Relationship between the agitation torque of the wet iron ore powder and pellet properties

Abstract

Handling dephosphorized iron-ore powders with varying sizes and degrees of reduction is a pivotal issue in the iron-making process. A wet granulation process is employed for using dephosphorised fine ore powders as raw materials; however, it is difficult to determine the optimum water content to produce green pellets with the required physical properties because of the significant variation in the physicochemical properties of the dephosphorized ore powders. Thus, developing a method to determine the optimum water content for producing green pellets from fine ore powders with various degrees of reduction is necessary. In this study, we propose a method to estimate the optimum water content using agitation torque, which is a rheological property of wet ore powders. To this end, we investigated the effects of the hematite/magnetite fraction in the raw ore powder mixture on the agitation torque and green pellet properties. The characteristics of the agitation torque profile and green pellet properties (density and compressive strength) changed significantly depending on the hematite/magnetite fraction. Subsequently, we investigated the relationship between the agitation torque and green pellet properties, which revealed that the density and compressive strength of the green pellets correlated well when the product of the agitation torque and tumbling time was employed as the explanatory variable, regardless of the hematite/magnetite fraction. Thus, the properties of green pellets produced from fine ore powders with various degrees of reduction can be estimated based on the rheological properties measured by the agitation torque.