阅读说明：本技术 一种从铝电解槽大修渣中回收氟化铝的方法 (Method for recovering aluminum fluoride from overhaul residues of aluminum electrolytic cell ) 是由 刘向前 李海 郑斌 王玉强 于 2020-05-13 设计创作，主要内容包括：本发明提供了一种从铝电解槽大修渣中回收氟化铝的方法,解决了缺乏通过铝电解槽大修渣制备氟化铝的方法的问题。本发明通过对铝电解槽大修渣进行一系列的处理步骤后,制备出电解铝产业中大量需求的氟化铝产品,增加了氟化铝产品的来源,通过这种方式,使得氟元素在电解铝产业中得到循环利用,降低了萤石的需求,有益于电解铝行业的可持续发展,具有很高的经济效益和推广价值。同时制备过程中分离出的主要由碳素材料组成的副产品,也可经过一定的提存方法后得到耐火的碳素材料,使得铝电解槽大修渣不再是电解铝厂的负担,而变为电解铝厂的又一个经济效益增长点,不但使铝电解槽大修渣变废为宝,而且可有效降低电解铝厂的生产成本。(The invention provides a method for recovering aluminum fluoride from overhaul residues of an aluminum electrolytic cell, which solves the problem of lacking a method for preparing aluminum fluoride from the overhaul residues of the aluminum electrolytic cell. According to the method, after a series of treatment steps are carried out on the overhaul residues of the aluminum electrolytic cell, aluminum fluoride products which are greatly required in the electrolytic aluminum industry are prepared, and the sources of the aluminum fluoride products are increased. Meanwhile, the byproduct mainly composed of carbon materials separated in the preparation process can also be extracted by a certain extraction method to obtain a fireproof carbon material, so that the overhaul residues of the aluminum electrolysis cell are not the burden of an electrolytic aluminum plant any more and become another economic benefit growth point of the electrolytic aluminum plant, the overhaul residues of the aluminum electrolysis cell are changed into valuable, and the production cost of the electrolytic aluminum plant can be effectively reduced.)

1. A method for recovering aluminum fluoride from overhaul residues of an aluminum electrolysis cell is characterized by comprising the following steps:

(1) crushing and ball-milling overhaul residues of the aluminum electrolytic cell to obtain powdery mixed waste which mainly comprises carbon materials and attachment waste on the waste cell;

(2) putting the powdery mixed waste obtained in the step (1) into a reaction kettle, adding an acidic solution into the reaction kettle, and heating, stirring and fully reacting to obtain a mixed solution;

(3) carrying out precipitation and solid-liquid separation on the mixed solution obtained in the step 2 to obtain a supernatant containing aluminum salt and hydrofluoric acid and a precipitate mainly composed of a carbon material;

(4) injecting the supernatant obtained in the step (3) into a reaction kettle, injecting sufficient aluminum hydroxide into the reaction kettle, precipitating and cooling after full reaction under heating conditions, separating out crude aluminum fluoride crystals, and then performing solid-liquid separation to obtain crude aluminum fluoride crystals;

(5) and (4) washing, filtering and drying the crude aluminum fluoride crystal obtained in the step (4) to obtain a pure aluminum fluoride product.

2. The method for recovering aluminum fluoride from the overhaul slag of aluminum electrolysis cells as claimed in claim 1, wherein: the reaction time in the step (2) and the step (4) is 1-3 hours.

3. The method for recovering aluminum fluoride from the overhaul slag of aluminum electrolysis cells as claimed in claim 1, wherein: the reaction temperature in the step (2) and the step (4) is 60 ℃ to 100 ℃.

4. The method for recovering aluminum fluoride from the overhaul slag of aluminum electrolysis cells as claimed in claim 1, wherein: the number of the ball milling meshes in the step (1) is 200-300 meshes.

5. The method for recovering aluminum fluoride from the overhaul slag of aluminum electrolysis cells as claimed in claim 1, wherein: the concentration of the acidic solution in the step (2) is 0.1-1 mol/L.

6. The method for recovering aluminum fluoride from the overhaul slag of aluminum electrolysis cells as recited in claim 5, wherein: under the condition that the concentration of the acid solution is 0.5mol/L, the mass ratio of the powdery mixed waste material to the acid solution in the step (2) is 1: 10.

7. The method for recovering aluminum fluoride from the overhaul slag of aluminum electrolysis cells as claimed in claim 6, wherein: the mass ratio of the aluminum hydroxide added in the step (4) to the powdery mixed waste in the step (2) is 0.2: 1.

8. the method for recovering aluminum fluoride from the overhaul slag of aluminum electrolysis cells as claimed in claim 1, 5 or 6, wherein: the acid solution is a strong acid solution which can be completely ionized by hydrogen ions after pure acid is used for melting water.

9. The method for recovering aluminum fluoride from the overhaul slag of aluminum electrolysis cells as claimed in claim 1, wherein: the main component of the attachment waste in the step (1) is fluoride, and the fluoride mainly comprises cryolite, sodium fluoride and magnesium fluoride.

Technical Field

The invention relates to the technical field of electrolytic aluminum, in particular to a method for recovering aluminum fluoride from overhaul residues of an aluminum electrolytic cell.

Background

Electrolytic aluminum is aluminum obtained by electrolysis. The modern electrolytic aluminum industry adopts cryolite-alumina molten salt electrolytic method. The molten cryolite is solvent, alumina is solute, carbosome is anode, aluminium liquid is cathode, strong direct current is introduced, electrochemical reaction is carried out on two poles in the electrolytic cell at 950-970 ℃, namely electrolysis. Aluminum fluoride is often added to electrolytic aluminum to lower the melting point and improve the conductivity of the electrolyte. At present, fluorite is mainly used as a raw material for preparing aluminum fluoride. However, although the industrial production of aluminum fluoride in China has the advantages of fluorite resources and does not need to use imported fluorite for production like foreign aluminum fluoride plants, the local aluminum fluoride plants continuously consume a large amount of fluorite, and in addition, a part of fluorite is exported to foreign countries and is used as ore resources, so that the fluorite belongs to nonrenewable resources and uses one minute for one minute, and the method is undoubtedly at the bottom of reducing the mineral resources in China.

In recent years, repeated construction of blind low levels of small and medium-sized aluminum fluoride plants, the macroscopic regulation and control of China to the electrolytic aluminum industry have large gaps of aluminum oxide and aluminum hydroxide, and the more and less fluorite resources are used, the higher and less the fluorite resources are, the higher and lower the price of the aluminum fluoride are, the continuous rising of the cost of the electrolytic aluminum is caused, the rising of the aluminum price is further caused, the cost of downstream production industry is increased, certain influence on the production of aluminum product related industries and the trade popularization of products in China is caused, and the market prospect is not blindly optimistic. The aluminum fluoride in the electrolytic aluminum needs to be recycled by a certain means so as to reduce the consumption of fluorite.

The overhaul slag of the aluminum electrolysis cell is solid waste discharged periodically from the aluminum electrolysis cell and is a general name for all waste lining materials and carbon-containing electrode materials removed during overhaul of the aluminum electrolysis cell. The aluminum electrolytic cell overhaul slag belongs to dangerous waste and is I-type waste which is forbidden to be randomly discarded by national regulations due to the fact that the aluminum electrolytic cell overhaul slag contains toxic fluoride and a small amount of highly toxic cyanide. With the rapid increase of environmental requirements and environmental regulations, hazardous wastes must be temporarily stored in a site with a "three-proofing" function, while harmless final disposal must be performed. Otherwise, the production unit not only bears huge environmental protection fines, but also risks shutting down at any time.

The aluminum electrolytic cell must be overhauled every 3-5 years, and about 26kg of overhaul slag of the aluminum electrolytic cell is generated every 1 ton of electrolytic aluminum according to statistics. At present, the newly added aluminum electrolysis cell overhaul slag in China is about more than 30 ten thousand tons every year. Under the prior art, electrolytic aluminum plants mostly adopt an open-air stacking or soil landfill method to treat electrolytic aluminum solid waste, not only occupy a large amount of land, but also soluble fluoride and cyanide contained in the electrolytic aluminum solid waste can flow into rivers along with rainwater and permeate into underground polluted soil, underground water and surface water, thereby causing great harm to the surrounding ecological environment, human health and growth of animals and plants.

In order to realize the harmonious development of the electrolytic aluminum industry, the overhaul residues of the aluminum electrolytic cell are not only required to be subjected to harmless treatment, but also more importantly, how to change the overhaul residues of the aluminum electrolytic cell into valuables is changed into valuable substances, useful components in the overhaul residues are extracted and recycled, the dependence of the related industries of the electrolytic aluminum on ores is reduced, particularly the dependence of the aluminum fluoride preparation industry on fluorite ores (the fluorite ores are adopted to prepare the aluminum fluoride at present and are a single source of the aluminum fluoride), the raw material source is increased, and the sustainable development of the electrolytic aluminum industry is realized. But the technical means for preparing the aluminum fluoride by the overhaul slag of the aluminum electrolytic cell is still lacked at present.

Disclosure of Invention

In order to solve the problem of lack of a method for preparing aluminum fluoride from the overhaul residues of the aluminum electrolysis cell in the background art, the invention provides a method for recovering aluminum fluoride from the overhaul residues of the aluminum electrolysis cell.

The technical scheme of the invention is as follows: a method for recovering aluminum fluoride from overhaul residues of an aluminum electrolytic cell comprises the following steps:

(1) crushing and ball-milling overhaul residues of the aluminum electrolytic cell to obtain powdery mixed waste which mainly comprises carbon materials and attachment waste on the waste cell;

(2) putting the powdery mixed waste obtained in the step (1) into a reaction kettle, adding an acidic solution into the reaction kettle, and heating, stirring and fully reacting to obtain a mixed solution;

(3) precipitating and carrying out solid-liquid separation on the mixed solution obtained in the step (2) to obtain a supernatant containing aluminum salt and hydrofluoric acid and a precipitate mainly composed of a carbon material;

(4) injecting the supernatant obtained in the step (3) into a reaction kettle, injecting sufficient aluminum hydroxide into the reaction kettle, precipitating and cooling after full reaction under heating conditions, separating out crude aluminum fluoride crystals, and then performing solid-liquid separation to obtain crude aluminum fluoride crystals;

(5) and (4) washing, filtering and drying the crude aluminum fluoride crystal obtained in the step (4) to obtain a pure aluminum fluoride product.

The reaction time in the step (2) and the step (4) is 1-3 hours.

The reaction temperature in the step (2) and the step (4) is 60-100 ℃.

The number of the ball milling meshes in the step (1) is 200-300 meshes.

The concentration of the acidic solution in the step (2) is 0.1-1 mol/L.

And (3) under the condition that the concentration of the acid solution is 0.5mol/L, the mass ratio of the powdery mixed waste material to the acid solution in the step (2) is 1: 10.

The mass ratio of the aluminum hydroxide added in the step (4) to the powdery mixed waste in the step (2) is 0.2: 1.

the acid solution is a strong acid solution with hydrogen ions capable of being completely ionized after pure acid is used for melting water.

The main component of the attachment waste in the step (1) is fluoride, and the fluoride mainly comprises cryolite, sodium fluoride and magnesium fluoride.

The invention has the advantages that: according to the method, after a series of treatment steps are carried out on the overhaul residues of the aluminum electrolytic cell, aluminum fluoride products which are greatly required in the electrolytic aluminum industry can be prepared, the sources of the aluminum fluoride products are increased, the fluorine element is recycled in the electrolytic aluminum industry, the requirement of fluorite is reduced, the sustainable development of the electrolytic aluminum industry is facilitated, and the method has high economic benefit and popularization value. Meanwhile, the byproduct mainly composed of carbon materials separated in the preparation process can also be extracted by a certain extraction method to obtain a fireproof carbon material, so that the overhaul residues of the aluminum electrolysis cell are not the burden of an electrolytic aluminum plant any more and become another economic benefit growth point of the electrolytic aluminum plant, the overhaul residues of the aluminum electrolysis cell are changed into valuable, and the production cost of the electrolytic aluminum plant can be effectively reduced.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.