Keystone Generating Station

The Keystone Generating Station is a 1,711 MW baseload coal-fired power plant located on roughly 1,500 acres (610 ha) in Plumcreek Township, southeastern Armstrong County, Pennsylvania near Crooked Creek, just west of Shelocta, Pennsylvania.

The plant was built in 1967 and expanded in 1968. It has had a number of improvements made over the years to reduce the level of environmental pollution, especially measures to cut down acidic emissions of nitrogen and sulphur oxides.

The facility consists of two steam turbines, which began commercial operation in 1967 and 1968, and four cooling towers.

The main turbines run on steam produced by twin 850 MW boilers, each as tall as a 14-story building. The plant uses in excess of 4 million tons of coal a year. The plant ranks among the best in the US in terms of availability among coal plants of the same size.

Each unit is a Westinghouse cross-compound dual steam turbine-generator operating at supercritical steam conditions. At the time Keystone was constructed, Units 1 and 2 were the largest generating units in the world. Keystone was the first plant to be constructed away from a significant source of cooling water. The Keystone Reservoir was constructed on the North Branch of Plum Creek, a tributary of Crooked Creek to provide a constant source of cooling water for the plant's thermodynamic cycle year round. The cooling tower system at Keystone marks one of the most significant of early environmental controls on large power plants in the United States (thermal pollution of waterways was one of the first types of pollution to experience significant controls).

The plant's steam generators each produce approx. 7 million lbs. of steam per hour at 3,800 psi and 1,005 deg. F., with a single reheat to the same temperature. Each unit has two boiler feed pumps, one of which is run by its own steam turbine, and the other of which is powered via the low-pressure turbine-generator through a fluid coupling (so rpm may be varied to maintain the proper boiler feedwater flow and pressure). An auxiliary boiler provides steam for the feed pump with its own turbine in order to provide flow through the boiler at startup without drawing power off the grid. One of the earlier supercritical plants in the country, the boiler design incorporates an improvement over the first full-scale supercritical units at Eddystone Electric Generating Station, near Philadelphia. This improvement is a re-circulation circuit that increases water flow through the water walls surrounding the lower furnace in order to protect them during startup with considerably less flow through the entire boiler, thus saving fuel wasted as boiler flow is bypassed to the condenser during startup.

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