Properties of refractory materials for primary aluminum production electrolyzers

Abstract

Results are provided for a study of changes in the properties of barrier materials during laboratory and industrial tests. Some autopsy results are presented for electrolyzers with a different service life. Directions are indicated for improving barrier layer properties in electrolyzers due to the use of new technology and equipment intended for vibration compaction of materials directly in electrolyzer socles.The service life of electrolyzers and the stability of their operation depend to a considerable extent on the properties of barrier materials used in electrolyzers in order to protect thermal insulation from corrosive components of the electrolyzer bath. Currently considerable operating experience has been accumulated with different materials that show the most popular barrier materials remain aluminosilicate refractories. Highly dense chamotte objects, of different dimensions produced by compaction at high pressure are used extensively in electrolyzer construction. However, as a result of double heat treatment, high wear of the die and the requirement for minimizing tolerances the cost of these components is quite high [1]. At the same time presence of joints does not resolve the problem of providing high gas-tight barrier layers. An increase in barrier component dimensions gives rise to a requirement for using special vacuum-lifts, which complicates the assembly operation, although the number of joints remains quite high.Unmolded materials currently used in the form of barrier mixes do not have joints, they exhibit increased technological efficiency, including higher assembly productivity, and in the absence of water the possibility of assembling barrier layers of different dimensions and shape. However, the production technology used does not make it possible to obtain a highly dense layer. Open porosity is quite high and it is normally 25 -27%, which leads to increased capillary penetration of corrosive component liquids into barrier and the underlying thermal insulation layers, and also reduces the amount of reacting material within the volume of the protective layer. In addition, an increase in porosity causes a number of negative phenomena connected with penetration of gaseous components.Interaction of liquid components of electrolyzer baths infiltrating through the hearth blocks with aluminosilicate material has been described sufficiently in publications [2 -6]. However, features of the reaction of barrier layers with gaseous components has not been aired in sufficient detail. Of recent publications the article of Norwegian researchers [7] should be noted in which volumetric changes in the lining of electrolyzers under the action of gaseous sodium are considered. In the article in [8] transformation is described for the same type of barrier mix in electrolyzers differing in service life and structural features, which is due to the occurrence of both liquid phase and gas phase processes; alongside analysis of gas phase processes data are provided for the possibility of increasing the life of unmolde...

Mechanism of aluminum carbide formation in aluminum electrolysis cells

“…The generated reaction of Al4C3 can also proceed in the presence of NaF and aluminum because NaF easily reacts with aluminum to form metal sodium (Eqs. 7 and 8) when temperatures exceed 900°C [29][30][31], as given by Al+3NaF=AlF3+3Na…”

Study of the mineral and phase composition of aluminosilicate refractory ShPDM-45 after service in an aluminum electrolyzer of OAO Zaporozh’e aluminum combine

“…Operating experience indicates that the most popular barrier materials remain aluminosilicate refractories [1]. On the basis of work given in publications [2 -5] and according to the resolution of the Technical Council of the Zaporozhe Aluminum Combine for replacement of refractory ShA-5, that exhibits low operating indices, the refractory lining used was chamotte dense blast-furnace objects grade ShPD M -45 with additions of mullite-corundum chamotte.…”

“…AlF 3 and chiolite (decomposition products of NaAlF 4 in post-reaction material) are recorded in [1] with an excess of them, and with a deficiency there are products of their reaction with entering sodium vapor, predominantly cryolite and aluminum, recorded in intermetallics or oxidized to Al 2 O 3 [1].…”