Patent NZ-507157-A (NZ)
Title: A molten metal bath-based direct smelting process with a gas flow rate of at least 0.30 Nm3/s/m2 at the interface of the metal and slag layers
Inventor: BATTERHAM ROBIN JOHN
IPC: C21B11/08
Filed: 2000-09-26
Abstract: A direct smelting process for producing metal from a metalliferous feed material in a fixed metallurgical vessel comprises the steps: a) forming a molten bath having a metal layer (15) and a slag layer (16) on the metal layer in the vessel; b) injecting metalliferous feed material and/or solid carbonaceous material with a carrier gas into the molten bath via one or more downwardly extending lance/tuyere, and smelting metalliferous material to metal in the molten bath, whereby the solids and gas injection causes gas flow from the molten bath at a flow rate of at least 0.30 Nm3/s/m2 at the location of the interface between the metal layer and the slag layer (under quiescent conditions), which gas flow entrains molten material in the molten bath and carries molten material upwardly as splashes, droplets and streams and forms a transition zone (23) in a gas continuous space (25) in the vessel above the slag layer, whereby splashes, droplets and streams of molten material contact the side walls of the vessel and form a protective layer of slag; and c) injecting an oxygen-containing gas into the vessel via one or more lance/tuyere and post-combusting reaction gases released from the molten bath, whereby ascending and thereafter descending splashes, droplets and streams of molten material facilitate heat transfer to the molten bath, and whereby the transition zone minimizes radiation heat loss from the vessel via the side walls in contact with the transition zone. A fixed vessel for use in the direct smelting process comprises: a) a shell; b) a hearth formed of refractory material having a base (3) and sides (55) in contact with the molten bath; c) side walls (5) which extend upwardly from the sides of the hearth and are in contact with the slag layer (16) and the gas continuous space(25), wherein the side walls that contact the gas continuous space include water cooled panels (8) and a layer of slag on the panels; d) one or more lance/tuyere (13) extending downwardly into the vessel and injecting an oxygen-containing gas into the vessel above the metal layer (15); e) one or more downwardly and inwardly extending lance/tuyere (11) injecting at least part of the metalliferous feed material and/or a carbonaceous material with a carrier gas into the molten bath so as to generate bath-derived gas flow at a rate of at least 0.30 Nm3/s/m2 at the location of the interface between the metal layer (15) and the slag layer (16) (under quiescent conditions (17 and 19)) and resultant buoyancy uplift of molten material from the metal layer (15) and the slag layer (16); f) a transition zone (23) formed by ascending and thereafter descending splashes, droplets and streams of molten material in the gas continuous space (25) above the slag layer with some of these splashes, droplets and streams contacting the side walls of the vessel and forming a layer of molten material on the side walls; and g) a means for tapping molten metal (81) and slag (61) from the vessel.