Metallurgical lance with annular gas flow control

Abstract

A method of controlling total jet pressure from the head of a metallurgical lance for introducing gas into a volume of metal in a vessel. The lance head has at least one ejector, which has a nozzle located in a bore of the lance head and has an annular gas passage between at least one nozzle and the wall of the bore. The method proceeds by adjusting the annular gas velocity from a first Mach number to a second mach number to effect change of the total jet pressure.

1 . A method of controlling total jet pressure from a head of a metallurgical lance for introducing gas into a volume of metal in a vessel, the lance head having at least one ejector comprising a nozzle located in a bore of the lance head and having an annular gas passage between at least one nozzle and the wall of the bore, the method comprising adjusting the annular gas velocity from a first Mach number to a second Mach number to effect change of the total jet pressure.  
   
   
       2 . The method according to  claim 1 , wherein the ejector outlets comprises primary gas outlets and a plurality of secondary gas outlets adjacent each primary gas outlet, and supplies shrouding gas to the secondary gas outlets.  
   
   
       3 . The method according to  claim 1 , wherein the annular gas velocity is changed from a value of about Mach 1.  
   
   
       4 . The method according to  claim 1 , wherein the annular gas velocity is changed to a value of about Mach 1.  
   
   
       5 . The method according to  claim 1 , wherein the gas is selected from the group consisting of oxygen, argon, nitrogen or mixtures thereof  
   
   
       6 . The method according to  claim 1 , wherein the gas supplied to the ejector and the annular passage are independently selected from the group consisting of oxygen, argon, nitrogen or mixtures thereof.  
   
   
       7 . The method according to  claim 2 , wherein the gas is selected from the group consisting of oxygen, argon, nitrogen or mixtures thereof.  
   
   
       8 . The method according to  claim 2 , wherein the gas supplied to the ejector, the annular passage and the secondary outlets are independently selected from the group consisting of oxygen, argon, nitrogen or mixtures thereof.  
   
   
       9 . The method according to  claim 2 , wherein the shrouding gas protects the critical dimensions of the convergent nozzle from damage.  
   
   
       10 . A metallurgical lance head for introducing gas into a volume of metal in a vessel, the head having at least one ejector comprising a nozzle located in a bore of the head and having an annular gas passageway between the ejector and a wall of the bore, the wall curving inwards at an intermediate region before a discharge end of the ejector, and the wall near the intermediate region providing a convergent distal end portion of a secondary gas passageway.  
   
   
       11 . The lance head of  claim 10 , wherein the ejector outlet comprises a primary gas outlet.  
   
   
       12 . The lance head of  claim 11 , wherein the primary gas outlet discharges a gas selected from the group consisting of oxygen, argon, nitrogen or mixtures thereof.  
   
   
       13 . The lance head of  claim 11 , wherein the secondary gas passageway carries a shrouding gas.  
   
   
       14 . A metallurgical lance head for introducing gas into a volume of metal in a vessel, the head having at least one ejector comprising a nozzle located in a bore of the head and having an annular gas passageway between the ejector and a wall of the bore, the wall curving inwards at an intermediate region before a discharge end of the ejector, and the wall near the intermediate region providing a convergent distal end portion of a secondary gas passageway, 
 the head further having a plurality of secondary gas outlets separated from and surrounding a primary gas outlet, the secondary gas outlet directed at an angle away from the annular gas outlet effective to form a gaseous layer around a gas discharged from the primary gas outlet.    
   
   
       15 . The lance head of  claim 14  wherein the longitudinal axis of the secondary gas outlet diverges from the longitudinal axis of the primary gas outlet at an angle of up to about 45°.  
   
   
       16 . The lance head of  claim 14  wherein the longitudinal axis of the secondary gas outlet diverges from the longitudinal axis of the primary gas outlet at an angle of from about 5° to about 25°.  
   
   
       17 . The lance head of  claim 14  wherein the longitudinal axis of the secondary gas outlet diverges from the longitudinal axis of the primary gas outlet at an angle of from about 10° to about 20°.  
   
   
       18 . The lance head of  claim 14  wherein the secondary gas outlet discharges a shrouding gas.  
   
   
       19 . The lance head of  claim 14  wherein the primary gas outlet discharges a gas selected from the group consisting of oxygen, argon, nitrogen or mixtures thereof.  
   
   
       20 . The lance head of  claim 14  wherein the plurality of secondary gas outlets is arranged circumferentally or on an arc of a circle that is concentric with the primary gas outlet.