Preheating of hot briquetted iron

In an earlier study we have shown that when Hot Briquetted Iron (HBI) is pre-heated in an inert atmosphere, internal reduction of Fe0 occurs at temperatures above 500°C. In a carbon dioxide atmosphere at temperatures above 700°C, oxidation occurs only externally whilst the internal reduction reactions proceed simultaneously. In this investigation these simultaneous reduction and oxidation reactions have been studied in atmospheres resembling more closely the expected composition of the off-gas of an electric-arc furnace. Isothermal and non-isothermal thermogravimetry (TG) as well as differential thermal analysis DTA) techniques were used. The behaviour of HBI in oxidising atmospheres at elevated temperature is discussed and it is shown that simultaneous external and internal reduction occur even when the oxidation potential of the preheating gas is increased significantly. The optimum temperature for preheating is between 750°C and 800°C.