Methanol synthesis (syngas loop)

Low-pressure syngas-to-methanol loop (CO + 2 H2 <-> CH3OH, equilibrium reactor at 80 bar/510 K). The high-pressure separator's crude liquid still carries several mol% dissolved CO2/H2/CO from the reactor loop, so a letdown valve plus a second flash (mirroring the HDA casebook's own SEP-LETDOWN-SEP2 degassing pattern) strips the bulk of it before the atmospheric column — dissolved permanent gas at that scale can otherwise mislead a bubble-point search onto a spurious low-temperature root nowhere near methanol/water's real ~340 K bubble point, so keeping the column's own feed genuinely light on non-condensables is the honest fix, not a thermo-solver workaround. From the ChemSep casebook (Methanol_iecr49p6150). Honesty note: the equilibrium constant (0.0021 bar^-2 at 500 K, van 't Hoff to 510 K) is about half of Graaf et al. (1986)'s log10 K = 5139/T − 12.621, and is applied to ideal-gas partial pressures at 80 bar with no fugacity correction — read the conversion as a representative approach to equilibrium, not a rigorous equilibrium limit.