Systematic design of energy efficient extractive distillation column for azeotrope mixture

Abstract

The last dozen years produced so many articles on the synthesis of separation systems. For distillation systems, they can be divided into several types such as ordinary distillation and azeotropic distillation. When designing a separation system for mixtures containing azeotrope(s), ordinary distillation can be considered as not feasible since high purity products cannot be obtained. When designing a distillation based separation process, several problems may occur such as determination of optimal number of plates, optimal location for feed, and optimal reflux ratio. The main objective of this paper is to propose a methodology to design an energy efficient extractive distillation process using driving force approach. The design concept is to design the distillation column system at maximum driving force. At maximum driving force, the energy required for the system will be minimum. A case study of ethanol-water mixture from a literature was selected and investigated. Initially, the literature case study was analysed and simulated by using Aspen PLUS V9 to determine the energy usage and capital cost of the existing design. Then, the feed information from the existing design was used for a new design which was developed according to the driving force approach in the methodology. Optimum design variables were determined from the methodology. Since the literature case study used NRTL thermodynamic properties, similar package was used to ensure reliable data. Finally, both designs were analysed and compared in terms of capital and operating cost. Based on the findings, the capital cost was reduced up to 0.47 % and operation cost up to 7.61 %. Performance confirms that by using this methodology, optimum or near optimum design for extractive distillation can be developed in an easy, practical and systematic manner.