Submicron particulates from pulverized-coal combustion

Conference · Sun Mar 01 04:00:00 EST 1981

OSTI ID:6475884

Pennucci, J; Greif, R; Parsons, G; Robben, F; Sherman, P

During the combustion of pulverized coal the bulk of the mineral matter is converted to fly ash. A fraction of the mineral matter may be vaporized and subsequently condense, either on existing particles or by forming new particles by the process of homogeneous nucleation. The latter process results in a large number of particles in the size range 0.005 to 0.1 microns diameter; the size of typical ash particles is from 2 to 50 microns. Because of their small size the submicron particles do not contribute substantially to the total mass of fly ash and may be overlooked; however, they can be a significant fraction of the total number of particles produced and are most easily ingested into the lungs and thus may be a significant health hazard. Further, there is evidence that certain toxic trace elements are concentrated in the submicron particles, creating a greater health hazard than their prevalence would indicate. This work consists of an experimental study of the effect of heat transfer and combustion parameters on the number and size distribution of particles in the submicron range, including consideration of practical methods of their control. The parameters that have been studied are the flame temperature, cooling rate and oxygen concentration in the fuel lean range. Peak temperatures have been varied from 1900 K to 2500 K. By chaning the thermal resistance of the burner chimney wall, cooling rates of 400 Ks/sup -1/ and 700 Ks/sup -1/ were obtained during the primary cooling period. These results support evidence of the competition between homogeneous and heterogeneous nucleation of vaporized material, which has been discussed in various models of pulverized coal fly-ash formation. They indicate that there may be possibilities for control of the smallest particles by varying the cooling rates in the post flame region.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6475884
• Report Number(s): LBL-12485; CONF-810466-2
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010800 -- Coal
Lignite
& Peat-- Waste Management
014000 -- Coal
Lignite
& Peat-- Combustion
20 FOSSIL-FUELED POWER PLANTS
200202* -- Fossil-Fueled Power Plants-- Waste Management-- Noxious Gas & Particulate Emissions
AEROSOL WASTES
ASHES
BENCH-SCALE EXPERIMENTS
CARBONACEOUS MATERIALS
CHEMICAL REACTIONS
COAL
COMBUSTION
ENERGY SOURCES
EVAPORATION
FLUE GAS
FLY ASH
FOSSIL FUELS
FOSSIL-FUEL POWER PLANTS
FUELS
GASEOUS WASTES
MATERIALS
OXIDATION
PARAMETRIC ANALYSIS
PARTICLE SIZE
PHASE TRANSFORMATIONS
POWER PLANTS
QUENCHING
RESIDUES
SIZE
THERMAL POWER PLANTS
THERMOCHEMICAL PROCESSES
VAPOR CONDENSATION
WASTES