Cold-methanol CO2 absorption at 30 bar (SRK + Huron-Vidal)

The Rectisol idea — CO2 dissolves strongly in methanol at -35 C and 30 bar while methane does not — on the one Gᴱ-mixing package whose parameters were regressed for the rule: SRK with Huron-Vidal mixing driven by Equinor NeqSim's Apache-2.0 set (methanol/CO2, methanol/methane fitted at infinite pressure), not by the low-pressure NRTL binaries the other Gᴱ packages borrow. 100 mol/s of 30% CO2 gas against 150 mol/s of cold methanol: the treated gas comes out at 99.9% methane with 0.08% CO2, the rich methanol holds 17 mol% CO2, and a first-stage flash to 2 bar releases 6.3 mol/s of 97% CO2 — a real Rectisol regenerates in several flash stages plus stripping, which is why this solvent still carries 14% CO2. K-values on the package: CO2 0.60 at 238 K against plain SRK's 1.64 (the mixing rule is the whole difference), methane 3100. Two things worth knowing: the lean methanol carries 0.1% dissolved methane on purpose — the cubic K-value refinement collapses onto the trivial solution when a gas is seeded at the 1e-4 placeholder the Kremser absorber uses, and that K of 1 sent 27 mol/s of methane into the solvent before the seed was made physical (recorded in flowsim/solver/CLAUDE.md as an open item); and the absorber is a Kremser stage model at the mean of the two inlet temperatures.