Novel heat-pump-assisted extractive distillation for bioethanol purification

Hao Luo, Costin Sorin Bildea, Anton A. Kiss

Research output: Contribution to journalArticlepeer-review

103 Citations (Scopus)

Abstract

The purification of bioethanol fuel involves an energy-intensive separation process to concentrate the diluted streams obtained in the fermentation stage and to overcome the azeotropic behavior of the ethanol-water mixture. The conventional separation sequence employs three distillation columns that carry out several tasks, penalized by high-energy requirements: preconcentration of ethanol, extractive distillation, and solvent recovery. To solve this problem, we propose here a novel heat-pump-assisted extractive distillation process taking place in a dividing-wall column (DWC). In this configuration, the ethanol top vapor stream of the extractive DWC is recompressed from atmospheric pressure to over 3.1 bar (thus to a higher temperature) and used to drive the side reboiler of the DWC, which is responsible for the water vaporization. For a fair comparison with the previously reported studies, we consider here a mixture of 10 wt % ethanol (100 ktpy plant capacity) that is concentrated and dehydrated using ethylene glycol as mass-separating agent. Rigorous process simulations of the proposed vapor recompression (VRC) heat-pump-assisted extractive DWC were carried out in AspenTech Aspen Plus. The results show that the specific energy requirements drop from 2.07 kWh/kg (classic sequence) to only 1.24 kWh/kg ethanol (VRC-assisted extractive DWC); thus, energy savings of over 40% are possible. Considering the requirements for a compressor and use of electricity in the case of the heat-pump-assisted alternative, it is possible to reduce the total annual cost by approximately 24%, despite the 29% increase of the capital expenditures, for the novel process as compared to the optimized conventional separation process.

Original languageEnglish
Pages (from-to)2208-2213
Number of pages6
JournalIndustrial and Engineering Chemistry Research
Volume54
Issue number7
DOIs
Publication statusPublished - Feb 25 2015

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Industrial and Manufacturing Engineering

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