Gas lance system for molten metal furnace

Abstract

A lance system for lancing gas into a molten metal furnace wherein primary gas is passed into a furnace as a coherent jet enveloped in secondary gas provided into the furnace through a plurality of secondary openings communicating with respective secondary passages having restrictions within the lance set back from the lance face.

1 . A lance comprising a lance face having at least one primary opening for passing at least one gas jet out from the lance, and a plurality of secondary openings arranged around the primary opening(s) on the lance face, each secondary opening communicating with a passage for passing secondary gas within the lance to the respective secondary opening, and each said passage having a restriction therein so that the area for gas flow at the restriction is smaller than the area of the secondary opening with which that passage communicates.  
     
     
         2 . The lance of  claim 1  wherein the area for gas flow at the restriction is within the range of from 20 to 80 percent of the area of the secondary opening.  
     
     
         3 . The lance of  claim 1  wherein the plurality of secondary openings are arranged in at least one ring around the primary opening(s).  
     
     
         4 . The lance of  claim 1  wherein the plurality of secondary openings are arranged in two rings, an inner ring and an outer ring, around the primary opening(s).  
     
     
         5 . The lance of  claim 4  wherein the passages communicating with the secondary openings arranged on the inner ring communicate with an inner annular passage within the lance, and the passages communicating with the secondary openings arranged on the outer ring communicate with an outer annular passage within the lance.  
     
     
         6 . The lance of  claim 1  wherein the downstream termination of each restriction is a distance of at least 3 ds from the lance face where ds is the diameter of the secondary opening corresponding to that restriction.  
     
     
         7 . A method for providing at least one gas jet from a lance into a molten metal furnace comprising: 
 (A) passing primary gas in at least one primary gas jet out from a lance to form at least one primary gas jet within the molten metal furnace;    (B) passing secondary gas through a plurality of passages within the lance, each passage communicating with a secondary opening and having a restriction therein, and said secondary gas flowing within a passage having a higher pressure at the entrance to the restriction than at the secondary opening; and    (C) passing secondary gas out from the secondary openings and forming a gas envelope around the primary gas jet(s) within the molten metal furnace.    
     
     
         8 . The method of  claim 7  wherein the gas envelope comprises a flame envelope.  
     
     
         9 . The method of  claim 7  employing one primary gas jet.  
     
     
         10 . The method of  claim 7  employing from 2 to 6 primary gas jets.  
     
     
         11 . The method of  claim 7  wherein the primary gas jet(s) comprises oxygen.  
     
     
         12 . The method of  claim 7  wherein the primary gas jet(s) has a supersonic velocity.  
     
     
         13 . The method of  claim 7  wherein the secondary gas pressure at the entrance to the restriction exceeds the secondary gas pressure at the secondary opening by at least 50 percent.