Research On The Design And Control Of Separating Methanol-Acetonitrile

Extractive distillation (ED) and Double effect pressure swing distillation (PSD) were used for the separation of methanol-acetonitrile in this paper. The Chemical process simulation software of Aspen Plus and Aspen Dynamics were used for design and control of the distillation processes. Aniline was selected as the solvent by comparing infinite dilution relative volatility in the design of ED. The value of solvent ratio was4.5. In the design of the steady-state of the two distillation processes. The lowest total annual cost (TAC) was taken as the objective function. Aspen Plus was used for optimizing the distillation parameters. Economic optimization results showed that PSD cost less than ED under the same separation conditions.Aspen Dynamics was used for the dynamic simulations. Fixed reflux ratio structure and feedforward-feedback control structure were designed in the dynamic simulation of ED. Feed flow rate±10%and feed composition disturbances were added into the system. The dynamic performance showed that control structure with fixed reflux ratio did not meet the quality design specification, the feedforward-feedback control structure was able to handle disturbances well. Fixed R/F ratio and feedforward-feedback control structures were designed in the dynamic simulation of PSD. Feed flow rate±5%and feed composition disturbances were added into the system, the dynamic simulation results revealed that both control structures were able to maintain product quality and that feedforward-feedback control structure did not show better dynamic performance than fixed R/F ratio control structure. Researching on the R/F control system, the results were:the control system showed good controlling ability and quality of products, which fully complied with the design specification as feed flow rate decreased. Reducing the methanol content in feed composition was conducive to quality control and lessening the reboiler heat duty of pressure tower T1. Comparing to the controlling ability of ED control system with PSD, ED had greater operation flexibility.