Water/Steam Injection for NOx Reduction in Process Burners

2018 ◽  
Author(s):  
Steve Londerville ◽  
Kevin Anderson ◽  
Charles Baukal ◽  
Wes Bussman
Keyword(s):  
Gas Turbines ◽  
Nox Reduction ◽  
Flame Temperature ◽  
Steam Injection ◽  
Water Steam ◽  
Flame Instability ◽  
Wide Range ◽  
Unburned Hydrocarbons ◽  
Thermal Nox ◽  
Flame Chemistry

Liquid water or steam injection is a technique that has been used for years to reduce NOx primarily by reducing the flame temperature which reduces thermal NOx. There is also evidence to suggest it reduces NOx by modifying the flame chemistry. While it is well proven for reducing NOx, there are some potential disadvantages including reduced thermal efficiency, flame instability, and increased emissions of other pollutants such as CO and unburned hydrocarbons. Water/steam injection has been used in a wide range of applications, particularly in boilers and gas turbines. Much less information is available on using this technique in process heaters which have some key differences compared to most combustors which include a highly varying fuel composition and natural draft to provide the combustion air. This paper will consider how water or steam may be injected into process burners including some predictive methods for determining NOx.

Analysis of the Mixing and Emission Characteristics in a Model Combustor

2018 ◽  
Author(s):  
Shan Li ◽  
Shanshan Zhang ◽  
Lingyun Hou ◽  
Zhuyin Ren
Keyword(s):  
Gas Turbines ◽  
Schmidt Number ◽  
Numerical Study ◽  
Flame Temperature ◽  
Scalar Dissipation ◽  
Mixing Process ◽  
Nox Formation ◽  
Turbulent Schmidt Number ◽  
Wide Range ◽  
Air Mixing

Modern gas turbines in power systems employ lean premixed combustion to lower flame temperature and thus achieve low NOx emissions. The fuel/air mixing process and its impacts on emissions are of paramount importance to combustor performance. In this study, the mixing process in a methane-fired model combustor was studied through an integrated experimental and numerical study. The experimental results show that at the dump location, the time-averaged fuel/air unmixedness is less than 10% over a wide range of testing conditions, demonstrating the good mixing performance of the specific premixer on the time-averaged level. A study of the effects of turbulent Schmidt number on the unmixedness prediction shows that for the complex flow field involved, it is challenging for Reynolds-Averaged Navier-Stokes (RANS) simulations with constant turbulent Schmidt number to accurately predict the mixing process throughout the combustor. Further analysis reveals that the production and scalar dissipation are the key physical processes controlling the fuel/air mixing. Finally, the NOx formation in this model combustor was analyzed and modelled through a flamelet-based approach, in which NOx formation is characterized through flame-front NOx and its post-flame formation rate obtained from one-dimensional laminar premixed flames. The effect of fuel/air unmixedness on NOx formation is accounted for through the presumed probability density functions (PDF) of mixture fraction. Results show that the measured NOx in the model combustor are bounded by the model predictions with the fuel/air unmixedness being 3% and 5% of the maximum unmixedness. In the context of RANS, the accuracy in NOx prediction depends on the unmixedness prediction which is sensitive to turbulent Schmidt number.

Humid Air NOx Reduction Effect on Liquid Fuel Combustion

2004 ◽  
Vol 126 (1) ◽  
pp. 69-74 ◽  
Author(s):  
A. G. Chen ◽  
Daniel J. Maloney ◽  
William H. Day
Keyword(s):  
Liquid Fuel ◽  
Nox Reduction ◽  
Flame Temperature ◽  
Substantial Reduction ◽  
Combustion Process ◽  
Pollutant Emissions ◽  
Humid Air ◽  
Wide Range ◽  
Reduction Of Nox ◽  
Reduction Effect

An experimental investigation was carried out at DOE NETL on the humid air combustion process using liquid fuel to determine the effects of humidity on pollutant emissions and flame stability. Tests were conducted at pressures of up to 100 psia (690 kPa), and a typical inlet air temperature of 860°F (733 K). The emissions and RMS pressures were documented for a relatively wide range of flame temperature from 2440-3090°F (1610–1970 K) with and without added humidity. The results show more than 90% reduction of NOx through 10% humidity addition to the compressed air compared with the dry case at the same flame temperature. The substantial reduction of NOx is due to a shift in the chemical mechanisms and cannot be explained by flame temperature reduction due to added moisture since the comparison was made for the same flame temperature.

System Evaluation and LBTU Fuel Combustion Studies for IGCC Power Generation

1995 ◽  
Vol 117 (4) ◽  
pp. 673-677 ◽  
Author(s):  
C. S. Cook ◽  
J. C. Corman ◽  
D. M. Todd
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Coal Gasification ◽  
Flame Temperature ◽  
Combined Cycle ◽  
Gas Turbine Combustor ◽  
Gas Cleaning ◽  
Wide Range ◽  
Cycle Systems ◽  
Combined Cycles

The integration of gas turbines and combined cycle systems with advances in coal gasification and gas stream cleanup systems will result in economically viable IGCC systems. Optimization of IGCC systems for both emission levels and cost of electricity is critical to achieving this goal. A technical issue is the ability to use a wide range of coal and petroleum-based fuel gases in conventional gas turbine combustor hardware. In order to characterize the acceptability of these syngases for gas turbines, combustion studies were conducted with simulated coal gases using full-scale advanced gas turbine (7F) combustor components. It was found that NOx emissions could be correlated as a simple function of stoichiometric flame temperature for a wide range of heating values while CO emissions were shown to depend primarily on the H2 content of the fuel below heating values of 130 Btu/scf (5125 kJ/NM3) and for H2/CO ratios less than unity. The test program further demonstrated the capability of advanced can-annular combustion systems to burn fuels from air-blown gasifiers with fuel lower heating values as low as 90 Btu/scf (3548 kJ/NM3) at 2300°F (1260°C) firing temperature. In support of ongoing economic studies, numerous IGCC system evaluations have been conducted incorporating a majority of the commercial or near-commercial coal gasification systems coupled with “F” series gas turbine combined cycles. Both oxygen and air-blown configurations have been studied, in some cases with high and low-temperature gas cleaning systems. It has been shown that system studies must start with the characteristics and limitations of the gas turbine if output and operating economics are to be optimized throughout the range of ambient operating temperature and load variation.

Study of a Rich/Lean Staged Combustion Concept for Hydrogen at Gas Turbine Relevant Conditions

2013 ◽  
Author(s):  
Felipe Bolaños ◽  
Dieter Winkler ◽  
Felipe Piringer ◽  
Timothy Griffin ◽  
Rolf Bombach ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Carbon Capture ◽  
Flame Temperature ◽  
Nox Emissions ◽  
Hydrogen Fuel ◽  
Auto Ignition ◽  
Wide Range ◽  
The Rich

The combustion of hydrogen-rich fuels (> 80 % vol. H2), relevant for gas turbine cycles with “pre-combustion” carbon capture, creates great challenges in the application of standard lean premix combustion technology. The significant higher flame speed and drastically reduced auto-ignition delay time of hydrogen compared to those of natural gas, which is normally burned in gas turbines, increase the risk of higher NOX emissions and material damage due to flashback. Combustion concepts for gas turbines operating on hydrogen fuel need to be adapted to assure safe and low-emission combustion. A rich/lean (R/L) combustion concept with integrated heat transfer that addresses the challenges of hydrogen combustion has been investigated. A sub-scale, staged burner with full optical access has been designed and tested at gas turbine relevant conditions (flame temperature of 1750 K, preheat temperature of 400 °C and a pressure of 8 bar). Results of the burner tests have confirmed the capability of the rich/lean staged concept to reduce the NOx emissions for undiluted hydrogen fuel. The NOx emissions were reduced from 165 ppm measured without staging (fuel pre-conversion) to 23 ppm for an R/L design having a fuel-rich hydrogen pre-conversion of 50 % at a constant power of 8.7 kW. In the realized R/L concept the products of the first rich stage, which is ignited by a Pt/Pd catalyst (under a laminar flow, Re ≈ 1900) are combusted in a diffusion-flame-like lean stage (turbulent flow Re ≈ 18500) without any flashback risk. The optical accessibility of the reactor has allowed insight into the combustion processes of both stages. Applying OH-LIF and OH*-chemiluminescence optical techniques, it was shown that mainly homogeneous reactions at rich conditions take place in the first stage, questioning the importance of a catalyst in the system, and opening a wide range of optimization possibilities. The promising results obtained in this study suggest that such a rich/lean staged burner with integrated heat transfer could help to develop a new generation of gas turbine burners for safe and clean combustion of H2-rich fuels.

One-Dimensional Model to Quantify NOx Reduction in Gas Turbines Using EGR

1998 ◽  
Author(s):  
K. K. Botros ◽  
M. J. de Boer ◽  
G. Kibrya
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Nox Reduction ◽  
Simulation Software ◽  
Specific Work ◽  
Dimensional Model ◽  
Nox Formation ◽  
One Dimensional ◽  
Thermal Nox

A one dimensional model based on fundamental principles of gas turbine thermodynamics and combustion processes was constructed to quantify the principle of exhaust gas recirculation (EGR) for NOx reduction. The model utilizes the commercial process simulation software ASPEN PLUS®. Employing a set of 8 reactions including the Zeldovich mechanism, the model predicted thermal NOx formation as function of amount of recirculation and the degree of recirculate cooling. Results show that addition of sufficient quantities of uncooled recirculate to the inlet air (i.e. EGR>∼4%) could significantly decrease NOx emissions but at a cost of lower thermal efficiency and specific work. Cooling the recirculate also reduced NOx at lower quantities of recirculation. This has also the benefit of decreasing losses in the thermal efficiency and in the specific work output. Comparison of a ‘rubber’ and ‘non-rubber’ gas turbine confirmed that residence time is one important factor in NOx formation.

Low Load Operation Range Extension by Autothermal On-Board Syngas Generation

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Max H. Baumgärtner ◽  
Thomas Sattelmayer
Keyword(s):  
Gas Turbines ◽  
Power Plants ◽  
Renewable Energy Sources ◽  
Flame Temperature ◽  
Combined Cycle ◽  
Sudden Increase ◽  
Gaseous Emissions ◽  
Fuel Processor ◽  
Burn Out ◽  
Unburned Hydrocarbons

The increasing amount of volatile renewable energy sources drives the necessity of flexible conventional power plants to compensate for fluctuations of the power supply. Gas turbines in a combined cycle power plant (CCPP) adjust the power output quickly but a sudden increase of CO and unburned hydrocarbons emissions limits their turn-down ratio. To extend the turn-down ratio, part of the fuel can be processed to syngas, which exerts a higher reactivity. An autothermal on-board syngas generator in combination with two different burner concepts for natural gas (NG) and syngas mixtures is presented in this study. A mixture of NG, water vapor, and air reacts catalytically in an autothermal reactor test rig to form syngas. At atmospheric pressure, the fuel processor generates syngas with a hydrogen content of −30 vol % and a temperature of 800 K within a residence time of 200 ms. One concept for the combustion of NG and syngas mixtures comprises a generic swirl stage with a central lance injector for the syngas. The second concept includes a central swirl stage with an outer ring of jets. The combustion is analyzed for both concepts by OH*-chemiluminescence, lean blow out (LBO) limit, and gaseous emissions. The central lance concept with syngas injection exhibits an LBO adiabatic flame temperature that is 150 K lower than in premixed NG operation. For the second concept, an extension of almost 200 K with low CO emission levels can be reached. This study shows that autothermal on-board syngas generation is feasible and efficient in terms of turn-down ratio extension and CO burn-out.

Technology Update on Gas Turbine Dual Fuel, Dry Low Emission Combustion Systems

2003 ◽  
Author(s):  
Petter Egil Ro̸kke ◽  
Johan E. Hustad ◽  
Nils A. Ro̸kke ◽  
Ole Birger Svendsgaard
Keyword(s):  
Gas Turbine ◽  
Flame Temperature ◽  
Steam Injection ◽  
Dual Fuel ◽  
Combustion System ◽  
Single Digit ◽  
Water Steam ◽  
Marine Propulsion ◽  
Low Emission ◽  
Combustion Systems

A challenging issue in the gas turbine industry is to develop a practical dual fuel (DF), dry low emission (DLE) combustion system. Especially for the onshore-based power generation systems, and liquid DLE for aeroderivative engines used for marine propulsion. A novel mid-size (3MW) gas turbine is being developed mainly targeted for marine propulsion, where a dual fuel DLE combustion system aiming at single digit NOx emission figures has been explored. As a part of this development, the present technology available from different gas turbine manufacturers has been surveyed. Status of the different techniques applied in dual fuel DLE combustors today and their achievements are presented, including the available information on fuel injectors, cooling schemes, combustion air distribution, noise control and combustor performance. The techniques utilized and explained are such as flame temperature control (water/steam injection), staged combustion, lean premixing and lean prevaporized premixing, rich-quench-lean-burning (RQLB) and catalytic combustion. These are also documented for the different concepts commercially available, describing both advantages and drawbacks. Conclusions are made towards the dominating trends for the different parameters mentioned above, and how they affect the final combustor design. A survey of the dominating parameters for low emission combustion systems is presented.

A Combustion Test Facility for Testing Low NOx Combustion Systems

2002 ◽  
Author(s):  
Difei Wang ◽  
Vivek Sahai ◽  
Dah Yu Cheng
Keyword(s):  
Atmospheric Pressure ◽  
Gas Turbines ◽  
Nox Reduction ◽  
Steam Injection ◽  
Test System ◽  
Combustion Stability ◽  
Test Facility ◽  
Inlet Temperature ◽  
Computer Data ◽  
Combustion Systems

Cheng Power Systems has designed and built an atmospheric pressure combustion test facility for gas turbines, which has the capability of testing the full size combustion systems of large gas turbines at atmospheric pressure while maintaining the adiabatic flame temperature at pressurized conditions. The uniqueness of the test facility is the method of preheating the air to the compressor discharge temperature of a gas turbine at high-pressure ratios using the combustion exhaust gas and a compact air-to-air heat exchanger. The exhaust dampers and dilution airflows control the preheated-air temperature. The other characteristic of the test facility is the competence of testing NOx reduction combustion systems using steam or inert gas. The facility has the capability to perform steam injection experiments to examine the combustion stability with massive steam injection rates of up to 20% of air mass flow rate. The test process is fully automated with computer data acquisition and digital control. Combustion systems such as GE Frame 5P, 6B, 7EA, and Westinghouse 501D5A have been tested. With Cheng Power’s unique NOx reduction system (CLN™ - Cheng Low NOx System), less than 5 ppm NOx and very low level of CO were obtained for these combustion systems without hardware modification. The facility is also capable of testing Dry-Low-NOx (DLN) combustion systems. The test system is also assisted by a commercial computer program (Star-CD) to estimate the pressurization effect for extrapolating the test results. The pressure dependence can be simulated with the unique combustion geometry, type of fuel, and onset of turbine inlet temperature, respectively. The results depict the detail of the flame structure under various combustion chamber design characteristics. The model pressurization results correlate well with our experimental results as well as results in the literature.

Humid Air NOx Reduction Effect on Liquid Fuel Combustion

2002 ◽  
Author(s):  
Alexander G. Chen ◽  
Daniel J. Maloney ◽  
William H. Day
Keyword(s):  
Liquid Fuel ◽  
Nox Reduction ◽  
Flame Temperature ◽  
Substantial Reduction ◽  
Combustion Process ◽  
Pollutant Emissions ◽  
Humid Air ◽  
Wide Range ◽  
Reduction Of Nox ◽  
Reduction Effect

An experimental investigation was carried out at DOE NETL on the humid air combustion process using liquid fuel to determine the effects of humidity on pollutant emissions and flame stability. Tests were conducted at pressures of up to 100 psia (690 kPa), and a typical inlet air temperature of 860 °F (733 K). The emissions and RMS pressures were documented for a relatively wide range of flame temperature from 2440–3090 °F (1610 − 1970 K) with and without added humidity. The results show more than 90 percent reduction of NOx through 10 percent humidity addition to the compressed air compared with the dry case at the same flame temperature. The substantial reduction of NOx is due to a shift in the chemical mechanisms and cannot be explained by flame temperature reduction due to added moisture since the comparison was made for the same flame temperature.

scholarly journals Semi–Empirical Correlation of NOx Emissions From Combustion Turbines With Water/Steam Injection

1995 ◽  
Author(s):  
Donald M. Newburry ◽  
Arthur M. Mellor
Keyword(s):  
Standard Deviation ◽  
Formation Rate ◽  
Flame Temperature ◽  
Steam Injection ◽  
Measured Data ◽  
Fuel Oil ◽  
Nox Emissions ◽  
Time Model ◽  
Water Steam ◽  
Semi Empirical

Inert (water or steam) injection is commonly used to reduce NOx emissions in stationary gas turbine combustors, both lean premixed when oil–fired and conventional. Thus, having an accurate phenomenological model to predict these reductions could be useful in both design and implementation for low emissions. In this work, the semi–empirical characteristic time model (CTM), which has been validated for thermal NOx emissions from conventional, diffusion flame combustors, is modified to account for inert injection effects. Measured NOx data from two heavy–duty, utility combustion turbines operating on natural gas and fuel oil #2, both dry and with water or steam injection, are correlated. Inert injection is modeled as thermal, and two limiting cases are proposed which successfully bound the measured data. An empirically selected effective inert injection flame temperature was substituted for the stoichiometric flame temperature used to estimate the thermal NO formation rate in the CTM. This procedure correlated all of the measured data from both combustors for both fuels with a standard deviation of 1.02 g NO2/kg fuel. The high standard deviation results from systematic trends in the dry data for one combustor which propagate through the lower NOx values of the inert injection data. Removing these trends empirically improves the combined correlation to a standard deviation of 0.28 g/kg (approximately 3.2 ppmvd at 15% O2).

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