ASPEN PLUS

A: A fits because alkaline sour water drives SSC and hydrogen damage in carbon steel, and PWHT is the usual control when hardness is managed. B looks attractive due to stainless bias, but NH3/H2S service often causes ammonium bisulfide corrosion and under‑deposit attack that stainless doesn’t magically fix. C addresses chlorides, which aren’t the controlling species here. D is valid in hot dry sulfidation, not aqueous sour systems at 120 °C.

A: A holds under audit: contracts fix the technical baseline, and any shift needs a managed change. B feels safety‑driven, but regulators look for contractual clarity, not silent upgrades. C confuses software defaults with legal obligation — Aspen isn’t a code authority. D sounds pragmatic, yet mixing editions creates an untraceable basis that auditors tear apart.

A: A tracks the usual Fenske–Underwood–Gilliland logic: moving off total reflux typically doubles stages. B underplays the penalty of finite reflux. C exaggerates; that happens at very low relative volatility, not 2.5. D treats Gilliland as deterministic when it’s a band, not a point.

A: A aligns with pressure and chemistry — cubic EOS handles hydrocarbons cleanly. B is tempting if you’ve lived in solvent systems, but activity models break down at 100 bar. C mixes models without thermodynamic continuity. D adds electrolyte complexity where none is controlling.

A: A reflects reality: Aspen stops at process duty and hydraulics. B is a common false comfort — no simulator certifies pressure vessels. C applies only if contractually specified and still needs mechanical design. D confuses software governance with pressure equipment law.

A: A matches field history: oxygen drives degradation products and localized attack. B needs dry high‑temp sulfur service. C assumes chloride control failure, not stated here. D is an old refinery myth at these temperatures.

A: A reflects real separators failing design because dew‑point systems are sensitive. B ignores slope of phase envelope. C violates basic thermodynamics. D invents a temperature threshold that doesn’t exist.

A: A captures why codes exist: they guard against scenarios simulators don’t test. B confuses math with hazard control. C narrows the scope incorrectly — 14C is about protection systems. D would fail any audit instantly.

A: A reflects industry defaults that usually land close. B overstates real hydraulics. C is overly pessimistic and inflates columns. D pretends variability doesn’t exist.