Causes of the shell and core structure and layered inhomogeneity in iron ore pellets

Abstract

Equations for a multiple shell model of a sphere where induration occurs under transient temperature conditions are written and solved on a digital computer using a repeated extrapolation technique. Parameters representative of industrial induration and shrinkage-kinetic data for a commercial magnetite concentrate are used in the calculations. Results show that large temperature gradients within pellets are characteristic of the more severe heating conditions, which in turn can lead to large shrinkage gradients in the radial direction from pellet surface to the core and result in the defective pellet texture. Experimental evidence is discussed and a “propensity index,” derived from the calculations, is introduced and compared with experience.