Process Technology Quick Reference Cards
FCC
Chapter from the Process Technology Quick Reference Cards.
FLUID CATALYTIC CRACKING (FCC)
Process Objective
Crack heavy gas oil into gasoline, LPG, and light cycle oil using hot regenerated catalyst in a riser reactor.
Key Operating Variables
| Variable | Typical Range | Effect / Notes |
|---|---|---|
| Riser Outlet Temp | 950-1,020°F | Higher T → more conversion, more gas + coke |
| Cat/Oil Ratio | 4-10 wt/wt | Higher → more conversion (more catalyst contact) |
| Feed Preheat | 400-700°F | Affects cat/oil ratio (heat balance lever) |
| Catalyst Activity (MAT) | 60-75 | Higher activity → more conversion per unit catalyst |
| Feed CCR | 0.1-1.0 wt% | Higher CCR → more coke, less gasoline selectivity |
Process Configurations
Modern riser FCC: all cracking in riser (2-5 sec), disengager vessel above
Resid FCC (RFCC): processes atmospheric resid — requires catalyst cooler
Dual riser: separate risers for different feeds (naphtha cracking + gas oil)
Petro-FCC: maximizes propylene/ethylene yield — high severity, ZSM-5 additive
Products & Yields
Fuel gas (C2-): 3-5 wt% (refinery fuel)
LPG (C3/C4): 12-20 vol% (propylene = petrochemical value)
Gasoline: 45-55 vol% (major gasoline blending component, ~92 RON)
LCO: 10-20 vol% (low cetane diesel blending — requires HDT)
Slurry/CLO: 5-10 vol% (fuel oil or carbon black feedstock)
Coke: 4-6 wt% (burned in regenerator for heat)
Common Troubleshooting
Afterburn: CO burning in dilute phase — add Pt promoter, increase O2
Catalyst losses: damaged cyclones, high attrition — inspect at T/A
Slide valve issues: erosion, coking — monitor valve position and response
Poor stripping: high delta coke — increase stripping steam, inspect baffles
Feed nozzle problems: poor conversion, high slurry — check nozzle ΔP
Source: Process_Tech_Quick_Reference_Cards_v1.xlsx · sheet “FCC”
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