Page 306 - Sustainability in the Process Industry Integration and Optimization

T y p i c a l P i t f a l l s a n d How t o Avo i d T h e m 283

16. Based on the optimization, extract adjusted data and return
to step 7. Perform an additional loop (or loops) while
screening and scoping for potential simplifications.
17. Consider real plant constraints; these include safety,
technology limitations, controllability, operability, flexibility,
availability, and maintainability.
18. Pay attention to start-up and shutdown of the process; some
early designs for highly integrated plants had problems in
this area.
19. Run a second optimization for the final tuning accounting
for the information added during steps 16 to 18. If necessary,
return to any appropriate previous step for adjustment.
20. The design is now ready for detailing. However, optimization
is a never-ending procedure, and designs may need to be
modified in response to changes in operating conditions
(e.g., plant capacity) or the economic environment (e.g., tax
policy; prices for energy, materials, and production).

12.1 Data Extraction
As emphasized previously, data extraction is a crucial step. Bodo
Linnhoff presented one of his last plenary lectures (Linnhoff and
Akinradewo, 1998) on the automated interface between simulation
and integration. This has been a substantial step toward data
extraction for PI software tools. The plenary has been fairly
comprehensive and suggested the way forward for this important
task. The problem received increased interest following this lecture,
and several software packages now offer support for solving it.
Nonetheless, more work in this area is needed to satisfy the
requirements of routine industrial applications.
In their SuperTarget and Pinch Express software packages,
Linnhoff March (1998) included procedures for automatic extraction
of data for Heat Integration. Even so, thermal data, which involve the
stream heating and cooling information and utilities information,
are the most critical data required for Pinch Analysis. There are
several possibilities for extracting the thermal data from a given heat
and material balance. This must be done carefully, as poor data
extraction can easily lead to missed opportunities for improved
process design. In extreme cases, poor data extraction can falsely
present the existing process flow-sheet as optimal in terms of energy
efficiency. If the data extraction accepts all the features of the existing
flow-sheet then there will be no scope for improvement. If it does not
accept any features of the existing flow-sheet then Pinch Analysis