Year: 1887

page_text: Date of Application, 26th July. 1887
Complete Left, 25th Apr., 1888
Complete Accepted, 25th May, 1888
EDUARD LARSEN Merchant, or 20 Dark Lane London, 1.1. do hereby deciate the
nature of this invention to be as follows:-
The present process of manufacturing Slag Cement consists in granulating or
disintegrating blast furnace Slags as they flow from the furnace, drying them if wet,
and grinding same, and mixing them with ordinary lime, previously slaked to a fine
dry powder.
This necessitates that the slags have in themselves the required chemical properties
and that the treatment takes place at the furnace where room is generally very
limited.
This Invention has for its object different improvements on this process.
I prefer collecting the fluid slags in large removable tanks or resovoirs which will
enable me to take the slags in a fluid state to a more convenient place, than by the
side of the furnace, and there either mix two different fluid slags, add any incerdients
the slags might be difficient of, or eleminate such foreign dangerous matter, that can
be eleminated, and afterwards granulate or disentegrate the slags as required.
Instead of slaking the lime used for mixing with the slags, as now done, in ordinary
water, to a dry powder, I prefer, in accordance with this invention, to slake the lime
in Gypsium water, or a weak solution of sulphuric acid, (rendering it selenitic, after
General Scotts process) before mixing it with the slags or slaking it with steam in a
room heated to such a temperature that no condensation takes place whereby the lime
will bydrate without or with little expansion.

page_text: Instead of using one sort of ordinary pure lime, I prefer using a mixture of pure
lime and so called hydraulic lime, or hydraulic lime alone unslaked, or slaked with
ordinary water or in any of the before mentioned manners.
When the slags are used in the granulated form and consequently wet I prefer
crushing them roughly as part of the water, they contain, will then run off by itself;
and they will then dry much easier.
In this case I also prefer mixing the required quantity of burnt lime with the wet
slags instead of slaking the lime seperately, whereby the water required for the slaking
of the lime will be absorbed from the wet slags.
This and the heat generated by the hydration will effect a saving in the drying.
By mixing with the slags a few per cent. of dry ground clay or some similar
material, or a small per centage of Sulphate of Iron a cement is obtained which is both
improved in closeness, hardness and other qualities which go towards the making up
of a good cement.

page_text: Preparation of Raw Materials Used therefor.
EDUARD LARSEN of 41 Eastcheap London E.C. Merchai erly of 26 Mark
Lane) 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:
My invention has for its object improvements in the manufacture of Slag Cement.
The present process of manufacturing this class of Cement consists in either
granulating in water or disintegrating and suddenly cooling Blast-furnace Slags
directly as they flow from the Furnace, drying them if wet grinding and mixing
them with ordinary lime, previously slaked to a fine dry powder.
necessary
For carrying on the process in this manner the slags must in themselves have the
chemical composition required to produce cement and there must be sufficient
room directly by the furnace for the treatment of the slags. I therefore prefer in instances
where this cannot be conveniently carried out to collect the fluid slags in large
removeable tanks reservoirs or ladles placed on rails which will enable one to remove
the slags in a fluid state to a place more suitable for further or special treatment than
the immediate neighbourhood of the furnace. These tanks or ladles are most con-
veniently constructed from Iron lined with firebricks and covered with a non-conducting
material for instance a coat of slagwool, so that the slags can be kept as hot as possible.
The portable vessels are hung on pivots so that they can be tilted over or are supplied
with an outlet at the bottom.
I then submit the slags to the treatment required for each special case on the spot
where they will be made into cement. This treatment as heretofore consists either in
granulation in water or disintegration and sudden cooling, but besides this I may
mix the slags whilst they are still in a fluid state in the ladles or brought to special
mixing furnaces or reservoirs with such materials preferably if possible also in a fluid
state so that the most perfect admixture can be effected as will render them suitable
or more suitable for producing good cement, for instance Aluminia, Silica or Lime or
one or more of these combined, and if possible brought to fusion before the mixing.
If the slags contain any substance which it might be found desirable to eliminate or
reduce, before the slags are used for cement making for instance a high per centage
of sulphur and these substances can be eliminated or the contents of same be reduced
by an oxydation process, 1 propose treating the still fluid slags, like Iron in a Bessmer
Converter by a current of air preferably highly heated forced through the fluid mass
whereby for instances the sulphur or part of same will be consumed. The slags must

page_text: of course be kept heated and fluid during this treatment to prevent them from solidi-
fying, and to render the following disintegration or granulation possible, and this
must be done in a crucible constructed for the purpose besides the furnace or in
connection with the ladle bringing the slags from the furnace or the ladle itself may
be such a converter.
The lime now used in the manufacture of slag cement is ordinary pure lime from
chalk or lime stone slaked in water and left to fall to a dry fine powder. According
to my invention I have found that by rendering the lime selemitic, that is slaking the
lime in gypsium water or in a weak solution of sulphuric acid or burning it under
access of sulphur vapours after General Scotts process instead of in ordinary water
better results especially in respect of self hardness are obtained.
Similar results can be obtained by mixing sulphuric acid or preferably sulphuric
acid salts for instance Iron Aluminium Zinc or Copper Sulphates in the cement and
of these Iron Sulphate will generally be the cheapest. The best suitable quantity of
admixture varies according to the chemical composition of the materials used for the
cement but from one up to two per cent. will generally be found most effective
and safe.
One way of preparing a suitable mixture for this purpose is by treating Iron ores
as rich as possible in Iron with sulphuric acid and use this mixture dried and pulverized,
or by adding the sulphuric acid or the sulphates in a concentrated solution to the
smallest possible quantity of lime chalk or similar material so as to prepare a stiff
dough which is then dried ground and intimately mixed with the cement in the
required proportions previously ascertained by experiments.
The lime slaked in the ordinary manner to a fine dry powder is in consequence
of the expansion taking place by the hydration exceedingly bulky and light. In
order to obtain a closer hydrated lime powder I prefer slaking the lime by means
of steam brought in contact with the lime in closed reservoirs or tanks kept at
such a temperature that the steam introduced into the interior of these reservoirs
does not condense so that the lime only come in contact with steam but not with
any water. In this manner the lime can become perfectly hydrated, but with less
expansion.
Instead of using ordinary pure or nearly pure white or grey lime for mixing
with the slags prefer in some cases using either a mixture of pure lime and so
called hydraulic lime (lime containing Aluminia and Silica) or a hydraulic lime
alone, and the lime I likewise prefer slaking in one of the manners described
above. The quantity of lime required in such case for making cement will generally
be larger than when pure lime alone is used.
When the slags are used granulated in water, they are generally exceedingly
porous and spongy and consequentl very difficulty and slow to dry.
I have found that by crushing or grinding the slags in their wet state by means
of edge runners rollers or similar machines, and after thus preliminary grinding
allowing as much water as possible to run off before the drying that a great saving
in the drying is effected. A still further saving I obtain by mixing the burnt
lime required for making the slags into cement in the unslaked state but broken
to about walnut size with the wet preferably crushed or ground slags instead of
slaking the lime separately. The lime will chemically bind a certain quantity of
moisture for its hydration and at the same time by the great heat produced will
evaporate another part of the moisture contained in the slags. Care should be
taken of removing any unslaked particles of lime before the mixture is finally
made into cement, which is an easy matter if the slags have been crushed before-
hand. Any moisture still contained in the mixture must of course be evaporated
before the cement can be finished.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what I
claim is.
1. Collecting and bringing the slags in fluid state to a more convenient place than the

page_text: immediate neighbourhood of the Blast furnace for the purpose of making cement
of the slags, and there submitting them to such treatment as is required for
rendering them useful for cement making, as herein described.
2. Admixing and amalgamating with the fluid slags such material or materials
preferably in fluid state as they are deficient of and which will render them more
cementatious, as herein described.
3. Eliminating from the fluid slags such material or materials which it is desirable
to eliminate or reducing the contents thereof before using the slags for cement
making by submitting the still fluid slags to the oxydizing effect of a strong
current of air preferably superheated at the same time keeping the slags sufficiently
hot to remain perfectly fluid, as herein described.
4. Submitting the Lime used in the manufacture of Slag Cement to special
treatment instead of slaking it in ordinary water consisting in either rendering it
silinitic (slaking it in Gypsum water or in a weak solution of sulphuric acid) or
slaking it by steam in closed and heated reservoirs, as herein described.
5. Admixing to the ordinary mixture of lime and slags producing slag cement
a small quantity of sulphuric acid or sulphuric acid salts as Iron Aluminia Zinc
or Copper sulphates preferably previously prepared into a fine dry powder by means
of a small quantity of lime chalk or similar material as herein described.
6. Using instead of ordinary pure white or grey lime hydraulic lime or a mixture
of hydraulic and pure lime preferably slaked by any of the means described herein.
7. Crushing or grinding the granulated wet slags especially when they are very
porous, by means of edge runners rollers or similar machines and allowing as much
of the water as possible to run off before drying the slags, whereby a great economy
in drying is effected as herein described.
8. Mixing the unslaked lime with the bulk or part of the wet slags, preferably
after these are crushed or ground so that the hydration of the lime and the heat
generated thereby will effect a further economy in drying as herein described.
Dated this 25th day of April 1888.
EDUARD LARSEN.