CO2 dissolution in n-decane at 60 bar (PC-SAFT)

A CO2/methane gas contacted with n-decane at 60 bar and 313 K — the screening question behind CO2-EOR injection and physical-solvent CO2 removal: how much of the gas the oil takes up, and how much heat that releases. It runs on PC-SAFT (Gross & Sadowski 2001, chain + dispersion), the molecular equation of state for exactly this combination of a supercritical light gas and a long-chain alkane. The adiabatic mixer warms from 313 to 328 K on the heat of dissolution, and the isothermal contactor at 313 K leaves 186 mol/s of loaded oil (25.5 mol% CO2, 20.6% methane) against 14 mol/s of lean gas at 82% methane: 95% of the CO2 and 77% of the methane dissolve. Building this card exposed a flowsheet defect worth knowing about: the (P,H) flash behind every adiabatic mixer verified its answer by re-solving over the whole 80-1200 K range, and a SAFT density root at 80 K returns a residual enthalpy of the wrong sign, so the mixer reported 80 K for a state that is 328 K. The verification now brackets outward from the branch solution and keeps it when no sign change exists. Still bounded: PC-SAFT's bubble-point routine puts this mixture's bubble point at 421 K while its own flash finds vapour at 300 K — the flash is right and is what the results use; the saturation routine is the documented follow-up. No binary kij beyond what the package ships.