A post combustion (P·C) nozzle which accomplishes high P·C and heat transfer efficiency in a converter was developed through studies of both nozzle profile for maintaining stable P·C and appropriate P·C regin. By applying the abrupt expansion P·C nozzle to the 180t LD-KGC converters of Kawasaki Steel Corp., the following results were obtained.
1) In order to enhance heat transfer to molten steel, it is desirable to form the P·C region in a space near the molten steel surface and approximately more than 1.0 m inside the furnace wall refractories.
2) It is estimated that the P·C nozzle forms diffusion combustion due to the collision between oxygen jet and carbon monoxide gas. Therefore the oxygen flow velocity into the combustion region should be controlled under 10 m/s. For this purpose, it is required to keep the initial jet velocity from the nozzle within 100 m/s.
3) The P·C ratio increases with the lance height but the heat transfer ratio is almost constant at 60% regardless of the lance height.
4) The scrap ratio increased by 6% when P·C oxygen of 0.5 Nm3/min·t is supplied.
5) The developed abrupt expansion P·C nozzle has no significant effects on metallurgical reactions, and the values of (T-Fe) and (P)/ [P] are almost the same as those in the conventional process.
