Abstract
The carbothermic reduction of slag in silicomanganese production is accompanied by the release of carbon monoxide. This gas can accumulate as bubbles within the slag, leading to foaming and, potentially, disturbances to furnace operation. This study investigated the reduction in the slag together with its foaming using a sessile drop furnace. Five silicomanganese slags produced from industrial raw materials (Assmang ore, Comilog ore, high-carbon FeMn slag with quartz, and FeS additions) were reduced by a graphite substrate at isothermal conditions (i.e., 1540–1660 °C) under CO atmosphere. The reduction reaction was tracked by photographing the slag droplet, and the cyclic expansion and burst of the droplet were used to estimate the gas evolution. The reacted samples were analyzed by wavelength-dispersive X-ray spectroscopy (WDS) to determine MnO and SiO2 reduction. While no foaming was observed using Comilog ore, extensive retention of CO in the slag phase was observed when using Assmang ore or Assmang with high-carbon FeMn slag. The beginning of foaming was attributed to an increase in the reaction rate; the absence of foaming when using Comilog can be attributed to the acidity of the charge. Addition of sulfur to the Comilog-based charge did not influence the reduction.
Highlights
Silicomanganese (SiMn) is commonly used in steelmaking for its desulphurizing and deoxidizing properties as well as for the contributions of its alloying elements to the properties of steel [1]
The present study focused on the chemical and foaming behavior of the slag during reduction in the continuation of a series of works on the kinetics in silicomanganese production [3,4]
The sessile drop technique tended to agree to what was obtained in a tube furnace for some samples but disagreed for the Comilog ore (Com) charge
Summary
Silicomanganese (SiMn) is commonly used in steelmaking for its desulphurizing and deoxidizing properties as well as for the contributions of its alloying elements to the properties of steel [1]. Typical tapped SiMn alloys contain approximately 20 wt.%. The production of silicomanganese is accomplished through the carbothermic reduction of MnO- and SiO2 -rich oxides. The raw material charges commonly involve a mixture of Mn ore, ferromanganese slag (as another source of manganese), quartz, and coke. A great deal of research work has been done in the field of pyrometallurgy to fulfill the dual ambition of clarifying the reaction mechanisms and understanding the role of the raw materials’ composition. Concerning the SiMn production kinetics, non-isothermal experiments have shown that the reduction mechanism is two-staged [2,3], a slow stage at low temperature being followed by a rapid stage at approximately 1600 ◦ C
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