The removal of carbon dioxide from process gas streams is an important step in many industrial processes for a number of technical, economical or environmental reasons. In the presence of water, CO 2 - being an acid gas – can cause corrosion to process equipment. Besides this, the presence of CO 2 reduces the heating value of a natural gas stream and also wastes valuable pipeline capacity. The conventional technology to capture CO 2 on large scale is the absorption- desorption process, in which (aqueous) solutions of alkanolamines are frequently used as solvents. Nowadays, the addition of an activator or more specifically piperazine (PZ) to an aqueous N-methyldiethanolamine (MDEA) solution has found widespread application in the bulk removal of carbon dioxide. More generally, the localization of the mass transfer resistance to the interfacial region presents a problem in the intensification of most multiphase contacting processes in the chemical and biochemical industries, since effective strategies have to work in this micronthin region. Conventional methods for improving the rate, which rely on intensifying mixing or turbulence in the bulk of the phase or phases involved, therefore have inherent limitations. Thus in recent years there has had been some interest in the potential of nanofluids to influence mass transfer rates. In this work absorption of carbon dioxide into an aqueous MDEA+ PZ+H 2 O was investigated in a stirred vessel at 101.3 kPa to measure the absorption rate and volumetric mass transfer coefficient of CO 2 . Effect of different parameters such as temperature, gas flow rate, amine concentration, type of nanopartices (silica and alumina), nanoparticle concentration and agitation rate on mass transfer rate were investigated. The concentration of nanoparticles was in the range of 0.0001-0.03% v/v. The volumetric liquid-side mass transfer coefficient (k L a) of CO 2 was estimated by using film theory. The results show maximum enhanced absorption rates of 42.53% and 35.22% for SiO 2 and Al 2 O 3 particles (compared to base solution), respectively. It is also found that SiO 2 nanoparticle is a better candidate than Al 2 O 3 nanoparticle and 0.001 vol% of nanoparticles is an optimum concentration for CO 2 absorption enhancement for the present experimental conditions. The nanoparticles suspended in the base fluid cover the bubble, and as the movement of the fluid due to external forces becomes more dynamic, the particles collide with the gas-liquid interface, breaking the bubble into smaller size bubbles. More bubbles mean a larger interfacial area which would promote the mass transfer from the gas to the liquid. Addition of nanoparticles to the base solution decreases the surface tension of fluid which causes larger interfacial area. Keywords: Volumetric mass transfer coefficient, carbon dioxide, agitated vessel, amine solution, nanoparticles, nanofluids
