How to Reduce Energy Consumption in Distillation

Distillation is one of the most energy-intensive separation processes used in chemical plants, and separates components by their boiling points in multicomponent mixtures. Distillation has a significant impact on overall energy usage of chemical plants.

Energy requirements of distillation columns depend on both reboiler heat duty (which represents the major energy usage), and condensation heat recovery at the condenser (which has less of an impact). There are various strategies available to reduce energy consumption when distilling, including:

An incorrect feed location on a multicomponent distillation train can drastically increase reflux/boil-up ratio and therefore energy usage. An ideal feed location would be one in which composition of internal liquid traffic (column internal liquid traffic) and feed stream is as similar as possible to prevent large differences between composition gradients between streams.

Distillation energy savings strategies center around optimizing the reboiler or column’s separation performance, such as changing its configuration for multicomponent distillation trains to alter composition or concentration profile of internal liquid traffic or concentration profile; thoughtful use of side draws may further lower energy usage in multicomponent columns.

Distillation column control is key to optimizing overall energy consumption, according to Pete. An ideal system needs to reduce the integral error between actual and desired trajectory of a process without compromising plant robustness or operability – something achieved using advanced PID controllers or model predictive control, but unfortunately these aren’t widely available yet in industrial markets. Companies using SmartProcess control have achieved 40-80% variability reduction, 5-10% throughput increase, 5-10% energy cost savings, less off-spec / rework and improvements in safety/environmental metrics