(529d) Dynamic Operational Strategies of a Dividing-Wall Distillation Column with Electric Heating

Distillation is an energy-intensive thermal separation technology, which accounts for approximately 40% of chemical industry energy consumption.¹ Currently, process heating in distillation relies primarily on combustion-based methods, making distillation responsible for approximately 4% of global greenhouse gas emissions.² Thermal electrification has emerged as a promising approach to reduce carbon emissions in industrial processes by primarily replacing fuel-based heating with electric alternatives. However, there exists a gap in research on how to adopt electric heating in distillation processes and facilitate their integration with utility systems. Most distillation columns are operated at or very close to steady state, which assumes that heat is consistently available at the required levels. Directly replacing fossil fuels with electricity sourced from the power grid is currently not cost-effective as distillation columns cannot readily adapt their large production loads to fit a variable power supply (assuming power is generated by renewables). Therefore, the successful execution of process electrification should incorporate both energy-efficient designs and dynamic operating strategies that account for power availability, and ultimately reduce energy costs. The dividing-wall distillation column (DWC) is an example of such optimized design, as it separates ternary mixtures with 30-50% lower energy consumption compared to typical multi-component distillation setups.

In this work, we study dynamic operation of an electrified DWC leading to substantial energy-costs savings while maintaining (on average) target distillation production rates and product purities over time. The operation involves increasing column throughput when electricity is available during the day and decreasing it when renewable electricity generation is constrained (e.g., at night). A rigorous first-principles model of the pilot-scale column available at the University of Texas at Austin Pickle Research Center, allows us to gain insight into the DWC’s dynamics. In our optimization studies, we consider the separation of ternary mixtures and demonstrate the feasibility of dynamically adjusting the DWC operation in response to real-time changes in fluctuating energy availability. By integrating these adjustments and leveraging control strategies, we enhance the column’s adaptability to situations when renewable electricity is used to generate the heat required by the thermal separation process, while ensuring reliable separation performance.

[1] Kiss, A. A.; Smith, R. Energy 2020, 203, 117788.

[2] Cui, C.; Qi, M.; Zhang, X.; Sun, J.; Li, Q.; Kiss, A. A.; Wong, D. S.-H.; Masuku, C. M.; Lee, M. Renew. Sust. Energ. Rev. 2024, 199, 114522.