Acetone-water column at 3 atm (PR + Wong-Sandler)

An acetone recovery column at 3 atm on Peng-Robinson with the Wong-Sandler mixing rule — the one Gᴱ rule that keeps the quadratic composition dependence of the second virial coefficient, so it stays thermodynamically consistent at high pressure. 20 mol% acetone feed, 14 stages, reflux 2, 25% distillate: 80 mol% acetone overhead and acetone-free water in the bottoms, 2.65 MW on the reboiler. The cut is set at 0.25 rather than the feed's exact acetone fraction of 0.20, which pinned the column on a razor edge (temperature residual 2e-3, balance 3%); at 0.25 it closes to zero. Bound: the rule is driven by the low-pressure acetone/water NRTL binary and, as flowsim/solver/thermo/ge_params_neqsim.py records, NeqSim's Wong-Sandler kij is deliberately not wired in, so the second-virial cross term uses the van der Waals kij.