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Author
Hernández Narciso, Clàudia Rosa
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Abstract
Human activities have increased carbon dioxide emissions, which leads to a long-term increase in the average temperature of the Earth’s climate system. There has been a growing concern for climate change and its damages to the planet. In the context of sustainable development and clean energy production, where carbon capture and storage (CCS) is widely considered as part of the solution, aqueous amine-based chemical absorption is known as the most promising technology because of its high efficiency and selectivity. 30%wt Aqueous Monoethanolamine (MEA) is the most utilized amine because of its affordability, its high-water solubility and fast kinetics. However, these aqueous amine solvents are prone to degradation and undergo side reactions leading to negative plant operation and economics.
The objective of this study is part of a long-term project focused on improving the understanding of the balance between kinetics and mass transfer of MEA under different CO2 loading conditions. The first part focuses on developing a robust and sensible model of MEA-based chemical absorption, including the minimisation of the energy costs, under various volumetric and thermal conditions but without accounting for degradation products. The second objective includes addition of the predominant degradation product 1-(2-Hydroxyethyl)-2-imidazolidinone (HEIA) in the MEA-based chemical absorption process, with particular assessment on reboiler duty.
Modelling of a MEA-based chemical absorption process has been carried out with Aspen Plus version 11. The objective of the flowsheet developed is to obtain 90% CO2 capture at 99% purity for a given feed gas thereby minimizing the energy costs of the process particularly for reboiler duty of the stripper column. HEIA was added to the modelling using several correlations to predict thermophysical properties based on previous experimental work.
A model was successfully developed and was validated with simulated industrial or pilot plant CO2 absorption capture, including the process and environmental energy penalties. CO2 loading, lean solvent flow rate and column dimensions are the key variables for optimal operating conditions to minimize the energy requirement. In the presence of HEIA, there is an increased solvent flow rate and column dimensions for the set CO2 capture conditions. This model is relevant for the design of large-scale CO2 capture plants which need to consider not only the effect of HEIA, but also under which conditions it is economically feasible to introduce a feed and bleed control with fresh MEA.
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