Nonsharp split can improve the thermodynamic efficiency of the distillation system due to its avoidance of the remixing effects which are inherent to sharp split. Based on the Data Structure Theory

a method is introduced to synthesize and optimize the nonsharp complex distillation sequences. For an N-component mixture separation

the distillation sequences is comprised of N-1 columns

the nonsharp splits of which contain an arbitrary number of middle components. In order to synthesize the separation sequences above

the weighted directed digraphs can be applied to establish a new model which is suitable for the distillation columns. Additionally

based on the dynamic array “vector”

a storage structure of the weighted directed graphs

which combines the advantages of arrays and chain tables

is proposed. A series of operations are defined in the synthesis procedure and the breadth-first strategy is chosen to improve the synthesis efficiency. An example problem is solved to illustrate the high efficiency of this method. The results show that the optimal sequence of the example problem can effectively reduce investment cost and energy consumption.