Characterization of burning char particles under pressurized conditions by simultaneous in situ measurement of surface temperature and size

Reichelt, T.; Joutsenoja, Timo; Spliethoff, Hartmut; Hein, K. R. G.; Hernberg, Rolf

doi:10.1016/s0082-0784(98)80151-3

Cited by 14 publications

(8 citation statements)

References 7 publications

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“…q rg = 0 in our experiments, since the furnace wall temperature is equal to the gas temperature. A dependence between size and temperature of char particle burning at a given gas concentration was found experimentally at Sandia National Laboratories. , Such experiments have also been reported by others. ,,− An almost linear dependence between particle size and gas oxygen content was found experimentally; Equation 5 predicts an almost linear dependence in the regime of diffusion control, but radiation and the dependence of thermal properties on temperature (see Appendix) cause some nonlinearity. The dependence between particle size and temperature can be solved from the heat balance This is almost an explicit relation between D p and T p , but φ (∼1), Nu (∼2), and Sh (∼2) depend on D p to some extent.…”

Section: Modelsupporting

confidence: 72%

“…The literature shows a wide scatter in the observed dependence of T p and D p . ,− Comparison of the results is very difficult due to the large variation in process conditions, stage of combustion, and rank of fuel. However, it can be noticed that near zero and even slightly positive slopes have been observed 7,24-26 as well as clearly negative slopes. − ,− …”

Section: Resultsmentioning

confidence: 99%

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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: Modelsupporting

confidence: 72%

Section: Resultsmentioning

confidence: 99%

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

et al. 1998

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“…4 seemed reasonable. Similar apparent discrepancies between mesh sizes and pyrometrically determined equivalent diameters were reported previously [30]. To better explain the differences between sets, it is practical to examine trends in particle temperature and size as a function of height above the burner.…”

Section: Research Articlesupporting

confidence: 72%

“…Since the properties of the particle population in a flame may affect larger-scale flame behavior in an entangled manner, knowledge of particle size distributions is important from the point of char fragmentation as well [18][19][20]. Current in situ methods for coal particle size measurement use coded aperture [17,21,22], quasi-imaging [23][24][25], holographic [26,27], or pyrometric [28][29][30] principles. Reported accuracies are around 20% for coded aperture sizing [17] or 15% for holographic techniques, although the latter has only been applied to nonreacting flows.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional combined pyrometric sizing and velocimetry of combusting coal particles II: Pyrometry

et al. 2015

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Knowledge of the in situ temperature, size, velocity, and number density of a population of burning coal particles yields insight into the chemical and aerodynamic behavior of a pulverized coal flame (e.g., through means of combustion model validation). Sophisticated and reasonably accurate methods are available for the simultaneous measurement of particle velocity and temperature; however, these methods typically produce single particle measurements in small analyzed volumes and require extensive instrumentation. We present a simple, inexpensive method for the simultaneous, in situ, three-dimensional (3D) measurement of particle velocity, number density, size, and temperature. The proposed method uses a combination of stereo imaging, 3D reconstruction, multicolor pyrometry, and digital image processing techniques. The details of theoretical and algorithmic backgrounds are presented, along with examples and validation experiments. Rigorous uncertainty quantification was performed using numerical simulations to estimate the accuracy of the method and explore how different parameters affect measurement uncertainty. This paper, Part II of two parts that discuss this method [Appl. Opt.54, 4049 (2015)], describes particle temperature and size measurement in overexposed emission images.

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“…Drop-tube furnaces have been widely used in high-pressure coal pyrolysis and char combustion studies (Lee et al, 1991;Monson, 1992;Reichelt et al, 1998;Wu et al, 2000). There are several drawbacks related to drop-tube furnaces.…”

Section: Review Of Char Oxidation Facilitiesmentioning

confidence: 99%

Fundamental Investigation of Fuel Transformations in Pulverized Coal Combustion and Gasification Technologies

Hurt¹,

Calo²,

Fletcher³

et al. 2005

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The goal of this project was to carry out the necessary experiments and analyses to extend current capabilities for modeling fuel transformations to the new conditions anticipated in next-generation coal-based, fuel-flexible combustion and gasification processes. This multi-organization, multi-investigator project has produced data, correlations, and submodels that extend present capabilities in pressure, temperature, and fuel type. The combined experimental and theoretical/computational results are documented in detail in Chapters 1-8 of this report, with Chapter 9 serving as a brief summary of the main conclusions. Chapters 1-3 deal with the effect of elevated pressure on devolatilization, char formation, and char properties. Chapters 4 and 5 deal with advanced combustion kinetic models needed to cover the extended ranges of pressure and temperature expected in next-generation furnaces. Chapter 6 deals with the extension of kinetic data to a variety of alternative solid fuels. Chapter 7 focuses on the kinetics of gasification (rather than combustion) at elevated pressure. Finally, Chapter 8 describes the integration, testing, and use of new fuel transformation submodels into a comprehensive CFD framework. Overall, the effects of elevated pressure, temperature, heating rate, and alternative fuel use are all complex and much more work could be further undertaken in this area. Nevertheless, the current project with its new data, correlations, and computer models provides a much improved basis for model-based design of next generation systems operating under these new conditions.

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Characterization of burning char particles under pressurized conditions by simultaneous in situ measurement of surface temperature and size

Cited by 14 publications

References 7 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

Three-dimensional combined pyrometric sizing and velocimetry of combusting coal particles II: Pyrometry

Fundamental Investigation of Fuel Transformations in Pulverized Coal Combustion and Gasification Technologies

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