Heat transfer through coal ash deposits

Thesis/Dissertation · Tue Jan 01 00:00:00 EST 1985

OSTI ID:7176672

Anderson, D W

A one-dimensional heat flux through ash deposits was achieved by subjecting one surface to intense irradiation from SiC electrodes and the other surface to allow temperature heat sink. Temperature profiles and effective thermal conductivities (k), which account for both conduction and radiation heat transfer, were measured. The test facility, experimental methods, and experimental results are discussed. Flyash, crushed slag and fouling deposits, and solid fouling deposits were studied, with hot surface temperatures ranging from 425 to 1420/sup 0/C and surface irradiation from 23 to 500 kW/m/sup 2/. Thermal conductivities were low, typically less than 0.5 W/m/sup 2/K at temperatures below the sintering and fusion regimes. Particle sintering and melting had considerable effect on temperature profiles and thermal conductivities. The coupled problems of coal ash deposition onto relatively cool boiler was steam tubes, the resulting deposit layer growth, and heat transfer through the deposit were modeled numerically. Temperature dependence of slag viscosity, thermal conductivity, density, and ash deposition flux were accounted for. A simplified ash deposition model was developed for the case of thermophoretically-controlled deposition. Results of a parametric study, in which the effects of ash deposit properties and operating conditions were examined, are presented in dimensionless form. Ash deposition flux, chemical composition, thermal conductivity, surface emissivity, and flame temperature were found to have the greatest effect on heat transfer rates. Correlations of numerical results for steady state heat flux as a function of the ash silica ratio, and for steady state ash deposit thickness as a function of silica ratio and thermal conductivity, are presented.

• Research Organization: Purdue Univ., Lafayette, IN (USA)
• OSTI ID: 7176672
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
ASHES
THERMAL CONDUCTIVITY
BOILERS
HEAT TRANSFER
FLY ASH
SLAGS
CHEMICAL COMPOSITION
COAL
DENSITY
DEPOSITION
HEAT FLUX
MATHEMATICAL MODELS
SILICA
SINTERING
TEMPERATURE DEPENDENCE
VISCOSITY
AEROSOL WASTES
CARBONACEOUS MATERIALS
CHALCOGENIDES
ENERGY SOURCES
ENERGY TRANSFER
FABRICATION
FOSSIL FUELS
FUELS
MATERIALS
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RESIDUES
SILICON COMPOUNDS
SILICON OXIDES
THERMODYNAMIC PROPERTIES
WASTES
014000* - Coal
Lignite
& Peat- Combustion
010800 - Coal
Lignite
& Peat- Waste Management