Energy-saving heat pump-assisted extractive-azeotropic dividing wall column with heat exchanger network for separating acetonitrile and water: A techno-economic and inherent safety investigation

Abstract

In the present paper, a new extractive-azeotropic dividing wall column configuration is designed to recover acetonitrile from wastewater instead of the conventional two-column process. Although the performance of energetic and economic savings is enhanced in the dividing wall column, it is still characterised by high energy consumption. To this end, a methodical framework for designing energy-efficient intensified dividing wall columns is developed to gradually reduce the need for utilities. Results indicate that the reboilers of the extractive-azeotropic dividing wall column can be entirely replaced by the applications of vapour recompressed heat pump and heat exchanger network, which comprehensively improves the energy-saving performance. A multi-criteria evaluation of process sustainability, including energy consumption, total cost, environmental performance, energy efficiency, and inherent safety analysis, is performed among the designs. Results show that the heat-integrated extractive-azeotropic dividing wall column process is inherently safer than the conventional two-column process and reduces at most 51.95%, 89.96%, and 63.58% in total annual cost, CO2 emissions, and total energy consumption, respectively.