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Ferrothermic Extraction of Copper.
Khalafalla SE; Haas LA; Kilau HW
U S Pat 3 622 304 1971 Nov; :
Metallic copper is produced from finely ground oxide copper ores or concentrates by intimately mixing them with finely divided iron in the form of powder or shredded cans, auto bodies, or other scrap in a ratio up to 2x the theoretical amount for reduction of the oxide, and heating, preferably with some movement such as in a rotary kiln, for several hours at 560 deg.-950 Deg. C in a nonoxidizing atmosphere such as he or n2. The fe becomes oxidized to feo, while cu oxides are reduced to metal, the completeness of the reaction depending on the particle size of the reactants. With ore and fe finer than 100 mesh, 98 pct completion was accomplished, compared with 40-90 pct with coarser scrap fe. The reaction products are separated from gangue by specific gravity on jigs, air-tables, etc., and excess fe is separated from cu magnetically for recycle, leaving pure cu metal. Presumably, the feo is rejected with the gangue, but if the molar ratio of reactants is 8cu:3fe, the reduction of cu2o should give fe3o4, which could be separated magnetically from cu. However, in several experiments a static atmosphere gave better cu recovery than flowing he, the reason being unexplained. Water can be tolerated in the atmosphere up to 10 pct, 0.3-3 pct being desirable, but co2 is undesirable and carbonate ores as well as sulfide ores should be preroasted.
U.S. Pat. 3,622,304; Nov. 23, 1971; Chem. Abstr. 76:48,578R
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