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Distillation Control Configuration Selection
Authors:
Scott
Hurowitz1, Joe Anderson2, Marshall Duvall3, and
James B. Riggs4
ABSTRACT
Detailed
dynamic simulations of three distillation columns (a propylene/propane splitter,
a xylene/toluene vacuum column, and a depropanizer) have been used to study the
issues of configuration selection for single and dual composition control,
feedforward control using a feed composition analyzer, and decouplers using
control perfomance results for PI controllers. ATV identification [1] with online tuning
for setpoint changes was used for tuning the diagonal PI composition
controllers. In addition,
controller reliability tests were conducted by inducing reboiler duty upsets.For
dual composition control, the optimum configuration changes from one column to
another, but it is found to be among a predictable set of control
configurations. When the control of
both products is equally important, four or eight potential configurations must
be considered, which usually requires a number of dynamic simulations to
identify the optimum configuration. On
the other hand, guidelines are presented for reducing the number of viable
control configurations to two for cases in which one product is more important
than the other. Feedforward control
using a feed composition analyzer and one-way decouplers are shown to offer
significant advantages for specific control configurations, but can degrade
control performance for others. The
results presented here are consistent with other studies in the field, but
provide a more unified description of the field.
Publication Information: accepted to J. Process Control
Corresponding Author: J.B. Riggs
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