• 0 Coal and gas fired power plants are the main contributors of CO2 emissions. CAPSOL technology offers a competitive solution for the efficient post-combustion CO2 capture. (Public Power Corporation, Agios Dimitrios Power Plant)…
  • 1 CAPSOL incorporates state-of-the-art thermodynamic property prediction and Computer Aided Molecular Design for advanced solvents and blends. (Source : Imperial College - London)…
  • 2 CAPSOL technology utilizes multi-level design and selection of validated solvent-process schemes with optimum economic and controllability features. (Papadopoulos A.I., and P. Seferlis, “A framework for solvent selection based on optimum separation process design and controllability properties”,Computer Aided Chemical Engineering, 26, 177-182, 2009.)…
  • 3 CAPSOL aims at optimum design of absorption/desorption equipment and column internals through advanced modelling and experimentation (Kenig, E.Y. (2008), Chem. Eng. Res. Des. 86, Part A, 1059–1072)…
  • 4 CAPSOL aims at sustainable CO2 capture technology through the Environmental Performance Strategy Map (De Benedetto L., Klemeš J., 2009. J. Clean. Prod., 17(10), 900-906)…
  • 5 CAPSOL targets plant level (resources) integration of CO2 emitting and capture plants through total-site and plant-wide optimization analysis (Varbanov, P., Perry, S., Klemeš J.,Smith, R., (2005), Applied Thermal Engineering, 25, 985-1001)…

CAPSOL design optimization framework enables the reduction of annualized costs by 30%


The design of CO2 capture flowsheets requires that:

  1. Multiple structural and operating parameters acting as decision variables must be considered to identify highly performing configurations.
  2. Process models that describe the highly non-ideal characteristics of the solvent-CO2-water mixtures and the unit operation phenomena must by employed.

Flowsheet development

The first requirement is served by a process synthesis approach that combines generic representations of process layouts, called superstructures, with an optimization algorithm to systematically investigate an extensive range of structural and operating process options.

The proposed superstructure consists of modules representing generic process tasks (e.g. reactive, separation, reactive separation, heat transfer) and interconnecting streams emulating material flows. Each module may be independently assigned with a process model representing a particular task, the type of equipment utilized, the desired operating conditions and so forth. The proposed tasks account for (a) reaction, mass and heat exchange options between different phases within each module, and (b) stream mixing and splitting options to enable distribution of materials among different modules. Modules may be connected to each other thus forming a network of tasks serving the purpose of the entire flowsheet.

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 Solvent based CO2 capture process superstructure.



Column modeling

Orthogonal collocation on finite elements (OCFE) techniques provide an efficient model order reduction procedure for the separation process tasks. Column concentration and temperature profiles are approximated by polynomials of lower order than the actual stages they represent. The material and energy balances are satisfied exactly only at the roots of a certain family of orthogonal polynomials. Multiple finite elements may used to describe a column section with varying profiles. The main advantage of the OCFE model formulation is the flexible nature of the column section height and hence the separation capacity associated with the given column section.

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Model reduction concept for packed column sections using the OCFE technique.


Representation of various flowsheet configurations using separation/reaction modules, heat exchanger modules, splitters and mixers enables the efficient process design optimization. Decision variables are the column section heights in both the absorber and the stripper, the heat exchanger areas (both for the feed effluent heat exchanger and the intercooler heat exchangers, the lean amine stream flowrate, the target temperatures in the heat exchangers (flowrates of the cooling medium), the column pressures, and the reboiler duty.

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(A) Intercooled Absorber configuration, (B) Superstructure/OCFE equivalent.


The intercooled absorber flowsheet exhibits an improved performance.





Lean loading



Total Equivalent Stages








Reboiler Duty (kW)



Reboiler Temperature (K)



Exchanger Area (m2)



Solvent Flow (mol/s)



Absorber Pressure (kPa)

Stripper Pressure (kPa)



202.6 184.57

Split Ratio (%)



Objective function value



Damartzis T., A. I. Papadopoulos, and P. Seferlis, “Optimum Synthesis
of Solvent-Based Post-Combustion CO2 Capture Flowsheets through a
Generalized Modeling Framework”, Clean Technologies and Environmental
Policy, 16(7), 1363-1380, 2014.
DOI 10.1007/s10098-014-0747-2