Notes from a conversation with Site Manager, Frank Stagg, on 13th January 1993:

The washery was built to service local drift mines in 1932. It has been substantially altered since, and was re-equipped in 1950.
1993:
Services two open cast sites: Nant Helen & Derlwyn- coal delivered by road.
Output to domestic anthracite market (30%) and Industrial (70%).
Industrial for manufacture of smokeless fuels.
Exports through Swansea, Neath Abbey, and Briton Ferry (Belgium).
Export taken by rail large proportion to France ?Agglonard?.
Norway ?Elken?.
Elken manufacture refractory blocks for furnaces (Aluminium smelting etc.)
Elken operate a calcining process. Coal has high voltage passed through it, raising temperature to 2,000 C to drive off volatile material, the carbon is then crushed mixed with paste and cast into blocks .
Plant was installed to produce 250 tons/hour, this has been reduced by modifications, but at present it produces 14,000 tons a week (to suit current market).
Water supply is from the mains (as opposed to Taff Merthyr which extracts from the Trelewis Drift.).
Majority of output is by road, this is really due to economics and rail costs. Waste goes back by road to opencast for infill.

I. N.Wright 13th January 1993


In 1998, Celtic Energy decided to build a new state-of-the-art coal preparation plant at Onllwyn coal washery, capable of processing the production from all its sites. The new plant, based around a Heavy Media Drum Separator for coal greater than 22 mm and Heavy Media cyclones for the small coal, can operate up to 24 hours per day processing up to 26,000 tonnes per week of raw mined production and converting it to top quality anthracite products. The plant produces 5 different sizes of products in each of the 3 different coal qualities, Black Diamond, Premium and Economy. In addition, specialist coals with unique size qualities are produced on a batch basis for major customers. The Froth Flotation Plant at Onllwyn was constructed in 2005 as a facility for recovery of fine coal from Washery slurry, which had until then been treated as discard. The palntis supplied by several nearby opencast sites, notably Nant-Helen (nprn 410795), Selar (nprn 410801) and Margam (nprn 410802).
(Source: Celtic Energy)
B.A.Malaws, RCAHMW, 07 May 2010.