Modélisation du captage post-combustion du CO2 avec évaluation de la dégradation des solvants

in Récents Progrès en Génie des Procédés (2013), 104

Post-combustion CO2 capture in power plants is one of the most mature technologies for a short-term and large-scale decrease of CO2 emissions while simultaneously addressing the growing global energy ... [more ▼]

Post-combustion CO2 capture in power plants is one of the most mature technologies for a short-term and large-scale decrease of CO2 emissions while simultaneously addressing the growing global energy demand. CO2 is chemically absorbed in an amine solvent that can be regenerated at higher temperature, producing a pure CO2 stream. However, the large impact of this technology on the power plant efficiency and the environmental penalty are the main drawbacks for large-scale implementation. In this work, an innovative approach combining process modeling and evaluation of the environmental penalty due to amine degradation is presented. Based on experimental results, the kinetics of solvent oxidative and thermal degradation is estimated and included in the process model developed in Aspen Plus. Using this model, the influence of operating parameters like the oxygen concentration in the flue gas or the solvent regeneration pressure is studied. This model is a first step for a multi-objective optimization of the CO2 capture process, assessing both energy and environmental penalties of this technology. [less ▲]

CO2 CAPTURE in POWER PLANTS: Process Simulation and Solvent Degradation

Poster (2012, November)

Presentation of the research themes studied at the University of Liège in the field of CO2 capture

Modélisation des grands systèmes chimiques: travaux pratiques

Learning material (2012)

Notes de Travaux pratiques à l'attention des étudiants 1ere master ingénieur civil chimiste et sciences des matériaux

Study of 2-Ethanolamine degradation

Conference (2012, January)

One major drawback of the post-combustion CO2 capture using conventional amine solvents is solvent degradation, which can be due to thermal as well as oxidative mechanisms. Degradation affects the CO2 ... [more ▼]

One major drawback of the post-combustion CO2 capture using conventional amine solvents is solvent degradation, which can be due to thermal as well as oxidative mechanisms. Degradation affects the CO2 capture process since it may cause corrosion, foaming and fouling, possibly inducing a decrease of the solvent efficiency and high additional operating costs due to solvent replacement. In order to study degradation of conventional amine solvents as well as degradation of novel solvents, a degradation test rig has been built at the University of Liège in collaboration with the company Laborelec, member of the GDF SUEZ group. Since degradation generally occurs within a few months in real plant conditions, this equipment has been designed to allow the study of different degradation mechanisms under accelerated conditions, at high temperatures (up to 140°C) and high partial pressures in oxygen and CO2 (total pressure up to 20 bar with varying gas composition). An advantage of this degradation test rig is that it can be used in batch as well as in semi-batch mode with constant gas flow. High gas-liquid contact efficiency is also ensured thanks to a mechanical agitation system combined with gas bubbling. For a typical run, 300g of aqueous amine solution (30 wt % MEA in water) is introduced into the reactor and degraded during two weeks. The degraded solutions are then analysed using high pressure liquid chromatography (HPLC) for MEA quantification and gas chromatography with flame ionization detector (GC-FID) for the characterization of degradation products. The gas phase is analysed by Fourier Transform Infra Red spectroscopy. The final objective of this work is to implement the data obtained from experimental results on the degradation test rig into an existing simulation model that has been developed based on an existing pilot plant. [less ▲]

Modeling post-combustion CO2 capture with amine solvents

in Pistikopoulos, E. N.; Georgiadis, M. C.; Kokossis, A. C. (Eds.) 21st European Symposium on Computer Aided Process Engineering – ESCAPE 21 - Proceedings (2011)

Carbon capture and storage is a technology that can contribute to face the challenge of rising energy demand combined with a growing environmental awareness. In the present work, the CO2 capture process ... [more ▼]

Carbon capture and storage is a technology that can contribute to face the challenge of rising energy demand combined with a growing environmental awareness. In the present work, the CO2 capture process with monoethanolamine (MEA) is modeled using the simulation tool Aspen Plus. Two different modeling approaches are studied and compared: the equilibrium and the rate-based approaches. An optimization of key process parameters is performed and process modifications are studied with the objective of improving the global process energy efficiency. [less ▲]

Modeling post-combustion CO2 capture with amine solvents

Conference (2010)

Oral communication at the Cape-forum, Aachen, 2010. Modeling CO2 capture process and optimization of some process parameters with an equilibrium-based model.

Optimal design of a CO2 absorption unit and assessment of solvent degradation

Conference (2010)

Presentation of the main research fields of my PhD thesis at the University of Liège

Modeling of a pilot plant for the CO2-reactive absorption in amine solvent for power plant flue gases

Master's dissertation (2009)

During the combustion of fossil fuels in power plants, large carbon dioxide quantities are produced and released into the atmosphere. Carbon dioxide is a greenhouse gas and its role in the current global ... [more ▼]

During the combustion of fossil fuels in power plants, large carbon dioxide quantities are produced and released into the atmosphere. Carbon dioxide is a greenhouse gas and its role in the current global warming is widely accepted by the scientific community. Many projects have been launched in the last few years that aimed at developing processes for the mitigation of carbon-dioxide emissions. Among the different carbon capture and storage technologies (CCS), the post-combustion capture of CO2 in power plants seems promised to a large development. The objective of the present work is to model a pilot installation that should be built in the next few months. This pilot installation will be retrofitted in an existing coal-fired power plant in order to treat 5000 Nm³/h flue gas in two process trains. It is planed that 90% of the CO2 present in the flue gas can be removed, which corresponds to a capture rate of about 1 ton CO2/h. The role of this simulation is to facilitate the comprehension of the capture phenomena and to highlight the key process parameter and their influence on the obtained results. Furthermore, some technical improvements are studied that aim at a reduction of the energy consumption of the CO2-capture process. The simulation tool Aspen Plus has been employed to model the pilot installation. It has been assumed for the simulation requirement that the equilibrium state was achieved for each stage of the mass transfer columns. Mass transfer limitations and reaction kinetics have then been neglected. The model described in this work has been successfully developed for one process train treating a flue gas flow of 2500 Nm³/h. The solvent is monoethanolamine (MEA), which is the most employed solvent in CO2-capture technologies. The CO2-recovery rate has been fixed to 90%. The most relevant process parameter that have been studied with the developed model are the solvent flow rate, the solvent concentration, and the stripper pressure. An optimum for the solvent flow rate has been identified at 11,75 m³/h, corresponding to a thermal energy consumption of 3,76 GJ/ton CO2. When increasing the stripper pressure, the thermal energy consumption decreased up to 16%. The fact that a pressure increase in the stripper leads to a temperature increase and the strong temperature dependence of the CO2-partial pressure explained this reduction of the thermal energy consumption. However, an increase of the stripper pressure induces solvent degradation problems, corrosion and a more complex equipment design. The MEA-concentration has been varied between 27 and 37 wt-%. When using a more concentrated solvent solution, the solvent is easier to regenerate. Consequently, the thermal energy consumption of the process decreased up to 12,5%. However, corrosion problems limit the use of concentrated solvents so that the MEA-concentration in capture-processes is generally adjusted to 30 wt-%. Furthermore, two process modifications have been tested successfully. First, a partial evaporation of the regenerated solvent after the stripper outlet has been studied. The gaseous product of this partial evaporation was compressed and recycled to the stripper. A decrease by 25% of the thermal energy consumption could be achieved. However, compression work has to be furnished. When calculating the improvement on the basis of exergy, then the exergy of the capture process decreased by 18%. The second modification that has been studied is a solvent intercooling between two absorber stages. It has been observed that intercalating the intercooler between absorber bottom stages gives better results than between absorber top stages. Simulation results have shown that the thermal energy consumption decreased by up to 6%. In the case of a flue gas pre-cooling before the absorber inlet, about the same reduction of the thermal energy requirement could be achieved. Finally, a thermal energy consumption of 2,82 GJ/ton CO2 has been achieved in the best case, corresponding to a process exergy reduction by approximately 18%. The developed model allows further improvements so that the optimization of the CO2-capture process could be pursued. Since a detailed study of the process model could help the planning of an experimental test phase, the test-campaigns with the new pilot plant could be optimized. [less ▲]