Synthesis and characterization of Al2O3-methanol nanofluid and its usage in bubble column for an improved mass transfer rate

Abstract

Methanol-based physical absorption, known for its effective CO2 capture ability, has been employed in acid gas removal (AGR) unit. However, the high energy consumption associated cooling methanol and acid gas hampers its widespread adoption. To address this challenge, numerous studies have explored the use of nanoparticles to enhance the CO2 absorption at room temperature, thereby reducing the energy requirements. In this study, the objective is to synthesize and characterize the Al2O3-methanol nanofluid and investigate its application in a bubble column for improved mass transfer rates during CO2 absorption. The methanol based Al2O3 nanofluid was prepared using the two-step method with ultrasonication technology and CO2 absorption in the resultant product was investigated. Initially, 0.001 vol%, 0.01 vol % and 0.1 vol% Al2O3 nanoparticles was added to methanol solution and to mixture them well via ultrasonication technology. The static settlement method and zeta potential analysis were utilized to characterize the stability of the as-prepared nanofluid. Both impact of sonication power and time on the stability of nanofluid were discussed as well. Then, numerical simulations was employed to investigate the mass transfer coefficient for CO2 absorption and the numerical uncertainty was carefully analyzed to verify the reliability of the numerical method. It revealed a 7.3%, 29.2% and 60.7% enhancement in mass transfer coefficient during CO2 absorption for 0.001 vol%, 0.01 vol% and 0.1 vol% nanoparticles under room temperature, respectively. The visualized reason for this improvement was related to the enhanced bubble breakup and coalescence after adding nanoparticles to methanol. The expanded interfacial area between gas and liquid plays a vital role in the mechanism of this improvement.

Keywords

• CO2 absorption
• Al2O3 nanoparticles
• Mass transfer enhancement