With a capacity of 21 000 tons per day, Lucky Cement Ltd. is the largest cement producer in Pakistan. During the first part of 2007, Wärtsilä Corp. was awarded contracts by Lucky Cement to convert their complete heavy fuel oil (HFO) burning power plant to operate on natural gas.
Here is a view of the Lucky Cement power plant located in Pakistan’s North-West Frontier Province. The plant’s ten Wärtsilä engines will be converted from HFO to dual-fuel with gas as the main fuel.
The power plant at the Lucky Cement’s cement works, located in Pakistan’s North-West Frontier Province,is equipped with ten Wärtsilä generating sets having a combined output of some 72 MWe. There are three sets powered by Wärtsilä 12V46 engines, each having operated for about 10 000 hours, and seven with Wärtsilä 18V32 engines, each with about 50 000 running hours. At present these are all burning heavy fuel oil.
Wärtsilä was awarded a contract in May to convert six of the Wärtsilä 18V32 engines to operate as dual-fuel (DF) engines burning mainly natural gas. Within a month’s period, Lucky Cement Ltd. also decided to have the seventh and last of the Wärtsilä 18V32 engines converted to DF. They will each generate 5390 kWe when running on natural gas with a pilot injection of light fuel oil.
In July 2007, Wärtsilä was again awarded a contract, this time to convert the three Wärtsilä12V46 engines to Wärtsilä 12V50DF. Lucky Cement has chosen dual-fuel conversion to make the power plant more environmentally friendly, with cleaner exhaust gases. It will reduce NOx and CO2 emissions to comply with existing environmental regulations. Dual-fuel conversion will also give greater flexibility in the choice of fuels used.
“They will have the ability to switch to running on light fuel oil alone should there be a break in natural gas supplies or during the winter time, when the gas supply cannot be guaranteed,” said Leif Enlund, manager, Service Projects, Wärtsilä. “Generally there is also an interest from the government to have plants running on gas fuel.”
When an installation is originally designed, capital investment is focused on expected energy trends and known environmental regulations. All along its lifetime, generally over 25 years, fuel prices vary and environmental requirements become more stringent. It often affects the profitability of the investment and could lead to a different load profile, need to invest in emission control technologies or change to another fuel.
An engine gas conversion project in progress. The amount of work depends on the type and version of the engine.
Conversions are a way to get back to profitability while respecting regulations. “The conversion of each Wärtsilä 18V32 engine is planned to take 50 days,” said Enlund. “The conversion work is only allowed to be performed on one engine at a time. During this period parts like cylinder heads, camshaft, and possibly the pistons and connecting rods, will be replaced. The dual-fuel system will use the same injector as has been used so far in the liquid-fuel version, but the electrical control system will be new.”
The first converted generating set will return to operation in February 2008, and the plant, consisting of the seven 18V32 engines, will be handed over after conversions by the beginning of the fourth quarter 2008.
Upon completion of the conversion of the seven Wärtsilä 18V32 engines, a more challenging 12V50DF conversion will follow. During this time, the complete engine will be dismantled and basically all engine components except engine block and crankshaft will be renewed. The most time-consuming work will be the machining of the engine block to fit the increased diameter of the cylinder liner from 460 mm to 500 mm.
Wärtsilä will have three to five expatriates from Wärtsilä at site during the conversions and the rest of the crew will be from the local Wärtsilä office in Pakistan. The power plant is already covered by a maintenance agreement, whereby Wärtsilä is responsible for carrying out the routine maintenance of all engines.
Wärtsilä has had a maintenance agreement for the original seven Wärtsilä 18V32 engines since the power plant was commissioned in 1996. The three Wärtsilä 12V46 engines were installed in 2005 and are also covered under a maintenance agreement.
“We have, to date, converted around 30 engines from HFO to gas or dualfuel operation,” says Enlund. “Examples are four units in Pakistan, three units in Portugal, three in Turkey, one in Germany and as many as 16 units in the same plant in Indonesia. Also, plants in India and in South America have been through conversions to gas.”
Regarding the cost of a conversion Enlund said, “The cost is very much dependent on the version of the engine, and versions have varied over time. Payoff can be less than two years. The cost can be estimated to €140 to €200/kW, and for that price the power plant owner will get a modern overhauled engine operating on gas — with the latest control and automation technology.