The use of alternative raw materials is essential for establishing a circular economy in the mineral and ironmaking sectors. Therefore, this study investigates the potential of lime sludge as fluxing material during pelletization and proposes an alternative route for the usage of waste. The pellets were manufactured with different binary basicity values (CaO/SiO2) (0.15-0.45) and bentonite (0.5-0.7 wt%) and fixed carbon (0.5-1.1 wt%) contents. The results demonstrated that lime sludge has significant potential for application in pelletization. Pellet quality was evaluated using drop number, mechanical strength, tumble index, porosity, and kinetic analyses. Pellets with the optimal composition using lime sludge withstood 3.6 drops/pellet, a tumble test of 1.57 wt.%, and a mechanical strength test of 214.83 kgf/pellet and exhibited a porosity of 31.28%. Lime sludge did not influence the reducibility of the iron-ore pellets. In the temperature range of 800-900 °C, the reaction was controlled by diffusion, with Ea between 179.89 and 233.10 kJ/mol.

Abstract Production cost reduction for the Electric Arc Furnace (EAF) technology is strongly dependent on the efficiency of the electrical energy being introduced into the metal bath. Besides EAF technology, the slag foaming process is currently applied to some other equipment for steel production aiming to save energy, productivity improvements, enhance the refractory service life and inhibit steel re-oxidation. In this way, this study involved the recycling options of Crushed MgO-C spent refractories removed from the EAF without complex and costly beneficiation, with emphasis on its application as a slag conditioner, since its composition presents high MgO content. The experiments were performed in a laboratory induction furnace and the temperature was controlled at 1700°C.The initial height of the slag was recorded and foaming briquettes added into the furnace. The experiments were carried out for 30 minutes. When the foaming process was finalized, an aliquot from the slag was collected to be analyzed by chemical analysis. Then, the metal with slag was tapped into a mold. The results indicated that the best viscosity was 0.39poise. The maximum height of foam formation was observed for a binary basicity greater than 1.2. The concentration of MgO in the slag is close to the saturation point.

The aim of this work was to study the use of slags to desulfurize cast iron. It was proposed to use alumina instead of fluorspar. In addition, marble waste was used instead of lime. Simulations applying Thermo-Calc® software were carried out in order to obtain the theoretical phases using thermodynamic data. Then, a comparison between theoretical data and experimental tests were performed. Cast iron was melted in induction furnace at 1550ºC. Slags composed mainly for CaO and Al2O3 were used to desulfurize cast iron. The results showed that the desulphurization reaction was favored when the liquid phase was increased. Furthermore, it was found that cast iron desulfurization occurs by top slag mechanism. Furthermore, the desulfurization tests showed a decrease up to 90.10% in the sulfur content to the mixture containing conventional lime and 87.25% to the mixture RMF15. The slags obtained from marble waste contained MgO, which it interfered negatively in the desulfurization yield. In addition, increasing the CaO particle diameter improved the desulfurization process. The desulphurization process more favored to particle size of 500-1000 µm.