Design of an energy-efficient side-stream extractive distillation system

- Extractive distillation is the preferred method to separate azeotropic mixtures.
- Distillation is a major energy-consumer component in the chemical industry.
- Alternative distillation arrangements to minimize energy consumption have been developed.
- A novel side-stream extractive distillation system is presented.
- It is shown how the novel system is more energy-efficient than alternative distillation methods.

A novel extractive distillation system is presented. The proposed separation system evolves from an extractive thermally coupled system with a side rectifier. Specifically, the modification involves substituting the thermal coupling, i.e., the vapor-liquid interconnection, by a liquid side stream fed to a modified second column of the arrangement. The design procedure and performance on energy consumption and CO2 emissions of the proposed structure is illustrated with three case studies, which involve bioethanol dehydration and the separation of acetone-methanol and heptane-toluene mixtures. The results show that the proposed system can be more energy efficient and provide a more sustainable option when compared to conventional extractive distillation or thermally coupled sequences. We also show how the implementation of heat integration between columns of the proposed structure can be considered for additional savings on energy and CO2 emissions.