Alcan Research and Development Limited

Alcan International Limited

Frederick W Southam

Ernest W Dewing

Raman Radha Sood

Jean-Paul R Huni

Narasimha S Raghavan

A method of making fine particulate aluminum nitride, including the steps of reacting gaseous aluminum trichloride with aluminum-containing metallic material at elevated temperature to convert some of the trichloride to monochloride gas; introducing a gaseous nitrogen source to the monochloride-containing gas for reacting nitrogen with the monochloride to form fine particulate aluminum nitride; conducting a flow of gas comprising aluminum trichloride having the particulate nitride entrained therein to a cooling locality; there condensing the trichoride and accumulating the condensed trichloride and particulate nitride; and periodically reevaporating and removing the trichloride from the cooling locality for separating out and recovering the accumulated nitride.

Methods of making fine particulate aluminum nitride

In a process for the treatment of fume-laden carbon monoxide evolved in carbothermic reduction of alumina the fume-laden gas is contacted with particulate carbon in a fluidized bed maintained at a temperature, preferably in the range 2010.degree.-2050.degree. C. and above that at which sticky aluminium oxycarbide forms. The temperature of the bed is most conveniently controlled by the rate at which fresh carbon feed material is added to the bed. The hot gas emerging from the bed is rapidly chilled to a temperature below the solidification point of aluminium oxycarbide. This is most conveniently achieved by contact with a large excess of cool alumina/carbon mix in a stream which is continuously circulated through a heat exchange stage.

Carbothermic production of aluminium

In a process for production of aluminium metal carbon monoxide gas evolved at very high temperature through reaction of aluminium carbide and alumina is cooled by contact with a molten alumina slag at a lower temperature to cause back reaction of contained aluminium suboxide and Al vapor and consequent heat transfer to the contacted molten alumina slag.

A process for the production of aluminium in two steps:

Process for the production of aluminium

In a apparatus for the production of aluminium a molten alumina slag, containing combined carbon is circulated through one or more alternately arranged relatively low temperature zones where carbon is added to increase the combined carbon content of the slag by reaction with the alumina slag and high temperature zones where aluminium metal is released by reaction of aluminium carbide and alumina in the slag with consequent depletion of the combined carbon content. Alumina is supplied to the slag at one or more locations. The energy to drive the reactions is preferably supplied by resistance heating of the slag particularly in transit from a low temperature zone to a high temperature zone although usually additional energy is supplied to the slag in the return from a high temperature zone to the next low temperature zone. In most instances the aluminium-liberating reaction is carried out in an upwardly inclined passage and the gas evolved is employed to achieve the circulatory movement of the slag. It is a preferred feature to scrub the gas with carbon without admixed alumina to avoid formation of sticky aluminium oxycarbide in the carbon, which is subsequently added as process charge.

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Kingston, Canada

Frederick W Southam