Coupled Transport and Reaction Modeling of Sorbent Particle Size Effects in Nonisothermal Packed-Bed CO₂ Adsorption

Abstract

High Resolution Image Download MS PowerPoint Slide Recent studies have shown that solid sorbents offer a promising route for post-combustion CO 2 capture. This potential remains uncertain because the influence of particle size on the capture efficiency and reactor performance has not been fully characterized. Here, we developed a two-dimensional CFD Eulerian–Eulerian model, validated it against experimental data, and applied it to simulate CO 2 capture in a packed-bed reactor filled with spherical particles of 0.5, 0.8, and 1.5 mm diameter. A carbon-based sorbent impregnated with potassium carbonate (K 2 CO 3 ) was chosen for this study due to its relevance in industrial CO 2 capture. Under our baseline conditions of 10% CO 2, 60 °C, this sorbent follows a Langmuir isotherm with a maximum capacity of about 1.4 mmol of CO 2 /g at 60 °C and achieves roughly 1.2 mmol/g uptake. Its moderate thermal conductivity of 0.25 W/m·K helps dissipate the heat released during adsorption, minimizing temperature gradients across the bed. Gas–solid interactions were modeled via a Eulerian–Eulerian framework, explicitly defining interphase forces to capture momentum exchange. We used the Syamlal–O’Brien correlation for drag. Smaller particles (0.5 mm) achieved nearly complete CO 2 removal but produced a high pressure drop of 4.2 kPa. Larger particles of 1.5 mm reduced the pressure drop (0.9 kPa) but lowered the capture efficiency to 73%. Midsized particles of 0.8 mm struck a balance, reaching about 85% capture with a moderate pressure drop of 1.7 kPa. We observed that increasing the inlet gas flow by 20% shortened the breakthrough time to 23 min but slightly reduced the capture efficiency, indicating a trade-off between the flow rate and the performance. Because CO 2 adsorption is exothermic of −145 kJ/mol, careful thermal management is required to maintain stable operation.

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