A coupled model for particle agglomeration in poly-disperse gas phase fluidized bed ethylene polymerization reactors
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Date
2015
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Publisher
Universiti Teknologi Malaysia
Abstract
Fluidized bed reactors (FBRs) are widely used in chemical, petroleum and petrochemical industries due to excellent mass and heat transfer. However, there are several drawbacks in the operation of gas phase fluidized bed ethylene polymerization reactor such as hot spot and agglomeration. In this research, two approaches were developed to investigate polymer particle agglomeration in the gas phase fluidized bed ethylene polymerization reactor. Firstly, a computational fluid dynamics (CFD) model was coupled with population balance model (PBM) to evaluate the hydrodynamics, heat transfer, and agglomeration in the gas phase polyethylene fluidized bed reactor. Arastoopour’s equation was also used to investigate the polymer particle agglomeration. A gas-solid multi phase flow equations were developed based on the Eulerian-Eulerian approach. In order to take into account the solid polydisperse particles, the population balance equation was solved along with continuity, momentum, and energy equations using quadrature method of moment. Although the polymer particles were homogenously distributed in the gas-solid FBR, the polymer particle agglomeration could occur in the high temperature operation conditions. Secondly, in order to consider the influence of polymerization reaction on the polymer particle size distribution, a multilayer polymeric flow model (MPFM) was coupled with the PBM to calculate the polymer particle agglomeration under intra-heat and mass transfer resistance. The industrial plant data were used to simulate the growth rate of single polymer particle and the polymer particle size distribution (PSD). Model predictions were in agreement with the industrial data, and the polymer PSD became broader as the agglomeration occurred. Results showed that the MPFM was a very effective model to describe the evolution of polyethylene particles in the FBR
Description
Thesis (PhD. (Polymer Engineering))
Keywords
Polymerization—Mathematical models, Polymer engineering, Fluidized reactors