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 30-60atm and 303-333K, respectively, and they are 30-60atm and 240-270K 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.