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Research Papers: Radiative Heat Transfer

Theoretical Predictions of Spectral Emissivity for Coal Ash Deposits

[+] Author and Article Information
Dong Liu

Key Laboratory of Thermal Science and Power
Engineering of Ministry of Education,
Beijing Key Laboratory for CO2 Utilization
and Reduction Technology,
Tsinghua University,
Beijing 100084, China
e-mail: liu-d10@mails.tsinghua.edu.cn

Yuan-Yuan Duan

Key Laboratory of Thermal Science and Power
Engineering of Ministry of Education,
Beijing Key Laboratory for CO2 Utilization
and Reduction Technology,
Tsinghua University,
Beijing 100084, China
e-mail: yyduan@tsinghua.edu.cn

Zhen Yang

Key Laboratory of Thermal Science and Power
Engineering of Ministry of Education,
Beijing Key Laboratory for CO2 Utilization
and Reduction Technology,
Tsinghua University,
Beijing 100084, China
e-mail: zhenyang@tsinghua.edu.cn

Hai-Tong Yu

Key Laboratory of Thermal Science and Power
Engineering of Ministry of Education,
Beijing Key Laboratory for CO2 Utilization
and Reduction Technology,
Tsinghua University,
Beijing 100084, China
e-mail: yht09@mails.tsinghua.edu.cn

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received March 23, 2013; final manuscript received July 11, 2013; published online March 17, 2014. Assoc. Editor: Zhixiong Guo.

J. Heat Transfer 136(7), 072701 (Mar 17, 2014) (7 pages) Paper No: HT-13-1160; doi: 10.1115/1.4026907 History: Received March 23, 2013; Revised July 11, 2013

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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References

Bryers, R. W., 1996, “Fireside Slagging, Fouling, and High-Temperature Corrosion of Heat-Transfer Surface Due to Impurities in Steam-Raising Fuels,” Prog. Energy Combust. Sci., 22(1), pp. 29–120. [CrossRef]
Wall, T. F., Bhattacharya, S. P., Zhang, D. K., Gupta, R. P., and He, X., 1993, “The Properties and Thermal Effects of Ash Deposits in Coal-Fired Furnaces,” Prog. Energy Combust. Sci., 19(6), pp. 487–504. [CrossRef]
Baxter, L. L., and Desollar, R. W., 1993, “A Mechanistic Description of Ash Deposition During Pulverized Coal Combustion-Predictions Compared With Observations,” Fuel, 72(10), pp. 1411–1418. [CrossRef]
Liu, D., Duan, Y. Y., and Yang, Z., 2012, “Effects of Participating Media on the Time-Resolved Infrared Measurements of Wall Temperature in a Coal-Fired Combustor,” Exp. Therm Fluid Sci., 39, pp. 90–97. [CrossRef]
Liu, D., Duan, Y. Y., and Yang, Z., 2013, “Effects of Wake Dynamics on Infrared Measurements of Particle Cloud Temperatures in the Superheater Pendant Region of Utility Boilers,” Appl. Therm. Eng., 51(1–2), pp. 1076–1081. [CrossRef]
Liu, D., Duan, Y. Y., and Yang, Z., 2013, “Integrated Effective Emissivity Computation for Non-Isothermal Non-Axisymmetric Cavities,” Chin. Opt. Lett., 11(2), p. 022001. [CrossRef]
Liu, D., Duan, Y. Y., and Yang, Z., 2013, “Calculations of the Average Normal Effective Emissivity for Nonaxisymmetric Cavities Using the Modified Finite Volume Method,” Opt. Eng., 52(3), p. 039702. [CrossRef]
Saljnikov, A., Komatina, M., Manovic, V., Gojak, M., and Goricanec, D., 2009, “Investigation on Thermal Radiation Spectra of Coal Ash Deposits,” Int. J. Heat Mass Transfer, 52(11–12), pp. 2871–2884. [CrossRef]
Saljnikov, A., Vucicevic, B., Komatina, M., Gojak, M., Goricanec, D., and Stevanovic, Z., 2009, “Spectroscopic Research on Infrared Emittance of Coal Ash Deposits,” Exp. Therm Fluid Sci., 33(8), pp. 1133–1141. [CrossRef]
Moore, T. J., Cundick, D. P., Jones, M. R., Tree, D. R., Maynes, R. D., and Baxter, L. L., 2011, “In Situ Measurements of the Spectral Emittance of Coal Ash Deposits,” J. Quant. Spectrosc. Radiat. Transfer, 112(12), pp. 1978–1986. [CrossRef]
Bohnes, S., Scherer, V., Linka, S., Neuroth, M., and Bruggemann, H., 2005, “Spectral Emissivity Measurements of Single Mineral Phases and Ash Deposits,” ASME Paper No. HT2005-72099.
Linka, S., Wirtz, S., and Scherer, V., 2005, “Spectral Thermal Radiation Characteristics of Coal Ashes and Slags: Influence of Chemical Composition and Temperature,” ASME Paper No. HT2003-47187.
Bhattacharya, S. P., 2004, “Spectral Emittance of Particulate Ash-Like Deposits: Theoretical Predictions Compared to Experimental Measurement,” ASME J. Heat Transfer, 126(2), pp. 286–289. [CrossRef]
Shimogori, M., Yoshizako, H., and Matsumura, Y., 2012, “Determination of Coal Ash Emissivity Using Simplified Equation for Thermal Design of Coal-Fired Boilers,” Fuel, 95(1), pp. 241–246. [CrossRef]
Bhattacharya, S. P., Wall, T. F., and Arduini-Schuster, M., 1997, “A Study on the Importance of Dependent Radiative Effects in Determining the Spectral and Total Emittance of Particulate Ash Deposits in Pulverised Fuel Fired Furnaces,” Chem. Eng. Process., 36(6), pp. 423–432. [CrossRef]
Bhattacharya, S. P., 1999, “Apparent Emittance of Non-Isothermal Particulate Deposits,” Int. Commun. Heat Mass Transfer, 26(6), pp. 771–780. [CrossRef]
Bhattacharya, S. P., 2000, “A Theoretical Investigation of the Influence of Optical Constants and Particle Size on the Radiative Properties and Heat Transfer Involving Ash Clouds and Deposits,” Chem. Eng. Process., 39(5), pp. 471–483. [CrossRef]
Fiveland, W. A., 1987, “Discrete Ordinate Methods for Radiative Heat-Transfer in Isotropically and Anisotropically Scattering Media,” ASME J. Heat Transfer, 109(3), pp. 809–812. [CrossRef]
Li, H. S., Flamant, G., and Lu, J. D., 2003, “An Alternative Discrete Ordinate Scheme for Collimated Irradiation Problems,” Int. Commun. Heat Mass Transfer, 30(1), pp. 61–70. [CrossRef]
Bohren, C. F., and Huffman, D. R., 1983, Absorption and Scattering of Light by Small Particles, Wiley, New York, pp. 101–118.
Cartigny, J. D., Yamada, Y., and Tien, C. L., 1986, “Radiative-Transfer With Dependent Scattering by Particles: Part 1—Theoretical Investigation,” ASME J. Heat Transfer, 108(3), pp. 608–613. [CrossRef]
Xu, Y. L., 1995, “Electromagnetic Scattering by an Aggregate of Spheres,” Appl. Opt., 34(21), pp. 4573–4588. [CrossRef]
Meakin, P., 1983, “Formation of Fractal Clusters and Networks by Irreversible Diffusion-Limited Aggregation,” Phys. Rev. Lett., 51(13), pp. 1119–1122. [CrossRef]
Witten, T. A., and Sander, L. M., 1981, “Diffusion-Limited Aggregation, a Kinetic Critical Phenomenon,” Phys. Rev. Lett., 47(19), pp. 1400–1403. [CrossRef]
Pan, Y. D., Si, F. Q., Xu, Z. G., Romero, C. E., Qiao, Z. L., and Ye, Y. L., 2012, “DEM Simulation and Fractal Analysis of Particulate Fouling on Coal-Fired Utility Boilers' Heating Surfaces,” Powder Technol., 231, pp. 70–76. [CrossRef]
Kweon, S. C., Ramer, E., and Robinson, A. L., 2003, “Measurement and Simulation of Ash Deposit Microstructure,” Energy Fuels, 17(5), pp. 1311–1323. [CrossRef]
Goodwin, D. G., and Mitchner, M., 1989, “Flyash Radiative Properties and Effects on Radiative Heat Transfer in Coal-Fired Systems,” Int. J. Heat Mass Transfer, 32(4), pp. 627–638. [CrossRef]
Sorensen, C. M., and Roberts, G. C., 1997, “The Prefactor of Fractal Aggregates,” J. Colloid Interface Sci., 186(2), pp. 447–452. [CrossRef]
Pierce, F., Sorensen, C. M., and Chakrabarti, A., 2006, “Computer Simulation of Diffusion-Limited Cluster-Cluster Aggregation With an Epstein Drag Force,” Phys. Rev. E, 74(2), p. 021411. [CrossRef]
Zhao, J. J., Duan, Y. Y., Wang, X. D., and Wang, B. X., 2013, “Experimental and Analytical Analyses of the Thermal Conductivities and High-Temperature Characteristics of Silica Aerogels Based on Microstructures,” J. Phys. D: Appl. Phys., 46(1), p. 015304. [CrossRef]
Zhao, J. J., Duan, Y. Y., Wang, X. D., and Wang, B. X., 2013, “A 3-D Numerical Heat Transfer Model for Silica Aerogels Based on the Porous Secondary Nanoparticle Aggregate Structure,” J. Non-Cryst. Solids, 358(10), pp. 1287–1297. [CrossRef]
Lallich, S., Enguehard, F., and Baillis, D., 2009, “Experimental Determination and Modeling of the Radiative Properties of Silica Nanoporous Matrices,” ASME J. Heat Transfer, 131(8), p. 082701. [CrossRef]
Goodwin, D. G., 1986, “Infrared Optical Constants of Coal Slags,” Ph.D. thesis, Stanford University, Stanford, CA.
Bohren, C. F., and Huffman, D. R., 1983, Absorption and Scattering of Light by Small Particles, Wiley, New York, pp. 213–218.
Palik, E. D., 1985, Handbook of Optical Constants of Solids I, Academic, New York, pp. 753–763.
Toon, O. B., Pollack, J. B., and Khare, B. N., 1976, “Optical-Constants of Several Atmospheric Aerosol Species—Ammonium-Sulfate, Aluminum-Oxide, and Sodium-Chloride,” J. Geophys. Res., 81(33), pp. 5733–5748. [CrossRef]
Neely, V. I., and Kemp, J. C., 1963, “Optical Absorption in CaO Single Crystals,” J. Phys. Chem. Solids, 24(11), pp. 1301–1304. [CrossRef]
Pang, C. H., Hewakandamby, B., Wu, T., and Lester, E., 2013, “An Automated Ash Fusion Test for Characterisation of the Behaviour of Ashes From Biomass and Coal at Elevated Temperatures,” Fuel, 103, pp. 454–466. [CrossRef]
Adell, V., Cheeseman, C. R., Ferraris, M., Salvo, M., Smeacetto, F., and Boccaccini, A. R., 2007, “Characterising the Sintering Behaviour of Pulverised Fuel Ash Using Heating Stage Microscopy,” Mater. Charact., 58(10), pp. 980–988. [CrossRef]
Yang, J. G., Deng, F. R., Zhao, H., and Cen, K. F., 2007, “Mineral Conversion and Microstructure Change in the Melting Process of Shenmu Coal Ash,” Asia-Pac. J. Chem. Eng., 2(3), pp. 165–70. [CrossRef]
Zbogar, A., Frandsen, F. J., Jensen, P. A., and Glarborg, P., 2005, “Heat Transfer in Ash Deposits: A Modelling Tool-Box,” Prog. Energy Combust. Sci., 31(5–6), pp. 371–421. [CrossRef]
Markham, J. R., Best, P. E., Solomon, P. R., and Yu, Z. Z., 1992, “Measurement of Radiative Properties of Ash and Slag by FT-IR Emission and Reflection Spectroscopy,” ASME J. Heat Transfer, 114(2), pp. 458–464. [CrossRef]

Figures

Grahic Jump Location
Fig. 1

Representative 510 particle aggregate generated using the DLA method

Grahic Jump Location
Fig. 2

Comparison between experimental data and predicted spectral emissivities modeled using the original Mie theory, Tien's dependent scattering theory and the combined GMM and DLA model. (a) Sample 1 and (b) sample 2.

Grahic Jump Location
Fig. 3

Optical constants of each component in sample 1 (the absorption index of CaO is smaller than 10−6 in the present wavelength range and thus not plotted). (a) Real index and (b) absorption index.

Grahic Jump Location
Fig. 4

Comparison of the measured and optical constants predicted using Maxwell-Garnett theory for sample 1. (a) Real index and (b) absorption index.

Grahic Jump Location
Fig. 5

Comparison of spectral emissivities predicted using measured and calculated optical constants for sample 1

Grahic Jump Location
Fig. 6

Estimate effect of particle diameter on the ash deposit spectral emissivities where the particle diameter increases represent the effect of temperature

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