Modelagem rigorosa e simulação da etapa de grelha móvel no processo de endurecimento de pelotas de minério de ferro.

Abstract

This work presents a robust phenomenological model for the Traveling Grate system in an industrial-scale iron ore pellet induration plant. The process involves a continuously moving pellet bed heated by perpendicular air streams. The aim is to integrate into a single model the detailed chemical and physical phenomena occurring within the system, including gas/pellet energy transfer, a three-stage drying mechanism, compressive strength, and kinetic models for coke combustion, magnetite oxidation, and carbonate calcination. During the model's development, two types of energy balance from the literature were evaluated. A mesh convergence analysis was performed using the Grid Convergence Index (GCI) method, which defined the mesh for the system. The model showed good agreement with process data, with a normalized RMSE of 6.30%. The simulations allowed the evaluation of key parameter influences on the temperature profile and compressive strength of the pellet along the bed. An inverse relationship was observed between the profile and quality with respect to the grate speed, pellet diameter, and bed height. The bed void fraction produced negligible impacts on the evaluated variables. Variations in pellet composition had a strong influence on the bed, with similar effects observed between magnetite and coke. Notably, coke had a significant impact on compressive strength, constrained by the vitrification phenomenon at high temperatures. This model enables the identification and critical analysis of phenomena that are difficult to detect during conventional operation and assists in defining operational ranges to optimize product quality and energy efficiency of the process.