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ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
Evaluation of minimum fluidization velocities for various particulates and operating conditions
Submission Author:
João Pinheiro , RS , Brazil
Co-Authors:
João Pinheiro, Eduardo Nóbrega, Álisson Renan Stochero da Silva, Flavia Zinani
Presenter: Eduardo Nóbrega
doi://10.26678/ABCM.ENCIT2022.CIT22-0571
Abstract
In order to allow the use of renewable energy sources, as well as to increase efficiency in energy conversion processes, researches involving fluidization technologies have been considerably increasing in the last decades. Advances in research on the use of fluidized bed reactors in thermal conversion demonstrate that this technology is promising and widely used for the most diverse forms in the energy and fuels segment. Fluidization is a two-phase flow process in which a fluid phase produces an upward flow, percolating a bed of particles towards the upper portion of the equipment, making this bed fluidized. Regarding the phenomena involved, there is great interest in the fluid dynamic behavior of the bed, which depends on the properties of the particulate material, its granulometric distribution, specific mass and morphology of the particles. In addition, there is dependence on the fluid phase and operating conditions, such as distributor plate and bed diameter, influencing the minimum gas velocities for bed fluidization. In this context, the present work aimed to analyze the properties that interfere in the minimum fluidization velocity for different particles, of cylindrical, spherical and irregular morphology, with different configurations of distributor plates, varying the arrangement of orifices at the base of a fluidized bed by compressed air. The particulates were characterized in terms of diameter, density and morphology – sphericity and aspect ratio. Using a bench-scale cylindrical reactor, the fluidization of the particles was performed in triplicates for each configuration, and the pressure drop variations with increasing fluidization air velocity were determined, which were analyzed graphically. Through the tests, a pattern was observed in which the longer configuration cylinders tend to present higher minimum fluidization velocities, due to their aspect ratio and physical arrangement inside the bed. The variation of the configurations allowed the change of fluidization regimes and minimum fluidization velocities. Models of distributors with central orifice made favorable the occurrence of a spouting fluidization regime with lower minimum fluidization velocities, however, in an unstable fluidization process. Distributor configurations with multiple orifices provided a similar regime, but with higher fluidization velocities than the central orifice configuration, maintaining stable fluidization due to smaller difference between pressures. In the configuration with a wire mesh distributor, a bubbling fluidization was observed, with higher minimum velocities compared to the other two configurations.
Keywords
fluidized bed, minimum velocity fluidization, Distributor Plate Configuration
