Power-Gen International 2008 Orlando, Florida

Transcription

1 ULTRA LOW NOX COMBUSTION TECHNOLOGY Power-Gen International 2008 Orlando, Florida

2 PowerGen International Orlando, Florida December ULTRA LOW NOX COMBUSTION TECHNOLOGY Clifford Johnson, Barton Pepperman, Michael Koenig, Khalil Abou-Jaoude, Anil Gulati, Ali Moradian Siemens Power Generation Inc., 4400 Alafaya Trail, Orlando, FL Greg Hall Idaho Power, Boise, Idaho Abstract Siemens Power Generation combustion technology has undergone a significant transformation over the past 20 years. Evolving from the 1980's diffusion flame combustor technology, which produces a very stable flame, but is associated with relatively higher levels of emissions output of some constituents, Siemens Power Generation incorporated material and technological design advancements, industry-leading design engineers, and state of the art design tools to develop a successful Dry Low NOx (DLN) combustion system in the 1990's. Dry Low NOx technology provides reduced NOx emissions through a staged combustion proc- ess and unique temperature and heat release strategy. This four- stage premixed combustion process is designed to produce reli- the environmental compatibility of Siemens Power Generation's fleet of gas turbines, the Dry Low NOx technology has evolved into a combustion system, commercially offered as Ultra Low able and stable combustion, with lower level emissions and is currently installed in over 100 Siemens GT's. Further improving NOx (ULN), which is designed to achieve sub 9 ppm NOx emis- tem is characterized by a five stage premixed combustion proc- sions. In addition to stable combustion, the Ultra Low NOx sys- ess that employs a premixed pilot stage. Demonstration of Siemens Power Generation's combustion tech- nology is typically extensive, following a detailed design, rig and field test, and then full scale engine testing process, which lead to commercial introduction. The Ultra Low NOx combustion system has been introduced into the commercial fleet, and operating ex- perience with it has included high GT efficiency and sub 9ppm NOx emissions, across a wide operating range, as recently demonstrated at Idaho Power's Evander Andrews site.

3 PowerGen International Orlando, Florida December Contents Introduction... 4 Combustor Design Features... 5 Operation... 7 Testing and Verification... 8 Field Validation Idaho Power...9 Summary Permission for Use...10 References...11

4 PowerGen International Orlando, Florida December Introduction Building upon its history of advanced gas turbine combustion systems, Siemens has developed a robust Ultra-Low NOx (ULN) combustor design for flexible, relirequirements able power generation is designed to meet the stringent emissions in the U.S. and abroad. This configuration utilizes a highly premixed combustion system that was designed for SGT6-5000F and W501F engines. The ULN de- sign is applicable for new units and is also retrofittable to the existing fleet. The Siemens ULN technology is derived from the well-proven and robust Dry Low NOx (DLN) combustion system design that has been operating in SGT6-3000E, SGT6-5000F, and SGT6-6000G (W501D5/D5A, W501F, and W501G) engines for more than 10 years. Recent enhancements to the DLN combustion system have contributed to the world-class reliability, performance and operational flexibility of the newest Siemens SGT6-5000F gas turbines. [1] In response to market requirements for even lower NOx emissions, Siemens has leveraged this DLN design and operating experience into the development of the next-generation ULN combustion system technology, which has demonstrated sub-9ppm NOx emissions for F-class engines. In addition to the low NOx emis- design produces lower CO, VOC and particulate sions, the ULN combustor emissions. In combination with the Siemens low load CO system, this combustion system is capable of producing single-digit CO emissions down to 40% load. Additionally, the ULN design can meet these requirements for a wider range of fuels, including LNG. [2].

5 PowerGen International Orlando, Florida December Combustor Design Features The ULN combustion system shown in Figure 1 comprises a combustor basket, pilot nozzle, support housing, C-stage fuel nozzle, and transition. Most of the fuel is injected through eight main fuel nozzles in the support housing, which is divided into two fuel stages of four main nozzles each. The remainder of the fuel is divided between the C- stage and the pilot. The pilot nozzle includes a diffusion stage and a premix pilot stage. The premix pilot (D-stage) and the two main fuel stages (A and B stages) utilize swirler fuel injection (SFI) technology, which is the key design feature that enables this cominjection holes in the swirler vanes, enhanced fuel/air mixing is achieved, thus reducing bustor design to achieve sub-9ppm NOx emissions. By injecting fuel through multiple the peak temperature of local hot spots that contribute to NOx production. In addition to improved emissions, this design is capable of handling a wide range of fuel composition and fuel temperature. Figure 1: Ultra-Low NOx combustor cross-section

6 PowerGen International Orlando, Florida December Since the original engine test of this system in 2004 [3], the support housing was uptested in 2004 graded to add dual fuel capability. The original gas only design that was is shown in Figure 2. To accommodate the fuel oil tubing and increase the mechanical robustness of the fuel nozzles, the production support housing main nozzle bodies were redesigned as shown in Figure 3. As in the initial support housing design, the main fuel nozzles were designed to minimize CO production during loading. The pilot nozzle (Figure 4) and combustor basket (Figure 5) are very similar to the design that was tested in The ULN combustor basket incorporates design features from the proven DLN combustion system that has demonstrated the ability to operate at extended service intervals. Figure 2: Original Gas Only Support Housing Production nozzle body Figure 3: Dual Fuel Support Housing

7 PowerGen International Orlando, Florida December Figure 4: Dual Fuel Pilot Nozzle Figure 5: Combustor Basket Operation Table 1 shows the fuel staging used for the ULN combustion system. Similar to DLN, ignition is performed with fuel split between the diffusion pilot and main A-stage. Fuel is adjusted between these two stages to maintain stability during acceleration to synch speed. Near synch speed, the D-stage fuel is added. Below 25% load, the CO emissions are minimized by inje cting fuel through only the pilot, A and D-stages. B-stage fuel is introduced at 25% load to provide more uniform thermal loading and lower NOx emissions. Above 45% load, C-stage fuel is introduced to provide additional stability in the high load range. At high loads, 70-90% of the fuel is injected through the main fuel nozzles, with the remainder of the fuel being divided between the other fuel stages to provide the optimum tuning for low NOx and CO emissions while maintaining combustion dynamics below limits. Table 1: Fuel Staging

8 PowerGen International Orlando, Florida December Engines with the ULN combustion system are equipped with an active combustion dy- the combus- namics protection system (CDPS SPPA-D3000) that continually monitors tion dynamics levels and the engine emissions. After initial tuning of the engine during commissioning, the engine controller makes automatic real-time adjustments to the fuel fractions to maintain low emissions while protecting the engine against combustion dy- no action is namics. If the dynamics and NOx readings are within the allowable range, taken. If NOx emissions exceed the target value (e.g., due to a change in the fuel com- automatically modulates position or ambient temperature change), then the controller the D-stage fraction to reduce NOx, with the balance of the fuel offset by changes to A and B stages. If the combustion dynamics levels exceed the threshold value, then the D-stage fraction is adjusted to maintain dynamics levels within limits. Dual fuel operation with a ULN combustion system is very similar to DLN dual fuel operation. The engine can be started with either gas fuel or oil fuel. Transfers between gas and oil can be performed up to 70% load. Testing and Verification As discussed in [3], the ULN combustion system was developed through a combination of modeling with computational fluid dynamics, high pressure combustion rig testing and engine verification. A series of high pressure combustion rig tests were performed throughout the development of the first engine hardware. This hardware was success- above, fully demonstrated in an engine test on a SGT6-5000F in As described the production design incorporated dual fuel capability as well as a number of design enhancements. These design enhancements were tested in a single can high pressure combustor test rig to assess impacts on emissions and combustion dynamics. Final engine verification was performed at the Siemens Berlin Test Facility, a highly instrumented full scale SGT6-5000F engine, which operates at full load. The verification test at Berlin Test Facility included both gas and oil operation. With gas fuel, sub-9ppm NOx and sub-10ppm CO emissions were demonstrated for part load as well as base load operation. On oil fuel, sub-42ppm NOx and sub-10ppm CO emissions were demonstrated over the same load range. Fuel transfers between gas and oil were performed over a wide range of part load operation. More than 500 operating hours of validation and verification were performed between the first ULN demonstration and the final engine verification at the Siemens Berlin Test Facility prior to commercial release of the ULN design for production.

9 PowerGen International Orlando, Florida December Field Validation Idaho Power Following the final engine verification testing at the Berlin Test Facility engine, the first commercial application of the ULN combustion system was commissioned at the Idaho Power Evander Andrews project, Mountain Home, Idaho, a simple cycle SGT6-5000F). First fire of this unit occurred in February, The unit has performed as expected based upon Berlin Test Facility results. In particular, the engine has excellent starting reliability, and base load was achieved without any operational difficulty. During commissioning, the unit successfully demonstrated base load and part load per- re- formance with NOx emissions < 9ppm and meeting all contractual performance quirements. Figure 6 demonstrates that the ULN system meets <9ppm emissions for base load operation in the acceptable combustor dynamics operating range. Figure 7 shows the turndown from 60% to base load. This performance has been consistently demonstrated at the Evander Andrews project for a period of over 6 months, totaling more than 250 EBH and 25 ES. During this time, operation has been validated over a wide range of ambient operating conditions. Combus tor Dy namics Amplitude Combustion Dynamics Alarm Limit Acceptable Combustion Dynamics Operating Range NOx 15% O2) Figure 6: Combustor Dynamics at Base Load

10 PowerGen International Orlando, Florida December Emissions 15%O NOx CO Load % Figure 7: ULN Emission Results Summary The Siemens ULN combustion system has been validated and is now being offered commercially. The first commissioning effort of this engine at the Idaho Power Evander Andrews project was very successful, meeting all contractual performance guarantees. Emissions levels below 9ppm NOx and 10ppm CO were achieved for part load and base load operation. The lessons learned and methodology applied in the development of this combustion system are being used for development of new Siemens gas turbine products. Permission for Use The content of this paper is copyrighted by Siemens Power Generation, Inc. and is licensed only to PennWell for publication and distribution. Any inquiries regarding permission to use the content of this paper, in whole or in part, for any purpose must be addressed to Siemens Power Generation, Inc. directly.

11 PowerGen International Orlando, Florida December References 1. Kovac, J., Xia, J., SGT6-5000F Technology Enhancements, POWER-GEN International Engel, J., Nag, P., Abou-Jaoude, K., Wu, J., LaGrow, M., Liquefied Natural Gas (LNG) Flexibility Solutions for Large-Scale Gas Turbines, POWER-GEN International Bland, R., Ryan, W., Abou-Jaoude, K., Bandatu, R., Haris, A., Rising, B., 2004, Siemens W501F Gas Turbine : Ultra Low NOx Combustion System Development, POWER-GEN International 2004.