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Refractory coating for components of and aluminum electrolysis cess

An electrolytic cell and refractory technology, applied in the field of refractory coatings

Inactive Publication Date: 2003-03-05
ALCAN INT LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The lifetime of the carbon lining or cathode material is typically about 3-8 years on average, but may be shorter under adverse conditions

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0020] A coating slurry was prepared by mixing together 16% by weight water, 14% by weight solid oxalic acid, 65% by weight titanium diboride particles, and 5% by weight electrostatic precipitator dust. An exothermic reaction occurred during mixing.

[0021] The slurry was sprayed onto a 5 cm x 7 cm x 2 cm cathode block with a thickness of 1-2 mm. The coated pieces were then heated for 10 minutes to dry the coating.

[0022] The refractory coated cathode block was then placed in a laboratory electrolysis cell with a 3 cm separation between the anode and cathode. The bath contains NaF and AlF in a ratio of 1.25:1 3 , and kept at a temperature of 960°C. A 30 amp direct current of 2.8 volts was applied and 27 g of alumina was added to the bath over 2.5 hours.

[0023] The experiment was run for 24 hours, at which time the entire surface of the cathode was wetted by the aluminum.

Embodiment 2

[0025] Following the same procedure as in Example 1, a coating slurry containing 15% by weight of water, 10% by weight of solid oxalic acid, 65% by weight of titanium diboride particles and 10% by weight of electrostatic precipitator dust was prepared. The slurry was sprayed onto a 5 cm x 7 cm x 2 cm cathode block with a thickness of 1-2 mm. The coated pieces were then heated for 10 minutes to dry the coating.

[0026] Following the same procedure as Example 1, the refractory coated blocks were tested in a laboratory electrolytic cell with a bath temperature of 966°C. The experiment was terminated after 24 hours, at which point the entire surface of the cathode was wetted by the aluminum.

Embodiment 3

[0028] In this experiment, 25% by weight of a 15% aqueous solution of oxalic acid, 65% by weight of titanium diboride particles, and 10% by weight of electrostatic precipitator dust were mixed together to prepare a coating slurry. During mixing, the slurry was sprayed onto a 5 cm x 7 cm x 2 cm cathode block to a thickness of 1-2 mm. The coated pieces were then heated for 10 minutes to dry the coating.

[0029] Following the same procedure as Example 1, the refractory coated blocks were tested in a laboratory electrolytic cell with a bath temperature of 970°C. The experiment was terminated after 24 hours, at which point the entire surface of the cathode was wetted by the aluminum.

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PUM

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Abstract

The present invention provides a refractory coating for a component of an electrolytic cell for the production of aluminum in which an aqueous slurry is prepared comprising particulate refractory material, e.g. TiB2, dispersed in an aluminum oxalate complex. The slurry is applied as a coating to the surface of the component, e.g. a cathode block, and dried to form a hard refractory surface on the component. The aluminum oxalate complex may be formed in situ during production of the slurry by mixing together oxalic acid and electrostatic precipitator dust comprising aluminum oxide. After the refractory coated component is immersed in a high temperature cryolite bath of an aluminum electrolysis cell, the aluminum oxalate complex is converted to alumina which bonds the refractory particles to the surface of the cell component.

Description

technical field [0001] The present invention relates to a process for the preparation of refractory coatings for electrolytic cells used in the production of aluminum by the electrolysis of alumina dissolved in molten electrolyte, such as cryolite or other fluoride-based electrolytes. The invention more particularly relates to slurries for preparing refractory coatings and electrolytic cell components coated with refractory materials. Background technique [0002] Aluminum production is usually carried out by the Hall-Heroult electrolytic reduction method, in which alumina is dissolved in molten cryolite and electrolyzed at a temperature of about 900-1000°C. The method is carried out in a reduction tank, which generally comprises a stainless steel shell provided with an insulating lining made of a suitable refractory material which in turn further comprises a carbon lining in contact with the molten components. One or more anodes, usually made of carbon, are connected to th...

Claims

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Application Information

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IPC IPC(8): C25C3/08C04B41/50C04B41/87
CPCC04B41/87C04B41/009C04B41/507C04B2111/00879C25C3/08C04B41/4539C04B41/4554C04B41/5031C04B35/52
Inventor J·-P·胡尼K·I·锡A·A·米特奇J·伯格伦
Owner ALCAN INT LTD
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