Combustion of dust clouds: a survey of the literature
A literature survey of the production of dust suspensions for fundamental combustion studies shows that the most effective processes are those based upon agitation of a dust bed by a gas jet, with feeding of the resulting dispersion to a burner. A serious problem in most such systems has been the failure to ensure that no particle agglomerates existed in the suspension. A device can be made which effectively deagglomerates the dust. Several theoretical discussions of thermal, convective, and radiant heat transfer to and from dust clouds show that size is of prime importance in determining the temperature history of a particle, small sizes promoting rapid heating both by conduction and convection from hot gas and also by the impingement of external radiation such as might be emitted from the combustion zone. Limited experimental work on hot flames puts the relative contribution of radiative heat transfer to the combustion rate of dusts at around 50 percent of the total. In the combustion process, experimental work confirms that small particle size favors both ease of ignition and rate of combustion. Small-scale turbulence increases the combustion rate. A combination of theory and experiment shows that increasing temperature has a strong accelerating effect upon coal and carbon combustion, up to about 1000/sup 0/C; volatile matter tends to accelerate combustion but results in a separated two-stage process involving combustion of volatiles followed by burning of the carbonaceous residue. Pulverized coal particles can be expected to burn at a rate between that of carbon particles (slower) and oil droplets (faster) of the same size distribution.
- Research Organization:
- Pennsylvania State Univ., University Park (USA). Dept. of Fuel Technology
- OSTI ID:
- 5360105
- Report Number(s):
- NP-22730
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
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Pyrolysis
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CARBONACEOUS MATERIALS
CHEMICAL REACTIONS
COAL
COAL FINES
COMBUSTION
DUSTS
ENERGY SOURCES
ENERGY TRANSFER
FLUID FLOW
FOSSIL FUELS
FUELS
HEAT TRANSFER
HEATING
IGNITION
LAMINAR FLOW
MASS TRANSFER
MEASURING METHODS
OXIDATION
PARTICLE SIZE
RADIATION HEATING
SIZE
TURBULENT FLOW