Enhanced weathering to capture atmospheric carbon dioxide: Modeling of a trickle-bed reactor

Abstract

Enhanced weathering (EW) of alkaline minerals can potentially capture CO2 from the atmosphere at gigaton scale, but the reactor design presents great challenges. We model EW with fresh water in a counter-current trickle flow packed bed batch of 1–10 mm calcite particles. Weathering kinetics are integrated with the mass transfer of CO2 incorporating transfer enhancement by chemical reaction. To avoid flooding, flow rates must be reduced as the particles shrink due to EW. The capture rate is mainly limited by slow transfer of CO2 from gas to liquid although slow dissolution of calcite can also play a role in certain circumstances. A bed height of at least 7–8 m is required to provide sufficient residence time. The results highlight the need to improve capture rate and reduce energy and water consumption, possibly through enriching the feed with CO2 and further chemical acceleration of the mass transfer.