Many kinds of refining processes are used in the steelmaking industry. Molten metal contained in the bath of the processes is strongly agitated by gas injection. Meal droplets are carried up into the upper molten slag layer due to the gas-lift effect. Each metal droplet falls and finally returns to the lower metal layer although it is captured for a while at the metal-slag interface due to the interfacial effect. The behavior of molten metals near the interface is closely associated with the refining efficiency and metal loss. The residence time at the interface was investigated in this study. An analytical equation was derived for the residence time and a water model study was carried out to validate the equation. Water and silicone oil were used for the models of molten metal and slag, respectively.
