Wärtsilä Corporation has been awarded two separate contracts to supply natural gas-fuelled Wärtsilä 50DF engines for two captive power plants in Pakistan. The 50DF is the most powerful dual-fuel engine on the market today and provides for high-efficiency power generation from natural gas. The two contracted plants will have the first 50DF dual-fuel engines in Pakistan.
One contract, received in October 2005, is for an 18-cylinder Wärtsilä 50DF engine to be installed in an extension at the Maple Leaf Cement Factory in the Punjab, Pakistan. This 16.5 MWe set will operate on natural gas, with heavy fuel oil as the back-up fuel. The plant is scheduled to be in operation in the autumn of 2006.
Similarly, an 18-cylinder Wärtsilä 50DF engine is to be supplied for a power plant at the cement works of D.G. Khan Cement Co in Khairpur in the Punjab, Pakistan. D.G. Khan Cement Co is a member of the Nishat group of companies with businesses including cement, textiles and banking. The set will also operate on natural gas with heavy fuel oil as the back-up fuel. The contract was awarded in November 2005, and the delivery is due in September 2006.
In the past year, there has been a surge in demand for cement in Pakistan, and there are a number of projects there to increase cement-making capacity through both expansion of existing cement works, such as Maple Leaf Cement, and new plants, for example the D.G. Khan Cement Khairpur project. With these developments, there is a corresponding need for additional power to supply the new cement-making capacity, a large demand that cannot be met by the national grid.
For both orders, important factors in the choice of engine were the need for a reliable, cost-effective electricity supply to the cement making process, with flexibility in the choice of fuel. Fuel flexibility is an important factor in Pakistan as the year-round supply of natural gas cannot be guaranteed. The gas supply is not sufficient to meet the high demand in winter months. Furthermore operating an independent power plant for a cement works is advantageous when starting the large motors commonly used in cement mills with their sudden high starting currents. These requirements are all ideally met by the Wärtsilä 50DF.
The Wärtsilä 50DF lean-burn dual-fuel engine has become popular for power plant installations in a number of countries. It is the most powerful gas-burning engine on the market today and has both low emissions and high fuel efficiency which make it a competitive alternative to gas turbines. It is available with up to 18 cylinders giving up to 16.64 MWe in continuous base-load operation with a heat rate of 7608 kJ/kWh which is equivalent to an overall thermal efficiency of 47.3% at the busbars.
When running on natural gas, the gas fuel is supplied at a low pressure (less than five bar) and the engine operates on the lean-burn Otto process. Gas is admitted into the air inlet channels of the individual cylinders during the intake stroke to give a lean, premixed air-gas mixture in the engine combustion chambers. Reliable ignition is obtained by injecting a small quantity of diesel oil directly into the combustion chambers as pilot fuel which ignites by compression ignition as in a conventional diesel engine. This “micro-pilot” injection uses less than one per cent of the fuel energy being required as liquid fuel at nominal load. Electronic control closely regulates the “micro-pilot” injection system and air-gas ratio to keep each cylinder at its correct operating point between the knock and misfiring limits.
In the diesel mode, the engines run on liquid fuel oil such as heavy fuel oil or light fuel oil as a conventional diesel engine. The engines are fully capable of switching over from gas to back-up liquid fuel instantly and automatically should the gas supply be interrupted or in the event of any other alarm, while continuing to deliver full power. When the situation returns to normal it is then possible to switch back to gas mode.
Notes to the editor:
Wärtsilä is a leading provider of power plants, operation and lifetime care services in decentralized power generation.
The company provides power plants for baseload, intermediate, peaking, standby and combined heat and power applications as well as solutions for oil pumping. The product range comprises gas- and oil-fired power plants with outputs from 1 MW to 300 MW, biopower plants with outputs from 1 to 5 MWe and biothermal plants for 3–17 MWth.
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For further information, please contact:
Public Relations Manager, Power Plants
Wärtsilä Finland Oy
Direct tel: +358 10 709 1456
Direct fax: +358 10 709 1425