Abstract:
The scope of the present thesis is the development of a Computational Fluid Dynamics
model to describe the multiphase flow inside a structured packing absorber for postcombustion
carbon capture. The work focuses mainly on two flow characteristics: the
interface tracking and the reactive mass transfer between the gas and the liquid. The interface
tracking brings the possibility of studying the liquid maldistribution phenomenon,
which strongly affects the mass transfer performance. The development of a user-defined
function to account for the reactive mass transfer between phases constitutes the second
major concept considered in this thesis.
Numerical models found in the literature are divided into three scales due to the current
computational capacity: small-, meso- and large-scale. Small-scale has usually dealt
with interface tracking in 2D computational domains. Meso-scale has usually been considered
to assess the dry pressure drop performance of the packing (considering only the
gas phase). Large-scale studies the liquid distribution over the whole column assuming
that the structured packing behaves as a porous medium.
This thesis focuses on small- and meso-scale. The novelty of this work lies in expanding
the capabilities of the aforementioned scales. At small-scale, the interfacial tracking
is implemented in a 3D domain, instead of 2D. The user-defined function that describes
the reactive mass transfer of CO2 into the aqueous MEA solution is also included to assess
the influence of the liquid maldistribution on the mass transfer performance. At the
meso-scale, the Volume of Fluid method for interface tracking is included (instead of only
the gas phase) to describe flow characteristics such as the liquid hold-up, the interfacial
area and the mass transfer.
At the theoretical level, this model presents the particularity of including both a mass
and a momentum source term in the conservation equations. A comprehensive mathematical
development shows the influence of the mass source terms on the momentum
equation.