Simulation Of Batch Reactive Distillation For Esterification Process In Poly(Ethylene Adipate) Synthesis

The main reactions in synthesizing poly(ethylene adipate) from adipic acid and ethylene glycol are reversible, and the equilibrium constants of esterification reactions are small. Currently, most industrial methods to produce poly(ethylene adipate) are non-steady-state process coupling batch reaction with distillation, which need to remove by-products from the system to promote the positive reaction. The effect of distillation has a direct influence on the reaction. From infinitesimal segmentation and extreme ideological point of view, the model of the esterification stage of the batch production of poly (ethylene adipate) is built using Aspen Plus software, which split the entire process into numerous short period; all of these short period are assumed to be steady-state, and the complete batch model was constructed by connecting repeating units consisting of a reactor and a distillation column. Then the Step-growth method was used to establish the kinetics model of the esterification process. Each of these repeating units respectively represents the reaction progress of the batch reactor at different time. Firstly, experiments were carried to verify the the accuracy of this model, it was found that the experimental acid value and other properties of both experimental products could match calculated ones well. The average relative error of the experimental and calculated values for both the molecular weight of the polymers and the amount of distilled water were within12%. Secondly, using this model, the esterification process were simulated and analysed, which displayed that the reaction temperature should be as high as possible under the condition that most ethylene glycol has participated in the reaction. Either too high or too low, the molar ratio of acid to alcohols would adversely affect the molecular weight. The optimum mole ratio of alcohol to acid is1.15. Under variable reflux ratio conditions, the optimum economic efficiency could be achieved when the water distillate ratio was95%. Finally, the20tons of production scale was taken as an example to design and check the corresponding distillation column for the batch esterification process, and the treatment amount fluctuations of distillation column changing with reaction process were taking into consideration. When using pall ring as the filler, the appropriate column diameter is0.6～1.2meters and the height is about3.6meters.