Deoxidatlon rate of copper droplet levitated in Ar-H₂ gas stream

Abstract

Levitated copper droplets, 5 mm in diameter with initial oxygen contents of 0.036 to 1.9 wt pct, were deoxidized at about 1970 K in an Ar-H₂ gas stream. The Ar-H₂ gas mixture having hydrogen partial pressure less than 4 kPa was introduced into a silica reaction tube of 11-mm ID at gas flow rates up to 2 x 10^-4 Nm³s^-1. The effects of initial oxygen content of the droplets, hydrogen partial pressure, and gas flow rate on the deoxidation process were examined. A mixed control model for the deoxidation rate involving both gas and liquid film mass-transfer resistances was combined with a thermodynamic relationship for the dissolved species in molten copper. The value of 2 × 10^-4 m 73x00D7; s^-1 was assigned to the liquid film mass-transfer coefficient of dissolved oxygen throughout all experimental conditions. Under the experimental conditions of low initial oxygen content and high hydrogen partial pressure, the liquid film mass-transfer resistance was significant. When a droplet of high initial oxygen content was deoxidized, transition phenomena from gas to liquid film mass-transfer control were noticed in the later stage of reaction. It was deduced from the present model that the accumulation of dissolved hydrogen was indispensable to these phenomena.