Axial velocity gradient effects in tubular loop polymerization reactors

Generally, a comprehensively distributed reactor model must incorporate a momentum balance equation to calculate velocity gradient. However, the momentum balance equation also leads to the increasing complexity of the reactor model, which was neglected in previous works. In this work, issues whether the velocity gradient can be neglected or not are addressed. On the basis of mass, energy and momentum balances, polymerization kinetics as well as the thermodynamic state equations, two dynamically distributed reactor models either considering or neglecting axial velocity gradient are presented to examine its effect in tubular loop polymerization reactors. The results indicate that the axial velocity gradient has an important effect on the reactor flow-field parameters (i.e. propylene concentration, catalyst concentration, hydrogen concentration, polypropylene concentration, temperature and pressure) at low recycle ratios (Rec<50) and its effect on these aforementioned parameters can be neglected yet at high recycle ratios (Rec50). Namely, herein, we suggest that the momentum balance equation must be incorporated into the reactor model at Rec<50 and it can be neglected for the reactor model at Rec50, which is helpful to the distributed modeling of the tubular loop polymerization reactor. (c) 2012 Curtin University of Technology and John Wiley & Sons, Ltd.