Modeling And Simulation Of Complex Distillation System Based On Group Method

Simulation and optimization for complex distillation system with recycle stream and thermal-coupling are more difficult than regular system because of the high-dimension and narrow convergence field. In this thesis, simplified model distillation column section based on Group Method was used to balance the accuracy and convergency. According to the structured analysis, the complex distillation system simulation program is divided into several scales and models.The primary work of this thesis is presented as following:1. Applying the idea of structuring to distillation modeling, and dividing the flowsheet into four sacles. Modules included feed stage, heat exchanger, splitter, distillation column section, and thermodynamics module of SRK and PR equation will be done.2. Introduce Group Method into distillation column simulation instead of multiple rigorous theoretical stages. In this thesis, in addition to the mean value assumptions and linear hypothesis, making an analysis of the performance profile of absorption factor exchanging with different reflux ratios of crude argon tower of an air separation unit, we propose a method which use the S-wave curve equation to fit the performance profile of absorption factor exchanging and establish the set algorithm of distillation column segments based on the wave theory. Through the application of the crude argon column with simulation examples, it proves the effectiveness of this method which can effectively reduce the deviation caused by the simplified model.Applying modeling the program to simulate two thermally coupled distillation columns base on this method. At first, use the structural analysis method to analysis the process, step by step to establish the thermodynamic modules, function modules, device models and process simulation program. Results for these thermally coupled distillation systems simulation shows that the simulation results basically the same with business process simulation software.The simulation results indicated that the modeling process logic become simple. The distillation results prediction is accurate by the group method and the number of equation and variables are significantly reduced.