Effect of Solvent Composition on Solvent Properties of Non-Aqueous and Low Aqueous Solvents

Abstract

The high amounts of CO2 emissions can be minimized by applying Carbon Capture and Storage (CCS) technology. Chemical absorption with amines, or amine scrubbing, is one of the available technologies. In this technology, a solution with amines is used to capture the CO2. The main disadvantage of amine scrubbing is the high heats of absorption obtained, leading into high regeneration costs of the solvent. A trade-off between a low heat of absorption and a high capacity of absorption is then desired and hybrid solvents, which are mixtures of organic solvents and amines with a low content of water or directly without it, have a potential capacity for providing this good trade-off. In this work, different solutions of hybrid solvents were prepared and run in a calorimeter, and VLE curves and heats of absorption were obtained. Aqueous solutions were also run to compare the results between them and the organic mixtures. The organic solvents used were NMP (1-Methyl-2-Pyrrolidinone) and MEG (Ethylene glycol), while the amines used were DIPA (Diisopropylamine) and DEEA (2-(Diethylamino)-Ethanol). Experiments showed that organic mixtures had lower heats of absorption than the aqueous ones, and the best results in terms of the trade-off between the heat of absorption and the capacity were those where MEG was used as a diluent. Other three experiments were run in a string of discs to study the kinetics, and the overall mass transfer coefficients were obtained. Chemicals used in the string of discs were MEA (Ethanolamine) and MEG (Ethylene glycol). Finally, samples were taken from the loaded solutions, and the CO2 and amine contents were analysed on a TOC-L (Total Organic Carbon analyser) and a titrator.