Effect of CaO and MgO additives on the compressive strength of pellets: Exploration on the decisive stage during induration

Abstract MgO additives were demonstrated to have a negative effect on the strength of pellets and the addition of CaO additives can eliminate such effect. To further explore and clarify the decisive stage that additives affect the compressive strength of pellets during the induration process−preheating stage or roasting stage, briquettes with various compositions were prepared by using pure reagents and were preheated or roasted subsequently. Results show that the phase of briquettes changed significantly during roasting stage rather than preheating stage; when CaO-added briquettes were treated under the roasting process, liquid phase formed and accelerated the reaction between MgO and Fe2O3, thus, the roasting stage plays a decisive role in the change of pellets' strength. Interaction couple experiment was further conducted, the diffusion performance of Mg and Fe were studied and results proved the acceleration effect of lime on the reaction between magnesium fines and magnetite.