Novel preparation process of iron powders with semisteel by rotary cup atomizer

Abstract

ABSTRACT Semisteel, the main by-product of titania slag-smelting process of ilmenite with an electric furnace, cannot be widely used in the steel-making process because of its high sulfur and low carbon contents. Hoganas and water atomization processes are currently the major iron powder production techniques in China, but both have obvious drawbacks. A novel and clean iron powder production process is suggested to enhance the added value of semisteel, improve the production efficiency, and reduce the energy and water consumption. A circle of water curtain was set around a rotary cup atomizer. The iron powders and hot vapor produced in this new process can be applied in the reducing and leaching steps of sulfate process, respectively, which is propitious to cut down the manufacturing cost of titanium dioxide and realize optimized resource allocation and highly effective utilization. The effect of rotating speed on the obtained iron granules was investigated. Result shows that the median diameter of the obtained granules decreases with the increase in rotating speed and varies from 0.55 mm to 0.49 mm when the rotating speed is in the range of 600 rpm to 1000 rpm. The atomization mechanism of the molten semisteel was calculated to follow the ligament formation mode under the given experimental conditions. The obtained iron granules were analyzed by X-ray diffraction and scanning electron microscopy. The surfaces of the iron granules are smooth and are covered with a layer of iron oxides, including Fe3O4, FeO, and relatively small amounts of Fe2O3. Reduction experiments in hydrogen atmosphere at 1173 K (900 °C) were conducted to remove the iron oxides on the surfaces of the iron granules. The oxidation degree of iron powders decreases from 14.06% to 4.33% when the particle size varies from 0.3–0.35 mm to 0.6–0.65 mm. After reduction, the iron powders have dramatically rough surfaces and large specific surface areas, which benefit their reaction as reducing agents in the sulfate process.