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Ultra-Low Emission Burner for High Efficiency Boilers and Furnaces

Ultra-Low Emission Burner for High Efficiency Boilers and Furnaces. Presentation to CIEE January 3, 2000. Presentation Outline. LBNL’s Combustion Fluid Mechanics Research Background of low-swirl burner (LSB) and technology development history

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Ultra-Low Emission Burner for High Efficiency Boilers and Furnaces

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  1. Ultra-Low Emission Burner forHigh Efficiency Boilers and Furnaces Presentation to CIEE January 3, 2000

  2. Presentation Outline • LBNL’s Combustion Fluid Mechanics Research • Background of low-swirl burner (LSB) and technology development history • Progress report on CIEE/DOE-OIT Multi-year Project • Scaling to > 10 MMBtu/hr and commercialization • Internal FGR development • Advanced 2 ppm NOx LSB concept • Laboratory demonstration in Sep. 01

  3. Research Team • Robert K. Cheng*, Senior Scientist • Ian G. Shepherd, Staff Scientist • David Littlejohn*, Staff Scientist • Larry Talbot, Prof. Mech. Eng., U.C. Berkeley • Carlo Castaldini*, Participating Guest & Consultant • Scott E. Fable*, Senior Research Associate • Adrian Majeski*, Senior Research Associate • Gary L. Hubbard*, Computer System Engineer • Research Collaborators: • C. Benson* (ADLittle), B. Slim* (Gasunie), R. Srinivassen (Honeywell), C. K. Chan (H.K. Poly. U.), P. Greenberg (NASA Glenn), N. Peters (RWTH-Aachen), G. S. Samuelsen* (UC Irvine), J. Lee (Solo Energy), K. O. Smith (Solar Turbines) * participants of CIEE/DOE-OIT project

  4. Mission • Conduct research on combustion fluid mechanics to provide a basis for new and improved energy technologies that have minimum negative impact on the environment • Transfer basic knowledge to stationary heat and power generating systems

  5. Motivations • Fluid mechanical processes such as turbulence control combustion efficiency, flame stability, formation of pollutants and transition to detonation • Turbulent combustion theories and predictive numerical models rely on fundamental understanding of flame-turbulence interactions • Advances in high efficiency and low emission combustion devices require fundamental knowledge of combustion fluid mechanics phenomena

  6. Programmatic Objectives • Elucidate fundamental fluid mechanical processes that control flame propagation rate, flowfield dynamics and overall flame behavior • Build an experimental foundation for developing and validating theoretical models • Transfer knowledge to advance combustion technologies

  7. Our Emphasis:Premixed Combustion • Theoretical Significance • Flame characteristics, flame speed and power density relate directly to turbulence scales and intensities • Flame dynamics couple to near-field and far-field conditions • Impact on Technology • Significant NOx reduction by lean burn (excess air combustion) • Important combustion technology for heat and power generation

  8. Lean Premixed Combustion - Pollution Prevention Technology • Low NOx due to low flame temperatures • NOx (NO and NO2) formation dominated by thermal generation • Premixed flame temperature can be set by equivalence ratio • No emission of particulate matter • Challenges for developing lean premixed systems • Stabilization, flame stability, noise, vibrations & safety • NOx-CO trade-off • Fuel flexibility • Scaling • Control

  9. Fundamental Flame Turbulence Interaction Processes DOE SC-Basic Energy SciencesLBNL LDRD Flame Coupling With Its Environment NASA Microgravity Combustion Advanced Combustion System Burner & Combustor Development Cal. Inst. of Energy EfficiencyDOE-OPT Adv. Turbine SystemsDOE-OIT Combustion LBNL LDRD Projects

  10. Recent Accomplishments • Fundamental Studies • Designed an experiment to investigate flame structures under intense turbulence to support and verify new theory • Reconciled turbulent flame speed with burning rate • Identified near-field and far-field effects of buoyancy • Technology Transfer and Development • Scaled low-swirl burner to industrial size (1 MW) • Demonstrated low-swirl injector for gas turbine

  11. History of the Low-Swirl Burner • Novel stabilization concept for premixed flames • Discovered in 1991 • Swirl intensity about 1/10 of conventional swirl burners • Does not need recirculation to anchor flame • Exploits propagating nature of premixed combustion • Found to support very lean to very rich flames • Confirmed low emission under lean operation • Developed small LSB (15 TO 120 KW) for pool-heaters (DOE-LTR) • Scaled LSB to 1 MW (CIEE Multi-year Project) • Demonstrated for gas turbine combustors

  12. Propagating against the divergent flow, the flame settles where the local velocity equals the flame speed Flow divergence (generated by low-swirl) above the burner tube is the key element for flame stabilization Small air jets swirl the perimeter of the fuel/air mixture but leave the center core flow undisturbed Fuel/Air mixture Principle of Flame Stabilization by Low-Swirl

  13. Current Status of LSB • Two versions: • Jet-LSB for research and scaling • Vane-LSB for development and commercialization • Scaled 3” burner to 1 MW (3.5 MMBtu/hr) • Demonstrated potential for scaling to 10 MMBtu/hr • Collaborating with commercial boiler OEMs • Licensing discussion with industrial burner OEMs • Laboratory demonstration of external FGR • Laboratory demonstration with partially reformed gas • Laboratory demonstration with low Btu gas firing

  14. LSB fitted to a 15kW (50,000 Btu/hr.) Telstar Spa Heater Computer monitoring of efficiency and concentrations of NO, CO and O2 DOE ER-LTR SupportedLSB Development for Water Heaters • Initiated technology development of LSB • Determined effects of enclosure and orientation • Flame remains robust • Downward firing feasible • Found optimum operating condition • NOx < 10 ppm without compromising efficiency • Developed patented vane-swirler

  15. R a Premixture Rh Screen Exit tube Vane-swirler Top view of patented vane-swirler Vane-Swirler Is The Critical Component Of LSB Technology • Air-jet swirler is deemed too complicated for most applications • Novel design feature centerbody with bypass and angled guide vanes to induce swirling motion in annulus • Screen balances pressure drops between swirl and center flows • US Patent awarded 1999

  16. Increase laboratory burner dimensions by factor of 2 Tested three jet LSBs at LBNL and at UC Irvine Combustion Laboratory 5 cm LSB in LBNL water heater simulator (12 to 18 kW) 5 cm LSB in UCICL burner chamber (18 kW to 106 kW) 10 cm LSB in UCICL furnace simulator (150 to 600 kW) Demonstrate high firing rates Determine swirl requirement and emissions CIEE 70K Exploratory Project to Evaluate LSB for Large Commercial Systems 5 cm LSB 10 cm LSB

  17. REACTANT AIR IN To emission analyzers 80 cm honeycomb L 10.16 cm air premixing zone screens swirl air fuel UCICL Furnace Simulator for Large (10.16 cm ID) Jet-LSB

  18. 5.28 cm L swirl air screens 40 cm premixing zone fuel fuel reactant air UCICL Burner Evaluation Facility for Small (5.28 ID) Jet-LSB

  19. Comparison of Stability Regimes of Large and Small Jet-LSBs Results verify constant velocity scaling for the LSB concept Increase in Sgfor scaled up LSB is proportional to increase in swirler recess distance L. This indicates constant residence time scaling. 0.12 5 cm 10 cm Stable Unstable 0.10 0.08 Geometric Swirl Number , Sg 146 kW 0.06 585 kW 0.04 18 kW 106 kW 0.02 0.00 0 4 8 12 16 20 24 28 U, reference velocity (m/s)

  20. Firing rate (kW) for the 5 cm LSB 25 50 75 100 125 150 25 5 cm Burner 10 cm Burner 20 15 NOx ppm (3% O2) 10 5 600 100 200 300 400 500 Firing rate (kW) for 10 cm LSB NOx Independent of Burner Size and Input Power This 4” diameter low-swirl burner firing at 1.5 MMbtu/hr in a furnace simulator emits NOx = 12 ppm, CO = 20 ppm and HC < 1 ppm

  21. Chamber Size Affects CO Firing rate (kW) for the 5 cm LSB 25 50 75 100 125 150 10000 5 cm, Ac / Ab = 15 5 cm, Ac / Ab = 142 10 cm, Ac / Ab = 733 1000 CO emissions in ppm (corr. to 3% O2) LOG SCALE 100 10 1 100 200 300 400 500 600 Firing rate (kW) for the 10 cm LSB • High CO at low firing due to burner/furnace ineraction • CO concentrations level-off to 25 ppm at higher firing.

  22. UHC Limits Minimum Firing Rate Firing rate (kW) for the 5 cm LSB 25 50 75 100 125 150 125 2800 ppm at 17.5 kW 5 cm, Ac / Ab = 142 10 cm, Ac / Ab = 733 100 75 UHC emissions in ppm (corr. to 3% O2) 50 25 0 100 200 300 400 500 600 Firing rate (kW) for the 10 cm LSB • UHC also depends on chamber/burner interaction. • UHC drops below detectable limit at high firing

  23. California Institute of Energy Efficiency Multi-Year Program (6/99 - 9/00) • LBNL 100K, UCICL 50K • Research Develop and Demonstrate high capacity low-swirl burners up to 5 MMBtu/hr • Determine stable operating conditions for NOx < 10ppm, CO < 20 ppm, and high combustion efficiency • Develop scaling laws for vane-LSB • Continue development of vane-swirler for LSB with FGR • Develop guidelines for burner engineers to adapt LSB to fit different boilers and furnaces • Published a paper in Transactions of the Comb. Inst. • Led to expanded research on LSB with partial steam reformed natural gas

  24. Summary of Results6-99 to 9-00 Pursue More-science-less-art approach to burner design and scaling

  25. Parametric Study of Vane LSB • Burner radius, R • Swirler recess distance, L • Equivalence ratio,f • Reference velocity • Thermal input • Swirl number, S • For Jet-LSB R - swirl jet radius, A - total swirl jet area, m - swirl air flowrate • For vane-LSB - developed new formula

  26. Specifications of Two Vane-LSB Prototypes • R = 2.63 and 3.8 cm, Rh/R = 0.776 • Eight thin guide-vanes with a = 37o and 45o • Perforated plate screens with 60, 65, 70, and 75 % blockage • L = 6.2 and 10 cm • Designed and constructed LSBs with modular design for quick conversion

  27. Defining a Swirl Number • Separate integrals for core and annulus • Expressed in terms of mean axial velocities in the core, Uc and in the annulus, Ua • A simpler form expressed in terms of volumetric mass flow ratio being validated

  28. Defining A Swirl Number for Vane-LSB • Parameters: • Vane anglea • Ratio of burner to center body radii Rh/R =R • centerbody/annular of mass flux ratio • For the 7.68 cm ID LSi a = 37o, R = 0.8 • m can be estimated from effective area ratio

  29. Jet-LSB Vane-LSB Velocity Measurement of Vane LSB Flowfield • Comparison of Centerline Velocity Profiles of Jet-LSB and Vane-LSB to understand the foundation of flame stabilization 10 4 U= 2.5 m/s U= 10 m/s 8 2 U (m/s) Jet LSB 6 0 Vane LSB 4 -2 U (m/s) 0 10 20 30 40 50 Axial Distance (mm) 2 0 -2 -4 0 10 20 30 40 50 Axial Distance (mm)

  30. 1.0 60% 0.9 65% 70% 0.8 75% f at lean blow-off 0.7 0.6 0.5 0 2 4 6 8 10 12 14 Reference velocity U (m/s) Determine LSB Performance With Different Screens and Swirl Numbers • with 65% screen, f at lean blow off is not a strong function of U • Vane-LSB design should have high turn-down Stable regime Blow-off

  31. 104 7.5 cm vane-LSB at 280 kW f = 0.58 103 CO ppm (3% O2) 102 f = 0.95 101 Emission target area for new burners 100 0.0 5.0 10.0 15.0 20.0 25.0 NOx ppm (3% O2) Tested Medium (7.68 cm ID) Vane-LSB in Boiler Simulator at Arthur D. Little Medium Vane-LSB • 210 < Q < 280 kW • 0.58 < f < 0.95

  32. Fuel Line Inlet Mounting Flange Fuel Line Inlet Refractory sleeve Premixer Main Air Line 14.5" Premixer Main Air Line LSB Demonstrated at 1 MW • Extensive testing of 7.6 cm LSB at UC Irvine Combustion Lab.

  33. 40.0 0.18 MW 0.3 MW 30.0 0.6 MW 0.9 MW 1 MW NOx ppm (3% O2) 20.0 10.0 0.0 0.60 0.70 0.80 0.90 1.00 1.10 1.20 Equivalence Ratio, f Emissions of vane-LSB match Best Available Control Technology • Reached 1 MW thermal input and found lower NOx emissions with CO < 25 ppm and UHC below detectable limit LSB operating in UCICL furnace at 0.6 MW

  34. Attributes of LSB for Furnace and Boiler Applications • Simple Low pressure drop design for ultra-lean premixed flames that is scalable to different capacities • Accepts different fuel types and fuel blends • High turndown (at least 60:1) • Flame does not hum • Flash back conditions can be predetermined • Ignites easily from either upstream or downstream • Burner does heat up during operation • Flame is not sensitive to enclosure or constriction • Further NOx reduction with FGR

  35. 1000 f = 0.8 No FGR f = 0.825 f = 0.85 f = 0.8 With FGR f = 0.835 100 CO (3% O2) 10 1 0 5 10 15 NOx (3% O2) Laboratory Demonstration of LSB with External FGR • 2” LSB with vane-swirler fitted to a Telstar heat exchanger • Flue gas drawn at the chimney • Tested at 6 to 16kW with FGR up to 30%

  36. DiscoveredAdvanced 2 ppm NOx LSB Concept

  37. Barriers and Constraints to Reaching < 2 ppm NOx • Burner stability near lean limits • High CO and HC emissions • Flame out and light off • Safety concerns • Excessive external FGR compromises efficiency • Require precise control • Lack of fuel flexibility and modulation capability

  38. Combustion Scheme Based on Partial Reformed Gas • Exploit combustion features of hydrogen enriched natural gas flames • Presence of OH radical suppresses CO the ultra-lean combustion conditions that deliver < 5 ppm NOx • H2 lowers the lean flammability limit of natural/air combustion system thereby increasing the stability margin • Needs advanced lean premixed burner technology to capture these benefits

  39. Steam Reforming CnHM+ nH2O  nCO + (n + m/2) H2H = 226 kj/mole • Proven Commercial Technology • Vendors for large and small reformers • Thermal recuperators demonstrated for gas turbines • Typical Industrial applications • Temperature = 14000F (800oC) • Ni-based catalyst active at 300oC • Added water to maximize H2 concentration • Need research and development on partial reforming

  40. Firing synthetic partially reformed gas with FGR at 60 kBtu/hr Varied methane/air equivalence from 0.78 < f < 0.85 Varied reformed gas ratio from 0 to 20% Varied FGR from 0 to 30% Stable flame observed under all conditions with no flashback or blowoff Confirm feasibility of LSB to implement this scheme LBNL Demonstration

  41. 0% 10% 20% Burning of Partially Reformed Gas Lowers NOx and CO • Widens NOx-CO valley • NOx < 2 ppm, CO < 10 ppm at 0.75 < f < 0.8 with 23 % reformed gas • Needs to optimize f with percentage of partially reformed gas 1000 Reformed Gas 100 CO (3% O2) 10 1 0 2 4 6 8 10 12 NOx (3% O2)

  42. Overcoming Barriers • Burner stability near lean limits • H2 in partially reformed gas improves lean stability limit • High CO and HC emissions • High OH radical pool leading to faster CO burnout • Flame out and light off • LSB with partially reformed gas is stable beyond current burner limits • Safety concerns • Burning of partially reformed gas expands the boundaries of operation, improves margin of safety • Excessive external FGR affects efficiency • Operate with lower excess air, while preserving low emission • Tight control • LSB is resilient to rapid changes in mixture and flow conditions • Use of partially reformed gas further alleviates control needs • Rigid/complex design • No change in LSB design seems necessary

  43. CIEE/DOE-OIT Cost-Shared Program Launched in September 2000 • Objective: RD&D of commercial and industrial size LSBs with optional internal FGR capability that burn partial reformed natural to reach the ultimate performance target of 2 ppm NOx (3% O2). • Participants: CIEE Component: LBNL, CMC Engineering DOE-OIT Component: LBNL, A. D. Little • Current Funding Level: CIEE 300K, DOE-OIT 500K (FY01)

  44. Overall Strategy • Build upon CIEE Burner Research Effort • Two synergistic cost-shared developmental programs • CIEE Component • Develop scaling methods for large industrial LSBs • Bench and pilot scale development of integrated partial reformer and LSB technologies • DOE-OIT Component • Conceptual design and evaluation of LSB with internal FGR and scale up to large industrial size • Planned commercialization schedule < 25 ppm in 2001, < 5 ppm in 2003, < 2 ppm in 2007?

  45. Planned Schedule

  46. CIEE Component - Sep 00 to Sep 01 • LSB scaling and demonstration for large industrial systems • Bench and pilot-scale development and demonstration of LSB with FGR and partial reformer • Tasks: • Scale-up and testing of LSB with FGR at UCICL (LBNL) • Computational modeling of reformer kinetics (LBNL, CMC) • Engineering analysis of reformer design, heat transfer and operation and bench-scale simulation testing with LSB (CMC, LBNL) • Commercialization of basic LSB for industrial applications

  47. DOE-OIT Component - Oct 00 to Sep 01 • Development, design, scale-up, and evaluation of LSB with internal FGR capability • Integration of LSB to commercial and industrial systems • Tasks: • Determine optimum operating conditions for LSB with FGR and partially reformed natural gas (LBNL) • Design develop and evaluate premixer to enable internal FGR in LSB systems (ADLittle) • Demonstrate LSB with internal FGR to 2 MMBtu/hr (ADLittle/LBNL)

  48. CIEE Component - Oct 01 to Sep 02 • Demonstration of partial reformer concept for industrial systems at pilot scale • Tasks: • Select demonstration site and defining demonstration target (LBNL/OEM) • Bench scale partial reformer fabrication and assembly (CMC) • Economic and market assessment of ultra-low NOx systems (CMC/LBNL) • Secure commercial manufacturing agreement and licensing for large industrial 5 ppm NOx natural gas fired LSBs (LBNL)

  49. DOE-OIT Component - Oct 01 to Sep 02 • Scale up of LSB with internal FGR to > 10 MMBtu/hr • Development of large LSB for internal FGR and optimized for partial reformed gas operation • Plan pilot scale testing of internal FGR LSB with demonstration partner • Tasks: • Develop scaling parameters for LSBs with partial-reformed-gas and internal FGR capabilities (LBNL) • Perform pilot scale testing (LBNL, ADLiltte, OEM)

  50. Progress Report 10-00 to 1-01

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