Two-Point Temperature Control Structure and Algorithm Design for Binary Distillation Columns

• Published in: Industrial & engineering chemistry research 2005-01, Vol.44 (1), p.142-152
• Main Authors: Castellanos-Sahagún, Eduardo, Alvarez-Ramírez, José, Alvarez, Jesús
• Format: Article
• Language: English
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie0401096

In this paper the problem of designing a two-point linear temperature controller for the regulation of the product compositions in binary distillation columns is addressed. The combination of feedforward, feedback, and internal model control concepts yields a control design methodology with (i) criteria to choose the (decentralized and one- or two-way) decoupling structure and the temperature measurements location, (ii) a linear control system that consists of a static interaction compensator and a pair of decoupled proportional−integral controllers with feed-temperature-based setpoint adjustment, (iii) an implementation that requires the static dependencies of the measured tray temperatures on the feed temperature, the slopes of the operating lines, and the temperature-gradient-to-holdup quotients in the measurement trays, and (iv) a conventional-like tuning scheme that resembles the ones employed in linear first-order controllers and filters. The linear controller recovers the behavior of a material-balance-based feedforward−feedback nonlinear controller. The proposed design is applied to two representative examples through simulations, in the presence of holdup dynamics, nonideal thermodynamics, and actuator errors, as well as measurement delays and lags.