There are many issues to be decided
during the design of a new plant. Some firms want plants to
run exactly at the design rate- no more and no less. Other
firms want units designed conservatively so that the unit can
be debottlenecked relatively easily to higher than design
rates. Design conservatism also increases the processing
flexibility for different feeds or for different product
specifications. Some important design philosophies that
maximize the debottlenecking flexibility of a new plant
- Provide flexibility for other
operating scenarios and conditions (e.g., start of run
conditions, high conversion, higher impurity levels).
- Oversize specific critical
equipment (vacuum systems, FCCU compressors, critical
- Over-design utility systems
(flare, cooling water, steam, etc.) if future expansion is
- Design new towers and internals
for less than 80% of flood.
- Install 2 pass trays instead of
1 pass trays when borderline.
- Do not install high capacity
trays or packing.
- Do not install extended surface
shell and tube exchangers.
- Purchase pumps and compressors
that meet the design conditions with smaller than the
- Install drivers and delivery
systems that can handle the maximum power required by the
- Specify new equipment design
pressures high enough so that they will not be violated at
above design rates.
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