Design and control of dual condensers in distillation columns

Most distillation columns use water-cooled condensers cooling water that is inexpensive. With cooling water supplied at 305 K, a reflux-drum temperature of 322 K is normally used for column design. This temperature and the distillate composition set the require column pressure. aper demonstrates that the use of refrigeration in a second condenser in series with the primary water-cooled condenser has economical advantages in some separations. The dual-condenser process can be less expensive than the single-condenser process in cases in which a lighter-than-light-key component is present in the feed and in which the separation between the key components is difficult (low relative volatility systems). Using a small refrigerated condenser permits the column to operate at a lower pressure, which reduces reboiler duty enough to compensate for the small amount of refrigeration required. namic control of the dual-condenser process is also studied, and an effective control structure is developed.