Sticking mechanism of low grade iron ore-coal composite in rotary kiln reduction

A rotary kiln (Phi 1.5 m x 15 m) was designed to verify feasibility of the reduction technology of a low grade iron ore with low temperature via ore-coal composites. One of the troublesome problems was the sticking of kiln burden during the reduction process. Reduction behavior and sticking mechanism of composite pellets in the rotary kiln were investigated in this paper. Technology of X-ray diffraction (XRD) and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) were applied to reveal the sticking mechanism. Products with metallization degree of 84.83% were obtained after reduced in the rotary kiln. Reduction of Fe2O3 to FeO and reduction of FeO to Fe were mainly occurred at location of 9 m-13.5 m and 5.5 m-11.5 m in the rotary kiln, respectively. Pellets or pellets powders were bonded by low melting point substances formed in coal ash: hedenbergite and fayalite. These low melting point substances were mainly generated from coal ash and formed at location of 5.5 m-11.5 m in the rotary kiln. Hedenbergite occurred firstly, followed by bonding of pellets or pellet powders and formation of fayalite. Melt of fayalite intensified agglomerating behavior. (C) 2018 Elsevier B.V. All rights reserved.