Mechanism of pore formation in copper slag reduction: A clarification combining experiments and simulation

Copper slag still contains a large amount of iron resources after flotation, and direct storage is a serious waste of resources. Direct Reduced Iron(DRI) are prepared by reduction of copper slag which requires a large amount of fossil energy and emits carbon largely. In this work, straw and straw charcoal were used as reducing agents to reduce flotation copper slag to prepare DRI. The pore model of the DRI was constructed via micro/nano stimulation, and the direct reduction kinetic characteristics of the biomass copper slag composite pellets were analyzed. The results show that the addition of straw is beneficial for the direct reduction of copper slag. The straw is pyrolyzed to produce a reducing pyrolysis gas to prereduce the pellets while leaving pores to improve the kinetic conditions for the subsequent direct reduction of copper slag. Compared with traditional fossil fuels such as anthracite, the metallization rate of DRI prepared with straw and straw charcoal as reducing agents to reduce copper slag increased from 85 % to 96.54 %. This process can reduce carbon emissions by 0.26 ∼ 0.52 t per ton of molten iron. This study proposes a feasible, low-carbon and efficient flotation copper slag treatment method that can fully recover the iron resources in flotation copper slag and solve the industry problem that flotation copper slag can be stored and disposed of only. It is helpful to promote the organic combination of nonblast furnace ironmaking, the comprehensive utilization of copper slag and the comprehensive utilization of biomass resources.