Important mesoscale phenomena in gas phase fluidized bed ethylene polymerization

Sun, Jingyuan; Wang, Haotong; Tian, Sihang; Fan, Xiaoqiang; Shi, Qiang; Liu, Ying; Hu, Xiaobo; Yang, Yao; Wang, Jingdai; Yang, Yongrong

doi:10.1016/j.partic.2018.12.004

Cited by 15 publications

(10 citation statements)

References 169 publications

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“…However, in the non‐cloudy zone, it shows a completely contrary circumstance that the temperature is higher and the molar ratio of comonomer to ethylene is lower. Correspondingly, the low molecular weight polyethylene with less branches is generated 5 . The high molecular weight polyethylene with more branches highlights the excellent performance of the product of the cloudy ethylene polymerization, demonstrating the superiority.…”

Section: Introductionmentioning

confidence: 87%

“…For example, in a new ethylene polymerization process named the “cloudy ethylene polymerization” developed in recent years, liquid mixture containing inert condensing agent, and reactant comonomer (such as iso‐pentane, n ‐pentane, n ‐heptene, and 1‐hexene) is sprayed from the side wall into the fluidized bed for heat removal as well as copolymerization reaction 4 . Compared with the traditional gas‐phase ethylene polymerization technology, the separation, and re‐injection of liquid mixture are involved as shown in Figure 1 5 . Through adjusting the atomization and evaporation of the liquid mixture injected from the sidewall, the uniform temperature, and concentration distributions inside the reactor are disrupted.…”

Section: Introductionmentioning

confidence: 99%

“…Through adjusting the atomization and evaporation of the liquid mixture injected from the sidewall, the uniform temperature, and concentration distributions inside the reactor are disrupted. Particularly, when the bed temperature is close to the dew‐point temperature of the liquid, the liquid spray, and evaporation keep in a dynamic balance, hence, a gas–liquid–solid interaction zone (or vividly named “cloudy zone”) is formed near the liquid nozzle, 5 as shown in Figure 2. In combination with the gas–solid interaction zone, or named “non‐cloudy zone,” a totally new steady flow pattern with the coexistence of cloudy zone and non‐cloudy zone is established inside a single fluidized bed, which plays a vital role on ethylene polymerization.…”

Section: Introductionmentioning

confidence: 99%

“…Schematics of the Unipol ethylene polymerization gas phase process (a) and the cloudy ethylene polymerization gas phase process (b) 5 [Color figure can be viewed at wileyonlinelibrary.com]…”

Section: Introductionmentioning

confidence: 99%

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Dynamic characteristics of the volatile cloudy zone in a gas–solid fluidized bed with hydrocarbon liquid spray

et al. 2021

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In a gas–solid fluidized bed with continuous hydrocarbon liquid spray, a volatile “cloudy zone” could be formed, defined as a dynamically steady liquid‐affected zone, including droplets, wet particles, and the gas which passes through the zone. A new flow pattern with the dynamic coexistence of cloudy zone and non‐cloudy zone (gas–solid zone), is accordingly established. The temperature, particle concentration, and particle velocity fields are measured in real‐time via infrared thermography and particle imaging velocimetry, respectively. Results show that the area and range of central position of the cloudy zone illustrate a heavier fluctuant trend with the increasing velocity of liquid spray, and the main frequency of area fluctuation is close to that of the bubble rising. Moreover, the particle concentration and particle velocity in the cloudy zone are lower than those in the non‐cloudy zone, breaking the conventional symmetrical distributions of hydrodynamic parameters of particles in a gas–solid fluidized bed.

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Section: Introductionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Dynamic characteristics of the volatile cloudy zone in a gas–solid fluidized bed with hydrocarbon liquid spray

et al. 2021

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“…Sun et al. [ 20 ] looked more at mesoscale phenomena in FBRs, compared different types of computational fluid dynamics (CFD) and discrete element method (DEM) modeling approaches for PE and clearly demonstrated that mesoscale and macroscale phenomena are connected. Kaneko et al.…”

Section: Introductionmentioning

confidence: 99%

Gas‐Phase Polyethylene Reactors—A Critical Review of Modeling Approaches

Alves

Casalini

Storti

et al. 2021

Macro Reaction Engineering

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Different approaches to modeling the gas phase polymerization of ethylene that have been considered in the literature are reviewed. It is shown that while simple, well‐mixed models can give an adequate representation of the average performance of a given polymerization reactor, they do not allow one to analyze certain modeling problems such as the existence of temperature gradients or particle segregation, nor can they be used to treat operational modes such as condensed cooling where there can be up to three different phases in different parts of the reactor. For this, more complex models are required. These can take the form of compartmentalized models or even models based on computation fluid dynamics. However, long computational times can be required to fully exploit these models. Furthermore, significant progress needs to be made if one needs to address important phenomena such as agglomeration or particle attrition during polymerization.

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CFD–DEM simulations of wet particles fluidization with a new evolution model for liquid bridge

2022

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A new model for liquid-bridge evolution with consideration of particle dynamics, is proposed to improve Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) simulations of wet particles fluidization under high liquid loading and viscosity. A liquid bridge is allowed to form and remains stable only when the normal relative velocity of two particles is lower than a critical value v nc . A large v nc leads to an increase of liquid-bridge or cohesive force. The model can be reduced to the conventional liquid-bridge model in literature when v nc = 0 or ∞. With the new model, the prediction of bubble properties including bubble center, aspect ratio, and volume agrees well with the experimental data in literature. In particular, under high liquid loading, bubble disintegration due to particle agglomerating is reasonably captured.The simulations demonstrate the advantage of the new model that can extend the liquid-bridge models and CFD-DEM for high liquid loading and viscosity.

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Important mesoscale phenomena in gas phase fluidized bed ethylene polymerization

Cited by 15 publications

References 169 publications

Dynamic characteristics of the volatile cloudy zone in a gas–solid fluidized bed with hydrocarbon liquid spray

Dynamic characteristics of the volatile cloudy zone in a gas–solid fluidized bed with hydrocarbon liquid spray

Gas‐Phase Polyethylene Reactors—A Critical Review of Modeling Approaches

CFD–DEM simulations of wet particles fluidization with a new evolution model for liquid bridge

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