Computational study on the effect of slug dynamics on the operation of a polyolefin 8-leg loop reactor of industrial scale

The causes and ad-hoc remedies associated with the formation of slugs that result in pump power fluctuation inside slurry loop reactors have been discussed in several patent literature, but studied in few research publications. The circulation of large polymer slugs inside loop reactors can induce violent fluctuations of pump power that can lead to automatic shutdown of the entire production process. In our previous work, we have developed a computational fluid dynamic (CFD) model using the Eulerian - Eulerian two fluid method to study the solid segregation and solid dispersion mechanisms inside an 8-leg loop reactor of industrial scale. Herein we adopt this model to study the response of such loop reactor to the slug circulation. The modeling results reveal that the profiles of reactor outputs, i.e., solid volume fractions, velocity magnitudes and pump pressure output, demonstrate random fluctuations with small amplitudes when the reactor is in normal operations. However, these profiles show drastic fluctuations in a periodic manner once a large slug is circulating around the loop reactor. The solid dispersion mechanism governed by the secondary flow inside vertical legs cannot dissipate the slug effectively as the dispersion occurs primarily on the radial direction. Therefore, a mitigation method that offers mixing in the transverse direction is necessary to assure safe and continuous production process. (C) 2017 Elsevier B.V. All rights reserved.