Hydrodynamic investigation of industrial gas-phase polyethylene reactors in two different technologies

Document Type : Research Article

Authors

Center of Engineering and Multiscale Modeling of Fluid Flow (CEMF), Faculty of Chemical Engineering, Amirkabir University of Technology, Tehran, Iran

Abstract

Gas-solid fluidized bed reactors are among the common methods to produce linear low-density polyethylene. The contact quality between the two phases and the mixing of the solid particles in these reactors have significant impacts on the polymerization reaction. In this research, the hydrodynamic behaviour of two reactors licensed by Basell and Mitsui companies was investigated using computational fluid dynamics. Two-fluid model with the kinetic theory of granular flow was used. The model was first validated using experimental data, and then the analyses of the Mitsui and Basell industrial reactors were carried out. The results showed that the uniformity of the gas phase volume fraction, which indicates the quality of the gas-solid contact, increases with the distance from the bed bottom in both reactors so that at a normalized height of 0.96, the phase homogeneity reaches its maximum. At this height, the coefficient of variations of volume fraction in the Basell and Mitsui reactors are 0.4% and 1.3%, respectively, and the phase homogeneity in the Mitsui reactor is always higher than that in the Basell reactor at different heights, indicating a better contact between particles and gas. The time-averaged axial velocity of the solid particles at different heights showed that the intensity of solid particle movement is higher in the Basell reactor, so that at a normalized height of 0.72, the axial velocity of the solid particles in the Basell reactor is approximately 2 m/s, while it is approximately 1 m/s in the Mitsui reactor. Considering the axial velocity parameter, it can be concluded that the quality of solid particle mixing in the Basell reactor is higher than that in the Mitsui reactor.

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References

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Amirkabir Journal of Mechanical Engineering
Volume 56, Issue 4
2024
Pages 517-542

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