Electrolytic aluminum hazardous waste treatment system

Abstract

The utility model relates to the technical field of electrolytic aluminum hazardous waste treatment, in particular to an electrolytic aluminum hazardous waste treatment system which comprises four stirring tanks, a hydrochloric acid storage tank and a sodium carbonate storage tank. A second stirring tank is arranged at the rear end of the first stirring tank, overhaul slag powder and hydrochloric acid are added into the first stirring tank, and a liquid phase obtained after reaction in the first stirring tank enters the second stirring tank; hydrochloric acid, aluminum ash powder and electrolyte slurry are added into the second stirring tank, and a third stirring tank and a fourth stirring tank are arranged at the rear end of the second stirring tank; a liquid component obtained after reaction in the second stirring tank is introduced into a third stirring tank, a solid component obtained after reaction is added into a fourth stirring tank, sodium carbonate is added into the third stirring tank to obtain lithium carbonate, and hydrochloric acid and aluminum ash powder are added into the fourth stirring tank to obtain aluminum fluoride. According to the electrolytic aluminum solid hazardous waste treatment system, comprehensive treatment of electrolytic aluminum solid hazardous waste can be achieved, harmlessness and recycling of the electrolytic aluminum solid hazardous waste are achieved, and resource saving and environment protection are facilitated.

Description

Technical Field

[0001] The utility model relates to the technical field of electrolytic aluminum hazardous waste treatment, and in particular to an electrolytic aluminum hazardous waste treatment system. Background Art

[0002] Electrolytic aluminum is the process of extracting metallic aluminum from alumina through electrolysis. Metallic aluminum is relatively active and exists in the form of metal oxides in nature. It is difficult to prepare metallic aluminum using traditional methods. In industrial production, it can only be prepared through electrolysis. Since metallic aluminum products are widely used, the electrolytic aluminum industry plays a significant role in the process of social development.

[0003] However, a large amount of hazardous waste is generated in the process of preparing metallic aluminum through electrolysis, such as overhaul slag, aluminum ash, carbon slag, etc.; among them, overhaul slag is the waste slag generated by the maintenance and replacement of the cathode lining of the electrolytic cell in the production of electrolytic aluminum, which is mainly composed of waste cathode carbon blocks, waste refractory materials, waste cathode steel bars and cathode ash, and contains a large amount of soluble fluorides. If not properly disposed of, it will cause great environmental damage and safety hazards; aluminum ash is the aluminum ash slag generated on the surface of the melt during the processes of aluminum liquid transfer, refining, alloying, casting, etc. in the production of electrolytic aluminum, as well as the salt slag and secondary aluminum ash slag generated in the process of aluminum recovery, which contains a large amount of metallic aluminum and aluminum compounds. Aluminum nitride and carbide in the aluminum ash Ammonia and methane generated by the reaction of aluminum and water are harmful to humans and pose a threat to the ecological environment. Carbon slag is mainly waste generated by the shedding of carbon particles caused by uneven combustion and selective oxidation of carbon anodes, or the shedding of carbon particles from carbon cathodes under the erosion and scouring of aluminum liquid and electrolytes. In addition to containing 20-30% carbon, it also contains 60-70% electrolyte, of which the main components of the electrolyte are Na3AlF6, AlF3 and LiF, etc., which are also very harmful to the environment and human body. The traditional treatment method is crushing and then flotation to obtain carbon powder and electrolyte, and then further treat the electrolyte.

[0004] According to statistics, every ton of electrolytic aluminum produced will produce 15-20kg of overhaul slag, 6.3-10kg of aluminum ash, and 10-12kg of carbon slag. The total amount of typical hazardous solid wastes such as overhaul slag, aluminum ash and carbon slag generated by my country's electrolytic aluminum enterprises each year exceeds 1.2 million tons. If not properly disposed of, it will cause great environmental damage and safety hazards, and will also cause the loss of resources. Therefore, a treatment system that can dispose of electrolytic aluminum hazardous waste to achieve harmlessness and resource utilization of electrolytic aluminum hazardous waste is an urgent problem to be solved. Utility Model Content

[0005] The purpose of the utility model is to provide an electrolytic aluminum hazardous waste treatment system in view of the deficiencies of the above-mentioned prior art, so as to achieve the comprehensive treatment of electrolytic aluminum hazardous waste, thereby realizing the purpose of harmless treatment and resource utilization of electrolytic aluminum hazardous waste.

[0006] To achieve the above-mentioned purpose, the utility model adopts the following technical scheme: a system for treating hazardous waste from electrolytic aluminum, comprising a first stirring tank, wherein a first hydrochloric acid inlet and an overhaul slag powder inlet are provided on the first stirring tank, a first slurry outlet is provided at the bottom of the first stirring tank, and the first slurry outlet is connected to a first filter press; the filtrate of the first filter press is passed into a second stirring tank, a first filtrate inlet is provided on the second stirring tank, and the first filtrate inlet is connected to the first filter press; an electrolyte slurry inlet, a second hydrochloric acid inlet and a first aluminum ash powder inlet are also provided on the second stirring tank, a second slurry outlet is provided at the bottom of the second stirring tank, and the second slurry outlet is connected to the second filter press; the second filter press is connected to a third stirring tank, a second filtrate inlet is provided on the third stirring tank, and the second filtrate inlet is connected to the second filter press; a sodium carbonate inlet is also provided on the third stirring tank, and a third slurry outlet is provided at the bottom of the third stirring tank.

[0007] Furthermore, the third slurry outlet is connected to a third filter press.

[0008] Furthermore, the second filter press is also connected to the fourth stirring tank, and a second filter residue inlet is provided on the fourth stirring tank, and the second filter residue inlet cooperates with the second filter press; a third hydrochloric acid inlet and a second aluminum ash powder inlet are also provided on the fourth stirring tank, and a fourth slurry outlet is provided at the bottom of the fourth stirring tank.

[0009] Furthermore, the fourth slurry outlet is connected to a fourth filter press.

[0010] Furthermore, the first hydrochloric acid inlet, the second hydrochloric acid inlet and the third hydrochloric acid inlet are respectively connected to the hydrochloric acid storage tank.

[0011] Furthermore, the sodium carbonate inlet is connected to a sodium carbonate storage tank.

[0012] Beneficial effects of the utility model:

[0013] 1. It can realize the comprehensive treatment of solid hazardous waste from electrolytic aluminum, realize the harmlessness and resource utilization of solid hazardous waste from electrolytic aluminum, and is conducive to resource conservation and environmental protection;

[0014] 2. The method of dissolving lithium first and then sodium is helpful for the precipitation of lithium ions and the improvement of the yield of lithium carbonate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the connection of various devices of the utility model;

[0016] Figure 2 It is a schematic diagram of the overall structure of the utility model;

[0017] Figure 3 This is a schematic diagram of the structure of the hydrochloric acid storage tank of the utility model;

[0018] Figure 4 It is a schematic diagram of the structure of a sodium carbonate storage tank of the utility model.

[0019] The names corresponding to the marks in the figure are:

[0020] 1. First stirring tank; 11. First hydrochloric acid inlet; 12. Overhaul slag powder inlet; 13. First slurry outlet; 2. First filter press; 3. Second stirring tank; 31. Second hydrochloric acid inlet; 32. First filter press inlet; 33. Electrolyte slurry inlet; 34. First aluminum ash powder inlet; 35. Second slurry outlet; 4. Second filter press; 5. Third stirring tank; 51. Second filter press inlet; 52. Sodium carbonate inlet; 53. Third slurry outlet; 6. Third filter press; 7. Fourth stirring tank; 71. Third hydrochloric acid inlet; 72. Second filter residue inlet; 73. Second aluminum ash powder inlet; 74. Fourth slurry outlet; 8. Fourth filter press; 9. Hydrochloric acid storage tank; 91. First hydrochloric acid outlet; 92. Second hydrochloric acid outlet; 93. Third hydrochloric acid outlet; 10. Sodium carbonate storage tank; 101. Sodium carbonate outlet. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the utility model.

[0022] Embodiments of the present utility model:

[0023] like Figure 1-4 As shown, in this embodiment, the first stirring tank 1 is connected to the first filter press 2, and the first filter press 2 is connected to the second stirring tank 3, wherein a first hydrochloric acid inlet 11 and an overhaul slag powder inlet 12 are arranged above the first stirring tank 1, and a first slurry outlet 13 is arranged at the bottom of the first stirring tank 1, and the first slurry outlet 13 is connected to the first filter press 2, and the filtrate of the first filter press 2 is passed into the second stirring tank 3.

[0024] A first filtrate inlet 32 ​​is provided above the second stirring tank 3, and the first filtrate inlet 32 ​​is connected to the first filter press 2. A second hydrochloric acid inlet 31, an electrolyte slurry inlet 33 and a first aluminum ash powder inlet 34 are also provided on the second stirring tank 3; a second slurry outlet 35 is provided at the bottom of the second stirring tank 3, and the second slurry outlet 35 is connected to the second filter press 4, and the second filter press 4 is respectively connected to the third stirring tank 5 and the fourth stirring tank 7.

[0025] The filtrate from the second filter press 4 is introduced into the third stirring tank 5, a second filtrate inlet 51 is correspondingly provided above the third stirring tank 5, a sodium carbonate inlet 52 is also provided above the third stirring tank 5, a third slurry outlet 53 is provided at the bottom of the third stirring tank 5, the third slurry outlet 53 is connected to the third filter press 6, and the solid component obtained by the third filter press 6 is lithium carbonate.

[0026] The filter residue of the second filter press 4 is added to the fourth stirring tank 7, and a second filter residue inlet 72 is correspondingly arranged above the fourth stirring tank 7, and a third hydrochloric acid inlet 71 and a second aluminum ash powder inlet 73 are also arranged above the fourth stirring tank 7, and a fourth slurry outlet 74 is arranged at the bottom of the fourth stirring tank 7, and the fourth slurry outlet 74 is connected to the fourth filter press 8, and the solid component obtained by the fourth filter press 8 is aluminum fluoride.

[0027] The first stirring tank 1, the second stirring tank 3, the third stirring tank 5 and the fourth stirring tank 7 are all provided with stirring devices; the first hydrochloric acid inlet 11, the second hydrochloric acid inlet 31 and the third hydrochloric acid inlet 71 are respectively connected to the hydrochloric acid storage tank 9; the hydrochloric acid storage tank 9 is respectively provided with a first hydrochloric acid outlet 91, a second hydrochloric acid outlet 92 and a third hydrochloric acid outlet 93, and the hydrochloric acid inlets and the hydrochloric acid outlets correspond one to one; the sodium carbonate inlet 52 is connected to the sodium carbonate storage tank 10, and the sodium carbonate outlet 101 is provided on the sodium carbonate storage tank 10, and the sodium carbonate outlet 101 corresponds to the sodium carbonate inlet 52.

[0028] The principle of this utility model is:

[0029] The overhaul slag powder and aluminum ash powder involved in the utility model are obtained by crushing the overhaul slag and aluminum ash respectively, and the electrolyte slurry is obtained by flotation of carbon slag.

[0030] The main components of the overhaul slag are refractory materials and electrolytes, among which the electrolyte mainly contains Na3AlF6, Li3AlF6, etc. Under the condition of hydrochloric acid, Na3AlF6 and Li3AlF6 react with hydrochloric acid in the first stirring tank 1, and the reaction mechanism is as follows:

[0031] Li3AlF6+3HCl=3LiCl+3HF+AlF3↓

[0032] Na3AlF6+3HCl=3NaCl+3HF+AlF3↓

[0033] In this step, the amount of hydrochloric acid is controlled to be excessive, so that the fluorine and lithium in the overhaul slag can be dissolved, and the aluminum fluoride generated by the reaction is mixed with the refractory material that does not participate in the reaction and discharged from the reaction system through solid-liquid separation.

[0034] It should be noted that in this step, lithium ions will dissolve before sodium ions, but for overhaul slag, the purpose is to dissolve fluorine and lithium. Therefore, there is no need to subdivide in this step, and it is sufficient to control the excess of hydrochloric acid.

[0035] The main components of carbon slag are carbon powder and electrolyte. The carbon powder and electrolyte can be separated by a flotation machine. The separated electrolyte slurry is introduced into the second stirring tank 3. The amount of hydrochloric acid added is controlled so that the reaction stays at the lithium dissolving stage. A portion of aluminum ash powder (mainly composed of aluminum oxide) is added to neutralize the hydrofluoric acid generated by the reaction. The reaction mechanism is as follows:

[0036] Li3AlF6+3HCl=3LiCl+3HF+AlF3↓

[0037] Al2O3+6HF=3H2O+2AlF3↓

[0038] After the above reaction is completed, solid-liquid separation is performed to obtain a solid component and a liquid component, wherein the solid component contains Na3AlF6 and aluminum fluoride, and the liquid component is enriched with lithium chloride. The liquid component is introduced into the third stirring tank 5, and sodium carbonate solution is added to the third stirring tank 5, so that lithium carbonate can be obtained after solid-liquid separation. The mechanism is as follows:

[0039] 2LiCl+Na2CO3=2NaCl+Li2CO3↓

[0040] The solid component obtained by the above reaction is added to the fourth stirring tank 7, and hydrochloric acid is continuously added to the fourth stirring tank 7, so that the sodium ions can be dissolved, and aluminum ash powder is added to neutralize the hydrofluoric acid generated by the reaction, and aluminum fluoride can be obtained after solid-liquid separation. The mechanism is as follows:

[0041] Na3AlF6+3HCl=3NaCl+3HF+AlF3↓

[0042] Al2O3+6HF=3H2O+2AlF3↓

[0043] Therefore, through the treatment system of the utility model, it is possible to treat solid hazardous wastes such as overhaul slag, carbon slag (the electrolyte slurry of the utility model is obtained after carbon slag flotation, which is a common treatment method currently available) and aluminum ash produced by electrolytic aluminum, and obtain lithium carbonate and aluminum fluoride, thereby achieving harmlessness and resource utilization of solid hazardous wastes of electrolytic aluminum, which is beneficial to resource conservation and environmental protection.

[0044] It should be noted that in the present invention, the reaction process will be accompanied by the generation of hydrofluoric acid, such as hydrofluoric acid is generated in the first stirring tank 1, the second stirring tank 3 and the fourth stirring tank 7. Therefore, in actual production, the corrosion resistance of the equipment of the present invention is relatively high. For example, the first stirring tank 1, the second stirring tank 3, the fourth stirring tank 7 and the material conveying pump can adopt a polyfluoro lining. At the same time, the first filter press 2 and the second filter press 4 also need to be anti-corrosion. Materials resistant to hydrofluoric acid corrosion can be used, such as Monel 400 alloy widely used in industry. For the anti-corrosion of the present invention, the equipment and technology in the existing technology are mature and will not be repeated here.

Claims

1. A system for treating hazardous waste from electrolytic aluminum, characterized by: The invention comprises a first stirring tank (1), wherein the first stirring tank (1) is provided with a first hydrochloric acid inlet (11) and an overhaul slag powder inlet (12), and the bottom of the first stirring tank (1) is provided with a first slurry outlet (13), and the first slurry outlet (13) is connected to a first filter press (2); the filtrate of the first filter press (2) is passed into a second stirring tank (3), and the second stirring tank (3) is provided with a first filtrate inlet (32), and the first filtrate inlet (32) is connected to the first filter press (2); the second stirring tank (3) is also provided with an electrolyte slurry inlet (33) , a second hydrochloric acid inlet (31) and a first aluminum ash powder inlet (34); a second slurry outlet (35) is provided at the bottom of the second stirring tank (3), and the second slurry outlet (35) is connected to the second filter press (4); the second filter press (4) is connected to the third stirring tank (5), and a second filtrate inlet (51) is provided on the third stirring tank (5), and the second filtrate inlet (51) is connected to the second filter press (4); a sodium carbonate inlet (52) is also provided on the third stirring tank (5), and a third slurry outlet (53) is provided at the bottom of the third stirring tank (5).

2. The electrolytic aluminum hazardous waste treatment system according to claim 1 is characterized by: The third slurry outlet (53) is connected to the third filter press (6).

3. The electrolytic aluminum hazardous waste treatment system according to claim 1 is characterized by: The second filter press (4) is also connected to the fourth stirring tank (7), and a second filter residue inlet (72) is provided on the fourth stirring tank (7), and the second filter residue inlet (72) cooperates with the second filter press (4); a third hydrochloric acid inlet (71) and a second aluminum ash powder inlet (73) are also provided on the fourth stirring tank (7), and a fourth slurry outlet (74) is provided at the bottom of the fourth stirring tank (7).

4. The electrolytic aluminum hazardous waste treatment system according to claim 3 is characterized by: The fourth slurry outlet (74) is connected to the fourth filter press (8).

5. A system for treating hazardous waste from electrolytic aluminum according to any one of claims 1 to 3, characterized in that: The first hydrochloric acid inlet (11), the second hydrochloric acid inlet (31) and the third hydrochloric acid inlet (71) are respectively connected to the hydrochloric acid storage tank (9).

6. The electrolytic aluminum hazardous waste treatment system according to claim 1 is characterized by: The sodium carbonate inlet (52) is connected to the sodium carbonate storage tank (10).

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