In the case of the Consett furnace they were obtained although the
heat of the blast was under 1,100° Fahr., while heats of 1,500° to
1,600° are not uncommon at the present day in brick stoves, thanks to
the application of the regenerating principle of ex-president Sir W.
Siemens.
But an economy which promises to be of great importance is now sought
in the recovery and useful application of those constituents of coal
which, in the coking process, have hitherto been lost; or, as an
alternative, in a similar recovery in those cases in which the coal is
charged in a raw state into the blast furnace, as is the practice in
Scotland and elsewhere. This recovery of the hydrocarbons and the
nitrogen contained in the coal, and their collection as tar and
ammoniacal liquors, and subsequent conversion into sulphate of ammonia
as to the latter, and into the various light and heavy paraffin oils
and the residual pitch as to the former, have now been carried on for
a considerable time at two of the Gartsherrie furnaces; and they are
already engaged in applying the necessary apparatus to eight more
furnaces. In the coke oven the recovery of these by-products--if that
name can be properly applied to substances which yield the most
brilliant colors, the purest illuminants, and the flesh-forming
constituents supplied by the vegetable world--would appear at first
sight to be simpler; but it has presented its own peculiar
difficulties; the chief of which was, or was believed to be, a
deterioration in the quality of what has hitherto been the principal,
but what may, perhaps, come to be regarded hereafter as the residual
product, namely, the coke. But the more recent experience of Messrs.
Pease, at Crook, appears not to justify this opinion. You will see on
our table specimens of the coke produced in the Carves-Simon oven,
yielding 75 to 77 per cent. of coke from the Pease's West coal, which
they have now had at work for several months. Twenty-five of these
ovens are at work, and the average yield of ammoniacal liquor per ton
of coal has been 30 gallons of a strength of 7° Twaddell, valued at
1d. per gallon at the ovens; the quantity of tar per ton has been 7
gallons, valued at 3d. per gallon. These products would therefore
realize 4s. 3d. per ton of coal. Of course the profit on the ton of
coke is considerably more, and to this has to be added the value of
the additional weight of coke, which in the ordinary beehive ovens
from coal of the same quality is only 60 per cent. or in beehive ovens
having bottom flues about 66 per cent., while in the Carves ovens it
is, as I have said, upward of 75 per cent. Against these figures there
is a charge of 1s. 4d. per ton of coke for additional labor, including
all the labor in collecting the by-products; the interest on the first
cost of the plant, which is considerable, and probably some outlay for
repairs in excess of that in the case of ordinary ovens, has also to
be charged. Mr. Jameson takes credit for the combustible gas, which is
used up in the Carves ovens, but which remains over in his process,
and is available, though not nearly all consumed, in raising steam for
the various purposes of a colliery, including, no doubt, before long,
the generation of electricity for its illumination. It is right to
state that prior to 1879 Mr. Henry Aitken had applied bottom flues for
taking off the oil and ammoniacal water to beehive ovens at the Almond
Ironworks, near Falkirk. He states that the largest quantity of oil
obtained was eleven gallons, the specific gravity varying from 0.925
to 1.000, and that the water contained a quantity of ammonia fully
equal to 5½ lb. of sulphate of ammonia to the ton of coal coked. The
residual permanent or non-condensed gases were allowed to issue from
the end of the condenser pipe, and were burnt for light in the
engine-houses, but it was intended to force them into the oven again
above the level of the coke. Owing to the works being closed, nothing
has been done with these ovens for some years. I may mention, by the
way, that it is proposed to apply the principle of Mr. Jameson's
process to the recovery of oil and ammonia from the smouldering waste
heaps at the pit-bank, by the introduction into these of conduits
resembling those which he applies to the bottom of the beehive oven.
There is every reason to expect that one or more of these various
methods of utilizing valuable products which are at present lost will
be carried to perfection, and will tend to cheapen the cost at which
iron can be produced, and still further to increase its consumption
for all the multifarious purposes to which it is applied.