Climate change affects us all. Many of our projects are concerned with “climate-neutral” energy provision with the aim of reducing CO₂ emissions . According to the Intergovernmental Panel on Climate Change (IPCC), the 1.5°C target of the Paris Agreement cannot be achieved solely through measures to reduce CO₂ emissions; it also requires “negative” CO₂ emissions to be achieved.
The CONENGA Group has been dedicated to the former for many years with great success (Magnes-IT, decarbonization, process engineering innovations,…) But we are also working intensively on the second point, which has only become more concrete in recent years, in the area of innovative CO₂ capture options, also known as “Carbon Capture” (CC). This refers to the technical separation of carbon dioxide from exhaust gas streams before it is released into the atmosphere.
Why carbon capture?
The natural carbon cycle, in which CO₂ sources and CO₂ sinks (reservoirs) are balanced, is thrown out of balance by human-induced carbon dioxide emissions. The excess CO₂ is mainly produced during the thermal conversion (combustion) of fossil and biogenic organic fuels, but also during biotechnological processes such as bioethanol production.
This imbalance increases the atmospheric CO₂ content. As a greenhouse gas, CO₂ indirectly causes the earth’s temperature to rise, as the heat radiation reflected from the ground can no longer escape sufficiently from the atmosphere.
However, energy plants that produce heat and electrical energy are still needed. This is why CO₂ capture (CC) comes into play: carbon dioxide can be captured from the flue gases of heating plants to minimize further greenhouse gas emissions in the atmosphere.
Goal: Carbon capture should release as little CO₂ as possible directly into the atmosphere
As the CONENGA Group, we are currently focusing primarily on the topic of carbon capture and utilization / storage in biogenic-fired plants. Various technologies are being considered for this purpose.
Carbon capture technology overview
Various processes at different stages of development are available for CO₂ capture from flue gases.
- In the pre-combustion process, the CO₂ is separated before the actual combustion, but the fuel must first be converted into synthetic gas.
- In oxy-combustion, the fuel is burned with almost pure oxygen instead of air.
- In post-combustion processes, the fuel is burned normally and the CO₂ contained in the exhaust gas is then filtered out.
Post-combustion separation technology is particularly relevant for existing systems, as it can be applied after the combustion process and can be retrofitted. Accordingly, this process is also the most relevant for the needs of our existing customers.
Post-combustion in detail
In the case of CO₂ capture from flue gas, this process is used because the technologies can be adapted and retrofitted to most incineration plants. As CONENGA Group, we check the basic requirements and parameters for the best separation efficiency for plant operators and then evaluate which technology is best suited for the respective site.
Technologies used:
- CO₂ absorption (Amine scrubbing)
Amine scrubbing is the best known and most established process for separating CO₂ from flue gas. Amines react with the CO₂ to form water-soluble components and are thus separated from the flue gas.
Process flow diagram of a typical system for amine washing
As shown in the illustration, the plant primarily consists of two units – the absorber, where CO₂ is absorbed from the acidic exhaust gas, and the stripper, where the CO₂ is desorbedat higher pressures and temperatures and then compressed for further use. The advantage of the amine scrubbing technology is the already mature technology maturity and the high separation rate, the disadvantage is the high energy requirement for this technology to achieve high purity levels. [1], [2], [3]
- CO₂ adsorption (Temperature Swing Absorption)
Temperature Swing Absorption (TSA process) is another technology that we at the CONENGA Group are working intensively on. This involves the chemisorption or physisorption of carbon dioxide on solids. This requires highly selective sorbents.
The following figure shows the main material flows of a multi-stage TSA fluidized bed system consisting of two units as an example of an adsorption process. In the adsorber (left), the carbon dioxide accumulates on the particles, which are then blown into the desorber (right). There, the CO₂ is desorbed at high temperatures with process steam and then processed further. [4]
Block diagram showing the main material flows of a multi-stage TSA fluidized bed system for CO₂ separation from the flue gas.
Adsorption processes can be implemented not only as TSA, but also as PSA (Pressure Swing Adsorption) or as a combination of both technologies. Furthermore, the technology can be designed not only as a fluidized bed reactor but also as a fixed bed reactor. [5], [6]
Status Quo
The degree of maturity for adsorption technologies in CO₂ capture applications has not yet reached the industrial standard. However, the technologies, especially TSA, are promising in terms of achieving high degrees of purity and comparatively low energy consumption. [4]
We are therefore pursuing this concept intensively in research projects in order to be able to provide this practical technology to our customers with fulfilled site requirements.
About the author:
Our colleague Sabrina Kröhnert gives us a compact insight into research and practice at the CONENGA Group: As part of the FFG-funded Biofizz research project, she has been working on the topic of CO₂ capture (carbon capture, CC) and has also dedicated her master’s thesis to this subject.
Sabrina Kröhnert
CONENGA Group
Sources:
[1] J. D. Figueroa, T. Fout, S. Plasynski, H. McIlvried, and R. D. Srivastava, “Advances in CO2 capture technology-The U.S. Department of Energy’s Carbon Sequestration Program,” Int. J. Greenh. Gas Control, vol. 2, no. 1, pp. 9-20, Jan. 2008, doi: 10.1016/S1750-5836(07)00094-1.
[2] Y.-D. Hsiao and C.-T. Chang, “Efficient multi-objective optimization and operational analysis of amine scrubbing CO2 capture process with artificial neural network”, Int. J. Greenh. Gas Con-trol, vol. 138, pp. 104242, Oct. 2024, doi: 10.1016/j.ijggc.2024.104242.
[3] E. Pancione, A. Erto, F. Di Natale, A. Lancia, and M. Balsamo, “A comprehensive review of post-combustion CO2 capture technologies for applications in the maritime sector: A focus on adsorbent materials”, J. CO2 Util, vol. 89, pp. 102955, Nov. 2024, doi: 10.1016/j.jcou.2024.102955.
[4] F. Zerobin and T. Pröll, “Concentrated Carbon Dioxide (CO2 ) from Diluted Sources through Continuous Temperature Swing Adsorption (TSA)”, Ind. Eng. Chem. Res., vol. 59, no. 19, pp. 9207-9214, May 2020, doi: 10.1021/acs.iecr.9b06177.
[5] H. Si et al, “Analysis on temperature vacuum swing adsorption from wet flue gas carbon cap-ture by using solid amine adsorbent with co-adsorption equilibrium models”, Fuel, vol. 380, pp. 133171, Jan. 2025, doi: 10.1016/j.fuel.2024.133171.
[6] P. A. Webley, A. Qader, A. Ntiamoah, J. Ling, P. Xiao, and Y. Zhai, “A New Multi-bed Vacuum Swing Adsorption Cycle for CO2 Capture from Flue Gas Streams,” Energy Procedia, vol. 114, pp. 2467-2480, July 2017, doi: 10.1016/j.egypro.2017.03.1398.