DIRECT IRON AND STEELMAKING

摘要

Solid state iron oxide reduction in a gas-solid reduction zone is combined with continuous melting of the hot solid reduced iron in a fuel-fired gas-solid-liquid melting zone within a rotary furnace. The process includes direct pneumatic transfer of the hot reduced iron by carrier gases through a transfer duct incorporating an injection lance nozzle projecting a jet of hot reduced iron downwards into the metal bath within the melting zone. Oxygen is also introduced into the hot gas stream at selected locations in the melting zone for post-combustion with carbon monoxide generated by a carbon boil and combustion with other combustible gases prior to exit from the rotary furnace, thereby furnishing heat for melting. The hot gas stream is then utilized to provide a significant part of the heat requirement for reduction, prior to exhausting into the atmosphere. A feature is distributing the hot solid reduced iron laterally and longitudinally within the melting zone to enhance heat transfer for melting, including a preferred embodiment comprising continually traversing the jet of carrier gases and hot reduced iron longitudinally forwards and backwards. The invention embraces a broad range of known solid-state reduction processes, classified either as: Group A) those employing gases within a gravity contact-supported or fluidized moving bed at substantial pressures of 1-5 atmospheres; or Group B) solid carbonaceous reductants in a rotary kiln or rotary hearth conducted at near ambient atmospheric pressure. Combustibles in the exhaust gases and unnecessary fume generation caused by direct injection of oxygen into the bath are avoided, as problem endemic to known electric-arc and converter steelmaking technologies. A preferred embodiment applied to Group A reduction includes in situ reforming of a major portion of the hydrocarbons applied as reducing gases in the reduction zone, in combination with reforming a minor portion by partial oxidation with oxygen. The process includes various other preferred features which significantly improve energy requirements, production rates, yields, costs and control of the liquid iron and steel product composition and quality in relation to the prior art.