The wall of the charcoal storage house at Duddon iron furnace, Cumbria is
vitrified in a similar manner to Scottish 'vitrified forts'. There was a
unanimous view by memebers of the Historical Metallurgy Society, who were
visting that this had been caused by a charcoal fire (spontaneous or
otherwise) and that the vitrified deposit started from low melting alkali
metal salts in wood ash formed a slag with the silicate components of the
wall.
On a personal note I have experienced spontaneous combustion with boiler
coal (<1/2" smalls) on a number of occasions. Once when we laid in large
stockpiles. Smouldering was overcome by spreading to about 2ft deep and
turning frequently to dissipate heat. Much of the coal was denatured or
lost as a result of what was believed to be prudence and we never did it
again. During the miners strike of the mid 1980's quite a lot of the
coal we received had been stockpiled and was very hot or smoking. Again,
stirring up to dissipate the heat and then putting into a well-designed
silo overcame the problem. While this was going on I visited a hospital
in Huddersfield where coal was stored in flat-bottomed bunkers with 'dead
corners'. Sprinkling water on top was unsuccessful or made matters worse
and removal was either not possible or very unsafe in an enclosed building.
In the end the fire brigade had to fill the bunker with water but the coal
was ruined.
The definitive advice we used at the time was a report by the National Coal
Board-Coal Research Establishment "Silos for Coal Storage", B. Rowlandson,
Oct 1982.
Richard Smith
3M UK Bracknell, B2-3N,
Environment, Safety and Security [log in to unmask]
Tel: 01344-858154 (Trim. 8-230-2154)
Fax: 01344-858367 (Trim. 8-230-2367)
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