Role of total site integration in energy-target modification of distillation columns
This paper investigates the energy efficiency improvement of an industrial site through thermodynamic analysis of distillation columns together with the total site integration (TSI). Unlike the existing methods which consider the distillation unit exclusively, we study improvement options for the column while integrated to the background process. In fact, some of the improvement options proposed by single column analysis approach could appear inefficient in overall process integration and bigger savings can be identified while investigating the column attached to the process. The energy-target modifications of the column are performed by switching from actual temperature-enthalpy (T-H) profile into the ideal one while integrated to the background process. Based on the thermodynamic analysis, improvement options are proposed with different configuration of column by means of reflux ratio, feed conditions, side-reboiler in the stripping section and side-condenser in the rectifying section. In addition, heat pumping systems between intermediate stages and pressure modification are evaluated. The result emphasizes the importance of TSI in the energy-target modification. These modifications are in fact profitable in terms of total site energy saving, only when the column profile crosses the system pinch point. The application of the proposed methodology is demonstrated through an industrial case study highlighting different steps and the potential of the approach.