Method for preparing cryolite by alkaline leachate of cathode carbon block of aluminum electrolytic cell

A cathode carbon block and aluminum electrolytic cell technology, which is applied in aluminum fluoride, aluminum halide and other directions, can solve the problems of alkali leaching solution pollution of cathode carbon block in aluminum electrolytic cell, shortening of the process, etc.

Inactive Publication Date: 2017-05-31
CENT SOUTH UNIV
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  • Summary
  • Abstract
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  • Application Information

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Problems solved by technology

[0007] In order to solve the pollution problem of the alkaline leaching solution of the cathode carbon block of the aluminum electrolytic cell and the problems existing in the prior art, the present invention proposes a method for prod

Method used

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Experimental program
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Effect test

Embodiment 1

[0070] Grind 100g of aluminum electrolytic cell cathode carbon block to -200 mesh and account for 75% of the total particle weight, then mix it with NaOH solution with a mass fraction of 20% according to the liquid-solid mass ratio of 6:1, and prepare the slurry at a heating temperature of 60°C. The leaching was carried out for 1.5 h under the condition of a stirring rate of 180 r / min, and the first filtrate and the first filter residue were obtained by filtering after the reaction. Add sodium fluoride to the first filtrate to adjust Al:Na:F=1:3.1:6.3, then add 1gNa 3 AlF 6 Solid, then according to the rate of 12.5L / h, pass into the rich CO of 55% purity 2 Gas, at 70°C, 170r / min to form a precipitate, react for 30min, filter to obtain the second filtrate and the second filter residue, and dry the second filter residue at 120°C to obtain the cryolite product. Finally, 35.64 g of cryolite with a purity of 98.35% and a molecular ratio of 3.05:1 was obtained.

Embodiment 2

[0080] Grind 100g of aluminum electrolytic cell cathode carbon block to -200 mesh, accounting for 75% of the total particle weight, and then mix it with NaOH solution with a mass fraction of 30% according to the liquid-solid mass ratio of 7:1. Leaching for 1 h under the condition of a stirring rate of 170 r / min, and filtering after the reaction to obtain the first filtrate and the first filter residue. Add sodium fluoride to the first filtrate to adjust Al:Na:F=1:3.2:6.2, then add 1.25gNa 3 AlF 6 Solid, then according to the rate of 15L / h into the 50% pure CO 2 Gas, at 80°C, 160r / min, a precipitate is formed, reacted for 20min, filtered to obtain the second filtrate and the second filter residue, and the second filter residue was dried at 110°C to obtain the cryolite product. Finally, 34.96 g of cryolite with a purity of 97.81% and a molecular ratio of 2.98:1 was obtained.

Embodiment 3

[0082] Grind 100g of aluminum electrolytic cell cathode carbon block to -200 mesh, accounting for 75% of the total particle weight, then mix it with NaOH solution with a mass fraction of 25% according to the liquid-solid mass ratio of 8:1, and prepare the slurry at a heating temperature of 70°C. The leaching was carried out for 1.25 h under the condition of a stirring rate of 200 r / min, and after the reaction was completed, the first filtrate and the first filter residue were obtained by filtering. Add sodium fluoride to the first filtrate to adjust Al:Na:F=1:3.1:6.2, then add 1.5gNa 3 AlF 6 solid, followed by 10L / h of 60% pure CO-enriched 2 Gas, at 60°C, 150r / min to form a precipitate, react for 40min, filter to obtain the second filtrate and the second filter residue, and dry the second filter residue at 110°C to obtain the cryolite product. Finally, 35.06 g of cryolite with a purity of 98.12% and a molecular ratio of 2.95:1 was obtained.

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Abstract

The invention relates to a method for preparing cryolite by alkaline leachate of a cathode carbon block of an aluminum electrolytic cell, and belongs to a leachate preparation method. The method comprises the steps of grinding the cathode carbon block of the aluminum electrolytic cell to a certain particle size, mixing the ground cathode carbon block with alkaline liquid, carrying out size mixing, carrying out stirring leaching at a heating temperature of 20-90 DEG C, filtering to obtain first filtrate and a first filter residue, adding sodium fluoride and a small amount of Na3AlF6 solids into the first filtrate, controlling the introducing velocity of CO2-rich gas to generate precipitates while heating and stirring, after the reaction is finished, filtering to obtain second filtrate and a second filter residue, and drying the second filter residue at 100-150 DEG C, so as to obtain a cryolite product. According to the method, acidy leaching is replaced with alkaline leaching, so that the equipment requirements in the production process are reduced, processing processes such as flotation are omitted, an absorption process of hydrogen fluoride is omitted, and the processing process is simplified; a high-temperature processing process is saved, so that the energy consumption is reduced; and by adding crystal seeds, high-quality cryolite with the uniform particle size is generated when airflow rate is controlled. The method has the beneficial effects that the process is simple, a closed loop is utilized, the resource utilization rate is high, and the secondary pollution is avoided.

Description

technical field [0001] The invention belongs to a method for preparing cryolite, in particular to a method for preparing cryolite by using the alkaline leaching solution of cathode carbon block of an aluminum electrolytic cell as a raw material. [0002] technical background [0003] During the production process of aluminum electrolysis, the cathode carbon block expands due to the penetration of impurities such as sodium and cryolite, which further causes damage to the electrolytic cell. Domestic aluminum electrolytic cells need to be overhauled when they are about 2000 days old. The waste cathode carbon blocks produced during the overhaul process are one of the main solid pollutants in the aluminum electrolysis industry. The statistical results of the fluorine balance survey of industrial aluminum electrolytic cells show that for every ton of electrolytic aluminum produced, about 10kg of waste cathode carbon blocks will be produced. Taking 2015 as an example, the output of...

Claims

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Application Information

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IPC IPC(8): C01F7/54
CPCC01F7/54C01P2006/80
Inventor 赖延清田忠良郭伟昌肖劲杨凯袁杰李劼
Owner CENT SOUTH UNIV
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