Page 227 - Fluid Catalytic Cracking Handbook

Products and Economics 195

(text continued from page 190)
• Increase in the catalyst activity and hydrogen transfer properties
• Increase in catalyst-to-oil ratio (Figure 6-11)
• Increase in the use of main column overhead reflux rate instead
of top pumparound to control the top temperature

LCO

The emphasis on gasoline yield has sometimes overshadowed the
importance of other FCC products, particularly LCO. LCO is widely
used as a blending stock in heating oil and diesel fuel. This is par-
ticularly important during winter, when the price of light cycle oil can
be higher than gasoline. Under these circumstances, many refiners adjust
the FCC operation to increase LCO yield at the expense of gasoline.

LCO Yield

A refiner has several options to increase LCO yield. Since it is often
desirable to maintain a maximum cracking severity while maximizing
light cycle oil yield, the simplest way to increase LCO yield is to
reduce the gasoline end point. Gasoline end point is usually reduced

450
OCTANE
OCTANE BBL
Feed Sulfur = 0,46 wt% j
f.400 (-
t
•5 F
"3 350
w
£P
c
300
!
r

250
4 5 6 7
Catalyst to Oil Ratio (W/W)
Figure 6-11, Increased catalyst-to-oil ratio decreases gasoline sulfur [4],