THERMAL SCIENCE

International Scientific Journal

Thermal Science - Online First

Yazhu Zhang

,

Congxi Liu

,

Zhuben Huang

,

Jun Huang

,

Zhang Li

,

Kai Li

online first only

A simulation study on effect of nozzle geometry on flameless combustion of non-preheated methane gas

ABSTRACT
In this paper, the effects of different burner configurations on the characteristics of flameless combustion were evaluated by comparing the temperature field, NOx, OH and H2CO at different burner inlet velocity and angles through a combination of experimental and numerical simulations. The results show that increasing the burner inlet angle and gas velocity is imperative in achieving the flameless combustion, increasing the recirculation rate in the furnace, making the temperature distribution in the furnace uniform, and reducing the emission of NOx at the end of the furnace. During the simulation of flameless combustion, it was found that OH radicals and H2CO radicals were well correlated with the reaction exothermic zone, and the Reynolds number was positively correlated with the recirculation rate in the furnace. With the increase of Reynolds number, the entrainment rate of flue gas increases, and the combustion state is closer to flameless combustion. When recirculation rate Kv >2, combustion becomes flameless. Through the summary analysis of the data, it can be found that there is a critical Reynolds number for the burner to achieve flameless combustion, and flameless combustion occurs only when the Reynolds number is greater than 1.0×104.
KEYWORDS
flameless combustion, Methane combustion, numerical simulation, NOx emission, temperature distribution
PAPER SUBMITTED: 2023-10-14
PAPER REVISED: 2024-01-31
PAPER ACCEPTED: 2024-02-12
PUBLISHED ONLINE: 2024-04-13
DOI REFERENCE: https://doi.org/10.2298/TSCI231014077Z
REFERENCES
  1. Li P., et al., Experimental and Numerical Study of the Fuel-NOx Formation at High CO2 Concentrations in a Jet-Stirred Reactor, Energy and Fuels, 33 (2019), 7, pp. 6797-6808
  2. Slefarski, R., et al., Experimental study on combustion of CH4/NH3 fuel blends in an industrial furnace operated in flameless conditions, Thermal Science, 24 (2020). 2, pp. 3625-3635
  3. Pramanik S.,Ravikrishna RV., Effect of N2 dilution and preheat temperature on combustion dynamics of syngas in a reverse-flow combustor, Experimental Thermal and Fluid Science, 110 (2020)
  4. Darvell., et al. Some Aspects of Modeling NOx Formation Arising from the Combustion of 100% Wood in a Pulverized Fuel Furnace, Combustion Science and Technology, 186 (2014), 4-5, pp. 672-683
  5. Shan, Shiquan., et al., A review on fundmental research of oxy-coal combustion technology, Thermal Science, 26 (2022), 2, pp. 1945-1958
  6. Fan, WD., et al., Coal-nitrogen release and NOx evolution in the oxidant staged combustion of coal, Energy, 125 (2017), pp. 417-426
  7. Tu Y,Zhou., et al., NOx reduction in a 40 t/h biomass fired grate boiler using internal flue gas recirculation technology, Applied Energy, 220 (2018), pp. 962-973
  8. Christos A T., Emissions and Power Losses due to Biofuel or Biomass Nitrogen: Assessment and Prevention Mechanisms, Energy Fuels, 30 (2016), 11, pp. 9396-9408
  9. Cai, X., et al., New weighted-sum-of-gray-gases radiation model for oxy-fuel combustion simulation of semi-coke from coal-based poly-generation, Thermal Science and Engineering Progress, 46(2023)
  10. Wünning J.A., Wünning J.G.; Flameless oxidation to reduce thermal no-formation, Progress in Energy and Combustion Science, 23 (1997), 1, pp. 81-94
  11. Jianwei Y, Ichiro N 1999, Effects of Air Dilution on Highly Preheated Air Combustion in a Re-generative Furnace, Energy and Fuels, 13, pp. 99-104.
  12. G.G. Szegö., et al.,Operational characteristics of a parallel jet MILD combustion burner system, Combustion and Flame, 156 (2008), 2, pp. 429-438
  13. Masashi K., Toshiaki H., The science and technology of combustion in highly preheated air, Symposium (International) on Combustion, 27 (1998), 2, pp. 3135-3146
  14. Kazuhiro K., et al., High temperature air combustion boiler for low BTU gas, Energy Conversion and Management, 43(2002), 9-12, pp. 1563-1570.
  15. Liu W., et al., Effects of the tertiary air injection port on semi-coke flameless combustion with coal self-preheating technology, Fuel, 271 (2020)
  16. Masashi K., Toshiaki H., The science and technology of combustion in highly preheated air, Symposium (International) Combustion, 27 (1998), 2, pp. 3135-3146
  17. Dally B.B., et al., Structure of turbulent non-premixed jet flames in a diluted hot coflow, Proceedings of Combustion Institute, 29 (2002), 1, pp. 1147-1154
  18. F.C. Christo.,B.B. Dally., Modeling turbulent reacting jets issuing into a hot and diluted coflow. Combustion and Flame, 142 (2005), 1-2, pp. 117-129
  19. Seung H K., et al., Conditional moment closure modeling of turbulent nonpremixed combustion in diluted hot coflow, Proceedings of the Combustion Institute, 30 (2005), 1, pp. 751-757
  20. Dally B.,et al., Effect of fuel mixture on moderate and intense low oxygen dilution combustion, Combustion and Flame, 137 (2004), 4, pp. 418-431
  21. Roman W., et al., On the (MILD) combustion of gaseous, liquid, and solid fuels in high temperature preheated air, Proceedings of the Combustion Institute, 30 (2005), 2, pp. 2623-2629
  22. Veríssimo A.S., et al., Experimental study on the influence of the thermal input on the reaction zone under flameless oxidation conditions, Fuel Processing Technology, 106 (2013), pp. 423-428
  23. Huang MM., et al., Effect of thermal input, excess air coefficient and combustion mode on natural gas MILD combustion in industrial-scale furnace, Fuel, 302 (2021)
  24. Dally B.B., et al., Structure of turbulent non-premixed jet flames in a diluted hot coflow, Proceedings of the Combustion Institute, 29 (2002), 1, pp. 1147-1154
  25. Oldenhof E., et al., Ignition kernel formation and lift-off behaviour of jet-in-hot-coflow flames, Combustion and Flame, 157 (2010), 6, pp. 1167-1178
  26. Veríssimo A. S., et al., Operational, Combustion, and Emission Characteristics of a Small-Scale Combustor, Energy Fuels, 25 (2011), 6, pp. 2469-2480
  27. Von Schéele, J., et al., Flameless oxyfuel combustion for increased production and reduced CO2 and NOx emissions, stahl und eisen, 128 (2008), 7, pp. 35-42
  28. Szewczyk, D., et al., Experimental study of the combustion process of gaseous fuels containing nitrogen compounds with the use of new, low-emission Zonal Volumetric Combustion technology, Energy, 92 (2015), pp. 3-12
  29. Mardani A, et al., Numerical study of oxy-fuel MILD (moderate or intense low-oxygen dilution combustion) combustion for CH4-H2 fuel, Energy, 99 (2016), pp. 136 -151
  30. Dostiyarov, A., et al., A novel vortex combustion device: Experiments and numerical simulations with emphasis on the combustion process and NOx emissions, Thermal Science, 26 (2022), 2, pp.1971-1983
PDF VERSION [DOWNLOAD]
A simulation study on effect of nozzle geometry on flameless combustion of non-preheated methane gas