A Gas Turbine Innovative System for Managing Fuel With Different and Variable-Over-Time Wobbe Indexes

2008 ◽  
Author(s):  
Annalisa Forte ◽  
Antonio Asti ◽  
Simone Bei ◽  
Massimo Betti ◽  
Michele D’Ercole ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Natural Gas ◽  
Gas Turbine ◽  
Normal Operation ◽  
Fuel Composition ◽  
Market Demand ◽  
Combustion System ◽  
Innovative System ◽  
Wobbe Index ◽  
Over Time

Due to the substantial increase in sources of gas, natural gas interchangeability is a key subject in the industry today. The extensive pipeline network means that natural gas arriving at appliances, boilers, burners and power plant turbines could come from anywhere. Fuel compositions vary from one source to another. Moreover, most recently, Liquefied Natural Gas has emerged as a major source and the composition of gas derived from LNG substantially differs from the natural gas one. In Dry Low NOx (DLN) systems, those changes in fuel composition can cause dangerous increase in combustion dynamics and can also affect the NOx emissions of the machine. Therefore, in order to meet the growing market demand for gas turbine combustors able to tolerate significant alterations in fuel composition, a system capable of burning gases with differing and variable over time Wobbe Indexes was developed. This innovative system does not involve any combustion hardware modifications. It allows the use of a premixed combustion system that complies with emissions, reliability, and safety, even when burning a fuel that is distinctly different from the original design gas. In particular, the system was developed in order to meet the requirements of a customer for burning any continuously and slowly varying mixture of two fuel gases, whose Wobbe Indexes difference is up to 25%. Since the burner is designed for 100% of the gas with lower Wobbe Index, the gas that has a higher WI needs to be heated, in order to achieve a target Modified Wobbe Index; the same happens for any mixture of the two gases. The system is based on a closed loop control on the Modified Wobbe Index of the fuel. Two turbine control gas chromatographs, located upstream the combustor inlet, measure the gas characteristics (LHV, specific gravity and temperature) and calculates the MWI. If it is different from the target one, it is corrected by modifying the temperature set point of a heat exchanger. The hardware is completed with one more plant gas chromatograph, located upstream the heat exchanger, for evaluating the fast and complete switch from one gas to the other one. In addition to the normal operation, that is with the 100% Lower Wobbe Index gas (L) or 100% Higher Wobbe Index gas (H) or any continuously and slowly varying mixture of these two gases, the system allows both the black and the normal start, the complete switch back and forth between 100% L gas and 100% H gas and load sheds and rejection. Moreover the two gases can be burned in diffusion combustion mode, as available, without requiring any increase in temperature, with no limitation from firing to full load. The capability of the system to adjust to all of the previously described events, potentially dangerous and damaging for the Gas Turbine combustion system, makes it suitable for applications that burn different lots of gases coming from different LNG sources, since it allows the turbine to accommodate the differences in Wobbe Index, due to various gas lots on a pipe line.

scholarly journals Ongoing Development of a Gas Turbine Combustion System for Gaseous Fuels With a Wide Range of Wobbe Index Values

1988 ◽  
Author(s):  
V. M. Sood
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Pressure Oscillation ◽  
Injection System ◽  
Combustion System ◽  
Fuel Injector ◽  
Pressure Drops ◽  
Gaseous Fuels ◽  
Wide Range ◽  
Wobbe Index

Development of a combustion system at the author’s Company was carried out at atmospheric pressure to achieve successful operation of a 5500-hp (Type H) gas turbine on gaseous fuels covering a wide range of Wobbe Index (WI) values from 48.04 MJ/nm3 (1220 Btu/scf) for natural gas to 18.90 MJ/nm3 (480 Btu/scf) for natural gas and carbon dioxide mixtures. Mixtures with the latter composition have direct applications for gas turbine engines burning fuels derived from sanitary landfills and liquid sewage. Wide-range operational capability offers the flexibility to fire gas turbines with either pipeline quality natural gas or medium-heating-value fuel, depending on availability. For such applications, if a fuel injector is designed to operate satisfactorily on natural gas fuel, it will have unacceptably high pressure drops when operating on fuels with WI values towards the lower end of the range. On the other hand, if the fuel injector is designed to operate properly on fuels with WI values on the lower end of the range, it will have unacceptably low pressure drops when operating on fuels with WI values towards the higher end of the range, which causes combustion-driven pressure oscillation feedback into the fuel-injection system. This feedback usually increases the amplitude of combustion-driven pressure oscillation and can cause significant damage to the gas turbine in a relatively short time. This paper describes the design and development work carried out to resolve these problems.

Fuel Flexibility Influences on Premixed Combustor Blowout, Flashback, Autoignition and Instability

2006 ◽  
Author(s):  
Tim Lieuwen ◽  
Vince McDonell ◽  
Eric Petersen ◽  
Domenic Santavicca
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Dynamic Stability ◽  
Current Understanding ◽  
Fuel Composition ◽  
Fuel Flexibility ◽  
Lean Premixed ◽  
Gas Fuel ◽  
The Impact ◽  
Underlying Processes

This paper addresses the impact of fuel composition on the operability of lean premixed gas turbine combustors. This is an issue of current importance due to variability in the composition of natural gas fuel supplies and interest in the use of syngas fuels. Of particular concern is the effect of fuel composition on combustor blowout, flashback, dynamic stability, and autoignition. This paper reviews available results and current understanding of the effects of fuel composition on the operability of lean premixed combustors. It summarizes the underlying processes that must be considered when evaluating how a given combustor’s operability will be affected as fuel composition is varied.

Impact of Ethane, Propane, and Diluent Content in Natural Gas on the Performance of a Commercial Microturbine Generator

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Richard L. Hack ◽  
Vincent G. McDonell
Keyword(s):  
Power Generation ◽  
Natural Gas ◽  
Gas Turbine ◽  
Fuel Composition ◽  
Nox Emissions ◽  
Heating Value ◽  
Designed Experiment ◽  
Methane Number ◽  
The Impact ◽  
Lean Conditions

The impact of fuel composition on the performance of power generation devices is gaining interest as the desire to diversify fuel supplies increases. In the present study, measurements of combustion performance were conducted on a commercial natural gas-fired 60kW gas turbine as a function of fuel composition. A statistically designed experiment was carried out and exhaust emissions were obtained for significant amounts of ethane and propane. In addition, a limited study of the effect of inerts was conducted. The results show that emissions of NOx, CO, and NOx∕NO are not well correlated with common descriptions of the fuel, such as higher heating value or methane number. The results and trends indicate that the presence of higher hydrocarbons in the fuel leads to appreciably higher NOx emissions for both test devices operating under similar lean conditions, while having less impact on CO emissions.

The Performance Improvement of a 70kWe Natural Gas CHP System

2008 ◽  
Author(s):  
Lin Fu ◽  
Xiling Zhao ◽  
Shigang Zhang ◽  
Yi Jiang ◽  
Hui Li ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Natural Gas ◽  
Heat Pump ◽  
Flue Gas ◽  
Utilization Efficiency ◽  
Outlet Temperature ◽  
Absorption Heat Pump ◽  
Gas Engine ◽  
Innovative System ◽  
Chp System

It is well known that combined heating and power (CHP) generation permits the energy of the fuel to be more efficiently than electric and thermal separate generation. The paper deals with natural gas CHP system with a 70kWe gas-powered internal combustion engine (ICE), which has been set up at the Tsinghua University energy-saving building, in Beijing, China. The system is composed of an ICE, a flue gas heat exchanger and other heat exchangers. The conventional system’s characteristics is that the gas engine generates power on-site, and the exhaust of the gas engine is recovered by a high temperature flue gas-water heat exchanger, and the jacket water heat is recovered by a water-water heat exchanger to supply heat for district heating system. In order to improve the system’s performance, an innovative system with absorption heat pump is adopted. The exhaust of the gas engine drives an absorption heat pump to recover the flue gas sensible heat and further recover the latent heat, so the outlet temperature of the exhaust could be lowered to 50°C. In this paper, the electrical and thermal performance of the innovative system were tested and compared with conventional cogeneration systems. The test and comparison results show that the innovative CHP system could increase the heat utilization efficiency 10% in winter. All the results provide important insight into CHP performance characteristics and could be valuable references for CHP system’s improvements.

Reactor Network Modeling of Stability and Emissions of Hydrogen and Natural Gas Blends for a Piloted Gas Turbine Combustor

2020 ◽  
Author(s):  
Candy Hernandez ◽  
Vincent McDonell
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Chemical Reactor ◽  
Experimental Results ◽  
Fuel Composition ◽  
Gas Turbine Combustor ◽  
Flammability Limits ◽  
Lean Premixed ◽  
Carbon Molecules

Abstract Lean-premixed (LPM) gas turbines have been developed for stationary power generation in efforts to reduce emissions due to strict air quality standards. Lean-premixed operation is beneficial as it reduces combustor temperatures, thus decreasing NOx formation and unburned hydrocarbons. However, tradeoffs occur between system performance and turbine emissions. Efforts to minimize tradeoffs between stability and emissions include the addition of hydrogen to natural gas, a common fuel used in stationary gas turbines. The addition of hydrogen is promising for both increasing combustor stability and further reducing emissions because of its wide flammability limits allowing for lower temperature operation, and lack of carbon molecules. Other efforts to increase gas turbine stability include the usage of a non-lean pilot flame to assist in stabilizing the main flame. By varying fuel composition for both the main and piloted flows of a gas turbine combustor, the effect of hydrogen addition on performance and emissions can be systematically evaluated. In the present work, computational fluid dynamics (CFD) and chemical reactor networks (CRN) are created to evaluate stability (LBO) and emissions of a gas turbine combustor by utilizing fuel and flow rate conditions from former hydrogen and natural gas experimental results. With CFD and CRN analysis, the optimization of parameters between fuel composition and main/pilot flow splits can provide feedback for minimizing pollutants while increasing stability limits. The results from both the gas turbine model and former experimental results can guide future gas turbine operation and design.

Full Scale Testing of a Low Swirl Fuel Injector Concept for Ultra-Low NOx Gas Turbine Combustion Systems

2006 ◽  
Author(s):  
Waseem Nazeer ◽  
Kenneth Smith ◽  
Patrick Sheppard ◽  
Robert Cheng ◽  
David Littlejohn
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Flame Temperature ◽  
Pressure Oscillation ◽  
Test Results ◽  
Combustion System ◽  
Fuel Injector ◽  
Annular Combustor ◽  
Swirl Injector ◽  
Gas Turbine Combustion

The continued development of a low swirl injector for ultra-low NOx gas turbine applications is described. An injector prototype for natural gas operation has been designed, fabricated and tested. The target application is an annular gas turbine combustion system requiring twelve injectors. High pressure rig test results for a single injector prototype are presented. On natural gas, ultra-low NOx emissions were achieved along with low CO. A turndown of approximately 100°F in flame temperature was possible before CO emissions increased significantly. Subsequently, a set of injectors was evaluated at atmospheric pressure using a production annular combustor. Rig testing again demonstrated the ultra-low NOx capability of the injectors on natural gas. An engine test of the injectors will be required to establish the transient performance of the combustion system and to assess any combustor pressure oscillation issues.

Extension of Fuel Flexibility in the Siemens Dry Low Emissions SGT-300-1S to Cover a Wobbe Index Range of 15 to 49 MJ/m3

2012 ◽  
Author(s):  
Kexin Liu ◽  
Varkey Alexander ◽  
Victoria Sanderson ◽  
Ghenadie Bulat
Keyword(s):  
Natural Gas ◽  
Nox Reduction ◽  
Operating Conditions ◽  
Combustion System ◽  
Combustion Dynamics ◽  
Fuel Supply ◽  
Supply Pressure ◽  
Fuel Flexibility ◽  
Wobbe Index ◽  
Standard Production

The extension of gas fuel flexibility in the Siemens SGT-300 single shaft (SGT-300-1S) is reported in this paper. A successful development programme has increased the capability of the Siemens Industrial Turbomachinery, Lincoln (SITL) dry low emissions (DLE) burner configuration to a fuel range covering a Wobbe Index (WI) from 15 to 49 MJ/m3. The standard SGT-300-1S SITL DLE combustion hardware allowed for gas and liquid fuels within a specified range typically associated with natural gas and diesel, respectively. Field operation of the standard production SGT-300-1S has confirmed the reliable operation with an extension to the fuels range to include processed land fill gas (PLG) from 32 to 49 MJ/m3. The further extension of the fuel range for the SGT-300-1S SITL DLE combustion system was achieved through high pressure testing of a single combustion system at engine operating conditions. The rig facility allowed for the actual fuel type to be tested using a mixing plant. The variations in fuel heating value were achieved by blending natural gas with diluent CO2 and/or N2. Various diagnostics were used to assess the performance of the combustion system including measurement of combustion dynamics, temperature, fuel supply pressure and emissions of NOx, CO and unburned hydrocarbon (UHC). The results of the testing showed that the standard production burner can operate for a fuel with WI as low as 23 MJ/m3 which corresponds to 35% CO2 (in volume) in the fuel. This range can be extended to 15 MJ/m3 (54.5% CO2 in the fuel) with only minor modification, to control losses through the burner and to maintain similar fuel injection characteristics. The SITL DLE combustion system is able to cover a WI range of 15 to 49 MJ/m3 in two configurations. The results of testing showed a lowering in WI, from diluting with CO2 and/or N2, a benefit in NOx reduction is observed. This decrease in WI may lead to an increased requirement in fuel supply pressure.

Design and Testing of an Ultra-Low NOx Gas Turbine Combustor

1986 ◽  
Author(s):  
Kenneth O. Smith ◽  
Leonard C. Angello ◽  
F. Richard Kurzynske
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Catalytic Reduction ◽  
Water Injection ◽  
Nox Emissions ◽  
Combustion System ◽  
Gas Turbine Combustor ◽  
Program Goal ◽  
Primary Zone ◽  
Design And Testing

The design and initial rig testing of an ultra-low NOx gas turbine combustor primary zone are described. A lean premixed, swirl-stabilized combustor was evaluated over a range of pressures up to 10.7 × 105 Pa (10.6 atm) using natural gas. The program goal of reducing NOx emissions to 10 ppm (at 15% O2) with coincident low CO emissions was achieved at all combustor pressure levels. Appropriate combustor loading for ultra-low NOx operation was determined through emissions sampling within the primary zone. The work described represents a first step in developing an advanced gas turbine combustion system that can yield ultra-low NOx levels without the need for water injection and selective catalytic reduction.

Gas Turbine Gas Fuel Composition Performance Correction Using Wobbe Index

2010 ◽  
Author(s):  
Bryan Li ◽  
Mike J. Gross ◽  
Thomas P. Schmitt
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Performance Test ◽  
Test Accuracy ◽  
Fuel Composition ◽  
Gas Composition ◽  
Fuel Gas ◽  
Heating Value ◽  
Performance Effects ◽  
Wobbe Index

Gas turbine thermal performance is dependent on many external conditions, including fuel gas composition. Variations in composition cause changes in output and heat consumption during operation. Measured performance must be corrected to specified reference conditions prior to comparison against performance specifications. The fuel composition is one such condition for which performance corrections are required. The methodology of fuel composition corrections can take various forms. One current method of correction commonly used is to characterize fuel composition effects as a function of heating value and hydrogen-to-carbon ratio. This method has been used in the past within a limited range of fuel composition variation around the expected composition, yielding relatively small correction factors on the order of +/− 0.1%. Industry trends suggest that gas turbines will continue to be exposed to broader ranges of gas constituents, and the corresponding performance effects will be much larger. For example, liquefied natural gas, synthesized low BTU fuel, and bio fuels are becoming more common, with associated performance effects of +/− 0.5% or greater. As a result of these trends, performance test results will bear a greater dependency on fuel composition corrections. Hence, a more comprehensive correction methodology is required to encompass a broader range of fuel constituents encountered. Combustion system behavior, specifically emissions and flame stability, is also influenced by variations in fuel gas composition. The power generation industry uses Wobbe Index as an indicator of fuel composition. Wobbe Index relates the heating value of the fuel to its density. High variations in Wobbe Index can cause operability issues including combustion dynamics and increased emissions. A new method for performance corrections using Wobbe Index as the correlating fuel parameter has been considered. Analytical studies have been completed with the aid of thermodynamic models to identify the extent to which the Wobbe Index can be used to correlate the response of the gas turbine performance parameters to fuel gas composition. Results of the study presented in this paper suggest that improved performance test accuracy can be achieved by using Wobbe Index as a performance correction parameter, instead of the aforementioned conventional fuel characteristics. Furthermore, a relationship between this method’s accuracy and CO2 content of fuel is established such that an additional correction yields results with even better accuracy. This proposed method remains compliant with intent of internationally accepted test codes such as ASME PTC-22, ASME PTC-46, and ISO 2314.

Estimating Recoverable Performance Degradation Rates and Optimizing Maintenance Scheduling

2018 ◽  
Author(s):  
Cody W. Allen ◽  
Chad M. Holcomb ◽  
Mauricio de Oliveira
Keyword(s):  
Gas Turbine ◽  
Estimation Method ◽  
Noisy Data ◽  
Maintenance Scheduling ◽  
Normal Operation ◽  
Economic Optimization ◽  
Rate Estimation ◽  
Maintenance Schedule ◽  
Degradation Rates ◽  
Over Time

Many of the components on a gas turbine are subject to fouling and degradation over time due to debris buildup. For example, axial compressors are susceptible to degradation as a result of debris buildup on compressor blades. Similarly, air cooled lube oil heat exchangers incur degradation as a result of debris buildup in the cooling air passageways. In this paper, we develop a method for estimating the degradation rate of a given gas turbine component that experiences recoverable degradation due to normal operation over time. We then establish an economic maintenance scheduling model which utilizes the derived rate and user input economic factors to provide a locally optimal maintenance schedule with minimized operator costs. The rate estimation method makes use of statistical methods combined with historical data to give an algorithm with which a performance loss rate can be extracted from noisy data measurements. The economic maintenance schedule is then derived by minimizing the cost model in user specified intervals and the final schedule results as a combination of the locally optimized schedules. The goal of the combination of algorithms is to maximize component output and efficiency, while minimizing maintenance costs. The rate estimation method is validated by simulation where the underlying noisy data measurements come from a known probability distribution. Then, an example schedule optimization is provided to validate the economic optimization model and show the efficacy of the combined methods.

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