Virginia agency takes comment on 1,600 MW Greensville power plant

natural gas fired plant nov elp

The Virginia Department of Environmental Quality is taking comment until March 31 on a draft PSD air permit for the 1,600 MW (nominal) Greensville County combined cycle project of Dominion Virginia Power.

The utility, which is a unit of Dominion Resources, is currently before the Virginia State Corporation Commission for an approval on this project.

As proposed, this will be a combined-cycle, natural gas-fired facility. It will be located on a 1,143-acre parcel just west of the intersection of State Route 620 (Radium Rd.) and State Route 605 (Rogers Rd.) on the Brunswick County/Greensville County line. This facility will be about 4.5 miles to the east/southeast of the newly-constructed, gas-fired Brunswick County Power Station of Dominion.

"The facility will be located on a site which is suitable from an air pollution standpoint," said the DEQ. "The area is rural with a combination of undeveloped and transitional land (tree plantations and farms). An existing electric transmission line is less than 1,000 feet to the west. The site is an upland area (elevation 150-200 feet). The Meherrin River borders the southern end of the property site and Greensville Creek will transect it."

The proposed project will be a nominal 1,600 MW facility using three combustion turbines each with a duct-fired heat recovery steam generator (HRSG) with a common reheat condensing steam turbine generator (3 on 1 configuration). The proposed fuel for the turbines and duct burners is pipeline-quality natural gas.

Emissions from the turbines will be controlled by the use of low carbon fuels and high efficiency design (for greenhouse gases), clean fuels and good combustion practices (for PM10 and PM2.5), selective catalytic reduction and low NOx burners (for NOx), and oxidation catalyst (for carbon monoxide and volatile organic compounds).

A natural gas-fired auxiliary boiler, six fuel gas heaters, an auxiliary equipment cooler, four inlet chillers, an emergency diesel fire water pump, three emergency generators, and an oil storage tank are also proposed and will be subject to emission controls. Electrical circuit breakers potentially emit GHG pollutants (expressed as carbon dioxide equivalents, or CO2e) and they will also be covered in the permit.

The utility has proposed the installation of three Mitsubishi M501J class CTs in combined-cycle mode, the DEQ noted. Mitsubishi Hitachi Power Systems Americas announced in May 2015 that it had received an order for these turbines.

The project will use three HRSGs, one for each CT, which will use waste heat to produce additional electricity. Each HRSG will act as a heat exchanger to derive heat energy from the CT exhaust gas to produce steam that will be used to drive a Steam Turbine generator.

Steam production in the HRSGs will be augmented using duct burners that will be fired by natural gas. The proposed DBs will have a firing rate of 500 MMBtu/hr each. The heat recovered is used in the combined-cycle plant for additional steam generation and natural gas/feedwater heating.

Each HRSG will include high-pressure superheaters, a high-pressure evaporator, high-pressure economizers, reheat sections (to reheat partially expanded steam), an intermediate-pressure superheater, an intermediate-pressure evaporator, an intermediate-pressure economizer, a low-pressure superheater, a lowpressure evaporator, and a low-pressure economizer. The dry condenser will condense the steam exhausting from the ST. As the steam is condensed, the condensate flows to the condensate receiver tank.

The proposed project includes one reheat, condensing steam turbine generator designed for variable pressure operation. The steam turbine generator set is designed to produce up to about 600 MW of electrical output at ISO conditions with duct firing.

Four mechanical draft cooling towers will be incorporated to provide air inlet chilling for the CTs. These devices will cool the inlet area during periods of high ambient temperature in order to increase power output and improve efficiency. Particulate matter emissions from the cooling towers associated with the inlet air chillers will be controlled by high efficiency drift eliminators.

The proposed facility will include a 185.0 MMBtu/hr, natural gas-fired, auxiliary boiler. The auxiliary boiler will provide steam to the ST at start-up and at cold starts to warm up the ST rotor. The steam from the auxiliary boiler will not be used to augment the power generation of the CTs or ST. The boiler is proposed to operate 8,760 hrs/yr but will be limited by an annual fuel throughput based on a capacity factor of 10 percent. NOx emissions from the boiler will be controlled by the use of low NOx burners.

The facility will include three 7.8 MMBtu/hr and three 16.1 MMBtu/hr natural gas-fired, fuel gas heaters. The heaters will be used to warm up the incoming natural gas fuel to prevent freezing of the gas regulating valves under certain gas system operating conditions. The heaters are proposed to operate 8,760 hrs/yr. NOx emissions from the heaters will be controlled by the use of low NOx burners.

The project also includes a 3,000 kW diesel-fired emergency generator that will be operated up to 500 hours per year (including 100 hrs of maintenance checks and readiness testing). The emergency generator will provide power in emergency situations for turning gears, lube oil pumps, auxiliary cooling water pumps and water supply pumps. The emergency diesel generator is not intended to provide sufficient power for a black start, peak shaving or non-emergency power.

Another project component will be two 150-kW propane-fired emergency generators that will be operated up to 500 hours per year each (including 100 hrs of maintenance checks and readiness testing). The emergency generators will provide power in emergency situations for the uninterruptible power supply for the control house in the switchyard. The emergency propane generators are not intended to provide sufficient power for a black start, peak shaving or non-emergency power.

Dominion proposes to construct a 16-bay delugeable auxiliary equipment cooler which will cool the lubricating oil for miscellaneous equipment. Forced-draft fans will be incorporated to provide the flow needed for the equipment cooler. The cooler will have six bays equipped with deluge water sprays for additional cooling during extremely hot weather, causing particulate matter emissions from drift.

The DEQ noted that this project has a proposed construction commencement date in June 2016, and proposed start-up date in January 2018.

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