Direct bath smelting process with management of peripheral cold zones at the metal-slag interface

Abstract

An improved direct smelting vessel comprising a smelt reduction vessel (SRV) and optionally a cyclone converter furnace (CCF). The SRV provides means for promoting metal mixing at a zone below a slag layer adjacent to a vessel wall of the direct smelting vessel. The means for promoting metal mixing may include a split-level refractory hearth with two refractory floor levels, a refractory hearth with one or more gas bubbling devices, and/or at least one pair of solids injection lances that provide alternating solids injection at any given time (or other means). The means for promoting the metal mixing reduces a stagnant region capable of supporting a semi-solid slag layer that restricts metal-slag heat transfer. The means for promoting the metal mixing maintains an effective temperature delta between tapped metal at a forehearth and metal at the vessel wall of no greater than 40° C.

What is claimed is: 
     
         1 . A method for direct smelting of metalliferous material and producing molten metal in a direct smelting vessel, the method comprising:
 injecting solid carbonaceous material through at least one injection lance extending into the direct smelting vessel such that solids penetrate at least partially into a molten metal layer in the direct smelting vessel, wherein a slag layer is floating on the molten metal layer; and   promoting metal mixing at a zone immediately below the slag layer adjacent to a vessel wall of the direct smelting vessel.   
     
     
         2 . The method of  claim 1 , wherein the metal mixing reduces a volume occupied by a stagnant region cold enough to be capable of supporting a semi-solid slag layer that restricts metal-slag heat transfer. 
     
     
         3 . The method of  claim 1 , wherein the metal mixing maintains an effective temperature delta between tapped metal at a forehearth and metal at the vessel wall of no greater than 40° C. 
     
     
         4 . The method of  claim 1 , wherein the metal mixing is promoted using the direct smelting vessel comprising:
 a split-level refractory floor with two refractory floor levels comprising a first level having a first depth that supports a first metal depth and a second level having a second depth that supports a second metal depth;   wherein the second metal depth is greater than the first metal depth; and   wherein the first depth that supports the first metal depth promotes the metal mixing by metal convection into and out of the zone below the slag layer adjacent to the vessel wall.   
     
     
         5 . The method of  claim 4 , wherein the first level comprises at least 70% of a cross-sectional area of the split-level refractory floor. 
     
     
         6 . The method of  claim 4 , wherein the first depth supports the first metal depth that is not greater than 900 mm. 
     
     
         7 . The method of  claim 4 , wherein the first depth supports the first metal depth that is not greater than 700 mm. 
     
     
         8 . The method of  claim 4 , wherein the first depth supports the first metal depth that is not greater than 600 mm. 
     
     
         9 . The method of  claim 4 , wherein the second depth supports the second metal depth that is at least 300 mm greater than the first metal depth. 
     
     
         10 . The method of  claim 1 , wherein the metal mixing is promoted by injecting gas in the direct smelting vessel using one or more gas bubbling devices for promotion of metal convection to the zone below the slag layer adjacent to the vessel wall. 
     
     
         11 . The method of  claim 10 , wherein the gas comprises argon gas or nitrogen gas. 
     
     
         12 . The method of  claim 1 , wherein the metal mixing is promoted by using one or more pairs of solids injection lances in the direct smelting vessel, wherein one branch of a pair of solids injection lances provides at least a majority of the injected feed solids for the pair of solids injection lances at any given time. 
     
     
         13 . The method of  claim 12 , wherein injection of the feed solids through the one branch of the pair of solids injection lances is reversed to an opposing branch of the pair of solids injection lances, either immediately following injection through the one branch or a period of time later. 
     
     
         14 . An apparatus for direct smelting metalliferous material and producing molten metal and molten slag, the apparatus comprising:
 a direct smelting vessel comprising at least one of:
 (a) a split-level refractory hearth with two refractory floor levels comprising:
 a first level having a first depth that supports a first metal depth; and 
 a second level having a second depth that support a second metal depth, wherein the second metal depth is greater than the first metal depth; 
 
 (b) a refractory hearth with one or more gas bubbling devices; or 
 (c) one or more pairs of solids injection lances, wherein one branch of a pair of solids injection lances provides at least a majority of the injected feed solids for the pair of solids injection lances at any given time; 
   wherein the split-level refractory hearth, the one or more gas bubbling devices, or the one or more pairs of solids injection lances promotes metal mixing at a zone below a slag layer adjacent to a vessel wall of the direct smelting vessel.   
     
     
         15 . The apparatus of  claim 14 , wherein the metal mixing reduces a stagnant region capable of supporting a semi-solid slag layer that restricts metal-slag heat transfer between the molten metal and the molten slag. 
     
     
         16 . The apparatus of  claim 14 , wherein the metal mixing maintains an effective temperature delta between tapped metal at a forehearth and metal at the vessel wall of no greater than 40° C. 
     
     
         17 . The apparatus of  claim 14 , wherein the direct smelting vessel comprises the split-level refractory hearth. 
     
     
         18 . The apparatus of  claim 17 , wherein the first level comprises at least 70% of the cross-sectional area of the refractory floor, wherein the first depth supports the first metal depth that is not greater than 900 mm, and wherein the second depth supports the second metal depth that is at least 300 mm greater than the first metal depth. 
     
     
         19 . The apparatus of  claim 14 , wherein the direct smelting vessel comprises the refractory hearth with the one or more gas bubbling devices. 
     
     
         20 . The apparatus of  claim 14 , wherein the direct smelting vessel comprises the one or more pairs of solids injection lances.