Page 386 - Design of Simple and Robust Process Plants

9.5 Closed Loop Steady-state Optimization 373

Vapor
load

Operational
area

Liquid load
Fig. 9.11. Constraints of a distillation column.

Table 9.1. Constraints of simple distillation column.

Process Bottom temperature (decomposition)
Top temperature (solidification)
Column Design temperature
Design pressure
Internals Flooding and weeping of top section and bottom section
Gas loading (high and low)
Liquid loading (high and low)
Overload at feed section (high and low)
Pressure drop
Reboiler Fouling
Heat source temperature and pressure
Design temperature and pressure. Shell and Tube
Condenser Fouling
Cooling medium temperature and pressure
Design temperature and pressure inside and outside
Reflux drum Design temperature and pressure
Instrument measurements Range
Instrument actuators Capacity/range
Lines Design temperature and pressure
Pressure drop
Pumps Design temperature and pressure
Capacity and head

The final result of the model should be accurate and robust over the entire opera-
tional range. The model must be tested in combination with the optimizer, and
demonstrate its robustness from different starting points.
At the feasibility stage (Section 9.6.1), the factors that play an important role in
the overall economic process performance are identified by sensitivity analysis. Also,