Towards energy efficient distillation technologies - Making the right choice

In spite of claiming around half of the operational costs of chemical plants, distillation is still the most popular separation technology. Distillation has low thermodynamic efficiency, requiring the input of high quality energy in the reboiler - while rejecting a similar amount of heat at lower temperature, in the condenser. Several heat pump concepts have been proposed to upgrade that thermal energy and reduce the consumption of valuable utilities. Under certain conditions, the energy savings of heat pump assisted distillation is usually around 20-50%. This study proposes a novel selection scheme of energy efficient distillation technologies, with a special focus on heat pumps. The most promising technologies selected are vapor compression, mechanical or thermal vapor recompression, absorption, compression-resorption and thermo-acoustic heat pumps, multi-effect distillation, heat integrated distillation column, cyclic distillation, Kaibel and dividing-wall column. The scheme considers as the main selection criteria the type of separation tasks, product flow and specifications, operating pressure, difference in boiling points, reboiler duty and its temperature level. Moreover, this scheme is very practical, allowing major time and resources savings in the design of eco-efficient processes. (C) 2012 Elsevier Ltd. All rights reserved.