Effect of recycle streams on energy performance and closed loop dynamics of distillation sequences

This paper presents the retrofit of five conventional distillation trains for the separation of quaternary Mixtures of hydrocarbons for feed compositions with high or low content of intermediate components. The retrofit implies the incorporation of liquid or vapour recycle streams among the conventional distillation columns. Each recycle stream removes one condenser or one reboiler. The introduction of thermal links can lower the energy consumption up to 40% in contrast to conventional distillation trains widely used in the industry. This efficiency in the use of energy is achieved because the recycle streams, introduced in the conventional distillation trains, reduce the remixing associated with higher energy consumption. Also, the introduction of recycle streams can improve the dynamic responses in contrast to those obtained in the conventional distillation sequences. Hence, the introduction of recycle streams in the conventional distillation sequences can improve both the energy consumption and the control properties.