MEA post-combustion CO2 capture (electrolyte NRTL)

The reference amine process on the reference amine: flue gas (12% CO2 at 1.1 bar, 313 K) scrubbed with 30 wt% aqueous monoethanolamine at a lean loading of 0.20 mol CO2 per mol MEA, the rich solvent pumped and heated to 388 K, steam-stripped at 1.9 bar, and the overhead condensed at 313 K into a CO2 product and a reflux-water stream. It runs on the enrtl package — carbamate/bicarbonate/protonation speciation with Davies activity, the CO2 partial pressure a function of loading and temperature — which is what sets the rich loading of 0.53 mol/mol the absorber reaches and drives the stripper the other way at 390 K. What it computes: 24 mol/s of CO2 into 695 mol/s of rich solvent, a 39 mol/s CO2 product at 94 mol% after the condenser knocks out 109 mol/s of water, 3.9 MW of rich-solvent heating for 650 mol/s of circulation (the sensible-heat penalty the sensitivity sweep traces against solvent rate) and 6.8 MW of overhead condensing. Honesty notes: the absorber and stripper are Kremser stage models with the K-value taken at the entering liquid, so the absorber sees the lean-end driving force everywhere and captures essentially all of the CO2 — the 85-90% design figure of a real plant comes from the rich-end pinch and the packed height, which a stage-count shortcut does not resolve (the rate-based absorber was tried and its gas-film HTU of ~0.06 m at atmospheric pressure is not a number to show either) — and the stripper regenerates the solvent to zero loading where a real reboiled column leaves ~0.2. The loop is left open, the same simplification the mixed-amine showcase makes. Building this card also repaired the package: its (T,P) flash was a clamped split that turned a heated rich amine into pure CO2 vapour at the full solvent rate; it is now a Rachford-Rice split that conserves composition through the heater.