(712c) Comparison of Ammonia, MonoEthanolAmine and MethylDiEthanolAmine Solvents to Capture CO2

Current and future developments in world economies are closely connected to sustainable development that may lead to sustainable societies by means of the efficient, safe usage of raw materials and lower emissions of CO2. Several techniques have been proposed to reduce the emission of CO2 into the atmosphere. Among these techniques, chemical solvent absorption methods have been extensively studied and are considered as a reliable and relatively competitive method for reducing carbon dioxide emissions from fossil fuel power plants. The MEA scrubbing is so far the most acceptable chemical solvent method to react with CO2. However, its low absorption capacity, easily degradation and higher energy requirement suggest that future research efforts should be directed toward developing better solvents for removal of CO2. Ammonia seems to be an alternative solvent for removing CO2 from flue gases; it has already been used in the DeNOx process such as selective catalytic reduction and selective non-catalytic reduction in the flue gas systems. The scrub of all acid pollutants in flue gases, including the CO2, may be possible using the ammonia. However, limited information on its technical and economical effectiveness is available.

This work presents a comparison of CO2 absorption by ammonia solvent in terms of kinetics, absorption capacity and heat duty with respect to more traditional alkanolamines solvents, such as monoethanolamine (MEA) and methyldiethanolamine (MDEA). Ammonia has the advantage over amines respecting high absorption capacity, oxidative resistance and thermal degradation. However, ammonia losses can be large due to its high vapor pressure. Experiments are carried out in a thermoregulated Lewis-type cell reactor in temperatures ranging from 278 to 303 K and mass concentrations from 2 wt% to 5 wt%. Furthermore, the CO2 capture is simulated with the software Aspen plus? for a pulverised coal fired power plant (CF). The results show that carbon dioxide absorption by ammonia is faster than that carried out by MDEA and blend amines (MDEA MEA), while MEA is the most reactive solvent studied. With regard to post-combustion, the process simulation shows that the heat duty for NH3 is lower than this of MEA and MDEA. The energy consumption reaches 2.83 GJ/tCO2. Regarding kinetics reaction, heat duty and ammonia losses, 3 wt% NH3 is the suitable concentration to capture CO2.