Kent

Location:

Clinker manufacture operational: 1922-1970

Approximate clinker production: 15.8 million tonnes (29th)

Raw materials:

Ownership:

This was the largest of the plants built during Britain's "promoter" period. The original company was launched (17/6/16) to buy and install a large, modern, off-the-peg plant. Curiously, from 1920, this FLS plant had Sydney Greenwood Robinson - also a director of Tunnel and head of FLS's UK operation - as its Managing Director. It failed before the plant was complete, because of over-spend. It suffered a similar fate to other "promoter" ventures of the time. The original kilns were ordered from FLS in 1919 and the first kiln was already in place in early 1920. At this point the company was reconstituted with a doubling of capital and the promise to expand to a 6-kiln operation. With false starts and equipment failures, the company ran out of cash and folded. APCM bought it from the liquidator for about half the construction cost. The kilns were allegedly turning during 1921, but at the time of Blue Circle’s takeover, no finished product had been made, and it can be assumed that any previous kiln runs did not constitute “production”. Subsequently, the FLS-designed plant became something of an APCM showpiece and influenced the development of subsequent Blue Circle/Vickers designs: in his books, Davis used many photographs of the plant as illustrations of “state-of-the-art”. Kilns A1 and A2 were the largest in Britain until 1926 when they were overtaken by Bevans A1-A3. The plant was described in detail in the APCM 1924 schedule. The plant was operated by Blue Circle very much in concert with the adjacent Johnsons, with reserves strategically allocated between the two, and with the need for more capacity in the late 1930s, two more kilns were installed at Kent rather than Johnsons where the site was too cramped for expansion. Vickers Armstrong provided a new design for A3 and A4, presumably prompted by the craze for calcinator of the period: the calcinator experiment was quickly abandoned, and this precedent was applied with most of the calcinators that came under Blue Circle’s control.

The plant was provided with a rail link, but also despatched product by barge. After closure, the site was re-developed. A few fragments of the wharf remain: the plant site is covered by part of the Crossways industrial park.

Power Supply

The plant was electrically powered from the outset, initially using the central power house. This had initially one 3 MW turbo-generator and 250 kW diesel standby generator. This also supplied the kiln section of Johnsons from 1923. In 1925, two more turbo-generators were installed, supplying the whole of Kent and Johnsons. In 1955, both plants were switched to grid electricity.

Rawmills

Clay was washmilled separately (and from 1938 delivered as slurry by barge from Cliffe), and chalk brought from the quarry by rail was ground with the clay slip in three (four from 1938) washmills followed by Trix separators and two (four from 1938) FLS regrind mills.

Four rotary kilns were installed:

Kiln A1

Supplier: FLS
Operated: 1/1922 -30/04/1970
Process: Wet: chain system installed 1931.
Location: Hot end 557695,175275: Cold end 557687,175202: entirely enclosed.
Dimensions:

Rotation (viewed from firing end): clockwise.
Slope: 1/25 (2.292°)
Speed: ?
Drive: ?
Kiln profile:

Cooler:

Cooler profile:

Fuel: Coal, except 4/1960-5/1968 on Oil
Coal Mill: indirect: FLS Unidan combination mill shared by kilns 1 & 2
Exhaust: initially direct to stack. An ID fan was added in the early 1930s, and an electrostatic precipitator in 1962.
Typical Output: 1922-1931 313 t/d: 1931-1950 326 t/d: 1950-1960 344 t/d: 1960-1968 375 t/d: 1968-1970 314 t/d
Typical Heat Consumption: 1922-1931 9.51 MJ/kg: 1931-1950 7.85 MJ/kg: 1950-1960 7.69 MJ/kg: 1960-1968 7.90 MJ/kg: 1968-1970 8.50 MJ/kg

Kiln A2

Operated: 2/1922 -30/04/1970
Location: Hot end 557685,175276: Cold end 557677,175205: entirely enclosed.
Dimensions:

Kiln profile:

Exhaust: initially direct to stack. An ID fan was added in the early 1930s, and an electrostatic precipitator in 1961.
Typical Output: 1922-1931 313 t/d: 1931-1950 325 t/d: 1950-1960 348 t/d: 1960-1968 357 t/d: 1968-1970 296 t/d
Typical Heat Consumption: 1922-1931 9.50 MJ/kg: 1931-1950 7.65 MJ/kg: 1950-1960 7.70 MJ/kg: 1960-1968 7.86 MJ/kg: 1968-1970 8.41 MJ/kg
In all other respects identical to A1

Kiln A3

Supplier: Vickers Armstrong
Operated: 1938-30/04/1970
Process: Wet: originally fitted with calcinator. Since A4 had no calcinator, this was presumably an experiment to compare identical kilns with and without calcinators: it was removed 1946.
Location: Hot end 557705,175275: Cold end 557697,175204: entirely enclosed.
Dimensions (from cooler ports): 230’6⅛”× 10’10” (metric 70.26×3.302)
Rotation (viewed from firing end): clockwise?
Slope: ?
Speed: ?
Drive: ?
Kiln profile (from cooler ports): -597×2743: 1384×2743: 4432×3302: 70260×3302: Tyres at 6871, 23330, 44955, 66637.
Cooler: 12 × 14’6” × 3’11½” (metric 4.43×1.207) Reflex “Recuperator” planetary
Fuel: Coal, except 4/1960-5/1968 on Oil
Exhaust: via cyclones and an ID fan to stack.
Typical Output: 1938-1946 324 t/d: 1946-1960 348 t/d: 1960-1968 365 t/d: 1968-1970 322 t/d
Typical Heat Consumption: 1938-1946 7.84 MJ/kg: 1946-1960 7.87 MJ/kg: 1960-1968 7.95 MJ/kg: 1968-1970 8.49 MJ/kg

Kiln A4

Operated: 1939-30/04/1970
Process: Wet
Location: Hot end 557715,175273: Cold end 557707,175203: entirely enclosed.
Typical Output: 1939-1950 321 t/d: 1950-1968 360 t/d: 1968-1970 307 t/d
Typical Heat Consumption: 1939-1950 7.77 MJ/kg: 1950-1960 7.96 MJ/kg: 1960-1968 7.94 MJ/kg: 1968-1970 8.60 MJ/kg
Identical in all other respects to A3


Sources: