Modelling of ex situ dissolution for CO2 sequestration

Abstract

In this paper, a model for diffusion-controlled dissolution of carbon dioxide (CO2) droplets is presented. This model is applied to a system of co-current turbulent horizontal pipe flow of carbon dioxide–brine mixture in order to determine the feasibility of dissolving carbon dioxide within the pipe before injecting underground. Depending on the droplet size, there are two regimes of dissolution within the pipe: turbulent for large droplet size and laminar (pure diffusion) for smaller sizes. Since the droplet (while dissolving and therefore shrinking in size) may undergo both regimes, the droplet size at which it transitions from turbulent to diffusion-controlled dissolution is estimated and used to find the total time spent in diffusion-controlled dissolution regime. It was observed that diffusive dissolution is of similar order of magnitude to turbulent dissolution, and so both mechanisms must be taken into account in the evaluation of the total dissolution time. This diffusive dissolution time should be combined with the time spent in the turbulent regime to determine time pipe lengths required for complete dissolution of carbon dioxide droplets.