Packed and fluidized bed absorber modeling for carbon capture with micro-encapsulated sodium carbonate solution

Abstract

Micro-Encapsulated CO2 Sorbents (MECS) are a promising technology for post-combustion carbon capture because they enable slow-reacting solvents like carbonate solution to compete with traditional amine solvents. Before scaling up MECS for pilot testing, modeling is needed to design a MECS absorber and quantify its size and energy penalty. To that end, a multi-scale model for MECS- that ranges from a single capsule to a 500 MWe power plant absorber- is developed and presented here. First, the individual capsule model is developed and fitted to experimental CO2 absorption data collected on a 0.1 g sample of capsules filled with sodium carbonate solution. This capsule model is then validated against data collected on a 25 g batch of capsules exposed to flue gas conditions in a fluidized column. This model is then scaled up to represent two absorber designs: a multi-stage, counter-flow fluidized bed and a hollow, cylindrical packed bed with radial gas flow. These two absorber bed models are first optimized for a 1 MWe pilot-scale absorber, and then optimized for a 500 MWe coal plant. This model predicts absorbers of similar dimensions and smaller energy penalties than previously modeled absorbers filled with amine solvent capsules. Furthermore, it is demonstrated here that a few reasonable improvements to capsule design would result in absorber sizes and energy penalties lower than those of a benchmark amine solvent tower. These results demonstrate that micro-encapsulated carbonate solution can compete with faster-acting amine solvents for post-combustion carbon capture.