(13b) Novel Column Configurations and Operational Strategies for Distillation with Electric Heating

Over 40,000 distillation columns are operating in the United States alone, and account for approximately 90-95% of all separations and 20% of energy consumption in the chemical and petroleum refining sector.^1-3 Distillation is a thermal separation operation, and a significant portion of the energy used in distillation systems is due to process heating. Most typically heating is done using steam, which is generated by combusting fossil fuels. Therefore, distillation has a correspondingly high contribution to the carbon footprint of the chemical industry.

The transition to process electrification using renewable electricity provides an opportunity for decarbonizing distillation. Using a clean electricity source to generate heat can, in principle, fully eliminate carbon dioxide emissions from distillation processes. Most distillation columns in continuous processes are operated at or very close to steady state, which assumes that heat (and the corresponding energy source) is consistently available at the required levels at all times. On the other hand, renewable electricity generated by wind or solar photovoltaic plants is inherently variable. As a consequence, distillation systems using renewable electricity as the source of heat should have increased flexibility and the ability to accommodate fluctuations in available power.

Motivated by the above, we introduce novel modular distillation column architectures that feature distributed electric heating on each stage, and additional degrees of freedom for modulating material flow rates between stages. We demonstrate that these structures have high flexibility and turndown capacity, as well as exceptionally small startup times compared to conventional designs.

We illustrate these ideas in simulation case studies that consider the separation of binary and ternary mixtures and discuss optimal column design and operating strategies under fluctuations in power availability.

[1] Humphrey, J.; Seibert, A. Chem. Eng. 1992, 86-98.

[2] Kiss, A. J. Chem. Technol. Biotechnol. 2014, 479-498.

[3] Isopescu, R.; Woinaroschy, A.; Drãghiciu, L. Rev. Chim. 2008, 812-815.