Direct reduction of copper slag with H2 and CO: Effects of CaCO₃ on reduction kinetics

Abstract

Background

The choice of reductants and additives as well as the reduction process is critical to reduce energy consumption, improve quality and reduce costs. As the production capacity of copper slag has surged in modern industry, the efficient utilization of iron resources contained within it has emerged as a prominent research focus.

Methods

In this study, copper slag was used as the object and carbon monoxide and hydrogen as the reducing agents, combined with kinetic mathematical modeling, focusing on the advantages of hydrogen reduction of copper slag and the improvement of reduction kinetic conditions by CaCO₃.

Significant Findings

The results of the study show that hydrogen reduction is more efficient when copper slag briquettes are directly reduced with H₂ and CO; Temperature and CaCO₃ had a significant effect on the reduction rate and degree of reduction of copper slag briquettes; In addition, the phase kinetic analysis of copper slag briquettes reveals that the apparent activation energy change rule is E_{phase 1} < E_{phase 2} > E_{phase 3} when CO reduces copper slag; And when H₂ reduces the copper slag, the apparent activation energy change rule is E_{phase 1} < E_{phase 2} < E_{phase 3}. This indicates that as the reaction proceeds, the product layer inside the copper slag becomes dense, and the product layer is even denser due to the higher reduction of the endpoint in the H₂ atmosphere, resulting in an increase in the internal diffusion of the gas and a continuous increase in the apparent activation energy. The apparent activation energy of gas-reduced copper slag increased significantly with the addition of CaCO₃.