Dynamic simulation and control of two‑series industrial reactors producing linear low‑density polyethylene

One of the leading routes for producing polyolefns is through gas-phase catalytic fuidized bed reactors. In this study, the industrial gas-phase ethylene polymerization reactor series of Jam Petrochemical Company has been dynamically analyzed, modeled and controlled. The copolymerization of ethylene with 1-butene is defned on Zeigler–Natta catalyst, assuming a double active site mechanism. To serve this purpose, pseudo-kinetic rate constants and the method of moments have been employed. The proposed model is capable of predicting the unsteady-state behavior of each reactor in addition to the properties of the product such as melt fow index (MFI), dispersion index, and molecular weight distribution (MWD). The verifcation of the model has been conducted with plant data to prove the accuracy of the model-estimated MWD and MFI. The controllability of the process control confguration has been examined through analyzing the dynamic behavior of the process under conventional feedback PID controllers. It has been observed that the control structure delivers a convincing performance for disturbance rejection.