Reduction Performance Evaluation and Life Cycle Assessment of a Copper Slag Biomass Direct Reduction Process

In the face of the dual dilemma of “shortage of raw materials” and “high carbon emissions” in the iron and steel industry, the copper slag biomass reduction process is an environmentally friendly solution. However, there are still some problems in this technology, such as an unclear biomass reduction mechanism and unquantified environmental advantages. In this study, a composite pore-forming strategy was proposed to strengthen the direct reduction process of the copper slag biomass. By comparison of the reduction performance of the traditional process and the biomass direct reduction process, the synergistic mechanism of the composite pore-forming agent was systematically explored, and its environmental benefits were quantified by a life cycle assessment. The results show that the composite pore-forming agent constructs a multilevel connected pore network through the temperature-gradient synergistic effect of “low-temperature decomposition–medium-temperature conversion–pyrolysis pore forming”, which increases the porosity of the pellets to 59.81%, and the particle size of the DRI product is refined to 20.11 μm. Compared with traditional coke pellets, the iron reduction rate of biomass pellets with magnesium carbonate-ammonium bicarbonate increased from 84.36 to 95.37%, and the removal rates of lead and zinc increased from 81.49 and 77.45% to 96.76 and 97.58%, respectively. The life cycle assessment confirmed that the carbon emission per ton of copper slag of this process was 42.6% lower than that of the traditional coke process and that the environmental impact was greatly reduced. The “technical performance–environmental impact” correlation system constructed in this study provides a new technical path and scientific support for the low-carbon resource utilization of copper slag.