A landmark for private power in Mexico20 July 1998
The first unit at Samalayuca II in northern Mexico entered service in June. The 700 MW project is currently running ahead of schedule and is expected to be completed by the end of this year. It uses the most advanced combined cycle technology so far installed in Mexico, and is also the country's first large-scale private power project.
The Samalayuca II combined cycle plant in northern Mexico has moved from groundbreaking to commercial power in just over two years – a significant achievement for a complex project that required four years to complete legal, regulatory and financial negotiations.
Construction started in June 1996, and the first of the plant's three combined cycle units entered full commercial service on 5 June this year. The second unit is currently in its commissioning phase, with commercial operation scheduled for the third quarter. Unit 3 is scheduled to come on line by the end of the year. At that point, Samalayuca II, the first large-scale private power project in Mexico, will be producing 700 MW of power to support the industrial and residential growth of northern Mexico.
The plant is located adjacent to the existing Samalayuca I power plant just south of Ciudad Juarez, Chihuahua, and approximately 50 km south of El Paso, Texas. Samalayuca I is an oil- and gas-fired plant comprising two 158 MW units and is owned by Comisión Federal de Electricdad (CFE).
Samalayuca II will be operated by CFE under a 20-year contract, with ownership of the plant being transferred to them at the end of the lease period. The current owner of the plant is a consortium led by GE Capital, which also includes InterGen, an affiliate of Bechtel Enterprises and Shell; El Paso Energy; and ICA Fluor Daniel of Mexico.
A pipeline that is delivering natural gas from the US to the Samalayuca II site was built under an international partnership between El Paso Energy and PEMEX, the Mexican oil and gas company. About 37 km of the 73 km pipeline is in Mexico, and represents the country's first privately owned and operated natural gas pipeline.
In December 1992, CFE awarded the Samalayuca II project to the GE-led Engineering, Procurement and Construction (EPC) consortium made up of GE Power Systems, Bechtel Enterprises and ICA Fluor Daniel. GE Power Systems provided the major plant equipment as well as conceptual design; Bechtel provided detailed, overall plant design, engineering and management services; and ICA Fluor Daniel handled plant construction and national procurement.
Negotiations to complete the project arrangements were complicated by two major factors. First, this was the first major project developed under Mexico's newly adopted privatization laws. Second, there was a significant level of uncertainty in the Mexican economy triggered by the devaluation of the peso in 1994.
CFE, the Mexican government and the consortium members worked their way through all of the obstacles, however, and the final project documents were signed on 3 May, 1996. Financial closure was on 28 May, 1996, with the groundbreaking a week later.
It was a long and complicated learning process for the participants, but the successful completion of the negotiations is expected to pave the way for other private power developments in Mexico. Indeed, GE announced earlier this year that it will supply 7FA gas turbine-generators, spare parts and services for two 150 MW simple cycle facilities owned and operated by CFE. These will be at Rosarito, near Tijuana in northern Mexico, and at Rio Bravo, near Matamoris.
GE Capital's Capital Markets Group and InterGen arranged $515 million in debt financing for Samalayuca II, consisting of long-term loans from the Export-Import Bank of the US, the Inter-American Development Bank, and a commercial bank group led by Citibank of New York and including Union Bank of Switzerland, ABN Amro of the Netherlands and Dresdner Bank AG of Germany. In addition, consortium members provided an equity investment of $132 million.
Once all of the project negotiations were completed, the EPC consortium moved forward quickly with plant construction and equipment shipments, leading to commercial start-up of the first unit approximately three months ahead of the contract schedule. Current progress on units 2 and 3 means that they will also enter service early.
Samalayuca II features the most advanced combined cycle technology installed to date in Mexico. The plant consists of three multi-shaft GE STAG (Steam and Gas) 107FA combined cycle units, each including a GE MS7001FA advanced technology gas turbine, a steam turbine and two generators.
Since the F advanced technology was introduced in 1986, GE's F-series gas turbines have accumulated nearly 1.3 million hours of commercial service in power plants around the world. The 60 Hz 7F was introduced at 135.7 MW, but has undergone a series of uprates, and the 7FA now can produce 167.8 MW when firing natural gas at ISO conditions.
GE 7FA machines installed at Korea Electric Power Corporation's Seoinchon plant were the first gas turbines in the world to reach 55 per cent gross thermal efficiency in combined cycle operation. The F machines achieve greater operating efficiency than other technologies by firing at higher firing temperatures of 2350°F (1288°C). The higher firing temperature requires first stage turbine buckets with a cooling arrangement derived from GE's CF-6 aircraft engine, and the use of a patented nickel alloy.
The first stage cooling arrangement has been progressively developed as the F machines have been uprated, mainly through increasing use of film cooling. The original MS7001F first stage bucket cooing system was based on the CF-6 arrangement but did not include a film-cooled leading edge. The current buckets now use the full CF-6 system, complete with leading edge film cooling.
The bucket material used on the stage 1, 2 and 3 buckets on the 7FA and 9FA turbines is directionally solidified GTD-111, a nickel alloy with 14 per cent chrome, 9.5 per cent cobalt and 4.9 per cent titanium, as well as tungsten, molybdenum, aluminium and 2.8 per cent tantalum.
Selection of 7FA turbines for Samalayuca II was based on several factors:the 7FA is proven technology, which was a requirement of the CFE specification, and also a major factor for the owners' consortium as it affected the 'financeability' of the plant the power and heat rate values that were guaranteed were well suited to the site characteristics the 7FA was deemed the engine of choice to meet the emissions standards imposed by the financing institutions the 7FA is user-friendly technology, is well adapted to the combined cycle mode being used, and has a flexible control system.
Dual fuel capability
The 7FA gas turbines can fire on either natural gas, the primary fuel at Samalayuca II, or on diesel fuel oil, the backup fuel. The units can be started on either fuel and switched automatically from natural gas to diesel fuel oil on low gas supply pressure, or from diesel fuel oil to natural gas by operator initiation.
Each of the gas turbines drives a hydrogen-cooled, synchronous, 7FH2 generator. The generators are equipped with a Speedtronic Mark V control system, a static starting system (two for all three units), fire protection system, standard enclosures, lubricating oil systems, heat exchangers and a single water wash system for all three units.
The unfired, three-pressure, reheat, natural circulation heat recovery steam generators (HRSGs) feature horizontal gas flow and vertical fin tubes in all sections. Each HRSG is a fully integrated system consisting of all required ductwork and boiler components. Specially designed to operate with the 7FA gas turbines, the HRSGs match the turbines' operating characteristics to optimize efficiency and steam production. The HRSGs were provided by Aalborg Keystone, formerly Zurn Industries.
Each steam turbine is a straight condensing, reheat, opposed flow, axial exhaust unit. Reheat cycles are commonly used with combustion turbines such as the 7FA which operate with sufficiently high firing temperatures. The steam turbines are equipped with Mark V redundant control systems, lubricating and hydraulic oil systems and motor-driven turning gear.
GE's STAG combined cycle steam turbines are matched to the exhaust energy of the gas turbines and HRSGs. Flexibility is built into the design, to allow the steam turbine to be optimized for site-related parameters such as condenser pressure, which in the case of Samalayuca II is relatively high due to the use of a direct-acting dry-cooled condenser system.
The plant is connected to CFE's electrical distribution grid through a 230 kV switchyard, with transmission lines running north and south to the cities of Juarez and Chihuahua.
Samalayuca II will operate in accordance with all applicable standards set by the Mexican government and the World Bank. The gas turbines are equipped with GE's advanced Dry Low NOx combustion systems for emissions control to achieve NOx levels of 25 ppm or less on natural gas, and less than 42 ppm on fuel oil using water injection.
Water for the project is supplied by new wells drilled by CFE, as well as from the existing wells that supply Samalayuca I. With water being in short supply in the region, the plant employs several water-saving features that will result in average consumption of around 6.3 l/s and peak consumption of 60 l/s. In addition to the use of the dual-mode Dry Low NOx combustors on the gas turbines, the dry condenser cooling system used on the steam turbines also helps minimize the use of water.
Benefits for Mexico
Marking the first time that project financing techniques were adopted for private sector construction of power plants in Mexico, Samalayuca II sets an example for the continuing development of independent power projects in the country. Since it is privately financed, Samalayuca II frees up funds in Mexico for other infrastructure projects as well as for health and education.
By adding 700 MW of electrical power to the CFE grid, the new plant supports the economic growth of the state of Chihuahua, Much of the power will be used in the nearby city of Ciudad Juarez, which has a population of more than one million and more than 300 factories. Samalayuca II will also make a significant dent in Mexico's need to add 12 000 MW of new power by 2006.
Samalayuca II is bringing other benefits to the local economy through the purchase of local goods and services, the employment of about 1500 workers during the plant construction, and the hiring of 85 permanent workers to help operate the plant.
The long and complex project is reaching a highly successful conclusion. Using advanced technology and the latest emissions control systems, the plant is a showcase for the clean and efficient production of electrical power.