Controller Tuning and Disturbances

All of these systems have some common control loops. The system pressure is controlled by manipulating the fresh feed of A (F0A). The concentration controller with ratio control is used to control reactor inlet gas composition by manipulating the fresh feed of B (F0B). Bypassing (Fhy) around the FEHE is used to control gas mixture temperature Tmix. Reactor inlet temperature (Tin or T ) is controlled by manipulating the furnace heat input QF. The setpoints of these two temperature controllers are the same, and the controller output signals are split-ranged so that bypassing and furnace heat input cannot occur simultaneously. 

The liquid level in the flash drum is controlled by manipulating liquid product Lc. A temperature controller manipulates heat removal in the condenser to hold drum temperature constant. Compressor speed is controlled, which is assumed to fix the recycle gas flowrate FR. 

Perfect control is assumed for the composition/ratio controller, level controllers, gas condenser temperature controller, and speed controller. 

Ziegler-Nichols (ZN) and Tyreus-Luyben (TL) PI tunings are evaluated. Ultimate gain and frequency are obtained by performing relay-feedback tests. Temperature control loops have three 20-s lags. The pressure control loop has two 30-s lags. There is a 

TABLE 6.3 Controller Tuning for Single-Stage Adiabatic Reactor System 

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