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Computational modeling of flow field in boiler before and after urea injection under different conditions

In order to achieve ultra-low NOx emissions, the effects of total excess air coefficient, air coefficient in main combustion zone, blended-coal combustion and ammonia nitrogen molar ratio on a 330 MW coal-fired boiler combustion were studied by numerical simulation. The results show that the velocity field and temperature field in the furnace have synergy, the better the synergy is, the faster the temperature rises, and the more NOx it generates. Compared before and after urea spraying, the NOx concentration decreased with the decrease of the total excess air coefficient, the optimum total excess air coefficient is about 1.15, and the denitrification rate is as high as 76.2%. The smaller the air coefficient in the main combustion zone is, the smaller the NOx concentration is. The optimum air coefficient in the main combustion zone is about 0.92, and the denitrification rate is 85%. After urea injection, the denitrification rate of high volatile coal combustion is higher than that of low volatile coal combustion, and the reasonable blending mode of coal can reduce NOx emissions. The larger the ammonia-nitrogen molar ratio is, the lower the NOx concentration is. When the ammonia-nitrogen molar ratio is greater than 2, the amount of ammonia escape at the flue outlet exceeds the standard. When the ammonia-nitrogen molar ratio is less than 1, the NOx concentration at the flue outlet is greater than that before urea injection. The optimal ammonia-nitrogen molar ratio is about 2.
PAPER REVISED: 2020-11-25
PAPER ACCEPTED: 2020-12-17
  1. Yue, T., et al., Emission characteristics of hazardous atmospheric pollutants from ultra-low emission coal-fired industrial boilers in China, Aerosol and Air Quality Research, 20 (2020), pp.877-888.
  2. Mladenovic, M., et al., Denitrification techniques for biomass combustion, Renewable and Sustainable Energy Reviews,82 (2018), pp.3350-3364.
  3. Yao, X., et al., Investigation and control technology on excessive ammonia-slipping in coal-fired plants, Energies,13 (2020), doi:10.3390/en13164249.
  4. Fan, W., et al., Experimental study on the impact of adding NH3 on NO production in coal combustion and the effects of char, coal ash, and additives on NH3 reducing NO under high temperature, Energy,173 (2019), pp.109-120.
  5. Masato, T., et al., Experimental investigation of ammonia combustion in a bench scale 1.2 MW thermal pulverised coal firing furnace, Applied Energy, 277(2020), pp.115580.
  6. Tsukada, N., et al., Role of OH radical in fuel-NOx formation during cocombustion of ammonia with hydrogen, methane, coal, and biomass, Energy & Fuels, 34(2020), pp.4777-4787.
  7. Liu, S., et al., Relationship between the N2O decomposition and NO formation in H2O/CO2 /NH3/NO atmosphere under the conditions of simulated air-staged combustion in the temperature interval of 900-1600 ℃, Energy, 211(2020), pp.118647.
  8. Carlo, L., et al., Selective non-catalytic reduction (SNCR) of nitrogen oxide emissions: a perspective from numerical modeling, Flow, Turbulence and Combustion, 100(2018), pp.301-340.
  9. Wang, W., et al., Numerical simulation of NOx emission characteristics during combustion in 350 MW supercritical cogeneration tangentially boiler, Thermal Science,24(2020),pp.2717-2728.
  10. Przemysław, G., et al., Numerical research on the SNCR method in a grate boiler equipped with the innovative FJBS system, Energy, 207(2020),
  11. Sakiko, I., et al., Numerical calculation with detailed chemistry on ammonia co-firing in a coal-fired boiler: effect of ammonia co-firing ratio on NO emissions, Fuel, 274 (2020), pp.116924.
  12. Norbert, M.,et al., Numerical simulation of SNCR (selective non-catalytic reduction) process in coal fired grate boiler, Energy, 92(2015), pp.67-76.
  13. Zhang, L., et al., Modeling De-NOx by injection ammonia in high temperature zone of cement precalciner, Journal of Thermal Science,2020,
  14. Guo, Z., et al., A novel concept for convective heat transfer enhancement, International Journal of Heat and Mass Transfer,41 (1998),14, pp.2221-2225.
  15. Zeng, Z., et al., Investigation of the flow and heat transfer characteristics in advanced vortex combustor, International Journal of Thermal Sciences, 156 (2020), pp.106459.
  16. Fu, Z., et al., Generation characteristics of thermal NOx in a double-swirler annular combustor under various inlet conditions, Energy,200(2020), pp.117487.
  17. Li, Y., et al., Thermal and hydraulic characteristics of microchannel heat sinks with cavities and fins based on field synergy and thermodynamic analysis, Applied Thermal Engineering, 175 (2020), pp.115345.
  18. Tomáš B., et al., High temperature modification of SNCR technology and its impact on NOx removal process. European Physical Journal Conferences, 180 (2018), pp.02009.
  19. Wu, Y., et al., Effects of turbulent mixing and controlling mechanisms in an entrained flow coal gasifier, Energy & Fuels, 24 (2010), pp.1170-1175.
  20. Nakod, P., CFD Modeling and validation of oxy-fired and air fired entrained flow gasifiers, International Journal of Chemical & Physical Science, 02 (2013), pp.28-40.
  21. Ma, L., et al., A novel corner-fired boiler system of improved efficiency and coal flexibility and reduced NO x emissions, Applied Energy, 238(2019), pp.453-465.
  22. Li, Z., et al., Effects of moisture and its input form on coal combustion process and NOx transformation characteristics in lignite boiler, Fuel, 266(2020), pp.116970.
  23. Wang,Y., et al., Numerical optimization of the influence of multiple deep air-staged combustion on the NOx emission in an opposed firing utility boiler using lean coal, Fuel, 269(2020), pp.116996.
  24. Li, Yu., et al., Effect of char gasification on NOx formation process in the deep air-staged combustion in a 20 KW down flame furnace, Applied Energy, 164(2016), pp.258-267.
  25. Naruse, I., et al., Fundamental study on N2O formation/decomposition characteristics by means of low-temperature pulverized coal combustion. Symposium (International) on Combustion, 26(1996), pp. 3213-3221.
  26. Franz, W., et al., The NO and N2O formation mechanism during devolatilization and char combustion under fluidized-bed conditions, Symposium (international) on combustion, 26(1996), pp. 3325-3234.
  27. Lockwood, F., et al., Mathematical modelling of fuel-NO emissions from PF burners, Journal of the Institute of Energy, 65(1992), pp.144-152.
  28. Yan, Z., et al., Numerical simulation of synergistic optimization of un-burned carbon and NOx of blended coal under deep air staging condition, Clean Coal Technology, 25 (2019), pp. 82-87.
  29. Wang, D., et al., A review of urea pyrolysis to produce NH3 used for NOx removal, Journal of Chemistry, 2019(2019), pp. 01-11.
  30. Ma, L., et al., Combustion interactions of blended coals in an O2/CO2 mixture in a drop-tube furnace: experimental investigation and numerical simulation, Applied Thermal Engineering, 145 (2018), pp.184-200.