Three-stage crude distillation design: In a high-pressure primary tower (first stage) of a three-stage crude oil distillation system, the typical operating pressure maintained is approximately how many kg/cm^2?

Introduction / Context:
Some refinery configurations employ staged crude distillation with a high-pressure (HP) primary tower upstream of medium/low-pressure sections. Recognizing typical pressure levels aids in understanding column design, vapor–liquid traffic, and pump-around duties.

Given Data / Assumptions:

• Three-stage crude distillation: HP primary, followed by lower-pressure sections.
• Nominal crude slate and standard preheat/desalting.
• Pressures quoted as gauge values in kg/cm^2 (approximate ranges).

Concept / Approach:
HP primary towers often operate at a few kg/cm^2 to suppress vaporization in upstream equipment, improve heat integration, and control flash behavior. Typical values cluster around 3 kg/cm^2 for textbook problems, with subsequent stages at progressively lower pressures toward near-atmospheric conditions.

Step-by-Step Solution:

Verification / Alternative check:
Process design examples in petroleum refining courses frequently cite ~3 kg/cm^2 for HP sections, scaling with crude and column size.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming all crude towers run at near-atmospheric pressure; multi-stage systems intentionally vary pressure by stage.

Final Answer:
3