporation and crystallization

[0107] Pump the sodium sulfate solution into a double-effect evaporation system for evaporation and crystallization. Control the crystallization temperature at 40 °C and the crystallization time at 144 min. The crystalline product obtained is anhydrous sodium sulfate with a purity of 99.5%. The condensed water generated during the evaporation process can be recycled back to the workshop for reuse, achieving zero discharge.

[0108] S8. Centrifugal dewatering and packing

[0109] The centrifugal dewatering machine dehydrates and packs the sodium sulfate crystals.

[0110] In this example, the dosage ratio of flue gas electrostatic precipitator ash to water can be 1:3 without affecting the overall product output. However, the high content of sodium sulfate in the filtrate is prone to crystallization in Step S4, which affects the quality of the red cake (vanadium pentoxide). In the primary purification of S2, the reaction time is doubled, and the equipment operation stability is poor. It is easy to block the pipeline, the motor load increases, and it is prone to overload, resulting in frequent equipment failures.

[0111] Example 3

[0112] The flue gas electrostatic precipitator ash used in this example contains 50 wt% of sulfur oxides (ferric sulfate, sodium sulfate, calcium sulfate, magnesium sulfate, sodium thiosulfate), 15 wt% of vanadium pentoxide, 10 wt% of sodium oxide, and 5 wt% of nickel oxide (including nickel sesquioxide and nickel tetroxide).

[0113] S1. Dissolution and leaching

[0114] Dissolve 2 tons of the weighed flue gas electrostatic precipitator ash in 16 tons of water and stir evenly to obtain an ash slurry.

[0115] S2. Primary purification

[0116] The solution containing cations such as Fe 2+ , Fe 3+ , Ni 2+ , Ca 2+ , Mg 2+ , Al 3+ and anions such as SiO3 2- , PO4 3- , SO4 2-The ashy slurry containing anions is pumped into a stirring tank, and NaOH is added to adjust the pH value of the ashy slurry to 8.5. About 400 kg of hydrogen peroxide is added, and the pH value of the ashy slurry is continuously adjusted to keep it stable at 8.5. Heating is started, and the temperature is controlled within 65 °C for continuous reaction for 1 hour. After the ripening reaction ends, Fe 2+ 、Ni 2+ 、Mg 2+ and other cations form hydroxide precipitates, PO4 3- and Ca 2+ form insoluble Ca3(PO4)2 precipitates, and SiO3 2- and Al 3+ form Al2(SiO3)3 precipitates. 1500 kg of solid NaOH is consumed in this process.

[0117] S3. Filtration and separation of the filtrate

[0118] The preliminarily purified slurry is subjected to solid-liquid separation through a filter press to obtain 2000 kg of filter residue with a water content of 60%. The filter residue contains about 2.5% of vanadium and nickel and is sold directly as a nickel-vanadium concentrate slag product. The recovery rate of vanadium in the filter residue is about 20%. The separated vanadium-containing solution is light yellow, and the content of soluble vanadium V2O7 4- in the solution is 1.5%, and the content of sodium sulfate is 15%.

[0119] S4. Hydrolysis and precipitation of the filtrate

[0120] The above-mentioned vanadium-containing solution is added to a purification stirring tank, and the pH value of the solution is adjusted to 2.0 with 20% dilute sulfuric acid, heated to 80 °C and kept warm. Through regular analysis, the purification reaction ends until the vanadium concentration in the solution drops to between 0.015%. The reaction time is about 40 minutes. At this time, the solution is colorless or slightly light yellow, and finally hydrated vanadium pentoxide brick-red precipitate, that is, red cake, is produced. In this step, when the vanadium-containing solution is hydrolyzed and precipitated by adding acid for neutralization, the form of vanadium gradually changes, and the reaction is as follows:

[0121]

[0122] S5. Filtration and separation

[0123] The solution containing the red cake is filtered through a filter press to separate the red cake and the filtrate. The total weight of the separated red cake is 2000 kg, and the water content is 60%. The purity of V2O5 in the red cake solid is about 80% (the recovery rate of vanadium in the red cake is about 80%). At this time, the filtrate contains 15% wt of sodium sulfate but contains 0.015% of vanadium oxide ion impurities.

[0124] S6. Purification and vanadium removal of the filtrate

[0125] Adjust the pH value of the filtrate to 6.5, then pass the filtrate through a D201 resin column, control the flow rate during the process, and conduct detection at the outlet until the sodium sulfate solution at the outlet is colorless and transparent and no vanadium ions can be detected, which is considered qualified. At this time, the concentration of vanadium is less than <1 ppm, and the concentration of sodium sulfate is about 20%. This sodium sulfate solution can be used as a preparation solution for evaporation crystallization.

[0126] S7. Evaporation Crystallization

[0127] Pump the sodium sulfate solution into a double-effect evaporation system for evaporation crystallization, control the crystallization temperature at 40 °C, and the crystallization time at 384 min. The crystalline product obtained is anhydrous sodium sulfate with a purity of 99.5%. The condensed water generated during the evaporation process can be recycled back to the workshop for reuse, achieving zero discharge.

[0128] S8. Centrifugal Drying and Packing

[0129] The centrifugal dryer dries and packs the sodium sulfate crystals.

[0130] In this embodiment, the dosage ratio of flue gas electrostatic precipitator ash to water can be 1:8, which has no impact on the overall product output and product quality. However, compared with Example 1, it wastes resources and has 60% more water consumption. During the S7 evaporation crystallization process, the time increases, and the usage time of the evaporation system increases.

[0131] Comparative Example 1

[0132] Implement according to the method of Example 1, except that in step S2, only hydrogen peroxide is added, and NaOH is not added to adjust the pH value.

[0133] The specific operation process includes:

[0134] S1. Dissolution and Leaching

[0135] Dissolve 2 tons of weighed flue gas electrostatic precipitator ash in 10 tons of water, stir evenly to obtain an ash slurry.

[0136] S2. Primary Purification

[0137] Pump the ash slurry containing cations such as Fe 2+ , Fe 3+ , Ni 2+ , Ca 2+ , Mg 2+ , Al 3+ and anions such as SiO3 2- , PO4 3- , SO4 2- into a stirring tank, add about 400 kg of hydrogen peroxide, turn on the heating, and control the temperature within 65 °C for continuous reaction for 1 hour. After the aging reaction ends, Fe 2+ , Ni 2+ , Mg2+ Equivalent cations form hydroxide precipitates, PO4 3- and Ca 2+ form insoluble Ca3(PO4)2 precipitate, SiO3 2- and Al 3+ form Al2(SiO3)3 precipitate.

[0138] S3, Filtrate filtration and separation

[0139] Subject the primary purified slurry to solid-liquid separation through a filter press to obtain 2000 kg of filter cake with a water content of 60%. The filter cake contains approximately 2.5% vanadium and nickel and is sold directly as nickel-vanadium concentrate slag product. The recovery rate of vanadium in the filter cake is approximately 20%. The separated vanadium-containing solution is light yellow. The content of soluble vanadium V2O7 4- in the solution is 2.5%, and the content of sodium sulfate is 10%.

[0140] S4, Hydrolysis precipitation of the filtrate

[0141] Add the above vanadium-containing solution to a purification stirring tank, adjust the pH value of the solution to 2.0 with 20% dilute sulfuric acid, heat up to 90 °C and keep it warm. Through regular analysis, until the concentration of vanadium in the solution drops to between 0.015%, the purification reaction ends. The reaction time is approximately 40 minutes. At this time, the solution is colorless or slightly light yellow, and finally hydrated vanadium pentoxide brick-red precipitate, i.e., red cake, is produced. In this step, when the vanadium-containing solution is hydrolyzed and precipitated by adding acid for neutralization, the form of vanadium gradually changes. The reaction is as follows:

[0142]

[0143] S5, Filtration and separation

[0144] Press-filter the above solution containing red cake through a filter press to separate the red cake and the filtrate. The total weight of the separated red cake is 2000 kg, with a water content of 60%. The purity of V2O5 in the red cake solid is 80% (the recovery rate of vanadium in the red cake is approximately 80%). At this time, the filtrate contains 10% sodium sulfate and contains Fe 2+ 、Fe 3+ 、Ni 2+ 、Ca 2+ 、Mg 2+ 、Al 3+ 、vanadium-oxygen ion impurities.

[0145] S6, Purification of the filtrate to remove vanadium

[0146] At this time, the filtrate is still acidic, with a pH value of 2.0 and a sodium sulfate concentration of approximately 10%. The filtrate cannot purify the Fe 2+ 、Fe 3+ 、Ni 2+ 、Ca2+ , Mg 2+ , Al 3+ , vanadium-oxygen ion impurities, and the concentration of sodium sulfate in the filtrate is about 10%, which is relatively low and has no economic value. The filtrate is worthless, becomes waste liquid, generates waste, and cannot achieve zero emissions.

[0147] Comparative Example 2

[0148] Implemented according to the method of Example 1, except that in step S4, the pH value of the solution is not adjusted with dilute sulfuric acid.

[0149] The specific operation process includes:

[0150] S1. Dissolution and leaching

[0151] Weigh 2 tons of flue gas electrostatic precipitator ash and dissolve it in 10 tons of water, stir evenly to obtain an ash slurry.

[0152] S2. Primary purification

[0153] Pump the ash slurry containing cations such as Fe 2+ , Fe 3+ , Ni 2+ , Ca 2+ , Mg 2+ , Al 3+ and anions such as SiO3 2- , PO4 3- , SO4 2- into a stirring tank, add NaOH to adjust the pH value of the ash slurry to 8.5, add about 400 kg of hydrogen peroxide, continue to adjust the pH value of the ash slurry to make it stable at 8.5, turn on the heating, and control the temperature within 65 °C for continuous reaction for 1 hour. After the ripening reaction ends, the cations such as Fe 2+ , Ni 2+ , Mg 2+ in the slurry generate hydroxide precipitates, PO4 3- and Ca 2+ generate insoluble Ca3(PO4)2 precipitate, SiO3 2- and Al 3+ generate Al2(SiO3)3 precipitate. This process consumes 1500 kg of solid NaOH.

[0154] S3. Filtration and separation of the filtrate

[0155] Perform solid-liquid separation on the primary purified slurry through a filter press to obtain a total filter residue weight of 2000 kg, with a water content of 60%. The filter residue contains about 2.5% vanadium and nickel, and is directly sold as a nickel-vanadium concentrate slag product. The recovery rate of vanadium in the filter residue is about 20%. The separated vanadium-containing solution is light yellow, and the soluble vanadium V2O7 in the solution4- The content of [substance] is 2.5%, and the content of sodium sulfate is 10%.

[0156] S4. Hydrolysis and precipitation of the filtrate

[0157] If the pH value of the vanadium-containing solution in this step is not adjusted with dilute sulfuric acid, V2O7 in the solution 4- cannot be hydrolyzed and precipitated, and vanadium pentoxide cannot be separated out.

[0158] S6. Purification of the filtrate

[0159] The filtrate is still alkaline, with a pH value of 8.5 and a sodium sulfate concentration of approximately 10%. This sodium sulfate solution contains NaOH solution and soluble vanadium V2O7 4- ions. It is impossible to deeply purify sodium sulfate, which has no economic value. Instead, waste liquid is generated, and zero discharge cannot be achieved.

[0160] It can be seen from the examples and comparative examples that the technical solution described in the present invention can comprehensively recover valuable elements from the flue gas electrostatic precipitator ash, turning waste into treasure, with high economic and environmental benefits. Moreover, this method is simple to operate and has low costs.

[0161] It should be understood that the parts not elaborated in detail in this specification all belong to the prior art.

[0162] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A comprehensive utilization method for electric precipitator ash of flue gas, characterized in that, The comprehensive utilization method includes: Mixing the flue gas electrostatic precipitator ash with water to obtain an ash slurry; Adding an oxidant to the ash slurry, adjusting the ash slurry to be alkaline, and then performing a first reaction under a first heating condition, followed by solid-liquid separation to obtain a vanadium-containing solution and a filter residue; Adjusting the vanadium-containing solution to be acidic with a sulfuric acid solution, and then performing a second reaction under a second heating condition, followed by solid-liquid separation to obtain vanadium pentoxide and a filtrate; Adjusting the filtrate to be neutral, and then treating the obtained neutral solution through a resin column to obtain a sodium sulfate solution; Performing evaporation crystallization on the sodium sulfate solution to obtain anhydrous sodium sulfate.

2. The comprehensive utilization method according to claim 1, characterized in that, The flue gas electrostatic precipitator ash contains 46 - 55 wt% of sulfur oxides, 10 - 15 wt% of vanadium pentoxide, 8 - 12 wt% of sodium oxide, and 3 - 5 wt% of nickel oxide.

3. The comprehensive utilization method according to claim 1 or 2, characterized in that, The weight ratio of the flue gas electrostatic precipitator ash to the amount of water used is 1:(3 - 8).

4. The comprehensive utilization method according to claim 1 or 2, characterized in that The oxidant is hydrogen peroxide and / or sodium hypochlorite; And / or, the amount of the oxidant used is 0.1 - 0.5 times the weight of the flue gas electrostatic precipitator ash.

5. The comprehensive utilization method according to claim 1 or 2, characterized in that Adjusting the ash slurry to be alkaline with sodium hydroxide, and the amount of sodium hydroxide used is 0.6 - 0.9 times the weight of the flue gas electrostatic precipitator ash; And / or, the process of adjusting the ash slurry to be alkaline includes: adjusting the pH value of the ash slurry to 8 - 9; And / or, the process of adding an oxidant to the ash slurry and adjusting the ash slurry to be alkaline includes: first adjusting the ash slurry to be alkaline, then adding the oxidant, and then continuing to adjust the ash slurry to be alkaline.

6. The comprehensive utilization method according to claim 1, wherein, The conditions of the first reaction include: the temperature is 60 - 70 °C, and the time is 40 - 80 min.

7. The comprehensive utilization method according to claim 5, characterized in that The content of V2O7 in the vanadium-containing solution 4- is 2-3 wt%, and the content of sodium sulfate is 15-25 wt%; And / or, the filter residue contains vanadium and nickel, and the total content of vanadium and nickel is 2 - 3 wt%.

8. The comprehensive utilization method according to claim 1, wherein, The process of adjusting the vanadium-containing solution to be acidic with a sulfuric acid solution includes: adjusting the pH value of the vanadium-containing solution to 1.8 - 2.2 with a sulfuric acid solution; And / or, the conditions of the second reaction include: the temperature is 85 - 95 °C, and the time is 30 - 60 min; And / or, the concentration of sodium sulfate in the filtrate is 18 - 22 wt%, and the concentration of vanadium is 0.01 - 0.02 wt%.

9. The comprehensive utilization method according to claim 1, wherein The process of adjusting the filtrate to be neutral includes: adjusting the pH value of the filtrate to 6 - 7; And / or, the resin column is a D201 resin column; And / or, the concentration of sodium sulfate in the sodium sulfate solution is 18 - 22 wt%, and the concentration of vanadium is <1 ppm.

10. The comprehensive utilization method according to claim 1, characterized in that, The conditions of the evaporation crystallization include: the temperature is 35 - 50 °C, the pressure is normal pressure, and the time is 100 - 400 min.

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