7. Conclusions
In this article, the vapor recompression heat pump is introduced in the DWC column to reduce the heat irreversibility of distillation operation. There are two types of thermal coupling proposed under the VRC mechanism between the heat source and heat sink. They are the overhead vapor recompressed and the side vapor recompressed DWC. The former scheme operates the VRC at a very large CR because of its involvement between the two ends of the column. As a consequence, the OVR-DWC structure may not be so attractive proposition from industrial perspective, although it can show a better energy efficiency performance over the DWC-alone at the expense of an increased cost and complicated compression operation. On the other hand, in the SVRDWC configuration, the CR remains reasonably low because of its thermal pairing between the intermediate and bottom streams, which would lead to secure a remarkable savings. For the representative ethanol/water/ethylene glycol system, the DWC-alone shows a reasonable energy household and a better economic figure than the conventional two column system (CTCS). Further, it is observed that the OVR-DWC provides a better energy savings but a worse economic performance over the DWC-alone. Finally, it is investigated that the proposed SVR-DWC configuration is superior in the aspects of both energy consumption as well as payback time. Furthermore, the SVRDWC provides a reduced complexity in compressor operation over the OVR-DWC.
