When solvents, such as ethanolamine (MEA), are used to capture carbon dioxide (CO₂) emissions in industrial processes, they gradually break down over time, a process called degradation. This breakdown reduces the solvent’s ability to absorb CO₂ efficiently, increases its corrosiveness, and can create harmful emissions and toxic by-products.
As the solvent degrades, it also makes the operation of CO₂ capture plants more challenging. The degradation process produces a wide variety of by-products, including heat stable salts (HSS), amides, acids, nitrosamines, volatile organic compounds, and ammonia. Some of these compounds are difficult to remove, while others can impact the performance and safety of the system.
Thermal Reclamation as a Solution
To extend the life of these solvents and reduce their degradation-related issues, a process called thermal reclamation is used. In this process, a chemical called sodium hydroxide (NaOH) is added to the degraded solvent to break down specific by-products, such as amides. This reaction helps recover useful components of the solvent, such as non-degraded amine and organic acids, while minimizing solvent loss. The solvent is then heated and distilled to remove impurities. Interestingly, some by-products, such as nitrosamines, can also break down into simpler components, like amines, at the high temperatures used in the reclamation process or even during normal operations at the plant.
Experimental Approach
This study focuses on investigating how individual degradation products of ethanolamine (MEA) behave under alkaline (basic) and high-temperature conditions. Inspired by earlier research, the process involves mixing the degraded compounds with sodium hydroxide and leaving them at room temperature for 24 hours before heating the solution to 140°C for another 24 hours.
The composition of the solution is analyzed before and after treatment using a technique called liquid chromatography-mass spectrometry (LCMS), which identifies and measures the chemicals present. These experiments are being conducted on both fresh MEA—an unused, clean solution—and degraded MEA, which has been broken down using the SINTEF cyclic solvent degradation rig, a laboratory setup that mimics real-world plant conditions. This approach allows researchers to study a wider variety of degradation products, including complex ones that form over time in CO₂ capture plants.
Expected Results
The researchers expect to observe an increase in the concentration of recovered MEA, a decrease in the concentration of amides, and the formation of organic acids as by-products. These results will provide insight into the chemical reactions that occur during thermal reclamation and help optimize the process for extending solvent life.
Future Work on CESAR1 Solvent
Once this behavior is well understood for MEA, the team plans to perform similar experiments on a newer solvent called CESAR1. However, before doing so, they will need to further study CESAR1’s degradation behavior and refine analytical techniques to identify its breakdown products accurately.
Understanding how solvents degrade and how they can be efficiently reclaimed is crucial for improving CO₂ capture technologies. By extending the lifespan of solvents, researchers can reduce the costs and environmental impacts of these processes while ensuring cleaner and safer plant operations. This work contributes to the development of more sustainable and efficient CO₂ capture systems, which play a key role in reducing greenhouse gas emissions.
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