Alan S. Feitelberg

Chemical mechanisms of NOx formation for gas turbine conditions

Crucial reactions for NOx and CO were identified, expressions for their kinetics were improved using theoretical predictions, and the improved mechanism was exploited by probing a data set from high-pressure turbulent combustion with a two-reactor model. Reaction-path analysis and linear sensitivity analysis were combined to identify the reactions that were most important in determining NOx and CO concentrations in lean (=0.6), premixed, laminar methane/air flames ranging in pressure from 1 to 40 atm. These reactions were then analyzed using. Quantum-RRK techniques and literature data. Revised rate constants and additional reactions were proposed. Analysis revealed that thermal or Zeldovich formation of NO from N2+O apparently proceeds via the electronically excited O1D) state, not by direct reaction with ground-state O(3P). The chemical mechanism was used to model NOx measurements taken from the burned-gas zone of lean, premixed, turbulent, 5 to 10 atm methane and ethane flames stabilized on a perforated plate. The flow field of the turbulent flames was modeled as a perfectly stirred reactor (PSR) and a plug flow reactor (PFR) in series so that the complex chemistry could be included. Agreement between the model and the data was good, indicating that the PSR/PFR approximation is valid for predicting NOx from lean, premixed flames. The nitrous oxide (N2O) pathway was shown to be the dominant route to NOx formation at lower temperatures (more fuel-lean), with thermal NOx becoming more important at higher temperatures (closer to stoichiometric). The contribution of prompt NOx to the total NOx formed was found to be relatively small under fuel-lean conditions, although it becomes the dominant route to NOx under fuel-rich conditions.

Reduced NOx diffusion flame combustors for industrial gas turbines

This paper describes reduced NO x diffusion flame combustors that have been developed for both simple cycle and regenerative cycle MS3002 and MS5002 gas turbines. Laboratory tests have shown that when firing with natural gas, without water or steam injection, NO x emissions from the new combustors are about 40 percent lower than NO x emissions from the standard combustors. CO emissions are virtually unchanged at base load, but increase at part load conditions. Commercial demonstration tests have confirmed the laboratory results. The standard combustors on both the MS3002 and MS5002 gas turbine are cylindrical cans, approximately 10.5 inches (27 cm) in diameter. A single fuel nozzle is centered at the inlet to each can and produces a swirl stabilized diffusion flame. The walls of the cans are louvered for cooling, and contain an array of mixing and dilution holes that provide the air needed to complete combustion and dilute the burned gas to the desired turbine inlet temperature. The MS3002 turbine is equipped with six combustor cans, while the MS5002 turbine is equipped with twelve combustors. The new, reduced NO x emissions combustors (referred to as a lean head end, or LHE, combustors) retain all of the key features of the conventional combustors; the only major difference is the arrangement of the mixing and dilution holes in the cylindrical combustor cans. By optimizing the number, diameter, and location of these holes, NO x emissions can be reduced considerably. Minor changes are also sometimes made to the combustor cap. The materials of construction, pressure drop, and fuel nozzle are all unchanged. The differences in NO x emissions between the standard and LHE combustors, as well as the variations in NO x emissions with firing temperature, are well correlated using turbulent flame length arguments. Details of this correlation are presented.

Performance of a Reduced NOx Diffusion Flame Combustor for the MS5002 Gas Turbine

This paper describes a reduced NO x diffusion flame combustor that has been developed for the MS5002 gas turbine. Laboratory tests have shown that when firing with natural gas, without water or steam injection, NO x emissions from the new combustor are about 40 percent lower than NO x emissions from the standard MS5002 combustor. CO emissions are virtually unchanged at base load, but increase at part load conditions. The laboratory results were confirmed in 1997 by a commercial demonstration test at a British Petroleum site in Prudhoe Bay, Alaska. The standard MS5002 gas turbine is equipped with a conventional, swirl stabilized diffusion flame combustion system. The twelve standard combustors in an MS5002 turbine are cylindrical cans, approximately 27 cm (10.5 in.) in diameter and 112 cm (44 in.) long. A small, annular, vortex generator surrounds the single fuel nozzle that is centered at the inlet to each can. The walls of the cans are louvered for cooling, and contain an array of mixing and dilution holes that provide the air needed to complete combustion and dilute the burned gas to the desired turbine inlet temperature. The new, reduced NO x emissions combustor (referred to as a lean head end, or LHE, combustor) retains all of the key features of the conventional combustor; the only significant difference is the arrangement of the mixing and dilution holes in the cylindrical combustor can. By optimizing the number; diameter, and location of these holes, NO x emissions were substantially reduced. The materials of construction, fuel nozzle, and total combustor air flow were unchanged. The differences in NO x emissions between the standard and LHE combustors, as well as the variations in NO x emissions with firing temperature, were well correlated using turbulent flame length arguments. Details of this correlation are also presented.

Reduced NOx Diffusion Flame Combustors for Industrial Gas Turbines

This paper describes reduced NOx, diffusion flame combustors that have been developed for both simple cycle and regenerative cycle MS3002 and MS5002 gas turbines. Laboratory tests have shown that when firing with natural gas, without water or steam injection, NOx emissions from the new combustors are about 40% lower than NOx emissions from the standard combustors. CO emissions are virtually unchanged at base load, but increase at part load conditions. Commercial demonstration tests have confirmed the laboratory results.The standard combustors on both the MS3002 and MS5002 gas turbine are cylindrical cans, approximately 10.5 inches (27 cm) in diameter. A single fuel nozzle is centered at the inlet to each can and produces a swirl stabilized diffusion flame. The walls of the cans are louvered for cooling, and contain an array of mixing and dilution holes that provide the air needed to complete combustion and dilute the burned gas to the desired turbine inlet temperature. The MS3002 turbine is equipped with six combustor cans, while the MS5002 turbine is equipped with twelve combustors.The new, reduced NOx emissions combustors (referred to as a “lean head end”, or LHE, combustors) retain all of the key features of the conventional combustors; the only major difference is the arrangement of the mixing and dilution holes in the cylindrical combustor cans. By optimizing the number, diameter, and location of these holes, NOx emissions can be reduced considerably. Minor changes are also sometimes made to the combustor cap. The materials of construction, pressure drop, and fuel nozzle are all unchanged.The differences in NOx emissions between the standard and LHE combustors, as well as the variations in NOx emissions with firing temperature, are well correlated using turbulent flame length arguments. Details of this correlation are presented.Copyright