Improvements in the Manufacture of Cement and in Apparatus therefor.
Year: 1898

page_text: Reprinted as amended in accordance with the decision of the Chief Examiner
dated the 20th day of September 1900.
Date of Application, 21st Dec., 109O
Complete Specification Left, 29th July, 1899-Accepted, 7th Oct., 1899
Improvements in the Manufacture of Cement and in Apparatus
therefor.
I, CARL FRANZ ANTON EDUARD HUBERTUS VON FORELL, of Giessen, Germany,
Director of Works, do hereby declare the nature of this invention to be as
follows:
-
a
This invention relates to the manufacture of Portland cement from materials
containing lime and clay, and has for object, whilst avoiding special grinding
operations and the loss in time and money consequent thereon, to effect an
intimate comminution and, above all, a perfectly intimate and uniform mixture
of the materials in the furnace itself by burning the clay or clay-slate by
heating it to suitable temperature and altering its structure by
the removal of the water that is chemically combined with it, in
such a manner that the slate, which is extremely hard in its natural state,
can be easily crushed or comminuted, and so that, further, the silicic acid con-
tained therein will be set free or rendered accessible and enabled to combine
readily with the lime in the subsequent fusing process. Moreover, not only
is the lime dried-i.e., freed from the moisture that is mechanically combined
with it in this burning process and without losing any considerable amount of
carbonic acid but, above all, there is produced a molecular decomposition or
breaking down of the mass.
In the processes for the manufacture of Portland cement heretofore ordinarily
employed, either bricks have been made from hydrate of lime and unburned
clay, and then burned and the clinker bricks thus formed have been ground
and sold as Portland cement, or the raw materials have. in their natural state.
been dried, ground, and then made into bricks, which have then been burned
to a clinkering temperature and subsequently ground.
The first mentioned mode of manufacture was soon abandoned, on account of
its expense, whilst the secondly mentioned method entails many considerable
difficulties in the manufacture. When the raw materials are limestone and
clay, the comminution of the former is very difficult, and it must be dried, as
also must the clay. But if the raw material is chalk or Wiesenkalk (hereinafter
called meadow-lime) the mass must be washed, and then again dried, which
entails a great loss of time and money in connexion with the large quantity
of water employed. Furthermore, the lime, in the form of marl, meadow-lime,
or chalk, contains many impurities which render it ununiform and injuriously
affect the quality of the cement, whilst the impurities in the clay have an
injurious effect upon the colour of the cement.

page_text: Now, according to this invention all these drawbacks and defects are obviated
and the whole process of manufacture is simplified by the fact that the clay
or slate, and also the limestone, chalk, meadow-lime, or marl, are calcined
directly at a red heat, if necessary, after washing, and prior to the manufacture
proper, in their natural condition--that is to say, without previous grinding.
In this manner the clay-slate, as also the hard limestone, loses its structure,
and experiences a loosening of its structure in a manner similar to that which
takes place in the bursting of rocks produced by great cold in consequence of
the expansion of the moisture that has penetrated between the molecules of
the rock. The silicic acid of the clay is set free or rendered accessible or
operative, whilst, in addition, the lime, without losing any appreciable part of
its carbonic acid, experiences an alteration in its structure, which destroys the
molecular cohesion and thus considerably facilitates its comminution. The
water of hydration is removed from the chalk, marl, or meadow-lime by the
calcination, and any organic substances that are present are burned, so that this
also promotes loosening of the structure of the rock and facilitates its comminu-
tion.
By the fact that the lime loses none, or only an inappreciable part, of its
carbonic acid, all annoyance through the dust of the burnt lime is avoided.
The fact that the burning process does actually produce a considerable altera-
tion, especially in the clayey material (clay-slate) is best shown by the fact
that in treating burnt clay-slate with hydrochloric acid, a considerably higher
percentage of materials is dissolved than in the similar treatment of the finely
ground natural clay-slate with hydrochloric acid, which, in combination with
the conversion of the contained protoxide of iron into oxide of iron during the
process of burning, and the absorption of oxygen from the air, is a proof that
the silicic acid has actually been rendered accessible or operative or set free.
The essential feature of the present process consists in the fact that the raw
materials are subjected to a loosening of their structure in the natural state,
by being heated to a bright red heat, which loosening considerably promotes
their comminution, and thereby effects an economy in time and money.
carrying out the process described, there is employed a furnace which con-
sists of two or more separate parts, and is arranged to rotate in an inclined
position.
For
This furnace is fired in a suitable manner, at its lower end, and is traversed
along its entire length by the heating gases, whilst the raw material, which is
introduced at the higher end. passes through the furnace in the opposite
direction, and leaves it as a finished product at its lowest point. According
as the furnace is divided into two or more parts, the process of working that
is effected therein, is also divided into two, three, or more successive steps.
Thus, for example, in a furnace divided into three parts, the process may be
divided into a preliminary drying process, a caleining or roasting process, and
a fusing or burning process. These three processes, which are quite different
from one another, take place in totally different periods of time, and therefore
the several parts of the furnace must rotate with different speeds, so that it
is inconceivable that they should be combined or take place in one single part
of the furnace, regard being had to the efficiency of the furnace and to technical
difficulties, and also to the good quality of the finished product. It is, however,
possible to work economically with a combination of the preliminary drying
process and the calcining process in one part of the furnace which rotates at
a suitable speed, but the fusing process must take place in a special part of the
furnace which rotates slowly. A furnace of this kind comprises two parts B
and C. three examples of which are shown in the accompanying drawings.
In the example represented in Fig. 1 in longitudinal section, and in Figs. 2
and 3 in vertical cross section, the two parts B and C of the furnace, which
rotate with different speeds around one and the same axis, are connected directly
to each other.

page_text: Fig. 4 is a longitudinal section of a furnace in which one of the parts is
arranged above the other.
Fig. 5 is a longitudinal section and Fig. 6 a vertical cross section of another
example in which the two parts of the furnace are situated in line with each
other and are separated from each other.
The two parts of the furnace are most simply made of wrought iron casings b
and respectively, with inner linings b and c respectively, of ganister or other
refractory material. Externally, the parts of the furnace are provided with.
bearing rings 1. by means of which they run upon suitable roller bearings r
(Fig. 2). The two parts B and C are driven separately by means of suitable
devices E and F, which are shown in the drawings as a worm and worm-wheel
by way of example-in this case, the wheel is formed by a worm-wheel rim
which surrounds the part of the furnace and in which there engages a worm
which is driven in any suitable manner.
In order to render the velocities of rotation of the several parts independent
of each other, and to enable them to be regulated at will, it is advisable to
provide a separate driving device for each part of the furnace. Experiments
have shown that, as a rule, the part C must rotate twice as fast as the part B.
The latter rotates with its lower end in a sleeve-like extension of the front
portion A. This latter is made of refractory material and serves for burning
the pulverulent or gaseous fuel, which is introduced by means of a blower.
The upper end of the part B rotates either in a sleeve C2 of the part C (Fig. 1)
or in masonry M (Figs. 4, 5, and 6). The upper end of the part C rotates in
a corresponding aperture in the chimney D, whilst its lower end rotates, in
the examples shown in Figs. 4, 5, and 6, in a corresponding aperture in the
masonry M. From the outside and through the masonry there is carried a
charging-shoot G, which leads into the upper part of C.
The vacant space d, which remains in the chimney below the charging shoot,
serves as a dust-catcher in which any fine dust that may be carried in by the
escaping fire gases will collect.
The mode of operation of the furnace herein described and shown in Figs. 1, 2,
and 3, is as follows:-
The raw material such as lime, chalk, clay, and the like, which is introduced
in a wet state through the charging shoot into the furnace part C, is dried
during the rotation, intimately mixed and comminuted, and passes in a red-hot
state into the furnace-part B, in which the fusing process takes place, in the
most perfect manner, at a slow speed of rotation.
During this operation, the heating gases that escape from the front portion A
pass through the whole furnace into the chimney in a direction opposite to
that of the movement of the raw materials. The heating gases, on entering
the chimney, first come into contact with the wet raw material, which is con-
tinually charged in through the charging shoot, and they give up, for the greater
part, any dust particles which they may have carried in with them, to the said
wet raw material. In consequence of the more rapid rotation of the furnace-
part C, a rapid evaporation of the water contained in the raw material takes
place, whilst the high temperature of, say, 1000° which obtains in this part,
produces an intense calcination of the raw materials.
The chemical alteration thus produced in the mixture is sufficient, in most
cases, to produce at once a commencement of the burning process proper, so
that no loss of heat results therefrom.
Where space is limited, it is preferable to employ the arrangement shown
in Fig. 4, in which one of the two furnace-parts is arranged above the other.
In this case, the raw material that is introduced by the charging shoot G,
traverses, first, the more rapidly rotating furnace-part Cand, on leaving the
same, falls upon a second charging shoot H, which conveys it at once into the
furnace part B. The heating gases that pass upward from the latter, pass
through the brick flue directly into the upper part C, and thence to the

page_text: chimney D. In other respects, the mode of operation is in this case exactly
the same as with the arrangement shown in Fig. 1.
As, in consequence of the different natures of the raw materials to be treated,
it may happen that with the more rapidly operating preliminary drying and
roasting processes, a greater quantity of raw materials will pass into the furnace-
part B than the latter is capable of treating, it will be advisable, in cer-
tain cases, to draw off a part of the roasted raw materials from the furnace-part C.
This can be done, in the example shown in Figs. 5 and 6, through the passage K.
In the example shown in Fig. 4, this object could be effected in the most simple
manner if there were provided an additional charging shoot J, which is indicated
in the drawing in dotted lines.
In Figs. 5 and 6 there is further indicated an inlet #, which, like the charging
shoot H (Fig. 4), enable's the furnace part B to be employed for burning raw
material which has undergone a preliminary treatment according to the method
heretofore employed. In this case, the furnace-part would nave to be thrown
out of operation and would only serve to convey the heating gases to the
chimney. In the treatment of very hard rock or stone, the arrangements indicated
in Figs. 4 and 5 of the herein-described furnace, would allow of the interpola-
tion of a grinding process, effected outside the oven, before the burning process
proper in the furnace-part B, so that these arrangements will render the
herein-described furnace capable of the most extended use.
Instead of arranging the part C above the part B as shown in Fig. 4, the two
parts may be arranged side by side and provided with a suitable connexion.
Dated this 21st day of December 1898
F. WISE HOWORTH,
46, Lincoln's Inn Fields, London, W.C.,
Agent for the Applicant.
Improvements in the Manufacture of Cement and in Apparatus
therefor.
I, CARL FRANZ ANTON EDUARD HUBERTUS VON FORELL, of Giessen, Germany,
Director of Works, 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:-
This invention relates to the manufacture of Portland cement from materials
containing lime and clay, and has for object, whilst avoiding special grinding
operations and the loss in time and money consequent thereon, to effect an
intimate comminution, and, above all, a perfectly intimate and uniform mixture
of the materials in the furnace itself, by burning the clay or clay-slate by
heating it to a suitable temperature and altering its structure by
the removal of the water that is chemically combined with it, in
such a manner that the slate, which is extremely hard in its natural state,
can be easily crushed or comminuted, and so that, further, the silicic acid con-
tained therein is fluxed and enabled to combine readily with the lime in the
subsequent fusing process. Moreover, not only is the lime dried-i.e., freed
from the moisture that is mechanically combined with it-in this burning
process and with the loss of almost all its carbonic acid, but, above all, there
is produced a molecular decomposition or breaking down of the mass.
In the processes for the manufacture of Portland cement heretofore ordinarily
employed, either bricks have been made from hydrate of lime and unburned

page_text: clay, and then burned, and the clinker bricks thus formed have been ground
and sold as Portland cement, or the raw materials have, in their natural state,
been dried, ground, and then made into bricks, which have then been burned
to a clinkering temperature and subsequently ground.
The first mentioned mode of manufacture was soon abandoned on account of
its expense, whilst the secondly mentioned method entails many considerable
difficulties in the manufacture. When the raw materials are limestone and
clay, the comminution of the former is very difficult, and it must be dried, as
also must the clay. But if the raw material is chalk, the mass must be washed,
and then again dried, which entails a great expenditure of time and money in
consequence of the large quantity of water present. Furthermore, the lime,
in the form of marl or chalk, contains many impurities, which render it
ununiform and injuriously affect the quality of the cement, whilst the impurities
of the clay have an injurious effect upon the colour of the cement.
Now, according to this invention all these drawbacks and difficulties are
obviated, and the whole process of manufacture is simplified by the fact that
the clay or slate, and also the limestone, chalk, or marl, are, if necessary after
washing, and as the first stage in the manufacture proper, calcined at a red
heat in their natural condition-that is to say, without previous grinding.
In this manner the clay-slate, as also the hard limestone, loses its structure,
and experiences a loosening of its structure similar to that which takes place
in the bursting of rocks produced by great cold, in consequence of the expansion
of the moisture that has penetrated between the molecules of the rocks. The
silicic acid of the clay is fluxed, whilst, in addition, the lime, with loss of
almost all its carbonic acid, experiences an alteration in its structure which
destroys the molecular cohesion and thus considerably facilitates its comminution.
The water of hydration is removed from the chalk or marl by the calcination
and any organic substances that are present are burned, so that this also
promotes loosening of the structure of the rock and facilitates its comminution.
By the fact that the lime loses almost all its carbonic acid, all annoyance
through the dust of the burnt lime is avoided.
The fact that the burning process does actually produce a considerable altera-
tion, especially in the clayey material (clay-slate) is best shown by the fact that
in treating burnt clay-slate with hydrochloric acid, a considerably higher per-
centage of materials is dissolved than in the similar treatment of the finely
ground natural clay-slate with hydrochloric acid, which, in combination with
the conversion of the contained protoxide of iron into oxide of iron during the
process of burning, and the absorption of oxygen from the air, is a proof that
the silicic acid has actually been fluxed.
The essential feature of the present process consists in the fact that the raw
materials are subjected to a loosening of their structure in the natural state,
by being heated to a bright red heat, which loosening considerably promotes
their comminution, and thereby effects an economy in time and money.
For carrying out the process described, there is employed a furnace which con-
sists of two or more separate parts, and is arranged to rotate in an inclined
position.
This furnace is fired in a suitable manner, at its lower end, and is traversed
along its entire length by the heating gases, whilst the raw material, which is .
introduced at the higher end, passes through the furnace in the opposite
direction, and leaves it as a finished product at its lowest point. According
as the furnace is divided into two or more parts, the process of working that
is effected therein, is also divided into two, three, or more successive steps.
Thus, for example, in a furnace divided into three parts, the process may be
divided into a preliminary drying process, a calcining or roasting process, and
a fusing or burning process. These three processes, which are quite different
from one another, take place in totally different periods of time, and therefore
the several parts of the furnace must rotate with different speeds so that it

page_text: is inconceivable that they should be combined or take place in one single part
of the furnace, regard being had to the efficiency of the furnace and to technical
difficulties, and also to the good quality of the finished product. It is, however,
possible to work economically with a combination of the preliminary drying
process and the calcining process in one part of the furnace which rotates at
a suitable speed, but the fusing process must take place in a special part of the
furnace which rotates slowly.
Three examples of furnaces of this kind, each comprising two parts B and C,
are shown in the drawings filed with my Provisional Specification.
In the example represented in Fig. 1 in longitudinal section, and in Figs. 2
and 3 in vertical cross section, the two parts B and C of the furnace, which
rotate with different speeds around one and the same axis, are connected directly
to each other.
Fig. 4 is a longitudinal section of a furnace in which one of the parts is
arranged above the other.
Fig. 5 is a longitudinal section and Fig. 6 a vertical cross section of a furnace
in which the two parts of the furnace are situated in line with each other and
are separated from each other.
The two parts B and C of the furnace are most simply made of wrought iron
casings and respectively, with inner linings and respectively, of suitable
refractory material, as ganister. Externally, the parts B and C are provided
with bearing rings, by means of which they run upon suitable roller bearings
(Fig. 2). The two parts B and C are driven separately by means of suitable
devices E and F, each of which is shown in the drawings as a worm and worm-
wheel by way of example-in this case, the wheel is formed by a worm wheel
rim which surrounds the corresponding part of the furnace and in which there
engages a worm which is driven in any suitable manner.
In order to render the velocities of rotation of the several parts independent
of one another, and to enable these velocities to be regulated at will, it is
advisable to provide a separate driving device for each part of the furnace.
Experiments have shown that, as a rule, the part C must rotate twice as fast
as the part B. The latter rotates with its lower end in a sleeve-like extension
of the front portion A. This latter is made of refractory material and serves
for burning the pulverulent or gaseous fuel, which is introduced by means of
a blower.
The upper end of the part B rotates either in a sleeve of the part C (Fig. 1)
or in masonry M (Figs. 4, 5, and 6). The upper end of the part C rotates in
a corresponding aperture in the masonry M. From the outside and through the
masonry there is carried a charging-shoot G, which leads into the upper part
of C.
The vacant space, which remains in the chimney below the charging shoot,
serves as a dust-catcher in which any fine dust that may be carried in by the
escaping fire gases will collect.
The mode of operation of the furnace herein described and shown in Figs. 1, 2,
and 3, is as follows:
The raw material such as lime, chalk, clay, and the like, which is introduced
in a wet state through the charging-shoot G into the furnace part C, is, during
the rotation, dried, intimately mixed, and comminuted, and passes in a red-hot
state into the furnace part B, in which the fusing process takes place, in the
most perfect manner, at a slow speed of rotation.
During this operation, the heating gases that escape from the front portion A
pass through the whole furnace into the chimney in a direction opposite to
that of the movement of the raw materials. The heating gases, on entering
the chimney, first come into contact with the wet raw material, which is con-
tinually charged in through the charging shoot, and they give up, for the greater
part, any dust particles which they may have carried in with them, to the said
wet raw material.

page_text: In consequence of the more rapid rotation of the furnace-part C, a rapid
evaporation of the water contained in the raw material takes place, whilst the
high temperature of, say, 1000° C. which obtains in this part, produces an
intense calcination of the raw materials.
The chemical alteration thus produced in the mixture is sufficient, in most
cases, to produce at once a commencement of the burning process proper, so
that no loss of heat results therefrom.
Where space is limited, it is preferable to employ the arrangement shown
in Fig. 4, in which one of the two furnace parts is arranged above the other.
In this case, the raw material that is introduced by the charging shoot G.
traverses, first, the more rapidly rotating furnace-part and, on leaving the
same, falls upon a second charging shoot H, which conveys it at once into the
furnace part B. The heating gases that pass upward from the latter, pass
through the brick flue O directly into the upper part C, and thence to the
chimney D. In other respects, the mode of operation is in this case exactly
the same as with the arrangement shown in Fig. 1.
In consequence of the different natures of the raw materials to be treated.
it may happen that with the more rapidly operating preliminary drying and
roasting processes, a greater quantity of raw materials will pass into the furnace
part B than the latter is capable of treating; it will therefore be advisable, in cer-
tain cases. to draw off a part of the roasted raw materials from the furnace part C.
This can be done, in the example shown in Figs. 5 and 6, through the passage K.
In the example shown in Fig. 4, this object could be effected in the most simple
manner if there were provided an additional charging shoot J, which is indicated
in the drawing in dotted lines.
In Figs. 5 and 6 there is further indicated an inlet n, which. like the charging
shoot H (Fig. 4), enables the furnace part B to be employed for burning raw
material which has undergone a preliminary treatment according to the method
heretofore employed. In this case, the furnace part would have to be thrown
out of operation and would only serve to convey the heating gases to the
chimney. In the treatment of very hard rock or stone, the arrangements indicated
in Figs. 4 and 5 of the herein described furnace, would allow of the interpola-
tion of a grinding process effected outside the oven, before the burning process
proper in the furnace-part B. so that these arrangements will render the
kind of furnaces herein before described capable of the most extended use.
Instead of arranging the part C above the part B as shown in Fig. 4, the two
parts may be arranged side by side and provided with a suitable connexion.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is:-
1. In the manufacture of Portland cement from clayey material and lime,
subjecting the raw materials (clay-slate, clay, limestone, chalk, marl), for the
purpose of loosening their structure and thereby effecting a facilitation of their
comminution, to such a temperature (red heat) that the structure of the lime
is altered and the clayey materials are so altered as regards their structure and
so affected that their silicic acid is enabled to act upon the lime in the subse-
quent fusing process, substantially as described.
2. For carrying out the process according to the preceding claim, a furnace
having two or more separate furnace parts B and C, which rotate at different
speeds, and which are connected to one another in such manner and whose
revolutions can be so regulated that the wet raw material, which is charged
in at one end, will be efficiently mixed, dried, and calcined, will pass in a red
hot state into the burning zone, which is situated near the other end, and will,
after being fused, leave the furnace as a finished burned product, the object
being to avoid loss of heat and the formation of dust as much as possible, and
to reduce the cost of working to a minimum.

page_text: 3. A furnace according-to-Claim-2,-in-which-two-rotating furance-parts-Band C
are either-connected-together directly-one-behind-the-other-(Fig. 1)-or-ure sepuruted
from each other by-a-suitable-interval-of space-(Fig.-á).
4. A-furnace according to Claim-2,-in-which-two rotating furnace parts-B and C
are arranged one-above the other-(Fig. 4)-or-side-by-side.
5. Furunces according-to-Claims-3-and-4-in-which there is arranged-between-the
two rotating furnace-parts-B-and Ca-device-(1-or K respectively Fig. 4-und Fige.
and-6)-for-discharging-the-enleined raw-material-from-the furnace-part C, or a device
(Hand-n-respectively)-for charging-suitably prepared raw-material into-the-furnace
part-B.
3. 6. Apparatus for the manufacture of cement constructed, arranged, and
operating as hereinbefore described with reference to and shown in Figs. 1, 2,
and 3, Fig. 4, or Figs. 5 and 6, of the drawings filed with my Provisional
Specification.
3011
2 T... 1000
F. WISE HOWORTH,
46, Lincoln's Inn Fields, London, W.C.,
Agent for the Applicant.