Petroleum refining: What is the typical yield (by weight percent) of straight-run LPG obtained directly from crude oil distillation in a refinery?

Introduction / Context:Liquefied petroleum gas (LPG) is a light hydrocarbon mixture (mainly propane and butane) recovered in refineries from crude oil. When obtained directly from atmospheric and vacuum distillation—without cracking or reforming—it is called straight-run LPG. Understanding its typical yield helps in material balance, product slate planning, and economic evaluation of a refinery crude run.Given Data / Assumptions:

• Feed: untreated crude oil processed through atmospheric (and possibly vacuum) distillation only.
• Product of interest: straight-run LPG (C3–C4 range).
• We are considering typical global refinery practice with conventional crudes (no special condensate-rich case).
• Yield basis: weight percent of crude.

Concept / Approach:Crude oil contains a spectrum of hydrocarbons. The lightest fraction yields gases and LPG. Without conversion processes (e.g., catalytic cracking, hydrocracking), the natural—or straight-run—LPG cut is modest. Industry references consistently report a low single-digit wt% for straight-run LPG across common crude types, often near 1–2 wt% depending on crude light-ends and distillation cut points.Step-by-Step Solution:

Verification / Alternative check:Assays for medium crudes show LPG + dry gas as a small fraction. Where lighter condensates are processed, LPG can rise, but exam-standard “typical” values stay near ~1–1.5 wt% for straight-run only. Higher LPG yields generally require conversion units producing additional C3–C4.Why Other Options Are Wrong:

• 10–15: Too high for straight-run; such values imply conversion-derived LPG or very light condensate slates.
• 20–25: Unrealistically high without extensive cracking operations.
• 0.1–0.2: Too low; would underestimate normal straight-run recovery.

Common Pitfalls:Confusing straight-run LPG with total refinery LPG (which can include conversion LPG). Also, mixing volume percent with weight percent or using unusual crude cases can mislead the estimate.Final Answer:1–1.5 (weight percent)