Efficient optimization-based design of energy-intensified azeotropic distillation processes

Abstract

The separation of azeotropic mixtures is a difficult task in the downstream processing of many industrial processes. Although potentially less energy intensive separation techniques are available, the separation by extractive or heteroazeotropic distillation is often the method of choice, particularly for large scale processes. By application of different concepts for energy-intensification such as heat integration, the use of heat pumps or concepts of thermal coupling the separation efficiency of these thermal separation processes can be improved. However, the comparison of these different variants and the identification of the most energy or economicly beneficial option for a specific separation is an elaborate task. Therefore, an existing approach for the design of energy-intensified distillation processes has been extended to the design of extractive and heteroazeotropic distillation. The method utilizes a superstructure model based on the MESH equations including non-ideal thermodynamics. All considered process variants are evaluated by means of an automated procedure requiring nothing more than the definition of feed and product specifications as well as the thermodynamic model. The method is demonstrated for the dehydration of ethanol with the help of additional mass separating agents. While the investigated case study shows only small saving potential by the considered means of energy-intensification, it demonstrates the computational efficiency of the proposed design approach. Moreover, the method can easily be adapted for other separation tasks, requiring only minor changes.