In a refinery, FCC and RFCC are both cracking units used to convert heavy oil into lighter valuable products like gasoline, LPG, and diesel.
The main difference is the type of feedstock they process and how “heavy” that feed is.

FCC (Fluid Catalytic Cracking)

Purpose

Converts relatively lighter heavy oils into:

• Gasoline
• LPG
• Light cycle oil
• Propylene

Typical Feed

• Vacuum Gas Oil (VGO)
• Atmospheric gas oil

These feeds are cleaner and contain:

• Lower sulfur
• Lower metals
• Less carbon residue

Characteristics

• Lower coke formation
• Easier catalyst operation
• Better gasoline yield
• Lower catalyst contamination

Main Products

• Petrol/Gasoline
• LPG
• Olefins
• Diesel components

RFCC (Residue Fluid Catalytic Cracking)

Purpose

Processes much heavier refinery residue to maximize valuable products.

Typical Feed

• Residue oil
• Reduced crude
• Atmospheric residue
• Vacuum residue (partially)

These feeds are much dirtier and heavier:

• High sulfur
• High metals (Ni, V)
• High Conradson carbon residue (CCR)
• More asphaltenes

Characteristics

• Much higher coke formation
• Higher regenerator temperature
• More catalyst deactivation
• Requires specially designed catalyst and hardware
• More severe operating conditions

Main Products

• LPG
• Gasoline
• Propylene
• Slurry oil
• More coke than FCC

Simple Difference

Easy Operator-Level Understanding

Think of it like this:

• FCC = cracks “heavy oil”
• RFCC = cracks “very dirty bottom residue”

RFCC is basically a tougher, heavier-duty version of FCC designed to extract value from low-quality residual oil.

Key Operational Difference for Operators

In RFCC units operators usually monitor more carefully:

• Catalyst circulation
• Regenerator temperature
• Delta coke
• Slurry system
• Metals contamination
• Afterburn risk
• Erosion issues

Because residue feed creates:

• More coke
• More fouling
• More catalyst poisoning

Typical Refinery Use

• Older/simple refineries often use FCC.
• Modern deep-conversion refineries use RFCC to maximize profit from heavy crude oils.

Examples:

• Middle East heavy crude processing refineries often prefer RFCC.
• Petrochemical-focused refineries may use FCC for propylene production.