The Turkish electricity supply industry is changing to accomodate local power developments. Wärtsilä’s 50DF diesel plants have been chosen to provide power and heat for one of the country’s largest business centres.
Ufuk Berk, Wärtsilä Enpa Dis Ticaret A.S., Turkey
In 1999 the Turkish government introduced a policy of great importance to the country’s power production and distribution, which included special incentives that allow private entrepreneurs to build and operate their own power plants. That policy provided the impetus for the Manisa Organised Industrial Park (MOSB), one of Turkey’s largest business centres, to build its first power plant for its heat and power needs.
During August 2004, MOSB awarded a contract to Wärtsilä of Finland for an 84.8 MWe replacement and extension of the existing diesel power plant at Manisa. The project sees the first power plant installation of Wärtsilä 50DF generating sets, while the extension will be made up of Wärtsilä 34SG sets. The new plant will allow a change of fuel from heavy fuel oil to natural gas.
In 1999, Wärtsilä supplied a 54.3 MW baseload plant to Manisa with three Wärtsilä 18V46 diesel generating sets to meet the heat and electricity demand of MOSB’s industrial park, which houses some 115 companies from a range of industries, including paper, electronics, furniture, chemicals, textiles and food. Under the new contract, the existing diesel generating sets are to be replaced by three Wärtsilä 18V50DF sets, each with an electrical output of 16 638 kWe. In addition, four Wärtsilä 20V34SG generating sets will be installed, each giving 8730 kWe. The equipment is being supplied under an engineering, procurement and construction (EPC) contract.
The plant will have a high overall efficiency and be very flexible in operation. High energy efficiency will be ensured by the use of waste heat recovery to supply hot water and steam to the industrial park. The total steam production capacity will be around 40 tonnes/h at a pressure of 14 bar. Hot water will be fed into the district heating system of the industrial park, through a heating network with a pipeline length of 6 km.
Flexibility will be provided by the use of two sizes of generating sets and the dual-fuel capability of the larger generating sets. Whereas the existing engines burn heavy fuel oil, the new engines will all run on natural gas which is piped to the site. The 50DF engines are dual-fuel engines that have a pilot injection of a small quantity of light fuel oil to ignite the gas fuel. They can also switch over to operate solely on fuel oil in the event of an interruption in gas supply. The 34SG engines are pure gas engines with spark ignition of the gas fuel.
Figure 1. The Manisa Organised Industrial Park is one of Turkey’s largest business centres to build its own power plant
When the engines are running on natural gas, the plant will be able to meet the environmental regulations without using the existing deSOx system, which was installed with the original heavy fuel-burning engines for removing sulphur oxides from the exhaust gases. If the operator should want to switch the 50DF engines to heavy fuel oil, the deSOx will be put back into operation.
The installation of the plant will require careful organisation. The existing generating sets are to be replaced within seven months and the time span will only add to the pressure of having to exchange the sets while keeping two running at all times. The 18V50DF generating sets were delivered in October 2004 and the 34SG sets will be delivered in January 2005. The construction time of the power plant extension is expected to be eight months.
The business drivers for engines
The main reasons for MOSB’s decision to order the plant are the low price of natural gas compared to heavy fuel oil (HFO) and the easy replacement of the 46 engines by the new 50DF without losing much time, keeping down time at the existing plant to a minimum. The high efficiencies of the 50DF and the 34SG persuaded MOSB from their original intention of installing gas turbines.
By swapping engine by engine, the plant will be partly operating on HFO with the old engines, while the new 50DFs are being commissioned. Therefore the target is to have two engines continuously running while swapping work continues on the third engine. For the extension plant, which will have four 20V34SG engines, the main driver is the increase in electricity and hot water demand from the park.
Wärtsilä 50DF Manisa
The power plant at Manisa is the first to install Wärtsilä’s 50DF, a 50 cm bore dual-fuel engine with an output of 17 MW in 18-cylinder configuration. It has been designed to provide high output combined with fuel flexibility, low emissions, high efficiency and reliability. It is a four-stroke dual-fuel engine that can be run on natural gas or light fuel oil (LFO) and, with certain modifications it can be run on heavy fuel oil. It can be switched from gas to LFO and vice versa during operation.
The engine is manufactured in configurations from 6L up to 18V, giving 950 kW per cylinder and a maximum mechanical output of 17 100 kW. The engine speed is 500 or 514 for use with 50 or 60 Hz applications. The 50DF engine has a maximum thermal efficiency of 47 per cent, which is considerably higher than any other gas engine on the market.
The engine’s design concept is based on the Wärtsilä 46 diesel engine, which has been well established in the power plant and marine power markets since the late 1980s. The dual-fuel technology used is the same as in the Wärtsilä 32DF.
The 50DF operates on the lean-burn principle in which the mixture of air and gas in the cylinder has more air than is needed for complete combustion. This lean-burn method of combustion reduces peak temperatures and therefore NOx emissions; efficiency is increased and higher output is reached while avoiding knocking.
Combustion of the lean air-fuel mixture is initiated by injecting a small amount of LFO (pilot fuel) into the cylinder. The pilot fuel is ignited in a conventional diesel process, providing a high-energy ignition source for the main charge. To obtain the best efficiency and the lowest emissions, every cylinder is individually controlled to ensure operation at the correct air-fuel ratio with the correct amount and timing of pilot fuel injection.
An advanced automation system has been developed to control the entire engine’s functions. This system allows optimum running conditions to be set independent of the ambient conditions or the fuel. The automation system, controlling the 50DF engine, is a microprocessor-based distributed control system which is mounted on the engine itself.
This computer-based system also handles the start and stop sequences, engine safety systems and transfers between gas and diesel mode operations. The control of the process is so accurate that transfers between the gas mode and the diesel mode can be done at any load. The system’s various electronic modules are dedicated and optimized for specific functions, and they communicate with each other via a CAN databus.
Figure 2. Three 18V50DF sets are to be used, each with an electrical output of 16 638 kWe.
The 50DF’s control system also provides the power plant operator with a number of advantages, including easy maintenance and high reliability, thanks to rugged engine dedicated connectors and prefabricated cable harnesses. The new control system allows for easy interfacing with external systems via the databus, plus high flexibility and ease of customising as well as built in diagnostics for simple trouble shooting.
Meeting NOx emission regulations
Around the world stringent emission regulations are increasingly demanding the reduction of NOx emissions from power plants. It is now essential for power plant equipment manufacturers and suppliers to offer enhanced emission controls to their customers. In an internal combustion engine this means controlling peak temperature and residence time, which are the main parameters governing NOx formation.
In the case of the 50DF engine, the air-fuel ratio is very high (typically 2.2). Since the same specific heat quantity released by combustion is used to heat up a larger mass of air, the maximum temperature and consequently NOx formation are lower. The mixture is uniform throughout the cylinder since the fuel and air are premixed before introduction into the cylinders, which helps to avoid local NOx formation points within the cylinder.
Figure 3. Two engines will be kept on line during the conversion.
As a result of this feature, NOx emissions from the 50DF are extremely low and comply with the most stringent NOx emissions legislation in place today. The engine is optimised for NOx emissions of 500 mg/Nm3 at five per cent O2, dry (equivalent to 190 mg/Nm3 at 15 per cent O2, dry) and fulfils the German TA-luft standard for operation on natural gas.
Future of 50DF
In 2004, Wärtsilä received an order from Hyundai Heavy Industries of Korea to supply four sets of 50DF engines to power a series of 155 000 m3 dual-fuel electric LNG carriers, with an option of four more engines. Another dual-fuel electric LNG carrier, the 75 000 m3 Gaz de France Energy, is equipped with four 50DF with a combined power of 22.8 MW.
More units are due later in 2005: the 154 000 m3 dual-fuel electric LNG carrier Provalys will be delivered towards the end of the year, equipped with three 50DF engines providing 39.9 MW. Sister ship Gasleys will also be powered by three 50DFs, ordered in December 2004.