Kinetics of Liquid Copper Reduction with Graphite

Abstract

The rate of copper reduction using graphite rods vertically has been studied using a continuous infrared gas analyzer technique to determine the content of oxygen removed from the liquid copper. The initial content of oxygen in the molten copper was about 0.5 wt% and the final content was about 30 ppm. As expected, the rate of reduction of liquid copper containing such oxygen contents follows a first order kinetic law, but depending on the oxygen content, there are two controlling stages with different kinetic constants. Over the range of 500 ppm of oxygen dissolved, the first order kinetic constant k was found to be 3.32 × 10−4 m/s, but below 500 ppm of oxygen, the constant decreased to 0.31 × 10−4 m/s at 1473 K. A series of experiments was carried out at different temperatures (1423 K, 1473 K, 1523 K and 1573 K) in order to determine the activation energy, which was found to be 54 kJ/mol. At the same temperature (1473 K), graphite disks floating on the liquid surface were used to compare with graphite rods. It was found that the rate of reduction per unit area was 1.6 times higher with rods than with floating disks, due to the stirring of liquid copper produced by gas evolution which in the case of graphite disks was much lower than in the case of rods.