IMPROVEMENTS IN THE MANUFACTURE OF PORTLAND CEMENT
Year: 1884

page_text: :
I JOHN HENRY JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex,
Gentleman do hereby declare the nature of said Invention for "IMPROVEMENTS
IN THE MANUFACTURE OF PORTLAND CEMENT" to be as follows:-
The ordinary processes heretofore employed of making Portland Cement from
hydraulic lime stones cement rocks.clays chalks and the like involve considerable
labour and expense and consume much time. It is necessary to wait for the
drying of the Cement pastes after they are made before calcining them and the
calcining operation itself is tedious. and requires to be conducted with great care
the purpose of this operation being not only the clinkering or semi-vitrifying of
the cement paste but the expulsion both of the Carbonic acid gas and water found
in the raw material and of the water put with the cement powder in order to form
it into paste which to a considerable extent remains in the paste as it is put in the
kiln. Moreover in the calcining operation a large portion of the Cement paste is
wasted by under burning or overburning this being due to the impediment in the
draught and the choking up of the kiln produced by the compactness of straight
surfaced materials and the running together of the adjacent square or flat pieces or
blocks into which the cement paste is usually formed before being placed in the
kiln.
"
i
The length of time required for calcining depends largely upon the amount of
water or moisture in the cement paste and with a view among other things to
reduce this amount as well as to remove the carbonic acid gas, the plan has been
adopted of first calcining the raw stone by slow heat and then grinding it, forming
it into cement paste and recalcining the same to a clinker. This process gets rid of
the moisture and carbonic acid gas contained in the raw material but does not
obviate the necessity for the mixing of the usual amount of water with the cement
powder in order to make the same into paste.
1.
For the purpose of obviating the necessity of waiting for the paste to dry and of
saving the labour and expense usually attending the treatment and handling of
D

page_text: the paste after it leaves the pug mill and before it is put into the kiln the plan has
been adopted of mixing with the paste a liquid combustible whereby the cement
paste can be put into the kiln and subjected to calcination while wet or damp.
These processes get rid of the Gas and water in the raw Stone or material before
it is ground into powder and the latter permits the paste to be subjected to
calcining heat while still wet but neither of them removes the necessity for the
employment of water in considerable quantity mixed with the cement powder for
the purpose of bringing the latter to the condition of paste which can be formed
into proper shapes.
This Invention has for its object to enable cement powder to be moulded into
forms or shapes suitable for the kiln, as respects size, adaptability to free draught
and the like while dispensing nearly if not altogether, with the water ordinarily
required to bring it to the pasty condition for this purpose.
In other words it is proposed to fit for calcination, balls or lumps of dampened
cement powder, mechanically compressed by force instead of masses of wet cement
paste cut or moulded according to methods heretofore used. Under the process
according to this Invention the amount of water necessary is reduced from 35 to 40
per cent by weight (the amount heretofore required) to about six to ten per cent by
weight where ground raw stones or cement making materials are used and to about
15 to 25 per cent by weight where calcined cement making powder is similarly
used.
The Inventors have discovered that the object they have in view can be
accomplished by compressing the cement making powder while simply dampened
but not in a pasty condition by heavy pressure between rollers whose surfaces are
indented with cells wherein the dampened powder may under pressure be moulded
into forms suitable to be placed into the kiln.
One way of carrying this Invention into practice is to take raw cement-rocks
such as are used for making portland cement and after grinding them into powder
in the ordinary way between millstones run the powdered mass into a mixer of any
approved form wherein there are added to the powder about three per cent by
weight of coal tar or other liquid combustible and only about eight per cent, by
weight of water The powder is well stirred and while in this pulverulent
condition is fed in between rolls having upon their faces egg shaped, hexagonal
circular or other formed cavities or cells wherein the dampened powder is compressed
into balls or lumps most suitable for the calcining operation. These balls or lumps
may then be conveyed upon an endless belt or by any other suitable device to a
kiln where they are calcined and thence removed to mills where they are ground
into finished cement.
Another way of performing this Invention is to take limestone and clay or chalk
and clay as commonly used in the manufacture of portland cement and to dry the
same and grind them together in mills. The powder thus obtained is conveyed to
a mixing or stirring machine of any suitable design. To the powder about 12 per
cent (by weight) of water is added. The dampened powder thus obtained is fed
between rotating surfaces of the character hereinbefore described and the balls or
lumps obtained by the moulding operation are conveyed to kilns and then ground
into finished cement.
:
The Inventors have also made Portland Cement by taking natural cement rocks
containing the proper cement elements calcining them with about the same degree
of heat usually required to make the ordinary natural cement known in the trade
and then grinding the material thus obtained to a powder This powder is then
run into a mixing or stirring machine of any suitable design and about twenty per
cent (by weight) of water, and four per cent of any liquid combustible. are then
stirred into it (together with about one per cent by weight of coke "breeze") The
dampened powder thus obtained is then fed between rotating surfaces or rolls into
the faces of which are sunk egg-shaped, hexagonal circular or other shaped cavities
or cells wherein the material is compressed and moulded into balls, or lumps most
suitable for burning in the kiln. They are then conveyed by an endless belt or
-

page_text: any other suitable device to kilns where they are calcined and afterwards ground
into finished cement in the usual way.
The Invention is not however, limited to these applications which are merely
adduced by way of illustration of how it may be used. In every case however
there should be employed the main features of the process namely simply dampening
the pulverulent cement making material so that it shall remain essentially powder
as contradistinguished from paste and then forming this dampened powder into
balls or lumps by heavy pressure between rotating surfaces.
This Invention possesses many advantages over the systems now in use for
making portland cement and for preparing the cement making composition for the
same.
First. By it a minimum of water is required; in most cases when the raw
materials are used, only about one fourth of the water heretofore used is required,
thus effecting a great saving in the fuel necessary for the drying and calcining of
the paste in the ordinary process and further more ensuring a quicker and more
economical burning in the kilns since a considerable portion of such minimum of
water is pressed from the balls or lumps by pressure to which they are subjected in
passing between the rolls and is further evaporated during the passage of the balls
or lumps from the rolls to the kilns.
Second The oviform globular or hexagonal balls or lumps into which the cement-
making powder is preferably moulded cannot be successfully and regularly produced
in any other way than by heavy pressure and they possess by reason of their
small size and shape advantages over the square flat sided pieces or slabs into
which cement pastes have hitherto been formed since they adinit of a free
circulation of air during the calcining operation do not clog the draught have no
corners to chip off and "dust" away admit of a freer and more perfect burning
than is attainable under the older methods and furthermore are easier to crush and
grind than the large pieces made under the older methods.
Third. The balls or lumps being all moulded by a uniform pressure possess a
uniformity of porosity. and density and dampness and consequently a more uniform
manufactured product can be obtained.
Fourth. The settling tanks or "backs" and drying floors required under the
older methods can be dispensed with owing to the fact that by this Invention the
cement lumps in desirable forms can be delivered directly from the moulding
machine to the kilns by endless belts or other similar devices without any
handling whereby a large saving is effected in the cost of manufacture while the
great capacity. of rolls over other designs of compressing machines enables larger
amounts of the cement lumps or balls to be economically prepared for the calcining
operation.
Dated this 92nd day of Tenuary 1884

page_text: I JOHN HENRY JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex
IMPROVEMENTS IN
Gentleman do hereby declare the nature of said Invention for
"
THE MANUFACTURE OF PORTLAND CEMENT" and in what manner the same is to
be performed to be particularly described and ascertained in and by the following
statement:-
The ordinary processes heretofore employed for making Portland Cement from
hydraulic lime stones, cement rocks, clays, chalks and the like, involve considerable
labour and expense and consume much time. It is necessary to wait for the
drying of the cement pastes after they are made before calcining them, and the
calcining operation itself is tedious and requires to be conducted with great care,
the purpose of this operation being not only the clinkering or semi-vitrifying of
the cement paste but the expulsion both of the carbonic acid gas and water found
in the raw material, and of the water put with the cement powder in order to form
it into paste, which, to a considerable extent, remains in the paste as it is put in
the kiln. Moreover in the calcining operation a large portion of the cement paste
is wasted by under-burning or over-burning-this being due to the impediment in
the draught and the choking up of the kiln produced by the compactness of
straight surfaced materials, and the running together of the adjacent square or flat
pieces or blocks into which the cement paste is usually formed before being placed
in the kiln.
The length of time required for calcining depends largely upon the amount of
water or moisture in the cement paste and with a view among other things to
reduce this amount as well as to remove the carbonic acid gas, the plan has been
adopted of first calcining the raw stone by slow heat and then grinding it, forming
it into cement paste and re-calcining the same to a clinker. This process gets rid
of the moisture and carbonic acid gas contained in the raw material, but does not
obviate the necessity for the mixing of the usual amount of water with the cement
powder in order to make the same into paste.
For the purpose of obviating the necessity of waiting for the paste to dry, and of
saving the labor and expense usually attending the treatment and handling of the
paste after it leaves the pug-mill and before it is put into the kiln, the plan has
been adopted of mixing with the paste a liquid combustible whereby the cement
paste can be put into the kiln and subjected to calcination while wet or damp.
These processes get rid of the Gas and water in the raw stone or material before
it is ground into powder and the latter permits the paste to be subjected to
calcining heat while still wet; but neither of them removes the necessity for the
employment of water in considerable quantity mixed with the cement powder for
the purpose of bringing the latter to the condition of paste which can be formed
into proper shapes.
This Invention has for its object to enable cement powder to be moulded into
forms or shapes suitable for the kilns, as respects size, adaptability to free draught
and the like, while dispensing nearly if not altogether with the water ordinarily
required to bring it to the pasty condition for this purpose.
In other words it is proposed to fit for calcination balls or lumps of dampened
cement powder mechanically compressed by force, instead of masses of wet cement
paste cut or moulded according to methods heretofore used. Under the process
according to this Invention the amount of water necessary is reduced from 35 to 40.
per cent by weight, (the amount heretofore required) to about six to ten per cent
by weight where ground raw stones or cement making materials are used; and to
about 15 to 25 per cent by weight where calcined cement making powder is
similarly used.

page_text: The Inventors bave discovered that the object they have in view can be
accomplished by compressing the cement making powder while simply dampened
but not in a pasty condition by beavy pressure between rollers whose surfaces are
indented with cells wherein the dampened powder may under pressure be moulded
into forms suitable to be placed into the kiln.
One way of carrying this. Invention into practice is to take raw cement-rocks
such as are used for making Portland Cement, and, after grinding them into powder
in the ordinary way between millstones, run the powdered mass into a mixer of
any approved form wherein there are added to the powder about three per cent by
weight of coal tar or other liquid combustible and only about eight per cent, by
weight of water. The powder is well stirred and while in this pulverulent
condition is fed in between rolls, having upon their faces, egg-shaped, hexagonal,
circular, or other formed, cavities or cells wherein the dampened powder is
compressed into balls or lumps most suitable for the calcining operation. These
balls or lumps may then be conveyed upon an endless belt; or by any other
suitable device, to a kiln where they are calcined and thence removed to mills
where they are ground into finished cement.
Another way of performing this Invention is to take lime-stone and clay, or
chalk and clay as commonly used in the manufacture of Portland Cement, and to
dry the same and grind them together in mills. The powder thus obtained is
conveyed to a mixing or stirring machine of any suitable design. To the powder
about 12 per cent by weight of water is added. The dampened powder thus
obtained is fed between rotating surfaces of the character herein before described
and the balls or lumps obtained by the moulding operation are conveyed to kilns
and then ground into finished cement.
The Inventors have also made portland cement by taking natural cement-rocks
containing the proper cement elements, calcining them with about the same degree
of heat usually required to make the ordinary natural cement known in the trade;
and then grinding the material thus obtained to a powder. This powder is then
run into a mixing or stirring machine of any suitable design and about twenty per
cent by weight of water and four per cent of any liquid combustible are then
stirred into it (together with about one per cent by weight of coke "breeze").
The dampened powder thus obtained is then fed between rotating surfaces or rolls
into the faces of which are sunk egg-shaped, hexagonal, circular or other shaped
cavities or cells, wherein the material is compressed and moulded into balls or
lumps most suitable for burning in the kiln. They are then conveyed by an
endless belt, or any other suitable device, to kilns where they are calcined and
afterwards ground into finished cement in the usual way.
The Invention is not however limited to these applications which are merely
adduced by way of illustration of how it may be used. In every case however
there should be employed the main features of the process namely; simply
dampening the pulverulent cement making material so that it shall remain
essentially powder as contradistinguished from paste and then forming this
dampened powder into balls or lumps by heavy pressure between rotating surfaces.
This Invention possesses many advantages over the systems now in use for
making Portland Cement and for preparing the Cement-making composition for
the same.
-
First By it a minimum of water is required; in most cases when the raw
materials are used only about one fourth of the water heretofore used is required
thus effecting a great saving in the fuel necessary for the drying and calcining of
the paste in the ordinary process; and furthermore ensuring a quicker and more
economical burning in the kilns since a considerable portion of such minimum of
water is pressed from the balls or lumps by pressure to which they are subjected in
passing between the rolls and is further evaporated during the passage of the balls
or lumps from the rolls to the kilns.
Second-The oviform, globular or hexagonal balls or lumps into which the
cement making powder is preferably moulded cannot be successfully and regularly

page_text: :
produced in any other way than by heavy pressure and they possess by reason of
their small size and shape advantages over the square flat-sided pieces or slabs
into which cement pastes have hitherto been formed since they admit of a free
circulation of air during the calcining operation, do not clog the draught, have no
corners to chip off, and "dust" away, admit of a free and more perfect burning
than is attainable under the older methods; and furthermore are easier to crush
and grind than the large pieces made under the older methods.
Third The balls or lumps being all moulded by a uniform pressure possess a
uniformity of porosity and density and dampness and consequently a more uniform
manufactured product can be obtained.
Fourth-The settling tanks or "backs" and drying floors required under the
older methods, can be dispensed with owing to the fact that by this Invention the
cement lumps in desirable forms can be delivered directly from the moulding
machine to the kilns by endless belts or other similar devices without any handling
whereby a large saving is effected in the cost of manufacture while the great
capacity of rolls over other designs of compressing machines enables larger amounts
of the cement lumps or balls to be economically prepared for the calcining
operation.
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:
First The hereinbefore described improvement in the art of manufacturing
Portland Cement consisting in only dampening the pulverulent cement-making
material or materials so that it or they shall still remain essentially powder as
contradistinguished from paste and then moulding the said dampened powder into
balls or lumps by heavy pressure between rotating surfaces substantially as and for
the purposes herein before set forth.
Second-The process of manufacturing Portland Cement consisting in reducing
the cement making material or materials to powdered condition dampening the
same to such an extent only that it or they shall remain essentially powder as
contradistinguished from paste, moulding said dampened powder into balls or
lumps by heavy pressure and subsequently calcining the said balls or lumps and
reducing them to powder substantially as and for the purposes hereinbefore set
forth.
Third The process of manufacturing Portland Cement which consists in
dampening the previously powdered cement making material or materials with
water and a liquid combustible to such an extent only that it or they shall remain
essentially powder as contradistinguished from paste, moulding the said dampened
powder into balls or other suitable shapes by heavy pressure, and subsequently
calcining and reducing the same to powder substantially as hereinbefore set forth.
Dated this 13th day of October 1884.