Mathematical modeling and experimental study of gas/solid flows and combustion in the vortexing fluidized-bed combustor (VFBC) freeboard
A new solid fuel combustion technique, known as Vortexing Fluidized Bed Combustion (VFBC), was recently developed to increase the combustion intensity, calcium utilization, and turndown capability, and to reduce the freeboard height, elutriation of fines, and emission of pollutants for small- and medium-scale boiler applications. A modified Algebraic Stress turbulent Model (ASM) was proposed for the non-isotropic turbulent swirling gas flow. Trajectory-Statistical particle Model (TSM) was newly developed to deal with particle cloud suspension. The detailed formulations were given in cylindrical coordinates for axisymmetric flows. The effects of chamber Swirl number and geometry of exhaust pipe on isothermal gas flow were discussed. The gas combustion calculation showed a strong tangential secondary injection should be used for reacting flow in order to maintain a desired hydrodynamics characteristic in VFBC freeboard. A parametric study of particle dynamic behavior in the VFBC freeboard was conducted. The results showed that the particle flow pattern is strongly affected by the particle momentum transfer number, Froude number, gas velocity field, and particle initial radial locations. The particle average velocities, bulk density distribution, particle velocity, and size spectra in the VFBC freeboard were also calculated and discussed. Four VFBC cold test models (4, 7, 10, and 18 in diameters) were designed, fabricated, and tested. The measurements of gas flow field, particle mass flux, size distribution and elutriation rate were conducted. The tangential secondary injection, combined with a specially designed exhaust pipe, can largely prolong the particle residence time and significantly reduced the fines elutriation.
- Research Organization:
- Catholic Univ. of America, Washington, DC (USA)
- OSTI ID:
- 7034665
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
014000* -- Coal
Lignite
& Peat-- Combustion
AIR POLLUTION ABATEMENT
ASHES
CARBONACEOUS MATERIALS
CARBONATE ROCKS
CHEMICAL REACTIONS
COAL
COMBUSTION
COMBUSTORS
DENSITY
EFFICIENCY
ELUTRIATION
ENERGY SOURCES
FLUID FLOW
FLUID MECHANICS
FLUIDIZED-BED COMBUSTION
FLUIDIZED-BED COMBUSTORS
FOSSIL FUELS
FUELS
GEOMETRY
HYDRODYNAMICS
LIMESTONE
MATERIALS
MATHEMATICAL MODELS
MATHEMATICS
MECHANICS
OXIDATION
PARTICLE SIZE
PARTICLES
PERFORMANCE TESTING
PHYSICAL PROPERTIES
POLLUTION ABATEMENT
RESIDUES
ROCKS
SEDIMENTARY ROCKS
SEPARATION PROCESSES
SIZE
TESTING
THERMOCHEMICAL PROCESSES
TIME DEPENDENCE
TURBULENT FLOW
VELOCITY
VORTEX FLOW