Improvements relating to the Manufacture of Cement from Schist and Bituminous Marl.
Year: 1894

page_text: Date of Application, 2nd Aug., 1894-Accepted, 30th Mar., 1895
COMPLETE SPECIFICATION.
Improvements relating to the Manufacture of Cement from Schist
and Bituminous Marl.
I, LUDWIG MACK, of 17a Herdweg, Stuttgart, in the Empire of Germany,
Merchant, 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 :—
According to one method or process, the schist and bituminous marl are finely
powdered, after which they are intimately mixed with as much lime or finely ground
or pulverized calcareous marl as is necessary to bring the mixture to the consistency
of Portland cement. This mixture is then formed into balls or bricks by adding
thereto tar or other binding material such as is used in the agglomerated coal
industry (manufacture of briquettes), making use of the same ingredients and
machinery. These balls or bricks, when made and dried, are calcined in a suitable
furnace.
In carrying out this operation, the balls or bricks themselves form the fuel..
Great cconomy is thus effected, not only in the fuel itself but also in its uniform
distribution throughout the furnace, whereby the combustion is caused to be regular
and easily controlled.
The amount of lime to be added to the schist or marl depends upon the
composition of the schist or marl and especially on the amount of lime it contains
naturally. Varieties of schist exist which contain so much lime that they only
require a very small quantity of lime to be added, whilst other schists, which contain
only a small quantity of lime, require the addition of considerable quantities of lime.
For the usual lias schist the amount of lime to be added may be taken at about
30 per cent. In order to determine the exact amount of added lime required in any
particular case, the elementary composition of the schist or marl must be fixed by
analysis, when the amount of additional lime required for the manufacture of the
cement can be calculated.
The amount of tar to be added also depends upon the amount of bitumen
naturally contained in the schist or marl. Thus a larger quantity of tar or the
like should be added to a schist or marl containing a small quantity of bitumen than
to a schist or marl which is rich in bitumen.
For lias schist (or bituminous marl containing similar per centages of lime and
bitumen) the following proportions may be taken as an example :-
Lar
v parts
According to another method or modification of my process for the manufacture
of cement, the reduced bituminous schist or marl is calcined in furnaces which are
arranged in such a manner that the hydrocarbons thus given off can be employed
for other purposes (such, for instance, as for driving machinery for crushing the
cement afterwards obtained, or for operating a blower), and so as to permit the
introduction of chloride of sodium or potassium and water vapour to the incandescent
schist and marl in the furnace.
In the presence of incandescent schist or marl, the chloride of sodium or potassium.
together with the water vapour are dissociated, and, by reason of the interchange
of elements which results, there is formed hydrochloric acid which may be collected,

page_text: marl or schist brings about the formation of cement.
My said process may be advantageously carried out in a shaft-furnace, although
other suitable furnaces may be employed for this purpose if desired. The steam,
which is led into the shaft from below, is reduced by the incandescent carbonaceous
material to hydrogen which combines with the liberated chlorine of the chloride of
sodium to form hydrochloric acid, whilst the sodium oxide formed reacts in statu
nascendi with the clay and combines with the silicic acid and the alumina or
argillaceous earth.
In the case of lias schist (or bituminous marl of similar composition) the following
proportion may be taken as an example:-
Lias schist (or bituminous marl)
Chloride of sodium
-
100 parts
7 parts
In addition to the advantages claimed for the first mentioned process, the latter
process presents the following
1. The excess heating gases given off by the schist and marl constitute a valuable
source of motive power.
2. The commercial value of the hydrochloric acid obtained as a bye-product
considerably exceeds the cost of the common salt or rock salt employed.
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 :-
First. A process for the manufacture of cement from schist or bituminous mari,
in which powdered schist or bituminous marl is intimately mixed with lime or finely
ground or pulverized calcareous marl until it has the consistency of Portland
cement, this mixture being then calcined in suitable furnaces after the addition
thereto of tar or some other ingredient used in the agglomerated coal industry,
and the formation thereof into balls or bricks by machinery such as is used in that
industry, substantially as hereinbefore described.
Second. The modification of my invention, substantially as hereinbefore described,
wherein the calciuation of the marl or schist is effected in furnaces so arranged as
to permit the utilization of the hot gases which are given off by these bituminous
substances, and the introduction thereto of chloride of sodium or potassium and
water vapour, the formation of cement being effected by the dissociation of these
substances introduced to the incandescent schist and marl, whilst there is, at the
same tinie, formed bydrochloric acid and oxide of sodium or potassium which acts
upon the silicic acid from the schist or marl.
Dated this 2nd day of August 1804
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicant.