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19
SMOKE ABATEMENT.
Nuisances from the emission of smoke from industrial chimneys
in the Borough arise chiefly from the use of unsuitable coal,
or through the absence of proper appliances for burning it.
In an atempt to reduce overhead charges, most of the laundries
and manufacturing companies purchase the cheapest fuel
possible, which is known in the trade as " duff ", namely, slack,
dust, or fine siftings of house or steam coal, costing from 20/- to 22/per
ton delivered, and such coal is not always washed.
The siftings of Welsh Steam Coal or semi-anthracite have a
high calorific value and give off little smoke, but the slack of coals
from Derbyshire and Nottingham—soft house coals—is highly bituminous
and gives off as much as one third of its weight in smoke.
It is therefore impossible to fire such coal by hand without causing
a nuisance.
A certain amount of skill is required of the stoker when firing
these soft slack coals, and the work is decidedly harder as there is
a tendency for the coal to cake or fuse together, and the hard tight
crust which is formed prevents air passing through the fire bed.
If this is not carefully watched combustion is impeded, except where
the crust cracks and air passes through. Any slowing down of combustion
naturally affects the amount of steam raised, and manufacturers
cannot as a rule meet their requirements for steam unless
the boiler is working at its full rated capacity.
To burn any soft coal it is necessary to stoke at frequent
intervals—not longer than 5 minutes—but this has the decided
disadvantage that every time the fire door is opened the cold air
which enters the furnace, reduces its temperature and also the temperature
in the combustion. chamber, with the consequence that
volumes of smoke are emitted from the chimney. It is also necessary
to break up with a slice bar the crust on the fire bed at frequent
intervals and during this operation volumes of dense smoke are
given off. Moreover forced draught is needed for burning this
class of coal with a result that coal-dust, grit and ash is blown up
the chimney. During the year six cases of nuisances from dust,
grit and ash were dealt with.
For burning "duff" satisfactorily, mechanical stokers are
necessary, and in one laundry where an under-feed mechanical
stoker was installed excellent results were obtained.
During the year the chimney of a certain manufacturing
company suddenly began to emit volumes of black smoke eveny few
minutes after being quite satisfactory for many years. On en-