AN IMPROVEMENT IN THE MANU- FACTURE OF PORTLAND AND OTHER CEMENTS."
Year: 1881

page_text: LETTERS PATENT to Isaac Charles Johnson, of Mayfield House, Gravesend, in
the County of Kent, for an Invention of "AN IMPROVEMENT IN THE MANU-
FACTURE OF PORTLAND AND OTHER CEMENTS."
PROVISIONAL SPECIFICATION left by the said Isaac Charles Johnson at
the Office of the Commissioners of Patents on the 15th August 1881.
ISAAC CHARLES JOHNSON, of Mayfield House, Gravesend, in the County of Kent.
"AN IMPROVEMENT IN THE MANUFACTURE OF PORTLAND AND OTHER CEMENTS."
This Invention relates to a certain process of mixing the materials from which
cements are made in a more perfect manner than heretofore accomplished.
The manufacture of Portland cement in the first process thereof was originally
carried on by washing together chalk and clay in mills with much water to
produce their amalgamation.
The
The matters thus mixed were run into backs or reservoirs after subsidence.
superincumbent water was drained off and the mass was allowed to remain until it
became stiff enough to be wheeled in barrows to the drying stoves.
An improvement on this method was invented, and Letters Patent were granted
to Mr. William Goreham for mixing together the materials with a lesser quantity
of water in harrow mills. When roughly ground the mixture passed through iron
gratings into a pit, and was raised by an elevating wheel into a trough supplying
horizontal millstones.
The slurry after having been ground by these ran into a pit and was pumped
therefrom onto the drying floors direct, thus rendering the drying or subsiding
reservoirs unnecessary.
The slurry however being imperfectly mixed and passing quickly in this state
through the iron gratings, there is not sufficient time to incorporate in the proper
proportions the chalk with the clay, causing oftentimes considerable inconvenience
after dessication and calcination.
Now by using a subsequent operation which forms the subject of my present
Invention, I mix together a considerable quantity in suitable mills of the slurry after
FD 131

page_text: it comes from the millstones, and ensure a more perfect mixture of the atoms by
bringing them into close relationship, mechanically considered, on which depends
the more perfect union in the chemical operation produced by calcination, and by
which alone can the best results be obtained in the production of perfect clinker
so perfect cement.
For the purposes of my Invention I use, by preference, a semi-circular trough
in which vertical arms or knives rapidly revolve, stirring up a considerable mass
of slurry before entering the pump pits.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Isaac Charles Johnson in the Great Seal Patent Office on the
15th February 1882.
ISAAC CHARLES JOHNSON, of Mayfield House, Gravesend, in the County of Kent.
"AN IMPROVEMENT IN THE MANUFACTURE OF PORTLAND AND OTHER CEMENT."
This Invention relates to a certain process or system of mixing the materials
from which cements are made in a more perfect manner than heretofore
accomplished.
According to my Invention I submit the imperfectly mixed or washed chalk
and clay as it comes from the harrow mill to a rapid agitation in a churn like
apparatus or teaser, to ensure a perfect amalgamation and a closer relationship of
the atoms, mechanically considered, than is possible by the known system of wet
grindstones, whereby I dispense with the wet grinding operation and the usual
appliances connected with them, and also with the services of a "wet miller." My
churn like rapid agitator is preferably of semi-circular shape, and has vertical
arms or knives on a horizontal shaft which dash the slurry violently within the
churn before it passes into the pump pits.'
This method is the only one necessary if the chalk be of a soft nature; but when
the chalk is hard or has particles of flint with it, I pass the slurry through
between a pair of rollers to reduce these particles, in which case I arrange the
rollers between the harrow mill and the agitator.
The following remarks will explain the known processes, so that my present
patented process or system will be gathered by the concluding paragraphs.
The first method of making Portland cement was, by mixing chalk and clay
in the necessary proportions in a machine, very much like an ordinary mortar mill,
that is, a pair of vertical edge runners were made to run round in a basin with an
iron bottom. A pipe supplied this mill with a large quantity of water. These
edge runners having both a grinding or crushing motion as well as a mixing effect,
reduced the materials to a state of tolerably fine division, the semi-fluid mass
passed through iron gratings, thence to the reservoir or backs.
The objection to this method was that the runners were of great weight, and
having to move somewhat rapidly required considerable power to drive them.

page_text: In order to obviate this difficulty and also to produce better results, a system of
harrows was employed revolving horizontally in a large receptacle, from 15 feet to
18 feet diameter, carried round by arms proceeding from a vertical spindle.
The chalk and clay are put into this mill with about the same quantity of
water as in the other case, but the whole has to pass through horizontal gauze
wire sieves, 20 to 30 meshes on the side of the square inch. The advantage of this
system is, that the abrasion of the particles one against another reduce them to a
state of fineness with much water to pass through the wire gauze before running
into the backs.
In a small manufactory, where these backs could be tolerably near the drying
stoves, it was all very well, but in a larger place where some acres of back space
are needed to contain a sufficient quantity of slurry and necessarily distant, it
became an expensive and troublesome matter to remove it to the drying stoves.
This led to what is termed "Goreham's process," which consists in using a harrow
mill in the first instance for roughly mixing the chalk and clay together.
This mixture passes through vertical iron gratings having openings of about
1 of an inch between the bars into a pit, from which it is raised either by an
elevating wheel and buckets, or by an endless band and buckets into a horizontal
trough to supply horizontal millstones to further reduce the particles of chalk and
clay. After passing between the millstones the matter called slurry is conveyed
into a pit from which powerful force pumps raise and push the thick material
through pipes on to the drying stoves without further manual labour other than
merely luting it to some degree of uniformity in thickness. I say this thick
material, because the virtue of Goreham's process consists in the fact that so little
water is used in the combination of the chalk and clay that it is sufficiently thick
(4 lb. 2 oz. to the imperial quart) to be deposited at once by the pumps on to the
drying place without using depositing backs at all, and of course saves the labour
and expense of subsequent removal.
This was a great step in advance in the economical working of a cement manu-
factory, and in connection with my patented (May 1872) chamber system by
which coke ovens and fluid drying stoves are entirely dispensed with, the whole
process of cement making is considerably simplified, and by which better results
are obtained as regards quality of product.
In both systems there is a want of uniformity in the ultimate results, that is, in
the finished ground cement. First, the back system; the slurry being very thin
having a large quantity of water in its composition, when it is caused to run into
backs in consequence of the difference of the specific gravity of the chalk as
compared with that of the clay, a deposit was formed at the entrance of the back,
or at the point of delivery; this deposit consists of particles of chalk not having
the proper quantity of clay in combination, the latter having gone away to a
distance in the back with a considerable quantity of chalk, but not with the
proper quantity. Thus in different parts of the back there would be different
mixtures, and at the entrance of the back, or at the point of deposit, would be
found a large quantity of matter called sand, which is in reality unmixed particles
of chalk which has to be removed as useless. Goreham's process to a great extent
obviates this great want of uniformity and saves this waste.
It has been a perplexing problem, especially in very hot weather, with many
manufacturers, why in the testing room there should be such differences in the
breaking weights of test "briquettes," for it has frequently been found that of the
same parcel of cement one briquette made under the same circumstances as
another, gauged with the same quantity of water as another immersed in water, after
gauging the same time as another there is found a great difference in resistance to
rupture, one breaking at 1400 to 1500 lbs. per briquette of 21% square inches of
section, whilst another will break at 600 to 700 lbs., also clinker produced from
chalk and clay of the same quality and in the same proportions, calcined so as to
weigh 120 lbs. per bushel when ground. Some will set in a few minutes, whilst
other parts of the same lot will require a few hours,

page_text: This want of uniformity is due to imperfect amalgamation of the chalk and
clay. Barrows full of these materials are thrown into the harrow mill, a con-
siderable portion of each is separately pushed through the gratings before they
have had sufficient time to get properly mixed, and then passing rapidly through
the millstones, and onward to the pumps, the matter is not in sufficient mass for
proper amalgamation.
In order to effect a better mixture I use a semi-circular trough to contain slurry
as it comes from the harrow mill, retaining the same for some time before entering
the pump pit.
In the direction of the length of this trough a shaft is placed carrying vertical
arms into which horizontal bars of iron are fixed, forming a kind of large churn in
which they revolve rapidly in the mass of slurry, which so perfectly mixes the
chalk and clay together as to ensure perfect uniformity of the mass.
As the perfection of the finished article is due to the perfect admixture of the
particles as well as to their fineness, I pass the roughly prepared slurry at once
from the harrow mill to the teaser or churn without passing it through the "wet
millstones" at all.
This plan or system enables me to dispense entirely with the costly appliances
for wet grinding, such as bevil wheels, spindles, pinions, millstones, and the
services of a wet miller. The teasing machine, which may be of any description,
but is preferably a churn like one, which can be driven with a strap or gearing
from the horizontal shaft of the harrow mill or elsewhere, as may be most con-
venient, it requiring a small amount of power compared with that required to
drive millstones. The completion of the process depends on the friction or
abrasion of the particles and the dash of the machine. This churn like apparatus
acts as an additional mixer as well as a finisher.
Having now described the nature of my said Invention and in what manner
the same is to be performed, I declare that I claim :—-
The above described new process or system of treating slurry (after leaving the
harrow mill) to produce a perfect amalgamation and close relationship of the
particles, and in consequence a better clinker for cement than heretofore.
Secondly. I claim effecting a perfect amalgamation of the particles of washed clay
and chalk, termed slurry, by a dashing onward agitating action within a churn like
apparatus having rapidly revolving agitators or their equivalents, as set forth.
In witness whereof, I, the said Isaac Charles Johnson, have hereunto set
my hand and seal, this Fourteenth day of February, in the year of our
Lord One thousand eight hundred and eighty two.
ATT
TAHVAAN