Troubleshooting

Chapter from the FCC Operations Guide.

FCC TROUBLESHOOTING DECISION TREES

Common FCC Operating Problems

Problem	Symptoms	Likely Causes	Diagnostics	Corrective Actions	Safety Implications
Afterburn	Regen dilute temp > dense bed temp High cyclone temperatures	Incomplete combustion in dense bed CO burning in dilute phase	Compare dense vs. dilute temps Check O2 in flue gas	Increase excess O2 Add Pt combustion promoter Reduce feed rate	CRITICAL: cyclone damage, refractory failure
Catalyst losses	High stack opacity Low E-cat inventory Fines in slurry	Cyclone damage/erosion Attrition (high velocity) High fines in fresh cat	PSD analysis of E-cat Stack opacity monitor Cyclone ΔP trending	Inspect cyclones at T/A Reduce velocities Change catalyst supplier	Product contamination, environmental
Slide valve problems	Erratic temperatures Pressure balance instability Inability to control circulation	Erosion of valve/seat Coking/deposits Stem or actuator issues	Valve position vs. demand Stroking test Pressure surveys	Adjust valve tuning Plan repair at T/A Use bypass if available	Loss of circulation = emergency
Poor stripping	High coke yield (delta coke) High regen temperature High H/C ratio in coke	Insufficient steam Stripped plugging/maldistribution High catalyst circulation	H/C ratio of coke Stripping steam rate Spent catalyst temperature	Increase stripping steam Clean distributors at T/A Reduce circulation	Excess coke can exceed air/heat limits
Feed distribution issues	Uneven riser temperatures Low conversion at normal conditions High slurry yield	Plugged feed nozzles Low feed pressure Nozzle tip erosion	Riser TI profile Feed nozzle ΔP Nozzle inspection at T/A	Clean/replace nozzles Increase feed pressure Atomizing steam adjustment	Liquid carryover to regenerator
High regenerator pressure	Air blower at limit Restricted flue gas flow Surging	Flue gas slide valve restriction Cyclone plugging Orifice chamber fouling	Check flue gas valve position Regenator ΔP profile Blower surge margin	Open flue gas valve Reduce feed rate (less coke) Clean at turnaround	Blower surge = emergency

Source: FCC_Operations_Guide_v1.xlsx · sheet “Troubleshooting”

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