Study On Simulation And Optimization Of Vinyl Chloride Reactors From Hydrochlorination Of Acetylene Process

Great technical changes have taken place in vinyl chloride monomer (VCM) preparation as the global increasing demand for polyvinyl chloride (PVC). Mathematical modeling and simulation analysis played an important role in scale-up of reactors and operation optimization, from traditional two-stage fixed-bed reactor to fluidized bed reactor and compound reactor. In this paper, mathematical models were established based on different type of reactors, and after validation of data from pilot-scale and industrial reactors, simulation analysis of different factors and system optimization analysis were presented. The main results were listed as follows:(1) According to the reaction kinetics and analysis of commercial reactor, a two-dimensional pseudo-homogeneous dispersion model was employed to describe and evaluate the operation conditions of industrial fixed-bed reactor for hydrochlorination of acetylene. With experiential data from pilot-scale reactor, the method Crank-Nicholson was used to solve the equations. By using the model mentioned above, the simulation results fitted well with the industrial data. According to the simulation, it was found that the space velocity of acetylene and catalyst performance have great influence on the distribution of reactor temperature and products. If the final conversion rate at tube exit was set less than 70%, an expression of the optimum space velocity of acetylene can be deduced by considering the relationship between the space velocity of acetylene and catalyst activity.(2) After considering bubble factor in fluidized bed, a two-phase bubble model, which based on the reaction kinetics of hydrochlorination of acetylene and previous studies, was established to describe and analyze the operation conditions of industrial fluidized bed reactor. Fourth- and fifth-order Runge-Kutta algorithms was employed to solve the equations and the simulation results coincided well with the industrial data. Besides, the calculated bubble with a diameter of 3.59 cm show high rationality of the model. According to the simulation, it was found that the conversion of acetylene decreased with the increasing of fluidization number, and the acetylene concentration difference between bubble and emulsified phase decreased with the increasing of the height of reactor. What's more, the conversion of acetylene also increased with the catalyst capacity.(3) Fluidization number, catalyst activity in fixed-bed reactor and the space velocity of fixed-bed reactor were founded to affect the result of compound reactor most. If we set the optimization goal that the equipment have the maximum production capacity, the results could be obtained from simulation as follows:the fluidization number could be kept in a steady level when the activity of catalyst in fluidized bed reactor kept the same, and the space velocity of fixed-bed reactor decreased linearly with the decreasing of catalyst activity in fixed-bed reactor. So the compound reactor could be kept running stably by allotting different space velocity for fixed-bed reactor with different catalyst activity in actual industrial operation, that is big space velocity for fixed-bed reactor with high catalyst activity, and small space velocity for fixed-bed reactor with low catalyst activity according to the correlation.