Longview is among the first half dozen or so of a new generation of supercritical coal-fired power plants to start construction in the USA after a long hiatus (others being CBEC 4, Weston 4, Comanche 3, Elm Road and Iatan 2, see MPS, April 2007, pp 14-18). The developers of the 700 MWe (net) (769 MWe gross) plant in West Virginia (on the border of western Pennsylvania), can also claim a number of other firsts.

One particularly noteworthy feature of Longview (formerly known as Robinson Run) is that it is the first supercritical pulverised coal (PC) plant in the world to employ a low-mass-flux vertical-tube Benson boiler, to be supplied by Foster Wheeler (under a $200 million contract) using technology licensed from Siemens. There is such a boiler in operation, retrofitted into the Yaomeng plant in China by Mitsui (now Doosan) Babcock (also a Benson licensee), but that is subcritical. There is also one under construction, again being supplied by Foster Wheeler, at Lagisza in Poland. This is supercritical, but CFB rather than PC.

Among the advantages of vertical, compared with spiral wound, tubing is that it is self supporting, simplifying structural design, facilitating installation and reducing costs (with, eg, less field welding needed and installation of support straps avoided). Another major attraction is that it allows once-through operation down to 20% of full load.

The key to the low-mass-flux vertical-tube Benson boiler is its rifled (also called internally ribbed) evaporator tubing. The rifling is of special geometry developed by Siemens, with Benson-licensed boilermakers Doosan Babcock and Foster Wheeler the first users.

The rifling design improves heat transfer properties (notably avoiding deterioration of transfer with increased steam quality), allowing the boiler to operate with a low mass flux, comparable with that of drum boilers. This yields a number of advantages, including “natural circulation” or “positive flow” characteristics, basically meaning that increased heat input to a tube is automatically compensated for by increased flow (and vice versa). The concept was proven in a test section at the Farge coal-fired plant, Germany, and, at commercial scale, in the horizontal-exhaust-gas-flow vertical-tube HRSG of the Cottam combined cycle plant in the UK.

IPP and private equity

Other firsts claimed by the developers of the Longview project include: first US supercritical coal plant developed by an IPP; first greenfield coal plant in the north east of the USA for over 20 years; first major private equity participation in a new US coal plant project; and first Siemens “steam reference plant in the US.” The plant’s developers believe some form of carbon cap and trade system is inevitable in the future and have agreed to fund a non-profit organisation to handle carbon dioxide offsets, to the tune of $500 000. They have also undertaken to treat acid mine water in nearby abandoned mines, addressing a pre-existing environmental problem and providing the plant with a water supply, avoiding the need to take river water.

Longview, which is located on a greenfield site in a mine mouth location at Maidsville, north east of Morgantown, near the Monongahela River, some 70 miles south of Pittsburgh, will run on Eastern bituminous coal (to be supplied by conveyor). The efficiency will be 43.3% (LHV) (heat rate = 8600 Btu/kWh), with steam conditions of 250 bar and just under 600°C (ie supercritical but certainly not in the realm of ultrasupercritical, or to put it another way “leading edge not bleeding edge”).

The project finally received all necessary permit approvals and commenced construction in February 2007, with financial close and notice to proceed. The construction period is 48 months, with about 1500 craftworkers employed at the peak. “Substantial completion”/power plant operation is slated for spring of 2011.

With a total cost of $1.83 billion (50% equity) the project represents one of the largest single private investments in the history of West Virginia.

The project is 100% owned by Longview Power, LLC, which is in turn 100% owned by GenPower Holdings, LP, an entity created in October 2006 to invest in power projects. It was set up by GenPower, LLC, a privately held Boston based power plant developer, and First Reserve Corporation, the oldest and largest private equity firm focused exclusively on energy investments with $12.5 billion under management. GenPower LLC contributed its portfolio of projects, which included Longview. First Reserve made a five-year commitment to support development activities, investing $500 million in Longview and setting aside $500 of equity for new projects.

The Longview investment thesis can be summarised thus: electricity demand growth will eliminate present oversupply by 2011, coal fired plants will retain dispatch advantage over gas fired plants for baseload, and new supercritical plants will have a distinct advantage over old coal units.

The plant will sell power and capacity through a five-year 300 MW power purchase agreement with PPL EnergyPlus, LLC. The balance of the project’s generation will be sold on a merchant basis into PJM, said to be the largest and most liquid competitive wholesale electricity market in the USA.

The project will benefit from an attractive mine-mouth fuel supply contract that is estimated to significantly reduce fuel costs. As a result of this, combined with the technology to be employed, Longview expects to have a very competitive cost of dispatch.

Construction consortium

Construction will be guaranteed on a joint and several basis by a consortium of Siemens and Aker Kvaerner Songer, under a fixed-price, date-certain EPC contract, incorporating performance and completion guarantees, with a substantial completion date of 12 March 2011. The total consortium order volume is around $1.3 billion.

As well as licensing the boiler technology, Siemens, as EPC consortium leader, has a $405 million contract to provide turbine island design, as well as major turbine island equipment, including the steam turbine, generator, plant control system and, via its Wheelabrator subsidiary, an advanced air quality control system to reduce the emissions of particulates, sulphur dioxide, mercury, and sulphur trioxide. Burns and Roe are providing detailed engineering for the Siemens scope, under subcontract.

Aker Kvaerner Songer, under a contract valued at $654 million, will provide construction services and materials for the turbine island and boiler island. The power plant is located within about 50 miles of Aker Kvaerner Songer’s Canonsburg campus.

Innovative environmental permitting

As part of the public comment process for its air permit application, Longview reached an innovative arrangement with US Federal Park and Forest Service land managers to purchase SOx allowances in excess of regulatory requirements under the Acid Rain Program to offset acid deposition impacts from Longview on Dolly Sods National Forest and Shenandoah National Park. This arrangement was incorporated as a requirement under Longview’s air permit. The adopted permit condition also provides a mechanism for Longview to fund SOx controls on existing area SOx sources in lieu of allowance purchases, to achieve the same effect – no increase in acid deposition in Class I areas. Subsequent to issuance of its final air permit in March 2004, Longview reached agreement with the National Parks Conservation Association, Sierra Club and Trout Unlimited to amend several of the permit requirements, and perhaps more importantly, establish a non-profit 501(c)(3) corporation funded by Longview to investigate and fund efforts to mitigate acid deposition and CO2 emissions.

Dealing with mine water

In addition to minimising and mitigating the impacts of its air emissions, Longview has made a significant commitment to eliminating existing (and potential for) discharges of untreated acid mine water from abandoned underground coal mines in the area. In particular, Longview has contracted with AMD Reclamation, Inc (AMDRI), a non-profit 501(c)(3) entity established and operated by GenPower, to construct and operate water treatment facilities to pump and treat 10 million gallons per day of treated mine pool water. Without this economic commitment by Longview, the mine pool water would be discharged untreated into local rivers and streams. In particular an abandoned coal mine was in danger of overflowing due to the gradual rise of groundwater and the flooding of highly acidic mine water into Dunkard Creek, which flows into the Monongahela River, would have severe ecological impacts.

The water initially will be treated and released, but once Longview is operational, the water will be used for cooling at the power plant.

AMDRI has built and is now operating the first primary treatment plant, which has received grants and loans totalling $7.5 million from the Pennsylvania Department of Environmental Protection and various state agencies, with a second facility to follow shortly.

In addition, Longview will be funding an ongoing programme to assist in the reforestation of West Virginia strip mining lands and assist in the treatment of waters through a foundation to be established with the Sierra Club and Trout Unlimited once the plant goes into comm ercial operation.

Location of the Longview site The Longview site, as of end March 2007 Commercial structure of the Longview project Longview consortium structure: scope split Cross section of Longview boiler