Design and simulation of pressure swing adsorption cycles for CO2 capture
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Date
26/11/2015Author
Oreggioni, Gabriel David
Metadata
Abstract
Carbon capture and storage technologies (CCS) are expected to play a key role in the
future energy matrix. Different gas separation processes are under investigation with the
purpose of becoming a more economical alternative than solvent based post combustion
configurations. Previous works have proved that pressure swing adsorption (PSA) cycles
manage to reach similar carbon capture targets than conventional amine process but with
approx. a 50% lower specific energy consumption when they are applied at lab scale. These
encouraging results suggest that research must be undertaken to study the feasibility of this
technology at a low to medium power plant scale.
The simulation of PSA cycles is a computationally challenging and time consuming
task that requires as well a large set of experimentally measured data as input parameters. The
assumption of Equilibrium Theory reduces the amount of empirically determined input
variables that are necessary for modelling adsorption dynamics as well as enabling a simpler
code implementation for the simulators. As part of this work, an Equilibrium Theory PSA cycle
solver (Esim) was developed, the novel tool enables the quantification of the thermodynamic
limit for a given PSA cycle allowing as well a pre-selection of promising operating conditions
and configurations (high separation efficiency) for further investigation by using full governing
equation based software The tool presented in this thesis is able to simulate multi-transition
adsorption systems that obey any kind of equilibrium isotherm function without modifying its
main code.
The second part of this work is devoted to the design, simulation and optimisation of
two stage two bed Skarmstrom PSA cycles to be applied as a pre-combustion process in a
biomass gasification CHP plant. Simulations were carried out employing an in house software
(CySim) in which full governing equations have been implemented. An accurate analysis of
the operating conditions and cycle configurations was undertaken in order to improve the
performance of the carbon capture unit. It was estimated that the energy penalty associated
with the incorporation of the adsorptive pre combustion process was lower for a conventional
post combustion solvent unit, leading as well to lower specific energy consumption per unit of
captured CO2 and higher overall efficiencies for the CHP plant with installed pre-combustion
PSA cycles.
This work is pioneer in its kind as far as modelling, simulation, optimisation and
integration of PSA units in energy industries is concerned and its results are expected to
contribute to the deployment of this technology in the future energy matrix.