Importance

Loading Importance Indicators...

Abstract

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.

Loading the Abstract Image...

First Claim