Systematic Energy Optimization and Design of Process Alternatives for Separation of Quaternary Azeotropic Mixtures

Abstract

The separation of homogeneous mixtures is an essential aspect of modern industrial processes that significantly relies on distillation operations. However, distillation has an elevated energy consumption and results in inefficiency in various cases. The non-ideal properties of certain mixtures render their separation unsuitable when employing a single distillation unit, increasing the necessary steps and energy requirements. Because of the relevant role of energy saving in sustainability, a systematic approach must be employed to select the most appropriate separation strategy and identify the operations that minimise energy requirements for product generation. This work employs a systematic approach that utilises residual curve maps to propose viable separation stages and determine the best separation sequence. Various separation strategies are identified via the P-graph framework, which identifies the n-best separation strategies and provides the designer with insightful information concerning the process and its performance. Such a methodology had been previously demonstrated for the separation of ternary mixtures; however, this work constitutes a first step in the development of a systematic approach for the separation of quaternary (or more complex) azeotropic mixtures. The range of separation options, including azeotropic distillation and extractive heterogeneous-azeotropic distillation, are identified by analysing the quaternary residual curves. The potential of this method is demonstrated through a case study involving a mixture of acetone, ethyl acetate, ethanol, and water. The initial set of structures comprises 37 alternative sequences for separation, out of which three interesting alternatives are discussed in detail. The case study demonstrates the potential of the method employed in assessing azeotropic distillation alternatives and facilitating informed decision-making for designers.