Cement Kilns: Dunbar

Dunbar in 1968. Base map OS NT7076, 1968 revision, courtesy of the National Library of Scotland. Other detail from published plans. This shows the plant with three Lepol kilns, prior to conversion to precalciner operation. At this time it was Blue Circle's largest UK plant. View HD image in a new window.

Approximate capacity: tonnes per year: ✄

Picture: ©Lisa Jarvis 2007, and licensed for reuse under this Creative Commons Licence. See this and related images on Geograph. This shows the plant in 2007, viewed from the southwest. The separate stack through which the kiln gases leave the system is that of the SO₂ scrubber. Because wet scrubbing is used, the plume carries a large amount of water vapour.

Picture: ©Walter Baxter 2010, and licensed for reuse under this Creative Commons Licence. See this and related images on Geograph. This shows the plant in 2010, viewed from the west. The re-routed A1 highway is in the foreground.

Dunbar in 1976. Picture: ©NERC 1976: British Geological Survey Cat. No. P001495. This shows the view from the southeast of the Lepol plant prior to conversion to precalciner process. The nearer kiln building is that of kiln 3. The Bass Rock in the Firth of Forth can be seen on the horizon.

The Oxwell Mains Limestone Mine. Base map courtesy of National Library of Scotland: surveyed 1968. Mine details courtesy of BGS. This shows the stall-and-pillar mine in the Upper Longcraig Limestone, accessed through an adit on the NE edge. The Middle Skateraw Limestone seam above it was also mined, only along the northern edge, because it thins southwards. The course of the A1 diversion, opened in 1981, is shown in grey. The top 10 ft of the limestone (total thickness 20-25 ft) was left in place to form a stable roof.

Location:

Grid reference: NT7066276317
x=370662
y=676317
55°58'44"N; 2°28'13"W
Civil Parish: Dunbar, East Lothian

Clinker manufacture operational: 1963 to date

Approximate total clinker production to 2022: 43 million tonnes (8^th)

Raw Materials from the lower Carboniferous Limestone (Lower Limestone Formation: 322-331 Ma), in quarries at:

1963-1982: South Quarry at 371300,675700
1982-2006: Northwest Quarry at 370400,677000
2006 to date: Northeast Quarry at 371500,676800

The deposit has the following sequence (top to bottom):

2 to 20 m overburden, consisting of drift, magnesian limestone, sandstones and shales
1.2 m shale – used
5.2 m upper limestone - Middle Skateraw Limestone (Blackhall Limestone Member) – used
~10 m of interburden, consisting of magnesian limestone, sandstones and shales
7.2 m lower limestone – Upper Longcraig Limestone (Hurlet Limestone Member) - used

Additionally some sand – either bought in or interburden – is added.

Ownership:

1962-2001 Blue Circle
2001-6/1/2013 Lafarge
7/1/2013-14/7/2015 Lafarge Tarmac
15/7/2015- CRH

Also known as Oxwellmains Works. The limestone here was long known as the best in lowland Scotland, and the Oxwell Mains lime works, supplying the Scottish steel industry, was situated on the plant site, using drift mining. Until acquisition by Blue Circle in 1959, it was owned by Coltness. The two limestone seams, with substantial overburden and interburden, are extracted by a unique narrow slot mining technique that continuously restores the land as the face moves forward. As a result, the earlier quarry is already under agriculture. The limestone contains a few thin coal seams which benefit the fuel efficiency of the plant, giving it in the early days the lowest fuel consumption of any plant.

The original quarry was worked south of the railway. The area north of the railway was then worked. The A1 Edinburgh-London road originally ran north of the railway, and had to be re-routed to the south of the plant to free up the land to the north.

A Lepol plant was installed, although a suspension preheater system was feasible, because technology could be cheaply transferred from the successful Cauldon plant. With the installation of the third kiln in 1966, Dunbar became Blue Circle’s largest UK plant until overtaken by Hope in 1970.

The rawmills were distant from the kilns and could not use waste heat from the kiln system for raw material drying. They were heated with fuel oil, with typical heat usage 0.20 MJ/kg.

The plant was changed to precalciner operation in 1986, as with Cauldon, mainly in order to simplify the plant and allow operation with a smaller workforce.

Please contact me with any relevant information or corrections. I am particularly interested in firmer dates and statistics.

Note: technical information on currently operational plants is ✄withheld in the public version of the site at present, except where already published (see references).

Power Supply

The plant was entirely electrically powered from the grid from the outset.

Rawmills

1963-1986: One 1350 kW Aerofall mill for coarse grinding and one Head Wrightson 900 kW ball mill for separator rejects regrind. A second regrind mill was installed in 1966.
1986 to date Polysius RM54/27/90 roller mill, table 5.6m diameter, 2800 kW.

Three rotary kilns were installed:

Kiln A1

Supplier: Polysius
Operated: 01/04/1963-1986
Process: Semi-dry: Lepol 20.9×3.91 m grate
Location: Hot end 370630,676340: Cold end 370691,676324: entirely enclosed
Dimensions: Metric 63.00 × 3.793
Rotation (viewed from firing end): anti-clockwise
Slope: ?
Speed: ?
Drive: 82 kW
Kiln profile: 0×3340: 900×3340: 1800×3793: 62000×3793: 62500×3023: 63000×3023: Tyres at 4400, 22400, 34400, 55400.
Cooler: Fuller 744H grate
Fuel: Coal
Coal mill: direct: MPS90 75 kW roller mill
Exhaust: two parallel Western Precipitation electrostatic precipitators before the ID fan.
Typical Output: 1963-1969 684 t/d: 1970-1980 774 t/d: 1981-1986 684 t/d
Typical Heat Consumption: 1963-1969 3.38 MJ/kg: 1970-1980 3.19 MJ/kg: 1981-1986 3.29 MJ/kg

Kiln A2

Operated: 29/04/1963-1986
Location: Hot end 370626,676327: Cold end 370687,676311: entirely enclosed
Typical Output: 1963-1969 675 t/d: 1970-1980 761 t/d: 1981-1986 665 t/d
Typical Heat Consumption: 1963-1969 3.38 MJ/kg: 1970-1980 3.20 MJ/kg: 1981-1986 3.31 MJ/kg
Identical in all other respects to A1

Kiln A3

Supplier: Polysius
Operated: 20/09/1966 to 1984, 1986 to date
Process: 1966-1984 Semi-dry: Lepol 27.7×3.91 m grate: 1986 to date 5-stage air-separate precalciner: Dopol 2535.A5,

Stage 1 2×5.62ϕ
Stage 2 2×5.34ϕ
Stage 3 2×5.34ϕ
Stage 4 1×7.35ϕ
Stage 5 2×5.34ϕ
Prepol AS calciner 330 m³

Location: Hot end 370622,676310: Cold end 370680,676295: entirely enclosed
Dimensions: Metric 60.00 × 3.916BC / 4.351D
Rotation (viewed from firing end): anti-clockwise
Slope: 3.5% (2.006°)
Speed: 1.1 rpm: from 1986 increased to 3.5 rpm
Drive: 134 kW: from 1986 increased to 390 kW
Kiln profile: 0×3519: 911×3519: 1811×3916: 49036×3916: 52311×4351: 59011×4351: 59620×3640: 60000×3640: Tyres at 4737, 27237, 47737: Turning gear 44737.
Cooler: Fuller 850H grate: from 1986 Claudius Peters 1037 grate
Fuel: Coal, plus liquid wastes from 1994, petcoke from 1996, tyres from 1999, and sewage sludge from 2012.
Coal mill: direct: MPS100 75 kW roller mill: from 1986 Polysius RMK 19/9/28 roller mill, dia 1.9 m, 250 kW
Exhaust: 1966-1984, two parallel Western Precipitation electrostatic precipitators before the ID fan. From 1986 ✄
Typical Output: 1966-1970 836 t/d: 1971-1979 1048 t/d: 1980-1984 867 t/d: from 1986 ✄
Typical Heat Consumption: 1966-1970 3.37 MJ/kg: 1971-1979 3.19 MJ/kg: 1980-1984 3.26 MJ/kg: from 1986 ✄

References:

Sources:

Primary Sources:
- Greenhithe Archive
- “The New Dunbar Cement Works”, Cement and Lime Manufacture, 37, January 1964, pp 1-18
- Dunbar Works, Blue Circle Publicity Department, 1967
- Ordnance Survey 1:2500 mapping
- BGS mapping, monographs and mine plans
- M. Scrutton, M. G. Jones. and J. P. Elvins, “Dunbar Cement Works quarry, East Lothian: 45 years on” in Proceedings of the 14th Extractive Industry Geology Conference, EIG Conferences, 2008, pp 12-20
Confirmatory Sources:
- Jackson, pp 222, 278
- Pugh, pp 144-146, 156-161