Iм- PROVEMENTS IN THE MANUFACTURE OF PORTLAND CEMENT.”
Year: 1870

page_text: LETTERS PATENT to William Goreham and Leedham White, both
of Swanscombe, in the County of Kent, for the Invention of "Iм-
PROVEMENTS IN THE MANUFACTURE OF PORTLAND CEMENT.”
PROVISIONAL SPECIFICATION left by the said William Goreham and
.Leedham White at the Office of the Commissioners of Patents, with
their Petition, on the 12th January 1870.
We, WILLIAM GOREHAM and LEEDHAM WHITE, both of Swanscombe,
in the County of Kent, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE MANUFACTURE OF PORTLAND CEMENT," to
be as follows:-
:
By the usual method of making Portland cement the chalk and clay
after having been mixed together in wash mills and partially dried in
backs is further dried by heat on stoves or otherwise, and the substance
thus obtained is broken into lumps and burnt in kilns in alternate layers
with coke, the latter being in lumps of various sizes in the state in
which it comes from the gasworks or only broken with the hammer.

page_text: Now our Invention consists in avoiding the burning of the lumps of
mixed chalk and clay by contact in the kiln with lumps of coke as
above mentioned, whereby it is believed that much heat is wasted and
in using the fuel in a pulverized form as follows:-We take breeze or
other fuel of a carbonaceous character, and after having reduced it by
grinding or other suitable mechanical means, by preference to a fine
powder, we mix it with the chalk and clay. The result of this intimate
mixing is a homogeneous substance consisting of chalk, and clay, and
fuel, which when dry is burnt in kilns without the addition of more
fuel or at least of such fuel in small quantities only.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Goreham and Leedham White in the
Great Seal Patent Office on tlic 6th July 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, WILLIAM
GOREHAM and Leedham WhiTE, both of Swanscombe, in the County of
Kent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twelfth day of January, in the year
of our Lord One thousand eight hundred and seventy, in the thirty-
third year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto us, the said William Goreham and Leedham White,
Her special licence that we, the said William Goreham and Leedham
White, our exccutors, administrators, and assigns, or such others as we,
the said William Ġoreham and Leedham White, our executors, adminis-
trators, 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 MANU-
PACTURE OF PORTLAND CEMENT," upon the condition (amongst others)
that we, the said William Goreham and Leedham White, our executors
or administrators, by an instrument in writing under our or their hands
and scals, or under the hand and scal of one of us or them, 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

page_text: 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 Leedham White, on behalf of
myself and the said William Goreham, 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 :-
This Invention has for its object improvements in the manufacture of
Portland cement.
By the ordinary method of making Portland cement as practised in
England and usually called the "wet way" the chalk and clay are
intimately mixed together in suitable proportions in wash mills with the
addition of a large volume of water, so as to yield a liquid sufficiently
thin to admit of its being pumped into reservoirs or backs. The chalk.
and clay then settle (remaining mixed) to the bottom and as much
water as possible having been drained off, the mass is then allowed to
dry as far as the weather will permit and is then dug out, and in order
to complete the drying process it is spread on stoves heated with coke
or otherwise. When sufficiently dry the mixture of chalk and clay is
broken into picces and conveyed to the kilns for burning. Now this
burning as usually practised is accomplished by introducing the lumps
of dried chalk and clay into the kilns.alternately with pieces of coke, the
pieces of coke being either of the size as they come from the gasworks
or at most broken down with a hammer. The product obtained from
the kilns is then ground.
-
Now our Invention consists in avoiding the method of burning the
chalk and clay above described, and instead of merely placing the lumps
in the kiln in contact with pieces of coke which necessitates.. the
evolution of great heat before the fire can penetrate to the heart or core
of the lumps, we intimately-mix and incorporate ground or powdered
breeze or other fuel of a carbonaceous character with the chalk and clay
before burning. We thus ensure the contact of each particle of the
chalk and clay with a particle of fuel, by which greater uniformity of
burning is secured at a less expenditure of fuel, for we are thus enabled
to dispense with the use of more fuel in a loose form or at least need use
small quantities only of such fuel.
There are several ways by which our improvement can be carried out;
but we prefer the following inethod:-

page_text: .
We first mechanically reduce the breeze or other fuel to powder by
means of millstones or other suitable grinding apparatus. We then
introduce the powdered fuel into the wash mills in which the chalk and
clay are being reduced to a liquid, whereby the whole is intimately
mixed together and is deposited as a homogeneous substance or nearly
so in the backs. The stiff mud so obtained is then dried and broken into
pieces exactly as is usually done with the chalk and clay alone, and is
then introduced into the kilns either entirely without more fuel in a loose
form or with only small quantities of such loose fuel. We prefer to
employ ground or powdered breeze in the proportion of 30 pounds to the
bushel of finished cement, and to use in layers in the kilns as at present
practised from 10 to 15 pounds of coke in addition. This quantity of
fuel is somewhat less in weight than the fuel employed when working in
the ordinary way, and what is of more importance the breeze even after
grinding is of considerably smaller cost than the coke which it displaces.
A better and more uniform cement is also obtained.
-
We may mention other methods by which the ground or powdered
fuel may be intimately mixed with the chalk and clay according to our
Invention, but which methods are less advantageous than that above
set forth.
(1.) The chalk and the clay may be washed in the usual manner, and
the ground or powdered fuel may be mixed with it by means of a
stationary pug mill or similar mixing apparatus.
(2.) The chalk and clay may be brought from the backs to the works
in tumbrils caused to revolve by the action of drawing by horses or
engine power, and the ground or powdered fuel having been also placed
in the tumbril may be thus intimately mixed with the chalk and clay
on its way to the stoves.
(3.) Instead of tumbrils waggons may be used provided with churning
ór pugging apparatus set in motion by the wheels of the waggons.
(4.) The chalk and clay may be dried and mixed as practised in
Germany, by the so called "dry process," whereby the washing with
water and drying in backs are dispensed with. In this case the fuel
may be mixed with the chalk or clay or with both during the
manufacture.
Although we mention these different methods we do not confinc
ourselves to them, but we claim intimately admixing ground or powdered

page_text: .
fuel with chalk and clay and burning the mixture, and in such manner
to produce Portland cement.
We would remark that we are aware that a Patent dated 22nd March,
1854, for "improvements in the manufacture of Portland cement, was
granted to Robert Owen White, in the Specification of which the mixture
of breeze or other fuel with the chalk and clay before burning was
described, we do not therefore make any claim for the mere admixture
of fuel with the material to be burnt except such fuel be ground or
mechanically reduced to powder, the grinding or mechanical reduction
of the fuel is necessary to the success of the operation, without it a
suitable approximation of the particles of fuel to those of the chalk and
clay cannot be obtained.
For the purposes of this Specification, we mean by Portland cement,
a cement made by mixing together chalk and clay, and by the term
breeze we mean the siftings or screenings of coke as separated at the
gasworks.
In witness whercof, I, the said Leedham White, have hereunto
set my hand and scal, this 5th (Fifth) day of July, in the year
of our Lord One thousand eight hundred and seventy.
LEEDHAM WHITE.
(L.S.)