Optimization And Control For Mibk-N-Butanol Azeotropic System Using Extractive Distillation And Pressure-Swing Distillation

It is difficult to separate the MIBK-n-butanol minimum azeotrope with traditional distillation. In view of the economic and technical feasibility, extractive distillation (ED) and pressure-swing distillation (PSD) were proposed in this article to separate MIBK-n-butanol system.The vapor-liquid equilibrium (VLE) data of MIBK-n-butanol and MIBK-n-butanol-ethylene glycol (EG) were measured. The Wilson, NRTL and UNIQUAC activity coefficient models were used to correlate the VLE data to obtain the binary parameters. The RMSDs of vapor phase composition for MIBK-n-butanol system from the three models were less than 0.01. The three models all have a high degree of agreement with MIBK-n-butanol binary system and could be used to simulation. For the ternary system of MIBK-n-butanol-EG, the RMSD of vapor phase composition for NRTL is 0.0322, which shows a high precision. The optimization and dynamic control of ED and PSD for MIBK-n-butanol system were further researched using the obtained equations.EG was evaluated as the most suitable solvent for extractive distillation of MIBK-n-butanol. Optimal operating parameters of ED were obtained according to the optimization with sequential iterative method, and the corresponding TAC was 150,759.461$/y. Dynamic responses of control structures for the ED indicate that the control structures with fixed reflux ratio, R/F, QR/F could not efficiently handle disturbances of feed flow rate. Robust control can be achieved with dual temperature controllers which were added to solvent-recovery column and could control the reflux flow rate and the reboiler heat input.For the PSD separation technology of MIBK-n-butanol system, Aspen Plus was used to economically optimize the minimum of total annual cost (TAC). The optimal processes of the PSD with no, partial, and full heat integration were obtained. Dynamic control performances of different heat-integrated PSD were investigated with Aspen Plus Dynamics. The results indicated that the composition-reflux ratio cascade control structure could be used to deal with the disturbances of feed flow rate and feed composition of the PSD with no and partial heat integration. However, the pressure-compensated temperature control structure should be adopted for the PSD with full heat integration to achieve effective control.The results can provide guidance to the steady-state economic optimization and dynamic characteristics for the separation of similar azeotropic system.