Experimental characterization of liquid film behavior during droplets–polyethylene particle collision

Ren, Xuefei; Sun, Jingyuan; Huang, Zhengliang; Yang, Yao; Tian, Sihang; Wang, Jingdai; Yang, Yongrong

doi:10.1002/aic.16909

Cited by 13 publications

(6 citation statements)

References 32 publications

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“…Image processing was carried out to extract data from the images taken at different time instants using quasi-circle processing of MATLAB code. It can be divided into two parts, recognition and extraction, which was earlier reported in Ren et al 16 The program stimulates the gray level of all of the pixels to obtain the boundary value. After the particle profile was determined, points on the contour of the particle are collected and fit into a circle multiple times.…”

Section: Image Processingmentioning

confidence: 99%

“…The furthest extended arc length s and center angle φ are both parameters describing the spreading process of the liquid film, so only φ is discussed. The treatment methods are as shown in eqs and , respectively The droplet–particle collisions are usually characterized using dimensionless parameters such as the Weber number, Reynolds number, Capillary number, Ornezog number, etc., which are defined as shown in eqs –.…”

Section: Experimental Arrangementmentioning

confidence: 99%

“…The liquids used in the above experiments differ significantly from organic hydrocarbon substances, and solid particles chosen are generally metal or glass spheres, whose physical properties such as wetness, roughness, and thermal conductivity , are also obviously diverse from polyethylene particles. Thus, Ren et al conducted an experimental study of the collision characteristics. n -Hexane and 1-octene droplets and polyethylene spheres were taken as the target.…”

Section: Introductionmentioning

confidence: 99%

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Collision Characterization of Mixed Hydrocarbon Liquid Droplets with Polyethylene Particles

Hong

Sun

Yang

et al. 2021

Ind. Eng. Chem. Res.

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In the gas−solid fluidized bed with condensed liquid spray applied to ethylene polymerization, the collision characteristics of condensed droplets and polyethylene particles play an important role in determining the heat transfer and product properties. High-speed photography, noninvasive laser heating, and a quasi-circle data processing approach are employed to investigate the collision interaction between the hydrocarbon liquid droplets with different mixed compositions and a single polyethylene particle, under different particle temperatures and droplet Weber numbers. The results have found that the hydrodynamic behavior and heat transfer characteristics of the liquid films formed during the droplet−particle collision are more dependent on the liquid components with a higher mass fraction. The behavior of the liquid films is divided into two types, named the directly slip and recoil, the latter of which is beneficial for enhancing heat and mass transfer efficiency. Especially under low Weber numbers, the long-time recoil only occurs during the evolution of 1-octene and n-hexane/1-octene mixed liquid films. Generally, as the Weber number rises, the temperature thresholds required for recoil appearance increase for all kinds of liquid films. It is indicated that the necessary conditions for recoil are low inertia force and high temperature.

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Section: Image Processingmentioning

confidence: 99%

Section: Experimental Arrangementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Collision Characterization of Mixed Hydrocarbon Liquid Droplets with Polyethylene Particles

Hong

Sun

Yang

et al. 2021

Ind. Eng. Chem. Res.

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“…Albeit some studies in literature have considered the assumption of heterogeneous evaporation in FBRs, ,, some experimental studies have further investigated interactions between the particle and droplet. Ren et al studied the collision interaction characteristics between PE particles and liquid droplets by high-speed photography and a quasicircle imaging approach. They have reported that collision of the liquid droplet with PE particle results in stretching and wrapping of PE particle by a liquid film in which a portion of liquid film leaves the particle surface and a small amount of liquid covers the surface.…”

Section: Modeling a Fbrmentioning

confidence: 99%

Prediction of Temperature and Concentration Profiles in an Industrial Polymerization Fluidized Bed Reactor under Condensed-Mode Operation

Atashrouz

Rahmani

Nasernejad

et al. 2021

Ind. Eng. Chem. Res.

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Condensed mode operation of gas-phase ethylene polymerization adds more complexity to the hydrodynamics of fluidized bed reactors (FBRs). This study aims at the development of an industrial ethylene polymerization FBR model operating in condensed mode, and in this regard, the classical two-phase theory was modified. Two modeling strategies were investigated: a simple twophase model (model I) and a more complex one taking the presence of a wet zone (model II) into consideration. To access the predictive capabilities of the two models, model predictions were compared with plant data. The absolute relative deviation percentages for model I in prediction of the production rate and catalyst flow rate were 10.4 and 14.8, respectively. However, these errors for model II were 0.80 and 10.36, respectively. It was observed that the temperature profile predicted by model I was more consistent with that of plant data when the bubble diameter was considered to be small because of enhanced heat transfer rates between the bubble and emulsion phases. However, this assumption was not necessary for model II, and assuming a maximum stable bubble diameter for bubbles in the reactor, which is a more realistic assumption, the predicted temperature profile was reasonable. According to the results of model II, two zones, wet (including liquid droplets) and dry (including evaporated liquid), are formed in the condensed-mode operation of FBRs. It was found that for low-condensing agent flow rates (70 ton/h in this study), the difference between process conditions (concentration and temperature) of wet and dry zones increases (ΔC = 22.16 mol/m 3 and ΔT = 40.19 K), which can produce bimodal polyethylene (PE). Furthermore, a search strategy was developed based on the imperialist competitive algorithm and model II to find polymerization conditions needed to produce a PE grade with a specified microstructure. The results showed that the proposed algorithm is efficient for such a purpose. The sensitivity analysis of model I proved that in low gas velocities, the emulsion phase temperature is very sensitive to the catalyst flow rate. Moreover, the results of model I demonstrate that the dependency of temperature and monomer concentration of the emulsion phase on particle elutriation is negligible, especially under normal operating conditions.

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“…In the previous study, our research team studied the collision process of hydrocarbon droplets with polyethylene particles in detail. Ren et al 13 conducted an experimental study on the collision process between n‐hexane, 1‐hexene droplets, and polyethylene particles. Two kinds of liquid film behaviors were found, named the directly slide and recoil and accompanied by evaporation and splash.…”

Section: Introductionmentioning

confidence: 99%

Mass transfer characterization for hydrocarbon liquid–particle collision based on sensitive tracing of fluorescent probe

Sun

Wang

et al. 2022

AIChE Journal

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The heat and mass transfer characteristics during the collision process of hydrocarbon droplets and polyethylene particles in a liquid‐containing gas–solid polyethylene fluidized bed reactor significantly affect the product quality. In this work, the mass transfer process of single‐component hydrocarbon and bi‐component hydrocarbon liquid films on the polyethylene particle surface were quantitatively characterized by a newly developed experimental approach, based on a novel synthesized hydrocarbon liquid soluble fluorescent probe for sensitive tracing of hydrocarbon liquid diffusion. It was found that the boiling point and surface tension of the liquid as well as the surface temperature of the particle are the key factors affecting the mass transfer properties of the liquid film. Marangoni convection was observed and characterized on the particle surface. The critical time for the onset of Marangoni flow is between 4 and 8 s.

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Experimental characterization of liquid film behavior during droplets–polyethylene particle collision

Cited by 13 publications

References 32 publications

Collision Characterization of Mixed Hydrocarbon Liquid Droplets with Polyethylene Particles

Collision Characterization of Mixed Hydrocarbon Liquid Droplets with Polyethylene Particles

Prediction of Temperature and Concentration Profiles in an Industrial Polymerization Fluidized Bed Reactor under Condensed-Mode Operation

Mass transfer characterization for hydrocarbon liquid–particle collision based on sensitive tracing of fluorescent probe

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