NOVEL ENERGY-SAVING METHOD OF RECTIFICATION

The conventional rectification method to separate and purify chemical mixtures has the disadvantage of being an energy-intensive unit operation. The innovative method proposed in this article employs vapor and liquid recycles to the trays that in turn reduce the reflux rate and vapor boil-up rate, resulting in energy reduction without compromising the separations.

These findings were supported with examples of ethanol-water and butane- pentane system separations. With ethanol-water system, the experiments were conducted without overhead liquid recycle and using 16 and 5 vapor recycles. The energy saved was found to be 25–35% for 16 recycles and 20–30% for 5 recycles. Butane-pentane system was chosen as an example of industrial use of the proposed method. A liquid overhead reflux ratio of 0.5 (L/D) was used with vapor recycles, compared to a reflux ratio of 1.25 for the conventional separation without vapor recycles. This resulted in 30–35% saving in energy while giving the same productivity of the column. Butane-pentane separation was also simulated using a commercial process simulator (ASPEN^©PLUS).