Heat integration controller tuning

The second column in Table 6.2 gives tuning parameters. The TC2 temperature controller is also retuned because of the somewhat small heat duty in the high-pressure column with partial heat integration. These tuning parameters are very similar to those found in the completely nonheat-integrated system, so we anticipate that control should be good. 

TABLE 6.1 Controller Tuning Parameters Full Heat Integration THF-Water. 

Ki tuning parameter for an integral controller Kp tuning parameter for a proportional controller JQ overall heat transfer coefficient... 

For noninteracting control loops with zero dead time, the integral setting (minutes per repeat) is about 50% and the derivative, about 18% of the period of oscillation (P). As dead time rises, these percentages drop. If the dead time reaches 50% of the time constant, I = 40%, D = 16%, and if dead time equals the time constant, I = 33% and D = 13%. When tuning the feedforward control loops, one has to separately consider the steady-state portion of the heat transfer process (flow times temperature difference) and its dynamic compensation. The dynamic compensation of the steady-state model by a lead/lag element is necessary, because the response is not instantaneous but affected by both the dead time and the time constant of the process. 

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