In situ measurements of the spectral emittance of coal ash deposits

Moore, Travis J.; Cundick, Darron P.; Jones, Matthew R.; Tree, Dale R.; Maynes, R. Daniel; Baxter, Larry

doi:10.1016/j.jqsrt.2011.04.013

Cited by 10 publications

(9 citation statements)

References 10 publications

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“…Bhattacharya and Wall 18 report an increasing total emittance with increasing carbon content of the ash and a tendency to a more gray body behavior (carbon content of the ash was rather high with approximately 50 mass %). Moore et al 19 presented in situ measurements of spectral emittance of coal ashes in the outlet of a laboratory scale downfired entrained flow reactor. They also highlight the influence of iron content and physical ash structure on emittance.…”

Section: Introductionmentioning

confidence: 99%

Influence of Carbonate Decomposition on Normal Spectral Radiative Emittance in the Context of Oxyfuel Combustion

Gorewoda

Scherer

2016

Energy Fuels

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To investigate whether the radiative properties of carbonate rich ash layers in oxyfuel combustion systems might be influenced by the carbonate decomposition to the corresponding oxide, the emittance of Sr, Mg, and Ca carbonates is examined. In addition "synthetic coal ashes" were produced from mixtures of CaCO 3 and SiO 2 as well as Fe 2 O 3 and SiO 2 . The mixture ratios of the minerals were varied. All samples were prepared from powders with known particle size fractions of x < 32 μm and 125 < x < 160 μm. The powders were investigated for their temperature-dependent normal emittance in a radiation test rig by FT-IR spectroscopy in the temperature range from 500 to 1000 °C. The results reveal that the phase transformation from the carbonate to the corresponding oxide has a significant influence on spectral emittance. Whereas the carbonates show characteristic peaks in spectral emittance around 4 μm which stem from the infrared active CO 3 group, these peaks vanish after transformation to the oxide. For CaCO 3 , the most prominent carbonate in typical coal ashes, the emittance of the oxide is significantly lower than for the carbonate. Such a behavior in terms of total and spectral emittance has also been detected, for example, examining a Ca rich Rhenish lignite. Emittance increases with particle size for all samples. An enrichment of SiO 2 with Fe 2 O 3 leads to an increase in emittance.

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Section: Introductionmentioning

confidence: 99%

Influence of Carbonate Decomposition on Normal Spectral Radiative Emittance in the Context of Oxyfuel Combustion

Gorewoda

Scherer

2016

Energy Fuels

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“…Given that the absorption index of carbon is three orders of magnitude higher than that of pure ash at wavelengths below 4 μm, the char/ash particle cluster spectral emittance at short wavelengths is sensitive to the unburned carbon concentrations and insensitive to the mineral content and coal rank. The fly ash cluster spectral emittance has been measured on-line by Moore et al 47 . Therefore, this paper provides implications that the char/ash particle cluster spectral emittance method is a promising route for unburned carbon concentration on-line measurements that is independent of the mineral content and coal rank effects.…”

Section: Resultsmentioning

confidence: 99%

A New Route for Unburned Carbon Concentration Measurements Eliminating Mineral Content and Coal Rank Effects

Liu

Duan

Yang

et al. 2014

Sci Rep

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500 million tons of coal fly ash are produced worldwide every year with only 16% of the total amount utilized. Therefore, potential applications using fly ash have both environmental and industrial interests. Unburned carbon concentration measurements are fundamental to effective fly ash applications. Current on-line measurement accuracies are strongly affected by the mineral content and coal rank. This paper describes a char/ash particle cluster spectral emittance method for unburned carbon concentration measurements. The char/ash particle cluster spectral emittance is predicted theoretically here for various unburned carbon concentrations to show that the measurements are sensitive to unburned carbon concentration but insensitive to the mineral content and coal rank at short wavelengths. The results show that the char/ash particle cluster spectral emittance method is a novel and promising route for unburned carbon concentration on-line measurements without being influenced by mineral content or coal rank effects.

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“…2 for two ash deposit samples. The results are not compared with other experimental data [8][9][10][11][12] due to the lack of sufficient information conceming the ash deposits. The results are not compared with other experimental data [8][9][10][11][12] due to the lack of sufficient information conceming the ash deposits.…”

Section: Effects Of Mierostructurementioning

confidence: 99%

“…Saljnikov et al [8,9] measured temperature dependent total and spectral emissivities for four kinds of ash deposits for temperatures from 560 to 1460 K. Moore et al [10] measured in situ spectral emissivities of ash deposits formed by burning bituminous and sub-bituminous coals. Saljnikov et al [8,9] measured temperature dependent total and spectral emissivities for four kinds of ash deposits for temperatures from 560 to 1460 K. Moore et al [10] measured in situ spectral emissivities of ash deposits formed by burning bituminous and sub-bituminous coals.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Predictions of Spectral Emissivity for Coal Ash Deposits

Liu

Duan

Yang

et al. 2014

Journal of Heat Transfer

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Coal ash inevitably forms deposits as combustion residue on the walls and heat transfer surfaces of coal-fired boilers. Ash deposits decrease the boiler efficiency, reduce the generating capacity, and cause unscheduled outages. The radiative heat transfer is the major heat transfer mechanism in utility boilers: thus, the ash deposit emissivity is critical to boiler efficiency and safety. This paper presents a radiative transfer model to predict the spectral emissivities of coal ash deposits. The model includes the effects of the microstructure, chemical composition, and temperature. Typical ash deposit microstructures are generated using diffusion-limited aggregation (DLA). The radiative properties are then calculated using the generalized multiparticle Mie-solution (GMM). The combined GMM and DLA model predicts spectral emissivity better than the original Mie theory and Tien's dependent scattering theory with the average relative difference between predicted results and experimental data decreasing from 17.8% to 9.1% for sample 1 and from 18.6% to 4.2% for sample 2. Maxwell-Garnett (MG) effective medium theory is used to calculate the ash deposit optical constants based on the chemical compositions to include the effect of chemical composition. Increasing temperatures increase the particle diameters and particle volume fractions and, thus, the spectral emissivities. The spectral emissivity ultimately remains constant and less than one. The homogeneous slab model gives the upper limit of the ash deposit spectral emissivity.

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In situ measurements of the spectral emittance of coal ash deposits

Cited by 10 publications

References 10 publications

Influence of Carbonate Decomposition on Normal Spectral Radiative Emittance in the Context of Oxyfuel Combustion

Influence of Carbonate Decomposition on Normal Spectral Radiative Emittance in the Context of Oxyfuel Combustion

A New Route for Unburned Carbon Concentration Measurements Eliminating Mineral Content and Coal Rank Effects

Theoretical Predictions of Spectral Emissivity for Coal Ash Deposits

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