Co-Cap: Collaboration on Commercial Capture (Flexible Funding 2020)

An open-technology and open-access post-combustion capture initiative – Professor Jon Gibbins, Director, UK CCS Research Centre and Professor of CCS, University of Sheffield; and Dr Stavros Michailos, Researcher Co-Investigator, University of Sheffield (now Lecturer, University of Hull)

Post-combustion CO2 capture (PCC) plants are the basis for the majority of projects in the current wave of UK CCS deployment.  Applications actively being considered include gas-fired and biomass power plants, energy-from-waste plants, refineries and steam-methane reformer retrofits.  PCC plants are also widely applicable globally, particularly for retrofit applications.

This proposal addressed two issues:

  1. Knowledge-sharing for cost reduction
  2. Residual CO2 emissions from PCC plants in the context of net-zero

The delivery of the objectives of this project was enhanced by a number of subsequent open-access projects that it facilitated.  The following non-experimental projects are completed:

Related experimental projects are still ongoing:

Delivery of the project objectives was started by early workshops, as envisaged in the proposal, and then continued through stakeholder engagement on the BAT review, a number of conference presentations, an open-access journal peer-reviewed paper and updates on the project web page.  A list is given at the end of this blog.  This amounted to more material and engagement than anticipated in the proposal, due to assistance by the unforeseen related projects, and activity was extended over a considerably longer period than originally envisaged.  The project also helped to get a new detailed engineering study for an amine capture plant made available on the UKCCSRC web site and publicised to potential users.

In addition to high levels of CO2 capture from combustion flue gases, the research outcomes also suggested a way to reduce the regeneration energy penalty for CO2 capture from air using amines.  This has resulted in a new UKCCSRC project with co-investigator Stavros Michailos as PI, Co-DAC: Low-energy Direct Air Capture potential when combined with a Post Combustion Capture plant, with the concept described in a GHGT-16 presentation/paper  Stavros Michailos has also progressed to a new position as Lecturer at the University of Hull.

As a result of computer modelling in this project, a clear theoretical understanding has been gained of how PCC plant operating parameters can be adjusted to achieve high levels of CO2 capture and the factors that determine the amount of heat required when doing so.  In general, previous studies have not undertaken an holistic analysis and have therefore concluded that there are greater barriers to achieving high capture levels than, in fact, exist – the problems they encountered being due to pre-selection of operating parameters such as stripper pressure or absorber liquid/gas ratio.

An outline illustration of a PCC plant is shown below.  This project modelled the performance of such a plant using a non-proprietary capture solvent, a solution of 35% w/w monoethanolamine (MEA) in water.

One key finding was that lean solvent loadings of ~0.1 mol CO2/mol MEA are required to achieve high capture levels (95-99%) in the absorber.  This is not a surprising result as the leaner a solvent is, the more aggressively it will remove CO2 from a gas mixture.  The problem is how to produce this low lean loading without requiring excessive energy.  Previous studies, using a fixed stripper pressure, have concluded that a lot of energy would be required but we were able to show that, provided the pressure in the stripper/reboiler was high enough, the amount of heat required per tonne of CO2 captured would not go up.  The high pressure is important to suppress wasteful water vapour production in the reboiler; some water vapour is essential to ‘strip’ the CO2 from the solvent when it is heated, but a lot of heat is required to produce it.

It was also found that a high rich loading in the solvent leaving the absorber was essential to minimise heat demand in the stripper/reboiler; not doing so means that ‘unused’ solvent is being circulated and heated and also involves more water vapour being emitted from the stripper with the CO2.  High solvent rich loadings require that enough packing is available in the absorber to transfer enough CO2 from the flue gas to the solvent.  Up to 24 m of packing height was found necessary to capture the 99% of the CO2 in the flue gas from a gas turbine that comes from the burnt fuel, leaving only the 1% that came from the air going into it.  But this study emphasised that the solvent flow through the absorber is also critical: too low and it is insufficient to capture the CO2, too high and the CO2 is captured but the rich loading will be lower than the optimum value.

Work is now ongoing to test these theoretical findings on the amine capture pilot plant at the University of Sheffield’s Translational Energy Research Centre (, shown below, at a scale of around 1 tonne of CO2 capture per day.

TERC Carbon capture plant


Project outputs

17 June 2020Open-access PCC meeting (D1), 15 attendees, including from AECOM, Bechtel, BP, SSE, Tata Chemicals, VPI.  Karsto FEED study documents formed the basis of discussion, these were made available on the UKCCSRC web site here (D2, D5)
14 Sept 2020Open-access PCC workshop, 16 attendees, including from AECOM, Bechtel, BEIS, BP, Petrofac, SSE, Tata Chemicals, VPI.  Sherman FEED study documents formed the basis of discussion, these were subsequently made available on the UKCCSRC web site here (D4, D5)
March 2021GHGT-15 presentation and paper:

Elliott, William and Benz, August and Gibbins, Jon and Michailos, Stavros, An Open-Access, Detailed Description of Post-Combustion CO2 Capture Plant (March 29, 2021). Available at SSRN:  or

1 July 2021UKCCSRC web series update – recorded presentation (D3)
Oct 2021PCCC6 presentation:

Elliott, William, Benz, August, Curtis, Martin, Gibbins, Jon and Michailos, Stavros An open-access, detailed description of a post-combustion CO2 capture plant retrofit for Panda Energy’s Sherman combined cycle power plant

Oct 2021PCCC6 presentation:

Michailos, Stavros and Gibbins, Jon, Process modelling assessment of modifications to a detailed commercial PCC design using 35% MEA to achieve 95%+ capture levels, plus estimated cost and revenue implications

24 May 2022Peer-reviewed paper:

Michailos, Stavros and Gibbins,  Jon (2022) Modelling Study of Post-Combustion Capture Plant Process Conditions to Facilitate 95–99% CO2 Capture Levels From Gas Turbine Flue Gases, Frontiers in Energy Research, 10, 2022.   DOI=10.3389/fenrg.2022.866838

7 July 2022Summer 2022 update (presentation to web page)
Oct 2022GHGT-16 presentation and paper:

Michailos, Stavros and Samson, Abby and Lucquiaud, Mathieu and Gibbins, Jon, A performance modelling study of integrating a MEA direct air capture unit with a CCGT absorber (November 22, 2022). Available at SSRN:  or

Oct 2022GHGT-16 poster and paper:

Michailos, Stavros and Gibbins, Jon, Effect of stripper pressure and low lean loadings on the performance of a PCC plant for 99% CO2 capture level (November 22, 2022). Available at SSRN:  or

Oct 2022GHGT-16 presentation and paper:

Elliott, William and Benz, August and Gibbins, Jon and Michailos, Stavros, An open-access FEED study for a post-combustion CO2 capture plant retrofit to a CCGT (August 29, 2022). Available at SSRN:  or