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Fluidization and Fluidized Bed
Published in Ko Higashitani, Hisao Makino, Shuji Matsusaka, Powder Technology Handbook, 2019
Xinhua Liu, Shanwei Hu, Xinhua Liu, Bona Lu, Xizhong Chen, Limin Wang
Fluidization is a process where solid granules are transformed into a fluid-like state through suspension in a stream of gas, liquid, or their mixture. Consider a container with an open top and perforated plate at the bottom: solid particles will pack closely at the bottom under the action of gravity, and the total mass of particles is supported by the plate. If a stream of fluid flows upwards through the bed of particles at a low flow rate, the fluid merely percolates through the void spaces between stationary particles, and the particle bed remains in a fixed or packed state. As the flow rate of the fluid increases to a value at which the drag force of the fluid just counterbalances the effective weight of the particles, minimum fluidization is thought to be reached and the corresponding fluid velocity is called the minimum fluidization velocity (Umf). As the fluid velocity is increased to near the terminal velocity (Ut) of the particles, the bed expands continuously and the particles are pushed apart to act like a fluid. This state is called fluidization.
Chemical Reactor Applications
Published in Theodore Louis, Behan Kelly, Introduction to Optimization for Environmental and Chemical Engineers, 2018
Fluidization is the process in which fine solid particles are transformed into a fluid-like state through contact with either a gas or liquid, or both. Fluidization is normally carried out in a vessel filled with catalyst solids. The fluid is normally introduced through the bottom of the vessel and forced through the bed. At a low flow rate, the fluid (liquid or gas) moves through the void spaces between the stationary and solid catalyst particles and the bed is referred to as fixed. As the flow rate increases, the catalysts begin to vibrate and move about slightly, resulting in the onset of an expanded bed. When the flow of fluid reaches a certain velocity, the solid catalysts become suspended because the upward frictional force between the catalyst and the fluid balances the gravity force associated with the weight of the catalyst. This point is termed minimum fluidization or incipient fluidization and the velocity at this point is defined as the minimum or incipient fluidization velocity. Beyond this stage, the bed enters the fluidization state where bubbles of fluid rise through the solid catalysts, thereby producing a circulatory and/or mixing pattern.5
Thermal Energy Management
Published in Anil Kumar, Om Prakash, Prashant Singh Chauhan, Samsher, Energy Management, 2020
Anil Kumar, Om Prakash, Prashant Singh Chauhan, Samsher
The extent of fluidization is dependent on the size of the particles and the velocity of air. This means for a stable system, the extent of fluidization is less than that of gas. The difference between the mean velocity of solid and gas is the slip velocity. The slip velocity should be maximum for the solid and gas for excellent heat transfer and proper contact. Heating the particles of sand up to the ignition temperature of the fuels, and there is a constant injection of fuel, hence there will be a rapid burning of the fuel and attaining homogenous temperature throughout the bed. The FBC combustion takes place at 840°C–950°C. This temperature is much lesser than the ash fusion temperature and hence, problems related to melting of ash are avoided.
CFD-DEM simulation of fluidization of multi sphere-modeled corn particles
Published in Particulate Science and Technology, 2022
Preeda Prakotmak, Sathaphon Wangchai
The CFD-DEM model has been applied in previous relevant research to predict the movement of particles in fluidized beds and spouted beds, but only for particles that were spherical in shape (Takeuchi, Wang, and Rhodes 2008; Rong and Zhan 2010; Ren et al. 2011). By contrast, the real shape of particles could be oval, cylindrical, or capsular. A small number of studies have simulated grain sprouted close to the actual shape. Ren et al. (2012) simulated the shape of grains in a spouted bed with the multi-sphere method at different fluid velocities. It was found that a simulated corn kernel constructed with 4 spheres rendered better predictions than one with 7 spheres. In addition, Hilton, Mason, and Cleary (2010) and Zhou et al. (2011) studied the dynamics of ellipsoidal particles on the pressure inside the bed. They found that the particle shape had a significant effect on the minimum velocity of fluidization. However, only a few studies have been conducted on the influence of corn shapes on heat transfer in fluidized bed systems. Therefore, this research is intended to study the dynamics of the movement of corn kernel particles in a fluidized bed drying chamber using the CFD-DEM model to calculate the minimum fluidization velocity and particle temperature for drying corn kernels.
Fluidization of biomass: a correlation to assess the minimum fluidization velocity considering the influence of the sphericity factor
Published in Particulate Science and Technology, 2021
Andrés Reyes-Urrutia, José Soria, Alejandra Saffe, Mariana Zambon, Marcelo Echegaray, Sergio G. Suárez, Rosa Rodriguez, Germán Mazza
In this context, comprehensive information about the size, shape, and density of biomass particles is significantly important to predict fluidization behavior and minimum fluidization velocity (Tannous et al. 2013; Rezaei et al. 2016). Also, for non-spherical particles, the mean diameter and shape factors (such as sphericity) depend strongly on the evaluation method (Hegel et al. 2014; Olatunde et al. 2016). Cui and Grace (2007) performed a review of the fluidization of biomass particles. They observed very little knowledge existed about the influence of particle size and shape, moisture content, and compressibility on fluidized bed behavior. They identified different aspects to research into (a) the fluidization characteristics for wide ranges of biomass particle size and their relationship with more commonly studied particles, and (b) the influence of particle properties and extremely irregular shape on fluidization behavior.
Wettability improvement of pea protein isolate agglomerated in pulsed fluid bed
Published in Particulate Science and Technology, 2020
Raul Favaro Nascimento, Juliana Gomes Rosa, Kaciane Andreola, Osvaldir Pereira Taranto
The pulsed fluid bed agglomeration has been reported as an efficient process to improve the quality of foodstuff (Dacanal and Menegalli 2010; Dacanal, Hirata, and Menegalli 2013; Machado, Hirata, and Menegalli 2014). It has several advantages over conventional fluidization, e.g., reduction of minimum fluidization velocity, reduction of channeling, and fluidization of cohesive powder (Machado, Hirata, and Menegalli 2014). Dacanal, Hirata, and Menegalli (2013) present more realistic data for the agglomeration of spray-dried cohesive particles in the pulsed fluid bed. Other authors also analyzed pulsed fluid bed systems to process cohesive powders. Dacanal and Menegalli (2010) determined the optimal process conditions for agglomeration of soy protein isolate. Chen et al. (2009) used a fluid bed to coat cornstarch particles by atomization of hydroxypropyl cellulose aqueous solution. Yet, there is little information about powders having similar characteristics to pea protein isolate, and this work intends to give an initial understanding about agglomeration of this raw material.