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Chemical Durability of Thermal Insulating Materials in Hall-Héroult Electrolysis Cells

1
Department of Materials Science and Engineering, NTNU Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
2
Skamol A/S, Sletvej 2C, DK-8310 Tranbjerg, Denmark
3
SINTEF Industry, NO-7465 Trondheim, Norway
*
Author to whom correspondence should be addressed.
Ceramics 2019, 2(3), 441-459; https://doi.org/10.3390/ceramics2030034
Received: 20 May 2019 / Revised: 16 June 2019 / Accepted: 28 June 2019 / Published: 8 July 2019
The most common thermal insulating materials used in the cathode lining in aluminum electrolysis cells are Moler (diatomaceous earth), calcium silicate, or vermiculite based materials. The thermal insulation layer is critical for the overall thermal stability of the cell and is vulnerable to volatile species, such as sodium vapor, that may penetrate through the carbon cathode and refractory layer. Here, we present an investigation of the chemical degradation of typical thermal insulating materials by exposure to sodium vapor in a laboratory test. Changes in microstructure and chemical and mineralogical composition of the exposed materials were characterized by electronic microscopy and powder X-ray diffraction. The materials possess different reaction patterns, ranging from deformation by creep to formation of a glassy layer reducing further sodium penetration. The results from the laboratory test were compared with chemical reactions with sodium predicted by computational thermodynamics and discussed with respect to relevant ternary phase diagrams. View Full-Text
Keywords: thermal insulating materials; aluminum electrolysis cell; sodium vapor; Moler; calcium silicate; vermiculite; degradation thermal insulating materials; aluminum electrolysis cell; sodium vapor; Moler; calcium silicate; vermiculite; degradation
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Luneng, R.; Bertel, S.N.; Mikkelsen, J.; Ratvik, A.P.; Grande, T. Chemical Durability of Thermal Insulating Materials in Hall-Héroult Electrolysis Cells. Ceramics 2019, 2, 441-459.

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