Total Absorptivities and Emissivities of Particulate Coal Ash From Spectral Band Emissivity Measurements

1984 ◽  
Vol 106 (4) ◽  
pp. 771-776 ◽  
Author(s):  
T. F. Wall ◽  
H. B. Becker
Keyword(s):  
Radiative Transfer ◽  
Spectral Band ◽  
Flame Temperature ◽  
Coal Ash ◽  
Spectral Emissivity ◽  
Fe2o3 Content ◽  
Ash Layer ◽  
Coal Ashes ◽  
Emissivity Measurements

Previous measurements of the spectral emissivity of coal ashes are converted to total absorptivities and emissivities. Below the temperature at which ash sinters, the total absorptivity of an ash layer—which is necessary for the estimation of radiative transfer in furnaces—is shown to depend on both the source (flame) temperature and the ash temperature. Synthetic mixtures of the oxides Al2O3, SiO2, and Fe2O3 are shown to give the same trends as those for ashes of the same Fe2O3 content.

Spectral Thermal Radiation Characteristics of Coal Ashes and Slags: Influence of Chemical Composition and Temperature

2003 ◽  
Author(s):  
S. Linka ◽  
S. Wirtz ◽  
V. Scherer
Keyword(s):  
Heat Transfer ◽  
Chemical Composition ◽  
Thermal Radiation ◽  
Coal Ash ◽  
Spectral Emissivity ◽  
Department Of Energy ◽  
Radiation Characteristics ◽  
Transfer Rates ◽  
Inorganic Species ◽  
Coal Ashes

During the combustion of pulverized coal, ash particles (formed from inorganic species) can deposit on heat-transfer surfaces, resulting in a decrease in heat transfer rates and system efficiency. In addition to the knowledge of the thermal conductivity of the deposits it is necessary to obtain information on the thermal radiation characteristics of the furnace walls to predict the influence of ash sedimentation on heat transfer. At the Department of Energy Plant Technology investigations on the spectral emissivity of different coal ashes and slags were performed applying a spectral radiometer. The samples were electrically heated. Temperatures were varied between 600 and 1400 °C. Emissivities in the range of wavelengths from 1 to 15 μm have been determined. An essential result is that coal ashes show selective thermal radiation characteristics. The main factor of influence on the emissivity is the chemical composition. Therefore, measurements on the single phases SiO2, Al2O3 and MgO were carried out and compared with the emissivity of typical coal ashes and slags. Furthermore, the emissivity depends on temperature, mainly in the wavelength range from 1 to 6 μm.

scholarly journals A model sensitivity study of the impact of clouds on satellite detection and retrieval of volcanic ash

2015 ◽  
Vol 8 (5) ◽  
pp. 1935-1949 ◽  
Author(s):  
A. Kylling ◽  
N. Kristiansen ◽  
A. Stohl ◽  
R. Buras-Schnell ◽  
C. Emde ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Liquid Water ◽  
Volcanic Ash ◽  
Spectral Band ◽  
Sensitivity Study ◽  
Transfer Model ◽  
Mass Loading ◽  
Ice Clouds ◽  
Medium Range Weather Forecast ◽  
The Impact

Abstract. Volcanic ash is commonly observed by infrared detectors on board Earth-orbiting satellites. In the presence of ice and/or liquid-water clouds, the detected volcanic ash signature may be altered. In this paper the sensitivity of detection and retrieval of volcanic ash to the presence of ice and liquid-water clouds was quantified by simulating synthetic equivalents to satellite infrared images with a 3-D radiative transfer model. The sensitivity study was made for the two recent eruptions of Eyjafjallajökull (2010) and Grímsvötn (2011) using realistic water and ice clouds and volcanic ash clouds. The water and ice clouds were taken from European Centre for Medium-Range Weather Forecast (ECMWF) analysis data and the volcanic ash cloud fields from simulations by the Lagrangian particle dispersion model FLEXPART. The radiative transfer simulations were made both with and without ice and liquid-water clouds for the geometry and channels of the Spinning Enhanced Visible and Infrared Imager (SEVIRI). The synthetic SEVIRI images were used as input to standard reverse absorption ash detection and retrieval methods. Ice and liquid-water clouds were on average found to reduce the number of detected ash-affected pixels by 6–12%. However, the effect was highly variable and for individual scenes up to 40% of pixels with mass loading >0.2 g m−2 could not be detected due to the presence of water and ice clouds. For coincident pixels, i.e. pixels where ash was both present in the FLEXPART (hereafter referred to as "Flexpart") simulation and detected by the algorithm, the presence of clouds overall increased the retrieved mean mass loading for the Eyjafjallajökull (2010) eruption by about 13%, while for the Grímsvötn (2011) eruption ash-mass loadings the effect was a 4% decrease of the retrieved ash-mass loading. However, larger differences were seen between scenes (standard deviations of ±30 and ±20% for Eyjafjallajökull and Grímsvötn, respectively) and even larger ones within scenes. The impact of ice and liquid-water clouds on the detection and retrieval of volcanic ash, implies that to fully appreciate the location and amount of ash, hyperspectral and spectral band measurements by satellite instruments should be combined with ash dispersion modelling.

scholarly journals High accuracy infrared emissivity between 50 and 1000 ᵒC for solar materials characterization

2020 ◽  
Vol 307 ◽  
pp. 01043
Author(s):  
Raquel Fuente ◽  
Telmo Echániz ◽  
Iñigo González de Arrieta ◽  
Irene Urcelay-Olabarria ◽  
Josu M Igartua ◽  
...  
Keyword(s):  
Basque Country ◽  
Temperature Stability ◽  
Spectral Emissivity ◽  
High Temperature Stability ◽  
Working Temperature ◽  
Material Efficiency ◽  
Solar Thermal Collector ◽  
Infrared Spectral ◽  
Materials Used ◽  
Emissivity Measurements

The total hemispherical emissivity of materials used in the solar energy industry is a critical parameter in the calculation of the radiative thermal losses and material efficiency, especially in solar thermal collector absorbing surfaces. This is because the radiative heat losses have a significant economic impact on the final cost of the electricity produced in solar plants. Our laboratory, HAIRL, in the University of the Basque Country (UPV/EHU) in Spain [1] is the first to have published infrared spectral emissivity measurements in Solar Absorber Surfaces (SAS) at working temperature [2]. The laboratory allows measuring between 50 and 1000 ºC in the 0.83-25 μm range and is also capable of doing directional measurements at different angles between 0 and 80 degrees. Therefore, it is suitable for measuring solar selective coatings, for studying high temperature stability and for characterizing thermal energy harvesting materials. In this presentation, we show the specifications of our laboratory, the results of spectral emissivity measurements in air-resistant solar selective coatings and in eutectic alloys for thermal storage and we demonstrate the necessity of measuring at working temperature in order to possess reliable data.

Studies on the Leaching and Weathering Processes of Coal Ashes

1983 ◽  
Vol 15 (11) ◽  
pp. 163-191 ◽  
Author(s):  
Hay Leim ◽  
Magnusöm Sandstr ◽  
Tom Wallin ◽  
Anders Carne ◽  
Ulla Rydevik ◽  
...  
Keyword(s):  
Power Plants ◽  
Coal Ash ◽  
Mass Action ◽  
Equilibrium Analysis ◽  
Metal Leaching ◽  
Magnetic Fraction ◽  
Fly Ashes ◽  
X Ray ◽  
Weathering Processes ◽  
Coal Ashes

Within the Swedish project Coal-Health-Environment (Kol-Hälsa-Mi1jö) leaching studies were made on several types of coal ashes, fly ashes, bottom ashes and scrubber sludges. Studies were made on the effects of pH, pCl, pCO3. pEDTA and pSO4, in the leaching solution on the leaching of metals from coal ashes. As a model for the leaching system, we studied the leaching of Cr, Co, Ni, tu, Zn, Mo, Se, As, Cd and Pb. The leaching of the metals was found to increase with pH for pH less than 2 and pH greater than 9, and to decrease for 2 > pH > 6. The metal leaching behaviour may in part be explained by the mass-action law. We have also made long-term leaching tests of several coal ashes from Danish and Finnish Power Plants using leaching water of different pH. The dominating crystalline phases in the different coal ashes have been identified by X-ray diffraction technique. The major species in the different coal ashes were found to be mullite (3A12.2SiO2), α-quartz (Sio2) and the iron oxides magnetite and hematite. Leaching and X-ray studies were also made on the magnetic fraction of the fly ashes. Equilibrium analysis were made on the system Me-OH-Cl-CO32− - SO42−, where Me = Cr, Co, Ni, Cu, Zn, Mo, Se, As, Cd and Pb, partly using the computer program HALTAFALL. A model for the metal leaching from a coal ash deposit will be discussed.

Spectral emissivity measurements of liquid refractory metals by spectrometers combined with an electrostatic levitator

2012 ◽  
Vol 23 (12) ◽  
pp. 125602 ◽  
Author(s):  
Takehiko Ishikawa ◽  
Yusuke Ito ◽  
Junpei T Okada ◽  
Paul-François Paradis ◽  
Yuki Watanabe ◽  
...  
Keyword(s):  
Spectral Emissivity ◽  
Refractory Metals ◽  
Electrostatic Levitator ◽  
Emissivity Measurements

Spectral emissivity measurements of Mercury's surface indicate Mg- and Ca-rich mineralogy, K-spar, Na-rich plagioclase, rutile, with possible perovskite, and garnet

2009 ◽  
Vol 57 (3) ◽  
pp. 364-383 ◽  
Author(s):  
A.L. Sprague ◽  
K.L. Donaldson Hanna ◽  
R.W.H. Kozlowski ◽  
J. Helbert ◽  
A. Maturilli ◽  
...  
Keyword(s):  
Spectral Emissivity ◽  
Emissivity Measurements

Mineralogy and Physical and Chemical Characteristics of Coal Ash from Yang Zonghai Power Plant

2010 ◽  
Vol 177 ◽  
pp. 497-501
Author(s):  
Feng Rui Zhai ◽  
Zhong Zhou Yi ◽  
Qun Cai ◽  
Huan Bin Song ◽  
Li Li Zhang ◽  
...  
Keyword(s):  
Power Plant ◽  
Particle Diameter ◽  
Coal Ash ◽  
Chemical Characteristics ◽  
Test Results ◽  
X Ray Diffraction ◽  
X Ray ◽  
Physical And Chemical Characteristics ◽  
Coal Ashes ◽  
Physical And Chemical

The modality, physical and chemical characteristics, mineralogy and distribution of particle size of coal ash were studied by modern analytic technology SEM, spectral analysis, X - ray Diffraction (XRD) and laser granularity analyzer. The test results show that the mineralogy of coal ashes is dominated mainly by mullite, quartz and hematite.The coal ash of Yang Zonghai power plant has lower content of calcium oxide and is low calcium ash.At the same time, the losing amount is low to burn.The particle diameter is small and mainly concentrates on the range of 1-40 m.

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