5. EKMA Model

6.  Control of Nitrogen oxides  NO, NO 2, NO 3, N 2 O, N 2 O 3, N 2 O 4, N 2 O 5 NOx : NO + NO 2  Major Factors for NOx Formation Combustion Temperature Combustion Time Amount of Excess Air for Combustion Conditions for Complete Combustion ( 3T : Temperature, Time, Turbulence) Incinerator of Home Boiler – 1650 ℃ (NO : 1000ppm) 1000 ℃ (NO : 10ppm) Control of Nitrogen Oxides N 2 + O 2 =2NO NO + 1/2O 2 = NO 2 NO + O 3 = NO 2 + O 2

7.  Emitted NOx Pattern Thermal NOx ( 열형 NOx) : Combustion Temperature ( N 2, O 2 ) Fuel NOx ( 연료형 NOx) : Nitrogen Content in Fuel  Determination Factors for NOx Emissions Operating Condition Nitrogen Content in Flue Gas Nitrogen Content in Fuel  Representative NOx Control Methods 1. Fuel Denitrification ( 연료 탈질법 ) 2. Combustion Modification ( 연소 개량법 ) 3. Flue Gas Treatment ( 연도 가스 처리법 )

8. 1. Before Burning ( 연소 이전 ) Fuel Denitrification ( 연료 탈질 ) 2. During Burning ( 연소 과정중 ) Combustion Modification ( 연소 개량 ) Catalytic Combustion ( 촉매 연소 ) 3. After burning ( 연소 후 ) Flue Gas Treatment ( 연도가스 처리 ) Catalytic Emission Control ( 촉매 배출 제어 ) NOx Control Techniques

9. Strategies for Combustion Modification Reduce peak temperatures o f the flame zone Reduce gas residence time i n the flame zone Q: Temperature as a function of equivalent ratio?

10. 1.Fuel Denitrification ( 연료 탈질법 ) coal, shale, Heavy Oil Fuel Liquefaction Mixing with H 2 2. Combustion Modification ( 연소 개량법 ) -> Modification of Combustion Conditions Low Excess Air ( 저잉여 공기법 ) Staged Combustion ( 단계식 연소법 ) Off-Stoichiometric Combustion : OSC ( 비양론적 연소법 ) Fuel Gas Recirculation ( 연 도가스순환법 ) Reduced Air Preheat ( 감소된 공기 예열법 ) Gas Reburning ( 가스 재 연소법 ] Steam injection ( 증기 주입법 ) Low NOx Burners ( 저 NOx 연소로법 )

12. Air and Fuel mixing can be effective in a Burner Less Excess Air required (20%) disadvantage : Sometimes smoke and high CO appear (20%) Low Excess Air [ 저잉여공기법 ]

13. Staged Combustion ( 단계식 연소법 ) Air/Fuel Mixture – two step combustion Fuel Rich Area – 1st step Air Rich Area – 2nd step Lowering combustion T – NOx control Efficient for Thermal & Fuel NOx [30 – 50%] Off-Stoichiometric Combustion : OSC ( 비양론적 연소법 )

14. Flue Gas Recirculation [ 연도 가스 순환법 ] To reduce thermal NOx from big Boiler (Oil 과 Gas] Recirculation of Flue Gas (10-30%) Disadvantage : High Initial Cost. Efficiency : 40 -50 %

15. Relatively new method NOx control by lowering combustion Temp in a boiler and dissipating heat quickly (40-60%) To lower N 2 and O 2 reaction rate at Peak combustion Temp Low NOx Burners ( 저 NOx 연소로 법 )