GAS TURBINE TECHNOLOGY
GTX100 gets off to a good start
Recent experience shows all too well that introducing new gas turbine technology is no easy business. But looking back over the last six years, the GTX100 gas turbine can be regarded as a success story.
Since the commercial launch of the GTX100 in 1997, 28 units have been sold to ten countries, and the operating units have accumulated well over 100 000 operating hours, the fleet leader having achieved over 15 000 hours.
Eleven units are now operating commercially, while the remainder are in the manufacturing or site installation phase.
The power slot 35-60 MW has been a preferred range for industrial power and cogeneration for many years, and continues to show solid growth. Booming demand in the USA at the beginning of the millennium made the market peak at more than 250 units in a single year, and was followed by the deep recession of 2002, but we anticipate a return to the long-term trend of some 100-120 units/year. An analysis made of sales during 2003 indicates that the GTX100 has consolidated its market position and improved its share to 10-15% of the 35-60MW market. Launched at 43 MW, the GTX100 has now been released for operation at 45MW following extensive field evaluation and demonstration.
We are currently achieving a twelve month rolling average of 98.5% reliability, and all contractual performance undertakings have been met.
We are also doing further development work to increase efficiency, the main items in this programme being fine-tuning of seal and blade tip clearances, a review of the engine secondary flow and a modification in the turbine stator to minimise air leakage.
To facilitate maintenance, one side of the gas turbine has been kept "clean", avoiding unnecessary piping, cabling and connections to allow for easy inspection. Borescope ports are located on the clean side for inspection of each compressor stage.
At the front of the inlet chamber is a manhole with a transparent and reinforced polycarbonate window to enable easy inspection of the compressor inlet bellmouth during standstill and operation.
The compressor casing is vertically split in the longitudinal direction, which allows half of it to be removed for easy access to the rotor and stator parts. The rotor centre line is 1.5m (5ft) above the grating, for convenient inspection.
The burner section design allows each of the 30 DLE burners to be removed individually without dismantling the machine and also enables straightforward inspection of the combustion chamber.
The gas turbine itself and the exhaust diffuser have separate mounting details, which allows a split of the engine (by removal of a flow path section) for turbine and combustion chamber removal, with the gas turbine and the exhaust diffuser fixed to their ordinary mounting details.
Field balancing capability is provided in three planes on the rotor (compressor disc No 1, intermediate shaft and turbine disc No 3), for on-site exchange of the turbine module or individual blades in the compressor or turbine.
An overhead crane is installed inside the gas turbine enclosure to facilitate maintenance and enough space is available to allow operating personnel to walk around the machine. The crane can remove modules of the complete gas turbine core through a large sliding door on one side of the package. The complete gas turbine core can be rolled out on 'skates' through the sliding door.
The GTX100 uses DDIT's "3rd generation" DLE system, as also used in the recently introduced 29 MW GT10C. A cone similar to that of the 2nd generation burner is split into four sections and equipped with a mixing tube at the exit. In commercial operation the GTX100 system has demonstrated <20 ppmvd NOx within a load range 50-100% on gaseous fuel and <35 ppmv on liquid fuels.
The current status is that the dual fuel GTX100 burners have demonstrated NOx and CO emissions better than the launched values. Our latest tests in Helsingborg, Sweden, on gas fuel, showed NOx <15 ppmv / CO <5 ppmv in the 50-100% power range and on liquid fuel NOx <35 ppmv / CO <5 ppmv in the corresponding power range. All these figures have been achieved without water or steam injection.
The key advantage of the DDIT DLE systems, however, is that there is seldom need for tuning, and combustor frequency issues affecting life have been eliminated. In fact, DLE actually helps to extend parts life due to its improved flame spread and even temperature distribution.
GTX100 projects
In June 2003 DDIT (then Alstom Power Sweden) contracted with Latvenergo, the Latvian Joint Stock Company, to supply and build the new Riga Thermal Power Plant adjacent to the existing Riga Thermal Power Plant (TPP-1) in the North-eastern suburb of Ciekurkalus. This is the biggest building project ever carried out in Latvia.
The contract covers the complete supply and construction of the Riga TPP-1 plant, including two natural gas-fired GTX100 gas turbines, a single 54 MW steam turbine and auxiliaries, two HRSGs and two gas/diesel-fired heat only boilers, which will produce some 140 MW electricity and 150 MW heat. Building work began in February 2004, and main equipment will be delivered to site as of summer 2004. The plant is scheduled for completion in readiness for the winter season 2005/6.
The existing plant was built fifty years ago (1955-60) and is still the key source of heating for Riga.
An essential part of the contract is that the function of the old plant shall be totally unimpeded during the construction of the new. Due to age and wear, however, the old plant will gradually be dismantled as the new plant comes on line. The main operating mode of the plant will be baseload and control of the district heating outlet temperature. It will also be capable of continuous controlled partial load operation of the gas turbine without supplementary firing. The plant will be fuelled by Russian natural gas and the generators connected to the 110kV grid. The efficiency of the new plant will lead to considerable environmental improvement in the city.
Moscow City
The scope of supply for Riga, and the form of the contract, are very similar to the contract signed with City Energo for Moscow City, in November 2001, for the first part of a two-stage delivery.
DDIT (then Alstom Power) was selected as a main supplier in the provision of power and heat for a new hub in Moscow, and is currently delivering the first of two CCX100-2DH plants.
New areas for business and leisure are being created in Moscow, with new buildings vying daily to dominate the skyline. One such area, a pioneer project within Russia and even Eastern Europe, is the Moscow International Business Centre (MIBC), known locally as "Moscow City". This city within a city involves the creation of 2.5 million m2 of office, hotel, retail and leisure facilities. The centre is being built on Krasnopresenskaya Naberezhnaya – the only site in Moscow capable of accommodating such a vast project – and it makes extensive use of multifunctional space and multi-storey buildings.
One of the ways in which the Customer decided to save money on the project was to form a partnership with DDIT, whereby all local on-site works were carried out by City JSC, with DDIT providing the turbine installation and supervisory services. It was not a typical contract for DDIT, since its role was purely supervisory, with no direct responsibility for the civil works.
The first phase of the project included two combustion gas turbines fired by natural gas, two HRSGs, one district heating condensing steam turbine, and one peak water heating boiler and auxiliary systems – altogether forming a complete combined cycle power plant for the production of electricity and hot water for the district heating network. The first unit was scheduled to be in operation in simple cycle in January 2003 and the second unit in July 2003, in combined cycle. In the event, the combined cycle solution was implemented
directly and the first phase of the district heating unit was operational in time for the 2003/4 winter heating season.
German cogen
Due to legislation in Germany which favours upgrade of cogeneration plants, a number of GTX100 gas turbines were ordered over a short period in 2003. The first was for Frankfurt, shortly followed by two units for Sandreuth (Nuremberg) and a single unit for Wurzburg. These projects all benefit from German government subsidies that are in place for the modernisation of CHP plants.
A single natural gas-fired GTX100 has been delivered for use in a cogeneration application connected to an existing boiler belonging to the Infraserv company at the Höchst industrial park on the outskirts of Frankfurt. In addition to the gas turbine itself, DDIT's scope of supply covered erection and commissioning while civil works and electrical installation were taken care of by Infraserv. The plant was handed over to the customer in December 2003, and a seven-year preventive maintenance contract has now come into force.
In the cogeneration application, the exhaust gases from the gas turbine are fed into the existing boiler, which has a capacity of around 300 ton/hour of high pressure steam. The gas turbine exhaust gases are then burned in the boiler combustion chamber.
Infraserv-Bayernwerk is already 50% owner of a GTX100 cogeneration plant near Gendorf. This combined cycle CHP plant entered commercial operation in the spring of 2002, providing the electricity and process steam requirements for chemical facilities. The integration of the gas turbine combined cycle system into the existing cogen plant resulted in a fuel efficiency increase from 84% to 88%, with a reduction in emissions.
In July 2003, just before the sale of its industrial turbine businesses to Siemens, Alstom was awarded a contract by N-ergie AG, Nuremberg's electrical utility, to supply a cogeneration power plant to the Sandreuth CHP plant. N-ergie AG is investing in total 90 million into the modernisation of this power plant.
Under the original contract, the project was to be led by Alstom's heat recovery and plants business, which will provide the balance of plant, the heat recovery steam generators with supplementary firing behind the gas turbines, the electrical and control system and civil works. An existing coal fired boiler is being converted to gas/oil firing. The new arrangement is a consortium, whereby Siemens, via DDIT, supplies the two natural gas-fired GTX100 gas turbines, including installation and commissioning. A 3-year service contract for the turbines is included in the scope, with future consecutive options of three and six years.
The increased capacity will enable the Sandreuth CHP plant to provide the heating needs of 25% of the Nuremberg population via a 270 km district heating network. The turbines are currently under manufacturing in the Finspong workshops, and plant commissioning is scheduled for spring 2005.
On the heels of the Sandreuth order, DDIT was also awarded a contract by Heizkraftwerke Wurzburg GmBH for a natural gas fired GTX100 gas turbine to be used in a cogeneration application in an existing plant in central Wurzburg. The contract arrangement at the time was for plant equipment to be supplied in a consortium between Lurgi Lentjes Service AG (LLS) and Siemens AG of Germany, as well as DDIT (then Alstom Industrial Turbines AB). LLS is the consortium leader and EPC contractor. The consortium is replacing an existing coal-fired boiler with a new gas turbine and HRSG to be connected to an existing steam turbine. In Wurzburg, too, commercial takeover is scheduled for spring 2005, and here, a nine-year service contract is in place.
France, Portugal, UK
Three of our earliest installations, all gas-fuelled, are in France: Arjo Wiggins (Bessé sur Braye) and Emin Leydier (Saint Valliers) are both French paper installations, while Cerestar (Lille) is a starch plant. Cerestar and Emin Leydier are both located outdoors, Arjo Wiggins is indoors. Since its commissioning in July 2000, Cerestar has run for over 12000 hours. Both Arjo Wiggins and Emin Leydier have more than 15000 operating hours to their credit.
The Solvay plant in Portugal was built at a chemical complex owned by Solvay Portugal in Povoa de Santa Iria, north of Lisbon and entered operation in August 2001. The plant is driven by a GTX100 gas turbine, producing 89 tonnes of steam per hour and 42 MW of electricity, used to power the chemical mill. Excess electricity is exported to the grid. The Solvay plant was built on a build, own, operate (BOO) basis by Energin, a specially formed company, which will supply Solvay's chemical facility with steam and electricity for a period of 15 years. As in Germany, the national energy policy favours co-generation as a means of efficiently producing electrical power with minimal environmental impact.
Two UK CHP schemes, that of Powergen CHP for Michelin, at Stoke on Trent, and that of Scottish Power for the Sappi paper mill at Blackburn, came into operation at the beginning of 2002. Each consists of a single GTX100 with an unfired HRSG, a 20 MW steam turbine and back-up package boilers. They are among the first CHP schemes to come into operation since the setting up of NETA, the New Electricity Trading Arrangements, in April 2001. Both CHP schemes are owned by large generating companies, who, under NETA, can trade the excess power outputs of the CHP schemes as components of their total portfolios of generating plant.
The Powergen CHP plant at Stoke on Trent continues to be a dedicated plant providing secure supplies of power and steam to Michelin. This is Powergen CHP's twentieth scheme to come into operation. In general, it has been the company's policy to build schemes sized to match the energy demands of the industries that they serve. Any surplus power is exported as part of their general submission into the main UK power market.
The Blackburn project represents Scottish Power's first CHP scheme in England. It has a single paper machine installed in 1995 and makes about 100 000 t/year of fine papers for magazine and book printing and personal stationery. Production is in varying batch runs of different basis weights and colours. The paper machine has to be stopped to be cleaned and set up for each new production batch, which could then run for several weeks. To accommodate this, the CHP unit is extremely flexible in operation, and can run either as a pure combined cycle, with steam supply to Sappi guaranteed by package boilers, in CHP mode, or with the gas turbine shut down and package boilers supplying steam which is the current operation mode at night time.
Meanwhile, Cebi Enerji in Turkey, an independent power producer and an affiliate of Kaptan Iron & Steel, has purchased a GTX100 to power a combined cycle power plant at its Marmara Ereglisi site close to one of Kaptan's steel works in Tekirdag. The turbine will be delivered to site in October this year. The scope of supply also includes the now standard DLE combustion system, and evaporative cooling. The GTX100 is well suited to this project because the machine is designed to achieve the highest possible combined cycle efficiency in its class. Given the expected fuel prices in Turkey, this fact was of prime interest to the customer.
A variety of applications in the USA
MMPA City of Chaska, Minnesota, is an outdoor installation, IPP-owned and run in simple cycle on dual fuel as a peaker for the community. The plant was commissioned in February 2001, and, despite some initial problems (it was the first plant to run on dual fuel) is now behaving well and has been praised by its owners.
City of Redding Municipality purchased one combined cycle unit, adding a SCONOx unit to meet the extremely tight Californian emission limits, reducing the plant emissions to the extremely low value of 2.5 ppmv.
The City of Vernon's Malburg generating station ordered two GTX100 units for combined cycle application in May 2001 for later delivery pending building permission. The project was shelved temporarily, and the turbines stored in Sweden during the waiting period. Now permissions are in place, components shipped to Los Angeles, and site erection is expected to begin in summer 2004.
Recent orders: Belgium and Sweden
Two major recent orders have been for combined heat and power applications in Belgium and Sweden.
The Siemens Power Generation Group was awarded an order in December 2003 for a turnkey greenfield plant for delivery to the Essent CHP plant, near Antwerp in Belgium. At the heart of the plant are two GTX100 gas turbines. This highly efficient industrial power plant is part of a utility centre owned by Essent Belgium (an affiliate of Essent Nederland) which will provide the customer with a reliable source of large amounts of process steam and boiler feed water to the extended Ineos Petrochemical complex. The gas-fired 45 MW turbines will be located outdoors and will be used for power generation. Erection and commissioning are included in the contract, as is an option for a 15-year service contract for the gas turbines. The turbines will be delivered to site at the beginning of 2005, and the plant is scheduled for commercial operation at the beginning of 2006.
In November 2003 DDIT won the order for the Rya combined heat and power plant, which will provide electricity and district heating for the city of Gothenburg. It comprises three 45 MW GTX100 gas turbines connected to a single 141 MW ST5 steam turbine, all supplied from DDIT AB in Finspong.
Each gas turbine drives its own heat recovery steam generator, which is equipped with supplementary firing and additional NOx reduction for stringent environmental compliance (with NOx values as low as <5ppmv after the boiler). The gas turbines will run on natural gas, with oil as backup fuel. The plant will be delivered by December 2006.
This is the first large-scale power plant to be built in Sweden for many years. It has come about as the result of the big increase in demand for electricity and district heating, which is already enjoyed by some 90% of domestic residences in Gothenburg city.
The plant will have an exceptionally high total efficiency of 92.5%, and provide some 260 MW of electricity to the grid. During the summer, residual heat from local refineries will be sufficient to cover the heat demand. If needed, the plant can also run during the summer months in condensing mode, ie independently of the district heating network. A long-term service agreement is in place to achieve optimal profitability over the plant's life cycle by ensuring high reliability in both heat and electricity production.
Environmental permission was given on 26 January and the project is now officially underway. The Rya plant is a so-called "utilisation-optimised" power plant. As energy tax is levied in Sweden, the economy of a power plant, in terms of investment and operating costs, and particularly the degree of total utilisation, are determining factors in the choice of plant configuration.
GTX100 projects to date
GTX100 - the basic data
City of Chaska GTX100 installation
GTX100 gas turbine
GTX100 burner
Cutaway of the GTX100
GTX100 in the workshop at Finspong