Influence of Pressure and Steam Dilution on NOx and CO Emissions in a Premixed Natural Gas Flame

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Sebastian Göke ◽  
Sebastian Schimek ◽  
Steffen Terhaar ◽  
Thoralf Reichel ◽  
Katharina Göckeler ◽  
...  
Keyword(s):  
Natural Gas ◽  
Scaling Laws ◽  
Combustion Process ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Nox Formation ◽  
Combustion Chemistry ◽  
Air Mass ◽  
Gas Flame ◽  
Reactor Network

In the current study, the influence of pressure and steam on the emission formation in a premixed natural gas flame is investigated at pressures between 1.5 bar and 9 bar. A premixed, swirl-stabilized combustor is developed that provides a stable flame up to very high steam contents. Combustion tests are conducted at different pressure levels for equivalence ratios from lean blowout to near-stoichiometric conditions and steam-to-air mass ratios from 0% to 25%. A reactor network is developed to model the combustion process. The simulation results match the measured NOx and CO concentrations very well for all operating conditions. The reactor network is used for a detailed investigation of the influence of steam and pressure on the NOx formation pathways. In the experiments, adding 20% steam reduces NOx and CO emissions to below 10 ppm at all tested pressures up to near-stoichiometric conditions. Pressure scaling laws are derived: CO changes with a pressure exponent of approximately −0.5 that is not noticeably affected by the steam. For the NOx emissions, the exponent increases with equivalence ratio from 0.1 to 0.65 at dry conditions. At a steam-to-air mass ratio of 20%, the NOx pressure exponent is reduced to −0.1 to +0.25. The numerical analysis reveals that steam has a strong effect on the combustion chemistry. The reduction in NOx emissions is mainly caused by lower concentrations of atomic oxygen at steam-diluted conditions, constraining the thermal pathway.

Influence of Pressure and Steam Dilution on NOx and CO Emissions in a Premixed Natural Gas Flame

2013 ◽  
Author(s):  
Sebastian Göke ◽  
Sebastian Schimek ◽  
Steffen Terhaar ◽  
Thoralf Reichel ◽  
Katharina Göckeler ◽  
...  
Keyword(s):  
Natural Gas ◽  
Scaling Laws ◽  
Combustion Process ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Nox Formation ◽  
Combustion Chemistry ◽  
Air Mass ◽  
Gas Flame ◽  
Reactor Network

In the current study, the influence of pressure and steam on the emission formation in a premixed natural gas flame is investigated at pressures between 1.5 bar and 9 bar. A premixed, swirl-stabilized combustor is developed that provides a stable flame up to very high steam contents. Combustion tests are conducted at different pressure levels for equivalence ratios from lean blowout to near-stoichiometric conditions and steam-to-air mass ratios from 0% to 25%. A reactor network is developed to model the combustion process. The simulation results match the measured NOx and CO concentrations very well for all operating conditions. The reactor network is used for a detailed investigation of the influence of steam and pressure on the NOx formation pathways. In the experiments, adding 20% steam reduces NOx and CO emissions to below 10 ppm at all tested pressures up to near-stoichiometric conditions. Pressure scaling laws are derived: CO changes with a pressure exponent of approximately −0.5 that is not noticeably affected by the steam. For the NOx emissions, the exponent increases with equivalence ratio from 0.1 to 0.65 at dry conditions. At a steam-to-air mass ratio of 20%, the NOx pressure exponent is reduced to −0.1 to +0.25. The numerical analysis reveals that steam has a strong effect on the combustion chemistry. The reduction in NOx emissions is mainly caused by lower concentrations of atomic oxygen at steam-diluted conditions, constraining the thermal pathway.

A Literature Review of NOx Formation Kinetics and a Prediction Method for Lean-Burn, Two-Stroke Natural Gas Engines

2019 ◽  
Author(s):  
Taylor F. Linker ◽  
Mark Patterson ◽  
Greg Beshouri ◽  
Abdullah U. Bajwa ◽  
Timothy J. Jacobs
Keyword(s):  
Natural Gas ◽  
Chemical Properties ◽  
Prediction Method ◽  
Operating Conditions ◽  
Combustion Mechanism ◽  
Nox Emissions ◽  
Lean Burn ◽  
Nox Formation ◽  
Gas Combustion ◽  
No2 Formation

Abstract The increased production of natural gas harvested from unconventional sources, such as shale, has led to fluctuations in the species composition of natural gas moving through pipelines. These variations alter the chemical properties of the bulk gas mixture and, consequently, affect the operation of pipeline compressor engines which use the gas as fuel. Among several possible ramifications of these variations is that of unacceptably high engine-out NOx emissions. Therefore, engine controller enhancements which can account for fuel variability are necessary for maintaining emissions compliance. Having the means to predict NOx emissions from a field engine can inform the development of such control schemes. There are several types of compressor engines; however, this study considers a large bore, lean-burn, two-stroke, integral compressor engine. This class of engine has unique operating conditions which make the formation of engine-out NOx different from typical automotive spark-ignited engines. For this reason, automotive-based methods for predicting NOx emissions are not sufficiently accurate. In this study, an investigation is performed on the possible NO and NO2 formation pathways which could be contributing to exhaust emissions. Additionally, a modeling method is proposed to predict engine-out NOx emissions using a 0-D/1-D model of a Cooper-Bessemer GMWH-10C compressor engine. Predictions are achieved with GRI-Mech3.0, a natural gas combustion mechanism, which allows for simulated formation of NOx species. The implemented technique is tuned using experimental data from a field engine to better predict emissions over a range of engine operating conditions. Tuning the model led to acceptable agreement across operating points varying in both load and trapped equivalence ratio.

Using Multi-Dimensional Combustion Simulations of a Natural Gas/Diesel Dual Fuel Engine to Investigate NOx Trends With Air-Fuel Ratio

2017 ◽  
Author(s):  
Andrew Hockett ◽  
Michael Flory ◽  
Joel Hiltner ◽  
Scott Fiveland
Keyword(s):  
Natural Gas ◽  
Oil And Gas ◽  
Operating Conditions ◽  
Dual Fuel ◽  
Nox Emissions ◽  
Nox Formation ◽  
Jet Flame ◽  
Gas Drilling ◽  
Fuel Ratio ◽  
Wide Range

Natural gas/diesel dual fuel engines used in oil and gas drilling operations must be able to meet NOx emissions limits across a wide range of substitution percentage, which affects the air to natural gas ratio or gas lambda. In a dual fuel engine operating at high substitution, premixed, propagating natural gas flames occur and the NOx formed in such premixed flames is known to be a strong function of gas lambda. Consequently there is interest in understanding how NOx formation in a dual fuel engine is affected by gas lambda. However, NOx formation in a dual fuel engine is complicated by the interaction with the non-premixed diesel jet flame. As a result, previous studies have shown that enriching the air-fuel ratio can either increase or decrease NOx emissions depending on the operating conditions investigated. This study presents multi-dimensional combustion simulations of an air-fuel ratio sweep from gas lambda 2.0 to 1.5 at 80% substitution, which exhibited a minimum in NOx emissions at a natural gas lambda of 1.75. Images from the simulations are used to provide detailed explanations of the physical processes responsible for the minimum NOx trend with natural gas lambda.

Emission Characteristics of a Premixed Cyclic-Periodical-Mixing Combustor Operated With Hydrogen-Natural Gas Fuel Mixtures

2008 ◽  
Author(s):  
Jochen R. Bru¨ckner-Kalb ◽  
Michael Kro¨sser ◽  
Christoph Hirsch ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Combustion Process ◽  
Chemical Reactor ◽  
Chemical Effect ◽  
Nox Emissions ◽  
Nox Formation ◽  
Lean Blowout ◽  
Order Of Magnitude ◽  
Network Simulations ◽  
Fuel Mixtures

The concept of the cyclic periodical mixing combustion process (CPMCP) [1, 2] for the extension of the lean blowout limit had been implemented in an atmospheric experimental combustor for testing with both external perfect [3] and technical [4] premixing of reactants. It had been tested with natural gas and has now been tested with a mixture of 70%Vol of hydrogen and 30%Vol of natural gas (98% CH4) as fuel. With natural gas the NOx emissions are unaffected by the limited technical premixing quality, as long as the air preheat is in the design range of the premixers [4]. Then, for adiabatic flame temperatures of up to 1630 K NOx emissions are below 1 ppm(v) with CO emissions below 8 ppm(v) in the whole operation range of the test combustor (15% O2, dry). With the “70%Vol H2 – 30%Vol CH4” mixture the NOx emissions increase by nearly one order of magnitude. Then, NOx emissions below 7 ppm(v) (15% O2, dry) are achieved for adiabatic flame temperatures of up to 1600 K. They approach the 1 ppm(v) level only for flame temperatures below 1450 K. CO emissions are below 4 ppm(v). The reason for the increase of the NOx emissions is the higher reactivity of the mixture, which leads to earlier ignition in zones of still elevated unmixedness of reactants near the premixer-injector exits. This effect was investigated by chemical reactor network simulations, analyzing a pressure effect and an additional chemical effect of hydrogen combustion on NOx formation.

Emission Characteristics of a Premixed Cyclic-Periodical-Mixing Combustor Operated With Hydrogen-Natural Gas Fuel Mixtures

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
Jochen R. Brückner-Kalb ◽  
Michael Krösser ◽  
Christoph Hirsch ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Gas Turbines ◽  
Combustion Process ◽  
Chemical Reactor ◽  
Combustion Products ◽  
Chemical Effect ◽  
Nox Emissions ◽  
Nox Formation ◽  
Lean Blowout ◽  
Asme Turbo Expo

The concept of the cyclic periodical mixing combustion process (Kalb, and Sattelmayer, 2004, “Lean Blowout Limit and NOx-Production of a Premixed Sub-ppm-NOx Burner With Periodic Flue Gas Recirculation,” Proceedings of the ASME Turbo Expo 2004, Paper No. GT2004-53410; Kalb, and Sattelmayer, 2006, “Lean Blowout Limit and NOx-Production of a Premixed Sub-ppm-NOx Burner With Periodic Recirculation of Combustion Products,” ASME J. Eng. Gas Turbines Power, 128(2), pp. 247–254) for the extension of the lean blowout limit had been implemented in an atmospheric experimental combustor for testing with both external perfect (Brückner-Kalb, Hirsch, and Sattelmayer, 2006, “Operation Characteristics of a Premixed Sub-ppm NOx Burner With Periodical Recirculation of Combustion Products,” Proceedings of the ASME Turbo Expo 2006, Paper No. GT2006-90072) and technical (Brückner-Kalb, Napravnik, Hirsch, and Sattelmayer, 2007, “Development of a Fuel-Air Premixer for a Sub-ppm NOx Burner,” Proceedings of the ASME Turbo Expo 2007, Paper No. GT2007-27779) premixing of reactants. It had been tested with natural gas and has now been tested with a mixture of 70%vol of hydrogen and 30%vol of natural gas (98% CH4) as fuel. With natural gas the NOx emissions are unaffected by the limited technical premixing quality, as long as the air preheat is in the design range of the premixers (Brückner-Kalb, Napravnik, Hirsch, and Sattelmayer, 2007, “Development of a Fuel-Air Premixer for a Sub-ppm NOx Burner,” Proceedings of the ASME Turbo Expo 2007, Paper No. GT2007-27779). Then, for adiabatic flame temperatures of up to 1630 K NOx emissions are below 1 ppm(v) with CO emissions below 8 ppm(v) in the whole operation range of the test combustor (15% O2, dry). With the “70%volH2−30%volCH4” mixture the NOx emissions increase by nearly one order of magnitude. Then, NOx emissions below 7 ppm(v) (15% O2, dry) are achieved for adiabatic flame temperatures of up to 1600 K. They approach the 1 ppm(v) level only for flame temperatures below 1450 K. CO emissions are below 4 ppm(v). The reason for the increase in the NOx emissions is the higher reactivity of the mixture, which leads to earlier ignition in zones of still elevated unmixedness of reactants near the premixer-injector exits. This effect was investigated by chemical reactor network simulations analyzing a pressure effect and an additional chemical effect of hydrogen combustion on NOx formation.

Design of Inlet Conditions for High Pressure NOx Measurements in Lean Premixed Combustors

1995 ◽  
Author(s):  
Jon P. McDonald ◽  
Arthur M. Mellor
Keyword(s):  
Sensitivity Analysis ◽  
Natural Gas ◽  
Equivalence Ratio ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Nox Emissions ◽  
Oxides Of Nitrogen ◽  
Nox Formation ◽  
Lean Premixed ◽  
Inlet Conditions

Semi–empirical characteristic time models (CTMs) for NOx emissions index (EI) and lean blowoff are used in the design of an inlet condition matrix for measurement of NOxEI from a lean premixed combustor. Such models relate either NOxEI or the weak extinction limit to times representing relevant physical and chemical processes in the combustor. Lean premixed (LP) natural gas/air combustion is considered for the following conditions: inlet temperature, 300–800 K; combustor pressure, 1–30 atm; and equivalence ratio, 0.5–0.7. The NOx model is used to determine combinations of inlet conditions corresponding to greatest NOx sensitivity. A dependence of NOx emissions on pressure is included in the model. Emissions of oxides of nitrogen are found to he most sensitive to variations in inlet temperature and combustor pressure, in the 560–800 K and 20–30 atm ranges, respectively, while sensitivity to variations in equivalence ratio is substantial over the entire range considered. Thus it is found that operating conditions for high thermal efficiency in LP turbine combustors conflict with the goal of lowering NOx emissions, a result consistent with thermal NOx from conventional, diffusion flame combustors. A lean blowoff model is used to estimate the lowest equivalence ratio at which a flame can he held, as well as to determine whether a flame can be stabilised at the operating conditions suggested by the NOx sensitivity analysis. The results suggest a nominal lower limit on equivalence ratio of 0.4, and that a flame can be held for most of the combinations of inlet conditions suggested by the NOx sensitivity analysis. Autoignition of the fuel/air mixture is also considered in relation to the location and/or design of the premixing system. The current NOx CTM is applied to LP natural gas fired data from the literature. A model modification, thought to better represent the fluid mechanics relevant to LP NOx formation, is applied, and its implications discussed.

Ultra-Low Emission Hydrogen/Syngas Combustion With a 1.3 MW Injector Using a Micro-Mixing Lean-Premix System

2011 ◽  
Author(s):  
Brian Hollon ◽  
Erlendur Steinthorsson ◽  
Adel Mansour ◽  
Vincent McDonell ◽  
Howard Lee
Keyword(s):  
Carbon Dioxide ◽  
Natural Gas ◽  
Flame Temperature ◽  
Fuel Mixture ◽  
Full Scale ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Fuel Injector ◽  
Nitrogen Dilution ◽  
Fuel Mixtures

This paper discusses the development and testing of a full-scale micro-mixing lean-premix injector for hydrogen and syngas fuels that demonstrated ultra-low emissions and stable operation without flashback for high-hydrogen fuels at representative full-scale operating conditions. The injector was fabricated using Macrolamination technology, which is a process by which injectors are manufactured from bonded layers. The injector utilizes sixteen micro-mixing cups for effective and rapid mixing of fuel and air in a compact package. The full scale injector is rated at 1.3 MWth when operating on natural gas at 12.4 bar (180 psi) combustor pressure. The injector operated without flash back on fuel mixtures ranging from 100% natural gas to 100% hydrogen and emissions were shown to be insensitive to operating pressure. Ultra-low NOx emissions of 3 ppm were achieved at a flame temperature of 1750 K (2690 °F) using a fuel mixture containing 50% hydrogen and 50% natural gas by volume with 40% nitrogen dilution added to the fuel stream. NOx emissions of 1.5 ppm were demonstrated at a flame temperature over 1680 K (2564 °F) using the same fuel mixture with only 10% nitrogen dilution, and NOx emissions of 3.5 ppm were demonstrated at a flame temperature of 1730 K (2650 °F) with only 10% carbon dioxide dilution. Finally, using 100% hydrogen with 30% carbon dioxide dilution, 3.6 ppm NOx emissions were demonstrated at a flame temperature over 1600 K (2420 °F). Superior operability was achieved with the injector operating at temperatures below 1470 K (2186 °F) on a fuel mixture containing 87% hydrogen and 13% natural gas. The tests validated the micro-mixing fuel injector technology and the injectors show great promise for use in future gas turbine engines operating on hydrogen, syngas or other fuel mixtures of various compositions.

Experimental Assessment of the Emissions Benefits of a Ceramic Gas Turbine Combustor

1996 ◽  
Author(s):  
K. O. Smith ◽  
A. Fahme
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Flow Distribution ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Fuel Injector ◽  
Gas Turbine Combustor ◽  
Experimental Assessment ◽  
Industrial Gas Turbine ◽  
Combustor Liner

Three subscale, cylindrical combustors were rig tested on natural gas at typical industrial gas turbine operating conditions. The intent of the testing was to determine the effect of combustor liner cooling on NOx and CO emissions. In order of decreasing liner cooling, a metal louvre-cooled combustor, a metal effusion-cooled combustor, and a backside-cooled ceramic (CFCC) combustor were evaluated. The three combustors were tested using the same lean-premixed fuel injector. Testing showed that reduced liner cooling produced lower CO emissions as reaction quenching near the liner wall was reduced. A reduction in CO emissions allows a reoptimization of the combustor air flow distribution to yield lower NOx emissions.

Closed-Loop Combustion Control Using OH Radical Emissions

2000 ◽  
Author(s):  
Zhu (Julie) Meng ◽  
Robert J. Hoffa ◽  
Charles A. DeMilo ◽  
Todd T. Thamer
Keyword(s):  
Control System ◽  
Simulation Model ◽  
Gas Turbine ◽  
Closed Loop ◽  
System Simulation ◽  
Combustion Process ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Oh Radical ◽  
Emissions Control

The combustion process in gas-turbine engines produces emissions, especially nitrogen oxides (NOx) and carbon monoxide (CO), which change dramatically with combustor operating conditions. As part of this study, the application of active feedback control technologies to reduce thermal NOx emissions is modeled numerically and demonstrated experimentally. A new optical flame sensor, designed by Ametek Power & Industrial Products, has been successfully implemented as the feedback element in a proof-of-concept control system used to minimize NOx emissions. The sensor consists of a robust mechanical package, as well as electronics suitable for severe gas-turbine environments. Results from system rig tests correlate closely to theoretical predictions, as described in literature and produced by a control system simulation model. The control system simulation model predicts the efficacy of controlling engine operating characteristics based on chemical luminescence of the OH radical. The model consists of a fuel pump and metering device, a fuel-air mixing scheme, a combustion model, the new ultraviolet (UV) feedback flame sensor, and a simple gain block. The input reference to the proportional emissions control is the fuel-to-air equivalence ratio, which is empirically correlated to the desired low level of NOx emissions while satisfying other operating conditions, such as CO emissions and power. Results from the closed-loop emissions control simulation and rig tests were analyzed to determine the capability of the UV flame sensor to measure and control the combustion process in a gas-turbine engine. The response characteristics, overshoot percentage, rise time, settling time, accuracy, resolution, and repeatability are addressed.

CFD Analysis of Turbec T100 Combustor at Part Load by Varying Fuels

2015 ◽  
Author(s):  
Raffaela Calabria ◽  
Fabio Chiariello ◽  
Patrizio Massoli ◽  
Fabrizio Reale
Keyword(s):  
Natural Gas ◽  
Gas Turbines ◽  
Combustion Process ◽  
Calorific Value ◽  
Operating Conditions ◽  
Liquid Fuels ◽  
Cfd Analysis ◽  
Part Load ◽  
Gaseous Fuels ◽  
Wide Range

In recent years an increasing interest is focused on the study of micro gas turbines (MGT) behavior at part load by varying fuel, in order to determine their versatility. The interest in using MGT is related to the possibility of feeding with a wide range of fuels and to realize efficient cogenerative cycles by recovering heat from exhaust gases at higher temperatures. In this context, the studies on micro gas turbines are focused on the analysis of the machine versatility and flexibility, when operating conditions and fuels are significantly varied. In line of principle, in case of gaseous fuels with similar Wobbe Index no modifications to the combustion chamber should be required. The adoption of fuels whose properties differ greatly from those of design can require relevant modifications of the combustor, besides the proper adaptation of the feeding system. Thus, at low loads or low calorific value fuels, the combustor becomes a critical component of the entire MGT, as regards stability and emissions of the combustion process. Focus of the paper is a 3D CFD analysis of the combustor behavior of a Turbec T100P fueled at different loads and fuels. Differences between combustors designed for natural gas and liquid fuels are also highlighted. In case of natural gas, inlet combustor temperature and pressure were taken from experimental data; in case of different fuels, such data were inferred by using a thermodynamic model which takes into account rotating components behavior through operating maps of compressor and turbine. Specific aim of the work is to underline potentialities and critical issues of the combustor under study in case of adoption of fuels far from the design one and to suggest possible solutions.

Sign in / Sign up

Export Citation Format

Share Document