Mineralogical investigation on preheating studies of high LOI iron ore pellet

Abstract

Present pelletization practices are facing problems to handle high loss on ignition (LOI) concentrate generated from goethitic-hematite iron ore containing higher goethite, gibbsite, and kaolinite. These minerals need to completely release their LOI in the preheating zone of pellet induration process. If it is not, crack develops in the pellet, which reduces cold crushing strength (CCS) also deteriorates pellet quality. In this study, this issue has been addressed by taking variable preheating temperature (850 degrees C, 950 degrees C, 1000 degrees C, 1100 degrees C) and residence time (20, 25, 30, 35 min.). Pellets were prepared from three iron ores with LOI (2.64, 4.85, and 9.19%). Effect of ore mineralogy on the drying characteristics of the pellet has been established. Preheated pellet CCS, porosity and morphology have been investigated. The coordination between preheating temperature and residence time to acquire desired CCS (50 kg/pellet) varies ore to ore. A detailed morphological investigation has been performed to address the inappropriate heating effect by the use of stereomicroscopy, optical microscopy and scanning electron microscope study. The pellet properties are dependent on the presence of kaolinite and goethite percentage.