An efficient approach to utilize copper smelting slag: Separating nonferrous metals and reducing iron oxide at high temperature.

Over 50 million tons of copper slag are produced worldwide annually. Stacking is currently the primary method used to treat copper slag, resulting in resource wastage and environmental issues. Using slag as a raw material in the steel industry is areasonablesolution. However, the presence of nonferrous metals degrades steel performance and corrodes smelting equipment, and the remaining slag poses environmental and sustainable challenges. Thus, this study focused on removal of nonferrous metals from copper slag and subsequent reduction of iron oxide. The experimental results showed that increasing the percentage of the chlorinating agent (calcium chloride), temperature, and duration, the removal percentage of copper initially increased linearly, then plateaued. The acidity coefficient had a marginal effect on copper removal percentage. The optimum chlorination roasting conditions were 13 % calcium chloride, 1373 K, and 0.5 h, resulting in removal percentages of 90.3 %, 81.9 %, and 82.7 % for copper, zinc, and lead, respectively. The appropriate oxygen partial pressure for chlorination roasting was 10-5-0.7 atm. The reduction percentage of iron oxide was approximately 82 % under roasting conditions of 1.5 h at 1373 K. Based on these results, a novel scheme for copper slag utilization is proposed that involves chlorination roasting for nonferrous metal removal, reduction roasting for iron oxide reduction, and melting to obtain molten iron and separate molten slag. The iron and slag are used for steel manufacturing and rock wool preparation, respectively. This scheme provides apromisingway to efficiently use copper slag, which will reduce primary resource consumption and pollution.

Generation, utilization, and environmental impact of ladle furnace slag: A minor review.

More than 20 million tons of ladle furnace slag are produced annually. This slag is mainly treated by stockpiling; however, stacking results in dust and heavy metal pollution. Utilizing this slag as a resource can reduce primary resource consumption and eliminate pollution. In this review, existing studies and practices related to slag are discussed, and applications for different slag types are analyzed. The findings reveal that under alkali- or gypsum-activated conditions, CaO-SiO2-MgO, CaO-Al2O3-MgO, and CaO-SiO2-Al2O3-MgO slags may act as a low-strength binder, a garnet- or ettringite-based binder, and a high-strength cementitious material, respectively. Partial replacement of cement with CaO-Al2O3-MgO or CaO-SiO2-Al2O3-MgO slag can adjust the settling time. Meanwhile, CaO-SiO2-Al2O3-FeO-MgO slag combined with fly ash can be used to prepare a high-strength geopolymer, and CaO-Al2O3-MgO and CaO-SiO2-MgO slags may yield high carbon dioxide sequestration percentages. However, the aforementioned applications could lead to secondary pollution because these slags contain heavy metals and sulfur. Removing them or suppressing their dissolution is therefore of significant interest. Reusing hot slag in a ladle furnace could be an efficient utilization strategy because it can recover heat energy while utilizing the components of the hot slag. However, adopting this approach necessitates the further development of an efficient method for removing sulfur from hot slag. Overall, this review elucidates the relationship between the utilization method and slag type and identifies future research directions, thereby providing references and guidance for future research on slag utilization.