Index ◾  133
use of in manipulated distillate
control scheme, 36
use of in reflux control scheme,
38
Specification limits, key impurity
concentrations and, 19
Steam
constraint of and system
optimization, 67–68
excessive use of, 62–63
Steam flow rate. See also Boilup
measurement of in distillate
control scheme, 35
temperature control with, 38–40
Steam/feed ratio
establishment of separation
power base with, 36, 38
expert system rules and
optimization of, 65–66
Step changes, trial-and-error tuning
and, 82
Streams, flow rates of, 8
Stripping, 20, 39
mass transfer constraint, 47–50
measuring quality performance
of, 58
stages and liquid mass transfer
units for, 49
Stripping factor, 47–50
rectification, 50–53
Sustained cycling, 83
T
Temperature
change in from D/F shift, 27–29
control with boilup, 38–40
control with distillate flow rate,
34–37
control with reflux flow rate,
37–38
gradient per theoretical stage,
26–27
Theoretical stages
calculation of for rectification,
50–53
calculation of for stripping, 48
energy consumption and the
number of, 18
Fenske equation for determining
number of, 17

separation power with, 16

temperature gradients and,
26–27
Total material balance, 24
Total reflux, 10
energy consumption and, 18
manipulated distillate control
scheme and, 36
mole percent of cyclohexane in
liquid and vapor at, 16
separation power with multiple
stages at, 16–18
Tray efficiency, vapor traffic and,
46
Tray temperature gradient method,
27–29
Tray temperature in distillation
columns, effect of on
quality, 61–62
Tuning of control loops
effect of integral action, 93–99
effect of proportional gain,
90–93
internal model control (IMC)
rules, 113–114
oscillating, 84–85
pattern recognition, 86–90
quarter decay ratio, 85–86
quarter decay ratio rules, 112
trial-and-error, 81–82
ultimate gain, 82–84
Ziegler–Nichols rules of thumb,
107–110
Two-point Smith method, 110–112