IMPROVEMENTS IN THE MANUFACTURE OF COKE FOR METALLURGICAL PURPOSES
Year: 1886

page_text: .
HUGH BARCLAY, Metallurgical Chemist and ROBERT SIMPSON Metallurgist both
of Harrington Iron Works, Cumberland do hereby declare the nature of our
invention for." IMPROVEMENTS IN THE MANUFACTURE OF COKE FOR METALLURGICAL
PURPOSES" to be as follows:-
In the ordinary method of manufacturing coke for the blast furnace or other
metallurgic process it is often found that coke is produced which is weak and
friable;
and so open and porous that it is easily attacked by carbonic acid gas in
the upper parts of the blast furnace.
The object of this invention is to remedy these evil results. This we effect by
adding to the coal before coking a proportion of lime which we prefer to add in
the condition of hydrate of lime (slaked lime) but caustic lime may also be used
for the same purpose.
We find it preferable to have the coal finely crushed before coking, and to add
the lime before or during the crushing process.
We find that from 4 to 5 per cent of lime added to the coal gives the best
results; but the proportion of lime can be increased or diminished according to
the nature of the coal and the degree of density and hardness required in the
resulting coke. The lime is best added in a pulverent condition, and perfect
admixture must be ensured.
The lime has a strong binding effect and the resulting coke is hard and dense;
and so close and compact in structure, that it reduces to a minimum the solvent
action of carbonic acid.
We find that the lime being so intimately mixed with the coke neutralizes the
evil influence of silica and sulphur, and better grades of iron are produced when
working with this fuel, than with ordinary open grained coke.
Many classes of coal usually considered ill-adapted for metallurgical purposes on
account of sulphur and other impurities and blemishes; are by our process
converted into strong hard cokes suitable for use in the blast furnace.

page_text: We, HUGH BARCLAY, Metallurgical Chemist, and ROBERT SIMPSON, Iron Works
Manager, both of Harrington Iron Works, Cumberland do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:
"
'
Our Invention relates to improvements in the manufacture of coke for
metallurgical purposes and is specially adapted for use in blast furnaces for
smelting or reducing iron ores.
In the ordinary method of manufacturing coke in Bee-hive ovens, it is often
found that the coke produced is weak and unable to withstand much pressure as well
as friable, besides being so open, and porous, or spongy that it is easily attacked by
carbonic acid gas in the upper parts of the blast furnace.
The object of our Invention is to remedy these defects and this we effect by
passing the coal through a Carr's disintegrator or other suitable crushing and
commingling apparatus, adding the proper amount of lime (slaked or caustic lime)
either before or during the process of crushing as distinguished from adding such
lime subsequent to the crushing of the coal; except when the coal is crushed
before being washed in which case the crushed and washed coal is treated with
the lime dust by Carr's 'disintegrator or by other suitable commingling apparatus
for the purpose of effecting the essential intimate admixture thereof.
We find that from 4 to 5 per cent of lime added to the coal gives the best
result; but the proportion of lime may be modified according to the nature of the
coal and the degree of density and hardness required in the resulting coke..
The lime has a powerful binding effect when so mixed with the coal and the
resulting coke is hard and dense, and so compact in structure that it reduces to a
minimum the solvent action of carbonic acid at high temperatures.
We also find that by the lime being so intimately mixed with the coke the
evil influence of silica and sulphur is neutralized and that better grades of iron are
produced than when working with coke not treated with lime.
Many classes of coal usually considered ill-adapted for metallurgical purposes
on account of their bad coking properties, the presence of sulphur and other
impurities, are by our process converted into strong hard cokes specially suitable
for use in the blast furnace: This remark especially applies to the soft or non-
coking coals of Scotland.
By the thorough admixture of lime with the coal as hereinbefore described, the
actual percentage of sulphur in the coke is increased, but we have proved by
prolonged experiments in the laboratory by crucible assays, and by actual trial in
the blast furnace, that, although the sulphur is increased, it is held combined by,
or with the lime, and does not combine with the iron in the smelting process,

page_text: All experiments hitherto made in adding lime to coal coked in bee-hive ovens,
have proved failures by reason of the imperfect mixture of the materials, the lime
being added roughly by hand to the coal at the oven, and also because the sulphur,
being so much increased without a practically equal distribution of lime through-
out the coal, such lime-coke has been unfit for use in the blast furnace.
A serious defect in all previous attempts to use lime in the Bee-hive coking
oven has been the use of very large quantities of lime which gives very bad
results, for example, the excess of lime causes almost all the sulphur of the coal to
be retained, yielding coke with a high percentage of sulphur, such large quantity
of lime also causes the ovens to burn languid by lowering the temperature
producing weak and inferior coke, whilst the waste gases from such ovens are
lowered in their heating power and are useless for steam raising purposes.
1
We have overcome these difficulties by lowering the proportion of lime to
4 or 5°
From the results of working our process we find it advisable not to use any
higher proportion of lime than the aforementioned quantity, and in many cases
that proportion may be lowered with beneficial results.
So long as the hardness and density of the coke are not sacrificed, this lowering
of the proportion of lime is to be recommended because in such case there is not so
large an increase of sulphur in the coke.
As herein before described sulphur when combined with lime in coke does not
deteriorate the iron in the smelting process, but nevertheless large quantities of
sulphur in such coke should be avoided, if possible, solely for the reason, that the
resulting sulphide of calcium has a tendency to make blast furnace slags, more
viscous and difficult to run,
By crushing the coal and adding the lime in the state of fine flour during the
crushing process or afterwards when the coal is crushed before being washed as
herein before described, we secure a thorough and practically perfect commingling
thereof which results in a coke being produced possessing the improved qualities
herein before described, and in a condition that though the sulphur is increased it
is retained or fixed by the lime, so that its injurious influence is neutralized. We
have therefore by our improvements rendered the use of lime-coke practicable on
the industrial scale.
We find as a result of working our Invention, that, when the coking process is
conducted with care so that no undue excess of air is admitted, the use of lime
gives an increased yield of coke, the lime being so intimately mixed with the coal
forms chemical combinations with part of the volatile oils which are thereby fixed
and converted into coke, whilst the surface of the coke in the oven being more
compact, that is to say, less porous than hitherto, is not so easily acted on by the
air and there is consequently less waste.
Some descriptions of coals which do not give good results by our process yield
better cokes, when slightly damped and this damping or wetting is easily effected
by allowing a small stream of water to trickle into the disintegrator.
"
The slaked lime gives the best results, when it is in the condition of fine flour,
and contains about 35 % of water. Instead of limestone other calcareous
substances, such as chalk may be used as the source of lime and likewise some
kinds of slag which contain a large excess of free lime and are free from
impurities may be used either alone or in a conjunction with pure slaked lime.
•
Our process is only applicable to ovens of which the Bee-hive is a type, such
ovens not yielding ammonia or other bye-products, by reason. of all the evolved
gas being consumed inside the oven to maintain the heat necessary for coking.
Having now particularly described and ascertained the nature of our Inven-
tion, and in what manner the same is to be performed we declare that what
we claim is
;
•
The improvements in the manufacture of coke consisting in the intimate
admixture with crushed or pulverized coal of not more than 4 to 5 per cent of

page_text: pulverized lime, the same being mixed together or commingled whilst the
pulverized materials are in a state of rapid motion by being passed through
the machine known as Carr's disintegrator or other equivalent crushing and
commingling apparatus and thereby producing coke having the improved qualities
herein before described.
October 1886.
J. H. JOHNSON, DAY & JOHNSON,
Applicants' Agents,
115, St. Vincent Street, Glasgow,