At present, the greenhouse effect is becoming increasingly severe, making it crucial to control CO₂ emissions from fossil fuel combustion. Carbon dioxide capture technology represents both the primary step and the critical pathway, serving as a vital means for reducing carbon emissions in the future.

Based on a novel double-contact carbon capture gas-liquid two-phase absorption bed, and to investigate its enhanced mass transfer performance for ammonia-based carbon capture, this study employs an Eulerian-Lagrangian CFD framework. By integrating dual-film theory into a secondary development of Fluent, a mass transfer model for ammonia-based carbon capture is constructed.

The droplet load exhibits a unimodal distribution along the tower height, being low near the walls and high towards the center. As the liquid-to-gas ratio decreases, the net CO₂ flux increases, leading to a higher droplet load. Significant flow deviation exists at the flue gas inlet, with its severity diminishing as the liquid-to-gas ratio decreases. The uneven droplet distribution causes non-uniformity in CO₂ absorption and concentration field distribution. When the liquid-to-gas ratio decreases from 0.40 m³/m³ to 0.17 m³/m³, the CO₂ capture efficiency drops from 89.19% to 77.29%, a reduction of 13.34%, while the outlet CO₂ molar fraction rises from 1.45% to 3.00%. The overall gas-phase mass transfer coefficient (K_G) remains relatively high below three-quarters of the bed height. A banded region of low K_G forms beneath the nozzle manifold. In the region above the nozzles, K_G gradually decreases with increasing bed height due to insufficient mass transfer driving force and the influence of mass transfer resistance from the gas film side. As the liquid-to-gas ratio decreases, the high K_G zone contracts, and the banded low K_G zone exhibits a parabolic upward trajectory. Regarding the flow field, two high-velocity zones and vortices form within the bed due to the inlet and Venturi effect. The average gas phase velocity in the Z-direction exhibits a bimodal distribution along the bed height, a symmetrical three-segment oscillation along the X-cross section, and a non-monotonic distribution along the Y-cross section. As the liquid-to-gas ratio decreases, the disturbance between the gas and liquid phases intensifies, causing the average gas phase velocity along the Y=0 cross section and the X-cross section to gradually increase.

The double-contact carbon capture gas-liquid two-phase absorption bed exhibits favourable mass transfer characteristics, with the liquid-to-gas ratio exerting a significant regulatory effect on both flow and mass transfer. These findings provide a theoretical basis for optimizing carbon capture equipment.