Published: CABEQ 17 (1) (2003) 31–42
Paper type: Original Scientific Paper

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Economic and Controllability Investigation and Comparison of Energy-Integrated Distillation Schemes

M. Emtir, P. Mizsey, E. Rev and Z. Fonyo

Five different energy-integrated distillation schemes: two direct sequences with forward or backward heat integration (DQF, DQB), the Petlyuk or dividing wall system (SP), and two sloppy separation sequences with forward or backward heat integration (SQF, SQB) are investigated for the separation of a ternary mixture from economic and controllability points of view and compared to the non-integrated conventional direct separation scheme. The economic study shows that the optimal DQB has the highest total annual cost (TAC) saving: 37 %. SQF and SQB have 34 % and 33 % TAC savings, respectively. The controllability analysis, based on steady state indices, shows that the control loops of DQF and DQB have less interactions than in the case of the other energy-integrated schemes studied. The dynamic investigations also prove that DQF and DQB show similar controllability features than the non-integrated conventional scheme. Although the SQF and SQB have good economic features but their controllability features, especially the ones of SQB, are significantly worse than those of DQF and DQB. Therefore the controllability features should play a significant role at the selection of the energy-integrated distillation schemes.

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Energy-integrated distillation scheme, economic optimisation, controllability study