阅读说明：本技术 一种多废料联合处理制备氟化铝产品的方法及氟化铝产品 (Method for preparing aluminum fluoride product by multi-waste combined treatment and aluminum fluoride product ) 是由 吕晓军 韩泽勋 罗丽琼 吴勇聪 蒿鹏程 于 2021-07-28 设计创作，主要内容包括：本发明涉及一种多废料联合处理制备氟化铝产品的方法及氟化铝产品,将含氟废料颗粒、铝灰粉末和待处理的铝阳极氧化废水混合,浸出后,固液分离,获得浸出液和滤渣；调节浸出液的pH值至3-5,固液分离得固相物,烘干,获得羟基氟化铝粉末,将羟基氟化铝粉末与反应剂混合均匀,热处理,获得热处理产物；当反应剂包括氟化氢钾、氟化氢钠、氟化氢锂中的至少一种时,对热处理产物进行洗涤、干燥,获得氟化铝产品；当反应剂由氟化铵、氟化氢铵中的至少一种组成时,热处理产物即为氟化铝产品。本发明整合铝冶炼及加工行业的含氟废料、铝灰和铝阳极氧化废水,以羟基氟化铝的形式高效回收其中有价铝、氟元素,工艺简单,可行性高。(The invention relates to a method for preparing an aluminum fluoride product by multi-waste combined treatment and the aluminum fluoride product, wherein fluorine-containing waste particles, aluminum ash powder and aluminum anodic oxidation wastewater to be treated are mixed, and after leaching, solid-liquid separation is carried out to obtain leachate and filter residue; adjusting the pH value of the leachate to 3-5, performing solid-liquid separation to obtain a solid phase, drying to obtain hydroxyl aluminum fluoride powder, uniformly mixing the hydroxyl aluminum fluoride powder with a reactant, and performing heat treatment to obtain a heat treatment product; when the reactant comprises at least one of potassium bifluoride, sodium bifluoride and lithium bifluoride, washing and drying the heat treatment product to obtain an aluminum fluoride product; when the reactant is composed of at least one of ammonium fluoride and ammonium bifluoride, the heat treatment product is the aluminum fluoride product. The method integrates the fluorine-containing waste, the aluminum ash and the aluminum anodic oxidation wastewater in the aluminum smelting and processing industry, efficiently recovers valuable aluminum and fluorine elements in the aluminum anodic oxidation wastewater in the form of hydroxyl aluminum fluoride, and has simple process and high feasibility.)

1. A method for preparing aluminum fluoride products by multi-waste combined treatment is characterized by comprising the following steps:

s1, crushing the fluorine-containing waste to be treated to obtain fluorine-containing waste particles;

crushing the aluminum ash to be treated to obtain aluminum ash powder;

s2, mixing the fluorine-containing waste particles obtained in the step S1, aluminum ash powder and aluminum anodic oxidation wastewater to be treated, and after leaching, carrying out solid-liquid separation to obtain leachate and filter residue;

s3, adjusting the pH value of the leachate in the S2 to 3-5, performing solid-liquid separation to obtain a solid phase substance, and drying to obtain hydroxyl aluminum fluoride powder;

s4, uniformly mixing the hydroxyl aluminum fluoride powder obtained in the step S3 with a reactant, and carrying out heat treatment to obtain a heat treatment product and tail gas;

wherein the reactant comprises at least one of potassium bifluoride, sodium bifluoride, lithium bifluoride, ammonium fluoride and ammonium bifluoride;

when the reactant comprises at least one of potassium bifluoride, sodium bifluoride and lithium bifluoride, washing and drying the heat treatment product to obtain an aluminum fluoride product;

when the reactant is composed of at least one of ammonium fluoride and ammonium bifluoride, the heat treatment product is an aluminum fluoride product.

2. The method according to claim 1, wherein in S1, the grain size of the fluorine-containing waste material particles is less than or equal to 5 mm; the grain diameter of the aluminum ash powder is less than or equal to 3 mm.

3. The method according to claim 1, wherein in S1, the fluorine-containing waste material comprises one or more of waste electrolyte, residual materials after carbon extraction from waste electrodes, and solid smoke generated by aluminum electrolysis; the aluminum ash comprises one or more of primary aluminum ash and secondary aluminum ash, and preferably, the content of aluminum element in the aluminum ash is 20-50 wt.%.

4. The method of claim 1, wherein in S2, H is in the aluminum anode oxidation wastewater₂SO₄The concentration is 100-300g/L, Al³⁺The ion concentration is 5-50 g/L; further, in S2, the mass ratio of the fluorine-containing waste particles to the aluminum ash powder to the aluminum anodic oxidation wastewater is 1:0.05-0.5: 0.1-0.5.

5. The method according to claim 1, wherein in S3, the pH of the leachate is controlled to 3-5 by adding a lye to the leachate obtained in S2 and stirring the leachate.

6. The method as claimed in claim 1, wherein the heat treatment in S4 is performed at 120-600 ℃ for 2-10 h.

7. The method as claimed in claim 1, wherein in S4, the heat treatment is performed at 380 ℃ at 120 ℃ for 1-3 h; then heating to 400 ℃ and 600 ℃, and carrying out heat treatment for 1-5 h; preferably, in S4, the molar ratio of F to Al in the mixture of aluminum hydroxyfluoride powder and the reactant is 2.5-20: 1.

8. The method according to any one of claims 1 to 7, wherein after S4, the method further comprises the steps of treating the off-gas by adsorbing the off-gas with a part of the aluminum hydroxyfluoride powder obtained in S3;

the adsorption-treated aluminum hydroxyfluoride powder was returned to S4.

9. The method according to claim 8, characterized in that when the reactant comprises at least one of ammonium fluoride and ammonium bifluoride, the tail gas after adsorption treatment is introduced into absorption mother liquor containing hydrofluoric acid to obtain ammonium salt solution; then, sequentially evaporating, concentrating and crystallizing the ammonium salt solution to obtain ammonium salt and residual mother liquor; returning said ammonium salt to S4 for use as a reactant or one of its constituents; using the residual mother liquor as absorption mother liquor or one of the raw materials for the absorption mother liquor;

wherein the ammonium salt is ammonium fluoride and/or ammonium bifluoride; preferably, the content of hydrofluoric acid in the absorption mother liquor is more than 10 wt%, and the crystallization temperature is 0-10 ℃.

10. An aluminium fluoride product produced by the method of any one of claims 1 to 9.

Technical Field

The invention relates to a method for preparing an aluminum fluoride product by multi-waste combined treatment and the aluminum fluoride product, belonging to the field of waste recycling treatment.

Background

Aluminum fluoride is an important additive in the smelting industry. In the aluminum electrolysis process, aluminum fluoride is continuously added into the electrolytic cell to maintain the constant electrolyte molecular ratio and ensure the stable operation of the electrolytic cell. At present, aluminum fluoride is mainly fluorite (CaF)₂) Although the reserve amount of fluorite is high and accounts for 13.5% of the total reserve amount of the world in China for the production of raw materials, the gap of the fluorite raw materials is increased year by year due to the rapid development of downstream industries such as electrolytic aluminum and the like in recent years. This also leads to a high price for aluminium fluoride, increasing the cost of the product starting from aluminium fluoride. Therefore, the search for a new aluminum fluoride generation process which does not depend on fluorite as a raw material is particularly urgent for the aluminum fluoride production industry and has wide market prospect.

In fact, the electrolyte is continuously taken out while adding aluminum fluoride into the aluminum electrolysis cell to ensure the material balance, and the taken-out electrolyte is the fluorine-containing waste material. In the electrolytic aluminum industry, except for directly taken out waste electrolyte, the regenerated cryolite obtained by classifying overhaul residues and carbon residues or extracting carbon is also a main component of electrolytic aluminum fluorine-containing waste. In the past, the fluorine-containing waste can be favorably used as a furnace starting raw material through capacity expansion, but in recent years, 4500 million tons of capacity ceilings are formed in China, the excessive fluorine-containing waste cannot be utilized, and enterprises generally adopt stockpiling treatment. The stockpiling not only occupies the effective space of enterprises, but also toxic cyanide and soluble fluorine in the stockpiling easily pollute underground water and soil resources along with rainwater, thereby bringing huge environmental protection pressure to aluminum enterprises. The fluorine-containing waste material contains a large amount of valuable aluminum fluoride, so that the recovery of the aluminum fluoride for producing aluminum fluoride in the fluorine-containing waste material is of great significance to the aluminum electrolysis industry.

Chinese patent nos. CN108677020A, CN111690823A and CN109759423A provide methods for recovering valuable aluminum and fluorine from fluorine-containing wastes, which use acid and/or aluminum salt to leach fluorine-containing wastes, and add alkali solution to the obtained leachate to adjust PH, so that aluminum and fluorine in the leachate are recovered as aluminum hydroxyfluoride precipitate.

As for the obtained aluminum hydroxyfluoride product, the Chinese patent CN111690823A indicates that the aluminum fluoride can be obtained by calcination at 350-650 ℃, but alumina is also generated during calcination, so that the purity of the obtained aluminum fluoride is low. Chinese patent CN109759423A discloses that hydroxy aluminum fluoride reacts with hydrofluoric acid, and the reaction solution is crystallized to obtain aluminum fluoride, but this method obtains hydrated aluminum fluoride, further conversion into aluminum fluoride requires calcination, which results in hydrolysis of aluminum fluoride into alumina and reduces the purity of aluminum fluoride. Therefore, how to further efficiently convert the aluminum hydroxyfluoride into the aluminum fluoride is a key and difficult point in the process of converting the waste electrolyte into the aluminum fluoride by a wet method.

In the downstream industrial aluminum alloy production industry of electrolytic aluminum, the anodic oxidation process is accompanied by the generation of anodic oxidation wastewater which needs to be effectively treated to meet emission standards. The wastewater is often treated by acid-base neutralization in industry, and in fact, acidic anodizing wastewater contains a large amount of acid and a certain amount of aluminum salt (generally, H)₂SO₄The concentration is 100-300g/L, Al³⁺Ion concentration is 5-50g/L), and the acid-base neutralization treatment method causes the waste of valuable acid and aluminum salt, so that the resource utilization of the valuable acid and the aluminum salt cannot be realized.

Disclosure of Invention

Aiming at the defects of the prior art, one of the purposes of the invention is to provide a method for preparing an aluminum fluoride product by multi-waste combined treatment so as to realize resource recovery of aluminum and fluorine; the second purpose of the invention is to provide an aluminum fluoride product.

In order to solve the technical problems, the technical scheme of the invention is as follows:

a method for preparing aluminum fluoride products by multi-waste combined treatment comprises the following steps:

s1, crushing the fluorine-containing waste to be treated to obtain fluorine-containing waste particles;

crushing the aluminum ash to be treated to obtain aluminum ash powder;

s2, mixing the fluorine-containing waste particles obtained in the step S1, aluminum ash powder and aluminum anodic oxidation wastewater to be treated, and after leaching, carrying out solid-liquid separation to obtain leachate and filter residue;

s3, adjusting the pH value of the leachate in the S2 to 3-5, performing solid-liquid separation to obtain a solid phase substance, and drying to obtain hydroxyl aluminum fluoride powder;

s4, uniformly mixing the hydroxyl aluminum fluoride powder obtained in the step S3 with a reactant, and carrying out heat treatment to obtain a heat treatment product and tail gas;

wherein the reactant comprises at least one of potassium bifluoride, sodium bifluoride, lithium bifluoride, ammonium fluoride and ammonium bifluoride;

when the reactant comprises at least one of potassium bifluoride, sodium bifluoride and lithium bifluoride, washing and drying the heat treatment product to remove water-soluble metal fluoride therein to obtain an aluminum fluoride product;

when the reactant is composed of at least one of ammonium fluoride and ammonium bifluoride, the heat treatment product is an aluminum fluoride product.

Furthermore, in S1, the particle size of the fluorine-containing waste material particles is less than or equal to 5 mm; the grain diameter of the aluminum ash powder is less than or equal to 3 mm.

Further, in S1, the fluorine-containing waste material includes one or more of waste electrolyte (such as waste electrolyte fished out from an electrolytic cell), residual material after carbon extraction from waste electrodes (waste electrolyte after carbon extraction from waste cathodes or anodes), and solid smoke generated by aluminum electrolysis, and may also be other forms of fluorine-containing waste electrolyte for aluminum electrolysis.

Further, the fluorine-containing waste material is regenerated cryolite obtained after flotation and carbon extraction of waste electrodes.

Further, in S1, the aluminum ash includes one or more of primary aluminum ash and secondary aluminum ash, and preferably, the content of aluminum element in the aluminum ash is 20-50 wt.%.

Optionally, the fluorine-containing waste material contains 35-60 wt% of F, 10-25 wt% of Na, 5-20 wt% of Al, 0-10 wt% of K, 0-10 wt% of Ca, 0-5 wt% of O, 0-5 wt% of Mg and 0-5 wt% of S.

Further, in S2, H is contained in the aluminum anodizing wastewater₂SO₄The concentration is 100-300g/L, and further 120-280g/L, Al³⁺The ion concentration is 5-50g/L, further 10-45 g/L.

Further, in S2, the mass ratio of the fluorine-containing waste particles to the aluminum ash powder to the aluminum anodic oxidation wastewater is 1:0.05-0.5:0.1-0.5, and further 1:0.1-0.4: 0.2-0.4.

Further, in S2, the fluorine-containing waste particles obtained in S1, aluminum ash powder, and aluminum anodic oxidation wastewater to be treated are mixed and ball-milled.

Further, in S3, an alkali solution is added to the leachate obtained in S2 and stirred, and the pH of the leachate is controlled to 3 to 5.

Further, in S3, the aluminum hydroxyfluoride is AlF_x(OH)_3-x·mH₂O, wherein 0<x<3，m≥0。

Further, in S4, the heat treatment is performed at 120-600 ℃ for 2-10h, further 2-8 h.

Further, in S4, the heat treatment is performed at 380 ℃ at 120-; then the temperature is raised to 400 ℃ and 600 ℃, and the heat treatment is carried out for 1-5h, further 1.5-3.5 h. The applicant researches and discovers that the treatment for 1 to 3 hours at low temperature is helpful for separating a large amount of bound water in the aluminum hydroxyfluoride from the aluminum hydroxyfluoride, and a small amount of reactant is decomposed and volatilized to generate HF gas, so that the aluminum hydroxyfluoride is under the protection of the HF gas, and the hydrolysis of the aluminum hydroxyfluoride can be inhibited; then treating at high temperature for 1-5h, so that the residual small amount of bound water and the aluminum hydroxyfluoride directly react with a reactant, and the aluminum hydroxyfluoride is converted into aluminum fluoride; the segmented heat treatment is favorable for complete aluminum fluoride conversion, avoids the phenomenon that a large amount of reactants are heated, decomposed and volatilized at high temperature once and cannot react with the hydroxyl aluminum fluoride, is favorable for reducing the dosage of the reactants, and reduces the treatment cost while ensuring the conversion effect.

Further, in S4, the mass ratio of the aluminum hydroxyfluoride powder to the reactant is 15-25:25-45, further 20-24: 28-42.

Further, in S4, in the mixture of the aluminum hydroxyfluoride powder and the reactant, the molar ratio of F to Al is 2.5-20:1, more preferably 3-15:1, and most preferably 4-10: 1.

Preferably, in S4, the heat treatment is performed in a closed environment.

Further, after S4, the method further includes a step of treating the tail gas, i.e., adsorbing the tail gas with a portion of the hydroxy aluminum fluoride powder obtained in S3, so that the hydroxy aluminum fluoride powder has strong adsorbability and can better absorb HF in the tail gas;

the aluminum hydroxyfluoride powder after the adsorption treatment is returned to S4, whereby the reuse of HF can be realized, which contributes to a reduction in the amount of the reactant.

Further, when the reactant comprises at least one of ammonium fluoride and ammonium bifluoride, introducing the tail gas subjected to adsorption treatment into absorption mother liquor containing hydrofluoric acid to absorb ammonia gas in the tail gas to obtain an ammonium salt solution; then, sequentially evaporating, concentrating and crystallizing the ammonium salt solution to obtain ammonium salt and residual mother liquor; returning said ammonium salt to S4 for use as a reactant or one of its constituents; using the residual mother liquor as absorption mother liquor or one of the raw materials for the absorption mother liquor;

wherein the ammonium salt is ammonium fluoride and/or ammonium bifluoride.

Preferably, the content of hydrofluoric acid in the absorption mother liquor is more than 10 wt%, further 12-40 wt%, and further 14-20 wt%.

Preferably, the crystallization temperature is 0-10 ℃.

An aluminium fluoride product prepared by the method as described above.

The method can be used for treating the fluorine-containing waste, the aluminum ash and the aluminum anodic oxidation wastewater in a combined manner, can fully utilize the characteristics of high fluorine content, high aluminum ash content and high acid content of the aluminum anodic oxidation wastewater of the fluorine-containing waste, meet the leaching requirements of fluorine and aluminum in related materials and the preparation requirement of aluminum hydroxyfluoride, can better recycle aluminum ions in the aluminum anodic oxidation wastewater, does not need additional fluorine sources and aluminum sources, and is favorable for reducing the treatment cost. Meanwhile, the characteristic that the reactant can release HF during treatment at the temperature of 120-600 ℃ is utilized, and the hydroxyl aluminum fluoride is mixed with the reactant and then subjected to heat treatment, so that on one hand, the released hydrogen fluoride can inhibit hydrolysis of the hydroxyl aluminum fluoride in the process of removing crystal water during heat treatment, and high-purity aluminum fluoride can be directly obtained; on the other hand, the hydrogen fluoride released can react directly with aluminum hydroxyfluoride to produce aluminum fluoride, with the following reaction equation:

AlF_x(OH)_3-x·mH₂O+(3-x)HF＝AlF₃+(3-x+m)H₂O↑。

the invention treats the aluminum anode oxidation wastewater together with the fluorine-containing waste and the aluminum ash, thereby not only effectively utilizing the acid and the Al in the aluminum anode oxidation wastewater³⁺The acidity and Al content of the waste water are reduced, the waste resource utilization is realized, the treatment cost of the fluorine-containing waste material in the aluminum electrolysis can be obviously reduced, and the green recycling economy of the aluminum industry is realized.

Compared with the prior art, the invention has the following beneficial effects:

(1) the method integrates the fluorine-containing waste, the aluminum ash and the aluminum anodic oxidation wastewater in the aluminum smelting and processing industry, efficiently recovers valuable aluminum and fluorine elements in the aluminum hydroxide in the form of aluminum hydroxide, has simple process and high feasibility, enables the waste and the waste liquid generated at the upstream and the downstream of the aluminum industry to be effectively recycled, and is beneficial to the green sustainable development of the aluminum industry.

(2) The method realizes the conversion of the hydroxyl aluminum fluoride into the aluminum fluoride with higher purity in one step, is simple and efficient, does not need calcination treatment, and has extremely low content of aluminum oxide in the obtained aluminum fluoride product.

(3) The reactant in the invention does not pollute the product and is not residual, and can be effectively separated from the aluminum fluoride by simple water washing, thus being beneficial to more simply obtaining high-purity anhydrous aluminum fluoride; in addition, the reactant and the aluminum hydroxyfluoride are subjected to solid-solid mixing and roasting, so that the operation is convenient, no special requirement is required on equipment, and the industrial production is favorably realized.

Drawings

FIG. 1 is an XRD pattern of aluminum hydroxyfluoride hydrate from example 1.

Figure 2 is the XRD pattern of the aluminum fluoride product of example 1.

Detailed Description

The present invention will be described in detail with reference to examples. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

Example 1

The method for treating fluorine-containing waste electrolyte of the present example comprises the following steps:

(1) 16.00g of waste electrolyte powder (XRF fluorescence analysis: F49.68 wt.%, Na 21.48 wt.%, Al 14.48%, Ca 5.46, K5.13 wt.%, O2.59 wt.%, Mg 0.57 wt.%, S0.18 wt.%), 3.20g of aluminum ash powder (Al content: 32.15 wt.%), and 200ml of aluminum anode oxidation wastewater (H0.18 wt.%) are taken₂SO₄Concentration of 200g/L, Al³⁺The ion concentration is 15g/L), mixing and then ball-milling and leaching for 1h in a ball-milling tank, wherein the ball-milling rotating speed is 350 r/min; then filtering, slowly adding 4mol/L sodium hydroxide solution into the obtained filtrate to stop when the pH value of the solution is 3.5, filtering and drying to obtain 22.54g of hydrated aluminum hydroxyfluoride precipitate and filtrate; the filtrate was evaporated to give 39.72g of a mixed salt having sodium sulfate as a main phase.

(2) Uniformly mixing 30.00g of ammonium bifluoride with 22.54g of aluminum hydroxyfluoride, putting the mixture into a crucible, roasting the mixture for 2 hours at the temperature of 250 ℃, then heating the mixture to 550 ℃, and roasting the mixture for 2 hours to obtain 21.68g of aluminum fluoride and tail gas;

(3) absorbing the tail gas by using hydrofluoric acid with the mass concentration of 15% to obtain absorption liquid, then evaporating, concentrating, cooling and crystallizing the absorption liquid to obtain 15.14g of a mixture of ammonium fluoride and ammonium bifluoride, returning the obtained mixture to the step (2), and further participating in roasting; the rest absorption liquid can be used for absorbing tail gas again.

XRD detection is carried out on the hydrated aluminum hydroxyfluoride precipitate obtained in the step (1), and the detection result is shown in figure 1, so that the purity of the aluminum hydroxyfluoride in the obtained precipitate is high; XRD detection is carried out on the aluminum fluoride product obtained in the step (1), and the result is shown in figure 2, obviously, the main phase of the obtained product is aluminum fluoride, almost no impurity phase peak exists, the XRF element content analysis result is shown in tables 1 and 2, the oxygen content in the obtained aluminum fluoride product is extremely low, the reaction is well carried out, and the purity of the aluminum fluoride product is high.

Comparative example 1

Example 1 was repeated with the only difference that: in the step (2), the heat treatment is stopped by baking only at 250 ℃ for 4 hours.

Comparative example 2

Example 1 was repeated with the only difference that: in the step (2), the heat treatment is stopped by baking at 550 ℃ for 4 hours.

As is clear from tables 1 and 2, the purity of the aluminum fluoride product obtained by only one-stage calcination was not more than 90%, although the total calcination time was the same.

Example 2

Example 1 was repeated with the only difference that: the waste electrolyte powder in step (1) was changed to flotation cryolite (XRF analysis: F47.32 wt.%, Na 22.37 wt.%, Al 14.73%, Ca 6.75, K4.91 wt.%, O3.11 wt.%, Mg 0.42 wt.%, S0.13 wt.%), and the resulting hydroxyaluminum fluoride and aluminum fluoride products were examined and the results are shown in tables 1 and 2.

Example 3

Example 1 was repeated with the only difference that: and (3) changing the ammonium bifluoride in the step (2) into 40.00g of sodium hydrogen fluoride, washing the roasted and cooled product with water, filtering, and drying at 100 ℃ for 5 hours to obtain an aluminum fluoride product. And (4) evaporating and crystallizing the washing liquid obtained by washing with water to obtain a sodium fluoride product.

The obtained aluminum hydroxyfluoride and aluminum fluoride products were tested and the results are shown in tables 1 and 2.

TABLE 1 relevant Process parameters and the results of the determination of the content of the target substance in the relevant products for the examples

TABLE 2 content of part of elements in the hydrated aluminum hydroxyfluoride and aluminum fluoride products

The foregoing examples are set forth to illustrate the present invention more clearly and are not to be construed as limiting the scope of the invention, which is defined in the appended claims to which the invention pertains, as modified in all equivalent forms, by those skilled in the art after reading the present invention.