On the drying rates of individual iron oxide pellets

After agglomeration, iron oxide pellets are sintered in continuous furnaces to develop the mechanical properties required by iron making plants. In the first zones of the furnace, pellets are dried by the hot recycled gas. The objective of the study is to model their drying kinetics. For that purpose, individual pellets, instrumented for temperature measurement, are dried in a laboratory furnace equipped with a thermo-balance. The results show that there are four stages in the drying process: 1—an evaporation of the water film at the pellet surface; 2—an hybrid regime with surface film evaporation and apparition of dry spots with evaporation fronts moving within the pellet; 3—a shrinking wet core leaving behind the evaporation front a dry shell where there is water vapour diffusion; 4—a change of diffusion into bulk transportation of water through the dry shell, when the evaporation front is close to the boiling point. Mass and heat transfer equations are numerically solved, and the simulated values compared to the experimental results.