Energy saving of side-column DWCs for quaternary separation

• Side-column DWC processes quaternary mixture.
• Single column construction is available.
• Energy savings between 8.5% and 10.8% are yielded.
• Utility cost savings are 6% and 12.9%.
• Commercially proven DWC is utilized.

Side-column DWCs (divided wall columns) are proposed for the energy saving from the conventional three-column distillation system. The proposed columns are energy-efficient and compact to be installed in small construction space. The energy requirement, economics and thermodynamic efficiency of the side-column DWCs are evaluated and compared with the conventional system. Two example processes, the BTX and aliphatic compound mixture processes, are utilized for the evaluation. The heating and cooling duties of the side-rectifier DWC for the BTX process are 8.5% and 9.1% less than the conventional system, respectively. Those of the side-stripper DWC for the aliphatic compound mixture process are 10.2% and 10.8% less, respectively. The economic evaluation indicates that both side-column DWCs require slightly more investment cost than the conventional system, but their utility costs are 6% and 12.9% less than the conventional system for the BTX and aliphatic compound mixture processes, respectively. While the thermodynamic efficiency of the BTX process is 0.4% point higher than the conventional system, the efficiency of the aliphatic compound mixture process is 0.3% point lower. The characteristic of the side-column DWCs is explained to improve the column design, and the operational difficulty is examined to indicate the improvement from the existing DWC.