Optimal side heating and cooling in a distillation column

One of the effective methods for saving energy in a distillation column is the use of side heating and cooling. This procedure provides the heat supply at a temperature lower than the reboiler temperature and heat removal at a temperature higher than the condenser temperature, both of which are advantageous from the second-law perspective. The purpose of this paper is to demonstrate the effects of side heating and cooling on separation performance. To treat the ideal case, it was assumed that every plate above the feeder plate releases heat with side cooling and every plate below the feeder plate accepts heat by side heating. It is shown that there is an optimum temperature profile based on both the separation performance and second law. The results are presented graphically by the use of an integrated energy-utilization diagram. (C) 1998 Elsevier Science Ltd. All rights reserved.