Dr Charithea Charalambous is a research associate in the Research Centre for Carbon Solutions (RCCS) and the UK Industrial Decarbonisation Research and Innovation Centre (IDRIC) at Heriot-Watt University. Charithea was awarded with the UKCCSRC ECR Collaboration Fund Award to travel to the Norwegian University of Science and Technology (NTNU) in Trondheim to collect essential vapor-liquid equilibrium data of different amine solutions that are currently lacking in literature.
Here is what Charithea shares about her recent trip to Norway:
What was the aim for your collaboration?
My collaboration aimed to improve the economics and to de-risk large-scale development of Post-combustion Carbon Capture (PCC) processes by providing essential vapor-liquid equilibrium (VLE) data, which is currently lacking, for aqueous solutions of amines. This data is key to developing a rigorous design of water wash systems in amine-based carbon capture technologies aiming to reducing solvent emissions to the atmosphere.
In terms of challenges you hoped to address, why did you choose your particular collaboration partner? What key problems did you hope to overcome prior to the collaboration/research, or ideas you wanted to prove?
This work is a collaboration between the Research Centre for Carbon Solutions (RCCS) at Heriot-Watt University (HWU), the Norwegian University of Science and Technology (NTNU), and the independent research organisation SINTEF industry. The experiments were performed using existing equipment at the Department of Chemical Engineering at NTNU and the Department of Process Technology at SINTEF industry. The two research groups have a close collaboration and are working together in several projects. The absorption laboratories at the Department of Chemical Engineering at NTNU are part of the European Carbon Dioxide Capture and Storage Laboratory Infrastructure. Their team has significant experience measuring vapour-liquid equilibria for CO2 capture and have produced many publications using the VLE-equipment at NTNU and SINTEF industry.
Vapour-liquid equilibria are fundamental properties for the accurate design and simulation of any separation processes. The data is required for process modelling and simulations of nonideal liquid systems, like aqueous amines. However, there is a lack of experimental VLE data at low amine concentrations recorded in the washing sections of the PCC systems. The integration of advanced washing systems, like water wash systems, in amine-based PCC processes can provide a significant reduction in, or even elimination of, amine emissions to the atmosphere. As a consequence, washing systems can reduce the environmental impact and energy requirement of the carbon capture process, making PCC systems economically viable.
Regardless, existing models are used which do not make use of this critical data, leading to inaccurate predictions in the solvent losses to atmosphere, the extent of amine degradation, and consequently the inaccurate performance of the capture plant.
Obtaining these VLE data at very low concentrations of amines requires conditions of low vacuum pressure (especially at low temperatures), which are challenging to measure. A modified Swietoslawski ebulliometer was used to measure the volatility of aqueous amines at low concentrations when CO2 is not present. Analytical methods used vary from simple titration to LC-MS methods to quantify the amines in the liquid and in the gas phase (volatility). NTNU and SINTEF industry provided all required equipment and analytical capabilities.
Any previous research that you were building on (either successful or unsuccessful)? What were your key decision points and how did you approach these decisions? What would happen if no solution to the problem was found?
To make the PCC process economically viable, the energy requirement and environmental impact of the process must be reduced, while maintaining optimal CO2 recovery. The most well-known and broadly used amine in carbon capture systems is monoethanolamine (MEA) due to its low chemical cost, fast reaction rate and high capacity to capture CO2 even at CO2 low partial pressures. However, this solvent is moderately volatile and a significant amount of energy is required to regenerate the CO2 rich solvent in the stripper column. Therefore, interest has recently grown in mixing alkanolamines to reduce energy, solvent losses and solvent degradation.
2-Amino-2-Methyl-1-Propanol (AMP) and Piperazine (Pz) mixtures merge useful properties from both amines. AMP has a higher CO2 loading capacity and can be regenerated at lower temperatures than MEA. Pz, a diamine, effectively promotes rapid formation of carbamates and can theoretically absorb two moles of CO2 per mole of amine. Adding Pz to AMP is reported to be an energy and material saving alternative to conventional MEA-based solvents for the PCC process. The AMP/Pz mixture has been considered as the new benchmark for liquid-based capture systems (e.g. European ERA-ACT project ALIGN-CCUS and the EU project in the 7th framework program CAESAR).
Part of my work in RCCS was to lead the team’s activities on process modelling and experimental work in the ALIGN-CCUS project. The proposed experimental work was a following up study of the ALIGN-CCUS project as the AMP/Pz mixture was used as one of the long-testing solvents in the four European capture pilot plants participating in the ALIGN-CCUS project. These pilot plants were: (i) the pilot plant at Niederaussem (DE), (ii) the capture plant at Technology Centre Mongstad (NOR), (iii) the pilot rig at Tiller (NOR), and (iv) the PACT facilities at Sheffield (UK). This project is also relevant to newly funded ACT projects, such as the LAUNCH and SCOPE projects, which focuses on AMP/Pz degradation and integration of advance amine emission control strategies, respectively. These two projects are following ones from ALIGN-CCUS trying to address the new scientific and technical questions arose towards the completion of that project. A better understanding and prediction of volatile emissions are one of those questions.
The RCCS team, including myself, is also part of the SCOPE project and the obtained data will be valuable for achieving some of the main objectives of SCOPE. Besides, the VLE experimental data will be soon accessible to all the member of the CCS community through a publication. This will hopefully help the CCS community to improve the economic predictions of large-scale PCC systems.
Now, more about those findings: what did you discover? Any outputs you can share?
Although it was challenging to obtain these VLE data at low temperature and pressure ranges, I was able to obtain it for most of the tested solutions. An abstract has been submitted to the GHGT-16 conference and a publication is expected to follow.
Let’s talk about the impact of your results: why was this collaboration the right choice for you and your research? What did the partner institution get out of it?
I trained with specialist NTNU and SINTEF industry researchers on how to use the laboratory apparatuses for the VLE measurements and several techniques / methods to analyse the samples. The Environmental and Reactor Technology group at NTNU and the Department of Process Technology at SINTEF industry offer advanced systems for measuring VLE data and advanced techniques for sampling analysis. I obtained an exclusive knowledge on how to collect accurate VLE data of aqueous solvents from two of the leading laboratories focused on chemical absorption in EU.
I also had access to additional specific expertise, was exposed to a different research environment, gained new perspectives on research and built relationships with the collaborating institution and the research organisation. Both NTNU and SINTEF are leaders in the field of aqueous-based carbon capture technologies, which can be key to my career development in CCS.
Apart from being trained on new tools and obtaining valuable experimental data, I tried to build bridges for future collaboration between the RCCS of Heriot-Watt University and the Environmental and Reactor Technology group at NTNU. Both groups are part of SCOPE and this work will be continue in the next coming years!
How do you think your work will advance CCS research and implementation? Does it have impact for industry?
The UK government has set a target to become the first major economy to bring all greenhouse gas emissions to net zero by 2050 (2045 for Scotland). Meeting this challenging target will require radical changes including the complete decarbonisation of the energy and the industrial sectors. CCUS is anticipated to have a significant mitigation role especially in the decarbonisation of industrial zones. This work will provide measurable improvements in the environmental performance of PCC plants helping in the acceleration of their development. The work will be significantly important to tailor scale-up and integration of cost-effective amine emissions control systems.
More specifically, individuals and institutions who work on amine-based PCC systems will benefit from access to the missing VLE data at low concentrations of amines, as it will allow them to develop and design more accurate systems. This visit will also help to decrease the uncertainty between real data and the results from process modelling. This will substantially improve the economics of capture systems at large-scale development and accelerate the industrial R&D of CCS. This is expected to benefit all the members of the CCS community by increasing the awareness and confidence for investors and other stakeholders.
Closing up, I would like thank all my funders, UKCCSRC, ALIGN-CCUS project, RCCS, and the absorption labs of NTNU for making this trip possible.
My gratitude goes to Prof Hanna Knuutila and Dr Ardi Hartono of NTNU for hosting me in their research group and patiently guide me through the experiments during this collaboration. I would like to thank all my colleagues at NTNU for our great discussions during lunch and cake breaks, over dinner at a local brewery, in group meetings, corridors, offices and labs.
My gratitude also goes to the members of SINTEF industry that welcome me in their labs and help me with the apparatus and sample analysis.
Last but not least, I thank my line manager and mentor, Prof Susana Garcia at Heriot-Watt University, for providing continuous guidance and supporting my participation to this work.