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Didcot A Power Station, site of
Sutton Courtenay, Didcot, Oxfordshire, UK
associated engineer
Not known
date  1968 - 1970
era  Modern  |  category  Power Generation  |  reference  SU512919
Originally coal-fired, three out the four boilers at Didcot A power station were converted to co-fire natural gas. This was the first large power station in the UK to have this facility. Didcot A had four generating units, each capable of an output of 500MW. It closed in 2013.
The coal for the power station was delivered by train and stockpiled on site. It was then milled to a fine powder and carried into the boilers by a jet of hot air, where it burnt like a gas. That was used to heat water, which flowed in tubes lining the combustion chambers. It converted to steam, circulated twice through the boilers. Steam left the boiler at 568 degrees Celsius and 16,550kN per sq m pressure.
The steam entered the high pressure part of the turbines and turned the shafts at 3,000rpm. The shafts were linked directly to the generators. Steam returned to the boilers, was reheated, and then entered the intermediate and low pressure parts of the turbines. Exhaust steam from the turbines was condensed and returned to the combustion chamber tubes.
Inside each generator an electromagnetic rotor weighing 74 tonnes turned the copper stator to create alternating electric current at 23,500V. This was transformed up to 400kV and transmitted to the UK's National Grid from their substation on site. Sufficient electricity was generated to supply 2 million people.
Cold water for the condenser was drawn from the River Thames. Once heated, the water was cooled by evaporation inside six hyperbolic concrete cooling towers. This process produced a mist of water vapour that emerged as plumes from the top of the towers.
Electrostatic precipitators removed some 99 percent of fine coal dust from the boiler exhaust gases before they were expelled from the chimney. Larger ash particles were collected from the bottom of the boiler and piped to settlement pits.
A stockpile of some 5,000 tonnes of dry ash and dust was stored in silos. These were sold to Generation Aggregates for use in construction projects, or for the manufacture of Thermalite aerated breeze blocks.
Between 1970 and 1984, the surplus dust and ash were put into landfill at Sutton Courtenay. After 1984, they were pumped 8km through a 440mm diameter pipeline to lagoons in Radley. Water was filtered out of the lagoons, back into the Thames.
In 1996 and 1997, computerised advanced plant management systems were installed on all four generating units. This was designed to maximise performance and minimise cost.
From 2002, in line with UK government advice, Didcot A generated some of its power by burning biomass wood sawdust. This was able to replace up to 2 percent (74,000 tonnes) of the coal burned on site.
The power station was built by the Central Electricity Generating Board. It had been operated by National Power and Innogy, and then by RWE npower. It operated under licence from the Environment Agency, and was certified to ISO 14001. The station was been the subject of environmental protests, in November 2006 and October 2009.
Didcot A was required to close on or before 31st December 2015, as it has opted out of the EU Large Combustion Plants directive. Its generators were turned off in 2013, and demolition was scheduled. By February 2016, demolition was under way.
Tragically, the power station collapsed on 23rd February 2016 during demolition, killing at least one person.
Architect: Frederick Gibberd
Bolier supply: Babcock Power Ltd
Turbine and generator supply: C.A. Parsons & Co
Advanced plant management system (1996-7): Thales UK
Research: ECPK
b i b l i o g r a p h y
"Didcot Power Stations" by npower, RWE Group
undated, document in PDF available on www.rwe.com
www.industcards.com
www.rwe.com
www.ukqaa.org.uk
Location

Didcot A Power Station, site of