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A method for producing cryolite by using alkaline leaching solution 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: 2018-10-26
CENT SOUTH UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0006] 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 in the above-mentioned prior art, the present invention proposes a method for producing cryolite with the alkaline leaching solution of the cathode carbon block of the aluminum electrolytic cell, to achieve The purpose of treating waste, reducing energy consumption, shortening the process, and reducing equipment loss

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0076] 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 into the rich NH 3 Gas, to ensure that the element N:Al in the solution is 4.2:1, at 50°C and 170r / min, a precipitate is formed, 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 cryolite product. Finally, 33.58 g of cryolite with a purity of 97.65% and a molecular ratio of...

Embodiment 2

[0086] 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 15L / h into the rich NH with a purity of 60% 3 Gas, to ensure that the element N:Al in the solution is 4.2:1, at 50°C and 170r / min, a precipitate is formed, 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 cryolite product. Finally, 32.89 g of cryolite with a purity of 96.71% and a...

Embodiment 3

[0088] 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, followed by feeding 50% pure NH at a rate of 10L / h 3 Gas, to ensure that the element N:Al in the solution is 4.2:1, at 50°C and 170r / min, a precipitate is formed, 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 cryolite product. Finally, 33.21 g of cryolite with a purity of 97.07% and a molecular ratio of 2.9...

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Abstract

The invention relates to a method for preparing cryolites by using an aluminum electrolytic cell cathode carbon block alkaline leaching solution, and belongs to preparation methods of the cryolites. The method comprises the following steps: grinding aluminum electrolytic cell cathode carbon blocks finely to a certain particle size, performing slurry mixing with alkali liquor, and performing agitation leaching at a heating temperature of 20-90 DEG C; then performing filtration to obtain a first filtrate and a first filter residue; adding sodium fluoride and a small amount of Na3AlF6 solids into the first filtrate; then controlling the speed of introducing NH3-rich gas or adding NH4F to generate a deposit under the action of heating agitation; and after reaction, performing filtration to obtain a second filtrate and a second filter residue, and drying the second filter residue at 100-150 DEG C to obtain a cryolite product. According to the method provided by the invention, by replacing acid leaching with alkali leaching, the requirement of a production process on equipment is reduced, treatment processes including floatation are reduced, an absorption process of hydrogen fluoride is reduced, and the treatment process is simplified; a high-temperature treatment process is not used, so that the energy consumption is reduced; and by adding a crystal seed, high-quality cryolites with uniform particle sizes are generated under the condition that the airflow rate is controlled. The method provided by the invention is simple in process, achieves closed cycle, is high in resource utilization rate and avoids secondary pollution.

Description

technical field [0001] The invention belongs to a method for preparing cryolite, in particular to a method for producing cryolite by using the alkaline leaching solution of cathode carbon block of an aluminum electrolytic cell as a raw material. technical background [0002] 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 electro...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01F7/54
CPCC01F7/54C01P2006/80
Inventor 赖延清田忠良杨凯肖劲郭伟昌袁杰李劼
Owner CENT SOUTH UNIV