Modelling of heat transfer in a straight grate pellet induration reactor complemented with plant scale experiments

Abstract

Straight grate furnaces are widely used for induration of hematite pellets where typically 1%–2% carbon is added to the green mix to help in generating heat by combustion. The quality of the pellets in such reactor varies from top to bottom of the bed as different layers of pellets are exposed to varying thermal and gaseous environments. The thermal evolution (as a function of time) at a specific location in a moving pallet car was studied through plant scale experiments. Subsequently, these experimental temperature measurements were supplemented with a 1-D heat transfer model of the pellet bed. It was observed, from simulation results, that peak temperature faced by the pellets in top layer and bottom layer of the pellet bed differed by 105°C. The effect of bed height and grate velocity on the pellet bed thermal profile was studied using the model. With increase in production rate through increase in grate velocity and bed height, this difference further intensified. These findings can provide insight to plant operator to optimise production rate.