Clinker manufacture operational: 1957 to date

Approximate total clinker production: 40 million tonnes (7th)

Raw materials:


Cauldon was the first modern energy-efficient plant to be installed in Britain and Ireland, and only the second Blue Circle green-field development (the first being Hope, 28 years earlier). The limestone of Cauldon Low had been used fairly intensively for centuries to make lime. The plant was planned as part of Blue Circle’s post-war development, and the original plan was for a wet process, with one Shoreham-style kiln. The primary stated reason for examining the dry process option was a shortage of water supply at Cauldon. The suspension preheater system was still regarded with suspicion concerning emissions and stability, so the Lepol system was selected. Lepol kilns had operated in Germany from the late 1920s, and were the dominant process there by the time of the war. A pilot scale system was first operated at Barnstone to establish that the Cauldon materials would work. The first kiln was second (to West Thurrock A6) in capacity when installed, and was also by far the most efficient, the only challengers being the tiny shaft kilns at Plymstock and South Ferriby.

Early performance data was unreliable: kiln energy consumption below 3 MJ/kg was claimed.

However, by any standard, the plant was efficient and productive, and many further Lepol kilns were installed during the 1960s, spearheading the new drive towards efficiency.

The rawmix was ground in the combined raw- and finish-mill house adjacent to the kiln house, but kiln waste heat was not used for raw material drying. The initial installation used pulverised coal to heat the rawmills, using a claimed 0.70 MJ/kg. From 1960, fuel oil was used, consumption being typically 0.40 MJ/kg.

The plant was expanded with two more kilns of roughly the same size, to become Blue Circle's largest 1963-1966. However, the kilns were smaller and somewhat less efficient than the next-generation Lepol kilns installed in the late 1960s, and in 1985 they were replaced by a single precalciner kiln – Blue Circle’s first in Britain. The economic case for the change was primarily to reduce labour costs by simplifying the plant and allowing operation by a much smaller workforce. The rawmill integrated into the kiln system is heated by kiln exhaust gas.

Although the Cauldon Low quarry had a rail link, this was never extended to the plant, and the plant has always used road transport exclusively. Although both plants were highly efficient, there was always an uneasy rivalry between Cauldon and Hope, because they are close together and potentially serve the same market. Because Hope had a rail link, Lafarge invested in up-rating it, so that Hope could concentrate on serving more distant markets, while Cauldon handled the more local Midland region. The sale of Hope to ArcelorMittal in 2013 consolidated this position.

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).


Four distinct rotary kilns were installed:

Kiln A1

Supplier: kiln - Vickers Armstrong: grate - Polysius
Operated: 25/4/1957 to 1985
Process: Semi-dry: Lepol 20.9×3.91 m grate
Location: hot end 408492,349562: cold end 408500,349515: entirely enclosed.
Dimensions: 158’0”× 12’6” (metric 48.16 × 3.810)
Rotation (viewed from firing end): anti-clockwise
Slope: ?
Speed: ?
Drive: 67 kW
Kiln profile: 0×3810: 47092×3810: 47803×3010: 48158×3010: tyres at 3048, 22250, 42367: turning gear at 39014.
Cooler: Fuller 748S grate beneath kiln: 10° slope.
Fuel: Coal
Coal Mill: VKW Berz MB16 roller mill - initially semi-indirect and used also to heat rawmills - from 1960, used direct.
Exhaust: twin parallel chamber electrostatic precipitator before ID fan.
Typical Output: 1957-1972 651 t/d: 1972-1985 680 t/d
Typical Heat Consumption: 1957-1963 3.18 MJ/kg: 1963-1974 3.79 MJ/kg: 1974-1985 3.59 MJ/kg

Kiln A2

Supplier: Polysius
Operated: 9/8/1960 to 1985
Process: Semi-dry: Lepol 20.9×3.91 m grate
Location: hot end 408505,349564: cold end 408512,349516: entirely enclosed.
Dimensions: metric 48.12 × 3.750
Rotation (viewed from firing end): anti-clockwise
Slope: ?
Speed: ?
Drive: ?
Kiln profile: 0×3340: 864×3340: 1753×3750: 47120×3750: 47831×3025: 48120×3025: tyres at 3835, 24435, 38430: turning gear at 35430?
Cooler: Recupol P1616 grate
Fuel: Coal
Coal Mill: direct: Polysius ball mill
Exhaust: twin parallel chamber electrostatic precipitator before ID fan.
Typical Output: 1960-1972 639 t/d: 1972-1985 687 t/d
Typical Heat Consumption: 1960-1964 3.27 MJ/kg: 1964-1975 3.85 MJ/kg: 1975-1985 3.64 MJ/kg

Kiln A3

Supplier: Polysius
Operated: 3/8/1962 to 1983
Process: semi-dry: Lepol 20.9×3.91 m grate
Location: hot end 408517,349566: cold end 408524,349518: entirely enclosed.
Dimensions: metric 48.16 × 3.750
Rotation (viewed from firing end): ?
Slope: ?
Speed: ?
Drive: ?
Kiln profile: 0×3340: 900×3340: 1790×3750: 47160×3750: 47870×3025: 48160×3025: tyres at 3886, 24486, 38456: turning gear at 35456?
Cooler: Fuller 744H grate
Fuel: Coal
Coal Mill: direct: Berz MB16 roller mill
Exhaust: twin parallel chamber electrostatic precipitator before ID fan.
Typical Output: 1962-1973 633 t/d: 1973-1983 697 t/d
Typical Heat Consumption: 1962-1973 3.80 MJ/kg: 1973-1983 3.61 MJ/kg

Kiln B1

Supplier: FLS
Operated: 1985 to date
Process: single string 4-stage suspension preheater with in-line air-separate precalciner (FLS 41P ILC)(1): dimensions ✄
Location: hot end 408517,349566: cold end 408525,349509: entirely enclosed.
Dimensions: metric 58.00 × 3.950(2)
Rotation (viewed from firing end): clockwise(3).
Slope: ?
Speed: ?
Drive: ?
Kiln profile: ✄
Cooler: Claudius Peters grate: dimensions✄
Fuel: ✄
Coal Mill: indirect: MPS 140 roller mill(2).
Exhaust: ✄
Typical Output: ✄
Typical Heat Consumption: ✄


Sources: Jackson, pp 218, 276: Pugh, p 156: "New Cement Works in Staffordshire", Cement and Lime Manufacture, 30, Nov 1957, pp 77-89: “Cauldon Cement Works”, The Engineer, CCIV, 11/10/1957, pp 529-532: Cauldon Works, Blue Circle Publicity Department, 1957.