I n d . Eng. Chem. Res. 1994,33, 1878
1878
CORRESPONDENCE Comments on “Shortcut Procedure for Simulating Batch Distillation Operations” Urmila M. Diwekar Environmental Institute and Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
Sir: I am writing with reference to the article entitled “Shortcut Procedure for Simulating Batch Distillation Operations” (Sundaram, S.; Evans, L. B. Ind. E n g . Chern. Res. 1993,32,511-518). In the article, the authors present a shortcut procedure for batch distillation columns based on the Fenske-Underwood-Gilliland (FUG) method for continuous distillatiion columns. Citing the work of Diwekar et al. (1991),which described the same shortcut method in detail for the first time, Sundaram and Evans claim an independent and original development of the procedure. However, it should be noted that previous literature has not only described the shortcut method but also presented its applications to the various operating modes of batch distillation columns (Diwekar and Madhavan, 1986;Diwekar et al., 1987,1989,1991;Diwekar, 1988, 1991, 1992; Logsdon et al., 1990; Diwekar and Madhavan, 1991a,b). Also, these works are widely cited in the literature (see,for example,BosleyandEdgar, 1988; MujtabaandMacchietto, 1988;Logsdon et al., 1990,Bernot et al., 1993), and are unlikely to escape the attention of any systematic research effort. With reference to Diwekar et al. (1991),Sundaram and Evans claim that their paper differs “by formulating the model in a form that can be used convenientlyto simulate existing columns.” However, this claim remains unsubstantiated throughout the paper since the two formulations are identical. They both utilize the FUG method for continuous distillation columns as the basis and treat a batch distillation column as a continuous column with changing feed. Furthermore, the use of the shortcut method for simulating batch distillation columns was also introduced and described in several articles (Diwekar et al., 1987,1989; Diwekar, 1991; Diwekar and Madhavan, 1991b). Sundaram and Evans further state in the section on literature review that, in contrast to Diwekar et al. (19911, they present comparisons with rigorous simulations of batch distillation columns. However, the paper by Diwekar et al. (1991) also includes comparisons with the results of a rigorous simulation from BATCHFRAC, the same softwareused by Sundaram and Evans in their paper. In fact, Diwekar et al. (1991) even present comparisons with experimental data, which is lacking in the paper by Sundaram and Evans. Also, many of the systems considered in their case studies are identical to those in Diwekar et al. (1991), the only difference being the simulation stopping criteria.
Finally, the authors should be aware that the literature on the shortcut method for batch distillation columns has advanced beyond the case of ideal mixtures and constant reflux mode of operation of the columns, to address nonideal azeotropic mixtures, variable reflux operation modes, and optimal reflux operation modes. In fact, a generalized treatment of the various operatingmodes using the shortcut method has also been developedand validated (Diwekar and Madhavan, 1991a,b;Diwekar, 1991,1992). In summary,becauseof the points made above regarding the work of several earlier papers, it should be noted that the approach by Sundaram and Evans has been presented and validated in previously published literature.
Literature Cited Barnot, C.; Doherty, M. F.; Malone, M. F. Design and Operating Targets for Nonideal Multicomponent Batch Distillation. Ind. Eng. Chem. Res. 1993,32,293. Boeley, J. R.;Edgar, T. F. Effect of Model Simplification on the Optimal Solution of Batch Distillation Control Policy. Proceedings of ZFAC Worhhop; 1988. Diwekar, U. M. Simulation, Design, and Optimisation of Multicomponent Batch Distillation Columns. Ph.D. Thesis, Indian Institute of Technology, Bombay, India, 1988. Diwekar, U. M. An Efficient Design Method for Binary Azeotropic Batch Distillation Columns. AIChE J. 1991,37,1571. Diwekar,U. M. Unified Approach to Solving Optimal Design-Control Problems in Batch Distillation. AIChE J. 1992,38, 1551. Diwekar, U.M.; Madhavan, K.P. Optimization of Multicomponent Batch Distillation. Proceedings of World CongressZZZof Chemical Engineering; 1986; p. 719. Diwekar,U. M.; Madhavan, K.P. Multicomponent Batch Distillation Column Design. Znd. Eng. Chem. Res. 1991a, 30,713. Diwekar, U. M.; Madhavan, K. P. BATCH-DIST a Comprehensive Package for Simulation, Design, Optimization, and Optimal Controlof Multicomponent Batch DistillationColumns. Comput. Chem. Eng. 1991b, 15,833. Diwekar, U.M.; Malik, R. K.; Madhavan, K. P. Optimal Reflux Rate Policy Determination for Multicomponent Batch Distillation Columna. Comput. Chem. Eng. 1987,11,629. Diwekar, U.M.; Madhavan; K. P., Swaney, R. E. Optimization of Multicomponent Batch Distillation Columns. Znd. Eng. Chem. Res. 1989,29, 1101. Logsdon, J. S.;Diwekar, U. M.; Biegler, L. T. On the Simultaneous Optimal Design and Operation of Batch Distillation Columns. Chem. Eng. Res. Dee. 1990,68,434. Mujtaba, I. M.; Macchietto, S. Optimal Control of Batch Distillation. Proceedings of 12th IMAC World Congress, Paris, 18-22 July; 1988.
0888-5885/94/2633-1878$04.5~l0 0 1994 American Chemical Society
