Solvent Screening for CO2 Capture

Solvent Class

Column Conditions

Absorber temperature 40 °C

Flue-gas CO2 inlet 15 %

Gas flow rate 1.0×

Live Readouts

Captured 0%Vented 100%

Capture eff.

Solvent loading

Regen. energy

0 GJ/t

How it works

CO2 absorption into a liquid solvent at equilibrium follows a Langmuir-type isotherm, with the equilibrium constant K set by temperature through the van't Hoff relation (exothermic absorption, so K falls as T rises):

K(T) = K0 · exp[ -(ΔH_abs/R) · (1/T - 1/T_ref) ]
θ = K·p_CO2 / (1 + K·p_CO2)      (fractional solvent loading, 0-1)
Efficiency = 100 · θ · kinetic_factor(flow, solvent)

ΔH_abs is the (negative) molar enthalpy of CO2 absorption — a strong, exothermic bond (amines) gives high low-temperature capacity but a large regeneration energy penalty; a weaker bond (ionic liquids) needs less heat to reverse but reacts more slowly, capped here by a solvent-specific kinetic ceiling representing finite gas-liquid contact time in the column.

Aqueous MEA — fast, strong chemisorption (ΔH≈-84 kJ/mol), best near 40-60 °C, but among the most energy-intensive to regenerate.
Hot K₂CO₃ — weaker carbonate/bicarbonate equilibrium (ΔH≈-71 kJ/mol), runs hot (70-120 °C) so absorption and stripping sit closer together thermally.
Chilled NH₃ — high capacity when cooled near 0-20 °C (ΔH≈-63 kJ/mol); real plants pay a refrigeration cost not modeled here.
Ionic liquid — lowest regeneration energy (ΔH≈-60 kJ/mol) but the slowest kinetics, so it never reaches the same peak efficiency as the aqueous solvents at a given residence time.

Regeneration energy (GJ per tonne CO2 captured) rises as loading falls, because more solvent mass must be reheated per mole of CO2 recovered — the single largest operating cost of amine-type post-combustion capture in practice.

CO2 (rising) Lean solvent (falling) Captured / rich solvent

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Solvent Screening for Post-Combustion CO2 Capture