Optimization Aspects for Reactive Batch Distillation.

On-line Optimizing Control for a Class of Batch Reactive Distillation Columns

“…The profit J (2) dependency on the accumulator product composition (c C a ), and results from previous RD column studies via open-loop optimization (Mujtaba and Macchietto, 1997;Giessler et al, 2001) suggest the consideration of the N-th tray vapor composition ν C (c N ) as regulated output at a fixed value z -(to be determined) smaller than the value z* asymptotically reached in total reflux regime. This is (rd := relative degree),…”

“…The column is operated as follows (Mujtaba and Macchietto, 1997;Giessler et al, 2001): at time t = 0, a mixture of m L moles at compositions c Ao , c Bo , and c Co of reactants A, B, and product C, is loaded, catalyst (H + ) is added, and heat is supplied at a constant rate Q ∈ [Q -, Q + ] set by equipment design and operation considerations. During the start-up period [0, t r ], the column is operated at total reflux (molar) rate (R = V N ) until a time t r when the product C reaches a certain purity.…”

“…In previous studies (Mujtaba and Macchietto, 1997;Giessler et al, 2001;Noeres et al, 2004), the optimal operation O (7) has been drawn by finding the set [Q, R(t), t r , t f ] that maximizes the profit J (2) subjected to the open-loop column dynamics (4), but it is unclear the connection with the feedback control design. Following the approach employed before in polymerization reactors (Alvarez et al, 2004a) and binary distillation columns (Alvarez et al, 2005), here the optimal motion problem will be addressed in terms of the closed-loop system with passive (robustness-oriented) SF control, with the understanding that optimal SF controllers are: (i) nonwasteful, (ii) inherently robust, and (iii) passive (relative degree less or equal to 1 and minimum phase) with respect to a certain output z (Sepulchre et al, 1997).…”

“…Most of the published works in RD have focused to continuous columns, and less attention has been given to the batch mode. While the open-loop operation design of batch RD columns has been successfully addressed via optimization techniques (Mujtaba and Macchietto, 1997;Giessler et al, 2001), the study of the associated tracking controller lags behind.…”

“…The proposed approach is illustrated with a case example (esterification of ethanol and acetic acid) through numerical simulations. The resulting closed-loop batch operation resembles to the open-loop ones drawn before (Mujtaba and Macchietto, 1997;Giessler et al, 2001) with standard optimization techniques for the process design part of the problem.…”