Energy-Efficient Extraction-Distillation Process for Separating Diluted Acetonitrile-Water Mixture: Rigorous Design with Experimental Verification from Ternary Liquid-Liquid Equilibrium Data

In this paper, an energy-efficient extraction-distillation process to separate diluted azeotropic acetonitrile-water mixtures is newly developed. Compared with the conventional azeotropic separation methods (i.e., extractive distillation), the potential dominant benefit of this proposed method is that the main separation task can be achieved by an extraction column without needing reboiler duty. In this work, an efficient solvent of n-propyl chloride is proposed to extract the organic compound into the extract phase and to let water remain in the raffinate phase. Ternary liquid-liquid equilibrium experiments are also conducted to verify the separation performance in the extraction column and decanter of the proposed process. It is found that significant savings of 40.3% in steam cost and 34.7% in total annual cost can be obtained by the proposed separation method as compared to that of a three-column extractive distillation system published in open literature.