Experimental and Theoretical Information on Solid Flow in a Circulating Fluidized Bed

1995 ◽  
Vol 117 (2) ◽  
pp. 133-141
Author(s):  
F. R. Steward ◽  
M. F. Couturier ◽  
S. Poolpol ◽  
S. Wang
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Equations Of Motion ◽  
Flow Patterns ◽  
Operating Conditions ◽  
Laboratory Scale ◽  
Experimental Results ◽  
Solid Flow ◽  
Model Based ◽  
Fundamental Equations

Data are presented on a laboratory-scale circulating fluidized bed for various column geometries, solid fluxes, and gas velocities. Particular attention is paid to the solid flux profiles under various operating conditions. A model based on the fundamental equations of motion has been developed to describe the flow patterns of the solids particles and gas within a circulating fluidized bed. The predictions of the model are compared with experimental results. The model predicts that instabilities at the base of the bed propagate up the column for significant distances before uniform flows of solids and gas are established.

Attrition Behavior of Coal Ash Under Circulating Fluidized Bed Combustion Conditions

2003 ◽  
Author(s):  
Franz Winter ◽  
Xin Liu
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Coal Ash ◽  
Operating Conditions ◽  
Laboratory Scale ◽  
Silica Sand ◽  
Electrical Heating ◽  
Fluidized Bed Combustion ◽  
Bed Temperature ◽  
Wide Range

The attrition behavior of ash produced from two bituminous and one anthracite coal was studied under laboratory-scale circulating fluidized bed combustor (CFBC) conditions. After the ash was produced in the oven, the ash sample with a size range from 0.1 to 1 mm was fed into the hot CFBC, which was heated by electrical heating shells and fluidized by air. The laboratory-scale CFBC was operated with using fine silica sand (40 to 80 μm) as bed material. After a certain time the operation was stopped, all particles were collected and sieving analysis was performed to obtain the actual particle size distribution (PSD) of the coal ash. The operating conditions were changed in a wide range, i.e. the bed temperature from 600 to 850°C, the fluidizing velocity from 1.2 to 2 m/s, the residence time from 60 to 120 min and the design of the cyclone. The effects of operating conditions and coal type were studied and their relative importance is discussed. Elemental analysis of the coal ashes showed that Si and Ca may play an important role during attrition.

Gas and solid flow patterns in the loop-seal of a circulating fluidized bed

2014 ◽  
Vol 264 ◽  
pp. 197-202 ◽  
Author(s):  
Piero Bareschino ◽  
Roberto Solimene ◽  
Riccardo Chirone ◽  
Piero Salatino
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Flow Patterns ◽  
Solid Flow

Co-Combustion of Biomass and Coal in Circulating Fluidized Bed: Modeling and Validation

2003 ◽  
Author(s):  
Juan Ada´nez ◽  
Luis F. de Diego ◽  
Pilar Gaya´n ◽  
Francisco Garci´a-Labiano ◽  
Andre´s Cabanillas ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Plug Flow ◽  
Weighted Average ◽  
Combustion Efficiency ◽  
Operating Conditions ◽  
Experimental Results ◽  
Hydrodynamic Characteristics ◽  
Particle Model ◽  
Carbon Combustion

In this work carbon combustion efficiencies in circulating fluidized bed combustion (CFBC) when co-firing biomass and coal mixtures were studied. Experimental results were obtained from the combustion of two kind of coals with a forest residue (Pine bark) in a CBF pilot plant (0.3MWth) with 20-cm i.d. and 6.5-m height. The effect of operating conditions such as percentage of biomass in the feed, temperature, excess air, air velocity and percentage of secondary air on carbon combustion efficiency was studied. A mathematical model for the co-combustion of coal and biomass in a circulating fluidized bed boiler has been developed. The riser is divided in three zones with different hydrodynamic characteristics: bottom, splash and freeboard. The bottom bed has a constant voidage, determined by a modified two-phase theory. The solids are considered in perfect mixing and the gas in plug flow. The voidage in the splash region follows an exponential decay model. In the freeboard region, the solids and the gas are in plug flow, and a core-annulus structure is considered. Devolatilization of solid fuels is modeled with a particle reaction model which allows to determine the volatiles generation rate as a function of time and operating conditions. Kinetics of char combustion is modeled with the shrinking particle model with mixed control by chemical reaction and gas film diffusion, assuming that the ashes separate once formed. To consider that the char particles are a mixture of coal and biomass char particles, a weighted average combustion rate is defined taking into account the individual combustion rates. Population balances of char particles in the different regions were developed to calculate carbon concentrations. The developed model can predict the different gas concentrations along the riser, such as oxygen, SO2, CO, CH4, etc..., and the carbon combustion efficiency. The experimental results of carbon combustion efficiencies and gas emissions were compared with those predicted by the model and a good correlation was found for all the conditions used.

scholarly journals Study on Powder Coke Combustion and Pollution Emission Characteristics of Fluidized Bed Boilers

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1424 ◽  
Author(s):  
Chen Yang ◽  
Haochuang Wu ◽  
Kangjie Deng ◽  
Hangxing He ◽  
Li Sun
Keyword(s):  
Power Plant ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Operating Conditions ◽  
Fluidized Bed Reactors ◽  
Solid Flow ◽  
Factors Affecting ◽  
Particle In Cell ◽  
Pollutant Discharge ◽  
Pic Method

The fluidized reactor is widely used in a number of chemical processes due to its high gas-particle contacting efficiency and excellent performance on solid mixing. An improved numerical framework based on the multiphase particle-in-cell (MP-PIC) method has been developed to simulate the processes of gas–solid flow and chemical reactions in a fluidized bed. Experiments have been carried out with a 3-MW circulating fluidized bed with a height of 24.5 m and a cross section of 1 m2. In order to obtain the relationship between pollutant discharge and operating conditions and to better guide the operation of the power plant, a series of tests and simulations were carried out. The distributions of temperature and gas concentration along the furnace from simulations achieved good accuracy compared with experimental data, indicating that this numerical framework is suitable for solving complex gas–solid flow and reactions in fluidized bed reactors. Through a series of experiments, the factors affecting the concentration of NOx and SOx emissions during the steady-state combustion of the normal temperature of powder coke were obtained, which provided some future guidance for the operation of a power plant burning the same kind of fuel.

Behavior of gas-solid flow in the downcomer of a circulating fluidized bed reactor with a V-valve

1997 ◽  
Vol 91 (1) ◽  
pp. 11-16 ◽  
Author(s):  
Youchu Li ◽  
Yongqi Lu ◽  
Fengming Wang ◽  
Kai Han ◽  
Wensheng Mi ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Fluidized Bed Reactor ◽  
Solid Flow

Investigation of turbulent gas-solid flow multi-scale dynamic in circulating fluidized bed riser

2020 ◽  
Author(s):  
Ricardo Nava de Sousa ◽  
Julia Volkmann ◽  
Cristian Ricardo Schwatz ◽  
Christine Boos ◽  
Rodrigo Koerich Decker ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Solid Flow ◽  
Multi Scale
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