Studies of the externally heat-integrated double distillation columns (EHIDDiC)

In terms of the separation of an ideal binary mixture of hypothetical components A and B, the synthesis and design of the externally heat-integrated double distillation columns (EHIDDiC) are studied under the assumption of a constant pressure elevation from the low-pressure (LP) to the high-pressure (HP) distillation columns involved. It is found that employing one to three external heat exchangers can be a reasonable design option for the EHIDDiC. When multiple external heat exchangers (e. g. more than three external heat exchangers) have been adopted, the process configuration must be carefully determined because the increase in the number of stages externally heat-integrated might not necessarily be beneficial to the system performance in this situation. This phenomenon has been caused by the strong mass and heat coupling between the HP and LP distillation columns involved and reflects also the unique characteristic of the EHIDDiC. For the reduction of capital investment, the total external heat exchange areas should be installed through as small a number of heat exchangers as possible and the extreme situation comes to the employment of a single external heat exchanger, thereby requiring subtle wisdom in arranging the total heat transfer areas between the HP and LP distillation columns involved. These insightful findings are of great significance to process synthesis and design. In addition, a novel decentralized control scheme is proposed for the operation of the EHIDDiC. (C) 2011 Curtin University of Technology and John Wiley & Sons, Ltd.