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HEAT, MASS AND MOMENTUM TRANSFER WITHIN AN IRON ORE PELLET DURING DRYING

Anna-Lena Ljung
Division of Fluid Mechanics, Luleå University of Technology, SE- 971 87, Luleå, Sweden

T. Staffan Lundstrom
Division of Fluid Mechanics, Luleå University of Technology, SE- 971 87, Luleå, Sweden

Iron ore pellets is one of the most refined products for mining industry. Being such, there is a natural driving force to enhance the pelletization in order to optimize production and improve quality especially since the process is time and energy consuming. In order to be successful it is of highest importance that the pelletization process is known in detail. Following this demand, heat and mass transport within a single pellet during drying is modeled with aid of Computational Fluid Dynamics. A two dimensional rectangular domain is chosen to represent the porous media within the pellet and the governing equations are set up for one directional flow through it. Convective transport of water and air through the capillaries of the porous media is computed from Darcy's law being adapted to a two-fluid system. Vaporization by boiling is taken into account and two energy equations are used to calculate the temperature distribution, one for the liquid and solid, and one for the gas. To start with, iteration errors and discretization errors are found to be negligible. Following this a sensitivity analysis shows that it is important to use a realistic value of the convective heat transfer coefficient when the vaporization of water is the dominating drying mechanism while the temperature of the solid and capillary movement of water is not influenced to the same extent. The derived model can be applied to a number of numerical set-ups such as a single pellet in an infinite space.

pages CHT-08-287

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