Enhanced Particle Mixing in Pulsed Fluidized Beds and the Effect of Internals

Abstract

Pulsation-assisted fluidization was employed in a square fluidized bed to enhance mixing properties. The gas-phase pulsation frequency was varied between 0.5 and 5.0 Hz. The fluidized bed hydrodynamics were studied with and without internals, in beds of different heights. From the measurement of pressure fluctuations, average cycle frequencies (ACF) and incoherent standard deviations (IOP) were calculated to quantify bubble characteristics, such as the bubble size. In addition, optical probe measurements were used to determine the local bubble fraction. When a fraction of the total flow is oscillated with an appropriate frequency, possible defluidization problems are prevented. A clear change in the bubble characteristics was observed when increasing the pulsation frequency up to 3.0 Hz. Higher pulsation frequencies, especially beyond 5.0 Hz, have no significant effect when compared to a steady, constant flow. Pulsation-assisted flow significantly increases bubble size, increases the ACF, and decreases bubble fraction. Moreover, the presence of internals slightly decreases the bubble size, slightly decreases the ACF, significantly decreases the bubble fraction, and influences the bubble pathway, especially at low superficial gas velocity. Finally, increasing the bed height has a less clear trend on the ACF, but it increases the bubble size using either steady or pulsed flow, with more significant increases in the latter case.

A nature-inspired approach to reactor and catalysis engineering

“…By pulsing the gas, fluidization is more uniform, and channeling and clumping are prevented. This improves the performance of fluidized bed combustion and drying [81,82]. Periodically perturbing the gas in a fluidized bed can suppress chaos by 'phase locking ' [83], however the periodicity of the bubble pattern is remarkable [79 ].…”

Coupling Euler–Euler and Microkinetic Modeling for the Simulation of Fluidized Bed Reactors: an Application to the Oxidative Coupling of Methane

“…As a whole, this work paves the way for the application of a reactive multiscale modeling to industrial scale fluidized units, representing a tool for the design and scale-up of novel fluidized technology. 48 , 49 …”

Computational fluid dynamic simulations of regular bubble patterns in pulsed fluidized beds using a two‐fluid model

“…Several attempts have been made to order the chaotic fluidization process by manipulating the particle flow dynamics and gas distribution. [7][8][9] Most of these attempts employ intrusive modifications of the column by including baffles, electrodes, and distributed gas injectors, thereby structuring the bed hydrodynamics. [9] Some more intrusive improvements of fluidized beds for obtaining regularly-structured flow patterns include the manipulation of the interparticle forces through AC electric fields.…”