Abstract
A new method for graphic exergy analysis of multicomponent distillation and for visualization of rate characteristics of a distillation column is proposed by applying an energy-utilization diagram, EUD. By introducing the concept of a premixing model, the exergy losses in a distillation column can be decomposed into losses caused by premixing in liquid phase and those caused by premixing in vapor phase. Also, the energy exchange in a phase change such as condensation or evaporation of each component is displayed individually. By introducing the concept of partial molar quantities, those exergy losses in liquid phase and vapor phase can be categorized into losses caused by heating and mixing in liquid phase and losses caused by cooling and mixing in vapor phase. To use this method, the energy exchanged (ΔHea) and the energy levels (Aed and Aea) are displayed systematically on EUD.
As a case study, simulation of the separation of n-hexane, n-heptane and n-octane is conducted for a column with 11 plates. The effect of reflux ratio and side-cooling or side-heating is discussed by using EUDs.
