Cockenzie Power Station
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Cockenzie power station was a coal-fired power station in East Lothian, Scotland. It was situated on the south shore of the Firth of Forth, near the town of
Cockenzie and Port Seton Cockenzie and Port Seton ( sco, Cockennie ; gd, Cùil Choinnich, meaning "cove of Kenneth") is a unified town in East Lothian, Scotland. It is on the coast of the Firth of Forth, four miles east of Musselburgh. The burgh of Cockenzie was crea ...
, east of the Scottish capital of
Edinburgh Edinburgh ( ; gd, Dùn Èideann ) is the capital city of Scotland and one of its 32 council areas. Historically part of the county of Midlothian (interchangeably Edinburghshire before 1921), it is located in Lothian on the southern shore of t ...
. The station dominated the local coastline with its distinctive twin chimneys from 1967 until the chimneys' demolition in September 2015. Initially operated by the nationalised
South of Scotland Electricity Board The South of Scotland Electricity Board (SSEB) generated, transmitted and distributed electricity throughout the south of Scotland, including the former regions of Strathclyde, Lothian, Fife, Central, Borders and Dumfries and Galloway and a few t ...
, it was operated by
Scottish Power Scottish Power is a vertically integrated energy company based in Glasgow, Scotland. It is a subsidiary of Spanish utility firm Iberdrola. ScottishPower is the distribution network operator for Central and Southern Scotland, Merseyside, Nor ...
following the privatisation of the industry in 1991. In 2005 a WWF report named Cockenzie as the UK's least carbon-efficient power station, in terms of carbon dioxide released per unit of energy generated. The 1,200
megawatt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...
power station ceased generating energy on 15 March 2013 around 8.30am. There are plans to replace the station with a
Combined Cycle Gas Turbine A combined cycle power plant is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy. On land, when used to make electricity the most common type is called a combined cycle gas turb ...
(CCGT) power station. The removal of the power station was done in stages with the twin chimneys and turbine hall being demolished in a controlled explosion on 26 September 2015, the front section of the boiler house on 4 November 2015 and the rest of the boiler house on 17 December 2015. This was the last remaining major structure to be removed.


History

Under a design by the firm of celebrated architect Sir Robert Matthew, construction of Cockenzie power station began in 1959 on the site of the former Preston Links Colliery. The site is also thought to have been the hiding place of General John Cope after the defeat of his army at the
Battle of Prestonpans The Battle of Prestonpans, also known as the Battle of Gladsmuir, was fought on 21 September 1745, near Prestonpans, in East Lothian, the first significant engagement of the Jacobite rising of 1745. Jacobite forces, led by the Stuart exile C ...
on 21 September 1745. Much of the electrical equipment for the station was manufactured by Bruce Peebles & Co., Edinburgh. SSEB set aside £60 million for the station's construction; the final cost was £54 million, around £6 million under budget. The station began generating electricity in 1967 for the then South of Scotland Electricity Board (SSEB). It was officially opened on 24 May 1968 by William Ross, Secretary of State for Scotland. In 2000-01, Cockenzie generated a record load factor, supplying 3,563 GWh of electricity and burning 1,500,000 tonnes of coal. The power station occupied a site. It generated electricity at a frequency of 50 Hertz using four identical 300-megawatt (MW) generating units, for a peak supply of 1200 MW.


Operations


Coal deliveries

Coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when ...
was originally supplied to the station directly from the
deep mine This list of deepest mines includes operational and non-operational mines that are at least , which is the depth of Veryovkina Cave, the deepest known natural cave in the world. The depth measurements in this list represent the difference in ele ...
s of the neighbouring Midlothian Coalfield, but these have since been exhausted or closed. Subsequently coal was supplied from open cast mines in the Lothians, Fife, Ayrshire and
Lanarkshire Lanarkshire, also called the County of Lanark ( gd, Siorrachd Lannraig; sco, Lanrikshire), is a historic county, lieutenancy area and registration county in the central Lowlands of Scotland. Lanarkshire is the most populous county in Scotl ...
. Russian coal was used latterly as it has a low sulfur content which helped reduce sulfur oxide (SOx) emissions to the atmosphere. The power station was the first to use the "merry-go-round" system of coal deliveries by
rail Rail or rails may refer to: Rail transport *Rail transport and related matters *Rail (rail transport) or railway lines, the running surface of a railway Arts and media Film * ''Rails'' (film), a 1929 Italian film by Mario Camerini * ''Rail'' ( ...
. This system uses hopper wagons which carry around 914 tonnes of coal per train. Coal was also delivered by lorries.


Coal handling plant

Coal was delivered to the station's coal plant, which has the capacity to hold up to 900,000 tonnes of coal on a storage bing. The coal plant and storage bing were situated on the opposite side of B1348 road between
Prestonpans Prestonpans ( gd, Baile an t-Sagairt, Scots language, Scots: ''The Pans'') is a small mining town, situated approximately eight miles east of Edinburgh, Scotland, in the Council area of East Lothian. The population as of is. It is near the si ...
and
Cockenzie and Port Seton Cockenzie and Port Seton ( sco, Cockennie ; gd, Cùil Choinnich, meaning "cove of Kenneth") is a unified town in East Lothian, Scotland. It is on the coast of the Firth of Forth, four miles east of Musselburgh. The burgh of Cockenzie was crea ...
, and the main station. The coal, known as 'raw coal' at this stage was weighed, sampled and screened for metal and stones before being transported to the main station and stored in bunkers. Coal was transported from the coal plant to storage bunkers in the main station by a conveyor belt.


Milling plant

There were six pulverising mills per unit which ground down the raw coal until it had the consistency of sand. The ground coal is called 'pulverised fuel' (PF). PF burns more efficiently than large lumps of coal, which reduces waste. The PF was then blown into the furnace along with preheated air by six large mechanical fans called Primary Air (PA) Fans. At full load each unit burned around 100 tonnes of coal per hour.


Draught plant

Each unit had two large Forced Draft (FD) Fans. For efficiency these fans drew warm air from an intake at the top of the station. This combustion air was passed through the Air Heater which increased its temperature. Dampers were used to control the quantity of air admitted to the furnace and direct some of the air to the Primary Air (PA) Fans. There were also two large Induced Draft (ID) Fans on each unit. These drew the hot gases from the Boiler, through the Air Heater where the heat is transferred to the incoming combustion air. The gases were then exhausted up the chimney. The exhaust flow of these fans was also controlled by dampers in the ducting. Working in tandem the Draught plant ensured the boiler was always under a slight vacuum. This created a draw of combustion air into the boiler and an exhaust to the chimney. The exhaust gases could not be allowed to cool below a certain temperature, as there was a risk of the sulfur and nitrogen oxides in the flue gases condensing and forming acids which could have damaged the ID Fans.


Water use

The water used in the station's boilers was taken from the local water supply, known as 'towns water'. This is the same as the
drinking water Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, a ...
used to supply households. This water was used as it had already been screened and purified by
Scottish Water Scottish Water is a statutory corporation that provides water and sewerage services across Scotland. It is accountable to the public through the Scottish Government. Operations Scottish Water provides drinking water to 2.46 million household ...
.


Demineralisation plant

The station's water treatment plant further demineralised the town’s water and removed any impurities. Although safe to drink water still contains dissolved
silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
(sand) and salt. Silica particles leave scale deposits on the boiler pipes which acts as an insulator, reducing heat transfer from the furnace to the water inside. This reduces the efficiency of the station and leads to increased running costs. Salt encourages
rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO( ...
which weakens the walls of the boiler pipes and can cause them to fracture and burst, known as a boiler tube leak. A serious tube leak can lead to reduced generation or loss of the unit until repairs are carried out. Hydrazine was added and used as a reducing agent to remove excess oxygen from the water. Free oxygen atoms in the water also encourage rust to form inside the boiler pipes. Sodium hydroxide was also added to 'scour' the inside of the boiler tubes and remove any silica particles. The demineralised water was then stored in large tanks inside the main station, ready to be used in the boilers.


Feedheating plant

Before the
feedwater Boiler feedwater is an essential part of boiler operations. The feed water is put into the steam drum from a feed pump. In the steam drum the feed water is then turned into steam from the heat. After the steam is used it is then dumped to the ma ...
was introduced to the boiler it was heated up in stages. There were seven
feedwater heater A feedwater heater is a power plant component used to pre-heat water delivered to a steam generating boiler. Preheating the feedwater reduces the irreversibilities involved in steam generation and therefore improves the thermodynamic efficiency of ...
s on each unit which gradually increased the pressure and temperature of the water, until it reached a final feed temperature of around 210 °C. A steam driven Main Boiler Feed Pump (MBFP) pumped the water through the boiler
Economiser Economizers (US and Oxford spelling), or economisers (UK), are mechanical devices intended to reduce energy consumption, or to perform useful function such as preheating a fluid. The term economizer is used for other purposes as well. Boiler, po ...
and into the boiler Drum.


Boiler

The boilers were conventional
water-tube boiler A high pressure watertube boiler (also spelled water-tube and water tube) is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which boils water in the steam-gen ...
s. The Boiler Drum was a high tensile steel pressure vessel where water and steam were separated. The water here was pressurised to 170 bar and heated further to 360 °C. On the bottom of each Drum were six large bore pipes known as Downcomers. These directed the water into the boiler water pipes where it was heated by the furnace. The water was then directed back into the Drum where it flashed off into
saturated steam Steam is a substance containing water in the gas phase, and sometimes also an aerosol of liquid water droplets, or air. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization ...
. The steam was then further heated by passing through Primary and Secondary Superheaters until it reached 565 °C. The superheated steam was then piped to the high-pressure turbine, back to the boiler for reheat, and then back to the intermediate and low-pressure turbines in series.


Turbine

There was one turbine and one alternator per unit. Each turbine had a High Pressure (HP) stage, an Intermediate Pressure (IP) stage and two Low Pressure (LP) stages all connected in tandem to the same shaft. The superheated steam entered the HP turbine at a temperature of 566 °C and a pressure of 162 bar. The exhaust steam from the HP turbine travelled back through the boiler Reheater and entered the IP turbine at the same temperature but at a lower pressure of 43.5 bar. The exhaust steam from the IP turbine then entered the LP turbines. The steam was used to drive the turbines, causing the shaft to rotate at 3,000 rpm. This speed drove the
alternator An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.Gor ...
and gave a
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
of 50 cycles per second (Hz) and allowed connection to the National Grid. Electricity was generated at 17 kilovolts (kV).


Condenser

After use, the steam was condensed back into water, by passing it through the condenser.
Seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appr ...
from the Firth of Forth was used as a cooling medium. Over 500,000 litres per minute of water were used for cooling. The seawater was then discharged back into the Firth of Forth. Controls ensured the discharged seawater was kept close to the temperature of the sea, to avoid creating a 'tropical' environment and upsetting the local ecosystem.


Ash removal and use

The burning of coal in power stations generates ash and dust. The station's
electrostatic precipitator An electrostatic precipitator (ESP) is a filterless device that removes fine particles, like dust and smoke, from a flowing gas using the force of an induced electrostatic charge minimally impeding the flow of gases through the unit. In con ...
s captured fly ash from the flue gases, preventing it from entering the atmosphere. Bottom ash was also produced by the station. Ash from the station was sold through the ScotAsh company, a joint venture between Scottish Power and Blue Circle. It was used in the construction industry and in products such as grout and
cement A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement mi ...
. Any remaining ash was piped to the large lagoons in the nearby town of Musselburgh, where it was capped and planted, and used as a
nature reserve A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, or features of geological or ...
.


Electricity distribution

The electricity was initially generated at 17 kV. This was stepped up via a transformer to 275 kV for distribution on the National Grid. The electricity was distributed to Scotland, and England too, which it is connected to via a double circuit overhead line, operating at 275 kV and 400 kV, to Stella near
Newcastle upon Tyne Newcastle upon Tyne ( RP: , ), or simply Newcastle, is a city and metropolitan borough in Tyne and Wear, England. The city is located on the River Tyne's northern bank and forms the largest part of the Tyneside built-up area. Newcastle is ...
.


Post-privatisation and future

From 1991 to 2013, the station was operated by the privatised Scottish Power utility group. It surpassed its originally intended lifespan. It was run as a 'marginal station', guaranteeing seasonal and peak supply and covering non-availability of other power stations. For this reason considerable investment was made to improve start-up times to maximise generating opportunities in the deregulated electricity generation market. This upgrading was in the form of an operating system that used gas, oil and finally coal in a three-stage modified burner control system developed by Eurotherm Controls. From 2001, the station exported electricity to Northern Ireland via an undersea power link.


CCGT replacement

The coal-fired power station was forced to close due to the
Large Combustion Plant Directive The Large Combustion Plant Directive (LCPD, 2001/80/EC) was a European Union directive which required member states of the European Union to legislatively limit flue gas emissions from combustion plant having thermal capacity of 50 MW or grea ...
(LCPD). This was an EU directive that aims to reduce acidification, ground level ozone and particulates by controlling the emissions of sulfur dioxide, oxides of nitrogen and dust from large combustion plants. To reduce emissions a Boosted Over Fire Air plant was fitted to reduce the concentration of oxides of nitrogen in the flue gas. The station closed on 15 March 2013, earlier than expected. Scottish Power had considered construction of a
Combined Cycle Gas Turbine A combined cycle power plant is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy. On land, when used to make electricity the most common type is called a combined cycle gas turb ...
(CCGT) power station on the site. Natural gas is a much more efficient fuel than coal and would have created less than half the carbon and nitrogen dioxide emissions compared to the old power station. If the new station had been built, it would have required a gas pipeline from
East Fortune East Fortune is a village in East Lothian, Scotland, located 2 miles (3 km) north west of East Linton. The area is known for its airfield which was constructed in 1915 to help protect Britain from attack by German Zeppelin airships during t ...
, to supply it with fuel. In 2011 planning permission to replace the coal-fired power station was approved by the Scottish Government. The new 1,000 megawatt (MW) CCGT power station would have created up to 1,000 jobs in demolition and construction and 50 full-time positions when completed. The approval was in line with the recommendations of the report of the public inquiry. Conditions imposed on the consent were made to minimise disturbance in the area during construction. These conditions would have also lessened impacts on the environment and protected species. The development would have been carbon capture ready and would have required full
carbon capture and storage Carbon capture and storage (CCS) or carbon capture and sequestration is the process of capturing carbon dioxide (CO2) before it enters the atmosphere, transporting it, and storing it (carbon sequestration) for centuries or millennia. Usually th ...
technology if it was commercially and technically proven. A separate application for a 17 km (11 mi) pipeline from the existing gas network at East Fortune to the new power station was also approved.


Cruise ship terminal

In the 1990s, leading maritime expert Professor Alf Baird was hired by ScottishPower to investigate the case for a £30 million marine terminal to replace Cockenzie Power Station that would bring the world’s biggest cruise ship companies to the East Lothian community. Cockenzie was said to be the "optimal" site for a port because it has little tidal movement, strong rail links and room for expansion. While ships can already dock at Leith, Rosyth and Hound Point, these locations are thought to lack the necessary infrastructure to cater for large cruise liners. As of 19 June 2013, Scottish Power was considering the cruise project. In May 2015 Cockenzie Development Company Ltd (CDC) proposed a significant development for the power station site. Based around the hub of the first purpose built cruise terminal on mainland Scotland, the development could expand to incorporate a cruise terminal, retail centre, visitor centre, eco village and industrial/business park. CDC expect the facility to attract around 200 ships per annum, bringing in around 500,000 visitors a year to Scotland, to create around 2,000 jobs directly, with others created indirectly, and to boost demand for Scottish products. Visitors are expected to generate £100m for the Scottish economy. The servicing of the cruise ships could generate a further £10m spend on local skills and produce. The scheme was still under discussion in 2019.


References


External links


YouTube
- Lighting of the Chimneys during the Three Harbour Arts Festival
YouTube
- Steeplejacks on the station's chimneys in July 1997 {{Scottish energy Buildings and structures in East Lothian Biofuel power stations in Scotland Coal-fired power stations in Scotland 1967 establishments in Scotland Buildings and structures completed in 1967 2013 disestablishments in Scotland Buildings and structures demolished in 2015 Former coal-fired power stations in the United Kingdom Former power stations in Scotland