Modeling Of Gas-Phase Linear Low Density Polyethylene Fluidized-Bed Reactor In Condensed Mode

Gas-phase fluidized bed is widely used in linear low density polyethylene (LLDPE) polymerization. Using a gas-phase fluidized bed polymerization process reduces the energy requirements as compared to other processes and most importantly reduces the capital investment required to run a process. However, the limited heat transfer capacity restricts the space time yields. To solve the problem, the condensed mode process was created. Now, the gas-phase process in our country is changing to the condensed mode process. Consequently, it is necessary to build mathematical model, which can provide basis for the optimization of the polymerization reactors.A continuous stirred tank model and a two-phase model are developed, which comprises mass balance equations, energy balance equations and reaction kinetic equations. The parameters in the kinetic model are retrieved from the articles published.The innovation of this model is considering the influence of the condensed liquid to the reactor behavior. Based on the continuous stirred tank model and the two-phase model in condensed mode, the LLDPE yield, the ethylene concentration, the catalyst fraction in the polyethylene, the catalyst activity and the distribution of concentration and heat, and so on, are calculated in the industry situation. Not only the key results are computed, but also the behavior of the reactor along with the condensed liquid, the catalyst feed rate and the entrance temperature et al are analyzed. They provide references for the optimization of the LLDPE fluidized bed in condensed mode.The result shows that the simulation results agree with the actual parameters well.