A Method for Reduction in the Start-Up Time of a Bubbling Bed Boiler Combustor

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Vijay Jain ◽  
Prabir Basu ◽  
Dominic Groulx
Keyword(s):  
Fluidized Bed ◽  
Internal Heat ◽  
Peak Temperature ◽  
Fuel Oil ◽  
Start Up ◽  
Bubbling Fluidized Bed ◽  
Bed Materials ◽  
The Mean ◽  
Rate Of Heating ◽  
Good Agreement

A study on the heating of inert bed solids in a bubbling fluidized bed by means of an over-bed start-up oil burner is presented in this paper. Experiments carried out in a 160 mm diameter bed shows that the bed heats up nonlinearly with time. The rate of heating and the peak temperature reached by the bed solids depend on the bed depth, the mean particle size, and the superficial velocity through the bed. It was further noted that premixing a certain amount of biomass with the inert bed solids accelerates the rate of heating, as well as increase the peak temperature attained. The internal heat generation in the biomass is found to start at temperatures as low as 200°C. Thus, premixing some biomass with inert bed materials could reduce the combustion start-up time of a fluidized bed boiler, reducing at the same time the start-up cost by saving on consumption of expensive fuel oil in the burner. Experimental data in the present laboratory-scale unit shows good agreement with those obtained earlier in an industrial fluidized bed tested with waste-coal.

Numerical Study of the Influence of Horizontal Tube Banks on the Hydrodynamics of a Dense Gas-Solid Bubbling Fluidized Bed

2003 ◽  
Vol 1 (1) ◽  
Author(s):  
Sanjib K. Das Sharma ◽  
Ratan Mohan
Keyword(s):  
Fluidized Bed ◽  
Solid Phase ◽  
Numerical Study ◽  
Horizontal Tube ◽  
Particle Interactions ◽  
Tube Bank ◽  
Bubbling Fluidized Bed ◽  
Tube Banks ◽  
Fluidizing Medium ◽  
Good Agreement

Numerical study of the influence of tube-bank on the hydrodynamics of a freely bubbling fluidized bed is relatively less reported in the literature. In this paper, results obtained from CFD study of a two dimensional gas-solid fluidized beds with horizontal tube-bank are compared with the published experimental data (Hull et. al., 1999). A 2-D bed, 1 m high and 0.2 m wide with tubes of diameter 0.026 m was taken for the calculations. Two different tube arrangements of staggered and inline pitch with center-to-center distance of 0.05 m were considered. Air was used as the fluidizing medium and ballotini glass (diameter: 230 mm and density: 2723 kg/m3) was the fluidized material. Air velocities used were 0.15 m/s and 0.187 m/s. The Eulerian-Eularian Two-Fluid CFD model was employed for modeling the momentum equations for both the gas and the solid phase with kinetic theory modification for the solid phase to account for the inter-particle interactions. Hydrodynamic features, such as, bubble size and bubble rise velocity and their variation with height within and outside the tube bank showed good agreement with the data of Hull et al.(1999)

scholarly journals Application of Pseudohomogeneous and Heterogeneous Models in Assessing the Behavior of a Fluidized-Bed Catalytic Reactor

Energies ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 208
Author(s):  
Katarzyna Bizon
Keyword(s):  
Steady State ◽  
Mathematical Models ◽  
Fluidized Bed ◽  
Catalytic Reactor ◽  
Reactor Dynamics ◽  
Catalyst Pellet ◽  
Start Up ◽  
Scale Models ◽  
Heterogeneous Models ◽  
Bubbling Fluidized Bed

Comparative analysis of the steady-state and transient properties of a bubbling fluidized-bed catalytic reactor obtained according to different mathematical models of the emulsion zone was performed to verify the commonly used assumption regarding the pseudohomogeneous nature of this zone. Four different mathematical models of the fluidized-bed reactor dynamics were formulated, based on different thermal and diffusional conditions at the gas-solid interface and within the catalyst pellet, namely the model based on the assumption of pseudohomogeneous character for the emulsion zone, and a group of two-scale models accounting for the heterogeneous character of this zone. It was demonstrated that, while the pseudohomogeneous model of the emulsion zone predicts almost identical behavior of the reactor at steady-state as the proposed heterogeneous models, it may fail in the prediction of the reactor start-up behavior, especially when dealing with highly exothermic processes run at relatively high fluidization velocity.

scholarly journals Effect of particle shape on bubble dynamics in bubbling fluidized bed

2021 ◽  
Vol 249 ◽  
pp. 06012
Author(s):  
Siddhartha Shrestha ◽  
Zongyan Zhou
Keyword(s):  
Fluidized Bed ◽  
Bubble Size ◽  
Particle Shape ◽  
Bubble Dynamics ◽  
Bubble Velocity ◽  
Aspect Ratios ◽  
Bubbling Fluidized Bed ◽  
Single Jet ◽  
Bubble Splitting ◽  
Good Agreement

Particle shape can significantly affect the bubble dynamics of bubbling fluidized beds (BFB). In this paper, findings obtained from simulations using CFD-DEM are summarized to discuss the effect of particle shape on bubble dynamics and bubble properties such as bubble size, shape and velocity at a single orifice and uniform fluidized bed. Particles with aspect ratios at 0.5 (oblate), 1 (spherical) and 2 (prolate) are employed to represent disc-like, spherical and rod-like particles, respectively. Both single jet and uniform fluidized bed simulations demonstrate that the bubble forming/rising regions, bubble coalescence locations, and bubble splitting phenomena are significantly influenced by particle shape. The CFD-DEM results for bubble size and bubble velocity show good agreement with literature correlations.

scholarly journals Numerical study of mixing and heat transfer of SRF particles in a bubbling fluidized bed

2019 ◽  
Vol 142 (2) ◽  
pp. 1087-1096
Author(s):  
Mohamed Sobhi Alagha ◽  
Botond Szucs ◽  
Pal Szentannai
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Fluidized Bed ◽  
Present Model ◽  
Numerical Study ◽  
Sand Particle ◽  
Particle Sizes ◽  
Proposed Model ◽  
Bubbling Fluidized Bed ◽  
Good Agreement

AbstractIn this article, numerical investigations on mixing and heat transfer of solid refused fuel (SRF) particles in a bubbling fluidized bed are carried out. The numerical model is based on the Eulerian–Eulerian approach with empirical submodels representing gas–solid and solid–solid interactions. The model is verified by experimental data from the literature. The experimental data include SRF vertical distribution in SRF–sand mixtures of different sand particle sizes ($$d_{\mathrm{pm}} = 654,810$$ d pm = 654 , 810 and 1110 $$\upmu$$ μ m) at different fluidization velocities ($$u/u_{\mathrm{mf}} = 1.2$$ u / u mf = 1.2 –2.0). We proposed magnification of drag force exerted by the gas on SRF particles based on Haider and Levenspiel (Powder Technol 58(1):63–70, 1989) drag coefficient. The proposed model shows good agreement with the experimental data at high fluidization velocities ( $$u/u_{\mathrm{mf}} = 1.5$$ u / u mf = 1.5 –2.0) and poor predictions at low fluidization velocities ($$u/u_{\mathrm{mf}} = 1.2$$ u / u mf = 1.2 –1.5). Heat transfer results showed that the present model is valid and gives good agreement with the experimental data of wall–bed heat transfer coefficient.

External bed materials for the oxy-fuel combustion of biomass in a bubbling fluidized bed

2021 ◽  
pp. 128882
Author(s):  
Matěj Vodička ◽  
Kristýna Michaliková ◽  
Jan Hrdlička ◽  
Cornelia Hofbauer ◽  
Franz Winter ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Fuel Combustion ◽  
Bubbling Fluidized Bed ◽  
Bed Materials

Petroleum Coke and Coal Start-Up Testing in Bubbling Fluidized Bed Combustors

1997 ◽  
Vol 119 (2) ◽  
pp. 96-102 ◽  
Author(s):  
E. J. Anthony ◽  
K. Anderson ◽  
R. Carson ◽  
I. T. Lau
Keyword(s):  
Fluidized Bed ◽  
Petroleum Coke ◽  
Bituminous Coal ◽  
Volatile Content ◽  
Fluidized Bed Combustion ◽  
Bench Scale ◽  
Start Up ◽  
Bubbling Fluidized Bed ◽  
Tennessee Valley ◽  
Start Ups

Bench-scale and 160 MWe demonstration tests were conducted for petroleum coke and high volatile bituminous coal blends. The bench-scale apparatus was a 100-mm-dia reactor located at the Canada Centre for Mineral and Energy Technology (CANMET), Energy Research Laboratories. The demonstration tests were conducted on the Tennessee Valley Authority’s (TVA) 160 MWe Shawnee Atmospheric Fluidized Bed Combustion (AFBC) Unit located at Paducah, Kentucky. Five and ten percent nominal volatile petroleum cokes were tested in the bench-scale unit. In addition, for the five-percent petroleum coke blends of 25, 50, and 75-percent petroleum coke, with the balance coal, were also examined at the bench scale. Eight start-up tests have been conducted with 50 percent blend of green delayed petroleum coke at the Shawnee AFBC unit. The bench-scale tests revealed that the volatile content in the petroleum coke was the primary factor affecting start-up. The tests showed that the volatile content from the coke and coal ignited at similar times; the char required longer to ignite. Bench-scale tests showed adequate start-up performance with blends up to 75 percent petroleum coke. Cold start-ups were conducted at the Shawnee AFBC Unit with 7 to 10 percent volatile green delayed petroleum coke. In all the start-ups, the operating temperature of 816°C was reached within 15 min of introducing the petroleum coke blend; this is similar to when high volatile bituminous coal was used. One start-up required a longer time because limestone had to be used to generate the bed. Local hot spots (982°C) were noticed in several start-ups for short periods, but subsided when additional air was supplied. Although more difficult to control, TVA routinely starts the Shawnee AFBC Unit with 50 percent shot petroleum coke and 50 percent high volatile bituminous coal.

Combustion characteristics of straw stored with CaCO3 in bubbling fluidized bed using quartz and olivine as bed materials

2018 ◽  
Vol 212 ◽  
pp. 1400-1408 ◽  
Author(s):  
Marjan Bozaghian ◽  
Anders Rebbling ◽  
Sylvia H. Larsson ◽  
Mikael Thyrel ◽  
Shaojun Xiong ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Combustion Characteristics ◽  
Bubbling Fluidized Bed ◽  
Bed Materials
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