Iron ore pellets are LKAB's most refined product and the company is one of
the leading suppliers in the world. There is for competitive reasons a
great need for research in order to optimize the production and improve
quality.
The global goal with this project is to develop a tool with which the
drying zone of the straight grate pelletizing plant in Malmberget, Sweden,
can be optimized. The aim with this thesis is to make a model of
temperature and velocity distribution in the up? draught drying zone,
without any regard to moisture content in green balls.
The velocity distribution is described by laws of fluid dynamics in porous
media. The dominating heat transfer mechanism is convection due to the hot
air passing through the pellet charge. The air temperature is calculated
from the energy equation and the average temperature of the pellet charge
is calculated from a diffusive transport equation. Simulations of velocity
and temperature distribution are made with aid of Computational Fluid
Dynamics and the software CFX 10.0 is used. Result from simulations show a
rapid cooling of air due to the high specific surface area in the porous
material.
Experiments are performed at the Metallurgical Research Institute AB
(MEFOS). The goal is to use experimental results to define unknown material
parameters and to validate the simulation model. Two sets of experiments
are carried out within the frames of this thesis. The first set has the aim
to secure the equipment from possible measurement errors. In the second set
of experiments, flow through pellets of different sizes and packing are
investigated and compared with available equations.
Conclusions are that it is possible to make a heat transfer model in CFX
10.0 which calculates solid and fluid temperature. The experimental
equipment at MEFOS is reliable for experiments made on small grains if
results are to be implemented in the simu...
