Control of Dividing-Wall Columns via Fuzzy Logic

Abstract

Because of their potential energy savings, dividing-wall columns (DWCs) have been viewed as an interesting alternative to the use of sequences based on conventional distillation columns. The energy savings, however, must be supported by suitable controllability properties for a proper operation. In this study we use a design methodology to optimize the gains of the Takagi−Sugeno fuzzy controller and show its implementation for the control of a DWC. Comparison with optimal proprotional−integral−derivative (PID) controllers was carried out to further analyze the performance of the proposed controller under load disturbances in feed composition and set point changes. The case studies considered here are the separation of pentane−hexane−heptane and the industrially relevant separation of benzene−toluene−xylene. The results show that the fuzzy controller provides a suitable option for DWC control and that it produces improved control performance with respect to the conventional PID controller.

Dividing-Wall Column Design: Analysis of Methodologies Tailored to Process Simulators

“…where V Petlyuk T,min is the vapor flow at the top and V Petlyuk B,min is the vapor flow at the bottom of the column. It should be noted that the value of q affects the solution of the Underwood equation from Equation (2) and not only by the term (1 − q) F [24]. The Vmin diagram reported by Halvorsen and Skogestad [24] for Petlyuk columns is a useful tool, as detailed vapor flow requirements can be identified directly from such a diagram.…”

“…Separations of multicomponent chemical mixtures have been carried out mainly in distillation columns trains. Ternary mixtures in particular have received special attention in the literature [2][3][4]. Conventional separation of ternary mixtures can be done by direct and indirect sequences (Figure 1).…”

Analysis of Multi-Loop Control Structures of Dividing-Wall Distillation Columns Using a Fundamental Model

“…Table 1 gives the mixtures investigated in this work, along with their ESI values. A mixture of n-pentane (nC 5 ), n-hexane (nC 6 ), and n-heptane (nC 7 ), which has been used in several studies from the literature [22,23,37] (with an ESI value of approximately 1.0), serves to illustrate in detail the procedure used for design and control. The results for the other mixtures are summarized in Section 4.…”

“…Ling and Luyben [18] used a sequential methodology to tune the Proportional-Integral (PI) controllers. Other authors have used different tuning methodologies and techniques, e.g., tuning based on minimizing convergence indices [22,23]. IMC tuning of PI/PIDs has also been considered to control hypothetical ternary systems in DWCs [24,25].…”

Controllability Analysis of Distillation Sequences for the Separation of Bio‐Jet Fuel and Green Diesel Fractions

“…Strategies have also been proposed to control DWC by measuring impurities in the product streams instead of the purities of the desired products 15. Recently, advanced control strategies for the control of thermally coupled systems have been proposed, such as model predictive control 16–18 and fuzzy control 19, among others. Also recently, Ramírez‐Corona et al 20 presented a control analysis of thermally coupled distillation columns, considering not only the isolated equipment but the interactions with whole processes.…”