Earlier this year, Cheng Power

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1 1.8:1 steam-to-fuel ratio reduces output of LM25 to 5 By Victor de Biasi Test data verify that levels are reduced at relatively low steam-to-fuel injection ratios independently of load while increasing power and improving efficiency. Earlier this year, Cheng Power Systems reported outstanding performance of its steam/fuel mixture technology in simultaneously reducing and emissions for an LM25PE gas turbine in cogeneration service, while increasing power. Certified test measurements show that can be brought down to low single-digit levels with steam as a diluent. Up to now, this has been thought impossible. Further, can be reduced at both partial and full load operating conditions. LM25 performance highlights with 1.8:1 steam/fuel injection ratio for diffusion flame combustion: level. Reduced to 5 without catalytic converter compared to 15 for DLE combustion and 42 with water injection. Heat rate. Reduced to 8624 Btu/ kwh (39.6% efficiency) from 9654 Btu for DLE operation and 9574 Btu with water injection. Power. Increases to 26,125 kw ISO base load output compared to 21,719 kw for DLE operation and 23,879 kw with water injection. Test program This is the first application of Cheng s new CLN control technology for a high pressure ratio and high firing temperature gas turbine like the LM25 which has an annular combustor design, 19.5:1 pressure ratio and 215 F firing temperature. The actual retrofit for testing was made on a cogeneration installation in San Jose, California that is equipped with water injection and catalyst converter for emissions control. A Scandinavian oil company cosponsored the rtofit and test project to address an environmental issue with Cost. Typical payback for gas turbine retrofit, controls and steam supply is on the order of one year for a unit in base load service, LM25 CLN manifold. Supply piping is split into left and right sections connecting to a ring manifold system which distributes highly homogenous mix off steam and fuel through flexible piping to all thirty retrofitted CLN injection nozzles. 1 GAS TURBINE WORLD: May - June 29

2 and emissions produced by their own fleet of LM25 gas turbines on North Sea offshore platforms. The operational test data was certified by a third party to technically qualify the application of CLN technology to reduce emissions of their oil platform units and while increasing power output and efficiency, even during hot day operation. Demonstrated ability to achieve 5 for high pressure ratio and high firing temperature industrial aero and heavy frame gas turbines (without DLE or water injection) should be of special interest to operators in the U.S., particularly in Southern California. What makes it possible The key to effectiveness of the new CLN technology, says Dr, Dah Yu Cheng, president of Cheng Power Systems, is a specially designed mixing and control system that delivers close to a 1% homogeneous gaseous mix of steam and fuel to the injector nozzle tip. Under proper conditions, he explains, the concentration distribution of diluent steam and fuel mix remains constant within small vortices within the combustion zone. There is a sudden death reaction where the species meet at the flame envelope at which point they instantly disappear upon being converted into H 2 O and combustion products. During operational testing, 75 F steam for mixing with natural gas fuel was supplied by the cogeneration plant s HRSG. A steam control valve metered the amount of steam via a computer program so the operator could maintain a precise steam-tofuel ratio for engine operation at any load. The steam and fuel were first mixed through a T-section using rotational vanes (CRVs) inside the piping to encourage laminar intermingling of the two fluids. This was followed by a set of static mixers to more thoroughly homogenize the mixed fluid flow. An extra length of piping for the engine s fuel Potential for cost savings and credits. The value of savings and credits are based on 2Q 29 European cap and trade prices of $1 per ton in US dollars. Typical CLN retrofit for an LM25 in cogeneration service is expected to pay for itself in less than one year out of operational savings not counting the value of increased power output. Standard with WLE with DLE with CLN LM25PE combustor water inj lean premix steam inj Annual fuel $1,135, $ (-$112,) $1,588, savings Annual (-$617,) $ $132, $181, savings Annual $1, $ $9, $22, credit Net savings $618, $ $11, $1,989, manifold allowed the turbulent flow to continuously and thoroughly mix the steam and fuel. The piping system then split into left and right sections connecting to a ring manifold which supplied the mixture of steam and fuel to 3 injection nozzles around the LM25 gas turbine (see photo). To further enhance turbulent mixing, Dr. Cheng reports, additional static mixers were installed on each of the two legs before connecting to the ring manifold. Operational test procedure Actual testing was preceded by changing various steam-to-fuel ratio and transient conditions to test con- Comparative test and design ratings. A water injected gas turbine at a cogeneration site in San Jose, Calif. was retrofitted for testing Cheng s new CLN control technology to measure power output, heat rate and relative to water injection operation (WLE) and comparative CO2 production based on 85 hours of operation. Standard with WLE with DLE with CLN LM25PE combustor water inj lean premix steam inj Power output 22,81 kw 23,879 kw 21,719 kw 26,125 kw Heat rate/kwh 8796 Btu 9574 Btu 9654 Btu 8624 Btu Efficiency 38.8% 35.6% 35.4% 39.6% level per year 115,114 tons 125,3 tons 116,83 tons 12,827 tons reduction 1,186 tons 9,217 tons 22,473 tons (relative to WLE) GAS TURBINE WORLD: May - June 29 2

3 trol system performance and influence on engine parameters. Data were recorded with constant power at different power levels ranging from 14 to 22.5MW which cover the partial and full load operating conditions at the host test site. Emission control during testing followed the CEMS 15% oxygencorrected levels required by the Northern California Air Resources Board. The emissions data measured was concurrently compared with the on-site continuous emission monitoring system certified by the state of California. Two different sets of fuel injection nozzles were used to test limits on fuel pressure supply and available steam pressure, etc. during start-up and at full load operation. Recorded data included, CO, and unburned hydrocarbons. During initial tests, the key measurements of primary concern were and CO. Later on, the measurement was compared with fuel flow and heat rate to calculate annual production for base load operation. CLN nozzle. Injection hole areas for fuel/steam nozzle tips are larger by a factor of 2 compared to standard natural gas nozzle areas. LM25 nozzle. Standard GE nozzle was used in engine testing to compare control performance versus CLN performance. emissions vs. homogeneity. LM25 test data verify that that CLN achieves much lower levels of emission with much less steam than injected by GE to reduce. LM25 vs. steam-fuel mix. Plot of test data indicates that can be controlled by CLN steam- fuel injection at any engine power level. 4 3 Steam-fuel = 1.5 Steam-fuel = 2. LM25 Steam-fuel = CEMS data 2 1 GE steam injection Classical steam injection flame stability limit CLN test data :1 nozzle, 22.5MW 2:1 nozzles, 18MW 1:1 nozzle, 18MW 1:1 nozzle, 22.5MW 2:1 nozzle. 22.5MW 2:1 nozzle, 22.5MW, CEM data 2:1 nozzle, 18MW, CEM data 4% Homogeneity 6% 8% 1% Steam-to-Fuel Ratio GAS TURBINE WORLD: May - June 29

4 The emissions test results were surprising, says Dr. Cheng, in that at a high degree of homogeneity (above 99%) the level became totally independent of the power operating level. In the past, has always been seen as depending on load conditions. In this case, the LM25 gas turbine reached a 5 level on less than 1.8:1 steam/fuel ratio. Tests run with a standard GE steam-fuel injection nozzle at the same ratio reduced to 24. The conclusion drawn is that the degree of homogeneity has a much more dramatic impact on control than does the steam/fuel ratio. To maintain mix continuity, says Dr. Cheng, a flow rotating vane was embedded in the nozzle tip to balance the flow and insure uniform fuel distribution through the nozzle holes. A standard LM25 natural gas fuel nozzle was modified to increase the hole diameters by a factor of two to accommodate the 1.8:1 steam/fuel flow. CLN also improves efficiency When operating on DLE combustion or water injection for control, gas turbine heat rate goes up. In contrast, with CLN reduction, the heat rate goes down and gas turbine efficiency is improved. CLN helps generate savings by reducing fuel costs while building up annual credits and boosting plant power output for sale or internal use. That is a hard combination to beat. For popular gas turbine models in peaking service such as Fr 7EA, 7FA and LM6 machines, CLN technology is able to increase power output by 25-4%, reduce heat rate by 1-2%, and reduce by 15-3% (see tables). Retrofitting CLN to an existing gas turbine plant is not a big deal, according to field engineers. If an on-site steam source is available, the job can be completed over a weekend. If not, a very small heat recovery steam generator can be added that will provide sufficient steam for emission control. In that case, for a Potential retrofit performance at 59 F ambient operation. Performance calculations for Cheng Cycle with premix1.8:1 steam/fuel injection take into account gas turbine compressor surge margin, output shaft and electric generator operating limits. Calculated reduction per kwh is proportional to the CLN increase in efficiency. Frame 7EA Power Heat Rate Efficiency Reduction ISO rating 85, kw 1437 Btu 32.7% % Cheng CLN 117, kw 8413 Btu 4.6% 24% per kwh Net change 32, kw 224 Btu 7.9% Frame 7FA ISO rating 167,9 kw 9242 Btu 36.9% % Cheng CLN 2,2 kw 769 Btu 48.3% 31% per kwh Net change 53,3 kw 2173 Btu 11.4% LM6PC Sprint ISO rating 48,9 kw 812 Btu 42.6% % Cheng CLN 62, kw 6937 Btu 49.2% 15% per kwh Net change 13,1 kw 175 Btu 6.6% Potential retrofit performance on 9 F hot day. Performance calculations for Cheng Cycle with premix 1.8:1 steam/fuel injection take into account gas turbine compressor surge margin, output shaft and electric generator operating limits. Calculated reduction per kwh is proportional to the CLN increase in efficiency. Frame 7EA Power Heat Rate Efficiency Reduction Hot day rating 74,4 kw 11 Btu 31.% % Cheng CLN 114,9 kw 8375 Btu 4.8% 31% per kwh Net change 4,5 kw 2625 Btu 9.8% Frame 7FA Hot day rating 15,9 kw 9658 Btu 35.3% % Cheng cycle 182,2 kw 7197 Btu 47.4% 34% per kwh Net change 31,3 kw 2461 Btu 12.1% LM6PC Sprint Intercooled rating not available n/a n/a n/a Cheng CLN not available n/a n/a n/a GAS TURBINE WORLD: May - June 29 4

5 turnkey retrofit project, scheduled plant downtime would be less than 1 week provided the boiler is ordered 6 months ahead. Retrofit scope of supply Specialized scope of equipment supply includes the HRSG, steam/fuel manifold system, complete set of injection nozzles and computer control system. For on-site retrofit, the existing fuel manifold is removed and replaced by a CLN manifold and associated mixing equipment. Changing out nozzles is more easily done for heavy frame gas turbine installations equipped with combustor cans such as a Fr 7EA or 7FA than for an aeroderivative like the LM6 which has an annular combustor and some 3 nozzles. With frame machines, only the nozzle tips must be replaced by a CLN design. For aero type industrial gas turbines however, a new manifold leading to the complete nozzle set must be installed. The computer system can go anywhere, preferably in the control room where it can be readily integrated into the operation of the gas turbine s DCS control system. All of the equipment is supplied as prefabricated assemblies tailored to the gas turbine design. As for on-site service support, the CLN retrofit does not change gas turbine inspection intervals. But project engineers claim it has increased the parts life of hot gas path components by a factor of two compared with DLE combustion control system experience. Green technology for expanding installed peaking capacity in the U.S. by 4-7% with a 25% reduction in CO2 production Cheng CLN steam/fuel injection works to simultaneously increase power output and efficiency of gas turbine plants while reducing and CO2 site emissions. Peaking status. Most of the gas turbine peakers in service such as Fr 5, 7EA and FT4 machines are at least 2 years old and operate at relatively low 25 to 3% simple cycle efficiencies with relatively high and CO2 emissions. In the past, many of them fitted with water injection to meet 45 regulations also suffered an associated 3-4 percentage point drop in efficiency. In more recent years, they have also been required to operate catalytic converters to further reduce to 15. Under pending cap and trade legislation, gas turbine peaking plants will soon be confronted with CO2 credit restrictions and proposed limits of 5 or less on that will call for investing in a new round of expensive emission control modifications. Low cost alternative. Dr. Cheng suggests that retrofitting CLN technology to already installed peaking plants offers owners and operators a double whammy of reducing to 5 while simultaneously boosting power output by 4-7% -- with a 25-35% increase in efficiency and over 25% reduction in CO2 production. He hesitates to hazard a guess as to the price range for a CLN retrofit saying it will vary considerably with the gas turbine design, condition and site specifics. But he maintains that the cost has to be considerably less than that of a new high-efficiency simple cycle gas turbine peaking plant that must be equipped with DLE combustion and catalyst for single-digit performance. In his view CLN is a far simpler and cost effective proposition. Typically it can be retrofitted on-site in less than 1 week of downtime, does not require extensive environmental and building permit approvals, will be much cheaper than adding another gas turbine plant on the same or different site, can be operated and maintained by the same crew, and help pay for itself out of fuel savings and CO2 credits. CLN retrofits. Dr. Cheng is emphatic in pointing out that CLN steam/fuel injection is now a proven technology for both industrial combustor can and aeroderivative annular combustion gas turbine designs. The technology was first demonstrated commercially over 25 years ago on an Allison 51KH aero unit in baseload cogeneration service with a 7% increase in power output and 4% improvement in efficiency. The unit is still running today. Two more Allison 51KH units in the San Joaquin Valley were retrofitted in 1985 at Frito Lay and Hershey to stabilize transmission lines between northern and southern California. The plants have since shut down but the units are working for the irrigation district as peakers to levelize the voltage on the transmission lines. In 22, Cheng Power retrofitted an LM25 for a peaking plant on Kauai Island in Hawaai where it has been carrying the daily variable load for close to 7 years now, operating at 44.3% efficiency. That same year, two GE Fr 6Bs at an oil refinery in Southern California were retrofitted with an average return on investment of around $3 million r per year. GAS TURBINE WORLD: May - June 29 5