Are Thermally Coupled Distillation Columns Always Thermodynamically More Efficient for Ternary Distillations?

Abstract

The thermodynamic efficiency of five ternary distillation configurations to distill ideal saturated liquids into pure product streams are calculated and compared. A striking result of this study is that for the fully coupled column (Petlyuk) configuration, which is known to have the lowest heat demand for ternary distillation, the range of values of feed composition and relative volatilities for which it is the most thermodynamically efficient configuration is quite limited. Among the three thermally coupled column configurations, the side-rectifier and side-stripper configurations tend to provide the most efficient configuration more often than the fully coupled configuration. Generally, the modified direct and indirect split configurations together provide the most thermodynamically efficient configuration for more feed compositions and relative volatilities than do the three thermally coupled column configurations. The high thermodynamic efficiency of these two configurations is primarily due to their ability to either accept or reject heat at the intermediate temperatures of binary mixtures.

Optimal synthesis of thermally coupled distillation sequences using a novel MILP approach

“…Despite its wide use and functionality it is a very energy intensive method of separation, accounting for about 40% of the total energy used in the chemical and petroleum refining industries (DOE, 2005). To this end, the thermally coupled distillation (TCD), in which heat is directly transferred between columns through two streams (liquid a vapor) that substitute a condenser or a reboiler (See Figure 1), has received considerable attention, with savings in total cost between 10 and 50%, when compared to the traditional approach, where simple columns are employed in series to achieve the desired product purities [1][2][3][4][5][6]). …”

“…In the condenser this fact is especially relevant if the most volatile component must be condensed at sub-ambient temperature preventing the use of cooling water. (2) In FTC systems the minimum vapor flow is that of the most difficult separation [5,6]. The thermal couples transfer the vapor between columns and, therefore, some column sections could have large diameters.…”

“…Some of them, without the intention of a comprehensive review are: modification in the number and characteristics of vapor and liquid transfer between columns [60,61]; Simultaneous design of thermally coupled and heat integrated systems [12,[62][63][64], thermodynamic analysis [2,5,6,[65][66][67], generation and analysis of sequences with reduced number of column sections [68][69][70][71], alternatives for columns with one or multiple walls [72,73].…”

Simplified Methodology for the Design and Optimization of Thermally Coupled Reactive Distillation Systems

“…Thermal coupling is among these approaches. The increase of the thermodynamic efficiency when thermal coupling is incorporated depends on the nature of the mixture, 1 but in general, thermally coupled systems have higher thermodynamic efficiencies than conventional distillation sequences. 2 Thermal coupling implies the use of column configurations to avoid remixing.…”

Distillation of a Complex Mixture. Part I: High Pressure Distillation Column Analysis: Modeling and Simulation

“…The synthesis of processes of complex mixtures distillation is very significant for an optimal design. Indeed, due to the complex interactions between components in the mixture, the research has been focused on ternary mixtures [10]. Reversible distillation of ternary mixtures implies a consequent minimization of the potential difference of transfer (mass and heat) at the tray level.…”