Carbon dioxide capture by single droplet using Selexol, Rectisol and water as absorbents: A theoretical approach

A theoretical method is developed to analyze carbon dioxide capture by a stationary single droplet for evaluating the fundamental mass transfer behavior. In the method, the gas-phase diffusion is predicted using a similarity method and the technique of separation of variable is employed to approach the liquid-phase diffusion. At the interface, a finite difference method is applied to connect the CO2 diffusion between the two phases. The individual capture processes of CO2 by three different absorbents of Selexol, Rectisol and water, are taken into account. The operating pressure and temperature of Selexol and water are in the ranges of 30-60 atm and 303-333 K, respectively, and they are 30-60 atm and 240-270 K for Rectisol. The analysis indicates that an increase in temperature decreases the CO2 capture amount and absorption time by Selexol and Rectisol droplets. The absorption time is more sensitive to the operating temperature than the capture amount. As a result, the CO2 absorption rates by the droplets are increased when the temperature increases. Among the three absorbents, Rectisol has the highest capacity to capture CO2 and its absorption time is in a comparable state to the other two absorbents. This results in that its absorption rate is larger than the others by an order of magnitude.