DOE Cooperative Agreement No. DE-FC26-00NT40895 Project Officer: Sean Plasynski

1. Pilot-scale Testing and Predictive Model Development for Use in Minimizing NOX Emissions and Unburned Carbon when Cofiring Biomass with Coal DOE Cooperative Agreement No. DE-FC26-00NT40895 Project Officer: Sean Plasynski Larry Felix* Steve Niksa Kevin Davis Douglas Boylan P. Vann Bush* Hong-Shig Shim

2. Emissions Benefits of Biomass Cofiring • CO2 Reduction from Unburned Fossil Carbon • SO2 Reduction from Displaced Sulfur • Lower NOX Emissions (from Reducing Fuel Nitrogen, at a minimum) • Higher Fuel Volatility from Biomass • LOI Reduction (from Displaced Coal, at a minimum)

3. Cofiring Research • In 2000, The U.S. DOE National Energy Technology Laboratory, through the Office of Energy Efficiency and Renewable Energy’s Biomass Power Program has Funded 11 New Research Grants to Study Biomass Cofiring • This presentation presents selected results from one of these grants: “Development of a Validated Model for Use in Minimizing NOX Emissions and Maximizing Carbon Utilization When Cofiring Biomass with Coal”

4. Specific Program Objectives • Develop a consistent, extensive biomass cofiring database • relationships between NOx and biomass cofiring parameters • effects on flame stability, carbon burnout, slagging and fouling, and particulate and gaseous emissions • Develop and validate a biomass cofiring model • forecast NOx and LOI for given fuel combination with specified cofiring configuration • optimize cofiring configuration to minimize NOx and unburned carbonfor specified fuels

5. PROJECT TEAM Southern Research Institute Southern Company (Combustion Research Facility) Niksa Energy Associates (Cofiring Process Model) Reaction Engineering International (CFD Simulations) Mesa Reduction, Inc (Biomass Preparation)

6. Project Flow Chart CFD Model of Combustor Biomass NOx-LOI Model Combustion+Gas Chemistry Models Controlled Pilot-Scale Cofiring Tests Database NOx-LOI Other Combustion & Emission Properties

7. EXPERIMENTAL PROGRAM

8. Combustion Research Facility • All testing conducted at the SRI/SCS 6.0 MMBtu/hr Combustion Research Facility (at 3.5 MMBtu/hr) • Continuous measurement and logging of ~ 200 pertinent process parameters • In-situ testing for mass emissions, particle size, char, pyrometry, ash resistivity, gases (O2 at furnace exit and at CEM location, CO, CO2, SO2, NOX, NH3, H2O, HCl). • On-site wet chemical flue gas and ash analyses, CHN (for carbon in ash), fuel heat value measurement • Instrumented CE-Raymond Model 352 Deep Bowl mill

9. Pilot-Scale Test Facility P a c k e d - C o l u m n C o n v e c t i v e S c r u b b e r S e c t i o n P u l s e - J e t B a g h o u s e H e a t E x c h a n g e r s F u r n a c e P u l v e r i z e d F u e l B i n C o a l B u r n e r F e e d e r E l e c t r o s t a t i c P r e c i p i t a t o r

10. Locations for Biomass Injection

11. Major Variables within the Test Matrix

12. Typical Coals

13. Biomass Fuel Analyses

14. Test Cases in Data Base

15. SELECTED TEST RESULTS • NOX Reductions from Cofiring Biomass • High, Medium, and Low Volatile / FC Ratios • Single (Mainly) and Dual-Register Burner • Sawdust and Switchgrass • 15% Overfire Air • 0% to 20% Biomass

23. What Do These Data Reveal? • There is No Guarantee that NOX Emissions will be Reduced when Coal is Cofired with Biomass • Complex Relationships Exist Among Furnace Operating Parameters, Burner Design, Cofiring Geometry, Biomass Choice, and Coal • NOX Reductions from Adding Biomass can be Much Greater than, Equal to, or Much Less than than the Amount of Fuel Nitrogen Replaced when Biomass is Cofired with Coal

24. General Conclusion In Order to Understand the Nature of the Interactions that have been Observed, Fundamental Questions of Fuel Chemistry and Combustion Must be Addressed

25. MODEL DEVELOPMENT

26. Model Requirements • Model results must agree with results in the experimental database - no adjustable parameters in the submodel for gas phase chemistry. • The model must incorporate a formalism that is generally applicable to any biomass cofiring configuration - from pilot-scale to full-scale.

27. Model Assumptions • It is not currently possible to incorporate detailed chemical reaction mechanisms into conventional CFD simulations of pulverized coal and biomass flames - The reaction mechanism for chemistry in the gas phase contains 444 elementary reactions among 66 species, including all relevant radicals and N-species (Glarborg et al. 1998). • To predict NOX and LOI, incorporate detailed gas-phase chemistry through advanced CFD post-processing methodology developed by NEA.

28. Model Implementation • Perform CFD simulation of the SRI/SCS pilot-scale furnace for as many test conditions as feasible using REI and REI’s Configurable Fireside Simulator to predict residence time distributions, temperature fields, and mixing intensities within the furnace.

29. Furnace Exit Furnace Zones Burnout Zone OFA Zone Mixing Layer Core Core ERZ ERZ

30. Model Implementation • Define an equivalent network of idealized reactor elements for the pilot-scale furnace from the conventional CFD simulations. • The network is “equivalent” to the CFD flowfield in so far as it represents the bulk flow patterns in the flow. To the extent that the residence time distribution, thermal history, and entrainment rates are similar in the CFD flowfield and reactor network, the chemical kinetics evaluated in the network represent the chemistry in the CFD flowfield.

31. DEVOLATILIZATION ZONE 8 CSTRs, 65 ms NO REDUCTION ZONE 8 CSTRs, 73 ms Char … … Primary Air Volatiles Char DEVOLATILIZATION ZONE, 65 ms NO REDUCTION ZONE, 128 ms Primary Air MIXING LAYER 19 CSTRs, 508 ms Secondary Air … … Tertiary Air (OFA) OFA ZONE 6 CSTRs, 156 ms LOI + Fly ash BURNOUT ZONE 1460 ms Exhaust Gases Reactor Network

32. Model Implementation 3. The reactor network is a computational environment that accommodates realistic chemical reaction mechanisms. Mechanisms with a few thousand elementary chemical reactions can now be simulated on ordinary personal computers, provided that the flow structures are restricted to the limiting cases of plug flow or perfectly stirred tanks.

33. MODEL VALIDATION • Pick Representative Cases • Predict NOX and LOI • Compare with Measurement

34. Predicted vs. Measured NOX

35. Questions