Abstract:
The present document describes methods for drying an aqueous priming coating composition covering an external surface exposed to air of a carbon material, or an aqueous coating composition covering an intermediate substrate covering an external surface exposed to air of a carbon material, to form a layer thereon. Also described are systems for drying a coating composition covering a surface of a carbon material.
Abstract:
The amount of electrically conductive material in the bottom floor lining of a conventional aluminum reduction cell is reduced by using a non-conductive lining material in its place. The non-conductive material separates the remaining electrically conductive regions from the sidewall linings of the cell and preferably confines the electrically conductive material to the "anode shadow" region of the cell floor. The non-conductive material preferably comprises a particulate alumina mixture made up of large shapes which firmly compact together and smaller particles which fill the remaining voids. Optionally, the mixture may be bonded together with amorphous alumina, in which case the mixture can also be used for cell wall linings. The linings can be used in reduction cells of conventional design and reduces undesirable magnetohydrodynamic effects as well as pollution hazards caused by conventional carbonaceous cell linings.
Abstract:
A refractory composition for use in contact with molten aluminum and molten aluminum alloys containing a refractory aggregate, a binder, and a treatment additive comprising a source of Sr. Methods comprising contacting a refractory composition with the Sr source to improve the resistance of the refractory to molten aluminum attack are also disclosed. Preferred treatment agents comprise Sr nitrate, Sr carbonate, Sr sulfate and Sr oxide.
Abstract:
The non-destructive testing of materials, particularly coarse grain materials such as the carbonaceous materials used in the anodes and cathodes of an aluminium smelting furnace, using longitudinal compression waves employs a waveguide to apply the waves to a specimen, the and specimen having a cross-sectional dimension Dg of between 3 and 5 times the material average grain size Dg. Alternatively, or in addition, the waves used preferably are of effective wavelength from about 30Ds to 50Ds. Alternatively, or in addition, the effective wavelength of the waves is preferred to be approximately equal to the length of the sample; the necessary very long samples may be obtained by connecting a plurality of smaller elementary samples end-to-end. The apparatus may include a controllable furnace for cycling the sample to determine the change with temperature of the physical characteristic that is being measured. The methods and apparatus employ relatively low frequencies, in the sonic range, and high powers; although particularly suited for measurements with coarse grain materials they are also very effective with more usual fine grain materials, such as ceramics.
Abstract:
The amount of electrically conductive material in the bottom floor lining of a conventional aluminum reduction cell is reduced by using a non-conductive lining material in its place. The non-conductive material separates the remaining electrically conductive regions form the sidewall linings of the cell and preferably confines the electrically conductive material to the "anode shadow" region of the cell floor. The non-conductive material preferably comprises a particulate alumina mixture made up of large shapes which firmly compact together and smaller particles which fill the remaining voids. Optionally, the mixture may be bonded together with amorphous alumina, in which case the mixture can also be used for cell wall linings. The linings can be used in reduction cells of conventional design and reduces undesirable magnetohydrodynamic effects as well as pollution hazards caused by conventional carbonaceous cell linings.
Abstract:
A thermocouple shield assembly comprising a first tube having an upper portion and a lower portion with a lower end, the first tube including a first elongated cavity closed at the lower end and receiving the thermocouple, a second tube having a second elongated cavity with at least one open end and receiving the upper portion while a part of the lower portion containing the thermocouple extends out of the open end, and a gap between adjacent walls of the second elongated cavity and of the first tube such as to allow independent thermal deformations of the first and second tubes. In use, at least a portion of the part of the lower portion of the first tube is subjected to a given temperature while the second tube is subjected to a different temperature. Methods of manufacturing and of assembling such a thermocouple shield assembly are also presented.
Abstract:
For heterogeneous materials such as refractories and carbon electrodes, the measurement the elastic properties of the material is difficult to achieve with high level of repeatability. The present invention is directed to a method and system for the elastic properties measurement of a material including the Elastic and Shear Modulus, as well as the Poisson's ratio of heterogeneous materials, at room and high temperature, according to a non destructive acoustic technique. The system comprises impacting devices for impacting a sample of the material so as to produce acoustic vibrations in the sample; acoustic detection devices so positioned relatively to the sample and the impacting device to capture the acoustic vibrations and to produce signals indicative of the acoustic vibrations; and a controller coupled to both the impacting devices and the acoustic detection device for controlling the impacting device, for receiving the signals from the acoustic detection devices and for using the signals to determine an elastic property of the material.
Abstract:
A barrier layer for prevention of solid fluorides penetration, e.g. NaF, from the interior of an aluminum production cell holding a fluoride-containing melt into a refractory layer intended to provide heat and electrical insulation for the cell. The barrier layer contains CaO, which may be derived from a CaO precursor such as calcite (CaCO.sub.2) by decomposition during cell start-up. Since CaO does not appear to react with sodium fluoride (NaF), and indeed according to thermodynamic calculations seems incapable of doing so at cell operating temperatures, it is effective for preventing the penetration of that compound when the latter is in the solid state. The barrier layer makes it possible to use insulating low cost refractories which are attacked by solid fluorides in the cell wall lining with improvement of the life of such materials. The barrier layer also keeps fluorides out of the refractory materials so that these materials can be disposed of in conventional land-fill sites without risk of causing pollution due to leaching of fluoride salts.
Abstract:
A method of manufacturing a shield assembly for protecting a thermocouple including assembling a first mold including a tubular shield having a cavity for receiving the thermocouple, assembling a second mold having a second tubular shield having a second elongated cavity with an open end, filling the first and second mold cavities with a liquid mix of refractory ceramic material and letting the liquid mix dry and thereafter disassembling the first and second molds to free the first and second tubular shields and curing the refractory ceramic material.
Abstract:
A thermocouple shield assembly comprising a first tube having an upper portion and a lower portion with a lower end, the first tube including a first elongated cavity closed at the lower end and receiving the thermocouple, a second tube having a second elongated cavity with at least one open end and receiving the upper portion while a part of the lower portion containing the thermocouple extends out of the open end, and a gap between adjacent walls of the second elongated cavity and of the first tube such as to allow independent thermal deformations of the first and second tubes. In use, at least a portion of the part of the lower portion of the first tube is subjected to a given temperature while the second tube is subjected to a different temperature. Methods of manufacturing and of assembling such a thermocouple shield assembly are also presented.