Mixing and combustion in a coal-limestone fluidized bed combustor
Task 1 was to investigate experimentally the characteristics of solids mixing between coal and limestone in a cold fluidized bed; Task 2 was to derive a model to describe the behavior of solids mixing observed in Task 1; and Task 3 was to develop a combustor model, which couples the mixing model derived in Task 2 with a combustion model, to simulate the mixing and combustion behavior in a hot coal-limestone fluidized bed combustor. In Task 1, the experiments were carried out in a 0.203 m diameter cold fluidized bed with coal and limestone of different sizes the the fluidized particles. Experimental parameters examined included operation time, air flow rate, bed height, initial bed setup, relative particle size and relative amount of the two particles. In the second task, the mixing model considered the downward or upward movement of a particle in the bed as being governed by certain probability laws; these laws were, in turn, affected by the bubbles. The distance of the upward movement was governed by the residence time of a particle staying in a bubble wake; the distance of downward movement, however, was determined from a material balance consideration. In all, the model took into account the effects of time, flow rate, initial bed setup and relative particle size on solids mixing. Dynamic coal concentration profiles under different operating conditions were generated by the simulation and were found to represent the experimental data reasonably well. In addition to the operation parameters included in Tasks 1 and 2, the model developed in Task 3 also considered the inlet size distribution of coal, size reduction of coal due to combustion and coal elutriation. This model was a capable of predicting the dynamic mixing and combustion behavior in a combustor under specific operation conditions.
- Research Organization:
- Lamar Univ., Beaumont, TX (USA)
- OSTI ID:
- 5722130
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
014000* -- Coal
Lignite
& Peat-- Combustion
AIR FLOW
BUBBLES
CARBONACEOUS MATERIALS
CARBONATE ROCKS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COAL
COMBUSTION
COMBUSTION KINETICS
COMBUSTORS
DIMENSIONS
ELUTRIATION
ENERGY SOURCES
FLOW RATE
FLUID FLOW
FLUID MECHANICS
FLUIDIZATION
FLUIDIZED BEDS
FLUIDIZED-BED COMBUSTION
FLUIDIZED-BED COMBUSTORS
FOSSIL FUELS
FUELS
GAS FLOW
KINETICS
LIMESTONE
MASS TRANSFER
MATERIALS
MATHEMATICAL MODELS
MECHANICS
MIXING
OXIDATION
PARTICLE SIZE
QUANTITY RATIO
REACTION KINETICS
ROCKS
SEDIMENTARY ROCKS
SEPARATION PROCESSES
SIZE
SOLIDS FLOW
THERMOCHEMICAL PROCESSES
TIME DEPENDENCE