Characterization of Size and Density Separated Fractions of a Bituminous Coal as a Feedstock for Entrained Slagging Gasification


Coal is one of the main sources of energy in many parts of the world and has one of the largest reserves/production ratios amongst all the non-renewable energy sources. Gasification of coal is one among the advanced technologies that has potential to be used in a carbon constrained economy. However, gasification availability at several commercial demonstrations had run into problems associated with fouling of syngas coolers due to unpredictable flyash formation and unburnt carbon losses. Computer models of gasifiers are emerging as a powerful tool to predict gasifier performance and reliability, without expensive testing. Most computer models used to simulate gasifiers tend to model coal as a homogenous entity based on bulk properties. However, coal is a heterogeneous material and comminution during feedstock preparation produces particle classes with different physical and chemical properties. It is crucial to characterize the heterogeneity of the feedstocks used by entrained flow gasifiers. To this end, a low ash US bituminous coal that could be used as a gasifier feedstock was segregated into density and size fractions to represent the major mineral matter distributions in the coal. Float and sink method and sieving were employed to partition the ground coal. The organic and inorganic content of all density fractions was characterized for particle size distribution, heating value, ultimate analysis, proximate analysis, mineral matter composition, ash composition, and petrographic components, while size fractions were characterized for heating value, ash composition, ultimate and proximate analysis. The proximate, ultimate and high heating value analysis showed that variation in these values is limited across the range of size fractions, while the heterogeneity is significant over the range of density fractions. With respect to inorganics, the mineral matter in the heavy density fractions contribute significantly to the ash yield in the coal while contributing very little to its heating value. The ash yield across the size fractions exhibits a bimodal distribution. The heterogeneity is also significant with respect to the base-to-acid ratio across the size and density fractions. The results indicate that the variations in organic and inorganic content over a range of density and size classes are significant, even in the low ash, vitrinite rich coal sample characterized here. Incorporating this information appropriately into particle population models used in gasifier simulations will significantly enhance their accuracy of performance predictions.

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N. Soundarrajan, N. Krishnamurthy and S. Pisupati, "Characterization of Size and Density Separated Fractions of a Bituminous Coal as a Feedstock for Entrained Slagging Gasification," International Journal of Clean Coal and Energy, Vol. 2 No. 4, 2013, pp. 58-67. doi: 10.4236/ijcce.2013.24007.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] Electricity in the United States, 2013.
[2] BP Statistical Review of World Energy, 2012.
[3] S. Shelley, “Coal Gasification Comes of Age,” Chemical Engineering Progress, Vol. 102, No. 6, 2006, pp. 6-10.
[4] L. Wang, Y. Yang, T. Morosuk and G. Tsatsaronis, “Advanced Thermodynamic Analysis and Evaluation of a Supercritical Power Plant,” Energies, Vol. 5, No. 6, 2012, pp. 1850-1863.
[5] R. Gupta, “Advanced Coal Characterization:? A Review,” Energy & Fuels, Vol. 21, No. 2, 2007, pp. 451-460.
[6] M. Massoudi and P. Wang, “Slag Behavior in Gasifiers. Part II: Constitutive Modeling of Slag,” Energies, Vol. 6, No. 2, 2013, pp. 807-838.
[7] Tampa Electric Integrated Gasification Combined Cycle Project, Project Performance Summary, Tampa, 2004.
[8] Duke Energy’s Edwardsport IGCC Powerplant Begins Commercial Operation, 2013.
[9] R. C. Neavel, “Origin, Petrography and Classification of Coal. Chemistry of Coal Utilization,” In: M. A. Elliott, Ed., John Wiley and Sons, New York, 1981.
[10] K. E. Benfell, et al., “Modeling Char Combustion: The Influence of Parent Coal Petrography and Pyrolysis Pressure on the Structure and Intrinsic Reactivity of Its Char,” Proceedings of the Combustion Institute, Vol. 28, 2000, pp. 2233-2241.
[11] T. F. Wall, et al., “The Temperature, Burning Rates and Char Character of Pulverised Coal Particles Prepared from Maceral Concentrates,” Symposium (International) on Combustion, Vol. 24, No. 1, 1992, pp. 1207-1215.
[12] J. G. Bailey, A. Tate, C. F. K. Diessel and T. F. Wall, “A Char Morphology System with Applications to Coal Combustion”, Fuel, Vol. 69, No. 2, 1990, pp. 225-239.
[13] R. B. Jones, C. B. McCourt, C. Morley and K. King, “Maceral and Rank Influences on the Morphology of Coal Char,” Fuel, Vol. 64, No. 10, 1985, pp. 1460-1467.
[14] R. S. Winburn, D. G. Grier, G. J. McCarthy and R. B. Peterson, “Rietveld Quantitative X-Ray Diffraction Analysis of NIST Fly Ash Standard Reference Materials,” Powder Diffraction, Vol. 15, No. 3, 2000, pp. 163-172.
[15] E. Raask, “Mineral Impurities in Coal Combustion: Behavior, Problems, and Remedial Measures,” Hemisphere Publishing Corporation, Washington, 1985, 484 p.
[16] C. R. Ward, “Analysis and Significance of Mineral Matter in Coal Seams,” International Journal of Coal Geology, Vol. 50, No. 1-4, 2002, pp. 135-168.
[17] V. Manovic, D. Loncarevic and R. Tokalic, “Particle-to-Particle Heterogeneous Nature of Coals: A Case of Large Coal Particles,” Energy Sources Part A—Recovery Utilization and Environmental Effects, Vol. 31, No. 5, 2009, pp. 427-437.
[18] D. X. Yu, et al., “Computer-Controlled Scanning Electron Microscopy (CCSEM) Investigation on the Heterogeneous Nature of Mineral Matter in Six Typical Chinese Coals,” Energy & Fuels, Vol. 21, No. 2, 2007, pp. 468-476.
[19] B. K. Saikia and Y. Ninomiya, “An Investigation on the Heterogeneous Nature of Mineral Matters in Assam (India) Coal by CCSEM Technique,” Fuel Processing Technology, Vol. 92, No. 5, 2011, pp. 1068-1077.
[20] P. N. Slater, G. H. Richards and J. N. Harb, “Pyrite and Illite Associations in 2 Eastern US Bituminous Coals,” Fuel Processing Technology, Vol. 44, No. 1-3, 1995, pp. 55-69.
[21] D. Brooker, “Chemistry of Deposit Formation in a Coal Gasification Syngas Cooler,” Fuel, Vol. 72, No. 5, 1993, pp. 665-670.
[22] R. W. Bryers, “Fireside Slagging, Fouling, and High-Temperature Corrosion of Heat-Transfer Surface Due to Impurities in Steam-Raising Fuels,” Progress in Energy and Combustion Science, Vol. 22, No. 1, 1996, pp. 29-120.
[23] G. Couch, “Understanding Slagging and Fouling in pf Combustion,” IEA Coal Research, Report No. IEACR/72, 1994.
[24] J. L. Yu, J. Lucas, V. Strezov and T. Wall, “Swelling and Char Structures from Density Fractions of Pulverized Coal,” Energy & Fuels, Vol. 17, No. 5, 2003, pp. 1160-1174.
[25] H. Wu, T. Wall, G. Liu and G. Bryant, “Ash Liberation from Included Minerals during Combustion of Pulverized Coal: The Relationship with Char Structure and Burnout,” Energy and Fuels, Vol. 13, No. 6, 1999, pp. 1197-1202.
[26] V. T. Sathyanathan and K. P. Mohammad, “Prediction of Unburnt Carbon in Tangentially Fired Boiler Using Indian Coals,” Fuel, Vol. 83, No. 16, 2004, pp. 2217-2227.
[27] J. R. Bunt and F. B. Waanders, “An Understanding of Lump Coal Physical Property Behaviour (Density and Particle Size Effects) Impacting on a Commercial-Scale Sasol-Lurgi FBDB Gasifier,” Fuel, Vol. 87, No. 13-14, 2008, pp. 2856-2865.
[28] R. P. Gupta, T. F. Wall, I. Kajigaya, S. Miyamae and Y. Tsumita, “Computer-Controlled Scanning Electron Microscopy of Minerals in Coal—Implications for Ash Deposition,” Progress in Energy and Combustion Science, Vol. 24, No. 6, 1998, pp. 523-543.
[29] M. Fajardo, J. Mojica, J. Barraza, G. A. P. Alcazar and J. A. Tabares, “Mineral Identification in Colombian Coals Using Mossbauer Spectroscopy and X-Ray Diffraction,” Hyperfine Interactions, Vol. 122, No. 1-2, 1999, pp. 129-138.
[30] K. M. Djamarani and I. M. Clark, “Characterization of Particle Size Based on Fine and Coarse Fractions,” Powder Technology, Vol. 93, No. 2, 1997, pp. 101-108.
[31] G. R. Dyrkacz, C. A. A. Bloomquist, L. Ruscic and E. P. Horwitz, “Variations in Properties of Coal Macerals Elucidated by Density Gradient Separation,” ACS Symposium Series, Vol. 252, 1984, pp. 65-77.
[32] G. H. Taylor, M. Teichmüller and C. Davis, “Organic Petrology: A New Handbook Incorporating Some Revised Parts of Stach’s Textbook of Coal Petrology,” Gebrüder Borntraeger, Berlin, 1998.
[33] B. Nandi, T. Brown and G. Lee, “Inert Coal Macerals in Combustion,” Fuel, Vol. 56, No. 2, 1977, pp. 125-130.
[34] I. S. Ruiz and C. R. Ward, “Chapter 4—Coal Combustion, in Applied Coal Petrology,” Elsevier, Burlington, 2008, pp. 85-117.
[35] S. F. Miller and H. H. Schobert, “Effect of Fuel Particle and Droplet Size Distribution on Particle-Size Distribution of Char and Ash during Pilot-Scale Combustion of Pulverized Coal and Coal-Water Slurry Fuels,” Energy & Fuels, Vol. 7, No. 4, 1993, pp. 520-531.
[36] J. N. Harb, “Investigation of Mineral Transformations and Ash Deposition during Staged Combustion,” Quarterly Technical Progress Report, 1 January 1996-31 March 1996.
[37] C. Sheng, C. D. Sheng, J. Lin, Y. Li and C. Wang, “Transformation Behaviors of Excluded Pyrite during O2/CO2 Combustion of Pulverized Coal,” Asia-Pacific Journal of Chemical Engineering, Vol. 5, No. 2, 2010, pp. 304-309.
[38] M. G. Thomas, T. D. Padrick, F. V. Stohl, F. V. Stephens and P. Howard, “Decomposition of Pyrite under Coal Liquefaction Conditions: A Kinetic Study,” Fuel, Vol. 61, No. 8, 1982, pp. 761-764.
[39] S. Srinivasachar, J. J. Helble and A. A. Boni, “Mineral Behavior during Coal Combustion.1. Pyrite Transformations,” Progress in Energy and Combustion Science, Vol. 16, No. 4, 1990, pp. 281-292.
[40] M. Loubser and S. Verryn, “Combining XRF and XRD Analyses and Sample Preparation to Solve Mineralogical Problems,” South African Journal of Geology, Vol. 111, No. 2-3, 2008, pp. 229-238.
[41] C. R. Ward and D. French, “Determination of Glass Content and Estimation of Glass Composition in Fly Ash Using Quantitative X-Ray Diffractometry,” Fuel, Vol. 85, No. 16, 2006, pp. 2268-2277.
[42] M. A. Wisdom, et al., “Quantitative XRD Analysis of Coal Combustion By-Products,” Abstracts of Papers of the American Chemical Society, Vol. 219, 2000, p. U399.
[43] Y. Hiei and H. Shirai, “Basic Study on Mineral Removal from Coal—The Influence of Mineral Distribution and Size of Pulverized Coal on Characteristics of Mineral Removal,” Coal Preparation, Vol. 26, No. 3, 2006, pp. 137-148.
[44] Y. H. Liu, R. Gupta and T. Wall, “Ash Formation from Excluded Minerals including Consideration of Mineral-Mineral Associations,” Energy & Fuels, Vol. 21, No. 2, 2007, pp. 461-467.

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