Alcan Research and Development Limited

Alcan International Limited

Raman Radha Sood

Ernest W Dewing

Frederick W Southam

Jean-Paul R Huni

Frank John Farago

David Michael Stokes

Narasimha S Raghavan

Meine Vandermeulen

Charles J Rogers

Ethan A Hollingshead

Dale Gordon Retallack

Thomas G Edgeworth

Henry James Byrne

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

An electrolytic reduction cell for the production of molten metal by electrolysis of a molten electrolyte, which is less dense than the molten metal includes a generally rectangular shell, one or more suspended anodes and a floor structure which supports a body of the molten metal. At least one essentially linear baffle member extends transversely of the cell and is formed with restricted flow channels for absorbing energy from the molten metal and to reduce the amplitude of the wave motion in the molten metal. The baffle may be in the form of a single member formed with apertures for metal flow restriction or may be constituted by a number of separate aligned members with metal flow channels between them.

Electrolytic reduction cells

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 described in U.S. Pat. No. 4,099,959 carbon monoxide gas is evolved at very high temperature through reaction of aluminium carbide and alumina in a high temperature zone of the system. This gas 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 body of molten alumina slag is maintained in a pretreatment zone, to which carbon and alumina feed are introduced and the carbon monoxide gas is led into the pretreatment zone. Excess slag, resulting from such introduction of feed and from gaseous back reaction, spills over into a low temperature zone of the system to augment the circulating slag stream.

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.

Apparatus for the production of aluminium

In the calcination of petroleum coke or the like in a rotary kiln, utilizing controlled air supply intermediate the ends of the kiln to burn removed volatiles and thereby generate all or nearly all of the heat required, highly effective control procedure includes establishing and repeatedly re-establishing target values for temperatures of exit gas and discharging product respectively at opposite ends of the kiln, such target temperatures representing conditions of desired position of the calcining zone and desired physical character of the calcined product which is achieved by proper maximum temperature in said zone. The procedure further includes adjusting one or more of the variables of combustion air supply, RPM of the kiln, and green coke feed rate so as to keep the end temperatures at target value. Preferably, only two variables are controlled in order to follow the updated target values, and the procedure also includes adjustment of one or both of such selected variables in order to compensate, when necessary, for changes in the other variable. Efficiency, economy, and unusual facility and reliability of control are achieved.

Calcination of coke

A pyroscrubber for combustion of large carbon particles in a stream of waste gas, particularly the waste gas from a coke calcination furnace comprises a generally U-shaped combustion chamber having a first passage arranged parallel with (preferably above) a second passage, so that there is a reversal in gas flow direction between the two passages. The combustion chamber has an exhaust gas inlet and an array of air inlets at the inlet end of the first passage. A gas outlet preferably leads laterally out of the side of the structure at the outlet end of the second passage to secure an abrupt change in the direction of gas flow.

Pyroscrubber

In the calcination of petroleum coke in a rotary kiln, procedure wherein air is controllably supplied internally of the kiln to burn the removed volatiles, as by selection or adjustment of the amount of such air and of the speed of coke travel down the kiln, so that all or nearly all of the heat for calcining the coke is provided by such combustion, and so that a suitably high temperature is reached for effective calcination at an efficiently large feed rate of coke, a special feature being to maintain a significantly long travel time of the coke from a region of intense calcining activity to the product discharge end of the kiln. High production rates, of coke calcined well and uniformly, are economically attained, with ease of control and with unusual stability of kiln operation.

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Arvida, Canada

Raman Radha Sood