IMPROVEMENTS IN THE MANufacture OF PORTLAND CEMENT
Year: 1870

page_text: LETTERS. PATENT to William Goreham, of Swanscombe, in the County
of Kent, for the Invention of "IMPROVEMENTS IN THE MANufacture
OF PORTLAND CEMENT."
Sealed the 15th September 1870, and dated the 12th July 1870.
PROVISIONAL SPECIFICATION left by the said William Goreham at
the Office of the Commissioners of Patents, with his Petition, on
the 12th July 1870.
I, WILLIAM GOREHAM, 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:-
The manufacture of Portland cement has been chiefly conducted in
two ways; by the so called wet or English method and by the dry or
German method.
By the wet method of manufacture the chalk and clay are washed
and thoroughly mixed in wash mills by the aid of a large quantity of
water amounting to several times their weight, so as to bring the whole

page_text: to the state of a liquid sufficiently thin for it to flow into backs or reser-
voirs. The water thus mixed with the chalk and clay has again to be
separated from it, partly by drainage and evaporation in the backs, and
partly by drying the deposit of mud so obtained on stoves or otherwise,
so as to admit of its being burnt in kilns.
By the dry method of manufacture the chalk and clay are each dried
artificially and ground separately, and are then mixed in pug mills or
otherwise with the addition of sufficient water to bring the whole into a
paste suitable for moulding into bricks or other shapes, which are then
dried and burnt.
Now by my method I equally avoid the mixing the chalk and clay
with several times their weight of water, which has afterwards to be
driven off as by the wet method, and the expense in the dry method of
drying the chalk and clay separately before grinding, which necessitates
water being again mixed with the powder, in order to bring it into the
state of bricks or lumps, which have once more to be dried before they
are burnt in kilns, and instead thereof I take chalk and clay in their
natural state and grind them between millstones, or with other suitable
grinding apparatus, either together or separately mixing them with the
aid of so much water only as shall be sufficient to facilitate the grinding,
and as shall deliver the material in the state of a finely ground and
homogenous mud or even of a paste capable of being moulded into
bricks or lumps, which can then be taken at once (and without the
necessity of separating the water added in grinding) to the stoves for
drying before burning. When working in this manner I prefer to
admix ground or powdered fuel with the chalk and clay; I either mix
the fuel with the ground chalk or ground clay or with both, or I grind
it together with one or both of them. I prefer to use ground or
powdered breeze (which is the small or refuse of coke), and in the pro-
portion of about 30 lbs. to the bushel of finished cement.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Goreham in the Great Seal Patent Office
on the 11th January 1871.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria;. by Her
Letters Patent, bearing date the Twelfth day of July, in the year of
our Lord One thousand eight hundred and seventy, in the thirty-fourth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said William Goreham, Her special license that I,
the said William Goreham, my executors, administrators, and assigns,
or such others as I, the said William Goreham, my 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-
FACTURE OF PORTLAND CEMENT," upon the condition (amongst others) that
I, the said William Goreham, my executors or administrators, by an
instrument in writing under my, or their, or one of their hands and
seals, 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 William Goreham, do hereby
declare the nature of the said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained in
by and the following statement thereof, that is to say:-
Portland cement is made from chalk and clay. There are at present
two different methods of manufacturing Portland cement.
According to the wet method commonly practised in England the
chalk and clay are first "washed" in wash mills with harrow tines, and
are so mixed with about five times their weight of water. They are thus
thoroughly disintegrated and mixed together and the mixture flows out
of the wash mills as a liquid of about the consistency of milk.
,,
The next process of manufacture is the separation of the water which
has thus been mixed with the chalk and clay in order that the "slip," as
the mixture is called, may be sufficiently dried for burning in kilus. The
liquid mentioned is therefore run into reservoirs or "backs in which
the chalk and clay gradually subside to the bottom, and the water above
is for the most part removed partly by drainage and partly by evaporation;
this process occupies from six to twelve weeks, according to circumstances.

page_text: The chalk and clay are then dug out of the "backs "in the state of mud,
more or less thick, and the "slip" after having been further completely
dried by artificial means is then burnt in kilns and ground.
According to the dry method, as frequently practised in Germany, the
chalk and clay are each ground separately, having been first artificially
dried to facilitate the grinding; they are then mixed, and the mixture
thus resulting is made into bricks or lumps by the aid of just sufficient
water to bind it together; the bricks or lumps are then burnt in kilns
with or without being previously dried on stones or otherwise.
Now according to my Invention the chalk and clay are roughly mixed
together in a wash mill with a small quantity of water only, say from one-
fifth to one-third of the weight of the whole. The product resulting from
this operation is not a liquid but a mud with coarse particles of undisente-
grated chalk and clay interspersed throughout it. I then pass this mud
through a pair of millstones such as are now used for grinding cement
after it comes from the kilns, and thereby thoroughly comminute and mix
the whole. The mud is then immediately transferred to the drying stoves
or chambers, without being poured into the reservoirs or backs, and the
dried slip is then burnt in kilns. A portion of the fuel for burning the
cement may be mixed with the chalk and clay, as is described in the
Specification of a Patent granted to me and another and dated the Fourth
day of February One thousand eight hundred and seventy, No. 99, in
such case the fuel is added to the other materials in the wash mill.
I avoid by my process the time, space, and expence involved in driving
off the excessive quantity of water with which the chalk and clay are
mixed according to the wet way of manufacture, inasmuch as I succeed
in effecting the perfect disintegration and mixing of the materials with
a small quantity of water only, and in thus obtaining a product which
can at once be dried by artificial means without the aid of drainage or
evaporation in backs.
I also avoid the expence incurred in the so-called dry process by drying
and grinding the chalk and clay separately, and in afterwards mixing
them with water, and I also obtain finer comminution and more uniform
admixture of the materials than it is believed can be obtained by the dry
method.
Although I have adopted by preference the above method of partly
mixing and disintegrating the chalk and clay in a washmill with harrow
tines and afterwards of completing the process by further grinding the

page_text: mud between millstones, this method may be varied, but I claim as my
improvements in the manufacture of Portland cement, disintegrating and
mixing the chalk and clay by grinding or crushing when wet, but without
excess of water, and then at once drying and burning the mud thus
obtained without the separation of water in setting backs.
In witness whereof, I, the said William Goreham, have hereunto
set my hand and seal, this Tenth day of January, in the year of
our Lord One thousand eight hundred and seventy-one.