A Lagrangian Two-Phase Model for Assessing the Near-Field Impacts of CO₂ Ocean Sequestration

A new version of a two-phase numerical model is developed to simulate CO₂ droplet dissolution and the plume dynamics of CO₂ enriched seawater produced by direct release of liquid CO₂ into deep ocean from a towed pipe. This Lagrangian framework model consists of three sub-models. They are the CO₂ droplet moving and dissolving sub-model, the turbulent dispersion of CO₂ enriched seawater sub-model, and the biological impact sub-model. We performed simulations of direct injection of liquid CO₂ from a release platform towed by a moving-ship into mid-depth seawater to examine the roles of injection parameters, including release platform type and initial CO₂ droplet size. Results from the simulations show that a horizontal release platform can create a plume with less physical and biological impacts than a plume created by a vertical release platform. With an injection rate of 100kg/s, simulations predict that injection of small droplets (5mm in diameter) would produce up to 1.5 times the pH reduction of larger droplets (15 mm in diameter). This large pH reduction may significantly affect ambient zooplankton.