OFA형 보일러의 운전조건이 NOx 발생에 미치는 영향

박경우; Kyoungwoo Park

Applied Chemistry for Engineering, Vol.24, No.3, 253-259, June, 2013

Export Citation

OFA형 보일러의 운전조건이 NOx 발생에 미치는 영향

Effects of Operating Conditions on NOx Emission in OFA-type Boiler

박경우^†

호서대학교 기계공학부

Kyoungwoo Park^†

School of Mechanical Engineering, Hoseo University, Asan 336-795, Korea

E-mail:

초록

이 논문에서는 overfire air (OFA) (과잉 연소공기)-형 접선주입 석탄가열 보일러의 기하학적인 형상 및 운전조건의 변화가 보일러의 성능에 미치는 영향을 살펴보기 위하여 연소현상과 NOx 발생 특성 등을 수치적으로 규명하고자 하였다. 이를 위하여 전산유체역학 기법을 이용하여 보일러 내부의 난류 열/유동, 화학 반응, 그리고 복사열전달 등의 영향을 고려하였다. 연구 결과, 보일러 내 NOx의 형성은 연소과정, 내부온도, 그리고 화학종의 농도 등에 대단히 의존적이며, 최대 NOx 저감 및 보일러의 효율에 대한 최적의 조건은 OFA에서 공급되는 공기의 양과 분사각도 그리고 보일러 외부의 기하학적인 형상을 변화시킴으로서 얻어질 수 있었다. 또한 이 연구의 운전조건 범위 내에서, OFA에서 공급되는 공기양의 변화가 분사각의 변화보다 NOx 배출량 저감 관점에서 보다 효율적임을 알 수 있었다.

In the present study, the characteristics of combustion phenomena and NOx emission in the OFA-type tangentially injected coal-fired boiler have been investigated numerically in order to find the effect of geometrical variation on the performance of the boiler. For these, numerical analyses of turbulent flow, chemical reaction, and radiation heat transfer are performed by using the computational fluid dynamics method. The predicted results clearly show that NOx formation highly depends on the combustion processes, the temperature and species concentrations. In addition, the optimum conditions for both the maximum NOx reduction and highest boiler efficiency can be obtained by considering the amount of supplied air and the injection angle at OFA, and modifying the boiler configuration. It is also found that the variation of supplied air at OFA is more effective than that of the injection angle for reducing the NOx emission, within the present operating conditions.

Keywords:Computational fluid dynamics;combustion;NOx;overfire air;radiation;tangentially injected coal-fired boiler;turbulent flow

[References]

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[1] Kokkinos A, Wasyluk D, Brower M, Barna JJ, Reducing NOx emissions in tangentially-fired boilers-A new approach, ASME International Joint Power Generation Conference, Miami, Florida, USA (2000)

[2] Le Bris T, Cadavid F, Caillat S, Pietrzyk S, Blondin J, Baudoin B, Fuel, 86(14), 2213 (2007)

[3] Soud H, Fukasawa K, Developments in Nox abatement and control, IEA Coal Res 1996: IEACR/89 (1996)

[4] Man CK, Gibbins JR, Witkamp JG, Zhang J, Fuel, 84(17), 2190 (2005)

[5] Molina A, Eddings EGD, Pershing W, Sarofim AF, Progress in Energy and Combustion Science., 26, 5071 (2000)

[6] Diez LI, Cortes C, Pallares J, Fuel., 87, 1259 (2007)

[7] Choi CR, Kim CN, Fuel, 88(9), 1720 (2009)

[8] Shih TH, Lion WW, Shabbir A, Yang Z, Zhu J, Comput. Fluids., 24, 227 (1995)

[9] Magnussen BF, Hjertager BH, On the Structure of Turbulence and a Generalized Eddy Dissipation Concept for Chemical Reaction in Turbulent Flow, 19th AIAA Aerospace Meeting, St. Louis, USA (1981)

[10] Chai JC, Lee HS, Patankar SV, J. Thermo. Heat Transfer., 8, 419 (1994)

[11] Smith TF, Shen ZF, Friedman JN, J. Heat Transfer., 104, 60 (1982)

[12] STAR-CCM+ v4.02, User Guide (2007)

[13] Ergun S, Chem. Eng. Progress., 48, 89 (1952)

[14] Shim ST, A Numerical Study on the NOx Reduction of Tangentially injected coal-fired boiler, M. S. Dissertation, Hoseo University (2012)