Evening star. [volume] (Washington, D.C.) 1854-1972, 1910-06-27
DISCUSS COAL DUST
Topic at Meeting of Mining
Engineers in London.
THEORIES ARE ExPOUNDED
Infammability Of Free Carbon
Mixed With Free Oxygen Dwelt
on by Speaker.
Foreign Correspondence Of The Star.

LONDON, June II, 1910.
The fifty-second general meeting Of the
Institution Of Mining Engineers, just held
at Burlington House, was largely devoted
| to the question of coal dust. A paper on
experiments illustrative Of the infiamma'
bility of mixtures Of coal dust and air,
| read by Prof. P. Phillips Bedson. was
followed by a contribution from H. w.
G. Haulbaum on memoranda concerning
coal dust and the essential principles
Of the coal dust theory. There were,
he said two methods of expounding the
| coal dust theory-the scholarly or tech
nical way and the popular way Inc
theory had often been presented In
the scholarly way, but in his opinion
no man ever had expounded the theory
in such a manner that the ordinary
person might profit by the exposition.
Yet nine-tenths Of the efficiency Of the
theory depended upon the recognition
granted to it by the rank and file.
The great fundamental principle of
| the coal dust theory might be stated
thus: II any quantity Of free Cor APP
mixed with free Cor approximately
free) oxygen the mixture is inf1am-
mable. In this statement the phrase
| intimately mixed should really be print
tiers, for therein lay the whole philoso-
ply of coal dust explosions. The man
who read, marked. learned and inward
ly digested the above statement really
mastere the entire modern theory Of
coal dust explosions.
Intimate Mixture.
Suppose they took two pieces of lumy
sugar of equal size and threw one piece
in<4 <bo r h,,r cd
gishly If they ground the other piece
into the smallest dust and scattered the
sugar dust thus obtained upon the fire
they obtained a miniature explosion
Why? Because the sugar dust was more
intimately mixed with air. and therefore
with oxygen. A single lump OF coal, say
ten pounds in weight. was not explosive
and If thrown on the fire it burned slow
ly But ten pounds of coal dust. finely
divided and raised by some shock as
cloud In the air, was explosive, because
% being finely divided, and 60 being
raised in cloud in the air. it became In
timately mixed with the air. and hence
was nothing more nor less than an init
mate mixture Of carbon and hydrocarbor
with oxygen.
The lesson was clear. If they wanted
the highest explosive effects in dynamites
and gunpowders they must mix the In
gradients intimately. But II, on the Other
hand, they wanted to prevent coal dust
explosions, they must guard against the
possibility of the coal dust becoming In
timately mixed with the air Of the mine
The remedy for coal dust was obvious
Either remove the dust, cake 1t, or use
q counter absorbent of heat. Watering
would cake 10 and the water would also
absorb part Of the heat Calcium chloride
would absorb much heat, leaving so much
less to be absorbed by the coal dust. The
coal dust In an airway measuring five
feet by ten feet was most dangerous
when 1t was scattered on the surfaces
of the airway to an average depth OF
only a three-hundredth part Of an inch
Large Quantities Less Dangerous.
It therefore followed that large quanti-
ties of coal dust were possibly less
dangerous than small quantities. It was
consequently clear that the dangers Of
coal dust could no be much lessened by
the removal of 1t, unless the removal be
absolute, which was impossible. The
remedies for the coal-dust danger might
be suggested by the character OF the
danger. Any shock that might raise the
dust as cloud in the air should be con,
tinuously guarded against. The ability
Of the dust to rise in the air should
be minimized by laying 1t and cakins
it by watering.
ANY sudden accession OF heat should
be guarded against ta) by the prevention
of blown-out shots; tb) by the thorough
insulation of electric currents; (c) by
strict regulations concerning the use and
care Of detonators, and (dD by the
maintenance of perfect discipline in the
mine. Any sudden accession of heat
should not only be guarded against, but
should be provided for II 1t occurred.
In the course Of a discussion of the
explosive nature of cuel dust ]. B. At
kinson inspector of mines. Northumber-
land) said that 1t was unfortunately true
that many avenues Of main mines con-
tanned the elements of violent explosions.
There was no question In his mind that
an excess OF coal dust did not arrest an
ex nlnsion once II had been eStabItShed.