Simultaneous particle morphology and temperature measurements of burning pulverized coal

Schroeder, Alan R.; Thompson, Daniel; Daves, Glenn G.; Buckius, Richard O.; Krier, Herman; Peters, James E.

doi:10.1016/s0082-0784(06)80137-2

Cited by 8 publications

(6 citation statements)

References 4 publications

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“…The other experiments were made at atmospheric pressure and a different gas temperature. The gas temperature in the measurements of Young et al was about 150 K lower than in the present case, while in the measurements of Schroeder et al and Mitchell and McLean it was about 150 K higher. In the measurements made by Timothy et al, Hurt, and Waters et al it was 300−550 K higher.…”

Section: Resultscontrasting

confidence: 63%

Effects of Pressure and Oxygen Concentration on the Combustion of Different Coals

et al. 1998

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A pyrometric method was used for simultaneous in situ measurement of the temperature and size of individual coal particles in a pressurized entrained flow reactor. Several series of measurements were made in the gas temperature range 1150-1270 K to study the effects of pressure (0.2-1.0 MPa) and oxygen volume fraction (3-30 vol %) on the particle temperature and size distributions and on the mean degree of burnoff at well-defined residence times. The fuels used in the experiments varied strongly in their reactivity: lignite from France (Gardanne), high-volatile bituminous (hvb) coals from Germany (Westerholt, Go ¨ttelborn) and Poland (mixture), and anthracite from Germany (Niederberg). Milled fuel was sieved into nominal-size fractions in the range from 75 to 180 µm. The strongest increase in combustion rate at increased pressure occurred for anthracite, which was the least reactive among the fuels studied. This is shown by increasing the mass-loss rate and increasing particle temperatures. Pressure had no effect on the combustion of the lignite sample, the most reactive fuel studied. Some evidence of swelling of hvb coal particles was observed during the early stages of combustion. The particle size remained roughly unchanged until the degree of burnoff exceeded 90%, whereafter the particle size started to decrease due to fragmentation. Experimental results from particle temperature measurements at various oxygen concentrations are compared with literature data. Results from in situ particle measurements including size and temperature recording have not been presented previously at elevated pressures for such a wide range of coals. Measurements on combustion rates, particle temperatures and particle sizes were analyzed with a single-particle combustion model. The effect of pressure on the surface reaction kinetics for an anthracite was found to be small compared to the oxygen content and temperature.

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Section: Resultscontrasting

confidence: 63%

Effects of Pressure and Oxygen Concentration on the Combustion of Different Coals

et al. 1998

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“…The particle temperature was measured, but additional measurement of conversion as a function of time by solid sampling and ash tracer method would have given further useful information. It has been shown − that, under certain conditions, the formation of CO 2 near the particle surface (either heterogeneously or homogeneously) must take place in order for the predicted and measured particle mass loss profiles to match.…”

Section: Resultsmentioning

confidence: 99%

Pressurized Pulverized Fuel Combustion in Different Concentrations of Oxygen and Carbon Dioxide

Saastamoinen¹,

Aho²,

Hämäläinen³

et al. 1996

Energy Fuels

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Theoretical and experimental studies showed that increasing gas pressure at constant gas composition most strongly increases the combustion rate of less reactive coals, which are difficult to burn completely in atmospheric pulverized fuel boilers. The effect of pressure increase is greatest near 0.1 MPa and less at higher pressures. The limit at which increase in pressure has an effect varies from coal to coal, depending on the particle size. With less reactive coals and small particles, the effect can be seen at pressures greater than 1 MPa. The relative effect of pressure increases when the gas oxygen content is low, improving the burnout in furnaces. The effect of pressure is small for large particles and reactive fuels. At high pressures the rates of homogeneous and heterogeneous reactions increase raising the maximum particle temperature; the higher temperature may increase the extent of devolatilization and further decrease the total combustion time. Combustion rate and the temperature of burning coal particles were measured in experiments with a pressurized entrained flow reactor under the following conditions: gas temperature 1073-1473 K, pressure 0.2-0.8 MPa, oxygen partial pressure 0.025-0.1 MPa, and partial pressure of CO 2 0.05-0.2 MPa. Measured and calculated results showed increased carbon dioxide concentration in the combustion environment to have an insignificant effect on the combustion rate in the studied temperature region, but it lowered the particle temperature to some extent, suggesting that the gasification reaction CO 2 -C takes place as well. Calculations indicated that in pressurized combustion the rate of gasification reaction is greater at higher temperatures.

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“…The pseudo particles consisted of various types including fairly regular rounded shapes, bulky shapes, and very irregular particles. The 201 images of the pseudo particles are very typical of those observed in the experiments of burning coal (Schroeder et al, 1992) and are used to assess the accuracy of the morphology generating approaches. Three views of two of the pseudo particles are shown in Figure 4.…”

Section: Results Of Morphology Estimatesmentioning

confidence: 99%

Morphology Descriptors of Irregularly Shaped Particles from Two-Dimensional Images

Daves

Buckius

Peters

et al. 1993

Aerosol Science and Technology

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Two-dimensional particle images provide significantly more information about particle morphology than does the measurement of a single length scale. However, approximations are still required to estimate three-dimensional particle parameters such as external surface area and volume from a two-dimensional image. Two techniques to predict surface area and volume from a two-dimensional image are examined by using images of objects of known surface area and volume. The orthographic intersection method intersects the two-dimensional images from all possible orthogonal axes. The resulting three-dimensional objects are averaged to obtain the final particle shape descriptors. The discrete revolution method first determines the major centroidal axis of the image and then rotates the silhouette about this axis. Because the silhouette is not symmetrical with respect to the major axis, the silhouette is divided into thin strips of area perpendicular to the major axis. Each of these strips is then rotated about its own centroidal axis (parallel to the major axis). Comparisons of the results of each method for specified particles provide estimates of the accuracy of each approach. The orthographic intersection and discrete revolution methods provide superior estimates of the surface area, volume, and surface area/volume ratio as compared with approaches using single length scale equivalent spheres. The method that provided the most accurate results was the discrete revolution technique.

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Simultaneous particle morphology and temperature measurements of burning pulverized coal

Cited by 8 publications

References 4 publications

Effects of Pressure and Oxygen Concentration on the Combustion of Different Coals

Effects of Pressure and Oxygen Concentration on the Combustion of Different Coals

Pressurized Pulverized Fuel Combustion in Different Concentrations of Oxygen and Carbon Dioxide

Morphology Descriptors of Irregularly Shaped Particles from Two-Dimensional Images

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