Factorial Analysis on the 2-D Transient Solid Velocity in Fluidized Bed Combustor

2003 ◽  
Author(s):  
Seong W. Lee ◽  
Yun Liu
Keyword(s):  
Fluidized Bed ◽  
Particle Velocity ◽  
Design Method ◽  
Factorial Analysis ◽  
Cold Model ◽  
Experimental Conditions ◽  
Image Velocimetry ◽  
Transient Velocity ◽  
Particle Velocities ◽  
Fluidized Bed Combustor

The transient solid velocity analysis in fluidized bed combustor (FBC) freeboard has been critical in the past two decades (Haidin et al 1998). The FBC cold model (6-in ID) was designed and fabricated. The solid transient velocity in FBC freeboard was measured and analyzed with the assistance of the advanced instrumentation. The laser-based Particle Image Velocimetry (PIV) was applied to the FBC cold model to visualize the transient solid velocity. A series of transient particle velocity profiles were generated for factorial analysis. In each profile, the particle velocity vectors for 100 position points were in the format of Vx and Vy. Analysis of Variance (ANOVA) was used to determine the significant factors that affect the transient particle velocities, time, and position coordinates. Then, the 1010factorial design method was used to develop a specific empirical model of transient particle velocity in FBC freeboard which was in the shape of Vx = f1(t, x, y), and Vy = f2(t, x, y). This unique factorial analysis method was proved to be very effective and practical to evaluate the experimental conditions and analyze the experimental results in FBC systems.

scholarly journals A new design method for fluidized bed conversion of largely heterogeneous binary fuels

2017 ◽  
Vol 21 (2) ◽  
pp. 1105-1118
Author(s):  
Pal Szentannai ◽  
György Pláveczky ◽  
Csaba Sándor ◽  
Tibor Szűcs ◽  
János Ősz ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Design Method ◽  
Calculation Methods ◽  
Cold Model ◽  
Minimum Fluidization Velocity ◽  
Binary Character ◽  
The Common ◽  
Fuel Particles ◽  
Fluidized Bed Combustor ◽  
Novel Design

Binary fuels of a fluidized bed combustor or gasifier are solids composed of two groups of particles. Their optimal handling in the same bed becomes rather difficult if their hydrodynamic properties differ by two orders of magnitude or more. Both of these fuel classes are directly fed into the reactor in most cases but the rather homogeneous fuel originally fed switches into a binary character inside the reactor in some others. A typical example of the latter case is the thermal utilization of rubber wastes. A novel design is proposed in the present paper by setting up a non-mixing, non-elutriated binary bed. Design criteria and procedure are formulated as well. One of the known calculation methods is proposed to be applied for assuring a segregated bed by means of choosing the bed components, geometry, and gas velocity conveniently. Cold model experiments are proposed to be applied for assuring no elutriation of the fine fuel particles and no sinking of the coarse fuel particles in the same time. A simple experiment is proposed for determining the common minimum fluidization velocity of the binary bed because known calculation methods can not be applied here.

Different Exit Effects between a Combined Riser with Variable Exit Constraints and a Conventional Riser with Weak Exit Constraints

2012 ◽  
Vol 550-553 ◽  
pp. 529-533
Author(s):  
De Wu Wang ◽  
Meng Da Jia ◽  
Shao Feng Zhang ◽  
Chun Xi Lu
Keyword(s):  
Fluidized Bed ◽  
Particle Velocity ◽  
Large Scale ◽  
Operating Conditions ◽  
Wall Region ◽  
Cold Model ◽  
Linear Distribution ◽  
Cross Sectional ◽  
Bed Height ◽  
Solids Holdup

A large-scale cold model experimental setup of combined riser with variable constraint exit (CRVCE) was established. The axial and radial distributions of solids holdup and particle velocity, under different operating conditions, were investigated experimentally, and the results were compared with conventional riser (CR). Experimental results showed that, the exit restrictive effect of combined riser with variable constraint exit was weak when particle circulation flux and static bed height in upper fluidized bed were lower, while it turned to be strong when superficial gas velocity and static bed height in upper fluidized bed were higher. Under the same conditions, averaged cross-sectional solids holdup of CRVCE was characterized by C type distribution when article circulation flux was higher, while that of CR with weak constraint exit was characterized by linear distribution. In axial direction, averaged cross-sectional particle velocity of CRVCE changed in order: acceleration-constant-decrease velocity, while that of CR changed in another: acceleration-constant velocity. The maximum of local solids holdup value of CRVCE appeared at the dimensionless radius position r/R=0.7, while that of CR appeared in the wall region. Their local particle velocities were similar in the core region, while local particle velocity of CRVCE was lower than that of CR in the annular region.

Hydrodynamic Performance of a Novel Design of Pressurized Fluidized Bed Combustor

2003 ◽  
Author(s):  
Alan L. T. Wang ◽  
John F. Stubington
Keyword(s):  
Fluidized Bed ◽  
Gas Flow ◽  
Scaling Laws ◽  
Scaling Law ◽  
Gas Injection ◽  
Hydrodynamic Performance ◽  
Silica Sand ◽  
Particle Movement ◽  
Cold Model ◽  
Fluidized Bed Combustor

A bench-scale fluidized bed combustor with a novel fluidizing gas injection manifold was successfully built for characterization of Australian black coals under pressurized fluidized bed combustion (PFBC) conditions. The bed of silica sand (mean size 1.3 mm and density 2700 kg/m3) was 40 mm ID with a static height of 75 mm. This facility was designed to operate at 1.6 MPa, 850°C and a fluidizing velocity of 0.9 m/s, identical to those used industrially, in order to match as closely as possible the local hydrodynamic environment around each coal particle in an industrial PFBC. To verify satisfactory hydrodynamic performance with the novel gas injection manifold, the fluidization was directly investigated by measuring differential pressure fluctuations under both ambient and PFBC conditions. In addition, a Perspex cold model was built to simulate at ambient conditions the hydrodynamics of the hot bed in this PFBC facility. The cold model was constructed to a geometric scale of 1.431:1, determined by Glicksman’s scaling law. Under PFBC conditions of 1.6 MPa, 850°C and 0.9 m/s, the bed in UNSW’s PFBC facility operated in a stable bubbling regime and the solids were very well mixed. The bubbles in this PFBC were effectively cloudless and no gas backmixing or slugging occurred; so the gas flow in this bed could be modeled by assuming two phases (bubble and particulate) with plug flow through each phase. The results from the cold model showed that the ratio of Umf for the simulated bed to Umf for the hot PFBC bed matched the conditions proposed by Glicksman’s scaling laws. The bubbles rose along the bed with axial and lateral movements (moving both towards and from the wall), and erupted from the bed surface evenly and randomly at different locations. Two patterns of particle movement were observed in the cold model bed: a circular pattern near the top section, and a rising and falling pattern dominating the particle movement in the lower section created by the rising bubbles.

Particle Velocity in a Dense Gas-Solid Fluidized Bed

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Qicheng Wang ◽  
Kai Zhang ◽  
Kuanli Yang ◽  
Jianchun Jiang
Keyword(s):  
Fluidized Bed ◽  
Particle Velocity ◽  
Particle Diameter ◽  
Solid Material ◽  
Dense Gas ◽  
Gas Velocity ◽  
Strong Function ◽  
Optical Fiber Probe ◽  
Inner Diameter ◽  
Particle Velocities

The upflowing and downflowing particle velocities are investigated by using a two-optical fiber probe system in the dense gas-solid fluidized bed with an inner diameter of 0.185 m and a height of 3.000 m. Two kinds of glass ballotinis, belonging to Geldart type B classification, are selected as solid material. Experiments are conducted under different operating gas velocities, static bed heights, and particle diameters. The results indicate that the upflowing particle velocity is a strong function of operating gas velocity and particle diameter, while the downflowing particle velocity depends mainly on the operating gas velocity. When the ratio of the operating gas velocity to the minimum fluidization velocity of the particles keeps the same constant, the effect of the particle diameter on the upflowing and downflowing particle velocities can be ignored. Both direction and size of the solid particle velocity are related to the bubble behaviors in the fluidized bed, and the upflowing particle velocity is lower than the bubble rise velocity. Furthermore, the across-sectional, non-uniform flow structure in the bed increases slightly with increasing static bed height at the high operating gas velocity.

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