This project focus on the understanding of gas-liquid mass transfer and the development of a gas-liquid vortex unit in the CO2 context. Fundamental experiments combined and numerical simulations can bring its design and efficiency to an unprecedented level. Therefore, advanced visualization technologies and novel numerical simulation methods will be used or developed to reveal and understand the mass transfer process between gas and liquid phases at different scales. X-ray computed tomography, high-speed camera and particle image velocimetry measurements will be employed to investigate the liquid holdup, droplet distribution and flow evolution, further contributing to the modelling of the mass transfer area. Computational fluid dynamics simulation of the gas-liquid flow coupled with overall/local mass transfer coefficient will be developed and validated based on the obtained data. This information will be used to build a CO2 capture and separation unit. To further intensify mass transfer in this unit, an optimization framework consisting of automated mesh generation, numerically solving the equations in combination with an optimization algorithm will be developed. This project will not only give a better understanding of gas-liquid mass transfer, but will also show a paradigm of process intensification based on fundamental experiments, visualization, modelling and computational fluid dynamics simulation.