Modeling And Simulation Of The Vinyl Chloride Rectification Process

Vinyl chloride (Vinyl Chloride, VC) is an important industrial raw material, and the main application of it is to produce polyethylene resin. PVC resin is one of the five synthetic resin, so the quality of VC directly affects the quality and cost of PVC resin.In order to achieve polymerization grade VC (99.95%, wt), distillation method is often used to obtain high-purity VC in the industry. However distillation process is a very energy consumption process, the research of VC distillation process is of great significance for industrial production. In this thesis, Aspen Plus simulation software is carried out to model and simulate VC distillation process of Xinjiang Zhongtai Chemical Co., Ltd. Huatai alkali plant. The feedstock is 25m3/h, which contains a vinyl chloride of 99.4%. The main work as follows:1. Provided an overview of different methods to product vinyl chloride and analyzed the rectification process, pointing out the rectification process is energy-intensive production process.Then, the ways of simulation process was summarized, including sequential modular method, equation oriented method and the simultaneously modular method. Analysis of the equilibrium and rate-based model of distillation column, described the features of the two models, selected a rate-based model simulation method of this thesis.2. An overview of commercial process simulation software HYSYS and Aspen Plus features is mentioned, choose Aspen Plus as the rectification process simulation software and then the rectification process was established. The results showed:At the pressure of 0.52?0.53 MPa, the total stage of low boiling tower is 29 at the third feed stage with the reflux ratio of 5. To the high boiling tower, At the pressure of 0.26-0.28MPa, the total stages are 41 at the feed stage 12 with the reflux ratio 0.6.The simulation results are consistent with the industry data.3. Analyzed the mass fraction of the two towers. For low-boiler tower, the reflux flow is 1350.82kg/h, the vapor stream out of the tower is 201.25kg/h, and with VCM of 90.571%. The loss rate of 0.81% at vinyl chloride, and acetylene recovery was 99.68%; For high boiler tower, the reflux flow is 4465.76 kg/h, the amount of the overhead stream is 22873.6kg/h, with the content of 99.99% VCM, to the requirements of polymer class. The flow of bottom stream at high-boiler tower is 278.71kg/h at the content of 51.77%.4. The sensitivity analysis is used to study the feed stage, recovery rates and reflux ratio to the distillation process, the propose of which is to optimize the VCM distillation. The results as follows:to the low boiling tower, the total stages are 29 at the feed stage of 3 with the B/F 0.99, and the reflux ratio is 6; to the high boiling tower, the total stages are 41 at the feed stage of 12 with the D/F 0.99, and the reflux is 0.2.5. Finally we simulate and optimize the above results, the rate-based model is adopted to rate the process. The results meet the Tower design standards. To the low boiling tower, the maximum flooding factor is 0.245, the pressure drop is 20.31kPa and the maximum backup/tray spacing is 0.307; To the high boiling tower, the maximum flooding factor is 0.569, the pressure drop is 32.22kPa and the maximum backup/tray spacing is 0.259.