Process for producing pure iron powder and product thereof

摘要

1,137,525. Iron powder; iron oxide. CENTRO SPERIMENTALE METALLURGICO S.p.A. 23 June, 1966 [23 June, 1965], No. 28156/66. Heading C1A. Crystalline, heptahydrated iron sulphate is dried, and its grain size increased, in a fluidized bed reactor, dehydrated and dissociated by heating whilst maintaining the grain size, and then heated in a fluidized bed reactor to 900 to 1200‹ C. prior to reduction, preferably also in a fluidized bed reactor, with reducing gases at 800 to 1200‹ C. In a modification the reduction is carried out by using a solid reducing material, such as carbon black, charcoal, graphite, or mineral oil coke, instead of the reducing gas. The grain size may be increased to 0À2 to 1À0 mm. by drying at 60 to 100‹ C. and almost pure hematite is obtained after dehydrating at 200-300‹ C. and dissociating at about 800‹ C. in a fluidized bed reactor. The iron powder produced by reduction may be heated to 1000 to 1100‹ C. for 10 to 30 minutes in an inert or reducing atmosphere to reduce its pyrophoricity and may be subsequently subjected to crushing and screening operations. The reducing gas may travel countercurrent to the ferrous compounds in which case it is heated to the temperature required for the reduction by heat exchange with the hot iron powder and the iron oxide is heated to the temperature required for the reduction by combustion of the spent reducing gas. The spent reducing gas may however be collected after the reduction stage and enriched to make it reducing and recycled. The iron sulphate may be suitably obtained by crystallization of exhausted pickling baths for steel sheets.