Design and 4E analysis of heat pump-assisted extractive distillation processes with preconcentration for recovering ethyl-acetate and ethanol from wastewater

Abstract

The separation of ternary azeotropes with a high content of one component using extractive distillation is energy intensive, and the introduction of preconcentration can significantly improve process economy. In this paper, the conventional three-column extractive distillation (TCED), four-column extractive distillation (FCED) with preconcentration, and three-column extractive distillation with integrated distillation column (TCED-IDC) are established and economically optimized to minimize the total annual cost (TAC) for recovering ethyl-acetate (EAc) and ethanol (EtOH) from wastewater containing a large amount of water. The preconcentration and solvent recovery functions can be integrated in IDC. Following that, the vapor recompression heat pump (VRHP) is introduced to further reduce energy consumption for the TCED-IDC process. The two VRHP-TCED-IDC processes are correspondingly designed. Simultaneously, the processes proposed are evaluated in terms of economy, energy consumption, environment and exergy destruction (4E analysis). The environmental analysis is performed via calculating Global Warming Potential (GWP) index using Life Cycle Assessment method. The two VRHP-TCED-IDC processes demonstrate superior performances with regard to 4E analysis. The most efficient VRHP-TCED-IDC process reduce over 32.0 %/16.0 %/6.8 % of TAC, 53.4 %/42.4 %/33.7 % of energy consumption, 62.0 %/53.0 %/45.9 % of GWP, and 49.7 %/35.7 %/29.3 % of exergy destruction compared to the TCED/FCED/TCED-IDC processes, respectively.