Fluid Catalytic Cracker (FCC)
Convert gas oil to lighter and more valuable products like;
LPG, gasoline, distillate, and cycle-oil.
FCC is a high temperature low pressure catalytic unit in
which heavy hydrocarbons are cracked into lighter
molecules.
Fluid Catalytic Cracker (FCC)
•Originally cracking was accomplished thermally
• But the catalytic process has almost completely replaced
•Catalytic Cracking processes
Thermafor Catalytic Cracker (TCC)
• Very few.
• Moving bed reactor.
Fluid Catalytic Cracker ( FCC)
• More common.
• Fluidized bed reactor.
Fluid Catalytic Cracker (FCC)
Thermal versus Catalytic Cracking Yields
Thermal cracking Catalytic
cracking
wt% vol% wt% vol%
Fresh feed 100.0 100.0 100.0 100.0
Gas 6.6 4.5 - -
Propane 2.1 3.7 1.3 2.2
Propylene 1.0 1.8 2.0 3.4
Isobutane 0.8 1.3 2.6 4.0
n-Butane 1.9 2.9 0.9 1.4
Butylene 1.8 2.6 2.6 3.8
C5_ gasoline 26.9 32.1 40.2 46.7
Light cycle oil 1.9 1.9 33.2 32.0
Decant oil - - 7.7 8.7
Residual oil 57.0 50.2 - -
Coke 0 - 5.0 -
Total 100. 0 96.5 100.0 102.2
Fluid Catalytic Cracker (FCC)
• Cracking process produces carbon (coke)
• Remains on the catalyst and rapidly lowers its activity
• To maintain the catalyst activity
• Necessary to regenerate the catalyst Cracking processes
• By burning off this coke with air; as result
• Continuously moved from reactor to regenerator and back
• Cracking reaction endothermic; regeneration exothermic.
Units are designed using this heat to supply needed
Fluid Catalytic Cracker (FCC)
Fluid Catalytic Cracker (FCC)
• Average riser reactor Temper. 900 to 1000oF (480–540oC),
• Oil feed temperatures from 500 to 800oF (260–425oC)
• Regenerator exit catalyst from 1200 to 1500oF (650–815oC).
•Modern FCC units are continuous processes 24 h/d
•Maintenance after 3-5 years between scheduled shutdowns
•There are two different configurations for an FCC unit
“Stacked" type: reactor above the catalyst regenerator
“Side-by-side" type: reactor and catalyst regenerator are in
two separate vessels
Fluid Catalytic Cracker (FCC)
Fluid Catalytic Cracker (FCC)
Fluid Catalytic Cracker (FCC)
•Coke formation deactivated the
surface of the catalyst
• Catalyst and hydrocarbon separated
mechanically,
• Steam stripping remove remaining
oil on the catalyst before the catalyst
enters the regenerator.
• Burning coke with air in
regenerator reactivates catalyst
Fluid Catalytic Cracker (FCC)
•Reg. Ts are carefully controlled to
prevent catalyst deact.
• And to provide the desired amount
of carbon burn-off
• This is done by controlling the air
flow to give a desired CO2/CO ratio
in the exit flue gases
Products
Catalytic Cracking
REACTIONS
CRACKING REACTIONS
The products formed in catalytic cracking are the result of
both primary and secondary reactions. Primary reactions are
designed as those involving the initial carbon–carbon bond
scission and the immediate neutralization of the carboniumion
The primary reactions can be represented as follows:
Paraffin → paraffin +olefin
Alkyl naphthene → naphthene +olefin
Alkyl aromatic → aromatic +olefin
CATALYSTS
CRACKING CATALYSTS
Three classes:
Acid-treated Natural aluminosilicates
Amorphous synthetic silica-alumina combinations
Crystalline synthetic silica-alumina catalysts zeolites
CASE-STUDY PROBLEM
The feed to fluid catalytic cracking unit (FCC) using
Zeolite catalyst is equal to 37,000 BPCD. Make a total
mass balance around FCC for the following:
Component Vol% API wt%S
650-850 oF 51.4 22 0.1
850-1050 oF 48.6 16 0.29
CASE-STUDY PROBLEM
CASE-STUDY PROBLEM
