Low NOx Lean Premix Reheat Combustion in Alstom GT24 Gas Turbines

Author(s):  
Daniel Guyot ◽  
Gabrielle Tea ◽  
Christoph Appel

Reducing gas turbine emissions and increasing their operational flexibility are key targets in today's gas turbine market. In order to further reduce emissions and increase the operational flexibility of its GT24 (60 Hz) and GT26 (50 Hz), Alstom has introduced an improved sequential environmental (SEV) burner and fuel lance into its GT24 and GT26 upgrades 2011 sequential reheat combustion system. Sequential combustion is a key differentiator of Alstom GT24/GT26 engines in the F-class gas turbine market. The inlet temperature for the SEV combustor is around 1000 °C and reaction of the fuel/oxidant mixture is initiated through auto-ignition. The recent development of the Alstom sequential combustion system is a perfect example of evolutionary design optimizations and technology transfer between Alstom GT24 and GT26 engines. Better overall performance is achieved through improved SEV burner aerodynamics and fuel injection, while keeping the main features of the sequential burner technology. The improved SEV burner/lance concept has been optimized toward rapid fuel/oxidant mixing for low emissions, improved fuel flexibility with regard to highly reactive fuels (higher C2+ and hydrogen content), and to sustain a wide operation window. The burner front panel features an improved cooling concept based on near-wall cooling as well as integrated acoustics damping devices designed to reduce combustion pulsations, thus extending the SEV combustor's operation window even further. After having been validated extensively in Alstom's high pressure (HP) sector rig test facility, the improved GT24 SEV burner has been retrofitted into a commercial GT24 field engine for full engine validation during long-term operation. This paper presents the obtained HP sector rig and engine validation results for the GT24 (2011) SEV burner/lance hardware with a focus on reduced NOx and CO emissions and improved operational behavior of the SEV combustor. The HP tests demonstrated robust SEV burner/lance operation with up to 50% lower NOx formation and a more than 70 K higher SEV burner inlet temperature compared to the GT24 (2006) hardware. For the GT24 engine with retrofitted upgrade 2011 SEV burner/lance, all validation targets were achieved including an extremely robust operation behavior, up to 40% lower GT NOx emissions, significantly lower CO emissions at partload and baseload, a very broad operation window (up to 100 K width in SEV combustor inlet temperature), and all measured SEV burner/lance temperatures in the expected range. Sector rig and engine validation results have confirmed the expected SEV burner fuel flexibility (up to 18 vol. % C2+ and up to 5 vol. % hydrogen as standard).

Author(s):  
Daniel Guyot ◽  
Gabrielle Tea ◽  
Christoph Appel

Reducing gas turbine emissions and increasing their operational flexibility are key targets in today’s gas turbine market. In order to further reduce emissions and increase the operational flexibility of its GT24 (60Hz) and GT26 (50Hz), Alstom has introduced an improved SEV burner and fuel lance into its GT24 upgrade 2011 and GT26 upgrade 2011 sequential reheat combustion system. Sequential combustion is a key differentiator of Alstom GT24 engines in the F-class gas turbine market. The inlet temperature for the GT24 SEV combustor is around 1000 degC and reaction of the fuel/oxidant mixture is initiated through auto-ignition. The recent development of the Alstom sequential combustion system is a perfect example of evolutionary design optimizations and technology transfer between Alstom GT24 and GT26 engines. Better overall performance is achieved through improved SEV burner aerodynamics and fuel injection, while keeping the main features of the sequential burner technology. The improved SEV burner/lance concept has been optimized towards rapid fuel/oxidant mixing for low emissions, improved fuel flexibility with regards to highly reactive fuels (higher C2+ and hydrogen content), and to sustain a wide operation window. In addition, the burner front panel features an improved cooling concept based on near-wall cooling as well as integrated acoustics damping devices designed to reduce combustion pulsations thus extending the SEV combustor’s operation window even further. After having been validated extensively in the Alstom high pressure sector rig test facility, the improved GT24 SEV burner has been retrofitted into a commercial GT24 field engine for full engine validation during long-term operation. This paper presents the obtained high pressure sector rig and engine validation results for the GT24 (2011) SEV burner/lance hardware with a focus on reduced NOX and CO emissions and improved operational behavior of the SEV combustor. The high pressure tests demonstrated robust SEV burner/lance operation with up to 50% lower NOX formation and a more than 70K higher SEV burner inlet temperature compared to the GT24 (2006) hardware. For the GT24 engine with retrofitted upgrade 2011 SEV burner/lance all validation targets were achieved including an extremely robust operation behavior, up to 40% lower GT NOX emissions, significantly lower CO emissions at partload and baseload, a very broad operation window (up to 100K width in SEV combustor inlet temperature) and all measured SEV burner/lance temperatures in the expected range. Sector rig and engine validation results have confirmed the expected SEV burner fuel flexibility (up to 18%-vol. C2+ and up to 5%-vol. hydrogen as standard).


Author(s):  
Hasan Karim ◽  
Jayaprakash Natarajan ◽  
Venkat Narra ◽  
Jun Cai ◽  
Shreekrishna Rao ◽  
...  

Driven by global warming, a relentless march towards increased fuel efficiency has resulted in increased firing temperature for HA-class engines without an increase in baseload emissions. Moreover, emissions compliance for CO, NOx, and unburned hydrocarbons are desired over increased range in gas turbine load. In addition, exceptional gas turbine operational flexibility is desired to address potential intermittency due to the penetration of renewables in the electrical grid. Staged/sequential combustion is a state of the technology to provide operational flexibility and reduced emissions in power generation gas turbines. GE Power’s 7HA-class gas turbine combustion system combines GE’s proven DLN-2.6+ combustion technology, that has run reliably for over 1.3 million fired hours across more than eighty 9FA.03, 9F.05 & 7FA gas turbine engines, with an axially fuel staged system (AFS). Axially staging combustion to two zones allows for increased firing temperature at baseload (while maintaining the same NOx level) by operating the later/second stage hotter than the first/primary stage. During low load operation as the gas turbine firing temperature is reduced, percentage fuel split in the staged fuel system can either be reduced significantly or turned off and thereby keeping the overall combustion system into emissions compliance over a wider range of firing temperatures. This paper presents both the development testing of the staged combustion in the FA and HA class gas turbine combustion system rigs at GE Power’s Gas Turbine Technology Laboratory and the validation testing of staged combustion system for the 7HA.01 engine completed during Spring 2016 at GE Power’s engine test facility in Greenville, SC. The paper also discusses the significant simplification of operational principle and flexibility of startup, loading and baseload operation of the 7HA combustion system. Discussion of engine test results will show how axial fuel staging was utilized to demonstrate emissions compliance ( NOx (15% O2) < 25 ppm; CO < 9 ppm), operation from 14% load to 100% load with low combustion dynamics and also to enable wide wobbe capability, which is a normalized measure of fuel flexibility.


Author(s):  
Douglas A. Pennell ◽  
Mirko R. Bothien ◽  
Andrea Ciani ◽  
Victor Granet ◽  
Ghislain Singla ◽  
...  

This paper introduces and presents validation of the Constant Pressure Sequential Combustion system (denoted CPSC), a second generation concept developed for and applied to the new Ansaldo GT36 H-class gas turbine combustors. It has evolved from the well-established sequential burner technology applied to all current GT26 and GT24 gas turbines, and contains all architectural improvements implemented since original inception of this engine frame in 1994, with beneficial effects on the operation turndown, fuel flexibility, on the overall system robustness, and featuring the required aspects to stay competitive in the present day energy market. The applied air and fuel management therefore facilitate emission and dynamics control at both the extremely high and low firing temperature ranges required for existing and future Ansaldo gas turbine engine classes.


Author(s):  
Katsuyoshi Tada ◽  
Kei Inoue ◽  
Tomo Kawakami ◽  
Keijiro Saitoh ◽  
Satoshi Tanimura

Gas-turbine combined-cycle (GTCC) power generation is clean and efficient, and its demand will increase in the future from economic and social perspectives. Raising turbine inlet temperature is an effective way to increase combined cycle efficiency and contributes to global environmental conservation by reducing CO2 emissions and preventing global warming. However, increasing turbine inlet temperature can lead to the increase of NOx emissions, depletion of the ozone layer and generation of photochemical smog. To deal with this issue, MHPS (MITSUBISHI HITACHI POWER SYSTEMS) and MHI (MITSUBISHI HEAVY INDUSTRIES) have developed Dry Low NOx (DLN) combustion techniques for high temperature gas turbines. In addition, fuel flexibility is one of the most important features for DLN combustors to meet the requirement of the gas turbine market. MHPS and MHI have demonstrated DLN combustor fuel flexibility with natural gas (NG) fuels that have a large Wobbe Index variation, a Hydrogen-NG mixture, and crude oils.


Author(s):  
Ralph A. Dalla Betta ◽  
James C. Schlatter ◽  
Sarento G. Nickolas ◽  
Martin B. Cutrone ◽  
Kenneth W. Beebe ◽  
...  

The most effective technologies currently available for controlling NOx emissions from heavy-duty industrial gas turbines are either diluent injection in the combustor reaction zone, or lean premixed Dry Low NOx (DLN) combustion. For ultra low emissions requirements, these must be combined with selective catalytic reduction (SCR) DeNOx systems in the gas turbine exhaust. An alternative technology for achieving comparable emissions levels with the potential for lower capital investment and operating cost is catalytic combustion of lean premixed fuel and air within the gas turbine. The design of a catalytic combustion system using natural gas fuel has been prepared for the GE model MS9OOIE gas turbine. This machine has a turbine inlet temperature to the first rotating stage of over 1100°C and produces approximately 105 MW electrical output in simple cycle operation. The 508 mm diameter catalytic combustor designed for this gas turbine was operated at full-scale conditions in tests conducted in 1992 and 1994. The combustor was operated for twelve hours during the 1994 test and demonstrated very low NOx emissions from the catalytic reactor. The total exhaust NOx level was approximately 12–15 ppmv and was produced almost entirely in the preburner ahead of the reactor. A small quantity of steam injected into the preburner reduced the NOx emissions to 5–6 ppmv. Development of the combustion system has continued with the objectives of reducing CO and UHC emissions, understanding the parameters affecting reactor stability and spatial non-uniformities which were observed at low inlet temperature, and improving the structural integrity of the reactor system to a level required for commercial operation of gas turbines. Design modifications were completed and combustion hardware was fabricated for additional full-scale tests of the catalytic combustion system in March 1995 and January 1996. This paper presents a discussion of the combustor design, the catalytic reactor design and the results of full-scale testing of the improved combustor at MS9OOIE cycle conditions in the March 1995 and January 1996 tests. Major improvements in performance were achieved with CO and UHC emissions of 10 ppmv and 0 ppmv at base load conditions. This ongoing program will lead to two additional full-scale combustion system tests in 1996. The results of these tests will be available for discussion at the June 1996 Conference in Birmingham.


Author(s):  
Martin Zajadatz ◽  
Douglas Pennell ◽  
Stefano Bernero ◽  
Bettina Paikert ◽  
Raffaele Zoli ◽  
...  

Increasing public awareness and more stringent legislation on pollutants drive gas turbine manufacturers to develop combustion systems with low NOx emissions. In combination to this demand the gas turbines have to provide a broad range of operational flexibility to cover variations in gas composition and ambient conditions as well as varying daily and seasonal energy demands and load profiles. This paper describes the development and implementation of the Alstom AEV (Advanced EnVironmental) burner, an evolution of the EV. Continuous fuel supply to two fuel stages at any engine load simplifies the operation and provides a fast and reliable response of the combustion system during transient operation of the gas turbine. Increased turndown with low emissions is an additional advantage of the combustion system upgrade.


Author(s):  
G. J. Kelsall ◽  
M. A. Smith ◽  
H. Todd ◽  
M. J. Burrows

Advanced coal based power generation systems such as the British Coal Topping Cycle offer the potential for high efficiency electricity generation with minimum environmental impact. An important component of the Topping Cycle programme is the development of a gas turbine combustion system to burn low calorific value (3.5–4.0 MJ/m3 wet gross) coal derived fuel gas, at a turbine inlet temperature of 1260°C, with minimum pollutant emissions. The paper gives an overview of the British Coal approach to the provision of a gas turbine combustion system for the British Coal Topping Cycle, which includes both experimental and modelling aspects. The first phase of this programme is described, including the design and operation of a low-NOx turbine combustor, operating at an outlet temperature of 1360°C and burning a synthetic low calorific value (LCV) fuel gas, containing 0 to 1000 ppmv of ammonia. Test results up to a pressure of 8 bar are presented and the requirements for further combustor development outlined.


Author(s):  
Ryozo Tanaka ◽  
Testuo Tastumi ◽  
Yoshihiro Ichikawa ◽  
Koji Sanbonsugi

Based on the successful results of the Japanese national project for 300 kW ceramic gas turbine(CGT302) development (this project was finished in March 1999), the Ministry of International Trade and Industry (MITI) started “Research and Development on Practical Industrial Co-generation Technology” project in August 1999. The objective of this project is to encourage prompt industrial applications of co-generation technology that employs hybrid gas turbines (HGT; using both metal and ceramic parts in its high-temperature section) by confirming its soundness and reliability. The development activities are performed through material evaluation tests and long-term operation tests for the HGT of the medium size (8,000-kW class). It is expected that the development can realize low pollution and reducing the emission of CO2 with highly efficient use of energy. The HGT will be developed by applying ceramic components to an existing commercial 7,000-kW class gas turbine. The development targets are thermal efficiency of 34% or higher, output of 8,000-kW class, inlet temperature of 1250deg-C, and 4,000hrs of operation period for confirmation of reliability. The HGT for long-term evaluation tests and the test plant are under development. This paper gives the summary of last year’s developments in the HGT project.


Author(s):  
Stefano Cocchi ◽  
Michele Provenzale ◽  
Gianni Ceccherini

An experimental test campaign, aimed to provide a preliminary assessment of the fuel flexibility of small power gas turbines equipped with Dry Low NOx (DLN) combustion systems, has been carried over a full-scale GE10 prototypical unit, located at the Nuovo-Pignone manufacturing site, in Florence. Such activity is a follow-up of a previous experimental campaign, performed on the same engine, but equipped with a diffusive combustion system. The engine is a single shaft, simple cycle gas turbine designed for power generation applications, rated for 11 MW electrical power and equipped with a DLN silos type combustor. One of the peculiar features of such combustion system is the presence of a device for primary combustion air staging, in order to control flame temperature. A variable composition gaseous fuel mixture has been obtained by mixing natural gas with CO2 up to about 30% vol. inerts concentration. Tests have been carried over without any modification of the default hardware configuration. Tests performed aimed to investigate both ignition limits and combustors’ performances, focusing on hot parts’ temperatures, pollutant emissions and combustion driven pressure oscillations. Results indicate that ignition is possible up to 20% vol. inerts concentration in the fuel, keeping the fuel flow during ignition at moderately low levels. Beyond 20% vol. inerts, ignition is still possible increasing fuel flow and adjusting primary air staging, but more tests are necessary to increase confidence in defining optimal and critical values. Speed ramps and load operation have been successfully tested up to 30% vol. inerts concentration. As far as speed ramps, the only issue evidenced has been risk of flameout, successfully abated by rescheduling combustion air staging. As far as load operation, the combustion system has proven to be almost insensitive to any inerts concentration tested (up to 30% vol.): the only parameter significantly affected by variation in CO2 concentration has been NOx emission. As a complementary activity, a simplified zero-dimensional model for predicting NOx emission has been developed, accounting for fuel dilution with CO2. The model is based on main turbine cycle and DLN combustion system controlling parameters (i.e., compressor pressure ratio, firing temperature, pilot fuel and primary air staging), and has been tuned achieving good agreement with data collected during the test campaign.


Author(s):  
Frank Reiss ◽  
Sven-Hendrik Wiers ◽  
Ulrich Orth ◽  
Emil Aschenbruck ◽  
Martin Lauer ◽  
...  

This paper describes the development and test results of the low emission combustion system for the new industrial gas turbines in the 6–7 MW class from MAN Diesel & Turbo. The design of a robust combustion system and the achievement of very low emission targets were the most important design goals of the combustor development. During the design phase, the analysis of the combustor (i.e. burner design, air distribution, liner cooling design) was supported with different CFD tools. This advanced Dry Low Emission can combustion system (ACC) consists of 6 cans mounted externally on the gas turbine. The behavior and performance of a single can sector was tested over a wide load range and with different boundary conditions; first on an atmospheric test rig and later on a high pressure test rig with extensive instrumentation to ensure an efficient test campaign and accurate data. The atmospheric tests showed a very good performance for all combustor parts and promising results. The high pressure tests demonstrated very stable behavior at all operation modes and very low emissions to satisfy stringent environmental requirements. The whole operation concept of the combustion system was tested first on the single-can high pressure test bed and later on twin and single shaft gas turbines at MAN’s gas turbine test facility. During the engine tests, the can combustors demonstrated the expected combustion performance under real operation conditions. All emissions and performance targets were fully achieved. On the single shaft engine, the combustors were running with single digit ppm NOx levels between 50% and 100% load. The validation phase and further optimization of the gas turbines and the engine components are ongoing. The highlights of the development process and results of the combustor and engine tests will be presented and discussed within this paper.


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