Oxygen injection method

A method of injecting oxygen into melt located within a metallurgical furnace having a heated furnace atmosphere containing carbon monoxide, said method comprising:

• introducing oxygen streams into nozzles having passageways of converging-diverging configuration, said configuration including an inlet section, a throat section, and a deverging section, the nozzles being situated at a tip of awater-cooled lance and angled outwardly from a central axis of the water-cooled lance;
• injecting a fuel containing a hydrogen species into the oxygen streams at inner circumferential locations of the passageways that are situated entirely within the passageways so that combined fuel and oxygen containing streams are formed within the passageways, each having a structure composed of an outer circumferential region containing a mixture of the oxygen and the fuel and an inner central region surrounded by the outer circumferential region and containing the oxygen and essentially no fuel;
• the oxygen streams being introduced into inlet sections of the passageways at or above a critical pressure, thereby to produce:
• a choked flow condition within the central throat sections of the passageways;
• acceleration of the combined fuel and oxygen containing stream to a supersonic velocity within diverging sections of the passageways;
• and discharge of the combined fuel and oxygen containing streams as structured jets from the nozzles into the furnace atmosphere, the structured jets having the structure of the combined fuel and oxygen containing streams and the supersonic velocity upon discharge from the nozzle;
• preventing ignition and combustion of the fuel within the passageways by providing the passageways with an inner surface uninterrupted by any discontinuity within which the outer circumferential region could otherwise decelerate and provide a site for stable combustion of the fuel;
• producing flame envelopes surrounding individual jets of oxygen formed from the inner central region of the structured jets and initially having the supersonic velocity to inhibit velocity decay and concentration decay of the jets of oxygen, the flame envelopes being produced entirely outside of the nozzles through contact of the outer circumferential region of the structured jets with the heated furnace atmosphere so as to create a shear-mixing zone containing a flammable mixture composed of the fuel, the oxygen and the heated furnace atmosphere and auto-ignition of the flammable mixture through heat supplied by the heated furnace atmosphere;
• and
• situating the water-cooled lance within the metallurgical vessel and directing the jets of oxygen into the melt, while surrounded by the flame envelopes.