New rating for industrial gas turbine
Siemens has recently announced a new rating for its SGT-800 gas turbine, the largest of its industrial gas turbines.
The new rating is the result of a two megawatt (MW) increase which will reduce life cycle cost for open cycle, CHP and combined cycle plants.
Launched in 1997 as a 43 MW machine under the name GTX100, the SGT-800 currently produces 45 MW with an electrical efficiency (ISO) in open cycle of 37 per cent. The new rating is 47 MW at 37.5 per cent efficiency. The combined cycle performance has also improved from 64 MW with an efficiency of 53 per cent to 66 MW with an efficiency of 54 per cent with dual-pressure heat recovery steam generator (HRSG).
Underlying this enhancement is a proven operating record since commercial introduction and a comprehensive testing program, resulting in redistribution and saving of cooling air. During a comprehensive “hot section mapping” carried out in 2003, over 1900 thermo-crystals were attached to the hot gas path components, and thermal paint, thermocouples and pressure taps were used to verify the temperature and pressure distribution in the turbine area. The result showed that cooling air could be redistributed and saved, giving a more uniform temperature profile for some hot section components, thus reducing stresses due to temperature gradients. This saving, together with a 1.4 per cent additional airflow from the compressor, is now used to increase power and improve efficiency.
Four components in the gas turbine have been modified, but fully interchangeable between the 45 MW and the 47 MW rating. The combustor exit temperature, which impacts hot section component life, will remain the same. The enhancement has been running in one single plant since November 2006 (5500 Equivalent Operating Hours, June 2007).The plant operates in continuous duty on natural gas and has only been stopped for washing, filter exchange and a scheduled follow-up borescope inspection at 4100 EOH. The results of the inspection were in line with all expectations.
The enhancement can be offered to new and existing customers and orders are already booked by both categories. It is part of the Siemens product strategy for SGT-800 to maintain the leadership of industrial gas turbines in its class and to deliver reliable and environmentally friendly equipment to the world market.
The first two new units of SGT-800 gas turbines with 47 MW output will be delivered to Condamine in Queensland, Australia. Siemens' customer is Austrian Energy & Environment (Australia), who are EPC contractor for a 140-MW turnkey combined cycle plant to be built in Queensland, Australia, for end customer Condamine Power Station Pty. Ltd. The tiny town of Condamine is located 373 km west of Brisbane on the banks of the Condamine river, best known for its fishing. Condamine is rugby mad with no fewer than three rugby teams, which is quite an achievement for a town with 85 residents! Power from the plant will be used for grid support, selling power both into the national power pool, and under contract to various off-takers.
The SGT-800 gas turbines are due to come on line in simple cycle in February 2009 after a scheduled construction phase of 21 months, converting to combined cycle some eight months later. Not only are these the first SGT-800 turbines to be delivered to Australia, as well as the first at the new rating, they are also the first to be fired on coal seam methane (CSM) fuel gas. After twenty years, ownership of the plant will transfer to Queensland Gas Company (QGC), the largest coal seam gas developer in Australia. QGC has developed an enormous coal seam gas resource close to existing infrastructure in southern Queensland where it expects significant future growth. With the construction of Condamine Power Station due to start this year, QGC plans to enter the Australian National Electricity Market in 2009.
The SGT-800 is robust and simple, designed for high reliability and low emissions while delivering high efficiency in both combined cycle and in simple cycle applications. The reliability factor (12 month rolling average) is an impressive 99.4 per cent, while the corresponding availability factor is a strong 96.3 per cent.
The machine is of single-shaft design driving the AC generator from the cold end via a double helical gearbox. Starting is provided by an electrical motor connected to the gearbox.
The 15-stage compressor features a welded rotor design with Cr-steel blades for high reliability. Three rows of variable guide vanes are fitted to control the inlet airflow. The combustion section has an annular combustor with 30 burners of the 3rd generation DLE design offering dual fuel dry DLE operation down to 15 ppmv NOx (at 15 per centO2) and 5 ppmv CO on natural gas and 42 ppmv NOx and 5 ppmv CO on diesel oil no 2 in the 50-100 per cent load range. Each burner can be removed individually for inspection without dismantling the machine. The three-stage turbine is bolted onto the stub shaft and features advanced aerodynamics with single crystal blades in the first rotating blade row as well as clearance control by stator cooling. The turbine exhausts into a straight axial diffuser section, which minimises losses in combined cycle applications.
The unit is designed for easy on-site overhaul and low maintenance cost. The hot section (combustor system and turbine module), and the compressor can be maintained without moving the core engine from its supports inside the gas turbine enclosure.
A total of 59 units of this high performing gas turbine have been sold since its introduction, for a wide range of applications and duties around the world. Ten units will operate in simple cycle mode, while 18 units will be used for cogeneration. No fewer than 31 units have been selected for combined cycle operation, where the inherent advantages of the SGT-800 are particularly outstanding. Installed applications are as varied as CCPP, CHP with and without supplementary firing in district heating, pulp and paper, chemical, food, tires and steel industries, as well as simple cycle peaking.
The 26 units which have so far entered commercial operation have accumulated more than 425,000 operating hours, with the fleet leader currently operating at over 41,500 hours.
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