Direct reduction kinetics of copper slag

China has large reserves of copper slag that contains a variety of valuable metals and has a high secondary utilization value. In order to reveal the carbothermal reduction mechanism of iron extraction from copper slag, isothermal reduction experiments of carbon-bearing pellet in copper slag were carried out with anthracite as reducing agent, and the kinetic analysis was conducted to provide reference for the utilization of copper slag. The reduction temperatures set in this experiment were 1 000 ℃, 1 050 ℃, 1 100 ℃, 1 150 ℃ and 1 200 ℃, and the C/O molar ratio was 1.0. The results show that the temperature has an important effect on the reaction rate in the isothermal reduction experiment of carbon-bearing pellets in copper slag. The main rate limiting step of this reaction is gas phase diffusion, and the activation energy value is 118.059 kJ/mol. The phased kinetic analysis shows that the activation energy is in the range of 61.54~146.98 kJ/mol, and the value of the activation energy changes with the degree of reduction. The specific performances are as follows: the reaction activation energy value in the first stage is low, and the reason may be that in the initial stage of the reaction, the iron oxide (Fe₃O₄) contained in the original copper slag participates in the reaction first; the reaction activation energy in the second stage is higher, because the iron oxides in the original copper slag has all basically got reacted. The iron exists in the state of liquid olivine which lowers the porosity of the pellet, hindering the diffusion of gas within the pellet.