Evaluation of new solvents to capture CO2: Modelling and validation of the regeneration column in industrial and pilot plants

The Intergovernmental Panel on Climate Change (IPCC) Working Group I warns in its sixth Assessment Report delivered in August 2021 that global warming will reach 1.5°C in a couple of decades even in a best-case scenario of deep cuts of greenhouse gas emissions. However, it states that climate change stabilization is still in human hands should “immediate, rapid, and large-scale reductions” in emissions take place. And it is clear that carbon capture and storage is a crucial mitigation measure to meet net zero emission targets and act as a deterrent against this universal environmental crisis notably following IPCC’s special report on climate change. Carbon capture is also currently attracting attention due to the potential that CO2 has as a: - Enhanced Oil Recovery (EOR) instrument: where CO2 injection into an oil well reduces the density of the oil and increases the well productivity - One-carbon (C1) building block in organic synthesis; where CO2 is recyclable, creating thus a circular carbon economy. Moreover, due to an increasing world population and thus a growing energy demand, natural gas plays a major role in the energy transition since it is less polluting than other fossil fuels and cheaper than emerging renewable technologies. A big proportion of the world’s natural gas reserves is acid; as they contain carbon dioxide CO2 and hydrogen sulfide H2S. These compounds must be separated from the gas before it is marketed for several reasons: H2S is toxic even at very low levels, CO2 accounts for most greenhouse gas emissions , CO2 can crystallize and form hydrates, clogging the pipes, CO2 reduces the calorific value of the gas, CO2 and H2S are acidic and corrosive Carbon Capture consists thus on applying pre and post-combustion technologies to capture CO2 from natural and flue gas streams. Industrially, absorption into a liquid solvent is considered to be the most advanced approach to capture the acid components and thus ‘sweeten’ the natural gas. Amine scrubbing has been used since 1930. However, this technique still faces commercialization problems notably due its the high energy penalty and extensive equipment size. Desired solvents characteristics are mainly: High absorption capacity, high mass transfer and chemical kinetics, low degradation tendency, and low cost. DEA, MEA and MDEA are examples of solvents that were extensively studied in the previous decades. However, new solvents are required to minimize the energy requirement of the acid gas sweetening unit, and to obtain task-specific absorption. The R&D ‘CO2 natif’ team at ToalEnergies, in its quest to evaluate new solvents that could be of economic benefits to its clients, develops thermodynamic, kinetic and mass transfer models which are inserted in a process simulation tool (Aspen Plus) of an acid gas removal unit. Using this tool, the team aims to ultimately evaluate the performance of the new solvents under industrial conditions. TotalEnergies operates in parallel an acid gas absorption/regeneration pilot plant that produces a number test runs to optimize the process. The results of the simulations are naturally compared then to CO2 absorption-regeneration pilot test results to validate and optimize the Aspen simulations. The work carried in this internship comes after preliminary simulations of absorption and regeneration columns where problems with this column were found .Thus, the following work comes as a detailed study of the regeneration model in Aspen Plus.