Logic Based Algorithms for the Rigorous Design of Thermally Coupled Distillation Sequences

This paper presents an algorithm for the rigorous design of thermally coupled distillation sequences using process simulators. First we show that the two side streams connections that produce a thermal ‘couple’ can be substituted by a combination of a material stream and a heat flow. In this way, the sequence of thermally coupled distillation columns can be simulated without recycle streams. The problem can be divided in two levels. An upper level that basically deal with the existence or not of a given distillation column and a lower level dealing with the parameters of an existing columns (number of trays, feed tray position and operational conditions). Therefore, the problem is solved using logic based decomposition algorithm that takes advantage of the structure of the problem iterating between those levels.