Crude fractionation naming: In refinery primary fractionation, the product group that includes gas oil, diesel oil, and heavy fuel oil is generally classified under which fraction family?

Introduction:
Refinery fractionation labels (light ends, light distillates, middle/intermediate distillates, heavy distillates, residues) help group products by boiling range and handling. Knowing where gas oil, diesel oil, and heavy fuel oil sit in this schema aids material balance and product slate understanding.

Given Data / Assumptions:

• Gas oil and diesel are heavier than naphtha/kerosene but lighter than atmospheric/vacuum residues.
• Heavy fuel oil can be a heavy distillate or a distillate–residue blend, typically boiling in the heaviest liquid range below residue.
• Terminology varies; the question groups these three together.

Concept / Approach:
Across many texts, naphtha and kerosene are treated as light to middle distillates, while gas oils and heavy fuel oils fall into the heavy distillates pool (short of residue). Although “middle/intermediate distillates” often includes diesel and kerosene, the trio specified—gas oil, diesel oil, and heavy fuel oil—together most appropriately aligns with the heavy distillate family, excluding residues and light ends.

Step-by-Step Solution:

Verification / Alternative check:
Refinery course notes frequently depict diesel and gas oil at the upper portion of the atmospheric column draw-offs, with heavy fuel oil as a heavy distillate stream or blend, all above true residue.

Why Other Options Are Wrong:

• Intermediate distillates: Would capture diesel and kerosene but not typically heavy fuel oil as a group.
• Light ends: LPG and light gases only.
• Residues: Heavier than heavy distillates; contain asphaltenic bottoms.
• Non-hydrocarbon by-products: Not a fraction family.

Common Pitfalls:
Rigidly applying one naming convention; this question bundles the set toward the heavy distillate end rather than middle-only.

Final Answer:
Heavy distillates