AN INTEGRATED MODEL TO STUDY THE EFFECTS OF OPERATIONAL PARAMETERS ON THE PERFORMANCE AND POLLUTANT EMISSIONS IN A UTILITY BOILER

Abstract

A gas fired tangentially boiler was modeled under full load conditions. Furnace was simulated by CFD and then was joint with two mathematical models to calculate heat transfer in the convective section, and metal temperature of waterwall tubes. Effects of changing the combustion excess air (0 to 20%) and burners tilt angle (-30° to +30°) were studied. Results showed that the boiler efficiency is optimum if excess air= 10% and the burners have a negative angle. However, these optimum settings cannot produce a superheated and reheated steam of 538 °C which is desirable. Indeed, a zero or positive tilt angle with 10% excess air, or a negative burner angle with 15% excess air lead to highest efficiency by considering the potential of generating superheated steam of 538 °C. In addition, CO emission in low excess air values growths by increasing the burner tilt angle. NOx emission in low and high excess air ratios is lower at positive burner angles while a moderate excess air (10%) needs a zero tilt angle to minimize NOx emission. Furthermore, a critical fouling thickness was computed, considering boiler's circulation ratio, in which the metal temperature of the waterwall exceeds the short overheating threshold. With a certain thickness of scale layers inside the tubes, a burner tilting equal to 0° or 30° postpones tube rupture. These results could be utilized by operating engineers to keep their utility boilers in the most efficient state and avoiding overheating and tube rupture.

Keywords

• Non-Premixed Combustion
• Burner
• Excess Air
• Deposition
• Thermal Efficiency
• NOx and CO Emission

References

1. [1] Hasini H, Yusoff MZ, Shuaib NH, Boosroh MH, Haniff MA. Analysis of flow and temperature distribution in a full scale utility boiler using CFD. In 2009 3rd International Conference on Energy and Environment (ICEE) 2009 Dec 7 (pp. 208-214). IEEE, http://dx.doi.org/10.1109/ICEENVIRON.2009.5398646.
2. [2] Park JK, Park S, Ryu C, Baek SH, Kim YJ, Park HY. CFD analysis on bioliquid co-firing with heavy fuel oil in a 400 MWe power plant with a wall-firing boiler. Applied Thermal Engineering. 2017;124:1247-56, http://dx.doi.org/10.1016/j.applthermaleng.2017.06.104.
3. [3] Galindo-Garci´a IF, Va´zquez Barraga´n AK, Rossano Roma´n M. Numerical study of the flow and temperature distributions in a 350 mw utility boiler. In ASME Power Conference 2010. (49354) p. 767-775.
4. [4] Masoumi H, Abroshan H. Numerical investigation of burner angles effect on the combustion phenomenon in a selected power plant boiler. Fuel and Combustion Journal. 2012; 1:1-13.
5. [5] Du Y, Lv Q, Li D, Liu H, Che D. CFD investigation on combustion and NOx emission characteristics in a 600 MW wall-fired boiler under high temperature and strong reducing atmosphere. Applied Thermal Engineering. 2017; 126:407-18.
6. [6] Arablu M, Poursaeidi E. Using CFD for NO x emission simulation in a dual fuel boiler. Combustion, Explosion, and Shock Waves. 2011;47(4):426.
7. [7] Hochenauer C, Brandstetter G. CFD simulation of a low NOx oil fired boiler. In Turbo Expo: Power for Land, Sea, and Air 2005;4725:1-10.
8. [8] Yue-yun S, Xiao-tao G, Ming-yao Z. Numerical study on the impact of varying operation conditions on nox emissions of large-scale pulverized coal-fired utility boiler. In International Symposium on Coal Combustion Berlin, Heidelberg, Germany. Springer; 2011. p. 1141-1152.

9. [9] Luan S, Ma Z, Wang H, Zhang Y, Lu P. CFD modeling and field testing of a 600-MW wall-fired boiler burning low-volatile bituminous coal. International Symposium on Coal Combustion, Singapore. Springer; 2015. p.213-219.
10. [10] Gao H, Runstedtler A, Majeski A, Boisvert P, Campbell D. Optimizing a woodchip and coal co-firing retrofit for a power utility boiler using CFD. Biomass and Bioenergy. 2016; 88:35-42.
11. [11] Rahimi M, Khoshhal A, Shariati SM. CFD modeling of a boiler’s tubes rupture. Applied Thermal Engineering. 2006;26(17-18):2192-2200.
12. [12] Tang G, Wu B, Johnson K, Kirk A, Zhou CQ. Simulation of an industrial tangentially fired boiler firing metallurgical gases. Journal of Thermal Science and Engineering Applications [Internet]. 2014;7(1): (011003) 1-11. Available from: https://doi.org/10.1115/1.4028344.
13. [13] Purimetla A, Cui J. CFD studies on burner secondary airflow. Applied Mathematical Modelling. 2009;33(2):1126-40.
14. [14] Vuthaluru HB, Vuthaluru R. Control of ash related problems in a large scale tangentially fired boiler using CFD modelling. Applied Energy. 2010;87(4):1418-26.
15. [15] Schuhbauer C, Angerer M, Spliethoff H, Kluger F, Tschaffon H. Coupled simulation of a tangentially hard coal fired 700° C boiler. Fuel. 2014;122:149-63, http://dx.doi.org/10.1016/j.fuel.2014.01.032.
16. [16] Drosatos P, Nikolopoulos N, Agraniotis M, Itskos G, Grammelis P, Kakaras E. Decoupled CFD simulation of furnace and heat exchangers in a lignite utility boiler. Fuel. 2014;117:633-48, http://dx.doi.org/10.1016/j.fuel.2013.09.033.
17. [17] Bar-Ziv E, Berman Y, Saveliev R, Perelman M, Korytnyi E, Davidson B, Chudnovsky B. Fouling formation in 575 mv tangential-fired pulverized-coal boiler. Journal of Engineering for Gas Turbines and Power [Internet]. 2010;132(12) :(123001) 1-7. Available from: https://doi.org/10.1115/1.4001297.
18. [18] Taha TJ, Stam AF, Stam K, Brem G. CFD modeling of ash deposition for co-combustion of MBM with coal in a tangentially fired utility boiler. Fuel Processing Technology. 2013; 114:126-34.
19. [19] Cantrell C, Idem S. On-line performance model of the convection passes of a pulverized coal boiler. Heat Transfer Engineering. 2010;31(14):1173-83.
20. [20] Bhambare KS, Mitra SK, Gaitonde UN. Modeling of a coal-fired natural circulation boiler. Journal of Energy Resources Technology. 2007;129(2):159-167.
21. [21] Sreepradha C, Panda RC, Bhuvaneswari NS. Mathematical model for integrated coal fired thermal boiler using physical laws. Energy. 2017; 118:985-98.
22. [22] Chaibakhsh A, Ghaffari A, Moosavian SA. A simulated model for a once-through boiler by parameter adjustment based on genetic algorithms. Simulation Modelling Practice and Theory. 2007;15(9):1029-51, http://dx.doi.org/10.1016/j.simpat.2007.06.004.
23. [23] Zhang W, Wang H, Yan K, Zhou T, Wang CA, Chen K, Che D. Mathematical modeling and thermal–hydrodynamic analysis of vertical water wall in a SCFB boiler with annular furnace. Applied Thermal Engineering. 2016; 102:742-8.
24. [24] Zima W, Nowak-Ocłoń M, Ocłoń P. Simulation of fluid heating in combustion chamber waterwalls of boilers for supercritical steam parameters. Energy. 2015; 92:117-27.
25. [25] Kim S, Choi S. Dynamic simulation of the water-steam flow in a supercritical once-through boiler. Journal of Mechanical Science and Technology. 2017;31(10):4965-75, http://dx.doi.org/10.1007/s12206-017-0945-z.
26. [26] Zima W. Mathematical Modelling of Dynamics of Boiler Surfaces Heated Convectively. In: Vikhrenko VS. (ed.). Heat Transfer-Engineering Applications [Internet]. Rijeka: IntechOpen; 2011. Available from: https://doi.org/10.5772/26231, p. 259-282.
27. [27] Singer JG. Combustion - Fossil Power Systems - a Reference Book on Fuel Burning and Steam Generation, Combustion Engineering. Inc., Windsor, CT; 1981.
28. [28] Munisamy KM, Yusoff MZ, Thangaraju SK, Hassan H, Ahmad A. Burner tilting angle effect on velocity profile in 700 MW Utility Boiler. IOP Conference Series: Materials Science and Engineering. 2015 Sep; 88:012021.
29. [29] Kumar M, Sahu SG. Study on the effect of the operating condition on a pulverized coal-fired furnace using computational fluid dynamics commercial code. Energy & Fuels. 2007;21(6):3189-93.
30. [30] Tree DR, Webb BW. Local temperature measurements in a full-scale utility boiler with overfire air. Fuel. 1997;76(11):1057-66.
31. [31] Hill SC, Smoot LD. Modeling of nitrogen oxides formation and destruction in combustion systems. Progress in Energy and Combustion Science. 2000;26(4-6):417-58.
32. [32] Hao Z, Kefa C, Ping S. Prediction of ash deposition in ash hopper when tilting burners are used. Fuel Processing Technology. 2002;79(2):181-95.
33. [33] Dal Secco S, Juan O, Louis-Louisy M, Lucas JY, Plion P, Porcheron L. Using a genetic algorithm and CFD to identify low NOx configurations in an industrial boiler. Fuel. 2015; 158:672-83.
34. [34] Tian D, Zhong L, Tan P, Ma L, Fang Q, Zhang C, Zhang D, Chen G. Influence of vertical burner tilt angle on the gas temperature deviation in a 700 MW low NOx tangentially fired pulverised-coal boiler. Fuel Processing Technology. 2015; 138:616-28.
35. [35] Tan P, Tian D, Fang Q, Ma L, Zhang C, Chen G, Zhong L, Zhang H. Effects of burner tilt angle on the combustion and NOx emission characteristics of a 700 MWe deep-air-staged tangentially pulverized-coal-fired boiler. Fuel. 2017;196:314-24, http://dx.doi.org/10.1016/j.fuel.2017.02.009.
36. [36] Więckowski Ł, Krawczyk P, Badyda K. Numerical investigation of temperature distribution in the furnace of a coal fired grate boiler in part load conditions. Journal of Power Technologies. 2018;97(5):359-65.
37. [37] Al-Mawali J, Dakka SM. Numerical analysis of flame characteristics and stability for conical nozzle burner. Journal of Thermal Engineering. 2019;5(5): 422-445, http://dx.doi.org/10.18186/thermal.624070.
38. [38] Marias F, Puiggali JR, Quintard M, Pit F. Quality of CFD models for jet flow analysis for the design of burners and boilers. Korean Journal of Chemical Engineering. 2002;19(1):28, http://dx.doi.org/10.1007/BF02706871
39. [39] Holman JP. Heat Transfer, Eighth SI Metric Edition. Mc Gran–Hill Book Company. 2001.
40. [40] Kays WM, Lo RK. Basic heat transfer and flow friction design data for gas flow to banks of staggered tubes: use of a transient technique. Technical Report 15. Stanford University.; 1952 Aug 15.
41. [41] Petukhov BS. Heat transfer and friction in turbulent pipe flow with variable physical properties. Advances in Heat Transfer. 1970; 6:503-564.
42. [42] Cooke DH. On prediction of off-design multistage turbine pressures by stodola’s ellipse. Journal of Engineering for Gas Turbines and Power. 1985;107(3):596-606, http://dx.doi.org/10.1115/1.3239778
43. [43] Collier JG, Thome JR. Convective Boiling and Condensation. Clarendon Press; 1994.
44. [44] Bergles AE, Rohsenow WM. The determination of forced-convection surface-boiling heat transfer. Journal of Heat Transfer. 1964;86(3): 365-372.
45. [45] Petelin, S, Koncar, B. Prediction of void fraction in subcooled flow boiling. International Conference in Nuclear Energy in Central Europe, Slovenia. 1998:195-222.
46. [46] Gungor KE, Winterton RH. A general correlation for flow boiling in tubes and annuli. International Journal of Heat and Mass Transfer. 1986;29(3):351-8, http://dx.doi.org/10.1016/0017-9310(86)90205-X.
47. [47] Chen JC. Correlation for boiling heat transfer to saturated fluids in convective flow. Industrial & Engineering Chemistry Process Design and Development. 1966;5(3):322-9.
48. [48] Cooper MG. Saturation nucleate pool boiling - a simple correlation. First UK National Conference on Heat Transfer [Internet]. Elsevier; 1984. p. 785–93. Available from: http://dx.doi.org/10.1016/B978-0-85295-175-0.50013-8.
49. [49] Jiao B, Qiu LM, Lu JL, Gan ZH. Liquid film dryout model for predicting critical heat flux in annular two-phase flow. Journal of Zhejiang University-Science A. 2009;10(3):398-417, http://dx.doi.org/10.1631/jzus.A0820322.
50. [50] Port RD, Herro HM. The Nalco Guide to Boiler Failure Analysis: The Nalco Chemical. McGraw-Hill; 1991.