Download CFD-modelling of the 400 kW th test kiln at LKAB/MEFOS

Master Thesis at
Division of Energy Technology
Department of Energy and Environment
Chalmers University of Technology
CFD-modelling of the 400 kWth test kiln at
LKAB/MEFOS
Supervisor: Robert Johansson; +46317725249, [email protected]
Examiner: Klas Andersson; +46317725242, [email protected]
The production of iron ore pellets involves sintering of the pellets in order for the pellets to obtain a
higher mechanical strength. The sintering is carried out by heating the pellets to a high temperature,
around 1250˚C, and in the grate-kiln process this is done in a rotary kiln. The kilns of today are fired
with coal and this part of the pelletizing process therefore causes considerable fuel costs and
emissions of CO2. There is accordingly a large need for improvements of the energy efficiency of the
process, i.e. its fuel consumption, but also an interest in the use of alternative fuels with a lower
relative emission of CO2. Any modifications of the process must, however consider the product
quality of the pellets. For the sintering this means that any changes of the kiln or the combustion in it
must be made with consideration of the heat transfer from the flame to the pellets. Tests of process
modifications in a full scale process are extremely costly and most R&D is therefore carried out on
smaller scale test rigs and/or with modelling. Computational Fluid Dynamics (CFD) is here regarded
as one of the key tools to understand the combustion and heat transfer in the kiln.
This master thesis is an initial study of the use of CFD modelling as a tool to investigate how the
combustion in the kiln is affected by co-combustion of biomass and coal, fuel properties, air flow, air
temperature etc. Focus will be put on heat transfer effects and especially the radiative heat transfer
which is of most importance for the high temperatures in the kiln. The task involves modelling of
pulverized biomass and coal combustion in the 400 kWth test kiln at LKAB/MEFOS for which there
exist significant experimental data. The whole combustion process, including drying, devolatilisation
and char burnout will be modelled. The aim is to identify suitable submodels and areas where there
is a need for further developments of modelling strategies. The modelling will be carried out with
ANSYS/FLUENT and is suitable for one or two students who have interest and/or experience of this
tool.
a)
b)
Figure 1: a) The burner side of the test kiln, b) inside the kiln looking towards the burner.