Effect of Supersonic Oxygen Lance on Post-Combustion in Converter Steelmaking Process – Experiment and Analysis with Converter Simulator

Employing post-combustion technology in the converter, using the sensible heat of the hot metal and the oxidation reaction heat as a heat source, is known to compensate for insufficient heat in the converter process. However, most studies on post-combustion have been conducted using subsonic nozzles, whereas actual converter processes use supersonic nozzles. Therefore, research on the combustion behavior of supersonic jets is needed. In this study, experiments and analyses were conducted using a converter simulator and a supersonic nozzle to investigate the effect of nozzle height on the post-combustion behavior. The reaction was set to complete combustion, with an O2gas flow rate of 150 L/min blown through the upper lance and a CO gas flow rate of 300 L/min blown at the bottom of the simulator to represent the surface of the molten metal. The combustion reaction of CO gas was calculated to be rate-controlled by reactant mixing. The nozzle heights were set to 250, 380, and 530 mm from the surface of the molten metal. Post-combustion analysis showed that the lowest gas velocity was observed under the condition of the highest nozzle height of 530 mm, and the high temperature and reaction zones were widely distributed in the lower region. Therefore, to facilitate heat compensation to the molten metal, it is necessary to control the gas velocity of the molten steelgas interface slowly.