Slide 1: The Practical Use of CFD in Burner Development and Boiler Applications
The Practical Use of CFD in Burner Development and Boiler Applications Matthew Martin ClearSign Technologies
Slide 2: The Practical Use of CFD in Burner Development and Boiler Applications
The Practical Use of CFD in Burner Development and Boiler Applications • What is Computational Fluid Dynamics (CFD)? • CFD: A brief history in boilers and burners • Why use CFD in burner development? • Why use CFD for boiler applications? • Examples • Summary 2
Slide 3: What is CFD?
What is CFD? • A virtual wind tunnel • The solution of partial differential equations • Navier-Stokes • Turbulence • Radiation • Chemistry • Usually, industrial CFD is • Steady-state • Finite-volume • Modeled turbulence • Used to tell us what the fluid flow is going to do given a design and a set of
Slide 4: CFD History – Boilers and Burners
CFD History – Boilers and Burners • A non-exhaustive literature survey suggests that boiler CFD modeling started from the largest scales • Conversely burner modeling history suggests the smallest details were investigated first 4
Slide 5: Burner Firing Environment
Burner Firing Environment • Burner performance is affected by volumetric heat density • NOx • Flame characteristics • Prior versions of API 560 limited to 16,000 Btu/h-ft2 • Still many poor performing installations 5
Slide 6: Burner Firing Environment
Burner Firing Environment Hearth Heat Intensity vs Burner Fired Duty for • A different metric improves Various Equipment screening 3,500,000 • Fired duty / Burner mounting 3,000,000 Hearth Heat Intensity [Btu/ft2] High wall area 2,500,000 2,000,000 • Adopted by API 560 1,500,000 Moderate • Limit 300
Slide 7: CFD for Burner Design
CFD for Burner Design • Limitations of physical testing • Cannot test every boiler design • Cannot test every heat release • Iterative design is relatively expensive Virtual Burner Design is Possible 7
Slide 8: CFD-First Burner Design Example
CFD-First Burner Design Example • Project Goals • Low excess air operation • Low NOx operation • Shorter flames • Increased efficiency • No physical testing 8
Slide 9: Why not High Excess Air?
Why not High Excess Air? • Heat transfer • Premixed combustion • Fuel lean → Lower NOx • Too lean → Unstable combustion (100% Excess Air) • Practically not achieving performance High Excess Air Only is not Practical 9
Slide 10: A Step Change in Performance
A Step Change in Performance Point Heat Release CO NOx Oxygen [MMBtu/h] [ppm @ 3% O2] [ppm @ 3% O2] [% Dry] 1 10.92 145.00 6.00 3.10 2 12.74 5.00 5.00 3.10 3 14.56 0.00 4.00 3.00 4 16.38 0.00 3.00 3.10 5 18.20 0.00 3.00 3.10 6 14.56* 0.00 2.00 3.00 * Tertiary fuel circuit activated. Less than 2.5 pp
Slide 11: CFD Simulation – Flame Shape
CFD Simulation – Flame Shape Steady-State Simulation Reproduces Flame Shape 11
Slide 12: Burner Flame at Various Rates
Burner Flame at Various Rates 12
Slide 13: CFD Simulation – Firetube Boiler
CFD Simulation – Firetube Boiler Predicted < 2.5 ppm (@ 3% Excess Oxygen) in a Firetube Boiler 13
Slide 14: Design Permutations, Combinations, and Iterations
Design Permutations, Combinations, and Iterations • Rapid prototyping of burner designs made possible CFD Stack Oxygen First Pass Efficiency cCO cNOx • Relatively detailed and [% Dry] Swirler Fuel NOx Reducing Steam [%] [ppm] [ppm] 5.28% LOW HIGH 67.83 0.02 2.46 accurate assessment of 5.77% 6.00% LO
Slide 15: CFD for Boiler Applications
CFD for Boiler Applications • Why use CFD on a per application basis? • Wide variety of boiler designs • Determine feasibility for edge cases • Risk mitigation for early adopters • Custom design for special requirements 15
Slide 16: Summary
Summary CFD Simulations for Burners and Boilers • Computational Fluid Dynamics (CFD) is well-tested for boiler and burner development • Improved and custom burners can be developed rapidly • Not all boilers are the same! • Boiler design affects burner performance CFD Provides Reduced Risk • Per-appl
Slide 17: www.clearsign.com
Boost Decrease Reduce NOx Operational Costs Emissions Efficiency www.clearsign.com 17