Multiphysics Modelling of Oxygen Injection Lance Steel Making

The basic oxygen steelmaking process is the primary method of steelmaking, in which a carbon rich molten pig iron is converted to steel. A water-cooled copper lance is lowered into an oxygen converter. Pure oxygen is pumped into the converter through the lance. A converging-diverging nozzle accelerates the oxygen jet to speeds exceeding Mach 2. The oxygen oxidises the carbon in the iron into carbon monoxide and carbon dioxide gases, which escape at the top of the vessel. The highly exothermic oxidation reactions that occur are known to cause rapid heating, typically raising temperatures to the vicinity of 2000°C, at least for a short period. Commonly, the nozzle regions of the water-cooled copper lance become degraded after about 300 melts, due mainly to erosive damage from debris and from the slurry itself. Replacing these nozzles incurs considerable cost and disruption to production. There is therefore a natural desire to extend component lifetime as much as possible and further information about the conditions to which these lances are subjected during steelmaking can assist with this. 

We built a fully coupled, multiphase flow, heat transfer model to capture some of the highly complex processes occuring during the steelmaking process.

Thermo-mechanical simulations demonstrated that the copper surfaces did not become excessively hot, but the mechanical properties (including resistance to plastic deformation and abrasive damage) were relatively poor. Some further calculations suggested that a Cu-Be alloy and/or the introduction of a protective cermet coating were options worth exploring further.