Numerical simulation of combustion characteristics at different coal concentrations in bituminous coal ignition in a tiny-oil ignition burner

Abstract

With the objective of producing a full-scale tiny-oil ignition burner, identical to the burner used in an 800 MWe utility boiler, numerical simulations were performed using Fluent 6.3.26 to study the progress of ignition for four coal concentration settings covering sub-operation conditions prevailing during the experiments performed with the burner. The numerical simulations conformed to the experimental results, demonstrating the suitability of the model used in the calculations. Simulations for a coal concentration of 0.40 kg/kg corresponding to a single burner operating at its rated output were also conducted, which indicated that gas temperatures along the burner centerline were high. As gas flowed to the burner nozzle, the high-temperature region expanded, ensuring a successful pulverized-coal ignition. With increasing coal concentration (0.08–0.40 kg/kg), the gas temperature along the burner centerline and at the first and second combustion chamber exits decreased at the equivalent radial points. At the center of the second combustion chamber exit, the O₂ concentrations were almost depleted for the five coal concentrations, while the CO concentrations peaked.

Key words： numerical simulation; tiny-oil ignition burner; pulverized coal; temperature field

Acknowledgments

This work was supported by the Hi-Tech Research and Development Program of China (No. 2007AA05Z301), the Post-doctoral Foundation of Heilongjiang Province (No. LRB07-216), and Heilongjiang Province via the 2005 Key Projects (No. GC05A314).

References

1 Dai D, Liu J. Tackling global electricity shortage through human power: Technical opportunities from direct or indirect utilizations of the pervasive and green human energy. Frontiers in Energy, 2012, 6(3): 210–226

2 Chen G F, Zheng X J, Cong L. Energy efficiency and carbon dioxide emissions reduction opportunities in district heating source in Tianjin. Frontiers in Energy, 2012, 6(3): 285–295

3 Franco A, Diaz A R. The future challenges for ‘‘clean coal technologies’’: Joining efficiency increase and pollutant emission control. Energy, 2009, 34(3): 348–354

4 You C F, Xu X C. Coal combustion and its pollution control in China. Energy, 2010, 35(11): 4467–4472

5 Liszka M, Ziebik A. Coal-fired oxy-fuel power unit- Process and system analysis. Energy, 2010, 35(2): 943–951

6 Schaffel-Mancini N, Mancini M, Szlek A, Weber R. Novel conceptual design of a supercritical pulverized coal boiler utilizing high temperature air combustion (HTAC) technology. Energy, 2010, 35(7): 2752–2760

7 Fan W D, Li Y Y, Lin Z C, Zhang M C. PDA research on a novel pulverized coal combustion technology for a large utility boiler. Energy, 2010, 35(5): 2141–2148

8 Liu C L, Li Z Q, Zhao Y, Chen Z C. Influence of coal-feed rates on bituminous coal ignition in a full-scale tiny-oil ignition burner. Fuel, 2010, 89(7): 1690–1694

9 Li Z Q, Liu C L, Zhao Y, Chen Z C. Influence of the coal-feed rate on lean coal ignition in a full-scale tiny-oil ignition burner. Energy & Fuels, 2010, 24(1): 375–378

10 Sheng C, Moghtaderi B, Gupta R, Wall T F. A computational fluid dynamics based study of the combustion characteristic of coal blends in pulverized coal-fired furnace. Fuel, 2004, 83(11,12): 1543-1552

11 Backreedy R I, Jones J M, Ma L, Pourkashanian M, Williams A, Arenillas A, Arias B, Pis J J, Rubiera F. Prediction of unburned carbon and NO_x in a tangentially fired power station using single coals and blends. Fuel, 2005, 84(17): 2196–2203

12 Saario A, Oksanen A. Comparison of global ammonia chemistry mechanisms in biomass combustion and selective noncatalytic reduction process conditions. Energy & Fuels, 2008, 22(1): 297–305

13 Yin C, Rosendahl L, Kær S, Clausen S, Hvid S L, Hille T. Mathematical modeling and experimental study of biomass combustion in a thermal 108 MW grate-fired boiler. Energy & Fuels, 2008, 22(2): 1380–1390

14 Shih T H, Liou W W, Shabbir A, Shabbir A, Yang Z G, Zhu J. A new k-ϵ eddy viscosity model for high reynolds number turbulent flows-model development and validation. Computers & Fluids, 1995, 24(3): 227–238

15 Gosman A D, Loannides E. Aspects of computer simulation of liquid-fuelled combustors. In: AIAA 19th Aerospace Science Meeting, St Louis, USA, 1981, Paper No. AIAA-81-0323

16 Cheng P. Two-dimensional radiation gas flow by a moment method. AIAA Journal, 1964, 2(9): 1662–1664

17 Smoot L D, Smith P J. Coal Combustion and Gasification. New York: Plenum Press, 1985

18 Spalding D B. Combustion and Mass Transfer. New York: Pergamon Press, 1979

19 Zhou L X. Theory and Numerical Modeling of Turbulent Gas-Particle Flows and Combustion. Boca Raton: CRC Press, 1993