Mathematical model of the pellet thermal process in an annular cooler

Based on the principle or laws of energy conservation, fluid flow, and heat and mass transfer, a mathematical model of pellet cooling and oxidation was established and solved by a three-diagonal matrix algorithm. Its numerical simulation software was developed with Visual Basic 6.0. A field test was performed and the established model was verified by practical measured results. The maximum relative error between computational and measuring results is 4.8%, indicating that the developed model is correct and reliable. A numerical simulation of the pellet thermal process in an annular cooler was conducted with the developed computational software and the temperature distribution of the pellet bed was gained. The simulation results show that the main influencing factors on the cooling process of the pellet bed in an annular cooler are air velocity in the first cooling zone, pellet bed thickness, pellet size and the annular cooler's velocity. Under the research condition, the reasonable operation parameters are the following: the range of pellet bed thickness is from 550 to 800 mm, the range of pellet size is from 7 to 16 mm, the range of air velocity in the first cooling zone is from 1.2 to 2.5 m · s-1, and the range of the annular cooler's velocity is from 1.0 to 1.5 m · min-1.