Origin of petroleum coke in refining: Which process listed below is directly associated with the production of solid petroleum coke as a primary by-product?

Introduction:
Petroleum coke (petcoke) forms when very heavy hydrocarbons undergo severe thermal cracking and polycondensation to solid carbon. Recognising which general process family yields coke helps distinguish unit operations by their severity and products.

Given Data / Assumptions:

• We consider broad categories rather than specific unit names.
• Coke requires severe thermal decomposition of heavy residual feeds.

Concept / Approach:
Coking is an extreme form of thermal cracking. While visbreaking is a mild thermal process intended to avoid excessive coke, and reforming/hydrotreating are catalytic processes targeting different goals, petroleum coke arises from severe cracking (e.g., delayed coking, fluid coking) that converts residue to lighter vapours and solid carbon. “Stabilisation” simply adjusts vapour pressure and removes light ends; it does not make coke.

Step-by-Step Solution:

Verification / Alternative check:
Unit names like delayed coking and fluid coking are explicitly thermal cracking processes known for coke production.

Why Other Options Are Wrong:

• Stabilisation: Light-ends removal; no solid formation.
• Visbreaking: Mild; aims to minimise coke.
• Reforming/Hydrotreating: Catalytic; not designed to create solid carbon.

Common Pitfalls:
Equating any “thermal” unit with coke production; only severe cracking (coking) intentionally produces bulk coke.

Final Answer:
Cracking