Research And Development Of Distillation Section For 300kt/a Vinyl Chloride

Due to its superior performance,polyvinyl chloride(PVC)is widely used in agriculture,industry,construction and other fields of national economy and people's livelihood.Distillation section is an important part of PVC production.The quality of PVC is largely determined by the results of distillation.And the energy consumption of distillation also accounts for a considerable proportion of the entire PVC production.The process simulation technology is used to perform process simulation and parameter optimization of the 300,000 tons/year vinyl chloride refining section in the PVC production and the new process will solve the current problems.Aiming at the problem of dealing with high/low-boiling residues in traditional vinyl chloride distillation,the molecular sieve adsorption scheme is proposed to reduce the water content of VC.In this paper,thermodynamic consistency tests are performed on the vapor-liquid equilibrium data of VC-EDC and CDE-EDC systems.The results show that the selected literature data meet the thermodynamic consistency.The parameters of WILSON,UNIQUAC,and NRTL models are obtained by literature data regression.The model simulation values are compared with the experimental values.Owing to the smallest average relative deviation,NRTL model is gained as the most suitable model for the vinyl chloride system.Comparising the actual engineering values with simulated,we confirm that NRTL model is most suitable for vinyl chloride system.In this article,the plant's vinyl chloride distillation section is simulated.Finally,the optimal process parameters of low-boiling tower T1 and high-boiling tower T2 are obtained through univariate and orthogonal analysis.After optimization,the low-boiling residues are below 1 ppm,the high-boiling residues also fell to 0?1 ppm,and the vinyl chloride reach 99.948%in the VC products.Due to repalcing the 7 ? chilled water with the 32 ?recycling water and reducing reflux ratio,the total operating cost is reduced by 17.10 million yuan/year.They are simulated and optimized that the third distillation tower T3 and recovery tower T4 through the Aspen Plus process simulation software in treatment process of the high-boiling residues.The operating parameters such as the optimal operating pressure,number of theoretical plates,feeding position,reflux ratio,and distillation ratio of the third distillation column T3 and recovery column T4 are obtained.Absorption tower T5 and desorption tower T6 of the low-boiler residues treatment process are simulated.They are obtained the operating parameters such as the optimal operating pressure,the theoretical plate number of absorption tower T5 and desorption tower T6.After the simulation and optimization,the high-boiling residues are separated into vinyl chloride(99.495%),dichloroethylene(99.670%),dichloroethane(98.687%),and the vinyl chloride of low-boiling residues are reduced by 62.3%.It can increase the annual profit of 43.57 million yuan.Aspen adsorption software is applied to simulate the vapor-phase adsorption and dehydration process of vinyl chloride,and the parameters such as the diameter of the molecular sieve,the adsorption pressure,and the height of the adsorption bed are analyzed and optimized.Finally,the best adsorption parameters are achieved:molecular sieve diameter Rp = 2.0 mm,adsorption pressure P = 3.60 bar,adsorption bed height Hb = 8.5 m.It is reduced to 21.9 ppm that the water of vinyl chloride products after adsorption.The amount of molecular sieves is decreased by 15%at the guaranteed adsorption time,and the purity of vinyl chloride products is as high as 99.997%.