Process Intensification in Multicomponent Distillation

Authors: 
Agrawal, R., Purdue University
Jiang, Z., Purdue University
Tawarmalani, M., Purdue University
Process intensification (PI) is an emerging concept which describes the design innovations that lead to significant shrink in size and dramatic boost in efficiency in a process plant. Distillation, which accounts for 90-95% of all separations in a chemical plant and ~3% of the world’s energy consumption, is therefore a crucial component in PI. In the context of multicomponent distillation, we believe that PI stands for minimizing the number of pieces of equipment as well as total cost while maintaining high efficiency through innovative process synthesis. This will lead to compact, easy-to-operate, energy efficient and cost effective processes. Here, we consider several different levels of PI in multicomponent distillation, including: 1) Introducing thermal couplings that eliminates some or all reboilers and condensers to save energy and reduce capital cost; 2) Using thermal couplings strategically by identifying places where heat exchangers that use intermediate temperature utilities should be kept to enhance thermodynamic efficiency, as well as places where thermal couplings are preferred in order to provide substantial energy savings but incur no or minimal penalty in utility; 3) Performing simultaneous heat and mass integration among thermally coupled distillation columns to reduce the number of columns and heat duty requirement; 4) Conducting any thermally coupled distillation in only one single column shell using the form of a dividing wall column that is fully operable; 5) Being able to systematically derive numerous configurations that use 1 to (𝑛−2) column shells from a traditional (𝑛−1)-column configuration. Here, we demonstrate these aspects of PI through examples, illustrating the importance of PI in multicomponent distillation and how this concept can be utilized by process engineers to design cost effective and energy efficient distillation systems.