Systematic design of energy efficient distillation column for alcohol mixture

Abstract

When designing a separation system for mixtures containing close boiling point components, ordinary distillation can be considered not feasible since high purity products require large number of stages and reflux ratio. During the design phase of distillation processes, 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 alcohol 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 5 component alcohol mixture from a literature was selected and investigated. Initially, the literature case study was analysed and simulated by using Aspen HYSYS V9’s shortcut design method to determine the energy usage and capital cost. Then, similar feed information from the shortcut 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. Both designs were simulated using similar thermodynamic model (RK-Aspen) to ensure reliable data for comparison purposes. 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 12.25 % and operation cost up to 9.39 %. The performance confirms that by using this methodology, optimum or near optimum design for alcohol distillation process can be developed in an easy, practical, and systematic manner.