Selection of Heat-Insulating Materials for Aluminum Electrolyzers

Kaplan, F. S.; Aksel'rod, L. M.; Puchkelevich, N. A.; Yurkov, A. L.

doi:10.1023/b:refr.0000016770.69206.00

Cited by 2 publications

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“…However, in practice molten salts and aluminum may break through the protective layer or slowly infiltrate along the joints between refractory components. Diatomite bricks and vermiculite plates impregnated during service were found to contain significant amounts of cryolite (up to 15%), sodium fluoride (up to 29%), and calcium fluoride (up to 6%) [5,6]. The heat conductivity of impregnated layers of the heat insulation was found to increase by a factor of 25 to 70 reaching values of 5 to 21 W/(m × K).…”

Section: Thermal Aging Of Heat-insulating Materials and The Heat Condmentioning

confidence: 98%

“…Procedures for determining the safe operating temperature of heat-insulating materials for aluminum electrolysis cells have been described in [5]; of the whole set tested, two were recommended for use. The safe operating temperature may be established either by the softening onset point on a dilatometric curve (Fig.…”

Section: Safe Operating Temperature For Heat-insulating Materialsmentioning

confidence: 99%

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Properties of Heat-Insulating Materials (A Review)

Yurkov

Aksel'rod

2005

Refract Ind Ceram

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Heat-insulating materials for the lining of aluminum electrolysis cells based on diatomite, vermiculite, perlite, and calcium silicate are briefly reviewed. Data on heat conductivity of these materials over the range of 200 -800°C are given, with emphasis placed on the behavior in the electrolysis bath. Properties of heat-insulating materials available from domestic and foreign manufacturers are discussed in terms of the classification temperature and safe operating temperature.Despite the ready availability of a wide range of heat-insulating materials, a mere four or five of them have found application for the heat insulation of electrolysis cells. The insulators in question are lightweight chamotte products and materials based on diatomite, vermiculite, perlite, and calcium silicate. The main reason for the preference given to these materials is that they are capable of sustaining longterm mechanical loading without deformation at temperatures as high as 900°C. HEAT-INSULATING DIATOMITE-BASED MATERIALSThe high-grade diatomites contain more than 70% SiO 2 . A microporous structure (pore size 0.005 -0.01 mm across) is the main property that provides a low heat conductivity of diatomite [1,2]. To further decrease heat conductivity, combustible additives (sawdust) are introduced into the material which, as they burn out during sintering, increase the pore number. Argillaceous species that make up part of the diatomite rock impart plasticity to the molding mix and control the sintering regime and maximum permissible operating temperature of the material. As a rule, diatomite as-recovered from the quarry is used with no other minerals added; for this reason, heat conductivity and operating temperature of diatomite products purchased from various manufacturers may differ appreciably.The raw material recovered from quarries is averaged to obtain the required consistency, and sawdust is added to the mixture. Depending on the mixture consistency, extrusion or slip-casting techniques are used to prepare green performs of the needed shape; next, the green performs are sintered in a tunnel furnace. In recent years, to meet progressively more stringent size tolerances, the usual practice is to surface-finish the sintered components using diamond machining tools. HEAT-INSULATING PERLITE-BASED MATERIALSPerlite is a high-silica mineral of volcanic origin with a glass-like structure. By chemical composition, it is close to granite; it contains more than 1% water. When heated, perlite, owing to the vigorous evolution of chemically bound water, expands in volume to form a lightweight porous material. The swell ratio of perlite, depending on its occurrence, may be as high as 20. Sharp heating to 800 -900°C imparts to perlite a structure with inner isolated pores. For producing perlite-based heat-insulating materials, firing and nonfiring technologies have been developed using, for example, clay or cement binders. The maximum permissible operating temperature for insulating materials based on high-quality perlite may reach 1200°C. H...

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Section: Thermal Aging Of Heat-insulating Materials and The Heat Condmentioning

confidence: 98%

Section: Safe Operating Temperature For Heat-insulating Materialsmentioning

confidence: 99%

Properties of Heat-Insulating Materials (A Review)

Yurkov

Aksel'rod

2005

Refract Ind Ceram

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“…Bricks with a high content of alumina, that is, alumina-silica refractory materials (chamotte), consisting mainly of mullite (3Al2O3 5SiO2) and the most resistant to the effects of melt components are used as the refractory materials [9]. Diatomaceous bricks of the types PD-350, PD-400, D-500 [10] and vermiculite of different composition [11] are widely used as thermal insulation materials.…”

Section: Problem Specificationmentioning

confidence: 99%

Use of Leaching Cake from Refractory Lining of Dismantled Electrolysers in Cement Production

Petrovskiy¹,

Nemchinova²,

Tyutrin³

et al. 2019

Proceedings of the International Symposium "Engineering and Earth Sciences: Applied and Fundamental Research" Dedicated to the

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A hydrometallurgical technology has been proposed for processing the refractory part of the lining of aluminum production electrolysers dismantled and disabled for overhaul. Fluorine-containing compounds are transferred to the solution, which allows obtaining cryolite for being used in the electrolysis process. It is recommended to use solid residue from leaching (cake) with a minimum content of alkalis and fluorine as an additive to the mixture for cement production. According to the results of experiments on obtaining portland cement by traditional firing technology, the limiting content of alkali metal oxides (not higher than 4.5% by weight, calculated as Na2O) in the leaching cake was determined, the optimum content of this additive in the charge is from 5 to 12% depending on chemical composition of lime used.

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Selection of Heat-Insulating Materials for Aluminum Electrolyzers

Cited by 2 publications

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Properties of Heat-Insulating Materials (A Review)

Properties of Heat-Insulating Materials (A Review)

Use of Leaching Cake from Refractory Lining of Dismantled Electrolysers in Cement Production

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