Alternative Method for Treating Electric Arc Furnace Dust: Simulation and Life Cycle Assessment

The technical and environmental aspects of treating electric arc furnace dust (EAFD) using a novel process including alkaline roasting and organic acid leaching were evaluated and compared to the globally applied conventional Waelz process. The global warming potentials of the roasting–organic acid leaching process (with co-product credits) and the Waelz processes were 7.48 and 4.71 kg CO2-eq with 33% Zn dust as the feed material. However, with decreasing Zn content, the novel process become environmentally more competitive, and with 12% Zn, the corresponding GWP values were 6.31 and 9.26 kg CO2-eq. Co-product recovery decreased the net environmental impacts from the processing of the dust, which gave some benefits to the novel process. The Waelz process was observed to be energy intensive; however, the high consumption of leaching and roasting chemicals was the issue in the novel process. The excess caustic soda in the roasting step was observed to be a significant factor in the overconsumption of the organic acid in the leaching stage, and therefore, optimization of the roasting step is crucial. Other ways to decrease leaching chemical consumption include investigating the possibility to reuse the raffinate in leaching, or scrubbing the leach calcine from acid-consuming alkali. Evaluating the impacts of novel processes early enables iterative and agile process development and the directing the focus on the problem areas.