Armco Inc.

David M Kundrat

Richard C Sussman

Allan M Smillie

A multiple stage process for obtaining Ni units from Ni laterite ores and sulfur-bearing Ni concentrates during production of nickel-alloyed iron, nickel-alloyed steel or nickel-alloyed stainless steel in a reactor equipped with top- and bottom-blowing means. Dried Ni laterite ore is charged into an iron/slag bath mixture containing dissolved carbon and a metalloid reductant such as aluminum or silicon. The laterite ore is melted while heat is generated by oxidation of the metalloid and carbon in the reactor. After the laterite ore is melted, top-blowing of pure oxygen and bottom-blowing of an oxygen-containing gas are ceased. Bottom injection of an inert stirring gas is begun. A sulfur-bearing Ni concentrate and aluminum are added to the bath. Sulfur from the sulfur-bearing Ni concentrate is transferred to and held within the slag produced from the laterite ore by controlling slag composition and temperature, degree of mixing of the iron/slag bath mixture by the inert gas and the carbon/metalloid concentration in the bath mixture. The sulfur-containing slag then is discharged from the reactor and the iron bath mixture is decarburized and refined to alloy specification. The extent of desulfurization by the slag determines the amount of sulfur-bearing Ni concentrate that can be added to the bath for a given slag weight. Total slag weight throughout the process should be within the range of 200 to 300 kg slag/MT bath mixture, the temperature of the bath should be maintained between 1500.degree.-1700.degree. C., the slag basicity should be controlled between 1-3 and the compositions of Al.sub.2 O.sub.3 and MgO in the slag should be maintained between 10-25 wt. % and 10-20 wt. % respectively.

Melting of NI laterite in making NI alloyed iron or steel

A three-stage process for obtaining metallic Cr units insitu during the production of stainless steel. Raw chromite ore or a concentrate produced from chromite ore is mixed with a carbonaceous reductant and slagging agents are added to an iron bath (24) for smelting and refining in a refining reactor (10). During the first stage, partially metallized chromite is smelted by carbon in the reactor that is top-and bottom-blown with oxygen and oxygen-containing gases respectively to produce a chromium alloy bath having a carbon content well below saturation. In the second stage, the alloy bath is decarburized by being bottom stirred with the oxygen-containing gas to the final bath carbon specification. In the third stage, the alloy bath is reduced by a metalloid reductant such as silicon or aluminum and again bottom stirred but with a non-oxidizing gas to achieve a high chromium yield. The reactor includes a top lance (18) extending through a throat (14) with a lower portion (20) of the lance extending to a point just above the bath and means (22) such as a tuyere or porous plug mounted at or near a bottom (16) and extending through a refractory lining (12) for stirring the iron bath containing dissolved carbon. Lance (18) includes a central passage (34) for injecting a compact, focused jet oxygen gas (30) that can penetrate through a slag layer (26) for decarburization of the iron bath and an outer passage (32) for discharging an oxygen gas (28) above the bath for post-combustion of CO to CO.sub.2. Passage (32) includes a plurality of evenly spaced annular diverging nozzles (33). The lance also includes a pair of concentric conduits (36) and (38) for conducting a coolant.

Method for direct use of chromite ore in the production of stainless

A process for obtaining Ni units from sulfur-bearing nickel concentrate during refining a nickel-alloyed steel or a stainless steel. Sulfur of the concentrate is transferred to and held within the slag by controlling slag composition and temperature, degree of mixing of the slag with the bath by an inert gas and aluminum level in the bath. The extent of desulfurization by the slag, the slag weight and the steel sulfur specification determine the amount of concentrate that can be added to the bath. The ratio of the slag weight to the iron bath weight should be in the range of 0.10-0.30 and the bath temperature is maintained between 1550.degree.-1700.degree. C. The slag basicity is controlled between 1.0 and 3.5, the composition of Al.sub.2 O.sub.3 in the slag is maintained between 15-25 wt. % and the composition of MgO is maintained between 12-20 wt. %.

Direct use of sulfur-bearing nickel concentrate in making Ni alloyed

Method of reducing metal oxide in a rotary hearth furnace (14) to make a feed stock for a refining vessel when manufacturing alloyed iron, alloyed steel or stainless steel. The rotary hearth furnace includes an annular inner refractory wall (32), an annular outer refractory wall (34), an annular refractory platform (33) between the two walls. Stationary fuel burners (36, 40) are mounted to walls (32, 34) at a position just above an upper surface of the platform. A mixture of a metal oxide and a carbonaceous reductant is placed onto the upper surface of the platform and rotated past the burners. The oxide is heated by an oxidizing flame. Thereafter, a second layer of a reductant is charged over the hot first layer, and both layers are heated for an additional period of time to a temperature of at least 1300.degree. C. to reduce the metal oxide. The metal oxide may be chromium ore, chromium ore concentrate, nickel ore, nickel ore concentrate and stainless steel flue dust. The reductant may be coal or coke. The reduced metals provide inexpensive metal units for alloying with molten iron.

Method of reducing metal oxide in a rotary hearth furnace heated by an

Method of producing pig iron in a blast furnace. At least a portion of a top gas from a blast furnace is collected, dried and then heated to an elevated temperature preferably in the range of 900.degree.-1000.degree. C. An oxygen-enriched hydrogenaceous fuel is introduced into the furnace bosh and the heated dried top gas is introduced into the lower half of the furnace stack above the furnace bosh at a point above which the coke in the furnace is not reactive.

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Cincinnati, OH, United States of America

David M Kundrat