Utilization of blue dust fines through composite pelletization using an optimized binder system

Abstract

Utilizing blue dust (BD) fines through pelletization is a challenging task due to their finer size (<100 mu m), uneven particle size distribution, high brittleness, and hydrophobicity. The current study tried to prepare Blast Furnace (BF)-grade composite pellets from BD iron ore fines using a proportionate amount of coke fines, bentonite/organic binder system, and limestone. An organic binder (OB) was added to partially replace bentonite during pelletization of BD fines. Organic binder's properties were corroborated with bentonite. Iron ore pellet feed (61.43% Fe, 3.52% SiO2, 2.8% Al2O3, and 3.36% LOI) materials were prepared by blending iron ore with BD fines in a 70:30 wt% ratio, respectively. The corresponding impacts of the binder system and additives on the chemical and physical properties of both green and fired pellets have been evaluated through drop tests, thermal shock behavior, and compressive strength measurements. It was identified that to produce adequate cold compressive strength (>= 250 kg/pellet) and porosity (equivalent to 26%), the necessary dosage of bentonite was decreased from 15 kg/t to 5 kg/t by blending 100 g/t of organic binder; as a result, the proportionate amount of silica and alumina was decreased without compromising on the mandatory pellet properties. Various mineralogical investigations, including FTIR, TG-DTA, XRD, SEM-EDS, and metallurgical properties such as SI, RI, and RDI, have contributed to achieving a standard BF grade fired pellet.