1,721,077 research outputs found
The rate-based modelling of CO2 removal from the flue gases of power plants
No full textRecently global warming has become a topic of great interest, involving social, economic and industrial issues. Many efforts are being made in order to limit emissions of CO2, a powerful greenhouse gas, whose massive presence in the atmosphere is increasing more and more. Industrially the most commonly used process for CO2 capture is absorption by alkanolamines, widely applied to the removal of exhaust gases from power plants. The design of the absorber is still difficult, due to the different phenomena involved. Commercially, several process simulators can be found, based on different assumptions, both for thermodynamics and for diffusion with reaction. Thermodynamics, kinetics and mass transfer greatly influence the chemical absorption process. Acid gases and amines are weak electrolytes, which partially dissociate in the aqueous phase: the high non-ideality of the liquid phase must be properly taken into account, usually with a / method. Kinetics and mass transfer can be described using two different approaches: the “equilibrium-based stage efficiency” or the “rate-based” one. This latter, if based on a proper mass transfer theory, can be used to correctly describe the phenomenon of diffusion with reaction occurring from the vapor phase to the liquid phase.
This paper focuses on modelling the absorption of CO2 by means of a piperazine solution, performed by properly modifying ASPEN Plus® with a homemade subroutine linked to the simulator. Experimental data of a pilot plant for cleaning flue gases from power plants have been used to validate the model, which well represents the absorption phenomeno
Application of CO2 Removal to Reduce Emissions in a Steel Plant
Full text linkThe steel industry is one of the major contributors to CO2 emissions due to its energy intensive processes. Steel plants operate by converting iron ore into steel through processes like the blast furnace method, resulting in substantial emissions, primarily from the combustion of fossil fuels and chemical reactions. In order to manage this challenge, Carbon Capture and Storage (CCS) technologies play a pivotal role in mitigating emissions. These technologies capture CO2 at the source and prevent it from entering the atmosphere. This work takes into consideration a French steel plant, producing 6.6 million tons of steel annually, and aims at designing the process of chemical absorption with a 30 wt.% MonoEthanolAmine (MEA) aqueous solution by optimizing it to reduce the thermal requirement for regeneration. The parameters that have been optimized are the height of the absorption column, the lean loading, the height and the pressure of the regeneration column and the temperature of the solvent entering in the regeneration column. Then, an economic analysis and the comparison of this technology with another technology for the CO2 removal, the polymeric membrane method, has been carried out in order to understand the pros and the cons also taking into account the CO2 purity and the CO2 recovery ratio that can be achieved with the two technologies
Modeling the methyldiethanolamine-piperazine scrubbing system for CO2 removal: Thermodynamic analysis
No full textRegeneration section of CO2 capture plant by MEA scrubbing with a rate-based model
Full text linkCO2 capture from exhaust gas of power plants, natural gas and refinery gas can be successfully achieved
by chemical absorption with alkanolamines. CO2 capture from exhaust gas is often obtained by absorption
with monoethanolamine (MEA) which is the most frequently used solvent for this purpose.
Our paper focuses on the regeneration section, where the amine solution is separated from the absorbed
CO2 and recirculated to the absorber. Since regeneration is obtained in a stripper or a distillation column, it
is the most energy demanding unit of the plant, so a careful modeling is required.
Thermodynamics, kinetics and mass transfer influence the chemical absorption process. Acidic gases and
amines are weak electrolytes, which partially dissociate in the aqueous phase: the high non-ideality of the
liquid phase must be properly taken into account, by employing a γ/φ method.
Kinetics and mass transfer can be described using two different approaches: the “equilibrium-based stage
efficiency” model or the “rate-based” one. ASPEN Plus® uses the rate-based model, but the prediction of
mass transfer coefficients is based on the film theory by Lewis and Whitman, while other theories can
more conveniently be used, i.e. the Eddy Diffusivity theory.
Since ASPEN Plus® simulator is suitable to be user customized, it has been chosen as framework for the
model proposed in this work, that was validated by comparing simulation results with experimental data of
a pilot plant for the purification of exhaust gas from power plant
Improved rate-based modeling of the process of CO2 capture with PZ solution
Full text linkIn recent years the interest in the development of CO2 capture technology has increased due to global warming, which is mainly due to emissions of carbon dioxide and which causes climate changes to the atmosphere and the Earth.
Commercial software packages are based on different methods for the column calculations, such as equilibrium or rate-based approaches. The commercial simulation software ASPEN Plus® has been used as a framework for the modeling, based on the rate-based approach with the Eddy diffusivity theory. The proposed model has been validated by comparison with experimental data.
An improvement in the prediction of mass transfer coefficients has been obtained by linking an external Fortran user subroutine to the software
Physical properties of PZ solution used as a solvent for CO2 removal
Full text linkThe climate change issues due to the emissions of carbon dioxide from various sources have become a challenge for many years because of the various negative effects on social, economic and environmental aspects. The most commonly applied technique is absorption by chemical solvents. Piperazine, in particular, has been used in the past as activator when mixed to other amines, such as methyldiethanolamine. Nowadays in literature also aqueous solutions containing pure piperazine are considered for CO2 capture. In this work properties such as density, viscosity and diffusivity of carbon dioxide related to this solvent have been carefully studied, taking into account the influence of carbon dioxide. New correlations have been proposed in order to best reproduce experimental data
Produzione di Idrogeno ed Energia da Biomasse in Malesia
No full textIn questo lavoro sono state studiate, mediante il simulatore commerciale Aspen
Plus® V7.2, le potenzialità di un impianto di produzione combinata di idrogeno ed
energia da biomassa. L‟impianto è in grado di produrre 10 [MWe], in accordo con
il programma SREP (Small Renewable Energy Program) promosso dal governo
della Malesia e 11.67 [kt/y] di idrogeno. L‟idrogeno è prodotto con gassificazione
in acqua supercritica (SCWG), processo di interesse per la valorizzazione delle
biomasse ad elevata umidità, mentre per produrre energia è stato scelto un ciclo
combinato. È stata effettuata l‟analisi dei costi per dimostrare la fattibilità del
processo. L‟impianto è alimentato con 280000 [t/y] di Empty Fruit Bunch (EFB),
biomassa ottenuta dalla lavorazione delle palme da olio. Come caso studio è stato
scelto il distretto di Teluk Intak nello stato del Perak (Malesia). L‟impianto è a
emissioni zero e tutti i rifiuti sono convertiti a prodotti a più alto valore aggiunto
CO2 capture in combined cycles with air-blown gasification of pre-dried high-moisture lignite
No full textThis paper deals with the energy impact of pre-combustion CO2 capture in air-blown IGCC plants when gasifying pre-dried high-moisture lignite.
An original in-house code, integrated with Aspen Plus, was used to carry out the thermodynamic IGCC assessment, which points out that a significant lignite pre-drying is necessary for higher efficiency. Considering a residual moisture in the pre-dried lignite ranging from 10 to 30 wt%, HHV efficiency presents a decreasing trend, with a maximum value slightly less than 37% for 90% of CO2 avoided, even though the higher the residual moisture in the pre-dried lignite, the lower the extraction of steam from the bottoming cycle of the IGCC plant for the water-gas shift reaction. However, introducing the specific primary energy consumption for CO2 avoided (SPECCA) as an index for the energy cost related to CO2 capture, reductions seem to be possible when gasifying pre-dried lignite with higher residual moisture. In particular, a SPECCA value as low as 2.79 MJ/kgCO2 has been calculated for the case with the highest (30 wt%) residual moisture in the lignite. Ultimately, measures for energy saving at the CO2 capture and storage plant are investigated as well
Using an Adaptive Parameter Method for Process Simulation of Nonideal Systems
No full textA thermodynamic model of the φ/φ class of methods that can be easily used with commercial process simulators
is proposed. The vapor-liquid equilibrium (VLE) is calculated by means of a Redlich-Kwong-type equation
of state (EoS) that uses modified Huron-Vidal mixing rules with activity coefficients: the activity coefficients
are derived from the NRTL model whose parameters are evaluated by fitting VLE data of binary mixtures.
By means of the Aspen PLUS process simulator, a comparison is made between the performances of both
the proposed method with user-created adaptive parameters that can be forced into the simulator database
and the Predictive-Soave-Redlich-Kwong (PSRK) method that uses UNIFAC to compute the excess free
energy. The ethanol-water separation by extractive distillation is analyzed to point out how an incorrect
prediction of the azeotrope can lead to underestimation of the overall process energy requirement
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