Synthesis and optimization of dividing-wall distillation columns for the separation of a quaternary mixture

Notwithstanding its low thermodynamic efficiency, distillation is among the most used separation processes in industry. As a consequence of the high energy consumption and the related environmental impact the research of more efficient alternatives remains one of the main interests in process engineering. Dividing-wall configurations are a well-known alternative to reduce the energy requirement of ternary distillation. Nevertheless, the design of dividing-wall columns for the separation of quaternary mixtures represents a challenge due to the number of possible configurations. In this work, a synthesis and design procedure is proposed for a double dividing-wall structure to separate quaternary mixtures. The performance of the intensified scheme is analyzed in terms of energy requirements, total annual cost, CO₂ emissions and thermodynamic efficiency. Due to the complexity of the system, after initial synthesis the structure is optimized through a meta-heuristic approach. The direct synthesis procedure leads to a dividing-wall system with higher energy requirements than the conventional sequences. However, after the rigorous optimization, savings in reboiler duty of 14.3% are obtained, with a reduction in TAC of 6.3%.