Power Plant
... overall efficiency of 57.5%. (Source 5) The Veazie power plant utilizes two GE Frame 7FA+ Enhanced Combustion Turbines, two ABB Heat Recovery Steam Generators, and one GE Steam TurbineGenerator. The two gas turbines generate more than two thirds of the plant’s 520-megawatt capacity. The exhaust from the combustion, which escapes up a stack in traditional fossil fueled power plants, is passed through heat recovery steam generators to create high-pressure steam to drive a steam turbine generator. After passing through the steam turbine the expanded steam flows through the condenser where it looses its heat and is condensed back to water form. The condensate then flows back to the HRSG where it is vaporizes back into high-pressure steam. Thus, implementing the use of combined cycle power to increase the plant’s efficiency. To cool and condense the steam, cooling water is brought in from the Penobscot River at 2000 gallons per minute. About 1800 gpm leave the cooling tower in the form of steam and the remaining 200 gpm goes back to the river. This accounts for 95% less cooling water used from the Penobscot than the former oil-fired plant. The gas turbines are fueled with natural gas. Natural gas burns cleaner than coal or oil fired plants, contributing to lower emissions of NOX, CO, and NH3. With the Veazie plant there is a 95 percent reduction in air pollution per megawatt-hour than with the old oil-fired plant. (Source 3) The plant is equipped with a Dry Low NOx combustion system along with a SCR, which reduces NOx to 3.5 ppm and less. (Source 5) The average emissions produced by the natural gas plant are: O2= 13.9%, NOX= 2.50 ppm, CO= 1.25 ppm, and NH3= .04 ppm. (Source 5) Although natural gas is a relatively expensive hydrocarbon fuel compared to industrial grade oil and coal, the capital cost of building a natural gas power plant is much lower than the cost of building a nuclear or coal plant. (Source 2) The Veazie plant is supplied with natural gas via. the Maritimes & Northeast Pipeline from a connection with main pipeline that stretches from Sable Island, Nova Scotia, through Maine to Massachusetts. From the main line running through Eddington, a 1.1-mile long twelve-inch lateral pipeline tunnels beneath the Penobscot River and emerges in Veazie. (Source 4) The pipeline supplies 100 million cubic feet of gas per day to a meter station adjacent to the plant. Duke Energy, being a pipeline owner is entitled to forty percent of the gas in the pipeline. (Source 5) The pipelines transmission of gas eliminates storage tanks, emergency spill contingencies and the shipment of oil by ships and trucks. Each gas turbine weighing 377,000 pounds is rated at 172 megawatts, hydrogen cooled. The 7FA+ gas turbine engines are of a single shaft design. Each drive a generator attached to the compressor end by a rigid coupling. The running speeds of the machines are at 3600 rpm. The engines have a compressor pressure ratios of 15.5:1 with an inlet airflow of 3,347,000 lb/hr and an exhaust flow of 3,569*10^3 lb/hr. The compressors consist of eighteen stages while the turbines have only three stages. The...