THERMAL SCIENCE

International Scientific Journal

MODELING AND OPTIMIZATION OF PROCESSES FOR CLEAN AND EFFICIENT PULVERIZED COAL COMBUSTION IN UTILITY BOILERS

ABSTRACT
Pulverized coal-fired power plants should provide higher efficiency of energy conversion, flexibility in terms of boiler loads and fuel characteristics and emission reduction of pollutants like nitrogen oxides. Modification of combustion process is a cost-effective technology for NOx control. For optimization of complex processes, such as turbulent reactive flow in coal-fired furnaces, mathematical modeling is regularly used. The NOx emission reduction by combustion modifications in the 350 MWe Kostolac B boiler furnace, tangentially fired by pulverized Serbian lignite, is investigated in the paper. Numerical experiments were done by an in-house developed three-dimensional differential comprehensive combustion code, with fuel- and thermal-NO formation/destruction reactions model. The code was developed to be easily used by engineering staff for process analysis in boiler units. A broad range of operating conditions was examined, such as fuel and preheated air distribution over the burners and tiers, operation mode of the burners, grinding fineness and quality of coal, boiler loads, cold air ingress, recirculation of flue gases, water-walls ash deposition and combined effect of different parameters. The predictions show that the NOx emission reduction of up to 30% can be achieved by a proper combustion organization in the case-study furnace, with the flame position control. Impact of combustion modifications on the boiler operation was evaluated by the boiler thermal calculations suggesting that the facility was to be controlled within narrow limits of operation parameters. Such a complex approach to pollutants control enables evaluating alternative solutions to achieve efficient and low emission operation of utility boiler units. [Projekat Ministarstva nauke Republike Srbije, br. TR-33018: Increase in energy and ecology efficiency of processes in pulverized coal-fired furnace and optimization of utility steam boiler air preheater by using in-house developed software tools]
KEYWORDS
PAPER SUBMITTED: 2015-06-04
PAPER REVISED: 2015-12-10
PAPER ACCEPTED: 2015-12-21
PUBLISHED ONLINE: 2016-01-01
DOI REFERENCE: https://doi.org/10.2298/TSCI150604223B
CITATION EXPORT: view in browser or download as text file
THERMAL SCIENCE YEAR 2016, VOLUME 20, ISSUE Supplement 1, PAGES [S183 - S196]
REFERENCES
  1. Zhang, X., et al., Numerical Investigation of Low NOx Combustion Strategies in Tangentially Fired Coal Boilers, Fuel, 142 (2015), pp. 215-221
  2. Chui, E. H., Gao, H., Estimation of NOx Emissions from Coal-Fired Utility Boilers, Fuel, 89 (2010), 10, pp. 2977-2984
  3. Liu, H., et al., Effect of Two-Level Over-Fire Air on the Combustion and NOx Emission Characteristics in a 600 MW Wall-Fired Boiler, Numerical Heat Transfer. Part A: Applications, 68 (2015), 9, pp. 993-1009
  4. Zhou, H., et al., Numerical Simulation of the Combustion Characteristics of a Low NOx Swirl Burner: Influence of the Primary Air Pipe, Fuel, 130 (2014), pp. 168-176
  5. Fan, J., et al., Modeling of Combustion Process in 600 MW Utility Boiler using Comprehensive Models and its Experimental Validation, Energy & Fuels, 13 (1999), 5, pp. 1051-1057
  6. Zeng, L., et al., Numerical Simulation of Combustion Characteristics and NOx Emissions in a 300 MWe Utility Boiler with Different Outer Secondary-Air Vane Angles, Energy & Fuels, 24 (2010), 10, pp. 5349-5358
  7. Chen, Zh., et al., Gas/Particle Flow and Combustion Characteristics and NOx Emissions of a New Swirl Coal Burner, Energy, 36 (2011), 2, pp. 709-723
  8. Modlinski, N., Computational Modeling of a Utility Boiler Tangentially-Fired Furnace Retrofitted with Swirl Burners, Fuel Processing Technology, 91 (2010), 11, pp. 1601-1608
  9. Coelho, L. M. R., et al., Application of a Global NOx Formation Model to a Pulverized Coal Fired Boiler with Gas Reburning, Proceedings, 4th International Conference on Technologies and Combustion for a Clean Environment, Lisbon, Portugal, July 7-10, 1997, Paper 9.4, pp. 1/8-8/8
  10. Xu, M., Azevedo, J. L. T., Carvalho, M. G., Modelling of the Combustion Process and NOx Emission in a Utility Boiler, Fuel, 79 (2000), 13, pp. 1611-1619
  11. Khalilarya, Sh., Lotfiani, A., Determination of Flow Pattern and its Effect on NOx Emission in a Tangentially Fired Single Chamber Square Furnace, Thermal Science, 14 (2010), 2, pp. 493-503
  12. Diez, L. I., et al., Numerical Investigation of NOx Emissions from a Tangentially-Fired Utility Boiler under Conventional and Overfire Air Operation, Fuel, 87 (2008), 7, pp. 1259-1269
  13. Belosevic, S., et al., Numerical Study of a Utility Boiler Tangentially-Fired Furnace under Different Operating Conditions, Fuel, 87 (2008), 15-16, pp. 3331-3338
  14. Belosevic, S., et al., Numerical Prediction of Pulverized Coal Flame in Utility Boiler Furnaces, Energy & Fuels, 23 (2009), 11, pp. 5401-5412
  15. Belosevic, S., et al., Numerical Analysis of NOx Control by Combustion Modifications in Pulverized Coal Utility Boiler, Energy & Fuels, 26 (2012), 1, pp. 425-442
  16. Belošević, S., et al., Three-Dimensional Modeling of Utility Boiler Pulverized Coal Tangentially Fired Furnace, International Journal of Heat and Mass Transfer, 49 (2006), 19-20, pp. 3371-3378
  17. Hashimoto, N., et al., Numerical Analysis of Pulverized Coal Combustion in a Multiburner Furnace, Energy & Fuels, 21 (2007), 4, pp. 1950-1958
  18. Lockwood, F. C., Romo-Millares, C. A., Mathematical Modeling of Fuel NO Emissions From PF Burners, Journal of the Institute of Energy, 65 (1992), pp. 144-152
  19. Hill, S. C., Smoot, L. D., Modeling of Nitrogen Oxides Formation and Destruction in Combustion Systems, Progress in Energy and Combustion Science, 26 (2000), 4-6, pp. 417-458
  20. Smoot, L. D., Smith, P. J., Coal Combustion and Gasification, Plenum Press, New York, 1985
  21. McAdams, J. D., Minimize NOx Emissions Cost-Effectively, Hydrocarbon Processing, 80 (2001), 6, pp. 51-58
  22. Blokh, A. G., Thermal Radiation of a Pulverized-Coal Flame, in: Heat Transfer in Steam Boiler Furnaces, Hemisphere Publishing, New York, 1988, pp. 85-124
  23. Crnomarković, N., et al., Numerical Determination of the Impact of the Ash Deposit on the Furnace Walls to the Radiative Heat Exchange Inside the Pulverized Coal Fired Furnace, Proceedings, International Conference Power Plants 2014, Zlatibor, Serbia, 28-31. October 2014, ISBN 978-86-7877-024-1, pp. 679-690
  24. Belošević, S., et al., A Numerical Study of Pulverized Coal Ignition by means of Plasma Torches in Air-Coal Dust Mixture Ducts of Utility Boiler Furnaces, International Journal of Heat and Mass Transfer, 51 (2008), 7-8, pp. 1978-1978
  25. Solomon, P. R., Colket, M. B., Evolution of Fuel Nitrogen in Coal Devolatilisation, Fuel, 57 (1978), 12, pp. 749-755
  26. De Soete, G. G., Overall Reaction Rates of NO and N2 Formation from Fuel Nitrogen, Proceedings of the Combustion Institute, 15 (1975), 1, pp. 1093-1102
  27. De Soete, G. G., Heterogeneous N2O and NO Formation from Bound Nitrogen Atoms during Coal Char Combustion, Proceedings of the Combustion Institute, 23 (1991), 1, pp. 1257-1264
  28. Stojiljković, D., Nitrogen Oxides During Combustion of Domestic Lignites, Andrejević Foundation, Belgrade, 2001 (in Serbian)
  29. Li, S., et al., NOx Emission and Thermal Efficiency of a 300 MWe Utility Boiler Retrofitted by Air Staging, Applied Energy, 86 (2009), 9, pp. 1797-1803

© 2024 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, National Institute of the Republic of Serbia, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence