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Andr é s Colorado Vince McDonell Paper # 070IC-0200

Impact of Ethane, Propane, and Diluent Content in Natural Gas on the NOx emissions of a Commercial Microturbine Generator. Andr é s Colorado Vince McDonell Paper # 070IC-0200. 8 th U. S. National Combustion Meeting May 19-22, 2013. Outline. Introduction Motivation Methodology

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Andr é s Colorado Vince McDonell Paper # 070IC-0200

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  1. Impact of Ethane, Propane, and Diluent Content in Natural Gas on the NOx emissions of a CommercialMicroturbine Generator Andrés Colorado Vince McDonell Paper # 070IC-0200 8th U. S. National Combustion Meeting May 19-22, 2013

  2. Outline • Introduction • Motivation • Methodology • Experiments • CFD • Chemical Reactor Network • Results • Conclusions

  3. Motivation (NOx emissions) • NOx Problems • NOx forms nitric acid - Acid rain • NO2 is a traveler (lifetime) • Photochemical smog (NO2 reacts with ozone+ sunlight) • Health

  4. Motivation (NOx regulations) NOx Emission Trends for All Acid Rain Program Units, 1990–2009. Source: EPA, 2010 • In the near future, regulations will be even more stringent. • Manufacturers and scientist must find solutions to reduce even more NOx emission. • The Clean Air Act requires states to reduce ground-level ozone • From 1990 to 2009 the SO2 rate has dropped 71 % and the NOx rate has dropped 77 %.

  5. Motivation (problem solving) How can combustion scientists reduce NOx emissions? By understanding How the NOx is formed in the combustion process Depends on Fluid dynamics Chemistry (kinetics) The composition of the reactants The way we mix the reactants-mixing patterns-recirculation The addition of other compounds impacts the kinetics-NOx Complex systems such as turbine-combustion chambers

  6. Predicting NOx emissions (MTG case) Experiments MTG Chemical kinetics software tools for solving complex chemical kinetics problems. • Complete set of chemical kinetics • GRI-Mech contains 325 reactions and 53 species • Short calculation time • What about the fluid dynamics in the chamber? • We can measure actual NOx • What about the chemical kinetics? • What about the fluid dynamics in the chamber?

  7. Predicting NOx emissions (MTG case) Computational fluid dynamics • Full access to the combustion chamber. • Nice colors that make everything understandable • chemistry  • A 3D geometry requires a lot of meshes. We need to solve the fundamental equations for every mesh. • What about the chemical kinetics? • Coupling fluid dynamics with full chemistry. High computer cost (simulations can take months)

  8. Methodology CFD Chemical kinetics + Chemical reactor network (CRN)

  9. Methodology • Step 1: Gain Details about Reaction Structure Mesh of the combustion chamber, C65 engine • CFD models • Turbulence: k-ε • Combustion: Finite rate/Eddy dissipation • Methane air- 2 steps • Boundary conditions=experimental CFD contours • Outputs from the CFD are inputs to the CRN • Residence time • Volume of each reactor • Temperatures • Flow distribution. • Flame shape.

  10. Methodology • Step 2: Develop CRN . Air dilution zone Block 1. Premixing and distribution Block Post-dilution & exhaust . Block 4. & 5. Planeof 4 injectors 7. secondary air 8. Post dilution zone 2. Plane of 2 injectors 6. Post flame

  11. Results • CRN performance • Very good agreement Comparison NOx emissions, experimental vs CRN

  12. Results • Effect of higher hydrocarbons • Effect of diluents 100% CH4 80%CH4-20%C3H8 85%CH4-15%C2H6 80%CH4-20% CO2

  13. Results- Effect of heavier alkanes Comparison of NOx emissions (CRN and experimental) at constant adiabatic flame temperature and preheated combustion air temperature (AFT= 1850K, preheated air temperature=835K) Experimental and CRN NOx pathways Hack and McDonell 2008 found that at full load the addition of higher hydrocarbons leads to higher NOx emission levels when compared to 100% methane. Influence of the different NOx pathways .

  14. Results- Effect of diluting gases Experimental and CRN Higher levels of diluent produce less NOX Influence of the different NOx pathways.

  15. Conclusions • The reactor network analysis (RNA) indicated that the addition of heavier hydrocarbons increases the production NOx. On the other hand the addition of diluents reduces the production of NOx. The same trend was observed experimentally. • The CRN methodology indicated that under the conditions of the MTG the N2O pathway is responsible for over 50% of the NOx emitted by the turbine.

  16. Acknowledgements • Dr. Vince McDonell • Professor S. Samuelsen • Zhixuan Duan • Howard Lee • Brendan Shaffer • APEP mates.

  17. Questions?

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