Mechanistic model to simulate wet agglomerate breakage in a gas-solid fluidized bed

Motlagh, A.H. Ahmadi; Palanisamy, Karthikeyan; Pougatch, Konstantin; Salcudean, M.; Grace, John R.; Grecov, Dana; McMillan, Jennifer

doi:10.1016/j.ces.2018.10.045

Cited by 8 publications

(8 citation statements)

References 22 publications

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“…Past studies have indicated that weaker agglomerates are produced when the fluidization velocity increases, [38,78] and the shear forces acting on agglomerates are more substantial, accelerating their fragmentation and erosion. [34,49] Figure 11 shows a significant variation between replicates: there is a significant random component in the motion of agglomerates and their interaction with gas bubbles, which is more pronounced at higher fluidization velocities. [80] Figure 12 shows results obtained with uneven gas distribution, using an average fluidization velocity of 0.4 m/ s. The spray nozzle was located on the west side, as shown in Figure 1.…”

Section: Agglomerate Formation and Breakupmentioning

confidence: 99%

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Experimental study of liquid vaporization in a fluidized bed

et al. 2022

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Liquid injection into a gas-solid fluidized bed has been applied in various industries, such as coating and granulation processes in pharmaceutical and food industries, reactor cooling in polyolefin production, fluid catalytic cracking, and fluid coking in the petroleum industry. A new experimental method has been successfully developed to monitor the vaporization rate of a liquid injected into a fluidized bed. In addition, it can be used to determine the mass of liquid accumulated in the bed at a steady state. With this new method, measurements have identified three phenomena that may increase the amount of liquid accumulated at steady state in a fluidized bed. (1) Gas mixing affects vaporization when the bed temperature is lower than the liquid boiling point. In liquid-rich regions of the bed, local vapour may build up, limiting the vaporization rate. Consequently, suitable emulsion to bubble gas transfer reduces the amount of accumulated liquid. (2) Solids mixing: hot particles from the rest of the bed must mix with the wetted particles to provide enough heat for vaporization. Good solids mixing reduces the amount of accumulated liquid.(3) Wet agglomerates formation: liquid trapped within wet agglomerates takes much longer to vaporize. The amount of accumulated liquid can be reduced by injecting the liquid in a well-agitated bed region, operating at a higher bed temperature, or increasing the flowrate of atomization gas.

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Section: Agglomerate Formation and Breakupmentioning

confidence: 99%

“…[49] Many of the experimental findings have been incorporated into models. [34,[55][56][57][58] Solids mixing brings hot bed particles to the spray region. When evaporative liquids are sprayed into a fluidized bed, liquid evaporation cools particles in the spray zone.…”

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confidence: 99%

Experimental study of liquid vaporization in a fluidized bed

et al. 2022

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“…Dependent upon agglomerate properties, segregation may promote breakup by allowing the agglomerates to concentrate in bed regions where they are more likely to be broken up by larger bubbles or gas distributor jets . Agglomerate breakup can be predicted with a model incorporating agglomerate properties and either CFD , or computational fluid dynamics–discrete element method (CFD–DEM) modeling of the local bed hydrodynamics. In fluid cokers, bed temperature, particle characteristics, and liquid properties are set by process requirements and agglomerate breakup can be enhanced by reducing the liquid content of the solids in the spray jet region and ensuring that wet agglomerates are exposed to gas bubbles.…”

Section: Reactormentioning

confidence: 99%

“…161 Dependent upon agglomerate properties, segregation may promote breakup by allowing the agglomerates to concentrate in bed regions where they are more likely to be broken up by larger bubbles or gas distributor jets. 175 Agglomerate breakup can be predicted with a model incorporating agglomerate properties and either CFD 176,177 or computational fluid dynamics−discrete element method (CFD−DEM) 178 modeling of the local bed hydrodynamics.…”

Section: Alternative Feedstocksmentioning

confidence: 99%

Review of Research Related to Fluid Cokers

Briens

McMillan

2021

Energy Fuels

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Fluid coking is a thermal conversion process that uses a conventional two-vessel circulating fluidized bed to convert heavy hydrocarbon feeds to lighter products. The technology was developed in the 1950s and since then has been used commercially around the world to upgrade heavy oils from various sources. Research work has been summarized related to all aspects of the fluid coking process, including reaction fundamentals, bed hydrodynamics, liquid distribution and jet–bed interaction, mixing of solid particles and agglomerates, mixing of vapors, control of the particle size, cleaning of the vapor stream in the scrubber, cleaning of the cold coke in the stripper, process monitoring, coke transfer lines, and the burner. The fluid coking process involves complex interactions between fluidized bed hydrodynamics, liquid feed injection, and reaction kinetics, and research tools that can take into account all of these interacting variables are requited to test methods to optimize the process. Fluid cokers can process many different types of feeds, and future applications may include blending and co-processing a variety of feedstocks ranging from waste plastics, pyrolytic bio-oil, and off-spec vegetable oils with heavy oil. The findings from this summary are also relevant for other applications that inject liquid into fluidized beds, such as the fluid catalytic cracking process, olefin polymerization cooled by liquid injection, granulators, and coaters.

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“…Granular agglomeration and agglomerate breakage are found in many particulate processes . Particles can be aggregated due to the cohesion/adhesion between particles induced by van der Waals forces, electrostatic interactions, and the presence of liquid bridges .…”

Section: Introductionmentioning

confidence: 99%

Breakage of wet flexible fiber agglomerates impacting a plane

et al. 2019

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The breakage of an agglomerate of wet flexible fibers impacting a plane is computationally investigated in this work using the discrete element method. In the agglomerate, the fibers stick together due to cohesive liquid bridge forces. Agglomerate breakage with various impact conditions, initial configurations, fiber properties, and liquid bridge properties is systematically investigated. The degree of breakage is governed by the impact energy, the cohesion energy due to liquid bridges, the energy dissipation/absorption through fiber-fiber contacts and fiber deformation, and the efficiency of force transmission within the agglomerate. More specifically, breakage is promoted by increasing impact velocity, decreasing agglomerate size, increasing initial compaction, increasing fiber bending modulus, decreasing liquid surface tension, and decreasing liquid-to-solid volume ratio. Breakage is strongly dependent on the modified Weber number, that is, the ratio of the Weber number to a dimensionless rupture distance, which is a measure of the impact energy relative to the cohesion energy. K E Y W O R D Sagglomerate breakage, discrete element method, flexible fiber, liquid bridge force

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Mechanistic model to simulate wet agglomerate breakage in a gas-solid fluidized bed

Cited by 8 publications

References 22 publications

Experimental study of liquid vaporization in a fluidized bed

Experimental study of liquid vaporization in a fluidized bed

Review of Research Related to Fluid Cokers

Breakage of wet flexible fiber agglomerates impacting a plane

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