Journal of Chemical Engineering of Japan, Vol.45, No.10, 840-849, 2012
Energy Conservation of a Multi-Effect Distillation Column with Internal Heat Integration
An energy-efficient distillation column using internal heat integration is proposed, and its energy saving performance and thermodynamic efficiency are compared with those of a conventional distillation column. The proposed column has three identical columns, with each handling one-third of the feed for a conventional binary distillation column, and two heat integrations are installed among them for the heat recovery. Applying different operating pressures, the heat integration among the columns is possible without vapor compression, of which the utilization is a main obstacle for the practical implementation of the existing internally heat-integrated distillation column (HIDiC). The performance comparison between the proposed and conventional systems indicates that the former requires 35.2% less reboiler duty and 36.8% less condenser duty compared with the latter for the benzene-toluene process and 29.2% less heating duty and 29.8% less cooling duty for the methanol-ethanol process. The thermodynamic efficiencies of the proposed and conventional systems are close for the benzene-toluene process. However, the efficiency of the proposed system in the methanol-ethanol process is lower than the conventional system due to the large enthalpies of the feed and products. Because the proposed system does not utilize a compressor, the difficulties accompanying the field application of the existing internal heat-integrated distillation system are eliminated. The operation and control of the proposed system are similar to those of the conventional binary column due to the separate reboiler and condenser attached to each of the three distillation columns.
Keywords:Heat-Integrated Distillation;Energy-Efficient Distillation;Internal Heat Integration;Dual Heat Integration;Binary Separation