Optimization And Control Of Extractive Distillation Process For Separating The Mixture Of Methyl Acetate-methanol-water

In recent years,energy saving and emission reduction requirements are getting higher and higher.Distillation operation is the most basic chemical unit operation process as the high energy consumption,so it is of great significance to study the energy saving technology of distillation process.In this paper,the separation and purification of methyl acetate-methanol-water system from pharmaceutical solvent wastewater by extractive distillation was studied.The pressure swing extractive distillation process was improved by extractive distillation with vapor side stripper.Then the operating parameters of two process was optimized.In the last,the research and optimization of the process control scheme made the production process operate stablely to reduce extra energy consumption in the process caused by system instability.The mass fraction of methyl acetate,methanol and water mixture is 74%,19%,and 7%,respectively.The water is used as the extractant and the steady state simulation was carried out by Aspen Plus with NRTL property method.RSM was used in the optimization of distillation process and the feasibility of separation was verified by experiments.Based on the above reasearch,the sidestream distillation column with rectifier was designed for the extractive distillation process.The two separation schemes were optimized.The results showed that under the same separation conditions,the reboiler duty has been reduced with global optimization for the two process.For the extractive distillation process,the temperature sensitive plate of the two tower was determined by the singular value decomposition method.The operating variables and the controlled variables were reasonably matched.Control effect was detected by 10% disturbance of feed flow and component.The results showed that extractive distillation tower with single temperature control can effectively control the purity of methyl acetate and methanol tower with double temperature control can better control the purity of methanol,but the response time and volatility is relatively large.QR/F feedback control structure was adopted to control the reboiler duty of the two tower,the effect indicated that the CS2 had better controllability with a shorter stable time and smaller fluctuation than CS1 of sensitive plate temperature to control the reboiler duty.For the vapor sidestream with rectifier,the singular value decomposition method was used to determine the temperature sensitive plate,meanwhile for the sidedraw stream flow rate by V/QR control structure,and reflux rate of side column by composition-temperature cascade control.The control scheme was tested by 10% feed flow disturbance and 5% composition disturbance.Compared with the control method of direct control of sensitive plate temperature for reboiler duty,QR/F control structure has better control effect.The sidestream flow rate control structure was improved by feedback control scheme of sensitive plate temperature of side rectifier to control the compressor shaft speed.Comparing with CS4,the control performance is more stable with smaller fluctuation and shorter stable time.