Flow Structures and Gas-Mixing Induced by Bubble Bursting at the Surface of an Incipiently Gas-Fluidized Bed

2004 ◽  
Vol 43 (18) ◽  
pp. 5738-5753 ◽  
Author(s):  
Roberto Solimene ◽  
Antonio Marzocchella ◽  
Raffaele Ragucci ◽  
Piero Salatino
Keyword(s):  
Fluidized Bed ◽  
Flow Structures ◽  
Gas Mixing ◽  
Bubble Bursting

Gas-Mixing in Bubbling Fluidized Bed Combustors: Hydrodynamics and Macromixing Associated With Bubble Bursting at the Bed Surface

2003 ◽  
Author(s):  
R. Solimene ◽  
A. Marzocchella ◽  
P. Salatino ◽  
R. Ragucci
Keyword(s):  
Fluidized Bed ◽  
Fluid Dynamic ◽  
Volatile Matter ◽  
Solid Fuels ◽  
Flow Structures ◽  
Specific Reference ◽  
Gas Mixing ◽  
Fluidized Bed Combustion ◽  
Bubble Bursting ◽  
Bubbling Fluidized Bed

Gas-mixing phenomena may play a significant role in fluidized bed combustion of solid fuels. Issues associated with gas mixing include: a) effectiveness of mass transfer between the bubble and the emulsion phases in the bed; b) degree of mixing between segregated gaseous streams in plume-like or bubbly flow in the bottom bed; c) extent of mixing between segregated gaseous pockets/streams in the splashing zone or in the upper freeboard. Among the others, issues b) and c) turn out to be relevant to fluidized bed combustion of high-volatile solid fuels (biomass, RDF, etc.). In this case, the rate of gas mixing often overcomes intrinsic kinetics as the rate-controlling step in volatile matter burn-out, especially under “stratified” combustion conditions. Despite several and significant contributions to the subject, understanding of gas-mixing in bubbling fluidized beds is still poor and calls for additional investigation. The present work aims at investigating gas-mixing in bubbling fluidized bed with specific reference to the above issue c). A laser assisted imaging technique has been used to characterize the hydrodynamic patterns associated with the bursting of either isolated bubbles or couples of closely time-delayed bubbles at the surface of a fluidized bed. Quantitative image analysis procedures were exploited in order to assess parameters defining the general fluid-dynamic behaviour and macromixing of the bubble-generated gas pockets with the mainstream gas. The formation of toroidal flow structures upon bubble bursting is highlighted in the case of isolated bubbles. The toroidal pockets entrain mainstream gas and grow accordingly while rising along the splash zone. Toroidal flow structures are observed also in the case of couples of closely time-delayed bubbles, but interference between leading and trailing pockets leads to more complex structures characterized by multiple incoherent eddies. The relevance of macromixing to volatile matter burning under conditions of stratified fluidized bed combustion is assessed and discussed.

Gas mixing in a multi-stage conversion fluidized bed (MFB) with secondary air injection. Part I: an experimental study

RSC Advances ◽  
2016 ◽  
Vol 6 (43) ◽  
pp. 36642-36655 ◽  
Author(s):  
Rong Zhang ◽  
Zhenhua Hao ◽  
Zhiyu Wang ◽  
Xiaodong Huo ◽  
Junguo Li ◽  
...  
Keyword(s):  
Experimental Study ◽  
Fluidized Bed ◽  
Air Injection ◽  
Gas Mixing ◽  
Cold Model ◽  
Stage Conversion ◽  
Multi Stage ◽  
Secondary Air Injection ◽  
Secondary Air

This paper investigated the distribution of secondary air after injection into a multi-stage conversion fluidized bed (MFB) cold model.

Radial gas mixing in a circulating fluidized bed

2000 ◽  
Vol 113 (1-2) ◽  
pp. 23-29 ◽  
Author(s):  
Won Namkung ◽  
Sang Done Kim
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Gas Mixing

Gas mixing and modeling of secondary gas distribution in a bench-scale fluidized bed

AIChE Journal ◽  
2004 ◽  
Vol 50 (5) ◽  
pp. 922-936 ◽  
Author(s):  
Fahad Al-Sherehy ◽  
John Grace ◽  
Alaa-Eldin Adris
Keyword(s):  
Fluidized Bed ◽  
Gas Mixing ◽  
Gas Distribution ◽  
Bench Scale

Hydrodynamics and gas mixing in a carbon nanotube agglomerate fluidized bed

AIChE Journal ◽  
2006 ◽  
Vol 52 (12) ◽  
pp. 4110-4123 ◽  
Author(s):  
Hao Yu ◽  
Qunfeng Zhang ◽  
Guangsheng Gu ◽  
Yao Wang ◽  
Guohua Luo ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Fluidized Bed ◽  
Gas Mixing

Investigating the flow structures in semi-cylindrical bubbling fluidized bed using pressure fluctuation signals

2019 ◽  
Vol 30 (6) ◽  
pp. 1247-1256
Author(s):  
Seyedeh Mahsa Okhovat-Alavian ◽  
Jamshid Behin ◽  
Navid Mostoufi
Keyword(s):  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Flow Structures ◽  
Bubbling Fluidized Bed

Comparison of the flow structures and regime transitions between a cylindrical fluidized bed and a square fluidized bed

2020 ◽  
Vol 376 ◽  
pp. 507-516
Author(s):  
Haidong Zhang ◽  
Zeneng Sun ◽  
Mengze Zhang ◽  
Yuanyuan Shao ◽  
Jesse Zhu
Keyword(s):  
Fluidized Bed ◽  
Flow Structures ◽  
Regime Transitions
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