Complex Processing of Copper Smelting Slags with Obtaining of Cast Iron Grinding Media and Proppants

The Ural region has a large number of metallurgical companies. The extraction of metals from ore is always accompanied by the accumulation of wastes. Currently, most of the wastes are stored in dumps and storage facilities forming technogenic deposits. One such that occupies huge areas is copper slag from the copper-smelting production. According to current estimations, about 2.2 tons of slag is formed for each ton of copper produced and about 24 million tons are produced annually [1]. In general, a copper slag contains about 35-45% iron and 0.4-0.5 copper, which indicates that this is a valuable secondary resource for recycling and utilization [33]. However, more than 80% of copper slag is not utilized, which makes it possible to consider this waste not only as a valuable material, but also as a potential hazard for the environment; it contaminates the soil and water with heavy elements [8]. Currently, only small amounts of the waste are recycled. In addition, technologies do not allow the complete extraction of valuable elements. This offers potential for the development of new highly efficient technologies for processing copper smelting wastes with extraction of valuable elements such as iron (Fe). Improvement of Fe quality requires a decrease in non-ferrous metal content, especially Cu. In recent years, extensive research was directed at the extraction of valuable materials from copper slags by high-temperature firing of copper conglomerates with subsequent magnetic separation or leaching of non-ferrous metals. However, these studies do not allow the complete processing of copper smelting slags. This work studies the production of iron-containing briquettes from copper-smelting slags, and their subsequent processing to obtain valuable products for metallurgical and oil companies. Keywords: briquette, reduction, cast iron, proppant

Formation of a Network Structure in the Gaseous Reduction of Magnetite Doped with Alumina

Reduction of un-doped magnetite is developed topochemically with the formation of a dense iron shell. However, the reduction of alumina-doped magnetite to wüstite proceeds with the formation of a network-like structure which consists of criss-crossed horizontal and vertical plates of wüstite. Reduction of magnetite includes the conversion of Fe3+ to Fe2+ and the movement of iron cations from the tetrahedral sites on the {400} and {220} planes of magnetite to the octahedral sites on the {200} planes of wüstite. Alumina has a negligibly small solubility in wüstite. In the reduction of magnetite doped with Al2O3, rejected Al3+ cations from wüstite diffuse to the magnetite–hercynite solid solution. Enrichment of the Fe3O4–FeAl2O4 solution with alumina in the vicinity of the reduction interface restricts the growth of {220} planes of wüstite and nucleation of {220} planes adjusted to the existing planes, preventing the merging of wüstite plates during the reduction process. Reduction of magnetite from the magnetite–hercynite solid solution practically stops when the Al3+ content at the interface approaches the solubility limit. Wüstite in the separated plates is reduced further to iron

Effect of Alumina on the Gaseous Reduction of Magnetite in CO/CO<inf>2</inf> Gas Mixtures

Reduction of magnetite doped with alumina (3, 6 and 12 mass pct Al2O3) was studied using CO/CO2 gas mixture (80 vol pct CO) at 1023 K and 1123 K (750 °C and 850 °C). The reduction rate and degree of reduction were evaluated from the weight loss of a sample with time. The reduction behavior was analyzed using the results of XRD and SEM–EDS measurements and thermodynamic analysis. Effect of alumina on the magnetite reduction depended on the alumina content and temperature. Magnetite reduction at 1023 K (750 °C) was accelerated by the addition of 3 mass pct Al2O3, however, the rate of reduction significantly decreased with the further increase in the alumina content to 6 and 12 mass pct. Different effect of alumina was observed in reduction at 1123 K (850 °C); the rate of reduction of the Fe3O4-Al2O3 mixture with 6 mass pct Al2O3 was the fastest. Reduction of un-doped magnetite was developed topochemically with the formation of a dense iron shell. However, reduction of alumina-doped magnetite to wüstite started along certain lattice planes with the formation of network-like structure. In the course of reduction, Al3+ ions diffused from wüstite to the Fe3O4-FeAl2O4 solution enriching hercynite content in the solution at the reaction interface. Further reduction of alumina-rich Fe3O4-FeAl2O4 solution resulted in the formation of micro-cracks which enhanced the rate of the reduction process