Clinker manufacture operational: 1953 - 23/12/1998
Approximate total clinker production: 12.2 million tonnes (35th).
Raw material: Devonian Limestone (Middle Devonian Limestone: 385-398 Ma) from the Saltram Quarry at 251400,054300
This was the most southerly cement plant, and the most westerly in Great Britain: as a far-flung part of the country, the cost of cement delivery from the Thames was high, and a cement plant here was planned as early as the late 1930s by the owners of the limestone quarries at Plymstock. Interrupted by the war, the plant finally commenced operations on a small scale with a shaft kiln using the "black meal process": a second one was added three years later. Technical management was supplied by Cementia. These kilns were operated independently, but their inputs and outputs were combined. The kiln feed was dry-ground and blended, then nodulized in a pan nodulizer with the addition of 12.6% water. On acquisition by Blue Circle, the shaft kilns were replaced by rotary kiln A1. This was the first British suspension preheater kiln, and the third efficient kiln to be installed, preceded only by Cauldon A1 and A2 Lepol kilns. The experience with the shaft kilns was sufficient to show that the material did not nodulize well, so the “Humboldt” preheater, which had the majority of the market at the time, was selected in preference to the Lepol grate.
Please contact me with any relevant information or corrections. I am particularly interested in firmer dates and statistics.
Operated: #1 2/1954-1961: #2 1956 (1st half)-1961
Process: Semi-dry: shaft kiln
Location: kiln 1 at 250669,54344; kiln 2 at 250646,54348.
Typical Output (each): 115 t/d
Typical Heat Consumption: 4.87 MJ/kg
Two rotary kilns were installed.
Supplier: kiln - Vickers Armstrong: preheater - KHD.
Process: Dry SP4 suspension preheater
Location: hot end 250657,054261: cold end 250710,054272: entirely enclosed
Dimensions: 178’0”× 12’6” (metric 54.25×3.810)
Rotation (viewed from firing end): anticlockwise
Slope: 1/33.33 (1.719°)
Speed: 1.4 rpm
Drive: 67 kW
Kiln profile: 0×3810: 53861×3810: 53861×3251: 54254×3251: tyres at 3658, 24994, 47854: turning gear 45415.
Cooler: Fuller 741H grate
Fuel: 1961-1979 Oil: 1979-1981 Coal
Coal mill: ?
Exhaust: preheater gases via the rawmill to two parallel electrostatic precipitators then through the precipitator ID fan to the stack.
Typical Output: 1961-1972 702 t/d: 1972-1981 748 t/d
Typical Heat Consumption: 1961-1977 3.80 MJ/kg: 1977-1981 4.13 MJ/kg
Process: Dry SP4 suspension preheater: fitted with afterburner 1990
Location: hot end 250660,054246: cold end 250713,054257: entirely enclosed
Cooler: Claudius Peters 744H grate
Fuel: 1966-1978 Oil: 1978-1998 Coal, in the last few years up to 20% replaced with Petcoke.
Coal mill: Babcock & Wilcox 5E ball-race mill (1575 mm)
Typical Output: 1966-1972 781 t/d: 1972-1978 864 t/d: 1978-1986 831 t/d: 1986-1998 913 t/d
Typical Heat Consumption: 1966-1978 3.76 MJ/kg: 1978-1998 4.06 MJ/kg
In all other respects identical to A1
Sources: Cook, pp 102, 116-117: Jackson, pp 250, 292: Pugh, p 144: "Developments at a Cement Works in Britain", Cement and Lime Manufacture, 33, July 1960, pp 49-53: "A New Rotary Dry-process Kiln in Gt. Britain", Cement and Lime Manufacture, 35, Jan 1962, pp 1-8, 23-28.