Three-stage condensate stabilization (Soave-Redlich-Kwong)

Wellhead fluid at 60 bar and 320 K — 60% methane with ethane through n-hexane — through a high-pressure separator, a letdown to 15 bar and an adiabatic medium-pressure separator, then to 2 bar and a low-pressure separator, on plain SRK with its shipped kij: the workhorse cubic for hydrocarbons, exactly where it is meant to be used. What it computes: 69 mol/s of HP gas at 76% methane, 10 mol/s of MP flash gas, 5 mol/s of LP gas rich in propane and butane, and 15.9 mol/s of stabilized condensate carrying 0.2% methane and 2.2% ethane — the light ends that would otherwise vent from a tank. The Joule-Thomson cooling across each valve is the model's, not an input: 320 to 304 K at the first letdown, 280 K at the second. No honesty note needed here beyond the obvious: a real stabilizer would reboil the last stage.