Effect of soot on pyrometric measurements of coal-particle temperature
Multiple wavelength pyrometers have been used by many investigators for the measurement of temperature of solid phase suspensions in flames. It is known that this temperature may differ from that of the surrounding gas by hundreds of degrees due to transient heating and chemical reactions. Recent observations of burning coal particles indicate that during the devolatilization phase, a highly luminous mantel can exist about the particles due to soot which is formed in the boundary layer or wake. This paper analyzes the effect a uniform soot cloud about the coal particle has on the temperature inferred from radiant emission measurements. The emissive power from the nonisothermal coal/soot system is computed relative to the power emitted by the coal particle alone as a function of the soot properties, volume fraction, soot cloud diameter, and differences in temperature. The soot greatly increases the effective temperature if it is more than 200 K above the coal surface temperature and can, under some circumstances, lead to an inferred temperature greater than either the soot or coal particle temperature. The effect is reduced as the optical thickness of the cloud is diminished, and for soot volume fractions below about 10/sup -6/ the error created by the soot is usually less than 100 K. It is concluded that measurements in the infrared are much preferable to the visible, and that the wavelength ratio for a two-color system is not a critical parameter. To improve confidence in the particle temperature indicated, it is recommended that a two-color measurement be made in each of two widely separated spectral regions and that the results be compared.
- Research Organization:
- Washington State Univ., Pullman (USA). Dept. of Mechanical Engineering
- DOE Contract Number:
- FG22-80PC30216
- OSTI ID:
- 6768464
- Report Number(s):
- DOE/PC/30216-4; CONF-821035-1; ON: DE83000910
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
014000* -- Coal
Lignite
& Peat-- Combustion
CARBONACEOUS MATERIALS
CHARS
CHEMICAL REACTIONS
COAL
COMBUSTION
ENERGY SOURCES
FLAMES
FOSSIL FUELS
FUELS
MATERIALS
MATTER
MEASURING INSTRUMENTS
OPERATION
OPTICAL PYROMETERS
OXIDATION
PARTICLES
PYROLYSIS PRODUCTS
PYROMETERS
RECOMMENDATIONS
SOOT
TEMPERATURE MEASUREMENT
THERMOCHEMICAL PROCESSES
VOLATILE MATTER