scholarly journals Combustion and Oxidation Kinetics of Alternative Gas Turbines Fuels

2014 ◽  
Author(s):  
Pierre-Alexandre Glaude ◽  
Baptiste Sirjean ◽  
René Fournet ◽  
Roda Bounaceur ◽  
Matthieu Vierling ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Ignition Temperature ◽  
Alternative Fuels ◽  
Flame Temperature ◽  
Liquid Fuels ◽  
Heavy Oils ◽  
Process Gas ◽  
Auto Ignition

Heavy duty gas turbines are very flexible combustion tools that accommodate a wide variety of gaseous and liquid fuels ranging from natural gas to heavy oils, including syngas, LPG, petrochemical streams (propene, butane…), hydrogen-rich refinery by-products; naphtha; ethanol, biodiesel, aromatic gasoline and gasoil, etc. The contemporaneous quest for an increasing panel of primary energies leads manufacturers and operators to explore an ever larger segment of unconventional power generation fuels. In this moving context, there is a need to fully characterize the combustion features of these novel fuels in the specific pressure, temperature and equivalence ratio conditions of gas turbine combustors using e.g. methane as reference molecule and to cover the safety aspects of their utilization. A numerical investigation of the combustion of a representative cluster of alternative fuels has been performed in the gas phase, namely two natural gas fuels of different compositions, including some ethane, a process gas with a high content of butene, oxygenated compounds including methanol, ethanol, and DME (dimethyl ether). Sub-mechanisms have specifically been developed to include the reactions of C4 species. Major combustion parameters, such as auto-ignition temperature (AIT), ignition delay times (AID), laminar burning velocities of premixed flames, adiabatic flame temperatures, and CO and NOx emissions have then been investigated. Finally, the data have been compared with those calculated for methane flames. These simulations show that the behaviors of alternative fuels markedly differ from that of conventional ones. Especially, DME and the process gases appear to be highly reactive with significant impacts on the auto-ignition temperature and flame speed data, which justifies burner design studies within premixed combustion schemes and proper safety considerations. The behaviors of alcohols (especially methanol) display some commonalities with those of conventional fuels. In contrast, DME and process gas fuels develop substantially different flame temperature and NOx generation rates than methane. Resorting to lean premix conditions is likely to achieve lower NOx emission performances. This review of gas turbine fuels shows for instance that the use of methanol as a gas turbine fuel is possible with very limited combustor modifications.

DME as a Potential Alternative Fuel for Gas Turbines: A Numerical Approach to Combustion and Oxidation Kinetics

2011 ◽  
Author(s):  
Pierre A. Glaude ◽  
Rene´ Fournet ◽  
Roda Bounaceur ◽  
Michel Molie`re
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Heat Input ◽  
Ignition Delay ◽  
Gas Turbines ◽  
Ignition Temperature ◽  
Alternative Fuels ◽  
Ignition Delay Times ◽  
Auto Ignition ◽  
Delay Times

Many investigations are currently carried out in order to reduce CO2 emissions in power generation. Among alternative fuels to natural gas and gasoil in gas turbine applications, dimethyl ether (DME; formula: CH3-O-CH3) represents a possible candidate in the next years. This chemical compound can be produced from natural gas or coal/biomass gasification. DME is a good substitute for gasoil in diesel engine. Its Lower Heating Value is close to that of ethanol but it offers some advantages compared to alcohols in terms of stability and miscibility with hydrocarbons. While numerous studies have been devoted to the combustion of DME in diesel engines, results are scarce as far as boilers and gas turbines are concerned. Some safety aspects must be addressed before feeding a combustion device with DME because of its low flash point (as low as −83°C), its low auto-ignition temperature and large domain of explosivity in air. As far as emissions are concerned, the existing literature shows that in non premixed flames, DME produces less NOx than ethane taken as parent molecular structure, based on an equivalent heat input to the burner. During a field test performed in a gas turbine, a change-over from methane to DME led to a higher fuel nozzle temperature but to a lower exhaust gas temperature. NOx emissions decreased over the whole range of heat input studied but a dramatic increase of CO emissions was observed. This work aims to study the combustion behavior of DME in gas turbine conditions with the help of a detailed kinetic modeling. Several important combustion parameters, such as the auto-ignition temperature (AIT), ignition delay times, laminar burning velocities of premixed flames, adiabatic flame temperatures, and the formation of pollutants like CO and NOx have been investigated. These data have been compared with those calculated in the case of methane combustion. The model was built starting from a well validated mechanism taken from the literature and already used to predict the behavior of other alternative fuels. In flame conditions, DME forms formaldehyde as the major intermediate, the consumption of which leads in few steps to CO then CO2. The lower amount of CH2 radicals in comparison with methane flames seems to decrease the possibility of prompt-NO formation. This paper covers the low temperature oxidation chemistry of DME which is necessary to properly predict ignition temperatures and auto-ignition delay times that are important parameters for safety.

scholarly journals Volatile, Low Lubricity Fuels in Gas Turbine Plants: A Review of Main Fuel Options and Their Respective Merits

1998 ◽  
Author(s):  
M. Molière ◽  
F. Geiger ◽  
E. Deramond ◽  
T. Becker
Keyword(s):  
Power Generation ◽  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Alternative Fuels ◽  
Primary Energy ◽  
Liquid Fuels ◽  
Heavy Duty ◽  
Gas Condensates ◽  
Clear Identification

While natural gas is achieving unrivalled penetration in the power generation sector, especially in gas-turbine combined cycles (CCGT), an increasing number of alternative fuels are in a position to take up the ground left vacant by this major primary energy. In particular, within the thriving family of liquid fuels, the class of volatile products opens interesting prospects for clean and efficient power generation in CCGT plants. Therefore, it has become a necessity for the gas turbine industry to extensively evaluate such new fuel candidates, among which: naphtha’s; kerosines; gas condensates; Natural Gas Liquids (NGL) and alcohols are the most prominent representatives. From a technical standpoint, the success of such projects requires both a careful approach to several specific issues (eg: fuel handling & storage, operation safety) and a clear identification of technological limits. For instance, while the purity of gas condensates meets the requirements of heavy-duty technologies, it generally appears unsuitable for aeroderivative machines. This paper offers a succinct but comprehensive technical approach and overviews some experience acquired in this area with heavy duty gas turbines. Its aim is to inform gas turbine users/engineers and project developers who envisage volatile fuels as alternative primary energies in gas turbine plants.

scholarly journals CFD Modeling of Syngas Combustion and Emissions for Marine Gas Turbine Applications

2016 ◽  
Vol 23 (3) ◽  
pp. 39-49 ◽  
Author(s):  
Nader R. Ammar ◽  
Ahmed I. Farag
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Alternative Fuels ◽  
Flame Temperature ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Ansys Fluent ◽  
Gas Fuel

Abstract Strong restrictions on emissions from marine power plants will probably be adopted in the near future. One of the measures which can be considered to reduce exhaust gases emissions is the use of alternative fuels. Synthesis gases are considered competitive renewable gaseous fuels which can be used in marine gas turbines for both propulsion and electric power generation on ships. The paper analyses combustion and emission characteristics of syngas fuel in marine gas turbines. Syngas fuel is burned in a gas turbine can combustor. The gas turbine can combustor with swirl is designed to burn the fuel efficiently and reduce the emissions. The analysis is performed numerically using the computational fluid dynamics code ANSYS FLUENT. Different operating conditions are considered within the numerical runs. The obtained numerical results are compared with experimental data and satisfactory agreement is obtained. The effect of syngas fuel composition and the swirl number values on temperature contours, and exhaust gas species concentrations are presented in this paper. The results show an increase of peak flame temperature for the syngas compared to natural gas fuel combustion at the same operating conditions while the NO emission becomes lower. In addition, lower CO2 emissions and increased CO emissions at the combustor exit are obtained for the syngas, compared to the natural gas fuel.

Predicting Flameholding for Hydrogen and Natural Gas Flames at Gas Turbine Premixer Conditions

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Elliot Sullivan-Lewis ◽  
Vincent McDonell
Keyword(s):  
Power Generation ◽  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Experimental Studies ◽  
Temperature Variations ◽  
Auto Ignition ◽  
Chamber Temperature ◽  
Transient Events ◽  
Significant Effort

Lean-premixed gas turbines are now common devices for low emissions stationary power generation. By creating a homogeneous mixture of fuel and air upstream of the combustion chamber, temperature variations are reduced within the combustor, which reduces emissions of nitrogen oxides. However, by premixing fuel and air, a potentially flammable mixture is established in a part of the engine not designed to contain a flame. If the flame propagates upstream from the combustor (flashback), significant engine damage can result. While significant effort has been put into developing flashback resistant combustors, these combustors are only capable of preventing flashback during steady operation of the engine. Transient events (e.g., auto-ignition within the premixer and pressure spikes during ignition) can trigger flashback that cannot be prevented with even the best combustor design. In these cases, preventing engine damage requires designing premixers that will not allow a flame to be sustained. Experimental studies were conducted to determine under what conditions premixed flames of hydrogen and natural gas can be anchored in a simulated gas turbine premixer. Tests have been conducted at pressures up to 9 atm, temperatures up to 750 K, and freestream velocities between 20 and 100 m/s. Flames were anchored in the wakes of features typical of premixer passageways, including cylinders, steps, and airfoils. The results of this study have been used to develop an engineering tool that predicts under what conditions a flame will anchor, and can be used for development of flame anchoring resistant gas turbine premixers.

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.

scholarly journals Prediction of Auto-Ignition Temperatures and Delays for Gas Turbine Applications

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Roda Bounaceur ◽  
Pierre-Alexandre Glaude ◽  
Baptiste Sirjean ◽  
René Fournet ◽  
Pierre Montagne ◽  
...  
Keyword(s):  
High Temperature ◽  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Equivalence Ratio ◽  
Process Conditions ◽  
Piping System ◽  
Gaseous Fuels ◽  
Auto Ignition ◽  
Wide Range

Gas turbines burn a large variety of gaseous fuels under elevated pressure and temperature conditions. During transient operations, variable gas/air mixtures are involved in the gas piping system. In order to predict the risk of auto-ignition events and ensure a safe operation of gas turbines, it is of the essence to know the lowest temperature at which spontaneous ignition of fuels may happen. Experimental auto-ignition data of hydrocarbon–air mixtures at elevated pressures are scarce and often not applicable in specific industrial conditions. Auto-ignition temperature (AIT) data correspond to temperature ranges in which fuels display an incipient reactivity, with timescales amounting in seconds or even in minutes instead of milliseconds in flames. In these conditions, the critical reactions are most often different from the ones governing the reactivity in a flame or in high temperature ignition. Some of the critical paths for AIT are similar to those encountered in slow oxidation. Therefore, the main available kinetic models that have been developed for fast combustion are unfortunately unable to represent properly these low temperature processes. A numerical approach addressing the influence of process conditions on the minimum AIT of different fuel/air mixtures has been developed. Several chemical models available in the literature have been tested, in order to identify the most robust ones. Based on previous works of our group, a model has been developed, which offers a fair reconciliation between experimental and calculated AIT data through a wide range of fuel compositions. This model has been validated against experimental auto-ignition delay times corresponding to high temperature in order to ensure its relevance not only for AIT aspects but also for the reactivity of gaseous fuels over the wide range of gas turbine operation conditions. In addition, the AITs of methane, of pure light alkanes, and of various blends representative of several natural gas and process-derived fuels were extensively covered. In particular, among alternative gas turbine fuels, hydrogen-rich gases are called to play an increasing part in the future so that their ignition characteristics have been addressed with particular care. Natural gas enriched with hydrogen, and different syngas fuels have been studied. AIT values have been evaluated in function of the equivalence ratio and pressure. All the results obtained have been fitted by means of a practical mathematical expression. The overall study leads to a simple correlation of AIT versus equivalence ratio/pressure.

Gas Turbine Fouling: The Influence of Climate and Part-Load Operating Conditions

2019 ◽  
Author(s):  
Nicola Aldi ◽  
Nicola Casari ◽  
Mirko Morini ◽  
Michele Pinelli ◽  
Pier Ruggero Spina ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Alternative Fuels ◽  
Environmental Influence ◽  
Electrical Power ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Continuous Increase ◽  
Part Load

Abstract Energy and climate change policies associated with the continuous increase in natural gas costs pushed governments to invest in renewable energy and alternative fuels. In this perspective, the idea to convert gas turbines from natural gas to syngas from biomass gasification could be a suitable choice. Biogas is a valid alternative to natural gas because of its low costs, high availability and low environmental impact. Syngas is produced with the gasification of plant and animal wastes and then burnt in gas turbine combustor. Although synfuels are cleaned and filtered before entering the turbine combustor, impurities are not completely removed. Therefore, the high temperature reached in the turbine nozzle can lead to the deposition of contaminants onto internal surfaces. This phenomenon leads to the degradation of the hot parts of the gas turbine and consequently to the loss of performance. The amount of the deposited particles depends on mass flow rate, composition and ash content of the fuel and on turbine inlet temperature (TIT). Furthermore, compressor fouling plays a major role in the degradation of the gas turbine. In fact, particles that pass through the inlet filters, enter the compressor and could deposit on the airfoil. In this paper, the comparison between five (5) heavy-duty gas turbines is presented. The five machines cover an electrical power range from 1 MW to 10 MW. Every model has been simulated in six different climate zones and with four different synfuels. The combination of turbine fouling, compressor fouling, and environmental conditions is presented to show how these parameters can affect the performance and degradation of the machines. The results related to environmental influence are shown quantitatively, while those connected to turbine and compressor fouling are reported in a more qualitative manner. Particular attention is given also to part-load conditions. The power units are simulated in two different operating conditions: 100 % and 80 % of power rate. The influence of this variation on the intensity of fouling is also reported.

Alternative Fuels for Gas Turbine Plants — An Engineering, Procurement, and Construction Contractor’s Perspective

1998 ◽  
Author(s):  
Ram G. Narula
Keyword(s):  
Developing Countries ◽  
Natural Gas ◽  
Gas Turbine ◽  
Power Plants ◽  
Alternative Fuels ◽  
Heavy Oils ◽  
Liquefied Petroleum Gas ◽  
Massive Growth ◽  
Balance Of Plant ◽  
Private Power

Tightly regulated and state-controlled utilities are rapidly changing into a competitive, market-driven industry, as private power development is being actively pursued worldwide. Accelerated economic growth in developing countries has fueled a massive growth in the power sector. Gas turbine based power plants have become an attractive option; however, many of these developing countries have limited supplies of conventional gas turbine fuels, namely natural gas or distillate oil. Therefore, power developers are seeking alternative fuels. This paper discusses the balance-of-plant (BOP) considerations and economics of using alternative fuels such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), naphtha, and crude/heavy oils.

Operability Limits of Tubular Injectors With Vortex Generators for a Hydrogen Fuelled Recuperated 100kW Class Gas Turbine

2016 ◽  
Author(s):  
Stefan Bauer ◽  
Balbina Hampel ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Bulk Flow ◽  
Vortex Generators ◽  
Test Rig ◽  
Temperature Range ◽  
Auto Ignition ◽  
Wide Range

Vortex generators are known to be effective in augmenting the mixing of fuel jets with air. The configuration investgated in this study is a tubular air passage with fuel injection from one single orifice placed in the side wall. In the range of typical gas turbine combustor inlet temperatures, the performance vortex generator premixers (VGPs) have already been investigated for natural gas as well as for blends of natural gas and hydrogen. However, for highly reactive fuels, the application of VGPs in recuperated gas turbines is particularly challenging because the high combustor inlet temperature leads to potential risk with regard to premature self-ignition and flame flashback. As the current knowledge does not cover the temperature range far above the self-ignition temperature, an experimental investigation of the operational limits of VGPs is currently being conducted at the Thermodynamics Institute of the Technical University of Munich, which is particularly focused on reactive fuels and the thermodynamic conditions present in recuperated gas turbines with pressure ratios of 4–5. For the study presented in the paper, an atmospheric combustion VGP test rig has been designed, which facilitates investigations in a wide range of operating conditions in order to comply with the situation in recuperated micro gas turbines, namely global equivalence ratios between 0.2 and 0.7, air preheating temperatures between 288K and 1100K, and air bulk flow rates between 6–16 g/s. Both the entire mixing zone in the VGP and the primary combustion zone of the test rig are optically accessible. High speed OH* chemiluminescence imaging is used for the detection of the flashback and blow-off limits of the investigated VGPs. Flashback and blow-off limits of hydrogen in a wide temperature range covering the auto-ignition regime are presented, addressing the influences of equivalence ratio, air preheating temperature and momentum ratio between air and hydrogen on the operational limits in terms of bulk flow velocity. It is shown that flashback and blow-off limits are increasingly influenced by auto-ignition in the ultra-high temperature regime.

Gas Turbines in Alternative Fuel Applications: The Utilization of Highly Aromatic Fuels in Power Generation

2004 ◽  
Author(s):  
Michel Moliere ◽  
Frederic Geiger
Keyword(s):  
Power Generation ◽  
Gas Turbine ◽  
Benzene Ring ◽  
Gas Turbines ◽  
Alternative Fuels ◽  
Diffusion Flames ◽  
Jet Fuels ◽  
Heavy Duty ◽  
Auto Ignition ◽  
Burn Out

Heavy Duty Gas Turbines enjoy a wide fuel capability that makes them increasingly popular power generation tools in several branches of the industry. Among Alternative Fuels for gas turbines is a group of “Aromatic Fuels”. These fuels are presently virtually unknown but they offer interesting prospects namely for captive power in the refining and petrochemistry. Until now there has been a limited awareness of the combustion issues posed by Aromatic Fuels especially in the high temperature, medium pressure conditions of gas turbine combustors. This apparent disinterest is tied to various issues namely: - smoke problems faced by the aviation sector during the 70’s that were caused by “aromatic jet fuels”; - the supremacy of natural gas that monopolizes R&D combustion efforts for power applications. The success of light aromatics in spark engines as substitutes for lead-based RON improvers has been stopped by the ban of aromatics in car fuels. Toxicity is thus another blemish of aromatic fuels. Chemically, aromatic fuels involve a wide diversity of molecules in structure and size, ranging from simple mono-aromatics (one benzene ring) to poly-aromatics (up to 3 condensed benzene rings). The general combustion problem posed by aromatic fuels lies in the high thermal stability of the benzene ring in oxidative conditions and its propensity to condense on itself and to form soot particles. In addition, the high Auto Ignition Temperature and Delay of Aromatic Fuels make them improper for combustion in Diesel engines and require large residence time in atmospheric flames. Interestingly, it appears that, with their hot and lean diffusion flames and relatively oxidizing combustion zones, Heavy Duty Gas Turbines exhibit a remarkable ability to break and cleanly burn out these molecules. The paper presents this new class of gas turbine fuels, outlines their market rationale and offers key combustion considerations to ensure clean utilization. It also summarizes the experience gathered by a gas turbine manufacturer in the combustion of BTX, C9+ and LCO type fuels. It also outlines the chemical mechanisms that underlie the clean combustion of aromatic fuels in gas turbine chambers.

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