Hot coke being pushed out of a retort at Ravenscraig. Hot coke being pushed out of a retort at Ravenscraig.

Ravenscraig: the Coke Ovens

1 min read

Coke was one of the key ingredients to make iron at Ravenscraig. Coke is made from coal, but has fewer impurities and a higher carbon content.

Making Iron with Coke

Until the 1700s iron was always made using charcoal as a fuel. Charcoal is made by charring wood in a low-oxygen environment.  Charcoal-fired furnaces needed to have a large amount of wood close by. For that reason, most of Scotland’s ironworks were in the Highlands.

The furnace in which Abraham Darby first successfully smelted iron with coke in 1709.

The furnace in which Abraham Darby first successfully smelted iron with coke in 1709.

In 1709 Abraham Darby successfully made iron using coke in a blast furnace in Coalbrookdale, England and this transformed the industry. Not only were ironworks no longer dependent on being close to woodland but coke’s greater resistance to crushing meant that blast furnaces could be built much taller. At the same time, new drainage technology was making coal mining easier.

The coke smelting industry expanded after a way was found to turn the pig iron into malleable iron. In the 1750s, the Seven Years’ War pushed up demand for iron for cannon and Scotland’s first coke-fired ironworks, the Carron Works (which opened in 1759) became famous for its ‘Carronades’, short-range cannon used initially on merchant ships.

Bringing in the Coke

Interior of the control tower at Hunterston Terminal.

Interior of the control tower at Hunterston Terminal.

Coking coal supplies for the Ravenscraig Coke Ovens came from several local coal mines. In particular Polkemmet Colliery in West Lothian supplyied 95% of its mined coal to the steelworks. After its completion in 1979, Hunterston Coal and Ore Terminal also supplied Ravenscraig with two trainloads of coal carrying 2,500 tons a day. The new terminal replaced Glasgow’s General Terminus Quay which was unable to cope with the increasing size of modern cargo ships.

At Ravenscraig the coal was received in the coal handling area, crushed and then transported to the coke oven batteries.  When first built, Ravenscraig had 70 Becker-type combination gas-gun coke ovens built across two batteries of 35 ovens each.  They were fired with either reclaimed blast furnace or coke oven gas and were designed with ventilated foundations to reduce drying-out of the clay beds.

The Coke Ovens

The ovens were laid out in a row and a ‘charging-machine’ would run along the row, filling each furnace in turn. The coal was crushed into smaller particles beforehand, to increase its total surface area.

The heated coal was carbonised by quenching it with water.  The resulting coke was transported to the screening plant where it was sorted into size, with the large bricks being used as fuel for the blast furnaces.

The coking process also produced gas. This was then piped to the by-products plant to be purified and other valuable products, such as tar, ammonia and benzole, were extracted.

Donald Oliver started his career at Ravenscraig on the Coke Ovens and recalls the hard conditions.

 

Did you work in the coke ovens at Ravenscraig or elsewhere such as Bedlay? If so we would love to record your memories for our oral history archive. You can contact us at museumcollections@culturenl.co.uk

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