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19
For the abatement of smoke from the chief offender, the
domestic fire burning raw coal, there is on solution, the reasons
being that sufficient heat cannot be generated to burn the hydrocarbon
gases which are driven off. Many patent grates are on the
market, constructed to effect an economy in the consumption of
coal, but these do not in any way diminish the smoke emitted into
the atmosphere. Inventors have also turned their attention to
the construction of grates and ranges for burning coke, which are
very successful up to a point, the drawback being that one cannot
keep a coke fire low; to get the best results the fire should be deep
and high-banked. It has been found that the transformation of
coal to coke does not diminish the sulphur content by any appreciable
amount so that coke fires emit almost as much sulphur
dioxide into the air as coal fires, and as sulphur acids are the cause
of the corrosion of stone-work, deterioration of paint-work, &c.,
there is no advantage from burning of coke so far as this destructive
impurity is concerned, but it would be an advantage from the
point of view of a cleaner atmosphere and the abolition of dirty
fogs.
With regard to large steam raising plants such as Tower
Stations, the difficulty is the prevention of the emission of grit
and sulphurous acid gases. In such works no expense is spared
in providing the latest methods of burning coal as nearly smokeless
as possible, and thousands of pounds are spent in installing apparatus
for arresting grit and washing the flue gases. The best of these
appliances, I understand, will arrest from 85 to 95 per cent. of the
grit. the remainder being discharged into the air, and 98 per cent.
of sulphur dioxide can be removed from the smoke by washing.
The boilers in all large steam raising plants are fitted with combustion
chambers beyond the firegrates, and the temperature in
this chamber with the addition of the secondary air which is admitted
over the fire is sufficient to consume the volatile gases. Factory
chimneys, therefore, pollute the air far less with the tarry volatile
gases than domestic chimneys.
It can be readily understood that it is impossible to prevent
Smoke from steam raising plants when the fires are first lighted,
the temperature of the combustion chamber is not high enough
to consume the gases.
A really efficient grit arrester would not be suitable for small
stram raising plants, and the cost also would be prohibitive. The
practical remedy therefore, is to get the owners of such
plants to install suitable fire bars in their present boilers to burn
but if the boiler is being forced by the use of mechanical
draught in consequence of being too small in capacity, there would