Modelling of Hybrid Carbon Capture via Membrane and Potassium Carbonate Process

Abstract

This thesis presents a techno-economic assessment of three post-combustion CO₂ capture technologies applied to the flue gas of the Luminus-Seraing natural gas combined-cycle (NGCC) plant. The flue gas, characterized by a low CO₂ concentration (4.5%) and high flowrate (1069 kg/s), corresponding to a capture scale of 246 tCO₂/h, represents a particularly challenging case for post-combustion capture.

Three configurations were evaluated: a two-stage membrane system, a potassium carbonate absorption process, and a hybrid membrane–solvent integration. The membrane process achieved the lowest capital cost (280 M€) but only moderate CO₂ purity (≈70%), insufficient for transport or storage. The potassium carbonate process delivered high-purity CO₂ (>96%) but incurred high energy penalties (5.4 GJ_work/tCO₂, 3.2 GJ_heat/tCO₂) and capture costs (≈295 €/tCO₂). By contrast, the hybrid configuration enriched the absorber feed to 30% CO₂, reducing equipment size and energy demand, and lowering the capture cost to ≈152 €/tCO₂.

Although still above pilot-scale benchmarks (70–90 €/tCO₂), the study demonstrates that hybridization can substantially reduce the cost and energy intensity of capturing CO₂ from dilute NGCC flue gases. Future work should focus on global optimization, thermal integration, and embedding the models into the decision-support tool for large-scale deployment developed by PhD researcher So-Mang Kim.