CO

2

absorption into absorbents is a widely used method to reduce carbon emissions

in which the concentration gradient near the gas-liquid interface may induce Rayleigh convection (RC). Once RC occurs

the mass transfer rate will be significantly enhanced. Therefore

it is necessary to explore the mass transfer enhancement mechanism further and develop a penetration/surface divergence hybrid mass transfer model. In this study

we conduct research on the process of CO

2

absorption into ethanol with RC. Firstly

we use a multi-relaxation time lattice Boltzmann method to simulate the absorption process and obtain the flow and concentration fields. And we also verify the reliability of the numerical simulation results by comparing with the experimental results. Then

we analyze the characteristics of non-uniform flow and concentration fields in RC. Moreover

we divide the near-interface region into diffusion-dominated and convection-dominated mass transfer zones by checking whether the horizontal average velocity is greater than 1.0×10

-4

m·s

-1

. Furthermore

based on the differences in mass transfer m

echanisms of the aforementioned two zones

we propose a penetration/surface divergence hybrid model to predict the instantaneous mass transfer coefficient. The prediction results demonstrate that the hybrid model can precisely predict the instantaneous mass transfer coefficient of the entire CO

2

absorption process. Our proposed hybrid model provides a promising way to deal with the complex mass transfer problems with non-uniform flow and concentration fields.