Application of three dimensional exergy analysis curves for absorption columns

This paper presents the application of three dimensional exergy analysis curves method to absorption column, which is the second most important separation technique in industries after distillation. A three dimensional graphical correlations of exergy lost to the ratio of liquid and gases molar flow (Lm/Gm), number of stages (N) and stage efficiency (η) inside the column is presented at different operating states of an absorption column. The curves provide visualization on the effect of design and operating parameters to the exergy lost of an absorption column. A case study on the recovery of sulfur dioxide was carried out to demonstrate the application of this method. It was found that the three dimensional exergy analysis curves method is useful in not only identifying the magnitude of exergy lost in absorption column but also providing direction on how the losses can be minimized while maintaining the required process specification. Results suggested that the absorption column should be operated with (Lm/Gm) ratio approaching minimum while maintaining the required recovery of sulfur dioxide. In addition, exergy lost of absorption column can be decided with two degrees of freedom. Consequently, the method is useful to guide engineers to make insightful decision on the optimum design and operating parameters at minimum exergy lost.

► A new exergy analysis method to optimize absorption process is presented.
► Exergy lost of absorption column is determined with two degrees of freedom.
► Exergy lost can be controlled by manipulation of (Lm/Gm) ratio.
► The (Lm/Gm) ratio is a function of stage efficiency and number of stages.