Microturbines and Methane
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  CLEAN, RELIABLE ENERGY: Based on jet engine technology, microturbines use high-nickel superalloys for strength and corrosion resistance at high temperatures. Features include low maintenance, low emissions and digital power conversion. |
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ENERGY & SUSTAINABILITY:
Nickel magazine, Mar. 01 -- on measures to reduce greenhouse gases and consumers shoulder the spiraling
cost of fossil fuels, alternative technologies are gaining greater prominence. Among the more promising
alternatives are portable and efficient microturbines that consist largely of nickel alloys.
When microturbines burn methane gas produced from decomposing waste in landfill sites, they provide more than
an alternative source of electricity; they also reduce emissions of methane, a greenhouse gas that
contributes to global warming.
In Canada, Suncor Energy Inc. has signed a five-year agreement with the Ontario environmental firm Conestoga Rovers and Associates (CRA) to develop landfill sites for the purpose of generating electricity from methane gas that would otherwise escape into the atmosphere. CRA is looking at 30 to 35 sites, and Suncor expects to spend about $60 million to develop six of them. The sort of equipment required for generating power at landfill sites includes large turbines, microturbines and reciprocating engines. Microturbines are considered especially useful at small or remote sites.
According to CRA, about 25% of Canadian landfill sites are being tapped to produce roughly 100 megawatts of electricity. These sites are also reducing carbon dioxide emissions by six million tonnes a year, according to CRA's project manager Rick Mosher. "This figure could be doubled if the resources, money and the market were put in place [for more landfill site development]," he says.
At oil fields, microturbines produce electricity from waste hydrocarbon gas, and this electricity is used to run oilfield equipment. But they also provide a low-emission alternative to simply flaring off natural gas, which is inefficient and produces toxic pollutants.
The Capstone Turbine Corporation in California, U.S.A., manufactures 30-kilowatt and 60- kilowatt microturbines weighing 189 and 608 kilograms, respectively. A high percentage of the components Capstone manufactures for its turbines are made from nickel alloys to ensure strength and resistance to corrosion at high operating temperatures. For example, nickel alloy N06002 and other alloys are used in the combustion chamber, where sometimes corrosive gases burn at temperatures as high as 870°C. The spinning turbine is made of N07713, and the main rotor shaft consists of N07718. The recuperator housing, which recycles hot gases to the combustion chamber, is made of austenitic stainless steels S31000 and S34700. Other components made from nickel alloys include the rotor, turbine nozzle, exhaust, thrust shaft, heat shields and fuel injectors.
These units are used for many applications, including landfill and wastewater treatment sites and oilfields. Capstone sold its 1,000th microturbine in late 2000.
One of its turbines has been undergoing field trials in the Puento Hills landfill site (the world's second-largest), just east of Los Angeles. Not only does it burn the impure landfill gas; its nitrogen oxide emissions have been measured at just 1.3 parts per million. Other Capstone microturbines are being used by PanCanadian Petroleum Ltd. to generate electricity from oil field natural gas.
Each microturbine can burn up to 255 cubic metres of natural gas a day and are versatile in that they can burn various fuels, including sweet natural gas, propane, and sour gas with up to 7% hydrogen sulphide, provided a scrubber system is used.
Photo: Capstone Turbine corp. Guilio Buttino
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Keith Field, director of communications |
