Effects of Mixing Using Side Port Air Injection on a Biomass Fluidized Bed

Abstract

Fluidized beds are being used in practice to gasify biomass to create producer gas, a flammable gas that can be used for process heating. However, recent literature has identified the need to better understand and characterize biomass fluidization hydrodynamics, and has motivated the combined experimental-numerical effort in this work. A cylindrical reactor is considered and a side port is introduced to inject air and promote mixing within the bed. Comparisons between the computational fluid dynamics (CFD) simulations with experiments indicate that three-dimensional simulations are necessary to capture the fluidization behavior of the more complex geometry. This paper considers the effects of increasing side port air flow on the homogeneity of the bed material in a 10.2 cm diameter fluidized bed filled with 500-600 μmground walnut shell particles. The use of two air injection ports diametrically opposed to each other is also modeled using CFD to determine their effects on fluidization hydrodynamics. Whenever possible, the simulations are compared to experimental data of time-average local gas holdup obtained using X-ray computed tomography. This study will show that increasing the fluidization and side port air flows contribute to a more homogeneous bed. Furthermore, the introduction of two side ports results in a more symmetric gas-solid distribution.

Experimental Investigation on Interaction of Side Gas Injection with Gas Fluidized Bed Using γ-Ray Transmission Technique

“…Deza et al studied the effect of side port air flow on particle mixing in a biomass fluidized bed having similar dimensions as previously referenced. 31 Drake and Heindel applied the 3D X-ray computed tomography to determine local time averaged gas holdup in fluidized beds with side air injection considering scale-up of such devices. 32 Min et al compared the computational fluid dynamics simulation to the experimental data of a laboratory scale fluidized bed with and without side gas injection.…”

Comparisons of Annular Hydrodynamic Structures in 3D Fluidized Beds Using X-Ray Computed Tomography Imaging

“…The use of CFD to model fluidized beds is highly dependent on the boundary conditions and validation through experimentation. Deza et al [8,9] and Min et al [10] have shown that X-ray visualization techniques can be used as a validation tool for fluidized bed hydrodynamic simulations.…”

Recent progress on renewable energy in engineering thermophysics

“…In the field of biomass [45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64], Luo et al [50] estimated the annual generation of crop residues, animal manure and organic faction of MSW in Hebei Province, China from 2002 to 2007. Qiao et al [51] investigated the biogas recovery from microwave heated sludge by anaerobic digestion.…”