Reynolds Metals Company

Other

Robert M Kibby

Method and apparatus for reducing the quantity of carbon dioxide emitted to the atmosphere from carbothermic processes producing metals are described. The method involves rejecting carbon from the process system or using carbon as a reagent to be recycled within the boundaries of the process system as a result of reactions of hydrogen with the carbon monoxide produced by the carbothermic process. Examples of the application of the method are given for the production of aluminum and for the production of a portion of the iron content of steel.

Carbothermic reduction product gas treatment

A method for extracting aluminum of substantial purity from furnace products resulting from carbothermic reduction of alumina-bearing ores and contaminated with up to about 30 weight percent of aluminum carbide is disclosed. The method involves contacting the furnace product with a high alumina-containing molten slag in the substantial absence of reactive carbon, so as to cause the alumina-containing slag to react with the aluminum carbide, thereby diminishing the aluminum carbide content of the furnace product to the level of 4-10% aluminum carbide by weight. It further involves heating the partially purified furnace product in the absence of both reactive carbon and slag, thereby reacting the self-contained alumina with the aluminum carbide contaminant to produce a purified aluminum.

Aluminum purification system

Alumina is carbothermically and cyclically reacted with carbon and recycled materials within a reduction zone to produce a slag layer, an overlying aluminum metal layer, and vaporization products which are passed through a vapor-permeable back-reaction zone, which comprises a feed charge mixture which is selectively connected to the reduction zone. The aluminum metal layer is initially contaminated with 20-37% of Al.sub.4 C.sub.3 by weight. The vaporization products preheat and react with the feed charge mixture within the back-reaction zone to produce pre-reduction products which are selectively co-fed to the reduction zone with any unreacted portions of the feed charge mixture. The liquid/solids ratio in the back-reaction zone is limited, thereby maintaining the zone in vapor-permeable and non-slumping condition, by varying proportions of alumina fed to the back-reaction zone and to the reduction zone. The aluminum in the aluminum metal layer is selectively purified by feeding no additional carbon and by raising the reaction temperature until substantially all aluminum carbide is decomposed.

Minimum-energy process for carbothermic reduction of alumina

A carbothermic reduction process is described for producing alumina metal containing about 10% Al.sub.4 C.sub.3. The process heats a descending charge by radiation at a rate of heat flux of 10-100 KW/sq. inch, to form a melt surface that is spaced from an open arc between a pair of electrodes. Additional alumina beyond the stoichiometric amount is preferably introduced into the reduction zone immediately surrounding the melt surface. A large moving-bed shaft furnace is utilized. This furnace comprises hearth shoulders and preferably also comprises alumina introduction ports and a charge shaping device that cooperatively interacts with the hearth shoulders to suspend the descending charge column above a pool of melted aluminum product therebeneath, whereby the aluminum product is able to flow and/or fall into the pool with minimum passage over unreacted charge.

Carbothermic reduction furnace

A method for extracting aluminum of substantial purity from furnace products resulting from carbothermic reduction of alumina-bearing ores and contaminated with up to about 30 weight percent of aluminum carbide is disclosed. The method involves contacting the furnace product with a high alumina-containing molten slag in the substantial absence of reactive carbon, so as to cause the alumina-containing slag to react with the aluminum carbide, thereby diminishing the aluminum carbide content of the furnace product.

Magnesium metal is produced in a magnesium reduction furnace by the reaction of aluminum metal with a calcium magnesium aluminate slag or with magnesium oxide in the presence of such slag, wherein aluminum is fed to the magnesium reduction furnace as an aluminum silicon alloy and wherein magnesium oxide is fed in less than stoichiometric amounts so that not all of the aluminum is reduced, such additions producing magnesium vapor and two liquid layers: an aluminum silicon alloy having a reduced aluminum content and a MgO.CaO.Al.sub.2 O.sub.3.TiO.sub.2 slag. The aluminum silicon alloy layer is tapped and recovered from the furnace. The recovered alloy may be used in the production of silicon alloy product by addition to aluminum.

Magnesium production

A carbothermic process for the production of aluminum contaminated with no more than about 10 weight percent of aluminum carbide is disclosed which involves charging alumina values and carbon values into a furnace and subjecting only a minor portion of said charge at any given time of an open arc so as to heat the reagents to reaction temperture. The various vapors which form pass through the charge where they undergo additional reaction. The aluminum formed flows over the charge which is maintained at a temperature lower than reaction temperature, so as to obtain aluminum contaminated with no more than about 10 weight percent of aluminum carbide.

Carbothermic reduction process

A process is set forth for reducing the aluminum carbide content of aluminum produced via carbothermic processes which comprises contacting the aluminum contaminated with aluminum carbide with reactive gases so as to cause the aluminum carbide to react and separate from the aluminum. The aluminum is recovered and the residue can be recycled back to the furnace without additional chemical treatment.

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Richmond, VA, United States of America

Robert M Kibby