Investigation of unburned carbon particles in fly ash by means of laser light scattering
A new optical method to determine the percentage of unburned carbon particles in fly ash from combustion of pulverized coal has been developed. The technique exploits the different properties of particles of ash and coal in the elastic scattering of polarized light.
The polarization measurements were performed using a linearly polarized laser source and a receiving system able to simultaneously detect the scattered radiation polarized in parallel and orthogonal planes, under the scattering angle of 60°. The parallel and perpendicular components of the scattered light intensities are measured in order to determine the polarization ratio. The operation of the system was tested under various conditions using monodisperse glass spheres. The performance of the novel device was assessed in several sets of measurements with samples of fly ash produced from coal fired power plants.
A correlation between the relative content of coal and ashes and the polarization ratio of scattered light was demonstrated. The resulting polarization ratio showed values ranging from 1.25 to 0.94 for a carbon content of 1.17 wt% and 16.3 wt%, respectively. The uncertainty on the measured percentage of unburned carbon was about 1%.
The proposed device represents an attractive tool for monitoring real-time burnout and combustion efficiency.
KeywordsBrewster Angle Polarization Ratio Depolarization Ratio Unburned Carbon Angular Aperture
Unable to display preview. Download preview PDF.
- 1.International Energy Outlook 2009, Chapter 4—coal. Report DOE/EIA-0484 (2009) Google Scholar
- 2.L. Douglas Smoot, Fundamentals of Coal Combustion: For Clean and Efficient Use (Elsevier, Amsterdam, 1993) Google Scholar
- 3.A.M. Carpenter, S. Niksa, D. Scott, Z. Wu, IEA clean coal centre (2007). www.coalonline.org/catalogues/coalonline/81591/6247/html/6247.html
- 7.L.K.A. Sear, The Properties and Use of Coal Fly Ash (Thomas Telford Ltd., 2001) Google Scholar
- 8.Federal Highway Administration, Coal fly ash in user guidelines for byproduct and secondary use materials in pavement construction. Report FHWA-RD-97-148, Turner Fairbank Highway Research Center (2008). www.recycledmaterials.org/tools/uguidelines/index.asp
- 9.ASTM standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete C618-05, 04.02, American Society for Testing Materials (2010) Google Scholar
- 10.European Committee for Standardization, Brussels, Fly ash for concrete. Part 1. Definition, specifications and conformity criteria (EN 450-1) (2005) Google Scholar
- 11.M.P. Martinez, Apparatus and processing for removing unburned carbon in fly ash. US Patent 5,555,821 (1996) Google Scholar
- 13.ASTM C311-07 standard test methods for sampling and testing fly ash or natural pozzolans for use in portland-cement concrete C311-07, 04.02. American Society for Testing Materials (2010) Google Scholar
- 14.N.J. Harris, K.C. Hover, K.J. Folliard, T. Ley, J. ASTM Int. 3, 12 (2006) Google Scholar
- 15.R.C. Brown, Method and apparatus of measuring unburned carbon in fly ash. US Patent 5,069,551 (1991) Google Scholar
- 17.N.G. Cutmore, Determination of carbon in fly ash from microwave attenuation and phase shift. US Patent 5,177,444 (1993) Google Scholar
- 18.T. Melick, T. Sommer, H. Conrads, in Conference on Unburned Carbon on Utility Fly Ash (2005). www.netl.doe.gov/publications/proceedings/05/UBC/pdf/Melick_paper.pdf Google Scholar
- 19.E. Peltonen, A. Somerikko, T. Viitanen, Procedure and means for measuring the coal content in quick ash. US Patent 4,498,338 (1983) Google Scholar
- 20.L. Mortensen, G. Sotter, Power Eng. 93, 33 (1989) Google Scholar
- 24.C.F. Bohren, D.R. Huffman, Absorption and Scattering of Light by Small Particles (Wiley, New York, 1983) Google Scholar
- 26.R. Calabria, P. Massoli, in Laser Diagnostics in Combustion, 1 edn., ed. by M. Lackner (ProcessEng Engineering GmbH, 2009), pp. 11–32 Google Scholar
- 29.H.C. van de Hulst, Light Scattering by Small Particles (Wiley, New York, 1957) Google Scholar
- 30.M. Kerker, The Scattering of Light and Other Electromagnetic Radiation (Academic Press, New York, 1969) Google Scholar
- 32.F. Beretta, A. Cavaliere, A. D’Alessio, Proc. Combust. Inst. 20, 1249 (1984) Google Scholar
- 34.A. D’Alessio, F. Beretta, P. Massoli, M. Lazzaro, in Physical and Chemical Aspects of Combustion, ed. by F.L. Dryer, R.F. Sawyer, (Gordon & Breach, New York, 1997), pp. 317–351 Google Scholar
- 36.A.F. Sarofim, Proc. Combust. Inst. 21, 1 (1986) Google Scholar
- 37.R.P. Gupta, T.F. Wall, Combust. Sci. Technol. 61, 145 (1985) Google Scholar