CFD study on solids flow pattern and solids mixing characteristics in bubbling fluidized bed: Effect of fluidization velocity and bed aspect ratio

2015 ◽  
Vol 274 ◽  
pp. 379-392 ◽  
Author(s):  
Maryam Askarishahi ◽  
Mohammad-Sadegh Salehi ◽  
Hamid Reza Godini ◽  
Günter Wozny
Keyword(s):  
Aspect Ratio ◽  
Flow Pattern ◽  
Fluidized Bed ◽  
Fluidization Velocity ◽  
Mixing Characteristics ◽  
Bubbling Fluidized Bed ◽  
Solids Mixing

scholarly journals Coal–biomass mixing characteristics in a bubbling fluidized bed of Geldart A particles

2017 ◽  
Vol 120 ◽  
pp. 1-14 ◽  
Author(s):  
Bahareh Estejab ◽  
Guevara Che Nyendu ◽  
Foster Agblevor ◽  
Francine Battaglia
Keyword(s):  
Fluidized Bed ◽  
Mixing Characteristics ◽  
Bubbling Fluidized Bed

Solids mixing in a shallow cross-flow bubbling fluidized bed

2018 ◽  
Vol 187 ◽  
pp. 213-222 ◽  
Author(s):  
Weibin Kong ◽  
Bin Wang ◽  
Jan Baeyens ◽  
Shuo Li ◽  
Hui Ke ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Cross Flow ◽  
Bubbling Fluidized Bed ◽  
Solids Mixing

scholarly journals NOx EMISSIONS FROM BUBBLING FLUIDIZED BED COMBUSTION OF LIGNITE COAL

2015 ◽  
Vol 55 (4) ◽  
pp. 275 ◽  
Author(s):  
Pavel Skopec ◽  
Jan Hrdlička ◽  
Jan Opatřil ◽  
Jiří Štefanica
Keyword(s):  
Nitrogen Content ◽  
Fluidized Bed ◽  
Oxygen Concentration ◽  
Brown Coal ◽  
Conversion Factor ◽  
Nox Emissions ◽  
Fluidization Velocity ◽  
Bed Temperature ◽  
Bubbling Fluidized Bed ◽  
Air Staging

This paper presents experimental results of NO<sub>x</sub> emission measurements for combustion of two kinds of coal in a bubbling fluidized bed combustor. The tested fuels were Czech brown coal (CBC) and German young brown coal (GYC). These fuels have different nitrogen contents. The experiments were performed in the pilot scale BFB experimental unit with power output of 500 kW. The influence of several parameters on NO<sub>x</sub> formation are investigated in this paper. The parameters studied here include the effect of the nitrogen content in the fuel, the effect of the oxygen concentration in the bed, the effect of bed temperature, the effect of air staging, and the effect of fluidization velocity. Significantly different behaviour of the fuels was found. Although GYC has a lower nitrogen content than CBC, it is more reactive and produces higher NO<sub>x</sub> emissions. The biggest dependence of NO<sub>x</sub> production for CBC was found for the effects of air staging and fluidization velocity. As the fluidization velocity increases and the amount of secondary air decreases, there is an increase in NOx emissions. The oxygen concentration in the bed has the strongest effect on the NO<sub>x</sub> production of GYCs. With increasing oxygen concentration, the production of NO<sub>x</sub> also increases. On the basis of the NO<sub>x</sub> measurements, the N-NO conversion factor was calculated and the effect of the operating parameters on this conversion factor was investigated.

Effect of the Shape of the Baffles on the Hydrodynamics of a Fluidized Bed

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Srinivasa Rao Venkata Naga Kaza
Keyword(s):  
Fluidized Bed ◽  
Fluidized Beds ◽  
Gas Flow ◽  
Experimental Studies ◽  
Expansion Ratio ◽  
Blockage Ratio ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Minimum Fluidization ◽  
Bubbling Fluidized Bed

Gas flow in a gas–solid fluidized bed is characterized by the predominance of bubbles. When gas flow is more than the minimum fluidization velocity, the top of the fluidized bed may fluctuate vigorously leading to unstable operation. Bed fluctuation and fluidization quality are interrelated. The quality of fluidization can largely be improved by introducing baffles in bubbling and turbulent fluidized beds. In the present work three baffle geometries, i.e., circular, triangular and square are used to determine different hydrodynamic parameters such as minimum fluidization velocity, bed expansion, pressure drop across the bed, fluctuation ratio, expansion ratio, etc. in a bubbling fluidized bed. A new parameter blockage ratio is introduced to analyze the behaviour of baffled fluidized beds. It is found from the current experimental studies that the blockage ratio mainly influences the hydrodynamics of the bed rather than the shape of the baffle.

Minimum Air Fluidization Velocity Study of Specific 2-D Bubbling Fluidized Bed Reactor

2014 ◽  
Vol 699 ◽  
pp. 660-665
Author(s):  
M. Fadhil ◽  
M.S. Aris ◽  
A.H. Abbas ◽  
A.B.A. Ibrahim ◽  
N. Aniza
Keyword(s):  
Fluidized Bed ◽  
Particle Density ◽  
Flow Behavior ◽  
Numerical Approach ◽  
Combustion Efficiency ◽  
Fluidized Bed Combustion ◽  
Fluidization Velocity ◽  
Bubbling Fluidized Bed ◽  
Flow Through ◽  
Bed Expansion

Research on the thermodynamic behavior of sand beds was carried out using a commercial computational dynamic package. The work involved simulating, with the use of the Ergun equation, the air flow through a two-dimensional bubbling bed reactor to predict the bed character whilst considering the major effective function (particle size, particle density, bed height and reactor width). The Minimum Fluidization Velocity (Umf) values were then calculated before the optimum value of Umfneeded to ensure a workable Bubbling Fluidize Bed Combustor (BFBC) system. The effects of using different Umfvalues on the flow behavior were also investigated using the numerical approach at different times. The results from these investigations indicate that the bubbling region in the fluidized bed combustion can be correlated to the sand bed expansion with minimum errors and assist in enhancing the combustion efficiency by supplying the required volume of oxygen into the system.

scholarly journals Particle-Scale Simulation of Solid Mixing Characteristics of Binary Particles in a Bubbling Fluidized Bed

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4442 ◽  
Author(s):  
Junjie Lin ◽  
Kun Luo ◽  
Shuai Wang ◽  
Liyan Sun ◽  
Jianren Fan
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Critical Velocity ◽  
Superficial Velocity ◽  
Mixing Index ◽  
Mixing Behavior ◽  
Mixing Characteristics ◽  
Bubbling Fluidized Bed

The behavior of solid mixing dynamic is of profound significance to the heat transfer and reaction efficiencies in energy engineering. In the current study, the solid mixing characteristics of binary particles in the bubbling fluidized bed are further revealed at particle-scale. Specifically, the influences of gas superficial velocity, Sauter mean diameter (SMD) in the system and the range distribution of particle sizes on the performance of mixing index are quantitatively explored using a computational fluid dynamics-discrete element method (CFD-DEM) coupling model. The competition between solid segregation and the mixing of binary particles is deeply analyzed. There is a critical superficial velocity that maximizes the mixing index of the binary mixture in the bubbling fluidized bed. Solid mixing performs more aggressive when below the critical velocity, otherwise solid segregation overtakes mixing when above this critical velocity. Moreover, superficial velocity is a major factor affecting the mixing efficiency in the binary bubbling fluidized bed. Additionally, the mixing behavior is enhanced with the decrease of SMD while it is deteriorated in the binary system with a wide range of particle size distribution. Therefore, it is highly recommended to perform a binary particle system with smaller SMD and closer particle size distribution for the purpose of enhancing the mixing behavior. The significant understanding of mixing characteristics is expected to provide valuable references for the design, operation, and scale-up of binary bubbling fluidized bed.

Cofiring low-rank coal and biomass in a bubbling fluidized bed with varying excess air ratio and fluidization velocity

Energy ◽  
2020 ◽  
Vol 203 ◽  
pp. 117882 ◽  
Author(s):  
Paulo R. Wander ◽  
Flávio M. Bianchi ◽  
Nattan R. Caetano ◽  
Marcos A. Klunk ◽  
Maria Luiza S. Indrusiak
Keyword(s):  
Fluidized Bed ◽  
Low Rank ◽  
Low Rank Coal ◽  
Fluidization Velocity ◽  
Excess Air ◽  
Bubbling Fluidized Bed
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