• Grid reference: SJ52718574
  • x=352710
  • y=385740
  • 53°21'59"N; 2°42'38"W
  • Civil Parish: Widnes, Lancashire

Clinker manufacture operational: 1955-1973

Approximate clinker production: 2.3 million tonnes

Raw materials:

  • Anhydrite (Permian: Eden Shales Formation: 251-271 Ma: B-bed and D-bed Evaporite Members) from Long Meg mine, Addingham, Cumberland, drift mine entrance at 356270,537750. Operated by British Plaster Board (Holdings) Ltd; later British Gypsum
  • Originally sand and ash were used, but later shale from ?

Ownership: United Sulfuric Acid Corporation

Alternatively called the Green Oak Works. The anhydrite process sulfuric acid plant was built essentially to ICI designs and specifications, in response to restricted availability of elemental sulphur in the 1950s.

USAC, which owned and operated the Widnes anhydrite process sulphuric acid and cement plant, was essentially a consortium of ICI sulfuric acid customers. As founded (May 1951), it was a partnership of the following:

  • The Alumina Co. Ltd
  • Thomas Bolton & Sons Ltd
  • British Celanese Ltd
  • British Enka Ltd
  • Clayton Aniline Co. Ltd
  • Courtaulds Ltd
  • James H. Dennis & Co. Ltd
  • Fisons Ltd
  • Imperial Chemical Industries Ltd
  • McKechnie Bros Ltd
  • Transparent Paper Co. Ltd

APCM was not involved in the consortium, but undertook to grind the clinker and distribute the cement product. The project was supported and underwritten by the Ministry of Materials.

Unlike Billingham and Whitehaven, which were built literally on top of their raw materials, the location of the Widnes plant was dictated by the need to minimise transportation distances for the acid product, since cost per km for this was high, and the market for the acid in the Widnes/Runcorn area was large. (ICI had seriously considered a pipeline from Billingham to Widnes as an alternative strategy.) The plant here was essentially the same as the S3 unit at Billingham.

Closure in 1973 was associated with the rise in energy prices and fall in the price of elemental sulphur. The Long Meg mine closed shortly after in January 1976. The cement site remained a Blue Circle depot for a while and has only recently been cleared.


Raw materials dried by separate oil-fired driers fed to two 450 kW Ernest Newell tube mills - open circuit?

Two rotary kilns were installed:

Kiln A1

Supplier: Edgar Allen
Operated: 21/4/1955 - 14/1/1973
Process: Anhydrite
Location: Hot end 352674,385711: Cold end 352764,385770: unenclosed.
Dimensions (from cooler ports): 353’0” × 13’0”B / 10’0”C / 13’0”D (metric 107.59 × 3.962 / 3.048 / 3.962)
Rotation (viewed from firing end): anticlockwise
Slope: 1/25 (2.292°)
Speed: 0.50-1.05 rpm
Drive: 113 kW
Kiln profile (from cooler ports): -610×3962: 28346×3962: 32004×3048: 96012×3048: 99670×3962: 107594×3962: tyres at 7010, 24841, 43536, 63779, 84887, 103784: turning gear at 48692
Cooler: Reflex planetary coolers 10 ×15’?×4’?
Fuel: 1955-1965? Coal: 1965?-1973 Oil
Coal Mill: ?uncertain. The kilns were apparently originally indirect-fired; Newell tube mills may have been used, but Atritors for direct firing may have been installed ~1959.
Exhaust: suction provided by acid plant blowers and scrubbed by acid plant gas cleaning.
Typical Output: 1955-1968 220 t/d: 1969-1973 224 t/d
Typical Heat Consumption: 1955-1968 8.20 MJ/kg:1969-1973 8.09 MJ/kg

Kiln A2

Operated: ?5/7/1955 - 14/1/1973
Location: Hot end 352669,385719: Cold end 352759,385778: unenclosed.
Identical in all other respects to A1.

Sources: Cook, pp 116-117: Jackson, p 302: D. W. F. Hardie, J. Davidson Pratt, A History of the Modern British Chemical Industry, Pergamon Press Ltd., 1966, pp 125, 325: a fair amount of information is to be found in the archive of the Catalyst Museum, Widnes: Plant Brochure (Catalyst Archive 1996.37): The Design and Construction of the United Sulphuric Acid Corporation Factory at Widnes, Lancs, ICI General Chemicals Division Chief Engineer’s Department Report, 6/2/1958 (Catalyst Archive 1996.42): USAC, Engineering Manager’s Monthly Reports (Catalyst Archive 2009.1).

The plant as installed was configured as follows:

Anhydrite, crushed at the mine to -100 mm, was received by rail (in a fleet of 150 26 t hopper-bottom trucks, and held in a 3000 t covered store, with an open-air stockyard as overflow. From this it was extracted and passed through cone crushers (Nordberg) to -12 mm and stored in rawmill feed bunkers.

Shale, sand (later dropped from the rawmix) and coke were received from local sources and stocked in the open air. Shale was passed through one of two hammer crushers (British Jeffrey Desmond) before feeding through one of two rotary dryers (Head Wrightson) heated by light fuel oil. The sand and coke were passed to the dryers as received. Dried materials were stored in separate rawmill feed bunkers.

The raw materials were extracted and weighed (Richard Simon) onto common rawmill feed belts, and conveyed to two 450 kW tube mills (Ernest Newell). The raw meal was ground to typically 7% >150 μm, at typically 14 t/hr. The coarse grind was intended to reduce kiln dust pickup, but also contributed to the very low outputs and high fuel consumptions of the kilns. The raw meal was stored in a set of 9 1000 t silos common to the two kiln systems. Meal was blended by recirculation with elevators and air-slides.

There were two Edgar Allen kilns of dimensions 355 × 13 / 10 / 13 ft, running on 6 tyres, and driven by a 113 kW motor through a fluid coupling to a spur wheel just above the 3rd tyre, giving speed variable from 0.50 to 1.05 rpm. The kilns were sloped at 1 in 25, and discharged into reflex planetary cooler tubes.

The meal was fed by pipe to the kiln back ends. The kilns were bricked throughout and had no other internals. The kilns were originally indirect-fired with coal, but were converted to oil firing in the mid-1960s.

Each kiln’s exhaust gas, containing around 9% SO2, was ducted through a cyclone returning most of the dust to the kiln feed elevator. It then passed through a conditioning tower to cool it and remove further dust. The water effluent was stripped of most of its dissolved SO2 by treatment with hot air in counter-current, and the latter was returned to the process. The cooled gases were passed through a set of mist precipitators (Power Gas Corporation: 10 for each kiln) to remove mist and the remaining dust. Finally, the moist gas was passed through scrubber dryer towers fed with sulphuric acid to remove the remaining water.

The cool gas now consisted only of nitrogen, SO2, CO2 and oxygen. The gas was further diluted with air to give around 6.5% SO2 content, so that there was about a two-fold excess of oxygen present. At this stage the gas passed through fans (“blowers”: Bryan Donkin, 113 kW, 3 per kiln) which supplied the sole gas-flow energy for the entire process.

The gas now passed into the converter unit in which SO2 was oxidised to SO3 by contact with a V2O5 catalyst at 420-450ºC. The process is exothermic, and the inlet gas was heated to reaction temperature, and the outlet gas cooled, by passing them through a counter current heat exchanger. Yield was maximised by repeating the process 4 times, after which the gas was passed through a cooler to the absorber towers, located next to the scrubber dryers mentioned above. Here the SO3 was dissolved in re-circulated 98% sulphuric acid, with water bled in to maintain a constant strength.

The acid was passed through coolers and stored in six 750 t tanks for 98% acid and three 500 t tanks for 20% oleum. From here it was pumped to road and rail loading points.

Finally, the remaining gas, which contained a fraction of a percent of residual SO2, was water scrubbed and passed through a precipitator before emission to atmosphere.

The clinker from the coolers dropped onto shaker conveyors via vibraflows to a set of five 1000 t bunkers and an 18,000 t covered store. The extraction points under the store marked the start of the APCM part of the process. The clinker was conveyed to the feed hoppers of two Vickers Armstrong open circuit 3-chamber finish mills: No1 900 kW, making 28 t/hr and No2 450 kW, making 14 t/hr on OPC. The product was conveyed by drag conveyor and elevator to two 1800 t bulk silos and four 1000 t packing silos. The plant had rail and road loading facilities, and could bring in conventional process clinker to “sweeten” the USAC product.