Abstract :
[en] Since the beginning of the 21st century, the effects of global warming have been more and more visible, especially through extreme climate phenomena. Anthropogenic emissions of greenhouse gases (especially carbon dioxide) have been identified as the main responsible for such climate change. Among the numerous studied technologies to decrease CO2 emissions, the absorption-regeneration process is the most developed at industrial level. However, the main inconvenience of such a process is its high demand for thermal energy. The solvent used for the CO2 absorption is an important parameter of the process and its choice is a key factor to reduce that required heat. Among the available solvent blends, the demixing solvents allow to reduce the flow needed to be regenerated. Simultaneously, this stream is more concentrated in carbon dioxide. Both contribute to reducing the regeneration energy which causes the highest operational costs of the absorption-regeneration process. For various reasons (e.g., production costs for ionic liquids, unknown water tolerance for water-lean solvents), only aqueous liquid-liquid amine-based mixtures are considered for this evaluation methodology. 30 different blends were identified through a literature review as potential candidates for further possible development. These blends are made of 23 organic compounds in different compositions and/or proportions. 12 of them are ternary blends composed of water and two amine-based molecules. The other mixtures contain a phase-splitter agent in addition to water and amine(s). These chemicals, used to induce or enhance the demixing behavior, are mainly sulfolane and alcohols. The evaluation methodology is composed of two successive steps. The first step is a techno-economic evaluation to classify the reviewed solvents. This evaluation is based on six indicators. The main one remains the regeneration energy as it is the parameter that should be reduced. CO2 absorption capacity and CO2 absorption rate are also considered for the thermodynamic and kinetic aspects. The demixing phenomenon is included in the evaluation through the demixing volume ratio. The two last indicators are the volatility of organic compounds (as it can have impacts on the process design) and the solvent cost (which is the only economic-exclusive criterion). The contributions of these six indicators are weighted using the analytical hierarchy process method and finally give a classification of the 30 identified blends. Among them, 17 solvents are excluded due to the health, safety, and environmental analysis (second step). Indeed, these blends contain at least one compound that presents a serious hazard (mortal hazard, serious fertility danger, corrosivity, high toxicity to aquatic life). Finally, 13 aqueous liquid-liquid biphasic amine-based blends remain and are classified through their score owned after the first step of the evaluation method. The aqueous solvents ranked from the 5th to the 2nd place are composed of two amine molecules. One contains primary/secondary amino groups (MEA, MAPA, TETA) while the other contains a tertiary amino group (DEEA, DMCA). Nevertheless, among the reviewed aqueous blends, the most promising demixing solvent is composed of triethylenetetramine (30 wt.%) and propan-1-ol (50 wt.%).
