Longannet power station

Longannet power station /lɒŋˈænɪt/ was a large coal-fired power station in Fife, and the last coal-fired power station in Scotland.[4] It was capable of co-firing biomass, natural gas and sludge. The station stands on the north bank of the Firth of Forth, near Kincardine on Forth.

Longannet Power Station
Longannet power station in 2011
Country	Scotland
Location	Fife
Coordinates	56.0489°N 3.6823°W
Status	Decommissioned
Construction began	1964[1]
Commission date	1970–73[2]
Decommission date	24 March 2016
Operator(s)	South of Scotland Electricity Board (1970–1991) Scottish Power (1991–2016)
Thermal power station
Primary fuel	Coal
Tertiary fuel	Gas
Power generation
Annual net output	9,525 GWh (2012)[3]
External links
Commons	Related media on Commons
grid reference NS953852

Its generating capacity of 2,400 megawatts was the highest of any power station in Scotland. The station began generating electricity in 1970,[2] and when it became fully operational it was the largest coal-fired station in Europe. At the time of closure it was the third largest, after Bełchatów in Poland and Drax in England, and the 21st most polluting.

Longannet was operated by the South of Scotland Electricity Board until 1990, when its operation was handed over to Scottish Power following privatisation. After failing to win a contract from National Grid, the station closed on 24 March 2016.[5][6]

The station is a regional landmark, dominating the Forth skyline with its 183 m (600 ft) chimney stack. Longannet lacked cooling towers, having instead used water from the River Forth for cooling.

History

The station was designed by Scottish architects Robert Matthew, Johnson Marshall & Partners.[7] Consulting Engineers were Merz and McLellan. Construction began in 1964,[1] 4 km (2.5 mi) downstream of the existing Kincardine power station. The station was constructed on 30 hectares (74 acres) of land reclaimed from the Firth of Forth using ash from the Kincardine station. It began generating electricity in 1970, with a design lifetime of 30 years, and was in full operation by 1973.[8][9] At the time of its completion, the station was the largest in Europe.[10]

The facility was operated by the South of Scotland Electricity Board until 1990 when the electricity industry in the UK was privatised.[9] After that it was operated by Scottish Power, a subsidiary of Iberdrola.[9][11] It paid £40m per year in connection charges to National Grid due to its distance from South England.[12]

The plant opted in to the UK Transitional National Plan, placing limits on its sulphur dioxide, nitrous oxides and particulates emissions. The plant tested additional technologies that could have permitted it to operate beyond 2020 under the EU Industrial Emissions Directive.[3][13] The station closed on 24 March 2016.[5][14][15]

Design and specification

Longannet had an installed capacity of 2400 MW and a declared net capacity of 2304 MW due to plant overheads.[16][17] The station produced 9,525 GWh of electricity in 2012, an increase on the 9,139 GWh produced in 2011.[3]

Electricity generation

The station in December 2011

The station consumed up to 4,500,000 tonnes (4,400,000 long tons; 5,000,000 short tons) of coal each year.[9] Coal was delivered either by road or rail to the station's coal store, which had the capacity to hold up to 2,000,000 tonnes.[3][9] It was then fed from the coal store to the boiler house by a conveyor belt capable of carrying 3500 tonnes of coal per hour.[9]

Each of the four boilers was serviced by eight pulverising units each capable of processing 40 tonnes of coal an hour.[9] The front-wall-fired Foster Wheeler boilers could each burn around 250 tonnes of coal an hour at full load.[9] There were two forced draft and two induced draft fans on each boiler.[9] Each boiler provided around 1800 tonnes per hour of steam at a pressure of 168 bars (16,800 kPa) and a temperature of 568 °C (1,054 °F) to two 300 MW General Electric Company turbo generators.[9][18] The thermal efficiency of the plant was around 37%.[9]

Coal supply

Coal was originally supplied directly by conveyor belt from the neighbouring Longannet Colliery, until it closed in 2002 after a flood.[16][19] Around half of the coal used was Scottish, and the rest had to be imported, the majority via the former British Steel plc ore loading facility at Hunterston Terminal in Ayrshire.[3] Onward transport was by rail and the level of traffic required to supply Longannet's fuel demand caused congestion on the Scottish rail network.[20] An alternative route, the Stirling-Alloa-Kincardine rail link, at the mouth of the river Forth was reopened in 2008, and was also used to deliver coal.[21]

Cooling system

The chimney is 183 metres (600 ft) tall; the station did not have cooling towers, instead using water drawn from the Firth of Forth at a rate of 327,000 cubic metres (11,500,000 cu ft) per hour for the station's cooling condensers.[9][18][22] The water was passed through coarse screens and then circulated by four electrically driven pumps.[9] Once circulated through the station's condensers, the water was discharged into a mile long cooling channel, where heat was dissipated before the water reached a wide part of the Forth.[9] Water used by the boilers was on a different cycle, and had to be deionised. Losses from this supply were made up by a plant capable of treating 218 cubic metres (7,700 cu ft) of water per hour.[9]

Electrostatic precipitators and sulphur trioxide conditioning

The station was fitted with electrostatic precipitators (ESP) to reduce the station's particulate emissions. In the late 1980s the station's units were fitted with sulphur trioxide (SO₃) conditioning equipment to lower the fly ash's electrical resistivity. This was to ensure the station maintained allowable particulate emissions. Between 1989 and 1994, the station's ESPs were given a major refurbishment. This meant that the SO₃ conditioning equipment did not need to be operated as frequently to maintain the allowed level of particulate emissions. This was beneficial as SO₃ is hazardous.[9]

NOx reduction

In 1994, the station was awarded funding from the European Commission under the THERMIE Demonstration Programme. With this money, Unit 2 at the station was retrofitted with gas-reburn equipment. This was the largest scale application of this technology in the world. In this process, natural gas is injected into the boiler. This cut NOx emissions from Unit 2 by 50%, as well as giving a reduction in CO₂ and SO₂ emissions. In 1996, all the station's boilers were fitted with Low NOx burners. This reduced the station's NOx emissions by 40%.[9]

The blend of coal fed to each unit was intended to minimize emissions of sulphur.[3]

Carbon capture and storage

The UK's first carbon capture and storage (CCS) unit was commissioned at the station in 2009.[10] It closed in 2011 after it became clear that it was not financially viable.[23] Plans for a UK Government funded project to convert Longannet to CCS were abandoned in 2011 and no further plans for CCS at Longannet were announced.

Environmental and health impact

In 2003, Longannet was named as Scotland's biggest polluter in a report by the Scottish Environment Protection Agency (SEPA). The station produced up to 4,350 tonnes of ash per day. This was piped to ash lagoons surrounding the nearby Preston Island.[24] This was then landscaped and used to reclaim the land from the Firth of Forth.

To improve environmental emissions, Longannet was fitted with 'Low-NOx' burners to limit the formation of oxides of nitrogen and a 'gas reburn system' that used natural gas to convert NOx into nitrogen and water vapour. Longannet used to burn up to 65,000 tonnes of treated and dried sewage sludge per year, which has a similar calorific value to low-quality brown coal. In 2005, a judge ruled the burning of sludge as illegal, but the SEPA continued to allow Scottish Power to burn the sludge illegally as part of an agreement which originally required Scottish Power to construct, and have in operation, a biomass plant in 2010.[25] All burning of biomass at Longannet – including waste-derived fuel and sawdust pellets – ceased in April 2012.[3]

In 2007, the WWF named Europe's 30 most climate polluting power stations in absolute terms; of these, Longannet was the most polluting in the UK (relative to power output).[26] It was the 21st most polluting power station in Europe.[27]

According to a Greenpeace-commissioned report by Stuttgart University on the health impacts of the biggest coal-burning power plants in Europe, Longannet was responsible for 4,210 lost 'life years' in 2010.[28]

References

1. Forsyth, Valerie (2 May 2018). "A Walk in the Past: Longannet the history-maker". Alloa and Hillfoots Advertiser. Retrieved 12 December 2020.
2. "Longannet power station is switched off after 46 years". BBC News. Retrieved 9 August 2020.
3. "Longannet Power Station EMAS STATEMENT 2012" (PDF). spenergywholesale.com. Retrieved 15 July 2014.
4. "Longannet switch-off ends coal-fired power production in Scotland". BBC News. 24 March 2016. Retrieved 24 March 2016.
5. "Longannet power station closes ending coal power use in Scotland". The Guardian. 24 March 2016. Retrieved 24 March 2016.
6. Third Force News. Green groups welcome Longannet closure. 23 March 2015.
7. "Robert Matthew, Johnson-Marshall & Partners". Dictionary of Scottish Architects. 2008. Retrieved 25 August 2009.
8. The Institute of Energy's Second International Conference on COMBUSTION & EMISSIONS CONTROL. Institute of Energy Conference. London: Elsevier. 4–5 December 1995. p. 49. ISBN 9781483104508.
9. Komall, Roshan (February 2000). "Cleaner Coal Technology Programme" (PDF). Archived from the original (PDF) on 4 March 2010. Retrieved 25 August 2009.
10. "Longannet Power Station". Gazetteer for Scotland. Retrieved 25 August 2009.
11. Mark Milner (29 November 2006). "Scottish Power agrees to £11.6bn Spanish bid". The Guardian. Retrieved 21 June 2014.
12. Queiro, Alicia (7 October 2014). "What is the National Grid and why does it cost to connect to it?". BBC News. Retrieved 2 August 2016.
13. Adam Brown (17 February 2014). "Coal still counts (2): decision time for generators (or it will be soon)". targetukenergy.com. Retrieved 15 July 2014.
14. "Low Carbon Scotland: Meeting The Emissions Reduction Targets 2013-2027" (PDF). scotland.gov.uk. Retrieved 15 July 2014.
15. "Reducing emissions in Scotland: 2013 progress report" (PDF). theccc.org.uk. Retrieved 15 July 2014.
16. "Longannet Power Station". engineering-timelines.com. Retrieved 21 June 2014.
17. "Practical Large Scale Coal Firing Experience at ScottishPower" (PDF). ieabcc.nl. Retrieved 15 July 2014.
18. "Longannet Power Station: Site Information" (PDF). spenergywholesale.com. Retrieved 15 July 2014.
19. "Grim future for deep coal mine". BBC News. 29 March 2002. Retrieved 22 June 2014.
20. "Stirling-Alloa-Kincardine Railway and Linked Improvements Bill" (PDF). scottish.parliament.uk. Retrieved 15 July 2014.
21. "Residents in legal bid to stop Longannet freight trains". BBC News. 6 September 2012. Retrieved 22 June 2014.
22. "Longannet Power Station". fifeserve.com. Retrieved 15 July 2014.
23. "Longannet carbon capture project cancelled". The Guardian. 19 October 2011. Retrieved 15 March 2013.
24. Gazetteer for Scotland - Preston Island
25. eliphas (6 December 2003). "Scottish Green Party". Scottishgreens.org.uk. Retrieved 22 August 2013.
26. "Dirty Thirty" (PDF). assets.panda.org. Retrieved 15 July 2014.
27. "BBC News - Longannet power station in 'top 30 EU polluters'". BBC Online. 22 July 2014. Retrieved 22 July 2014.
28. John Vidal (12 June 2013). "European coal pollution causes 22,300 premature deaths a year, study shows". The Guardian. Retrieved 22 June 2014.

External links

• Inside the once-mighty Longannet Power Station. BBC News