Simulation And Design Of 1 Million Tons/year Pvc Production Process

Polyvinyl chloride(PVC)is the second most widely consumed polymers in the world,accounting for more than a quarter of global resin consumption.In this paper,the production process of PVC is simulated,and the process accounting is carried out to improve quality and save energy,so as to solve the problems of low product quality,high energy consumption and pollution in the original process,and provide the direction for upgrading PVC industry under the background of carbon emission policy.It consists mainly of the following:(1)Testing of thermodynamic models: Thermodynamic modelling is the key basis for ensuring simulation calculations.Acetylene and hydrogen sulfide were selected as the key components of acetylene section and vinyl chloride(VCM)and dichloroethane as the key components of distillation section.The results show that the ELECCNRTL model and NRTL model were selected as thermodynamic models for the acetylene section and the distillation section respectively.(2)Simulation calculation of acetylene section: The wet acetylene process was selected and the acetylene generation and cleaning processes were simulated by RStoic reactor and Rad Frac module,respectively.Circulating cooling water is used to wash the washing tower to avoid the introduction of external cooling water.Acetylene gas with purity of 99.61%,hydrogen sulfide< 0.3 ppm,phosphine < 5 ppm and vinyl acetylene < 20 ppm were obtained.(3)Simulation calculation of Vinyl chloride section: Vinyl chloride was obtained by reacting refined acetylene gas with hydrogen chloride,and the purity of vinyl chloride was increased to 99.999% by using high and low boiling towers.By optimizing the operating parameters of low boiling tower T203,the condensation medium was changed from 7 ℃ frozen water of the original process to 32 ℃ circulating water,which greatly reduced the operating cost of the distillation process.VCM,EDC,CDE and other high value-added products in high boiling material were recovered by two-tower recycling process,and 99% of VCM was obtained from the top of T205 tower,99% of CDE was obtained from the side of T206 tower and 98% of EDC was obtained from the tower cauldron.(4)Simulation calculation of Polymer section: Suspension polymerization simulation was performed by batch distillation.VCM residue of PVC slurry < 1 ppm was obtained by simulating the optimization of the steam tower,which resulted in a 0.4% water content of PVC products.Considering that the unpolymerized VCM in the original process was mixed directly with the coarse VCM,this caused problems such as increased VCM distillation load.In this study,the VCM was purified and used directly for polymerization by adding T302 tower.(5)System Energy Efficiency Optimization: Reactive heat in VCM converters is recycled using lithium bromide / water absorption heat pumps to produce 5-8 ° C cold source and low pressure vapour.Heat pump distillation was carried out in T203 and T204 towers,resulting in a 79% reduction in energy consumption in T203 and 84% reduction in energy consumption in T204.