TABLE 16.4 Tuning Parameters for Control Structure CS5 with Tray 20
Pairing Span KC
shows the response of the CS5 structure to these disturbances. Both controlled variables go back to their setpoints for both positive and negative disturbances in a short time. In addition, even for these very large +20% step changes, the purities of product streams xDC and xBD settle down smoothly to steady-state values that are within +1% of the 95% specification value. Therefore, the CS5 structure is a much better choice for controlling this column/side reactor process compared to the CS7 structure.
The responses of CS5 with the tray 20 composition controlled for changes in feed compositions are given in Figures 16.20 and 16.21. In Figure 16.20 the composition of fresh feed F0A is changed from pure A to either 95 mol% A with 5 mol% B (solid lines) or 90 mol% A with 10 mol% B (dashed lines). Control structure CS5 handles this type of
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