1. CFD Modeling for Design of NOx Reduction in Utility Boilers Seventeenth Annual ACERC Conference Salt Lake City, UT February 20-21, 2003 S. Vierstra J.J. Letcavits M.A. Cremer, B. R. Adams, J.R. Valentine

2. Why Use CFD Modeling? l Stringent NO X emissions limits imposed on utilities l SCR can be used to achieve limits, but is expensive l Other less expensive NO X reduction options such as OFA are available l CFD is a cost effective approach to evaluate options

3. Summary of Reaction Engineering International (REI) Boiler Modeling  NOx REDUCTION STRATEGIES »Staging, OFA, ROFA »Reburning, FLGR, SNCR, RRI »Co-firing, Fuel Blending & Switching »Advanced Concept LNBs & Proof-of-Concept Furnaces  OPERATIONAL IMPACTS »CO Oxidation »Unburned Carbon-in-Ash (LOI) »Waterwall Wastage »Heat Rate  over 100 Utility Boilers Modeled  ~37,000 MW Capacity  Cyclone, Turbo, Wall, & T-fired  Firing Coal, Oil, Gas, Biomass, Petcoke, Tires, Blends

4. Project Objectives l Design and evaluate NOx reduction due to OFA in two units »265 MW wall-fired PC unit »530 MW cyclone-fired unit

5. Wall Fired PC Unit l 265 MW B&W Opposed Wall Fired l 18 Babcock Borsig Power CCV low NOx Burners l Subcritical l Eastern Kentucky bituminous coal (1% Sulfur) l Baseline NOx emissions 0.6 lb/MMBtu 12 FW Burners Partial Division Wall Superheater Pendants 6 RW Burners

6. Baseline Model 265 MW Wall Fired Unit l One-half furnace modeled – symmetry plane l Cartesian grid l 650,000 computational nodes l Vertical model exit downstream of secondary superheater

7. Baseline Coal Particle Trajectories 265 MW Wall Fired Unit

8. Baseline Model Predictions 265 MW Wall Fired Unit

9. Predicted CO Distribution 265 MW Wall Fired Unit Proposed OFA Elevation Front Wall > 20,000 ppm 0 ppm Front Wall

10. OFA Design Driven by Location of High CO and High Mass Flow Front Wall Rear Wall Symmetry Plane Side Wall Front Wall Rear Wall Symmetry Plane Side Wall CO (ppm) 0 >20,000 Axial Mass Flux (kg/m 2 /s) < 0 > 4.5

11. Proposed OFA Port Layout 265 MW Wall Fired Unit l 7 rear wall ports l 4 front wall ports l Interlaced rather than opposed l Elevation 10 ft above top burners l OFA jet velocity 170 ft/sec l Two configurations at different furnace staging levels l Burner modifications to maintain primary to secondary burner velocity ratio

12. Predicted Results – OFA 265 MW Wall Fired Unit Furnace Staging Burner Modifications Predicted NOx Predicted Carbon in Fly Ash Predicted Furnace Exit CO Baselinenone 0.58 lb/MMBtu 8%85 ppm Initial OFA0.90 primary & secondary 0.39 lb/MMBtu 20%801 ppm Revised OFA0.95primary only 0.38 lb/MMBtu 13%1000 ppm

13. Post Retrofit Test Data 265 MW Wall Fired Unit

14. Cyclone Fired Unit l B&W 530 MW, supercritical l Opposed wall-fired »2 over 3 on front wall »3 over 3 on rear wall l 60% PRB/40% Eastern bituminous fuel l Barrel water injection for NO 2 plume control l Baseline NOx emissions 1.8 – 1.9 lb/MMBtu

15. Cyclone Barrel Model »10’ diameter »Radial Burner »350,000 computational cells »Unstaged (SR=1.15) and staged (SR=0.90) were simulated Baseline particle trajectories

16. Furnace Model l Barrel exit results were interpolated into 750,000 computational cell furnace furnace model l Simulations were performed for the unstaged baseline condition and staged OFA configurations l Baseline results: »Predicted furnace exit gas temperature consistent with observations »Furnace exit CO predicted to be less than 100 ppm »Predicted NOx emissions of 1.96 lb/MMBtu consistent with CEMs

17. Initial OFA Port Layout CO (ppm, wet) 5 front wall ports 6 rear wall ports l Ports placed above barrel centerlines l Baseline results suggested that front/rear port distribution should be reversed – structural limitations did not allow this l Staggered ports allow for deeper penetration/improved mixing l 300 ft/s jet velocities l Predictions show high CO pockets in corners, average exit CO 2093 ppm (vs. 85 ppm baseline)

18. Modified OFA Port Layout l Prediction of high furnace exit CO led to modified design l Addition of 4 low velocity (100 fps) auxiliary ports in the corners l 16% of total OFA flow to auxiliary ports l Main port jet velocity proportionately reduced l Predicted average exit CO 413 ppm (vs. 2093 ppm initial OFA layout) CO (ppm, wet) 4 low velocity auxiliary ports

19. Overall Predictions CO (ppm, wet) Baseline OFA Case 1 OFA Case 2

20. NOx (ppm, wet) Baseline OFA Case 1 OFA Case 2 Overall Predictions

21. Predicted Furnace Exit Temperature Predicted CO (dry) Predicted NOx Baseline2438 F.217 ppm 1.96 lb/MMBtu Initial OFA (case 1) 2299 F.2093 ppm 0.35 lb/MMBtu Revised OFA (case 2) 2340 F.413 ppm 0.37 lb/MMBtu OFA Case 32364 F.324 ppm 0.47 lb/MMBtu

22. Post Retrofit Test Data 530 MW Cyclone Fired Unit

23. Summary l CFD modeling is an effective tool in design and evaluation of NOx reduction technologies in utility boilers l CFD utilized to develop conceptual design of OFA system in 265 MW wall fired furnace fitted with low NOx burners »Model predictions indicated NOx reductions over 30% could be achieved with limited increase in stack CO and carbon in fly ash »Subsequent installation of the OFA system has confirmed predictions l CFD based OFA design developed for 530 MW cyclone fired furnace »Model predictions indicated 80% NOx reduction with small increase in furnace exit CO »Subsequent installation confirmed predictions of 0.37 lb/MMBtu

24. Acknowledgements l This work was supported by American Electric Power (AEP)