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%.