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Within
the Ph.D. program, progress have been made in the numerical modeling
the reactor during the last few months:
- A
numerical model has been developed for the purpose of understanding
the process and the kinetics of the calcination reaction and for
being able to scale-up the solar lime reactor. The model takes
into account various heat transfer modes (conduction, convection,
and radiation) as well as chemical reaction kinetics. So far,
the program calculates the temperature distribution and the degree
of decomposition as a function of time in a simple geometry.
- The
numerical model has been validated with data from a set of experiments
performed at ETH's High-Flux Solar Simulator. For different time
periods and flux intensities, a thin layer of 2-3 mm CaCO3 particles
was placed on a SiC plate and directly irradiated by the artificial
concentrated solar radiation. Although quite a good agreement
was found between the numerical model and the experimental results,
it is suggested to simplify the rather complex experimental set-up
in order to be able to better determine the relevant experimental
parameters and some of the material properties.
- Currently,
a method for modeling unsteady systems including chemical reactions
is being developed. It is suited for the simulation and calculation
of chemical processes in different types of solar reactors, but
it can also be applied to combustion processes. Emphasis is given
to the coupling of thermal radiation with chemical kinetics.
In addition, a CFD (Computational Fluid Dynamics) study has been
performed to investigate the convection heat losses in the direct-heated
reactor with the conical reaction chamber. Preliminary results
suggests that only 6-10% of the unaccounted heat losses are due
to natural convection through the open aperture. However, the
effects of the CO2 release were not yet fully taken into account.
The CFD model included conduction and radiation (Monte-Carlo)
heat transfer as well as chemical kinetics. It will be extended
to the new indirect-heated reactor geometry.
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