IMPROVEMENTS IN THE MANUFACTURE OF PORTLAND CEMENT
Year: 1854

page_text: LETTERS PATENT to Robert Owen White, of Swanscombe, in the County
of Kent, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE OF
PORTLAND CEMENT."
Sealed the 30th May 1854, and dated the 22nd March 1854.
PROVISIONAL SPECIFICATION left by the said Robert Owen White at
the Office of the Commissioners of Patents, with his Petition, on the
22nd March 1854.
I, ROBERT OWEN WHITE, of Swanscombe, in the County of Kent, do hereby
declare the nature of the Invention for "IMPROVEMENTS IN THE MANUFACTURE
OF PORTLAND CEMENT" to be as follows:-
Heretofore in the manufacture of Portland cement it has been usual to
combine clay and chalk by grinding and washing in water, the matters being
allowed to settle in suitable reservoirs or vats, and when as free as may be
from water, the substance has been dug out in lumps and dried by artificial
means; such lumps have then been burned in kilns by the aid of fuel mixed
with the lumps in the kiln, the charging and burning not being a continuous
process, the kiln, on the contrary, being charged, burned off, and then emptied.
Now my improvements commence with the mixing of the materials, at which
step in the manufacture, in place of grinding the clay and chalk together in
water, and allowing these matters to settle, the chalk is washed alone, and then
mixed with clay by mechanical means; and in order to get the combined
matters into as convenient a form as may be for drying, the mass is caused to
be moulded into forms, preferring that of a brick, and this it is believed can be

page_text: most conveniently performed by forcing the combined matters through moulding
orifices or dies, as when making bricks and tiles, or the moulding may be by
hand; and to facilitate drying, these brick-like forms are hollow. In mixing
the clay and chalk by a pug mill or other mixing machinery a quantity of fuel
is introduced, in order that when burning in the kiln each brick or moulded
quantity of the materials may contain the requisite quantity of fuel, which is
important, not only in consequence of the uniformity of burning which results,
but the charging and drawing may be rendered continuous, and the stopping of
a kiln to draw and re-charge rendered unnecessary. And in constructing kilns,
in place of forming them conical, and opening at their upper parts directly into
the atmosphere, the kiln is constructed with parallel sides, and at the upper
part it is formed into an extensive chamber, terminating with a chimney, into
which chamber the moulded bricks or forms of the materials in a dry or nearly
dry state are moved progressively, so as to become highly heated before they
come to the kiln, into which they are continually discharged. The carrying or
moving the bricks or moulded forms is by carriages, or by an endless platform
or chain, moving through the heated chamber in connection with the kiln, or
the chamber may be heated by means separate from the kiln. The grinding
of the cement is as heretofore.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Robert Owen White in the Great Seal Patent Office on the
21st September 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ROBERT
OWEN WHITE, of Swanscombe, in the County of Kent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-second day of March, in the year of our Lord
One thousand eight hundred and fifty-four, in the seventeenth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Robert Owen White, Her special licence that I, the said
Robert Owen White, my executors, administrators, and assigns, or such
others as I, the said Robert Owen White, my executors, administrators, and
assigns, should at any time agree with, and no others, from time to time and
at all times thereafter during the term therein expressed, should and lawfully
might make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF PORTLAND CEMENT," upon the condition

page_text: (amongst others) that I, the said Robert Owen White, by an instrument in
writing under my hand and seal, should particularly describe and ascertain
the nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said Robert Owen White, do hereby declare
the nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement thereof (that is to say)
Heretofore in the manufacture of Portland cement it has been usual to
combine clay and chalk by grinding and washing in water, the matters being
allowed to settle in suitable reservoirs or vats, and when as free as may be
from water, the substance has been dug out in lumps and dried by artificial
means; such lumps have then been burned in kilns by the aid of fuel mixed
with the lumps in the kiln, the charging and burning not being a continuous
process, the kiln, on the contrary, being charged, burned off, and then emptied.
Now my improvements commence with the mixing of the materials, at which
step in the manufacture, in place of grinding the clay and chalk together in
water, and allowing these matters to settle, the chalk is washed alone, and then
mixed with clay by mechanical means; and in order to get the combined
matters into as convenient a form as may be for drying, the mass is caused to
be moulded into forms, preferring that of a brick, and this it is believed can
be most conveniently performed by forcing the combined matters through
moulding orifices or dies, as when making bricks and tiles, or the moulding
may be by hand; and to facilitate drying, these brick-like forms are hollow. In
mixing the clay and chalk by a pug mill or other mixing machinery a quantity
of fuel is introduced, in order that when burning in the kiln each brick or
moulded quantity of the materials may contain the requisite quantity of fuel,
which is important, not only in consequence of the uniformity of burning which
results, but the charging and drawing may be rendered continuous, and the
stopping of a kiln to draw and re-charge rendered unnecessary. And in
constructing kilns, in place of forming them conical and opening at their upper
parts directly into the atmosphere, the kiln is constructed with parallel sides,
and at the upper part it is formed into an extensive chamber terminating with
a chimney, into which chamber the moulded bricks or forms of the materials
in a dry or nearly dry state are moved progressively, so as to become highly
heated before they come to the kiln, into which they are continuously discharged.
The carrying or moving the bricks or moulded forms is by carriages, or by an

page_text: endless platform, or a chain, moving through the heated chamber in con-
nection with the kiln, or the chamber may be heated by means separate from
the kiln. The grinding of the cement is as heretofore.
Having thus described the nature of my Invention, I will proceed to
explain the best means I am acquainted with for performing the same. In
place of proceeding according to the ordinary process now in use when
making Portland cement, which consists of grinding the chalk and clay
together in water, and then allowing the combined matters to subside, and the
water to drain and run off (till the mass can be dug out), and then driving off
the remaining water by heated stoves, I either grind the chalk alone in water
and allow the same to subside, and the water to separate till the mass can be
dug out, or I grind the chalk in its dry state, by means of rollers, and then
subject it together with the clay to a pug mill, or to rollers, or other mechanical
mixing machine, in order intimately to combine the clay and the chalk, and I
at the same time combine therewith a quantity of fuel, using by preference the
siftings or small of coke, by which the fuel is equally diffused over the whole
mass, by which the subsequent burning is found to be more uniform than when
the dried lumps of the combined clay and chalk are placed in layers in the
kiln interposed between layers of fuel. By thus pugging or mechanically
mixing of the clay and chalk much time is saved, as the water separates more
quickly from the chalk than from the mixture of chalk and clay. The drying,
after pugging or mechanical mixing, will by reason of the compound containing
less water (whether the drying be by artificial heat or by atmospheric means)
be rendered less costly; and although the pugged or mechanically mixed
compound might with advantage over the old process be spread on to and dried
on the old stoves, I prefer to mould the mass into convenient shapes, and
this may be done in hand moulds, or, I believe, most conveniently, by expressing
the plastic compound through moulding orifices, which may be attached to the
pug mills or other mixing machinery, thus making either hollow or solid
moulded forms, which I prefer to be of the shape of ordinary bricks. These
moulded forms, in the state they come from the machine, may be handled and
stacked on artificially heated stoves, such as have heretofore been employed in
this manufacture, or other forms of drying sheds or rooms may be used; but
when the season will admit of it, I prefer to stack them in hacks, in the open
atinosphere or under sheds, like ordinary bricks. I would here remark, that
although it is preferred to grind the chalk separately from the clay, and to mix
the two by mechanical means without water, fuel may be mixed in with the
ordinary compound of clay and chalk, obtained by grinding both together in
water, in which case, when the mass has arrived at a state to be pugged or

page_text: mechanically treated, I mix the fuel by such mechanical means with the
compound of clay and chalk. In place of using sand to dust over the moulded
forms, as when making bricks, I in place of sand, when moulding or shaping
the combined materials, employ the dust of coke or of cinders to dust over
them; and it is preferred that the exterior surfaces of the lumps or moulded
forms should be thus dusted over, as by so doing the surfaces are rendered
harder and are prevented adhering; at the same time the coke thus used acts
as fuel in the burning. In mixing fuel with compounds of clay and chalk, I
find that the quantity introduced into the mass may be varied, and that what-
ever quantity be combined with the compound of clay and chalk, decreases the
quantity required to be loosely put into the kiln. I have mixed various pro-
portions of fuel with the compound, and have found the doing so advantageous,
and I prefer to combine with the lime and chalk, as nearly as may be, the
whole of the fuel requisite for the burning, and with this view I have intro-
duced as much as thirty-three per cent. of the whole mass, and I have used
very little additional fuel placed loosely amongst the lumps in the kiln.
In the manufacture of Portland cement, it has for the most part been usual
to burn a charge in a kiln, and allow it to cool down before drawing it; but in
some cases what are called running kilns have before been attempted to be
used, that is, where quantities are taken out from time to time at the bottom,
and wherein the charging is continued from time to time, so as to keep
up a constant charge in a kiln. Now, in working, I prefer to employ a
running kiln, and in place of allowing the heat and products to pass directly
into the atmosphere as heretofore when manufacturing Portland cement, I
construct an arch or other form of covered flue or tunnel at and communi-
cating with the upper part or mouth of a kiln, and at the further end of the
tunnel or flue it communicates with a chimney or shaft. Through this flue or
funnel a railway or tramway is laid, in such manner as to admit of trucks being
moved into and through the tunnel or flue by chains or otherwise, so that the
trucks may either tip and discharge their contents, or have false or folding
bottoms or otherwise, to discharge their contents into the kiln when they come
over the upper part or mouth thereof. I do not, however, make any claim to
such means of working trucks on railways or tramways, as the same is not new
when used for other purposes. The conveying the dry compound matters for
making Portland cement through a flue or tunnel heated by the products
passing from a kiln will cause such matters to arrive at the mouth of the kiln
in a highly heated state, and the same will more quickly ignite than when
thrown cold into the kiln ; and in thus feeding a kiln, by conveying the matters
through a heated flue or tunnel, I introduce any quantity of fuel which may

page_text: be required beyond what is contained in the blocks into the trucks with the
moulded blocks or lumps of the combined materials; or in place of depending
on the heat passing away from the kiln, as above described, to heat the flue or
tunnel, it may be heated by a separate fire or fires, or by the joint heat of
separate fires, and the flame and heated products passing from the kiln may
be used. And in order to keep in as much heat as may be, and to ensure a
good draft through the flue or tunnel, the outer end is closed with folding
doors, except when a truck is passing in or out.
Having thus described the nature of my Invention, and the manner of
performing the same, I would have it understood that I do not confine myself
to the precise details herein described; but what I claim are, the improvements
herein described in manufacturing Portland cement.
In witness whereof, I, the said Robert Owen White, have hereunto set
my hand and seal, this Twenty-first day of September, in the year of
our Lord One thousand eight hundred and fifty-four.
Witness,
S., CARPMAEL.
ROBERT OWEN WHITE. (L.S.)