Mass transfer between liquid metals and injected gases

Abstract

The rate of liquid-phase mass transfer between submerged bottom-blown and submerged top-blown gas jets and liquid metals was investigated. The rates of oxygen absorption in liquid silver, deoxidation of silver by argon, and deoxidation of liquid copper by CO gas jets were measured. The orifice diameters ranged from 0·46 to 2·2 mm and the flowrates from 1·75 to 45 cm³s⁻¹ at STP or 7·5 to 192 cm³s⁻¹ at the temperature of the melt. The oxygen contents were measured with a galvanic cell with a solid-oxide electrolyte. As support work, a few measurements of the frequency of bubbles formed at submerged orifices in liquid silver and copper were also made. The rates were controlled by liquid-phase mass transfer for the absorption of oxygen into silver at oxygen contents greater than 0·25 wt-% and for the deoxidation of copper at oxygen contents less than 0·025%. At oxygen contents greater than 0·025% in copper and less than 0·25% in silver the rates were fast and essentially controlled by the rate of gas injection. The rate of mass transfer increased with gas flowrate and depth of jet submersion. The mass-transfer parameters were nearly the same for both metallic systems. At low flows in the single':'bubble region the measured mass-transfer coefficients were in good agreement with those calculated from theory. In all cases of bottom-blown argon jets used for the deoxidation of silver, gas–metal equilibrium was obtained and the maximum rate of removal was achieved. A discussion of the results relative to steelmaking reactions and processes is given.