Key Words:distillation; dynamic; process control ;energy

Abstract:BACKGROUND: The triple-column extractive distillation (TCED) process for the ternary multi-azeotropic mixture of N-hexane/acetone/chloroform is a significant step in waste recovery and purification. Given the common occurrence of feed disturbances in practical industrial production, a feasible dynamic control scheme should effectively resist feed disturbances and ensure product quality, enabling the process to run steadily and safely with a high efficiency. However, it is challenging to design a robust control scheme for separation processes accompanied by side-stream capability. In this work, dynamic control schemes were designed for four separation processes: conventional and double side-stream TCED processes with single and double entrainers. A multipoint temperature control scheme, composition-temperature cascade control scheme and iable ratio control were combined to improve the dynamic performance of the control schemes. RESULTS: The results showed that the control schemes designed for the four extractive distillation processes are highly robust, resisting /- 20% feed flow and composition disturbances. A iable ratio control combined with composition-temperature cascade was found to be vital for double side-stream TCED schemes. CONCLUSION: The conventional TCED with a single entrainer (CS-TCED) is an optimal process for N-hexane/acetone/chloroform separation both from control and economic perspectives. The designed control scheme is simple, low-cost and easy-to-implement with a superior dynamic performance over other separation schemes. This study has a certain theoretical guidance for N-hexane/acetone/chloroform separation in terms of economic benefits and practical production.

Volume:97

Issue:8

Translation or Not:no