Abstract
Deoxidation rate of liquid copper whose oxygen concentration was above 0.25 mass% was measured by employing an agitated reactor under various experimental conditions (reaction temperature=1357∼1538 K, impeller tip speed=1∼33.3 s−1, gas flow rate=2.2∼31.7 (10−6 m3(NTP)/s), mol fraction of CO in the gas phase=0.2∼1.0).
Results obtained are as follows:
(1) The resistance of mass transfer in the liquid phase is small and neglected with respect to the overall resistance of the deoxidation.
(2) The chemical reaction is the rate-controlling step at a high gas flow rate, and the rate (−r) is expressed by an equation, −r=k′pCO, where pCO is the partial pressure of CO and k′ is an apparent rate constant of the chemical reaction. The apparent activation energy and the frequency factor are 9830 J/mol and 2.7 (10−6 mol/m2·s·Pa), respectively.
(3) Both steps of mass transfer in the gas phase and the chemical reaction are rate-controlling at a low gas flow rate. An empirical correlation on mass-transfer coefficient (kG) obtained by substracting the resistance of chemical reaction from that of the over-all reaction is Sh=0.01Re2.0Sc0.5 (Sh=kGd⁄D, Re=duρ⁄μ, Sc=μ⁄ρD, d=equivalent diameter, u=gas velocity in the nozzle, ρ=density of gas, μ=viscosity of gas, and D=diffusion coefficient of the CO2-CO system).
(4) The rate of deoxidation under the experimental conditions can be estimated from the over-all rate equation and empirical equations for k′ and kG.
(5) It was pointed out that the experiments under the conditions of lower oxygen concentration and higher temperature than those of the present study are necessary to discuss the mechanism of chemical reaction.
