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 power plant will close by or before December 31, 2028, as a result of a new wastewater rule that prohibits coal power plants from dumping mercury, arsenic, and selenium into streams and rivers, along with the Conemaugh Generating Station and at least 24 other power plants in 14 states.[1]
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 four 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 approximately seven 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.[3]
Since the plant's initial commissioning, several environmental control systems have either been upgraded or installed. These include modifications to the electrostatic precipitators, the addition of an ammoniaflue gas conditioning system to improve precipitator performance, and a low/NOx burner system to reduce the oxides of nitrogen (NOx) emissions. A Selective Catalytic Reactor (SCR) further reduces the NOx emissions. In 2009 a wet flue-gas desulfurization system was put in place to reduce sulfur dioxide and heavy metal emissions. The plant has a continuous emissions monitoring system in the stack which must adhere to very rigid accuracy and reliability requirements established by the Commonwealth of Pennsylvania.
A consortium of mid-atlantic power companies owns the plant. PSEG Fossil owns a 22.84 percent share (391 net MW with peaker), while Reliant Resources, operates it. The plant is basically a twin of the Conemaugh Generating Station, also partially owned by PSEG Fossil.
Key Facts:
Location: Shelocta, PA
MW: 1,711
Fuel: Coal
Commercial Operation: Unit 1: 1967, Unit 2: 1968
Ownership: 22.84% PSEG Fossil
Duquesne Light Holdings: 2.47% or 42.3 Megawatts (this part was previously owned by Atlantic City Electric)
Emissions
Keystone was outfitted with a wet limestone scrubber system in late 2009 to partially remove heavy metals and sulfur dioxide from the emitted flue gas.
While the plant has had SCR technology in place since 2003 to reduce emissions of nitrogen oxides, after 2010 operation of this equipment during the ozone season (May – September) was severely curtailed. Emission rates for nitrogen oxides during the 2011 and 2012 ozone seasons reverted to essentially what they had been prior to SCR start up in 2003, resulting in the release of approximately 9,000 additional tons of NOx per season over what could have been achieved with full operation of this pollution control technology.
Following the implementation of Pennsylvania’s Reasonably Available Control Technology rule (RACT 2) in 2017 which imposed more stringent emission requirements, NOx emission rates fell that year by 79% from 2011, the year of peak SCR curtailment.[4][5]
