Distillation Intensification by Simultaneously Enhancing both Mass and Heat Transfers
Special Symposium - EPIC-1: European Process Intensification Conference - 1
EPIC-1: Poster Session (EPIC - Poster) - P2
Keywords: Distillation intensification, mass & heat exchange network, thermal coupling, heat integration
Ben-Guang Rong* and Ilkka Turunen
Department of Chemical Technology, Lappeenranta University of Technology, P.O. Box 20, FIN-53851, Lappeenranta, Finland. *Tel: +358 5 6216113; Fax: +358 5 6212199; E-mail: benguang.rong@lut.fi
Process Intensification for novel distillation systems with the potential to substantially reduce both energy consumption and capital investment is a challenging task. However, it is a significant problem as distillation is widely used in process industry, and it needs both high energy consumption and large capital investment. Distillation is a typical process with simultaneous mass and heat transfers, the optimal synthesis of a distillation system must simultaneously maximum improve both the mass and the heat transfers efficiency. For a multicomponent separation, the final performance of the distillation system will depend on the optimum synergy of the multiple individual tasks for the enhancement of both mass and heat transfers within the distillation system, which is inevitably concerned with the simultaneous optimal synthesis of the mass and heat exchange networks.
For a multicomponent distillation, the traditional designs of simple column configurations use n-1 columns and 2(n-1) condensers and reboilers for an n-component separation. Each column implements one of the n-1 sharp splits for an n-component distillation. Such simple column configurations have the intrinsic separation inefficiency and suffer from both high energy consumption and large capital investment. To improve the separation efficiency, the sloppy splits can be used in the separation sequence, however, this will increase both the number of columns and the number of heat exchangers in the traditional distillation configurations. It is known that the number of columns and the number of heat exchangers (condensers and reboilers) in a distillation system represent not only the final equipment costs but also the installation costs in the final plant construction. Therefore, it is desired that the novel distillation systems could have the same or reduced number of both the columns and the heat exchangers than the traditional distillation configurations. Needless to say, if we want to improve the separation efficiency and simultaneously keep or reduce the number of columns and the number of heat exchangers, we must have the new method other than the traditional distillation configurations to coordinate the mass and heat transfers among the separation tasks.
The main objective of this work is to present a new method of simultaneous mass and heat exchange networks synthesis to design such novel distillation systems. A strategy of simultaneous thermal coupling and heat integration has been used to coordinate the mass and heat transfers. We found that thermal coupling and heat integration follow two different ways to deal with the heat exchangers which are concerned with both mass and heat exchange networks synthesis for a multicomponent distillation system. In certain cases, thermal coupling can enhance both mass and heat transfers by eliminating the condensers or reboilers. In other cases, heat integration is advantageous to enhance both mass and heat transfers by reducing both the number of heat exchangers and the number of columns. However, thermal coupling and heat integration must be simultaneously used to enhance the mass and heat transfers when a large number separation tasks are involved. The key in design of such novel distillation systems is by flexibly using thermal coupling and heat integration to determine the mass and heat exchange networks for the distillation systems. The mass and heat exchange network is for the determinations of the following concerned issues in synthesis of the novel distillation systems. 1) the number of individual splits, 2) the number of mass and heat transfer streams, 3) the number of heat integrations, 4) the number of thermal couplings, 5) the number of heat exchangers, 6) the number of columns. With different separation cases, some specific mechanisms are found which can determine the situations whether the thermal coupling or heat integration alone or simultaneously both to enhance the mass and heat transfers. The novel distillation systems have the distinct features in that they have different mechanisms to coordinate the intra-column and inter-column mass and heat transfers. The number of both columns and heat exchangers has been reduced and less than traditional configurations. In certain cases, they have the potential to significantly reduce both energy and capital costs, in other cases, they have better controllability and operability compared to traditional distillation systems.
The full paper includes a detail description of a systematic procedure for simultaneous mass and heat exchange networks synthesis to design the novel distillation systems. The economic performance and operability are also discussed between the novel systems and traditional distillation systems.
Presented Thursday 20, 13:30 to 14:40, in session EPIC-1: Poster Session (EPIC - Poster) - P2.
