Studies in chemical process design and synthesis: Part V: A simple heuristic method for systematic synthesis of initial sequences for multicomponent separations

Abstract

A simple heuristic method for the systematic synthesis of initial sequences for multicomponent separations is proposed and applied to a number of synthesis problems which have been solved previously using other methods. Based on reported costs, it is shown that the initial sequences synthesized for the test problems by the new heuristic method are cheaper than those obtained by other ordered heuristic methods. These initial sequences are also either identical to or at most a few percents higher in costs than those optimum sequences obtained by other algorithmic, heuristic-algorithmic and heuristicevolutionary methods. The new method is straightforward to apply by hand and it does not require any mathematical background and computational skill from the user. SCOPEAn important process design problem is the systematic synthesis of multicomponent separation sequences which is concerned with the systematic selection of the method and sequence for separating a multicomponent mixture into several products of relatively pure species. The general techniques which have been developed for solving the separation sequencing problem have included: algorithmic approaches involving some established optimization principles (e.g., Hendry and Hughes, 1972); heuristic methods based on the use of rules of thumb (e.g., Rudd et al., 1973, pp. 155-208); evolutionary strategies wherein improvements are systematically made to an initially created separation sequence (e.g., Stephanopoulos and Westerberg, 1976); and thermodynamic methods involving applications of thermodynamic principles (e.g., Hohmann et al., 1980). In some situations, two or more of these techniques have been used together in the synthesis (e.g., Seader and Westerberg, 1977). A review of previous studies on multicomponent separation sequencing can be found in Nishida et al. (1981).A disadvantage of many existing algorithmic and evolutionary techniques as reviewed by Nishida et al. is that their applications require special mathematical background and computational skill from the user. Although heuristic rules to guide the order of separation sequencing have long been available, many of the known heuristics contradict or overlap others; and procedures to resolve these conflicts have not been adequately developed. Recently, some success has been reported on the applications of certain heuristics together with evolutionary strategies for multicomponent separation sequencing (Seader and Westerberg, 1977; Nath and Motard, 1981).In this work, a simple heuristic method for the systematic synthesis of initial sequences for multicomponent separations is proposed. A comparison of the new heuristic method with other recent methods, particularly the heuristicevolutionary methods by Seader and Westerberg (1977) and by Nath and Motard (1981), is presented. A number of illustrative examples are given to demonstrate the simplicity and effectiveness of the proposed method. CONCLUSIONS AND SIGNIFICANCEThis work proposes and demonstrates a simple heuristic method for the systematic synthes...

Synthesis of mass exchange networks

“…Motard and coworkers (Mahalec and Motard, 1977;Nath and Motard, 1981;Lu and Motard, 1985) developed a computer methodology for synthesizing preliminary flowsheets, in which separation tasks are synthesized and cost estimated using a set of heuristic and evolutionary rules. Liu and his colleagues (Nadgir and Liu, 1983;Liu 1987;Cheng and Liu, 1988) proposed a simple-ordered heuristic technique for the preliminary synthesis of sloppy multicomponent separation sequences. They developed flexible and effective tools to represent the synthesis problem and to analyze the technical feasibility of separation tasks or product splits.…”

Design and synthesis of separation process based on a hybrid method

“…The rules selected for the separation point are according to the examples; different examples can use different rules. The rules [3] used in the example are listed in the following. Rule 1.…”

“…[2] Nadgir (1983) developed a simple-ordered heuristic method for the systematic synthesis of initial sequences for multicomponent separations. [3] Fair (1990,1993) provided a comprehensive set of rules for liquid and gas/vapor separations and demonstrated how to arrive at a design. [6] Douglas (1995) described how to consider a wide range of separation techniques in a hierarchical manner, emphasizing the interactions among the subsystems for gas/vapor, liquid, and solid separations.…”

Expertensysteme für die Verfahrenstechnik

“…Es handelt sich um eines der Gemeinschaftsprojekte des Tokyo Institute of Technology und der Firma Chiyoda Chemical Engineering and Construction [lo]. Das Expertenwissen besteht aus heuristischen Regeln nach [9]. Die Wissensbasis enthalt 28 Produktionsregeln, von denen jedoch nur neun die Trennprozesse betreffen.…”