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 the nozzle and a 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 at least one ejector comprises primary gas outlets and a plurality of secondary gas outlets adjacent each of the primary gas outlets, 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 and mixtures thereof. 
   
   
       6 . The method according to  claim 1 , wherein the gas supplied to the at least one ejector and the annular gas passage is independently selected from the group consisting of oxygen, argon, nitrogen and mixtures thereof. 
   
   
       7 . The method according to  claim 2 , wherein the gas is selected from the group consisting of oxygen, argon, nitrogen and mixtures thereof. 
   
   
       8 . The method according to  claim 2 , wherein the gas supplied to the at least one ejector, the annular gas passage and the plurality of secondary gas outlets is independently selected from the group consisting of oxygen, argon, nitrogen and mixtures thereof. 
   
   
       9 . The method according to  claim 2 , wherein the shrouding gas protects critical dimensions of the nozzle from damage. 
   
   
       10 - 20 . (canceled)