Cement Kilns

Dunstable

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Location:

  • Grid reference: TL0160323415
  • x=501603
  • y=223415
  • 51°54'1"N; 0°31'24"W
  • Civil Parish: Houghton Regis, Bedfordshire

Clinker manufacture operational: 1926 - 1971

Approximate total clinker production: 11.1 million tonnes (37th)

Raw materials:

  • Middle Chalk (Holywell Nodular Chalk Formation: 92-94 Ma), Grey Chalk (Zig-zag Chalk Formation: 94-97 Ma) and Chalk Marl (West Melbury Marly Chalk Formation: 97-100 Ma) from quarry at 500900,223500
  • Grey Chalk from quarry at 492300,222500
  • Chalk Marl and Gault Clay (Gault Formation: 100-112 Ma) from pit at 500900,224100

Ownership:

The plant was a Maxted & Knott design and was successfully commissioned before the Red Triangle takeover. The plant typified the Red Triangle acquisition policy in that it was superficially up-to-date, although not necessarily technically well-conceived.

The bizarre shapes of kilns A1-3 arose from a succession of ad hoc modifications. The original kilns had no enlarged sections: Edgar Allen was firmly against these at the time. Desiccators were added to these in the 1930s – the latter could not be added to the end of the kiln because of load considerations, so they were placed before the fourth tyre, and the kilns were truncated. At the same time, the third kiln was added, and precipitators and a common stack were added, the latter being on the centre-line of A2. The third kiln was in the standard Vickers Armstrong format, with enlarged burning zone and desiccator. Subsequently, in a further attempt to increase capacity, A1 and A3 were lengthened with the addition of a further pier, using tube of standard diameter. This was not possible for A2 because of the position of the stack.

Lime had been made by Forders at Sundon, Sewell and Blows Down nearby, and these small plants were replaced by a new plant at Dunstable in 1935, using the Totternhoe Stone intervening between the Chalk Marl and Grey Chalk in the main quarry: there was a block of fifteen kilns by 1938. These were cleared in 1964, making way for the press house for the semi-wet kiln A4 commissioned in 1966. The entirely in-house designed semi-wet project was mis-conceived: the smectite-bearing argillaceous component was unsuitable for pressing, and the Davis preheater had insuperable technical defects. The result was Blue Circle’s shortest-running kiln, with an operating life of less than five years, and a massive capital write-off. Had the plant survived beyond the 1973 energy crisis, the economics of persevering with it might have improved, but the plant had to shut to justify what was increasingly clearly a white elephant at Northfleet. The site remained as a depot for Northfleet cement. The plant used a spur of the Welwyn-Leighton Buzzard railway for transportation: the Dunstable-Luton section continued in operation solely for the plant after the line closed for other traffic in 1965, and remained in operation until the depot closed in 1990. The plant site was cleared and is now covered by an industrial estate, although a few foundations remain around the periphery. The quarries remain un-developed and overgrown.

Rawmills

Washmill systems were established at the various quarries and pumped slurry to the plant.

  • The initial two-kiln plant had one 20’ 75 kW washmill at the marl quarry making slurry that was pumped to the upper quarry, where it was inter-ground with Middle Chalk in two similar washmills, followed by a set of nine screeners with total power 75 kW.
  • The two-stage system was subsequently abandoned and all materials were fed to two 112 kW washmills.

Four rotary kilns were installed:

Kiln A1

Supplier: Edgar Allen
Operated: 9/1926-08/06/1970
Process: Wet
Location: hot end 501595,223380: cold end 501582,223455: unenclosed.
Dimensions:

  • 1926-1937? 200’0” × 9’8½” (metric 60.96 × 2.959)
  • 1937?-1948? 187’6”× 9’8½”B / 12’10¼”C / 9’7½”D (metric 57.15 × 2.959 / 3.918 / 2.934)
  • 1948?-1970 245’8” × 9’8½”A / 12’10¼”C / 9’7½”D (metric 74.88 × 2.959 / 3.918 / 2.934)

Rotation (viewed from firing end): initially anticlockwise: from 1948 clockwise.
Slope: 1/24 (2.388°)
Speed: 1.0 rpm
Drive: 45 kW
Kiln profile:

  • 1926-1937? 0×2350: 610×2350: 2337×2959: 60960×2959: tyres at 4089, 19101, 36830, 54559: turning gear at 34798
  • 1937?-1948? 0×2350: 610×2350: 2337×2959: 43967×2959: 45796×3918: 51511×3918: 53340×2934: 55778×2934: 56236×2134: 57150×2134: tyres at 4089, 19101, 36830, 54559: turning gear at 34798
  • 1948?-1970 0×2350: 610×2350: 2337×2959: 43967×2959: 45796×3918: 51511×3918: 53340×2934: 73508×2934: 73965×2134: 74879×2134: tyres at 4089, 19101, 36830, 54559, 72288: turning gear at 34798

Cooler: Rotary 60’0”× 6’0” (metric 18.29 × 1.829) beneath firing floor
Cooler profile: : 0×1829: 305×1829: 1829×2438: 5791×2438: 7315×1829: 18289×1829: Tyres at 3658, 11430.
Fuel: Coal
Coal Mill: Direct: Rema roller mill supplemented with Atritor
Typical Output: 1926-1932 176 t/d: 1932-1947 241 t/d: 1947-1966 297 t/d 1966-1970 286 t/d
Typical Heat Consumption: 1926-1932 9.15 MJ/kg: 1932-1938 8.57 MJ/kg: 1938-1951 8.10 MJ/kg: 1951-1966 8.37 MJ/kg: 1966-1970 9.12 MJ/kg


Kiln A2

Supplier: Edgar Allen
Operated: 9/1926-08/06/1970
Process: Wet
Location: hot end 501604,223382: cold end 501594,223438: unenclosed.
Dimensions:

  • 1926-1937? 200’0” × 9’8½” (metric 60.96 × 2.959)
  • 1937?-1970 187’6”× 9’8½”B / 12’10¼”C / 9’7½”D (metric 57.15 × 2.959 / 3.918 / 2.934)

Rotation (viewed from firing end): clockwise.
Slope: 1/24 (2.388°)
Speed: 1.0 rpm
Drive: 45 kW
Kiln profile:

  • 1926-1937? 0×2350: 610×2350: 2337×2959: 60960×2959: tyres at 4089, 19101, 36830, 54559: turning gear at 34798
  • 1937?-1970 0×2350: 610×2350: 2337×2959: 43967×2959: 45796×3918: 51511×3918: 53340×2934: 55778×2934: 56236×2134: 57150×2134: tyres at 4089, 19101, 36830, 54559: turning gear at 34798

Cooler: Rotary 60’0”× 6’0” (metric 18.29 × 1.829) beneath firing floor
Cooler profile: 0×1829: 305×1829: 1829×2438: 5791×2438: 7315×1829: 18289×1829: Tyres at 3658, 11430.
Fuel: Coal
Coal Mill: Direct: Rema roller mill supplemented with Atritor
Typical Output: 1926-1932 202 t/d: 1932-1942 294 t/d: 1942-1951 270 t/d: 1951-1958 278 t/d: 1958-1966 293 t/d: 1966-1970 252 t/d
Typical Heat Consumption: 1926-1932 8.86 MJ/kg: 1932-1951 8.22 MJ/kg: 1951-1966 8.82 MJ/kg: 1966-1970 9.36 MJ/kg


Kiln A3

Supplier: Vickers Armstrong
Operated: 1937-08/06/1970
Process: Wet
Location: hot end 501613,223383: cold end 501600,223457: unenclosed.
Dimensions:

  • 1937-1952 187’6”× 10’6”B / 9’0”C / 12’0”D (metric 57.15 × 3.200 / 2.743 / 3.658)
  • 1953-1970 245’8” × 10’6”B / 9’0”C / 12’0”/ 9’0”D (metric 74.88 × 3.200 / 2.743 / 3.658 / 2.743)

Rotation (viewed from firing end): clockwise
Slope: 1/24 (2.388°)
Speed: 1.0 rpm
Drive: 45 kW
Kiln profile:

  • 1937-1952 0×2743: 3048×2743: 4115×3200: 16307×3200: 17374×2743: 38176×2743: 40005×3658: 51435×3658: 53264×2743: 55778×2743: 56236×2134: 57150×2134: tyres at 1829, 18593, 36881, 54559: turning gear at 34747
  • 1953-1970 0×2743: 3048×2743: 4115×3200: 16307×3200: 17374×2743: 38176×2743: 40005×3658: 51435×3658: 53264×2743: 73508×2743: 73965×2134: 74879×2134: tyres at 1829, 18593, 36881, 54559, 72288: turning gear at 34747

Cooler: Rotary 59’10”× 6’4” (metric 18.24 × 1.930) beneath firing floor
Cooler profile: 0×1930: 152×1930: 1118×2330: 5080×2330: 6045×1930: 18237×1930: Tyres at 3810, 14630.
Fuel: Coal
Coal Mill: Direct: Rema roller mill supplemented with Atritor
Typical Output: 1937-1948 264 t/d: 1948-1952 283 t/d: 1952-1956 306 t/d: 1956-1959 266 t/d: 1959-1966 302 t/d: 1966-1970 268 t/d
Typical Heat Consumption: 1937-1952 8.20 MJ/kg: 1952-1956 8.41 MJ/kg: 1956-1959 8.13 MJ/kg: 1959-1966 8.50 MJ/kg: 1966-1970 9.10 MJ/kg


Kiln A4

Supplier: Vickers Armstrong
Operated: 15/08/1966-31/3/1971
Process: Semi-wet: Davis Preheater
Location: hot end 501625,223383: cold end 501615,223443: entirely enclosed.
Dimensions: 200’0”×14’0”BC / 15’0”D (metric 60.96 × 4.267 / 4.572)
Rotation (viewed from firing end): ?
Slope: ?°
Speed: ?
Drive: ?
Kiln profile: 0×3658: 737×3658: 2743×4267: 47396×4267: 51816×4572: 60960×4572: Tyres at 4572, 26822, 52730
Cooler: Fuller 850H grate
Fuel: Coal
Coal Mill: Direct: MPS100 roller mill
Typical Output: 894 t/d
Typical Heat Consumption: 4.82 MJ/kg



Sources: Cook, pp 72, 75: Jackson, pp 223, 278: Pugh, pp 109, 154-155, 263: “The Dunstable Portland cement works”, The Engineer, CXLV, January 27, 1928, pp 92-94, 104; February 3, 1928, pp 120-123


© Dylan Moore 2011: commenced 24/01/2011: last edit 31/12/2016.

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Old Maps

Dunstable Detail

Approximate capacity: tonnes per year
Dunstable Capacity

Picture: ©English Heritage - NMR Aerofilms Collection. Britain from Above reference number EPW019203.
Britain from Above features some of the oldest and most valuable images of the Aerofilms Collection, a unique and important archive of aerial photographs. You can download images, share memories, and add information. By the end of the project in 2014, 95,000 images taken between 1919 and 1953 will be available online.
This was taken on 29/8/1927 as part of a series commissioned by Red Triangle during purchase of this and other plants and shows it from the southwest. The coolers were below the firing floor, and, as at Humber, emerged in the open air just this side of the kiln building. The clinker stockpile, using the pictures and the map, can be calculated to contain 40-50,000 tonnes. The capacity of the plant at this time was 120,000 tonnes per year, and it had been running for about a year. This gives some indication of the conditions under which Red Triangle was purchasing the plant from its luckless promoters. View in High Definition.

Picture: ©English Heritage - NMR Aerofilms Collection. Britain from Above reference number EPW019210.
This was taken on 29/8/1927 as part of the same series and shows the plant from the southeast. Here we also get a view of the quarry area. The lower Chiltern escarpment runs across the top of the picture. The main washmills are across the road from the plant and are served by the Grey Chalk quarry that worked downwards from the hill top. The toe of the Chalk Marl outcrop, overlying Gault Clay, ran along the base of the escarpment near the tree-lined hedge. Chalk Marl was being extracted here and washmilled, and the slurry was pumped to a holding tank at the main washmills. The two-stage system was later abandoned when the hill-top quarry had been extended down far enough to access both materials from a single working. Here, as at Sundon, Arlesey and Barrington, Chalk Marl was irritatingly referred to as "clay", although it usually contained over 60% calcium carbonate. View in High Definition.