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.

Hydrodynamic Performance of a Novel Design of Pressurized Fluidized Bed Combustor

2005 ◽  
Vol 128 (2) ◽  
pp. 111-117 ◽  
Author(s):  
Alan L. T. Wang ◽  
John F. Stubington ◽  
Jiangang Xu
Keyword(s):  
Fluidized Bed ◽  
Gas Flow ◽  
Scaling Laws ◽  
Pressure Fluctuations ◽  
Gas Injection ◽  
Plug Flow ◽  
Hydrodynamic Performance ◽  
Cold Model ◽  
Circular Pattern ◽  
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 PFBC conditions. Instead of the usual horizontal distributor plate to support the bed and distribute the fluidizing gas, the fluidizing gas was injected horizontally through 8 radial ports in the cylindrical wall of the combustor. 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 the hydrodynamics of the hot bed in the PFBC facility. Under PFBC conditions, the bed operated in a stable bubbling regime and the solids were well mixed. The bubbles in the bed were effectively cloudless and no gas backmixing or slugging occurred; so the gas flow in the bed could be modeled by assuming two phases with plug flow through each phase. 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, 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 in the lower section.

Gas flow in a pressurized fluidized-bed combustor

1988 ◽  
Vol 56 (3) ◽  
pp. 157-163 ◽  
Author(s):  
J. Thýn ◽  
Z. Kolar ◽  
W. Martens ◽  
A. Korving
Keyword(s):  
Fluidized Bed ◽  
Gas Flow ◽  
Fluidized Bed Combustor

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.

Pengurangan Pelepasan Emisi dari Pembakar Lapisan Terbendalir Menggunakan Tempurung Kelapa Sawit Sebagai Bahan Api

2012 ◽  
pp. 07-11
Author(s):  
Mohammad Nazri Mohd Jaafar ◽  
Rosyida Permatasari ◽  
Mohd Nazar Yakin Mohd Sobree
Keyword(s):  
Fluidized Bed ◽  
Fuel Oil ◽  
Silica Sand ◽  
Nox Emissions ◽  
Fuel Feed ◽  
Bed Height ◽  
Excess Air ◽  
Axial Temperature ◽  
Fluidized Bed Combustor ◽  
Air Staging

Emissions released from fluidized bed combustor (FBC) are highly dependent on several operating parameters, for example, temperature, staged air, excess air, fuel feed rate, and fuel properties. This paper presents results of experiments conducted using air staging technique on a laboratory scale fluidized bed rig, using palm shells as fuel oil and silica sand as an inert medium. Silica sand was used to ensure a sustainable fuel ignition and stable combustion occurs in the FBC. Emission of CO and NOx emissions, and temperatures along the height of the bed and flue were measured. The experimental results show that the axial temperature profile along the height was proportionally reduced with bed height of FBC. CO and NOx emissions obtained exhibit lower values for the air staged combustion. Pelepasan emisi dari pembakar lapisan terbendalir (FBC) adalah sangat bergantung kepada beberapa parameter kendalian sebagai contoh: suhu, udara berperingkat, udara berlebihan, kadar suapan bahan api, dan sifat bahan api. Kertas kerja ini mempersembahkan keputusan eksperimen yang dilaksanakan menggunakan teknik pemeringkatan udara ke atas rig lapisan terbendalir skala makmal, menggunakan tempurung kelapa sawit sebagai bahan api dan pasir silika sebagai bahan perantara lengai. Pasir silica telah digunakan untuk memastikan pencucuhan bahan api mampan dan pembakaran stabil berlaku di dalam FBC. Pelepasan gas emisi CO dan NOx serta suhu sepanjang ketinggian pembakar dan juga dalam serombong diukur. Keputusan ujikaji menunjukkan bahawa profil suhu paksi berkurangan secara berkadaran sepanjang ketinggian FBC. Pelepasan CO dan NOx yang diperolehi mempamerkan nilai yang lebih rendah untuk keadaan pembakaran dengan pemeringkatan udara.

Effect of Gas Injection with Multi-hole Orifices on Bubble Behavior during Metal Refining

2011 ◽  
Vol 233-235 ◽  
pp. 1940-1945
Author(s):  
Fang Jiang ◽  
Guo Guang Cheng ◽  
Hai Kuo Yang
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Radial Direction ◽  
Gas Injection ◽  
Hole Diameter ◽  
Bubble Coalescence ◽  
Gas Flow Rate ◽  
Bubble Behavior ◽  
Cold Model ◽  
Optimal Distance

Cold model experiments have been conducted to make clear the effect of orifices on bubble behavior based on the comparison of 1-hole and 4-hole configurations. It is found that this effect is closely related to the gas flow rate and the orifice configuration. For 1-hole orifices, bubble behavior is influenced by the hole diameter at low gas flow rate. Nevertheless, in the region of high gas flow rate, this effect becomes less obvious. However, bubble behavior is strongly affected even at high gas flow rate when 4-hole orifices are used. It is also shown there exists an optimal distance between holes for 4-hole orifices. Below this value, the hole distance is too small to adequately avoid bubble coalescence in the radial direction. Above this value, little further contribution to avoidance of bubble coalescence can be made, but weight and cost of the orifices will increase.

scholarly journals An accurate lumped convective plus radiative heat exchanger model for performance-based modelling

2021 ◽  
Vol 347 ◽  
pp. 00007
Author(s):  
Wim Fuls
Keyword(s):  
Heat Exchanger ◽  
Gas Flow ◽  
Scaling Laws ◽  
Scaling Law ◽  
Process Conditions ◽  
Particle Radiation ◽  
Gas Radiation ◽  
Base Process ◽  
Fluid Process ◽  
Improved Model

There are several thermo-fluid process modelling tools available on the market which can be used to analyze the off-design performance of thermal plants. These tools all offer the user with a simple convective heat exchanger component that requires the design-base process conditions as inputs. The tools would then calculate an effective overall heat transfer factor (UA) and make use of gas flow mass ratios to scale the UA value for off-design conditions. The models employed in these tools assume that the contribution of gas radiation is insignificant, hence only applies convection scaling laws. This paper presents an improved model which considers the contribution of the gas and particle radiation, as is often encountered in the first few heaters in coal fired boilers and heat recovery steam generators. A more fundamental scaling law is applied for the convection scaling and incorporates a cleanliness factor which allows for the consideration of fouling of the heater surfaces. The model’s performance was validated against a discretized tube-level heater model that solves the fundamental convection and radiation terms. The model is accurate within 1% for the cases considered, as compared to more than 20% error if radiation contribution is not considered.

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