in Wiley InterScience (www.interscience.wiley.com).We describe a simple-to-use ''matrix'' method for obtaining all the basic distillation configurations and additional thermally coupled configurations that separate a zeotropic multicomponent feed into essentially pure product streams. This provides an opportunity to rank-list the configurations for a given application subject to criteria of interest. The only information needed to generate the configurations is the number of components in the feed. We have successfully enumerated all the configurations for feeds containing up to eight components. The method can also be used to generate nondistillation and hybrid separation configurations, and even easy-to-retrofit configurations. We illustrate the use of this method by applying it to the highly energy-intensive problem of petroleum crude distillation. We have identified more than 70 new configurations that could potentially have lower heat duty than the existing configuration. A significant number of these could reduce the heat demand by nearly 50%.
We present a general Global Minimization Algorithm (GMA) to identify basic or thermally coupled distillation configurations that require the least vapor duty under minimum reflux conditions for separating any ideal or near‐ideal multicomponent mixture into a desired number of product streams. In this algorithm, global optimality is guaranteed by modeling the system using Underwood equations and reformulating the resulting constraints to bilinear inequalities. The speed of convergence to the globally optimal solution is increased by using appropriate feasibility and optimality based variable‐range reduction techniques and by developing valid inequalities. The GMA can be coupled with already developed techniques that enumerate basic and thermally coupled distillation configurations, to provide for the first time, a global optimization based rank‐list of distillation configurations. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2071–2086, 2016
Nonazeotropic multicomponent mixtures are often separated into products by distillation configurations containing multiple distillation columns. One method of calculating the minimum vapor duty of a configuration is to sequentially calculate the minimum vapor duty of each mixture as it is split into two streams within a given column starting from the feed column. The other method simultaneously manipulates all the splits to yield the overall minimum vapor duty of the entire configuration. Of these two methods, the sequential minimization is attractive as it can be analytically solved. However, through extensive computations, we find that the sequential minimization method is not a valid substitute for the simultaneous minimization method. As the number of components in the feed increases, the fraction of the basic configurations for which sequential method yields a reasonable estimate decreases rapidly, thereby emphasizing the need for a more robust and reliable global optimization algorithm. © 2012 American Institute of Chemical Engineers AIChE J, 59: 971–981, 2013
An easy‐to‐use matrix‐based method for the systematic synthesis of distillation configurations using less than n‐1 columns to separate any zeotropic n‐component feed into n product streams is described. The method is easily extended to obtain additional thermally coupled configurations. The only information needed to generate the configurations is the number of components in the feed, or equivalently, the number of distinct composition final product streams. We have successfully enumerated configurations for feeds containing up to eight components. This has resulted in a large number of hitherto unknown configurations even for four‐component separations. Some of the novel configurations generated using the method have substantially lower heat duty than the previously known fewer column configurations for a four‐component feed separation. Therefore, it is essential to include these novel configurations in the search space to find the optimal distillation configuration with fewer columns for a given application. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2479–2494, 2012
Thermal coupling links between multicomponent distillation columns are known to reduce the total heat duty and, therefore, the first-law energy demand of distillation configurations. Most studies on the energy savings of thermally coupled configurations have focused on cases where all thermal coupling links of a configuration have been used. We show that certain types of thermal coupling links of a configuration actually do not contribute to the first-law energy savings. Furthermore, it is often believed that the first-law energy savings due to thermal coupling links always has associated second-law temperature-level costs due to increased utility demand at extreme temperatures. However, we demonstrate that some types of thermal coupling links provide first-law energy savings without exhibiting any second-law temperature-level penalties. Finally, we present heuristics to enable quick identification of such thermal coupling links.
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