In vacuum crude distillation, the heaviest non-vaporized stream leaves the column bottom. Select the correct technical term commonly used for this bottom product.

Introduction / Context:
Crude distillation is performed first at near-atmospheric pressure and then, for heavier cuts, under vacuum. The bottom stream from the vacuum column consists of the highest boiling components that do not distill even under reduced pressure.

Given Data / Assumptions:

• Unit: vacuum distillation column (VDU).
• Stream of interest: column bottoms (heaviest fraction).
• Naming conventions vary across refineries.

Concept / Approach:
The accepted term for the vacuum bottoms stream is “residuum” (often “vacuum residue,” “VR,” or “vacuum resid”). “Reduced crude” generally refers to the atmospheric column bottoms (after lighter components are removed). “Residual crude” is non-standard/ambiguous terminology, and “petrolatum” is a waxy by-product distinct from VDU bottoms.

Step-by-Step Solution:

Verification / Alternative check:
Typical refinery stream maps label VDU bottoms as VR/residuum; downstream uses include asphalt, feed to visbreaker/coker, or deasphalting.

Why Other Options Are Wrong:

Common Pitfalls:
Mixing up AU (atmospheric) and VDU terminology; always specify the unit when naming bottom streams.

Final Answer:
Residuum