Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.
Chemical looping combustion (CLC) as a potential CO2
capture technology has been considered as a promising and
likely alternative to traditional combustion technology to
mitigate the CO2 emission due to its prosecution of CO2
sequestration at a very low cost. In CLC, solid oxygen carriers
are introduced to transfer the oxygen necessary for the
combustion from air through the initial oxidation in air reactor
and subsequent reduction in fuel reactor. The CLC unit utilized
in this study is composed of two interconnected fluidized bed
including a circulating fluidized bed as the air reactor and a
bubbling fluidized bed as the fuel reactor. While a number of
studies on the hydrodynamic behaviour of the CLC process in
fuel reactor have been documented in the open literature, there
have been limited studies on the correlation between the bubble
formation and the local volume fraction. The hydrodynamic
behaviours and reactive characteristics of oxygen carriers are
still not fully understood although a variety of experiments and
simulations have been performed. This paper aims to
investigate the CLC process in a fuel reactor using the CFD
modelling, coupled with the heterogeneous reactions and
investigating the hydrodynamics and reaction kinetics of the
CLC process in the fuel reactor. A parameter correlating the
occurrence of bubble and dynamic parameters is proposed. The
parameter can be acted as an indicator of time-dependent
bubble evolution with a potential to be adopted in the CLC for
controlling the bubbling phenomena since the occurrence of the
bubbles at specific positions is highly correlated with the local
large eddies embedded in the flow. The static bed height
variations in the fuel reactor system affecting the flow
behaviour and kinetics of the CLC process are also discussed.
The results obtained from the CFD simulations indicate clearly
that the CFD model developed in the current study reasonably
forecasts the hydrodynamic behaviour and important
phenomena observed in the fuel reactor.
