For the systematic diagnosis of the thermodynamic efficiency in dual column distillation with heat integration of practical modes, a computing scheme is developed in conjunction with the method of calculation of exergy and the modularized reduced-order model, which are discussed elsewhere by the present authors[1,2]. The thermodynamic efficiencies of 9 types of heat integration modes are actually calculated and compared with that of a distillation column without heat integration using 3 different kinds of hydrocarbon mixtures, i. e., tertiary, quaternary, and octanary.
The results show that the separation energy demand can be reduced by 15% when single heat integration through the reboiler of the first column is made, and about 20% when dual integration through the condenser and the reboiler of the first column is made.