Drax Power Station is a large coal-fired power station in North Yorkshire, England, capable of co-firing biomass and petcoke. It is situated near the River Ouse between Selby and Goole, and its name comes from the nearby village of Drax. Its generating capacity of 3,960 megawatts is the highest of any power station in the United Kingdom and Western Europe, providing about 7% of the United Kingdom's electricity supply.

Opened in 1974 and extended in the mid-1980s, the station was initially operated by the Central Electricity Generating Board, but since privatisation in 1990 the station has changed owner several times, and is currently operated by Drax Group plc. Completed in 1986, Drax is the most recently built coal-fired power station in England, and by implementing technologies such as flue gas desulphurisation, is one of the cleanest and most efficient coal-fired power stations in the UK.^[1] However, because of its large size, it is also the UK's single largest emitter of carbon dioxide. In an attempt to reduce these emissions, the station is currently co-firing biomass and undergoing a turbine refurbishment, and there are plans to build a biomass only fired plant alongside the station, known as Drax Ouse Renewable Energy Plant.

Construction

Drax power station was constructed in two similar phases, each of three generating units. The first phase of construction, was begun in from 1973. Costain constructed the station's foundations and cable tunnels; Sir Robert McAlpine laid the roads in and about the station, as well as building the ancillary buildings; Mowlem laid the deep foundations; Alfred McAlpine built the administration and control buildings; Balfour Beatty undertook general building works and James Scott installed cabling. Although the first phase was not completed until 1975, the station's first generating set began generating electricity in 1974.

The second phase of construction began several years later in 1985. Tarmac Construction undertook the civil engineering works; Holst Civil Engineers built the chimney; N.G. Bailey installed cabling; Reyrolle, English Electric and South Wales Switchgear produced and installed the station's switchgear, English Electric also manufactured the generator cooling water pumps; T.W. Broadbent maintained the site's temporary electrical supplies, and the Sulzer Brothers manufactured the boiler feed pumps. This second and final phase was completed in 1986. In both stages the boilers were made by Babcock Power Ltd and the generators by C. A. Parsons and Company. Following the completion of the station, Mitsui Babcock fitted flue gas desulfurization (FGD) equipment at the station between 1988 to 1995.

Post-privatisation

On privatisation of the UK's electric supply industry in 1990, the operation of Drax Power Station was transferred from the Central Electricity Generating Board to the privatised generating company National Power. They sold it on to the AES Corporation in November 1999 for £1.87 billion (US$3 billion). AES relinquished ownership of the station in August 2003, after falling into £1.3 billion of debt. Independent directors continued the operation of the station to ensure security of supply. In December 2005, after refinancing, ownership passed to the Drax Group. On 15 May 2009, the company lost its investment grade status and was downgraded to 'junk' status by Standard and Poor's.

Design and specification

The station's main buildings are of steel frame and metal clad construction. The main features of the station consists of a turbine hall, a boiler house, a chimney and twelve cooling towers. The station's boiler house is 76 m (249 ft) high, and the turbine hall is 400 m (1,300 ft) long. The reinforced concrete chimney stands at 259 metres (850 ft) high, with a diameter of 9.1 metres (30 ft), and weighs 44,000 tonnes. It consists of three flues, each serving two of the station's six boilers. When finished, the chimney was the largest industrial chimney in the world, and is still the tallest in the United Kingdom. The twelve 114 metres (374 ft) high natural draft cooling towers stand in two groups of six to the north and south of the station. They are made of reinforced concrete, in the typical hyperbolic design, and each have a base diameter of 92 m (302 ft). Other facilities on the site include a coal storage area, flue gas desulphurisation plant and gypsum handling facilities.

Drax power station is the second largest coal-fired power station in Europe, after Bełchatów Power Station in Poland. Drax produces around 24 terawatt-hours (TWh) (86.4 petajoules) of electricity annually. Although it generates around 1,500,000 tonnes of ash and 22,800,000 tonnes of carbon dioxide each year, Drax is the most carbon-efficient coal-fired powerplant in the United Kingdom.

Operations

Coal supply and transport

The station has a maximum potential consumption of 36,000 tonnes of coal a day. Per year, this equates to around 9 million tonnes. This coal comes from a mixture of both domestic and international sources, with domestic coal coming from mines in Yorkshire, the Midlands and Scotland, and foreign supplies coming from Australia, Colombia, Poland, Russia and South Africa.

When the station first opened, the majority of the coal burned there was taken from various local collieries in Yorkshire. These collieries included: Kellingley, Prince of Wales, Ackton Hall, Sharlston, Fryston, Askern and Bentley. However, since the miners' strike in the mid-1980s, all but one of these mines have shut, with the pit at Kellingley being the only one of these still open.^[18] UK Coal currently have a five year contract to supply the station with coal. This contract ends at the end of 2009. They supply the station with coal from Kellingley, Maltby and, until its closure in 2007, Rossington. Coal was also brought to the station from Harworth Colliery until it was mothballed, and is still supplied by Daw Mill in Warwickshire.

The foreign coal is brought to the station via various ports in the UK, and it is taken from these ports to the power station by railway. First GBRf have a contract with Drax Group to move coal brought to Port of Tyne to the power station. This contract has been celebrated by First GBRf naming one of their locomotives Drax Power Station. English Welsh & Scottish Railways haul coal to the station from the nearby ports of Hull and Immingham, and from Hunterston Terminal on the west coast of Scotland.^[18][21] Freightliner move coal imported through Redcar.

All of the coal is delivered to the station by train. Trains reach the station using a 7.2 km (4.5 mi) long freight only section of the closed Hull and Barnsley Railway, which branches away from the Pontefract Line at Hensall Junction. A balloon loop rail layout is used at the station so that wagons of coal do not need to be shunted after being unloaded. Merry-go-round trains are used, so that wagons can be unloaded without the train stopping, as it passes through an unloading house. On average, there are 35 deliveries a day, 6 days a week.

Electricity generation

Coal is fed into one of thirty coal bunkers, each with a capacity of 1,000 tonnes of coal. Each bunker feeds two of the station's sixty pulverisers, each of which can crush 36 tonnes of coal an hour. The station has six Babcock Power boilers, each weighing 4,000 tonnes. The powdered coal from ten pulverizers is blasted into each boiler through burners, which are ignited by propane. In 2003 the original burners were replaced by low nitrogen oxide burners. Each of the six boilers feed steam to a steam turbine set. Each steam turbine consists of one high pressure (HP) turbine, one intermediate pressure (IP) turbine and three low pressure (LP) turbines. The HP turbines generate at 140 megawatts (MW). Exhaust steam from them is fed back to the boiler and reheated, then fed to the 250 MW IP turbines and finally passes through the 90 MW LP turbines. This gives each generating set a generating capacity of 660 MW, and with six generatin sets, the station has a total capacity of 3,960 MW. Each of the generating units is equipped with the Advanced Plant Management System (APMS), a system developed by RWE npower and Thales, and implemented by Capula.

The station also has six gas turbines installed. These standby turbines provide backup for breakdowns, or shut downs in the National Grid. Their annual output is generally low, generating 75 MW. and three of the units have been mothballed and are out of operation, but they could be refurbished. Emissions from these units are released through the stations second, smaller chimney, to the south of the main stack.

Cooling system

Water is essential to a thermal power station, as water is heated to create steam to turn the steam turbines. Water used in the boilers is taken from two licensed boreholes on-site. Once this water has been through the turbines it is cooled using condensers. Water for these condensers is taken from the nearby River Ouse. Water is pumped from the river to the power station by a pumphouse on the river, north of the station. Once it has been through the condenser, the water is cooled by one of the station's natural draft cooling towers, with two towers serving each generating set. Once cooled, the water is discharged back into the river.

Flue gas desulphurisation

All six units are served by independent wet limestone-gypsum flue gas desulphurisation (FGD) plant, which was installed between 1988 and 1996. This diverts gasses from the boilers and passes them through a limestone slurry, which removes at least 90% of the sulphur dioxide (SO₂) in the gasses. This is equivalent to removing over 250,000 tonnes of SO₂ from the station's emissions each year. The process requires 10,000 tonnes of limestone a week. This limestone is sourced from Tunstead Quarry in Derbyshire. A byproduct of the process is gypsum, and 15,000 tonnes of it is produced by the station each week. This goes to be used in the manufacture of plasterboard. The gypsum is sold exclusively to British Gypsum, and it is transported by rail to their plants at Kirkby Thore (on the Settle-Carlisle Railway), East Leake (on the Great Central Main Line) and occasionally to Robertsbridge (on the Hastings Line).^[32] English, Welsh & Scottish Railways transport the gypsum to the plants.

Ash use and disposal

Pulverised fuel ash (PFA) and furnace bottom ash (FBA) are two byproducts made through the burning of coal. Each year, the station produces about 1,000,000 tonnes of PFA and around 220,000 tonnes of FBA. Most of this ash is sold on, with all FBA and 85% of PFA being sold. Under the trade name Drax Ash Products, the sold ash is sold to the local building industry, where it is used in the manufacture of blocks, cement products, grouting and the laying of roads. The ash is also used in other parts of the country. Between 2005 and 2007, PFA was used as an infill at four disused salt mines in Northwich in Cheshire. 1,100,000 tonnes of PFA was used in the project, which was to avoid a future risk of subsidence in the town. Ash was delivered to the salt mines by EWS in ten trains a week, each carrying 1,100 tonnes of PFA. Following a trial in January 2010, PFA is also transported to Waterford in Ireland by boat. One ship a month will transport 1,200 tonnes of PFA from the station to Ireland for the manufacture of construction materials. This will replace 480 lorry journeys annually and is deemed more environmentally friendly.

The unsold PFA is sent by conveyor belt to the Barlow ash mound, which is used for disposal and temporary stockpile. Three conveyors feed the mound, with a total capacity of delivering 750 tonnes of PFA an hour. Some FGD gypsum is disposed of on the mound, if it is not of a high enough grade to be sold on. The mound itself is notable as it has won a number of awards for its nature conservation work.

Co-firing

Co-firing is the process of burning two or more types of fuel together at the same time. As well as burning coal, Drax power station also co-fires biomass and petroleum coke ('petcoke'). The station tested co-firing biomass in the summer of 2004, and in doing so was the first power station in the UK to be fueled by wood. The initial trial of 14,100 tonnes of willow was locally sourced from nearby Eggborough.

Since the trial, the station's use of biomass has continued. The station uses direct injection for firing the biomass, whereby it bypasses the station's pulverising mills and is either injected dirctly into the boiler or the fuel line, for greater throughput of biomass. The station's use of biomass has continued to increase and they have currently set a target for 12.5% of the station's energy to be sourced from biomass. This will contribute to the station's aim to cut its CO₂ emissions by 15%. The station burns a large range of biomass fuels, but among them, the most used are wood pellets, sunflower pellets, olive, peanut shell husk and rape meal. The majority of the station's biomass comes from overseas.

The station started to trial the co-firing of petcoke in one of its boilers in June 2005. The trial ended in June 2007. Over this period the boiler burned 15% petcoke and 85% coal. Petcoke was burned in the station to make the price of the station's electricity more competitive as the price of running the station's FGD equipment was making the station's electricity more expensive. The Environment Agency (EA) granted permission for the trial in June 2004, despite the plans being opposed by Friends of the Earth and Selby Council.^[41] To meet their concerns, the station's emissions were constantly monitored through the trial, and they were not allowed to burn petcoke without operating the FGD plant to remove the high sulphur content of the fuel's emissions. The trial proved that there were no significant negative effects on the environment, and so in late 2007, Drax Group applied to move from trial conditions to commercial burn. The EA granted permission in early 2008 after agreeing with Drax's findings that the fuel had no significant negative effects on the environment. The station can now burn up to 300,000 tonnes of the fuel a year, and stock anything up to 6,000 tonnes of the material on site.

Drax power station
Drax Power Station Viewed from the west in April 2002
Country	England
Town/city	Selby
Location	Drax
Coordinates	53°44′07″N 0°59′31″W / 53.73515°N 0.99187°W / 53.73515; -0.99187Coordinates: 53°44′07″N 0°59′31″W / 53.73515°N 0.99187°W / 53.73515; -0.99187
Owner	Central Electricity Generating Board (1974-1990) National Power (1990-1999) AES Corporation (1999-2003) Drax Group plc (2005-present)
Status	Baseload
Fuel	Coal, Biomass, Petcoke
Conveyance	Rail
Cooling water	Fresh
Technology	Steam tubine
Turbines	Six 660 MW C. A. Parsons and Company
Installed capacity	3,960 MW
Commissioned	1974-75 and 1986