λ jacket << λ reactor
More-advanced tools are helpful for some situations. If the temperature process response has elements of both self-regulating and integrating dynamics, a different tuning rule is needed. When there’re significant nonlinearities in the control logic (for example, the SP limiter block in Figure 1), a nonlinear computer simulation can accelerate finding the best controller parameters — today’s control systems come with built-in simulation tools. In some cases a Fuzzy Logic Controller (FLC) can give control superior to PID. When there’s no jacket but only electrical heating of the reactor, the FLC can provide the fastest possible heating of the reactor with no overshoot or oscillation. Again, the modern control system makes it easy to install this controller.
Achieve better control
Some plants have experienced oscillatory or sluggish response of batch reactor temperature. This can be caused by the integrating process response, limitations in the control system and lack of training. With a modern control system, a plant can set up the controllers to give fast set-point response without overshoot or oscillations. This offers the opportunity to maximize product quality, minimize batch cycle time and eliminate utilities waste — all positive impacts on your plant’s profitability.
Mark Coughran is a senior process control consultant for Emerson Process Management, Austin, Texas. E-mail him at Mark.Coughran@Emerson.com.
- Process Control and Optimization, Volume VIII in “Instrument Engineers’ Handbook,” p. 1,664, 4th ed., B.G. Liptak, ed., CRC Press, Boca Raton, Fla. (2007).
- Boudreau, M.A. and G.K. McMillan, “New Directions in Bioprocess Modeling and Control,” p. 91, ISA, Research Triangle Park, N.C. (2007).
- Bialkowski, W.L., in “The Control Handbook,” p. 1,234, W. Levine, ed., CRC Press, Boca Raton, Fla. (1996).