Materials for the Manufacture of Portland Cement.
Year: 1886

page_text: Materials for the Manufacture of Portland Cement.
I CHARLES SPACKMAN of Sileby near Loughborough in the County of Leicester
Cement Maker do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement:-
Two methods for the manufacture of Portland Cement are in general use the
wet and the dry and my Invention applies to the dry method. By this process
the mixture of raw materials is in the first place ground to a fine powder in the
dry state. This dry powder or dust is mixed with a greater or less quantity of
water the object to be attained being the production of lumps or forms of suitable
shape for burning in the kilns. The wet mixture or the lumps or bricks into
which it has been moulded is then dried on floors heated from below by furnaces or
coke ovens or in chambers or on floors heated in various ways by the waste gases
from the kilns and when dry is itself removed to the kilns to be burned.
The object of my Invention is to effect the drying process in the kilns in which
the burning is to be afterwards conducted. By this means obtain a considerable
saving in the cost of labour, as the raw materials are only once handled instead of
twice in passing from the mixing or moulding machinery to the kilns. I am
enabled to dispense with the costly drying arrangements at present in use, and to
entirely save the cost of fuel for the drying process, when, as is often the case,
the waste gases from the kilns are not employed for heating drying-floors or
chambers.
To carry out my Invention I adopt that modification of the dry method by
which a small quantity of water is added to the dry dust, sufficient only being
used to cause it to bind or adhere together when tightly squeezed in the hand, the
mixture being then by suitable machinery compressed into convenient forms such
as bricks cubes or balls. These, although containing a considerable quantity of
water, are very compact and dense and instead of submitting them to a pre-
liminary process of drying as before described I at once remove them in the damp
state to the kilns which are loaded exactly as they would have been if the materials
comprising the charge had been previously dried.
.
The form of kiln suitable for the working of my Invention is that known as the
intermittent kiln, and it may be applied to any existing kilns of this type. Their

page_text: shape is occasionally varied to suit different conditions or the opinion of the
designer. In some cases the products of combustion pass off through domes on
each kiln, in others a number of kilns are arranged in connection with a powerful
chimney shaft. In all cases however the principle of burning the cement is the
same.
Each kiln is loaded, burnt off, and allowed to cool. The charge is then drawn
and the operation of loading and burning is repeated.
I will now describe the treatment of a loaded kiln with reference to the accom-
panying drawings which show the application of my Invention to intermittent
cement kilns of a form in very general use.
Fig. 1 is a vertical longitudinal section through two kilns. Fig. 2 a cross
section through one kiln, Fig. 3 a plan at base of domes and Fig. 4 a plan at base
of kilns.
CC are covers, preferably of cast iron, which may be raised or lowered at will
by levers and chains or other suitable arrangement.
By means of these covers the tops of domes may, when required, be tightly
closed down. D is a flue or pipe, which may be of sheet iron, and is fixed at some
convenient place above the height to which the kilns are loaded. This is closed at
the extreme ends, and is connected with the interior of each kiln by branch pipes
E E, each of which is provided with a simple valvular arrangement F, Fig. 2, for
making or closing the communication between the kilns and the main pipe D. In
some cases, such as when broad low kilns are adopted, I may prefer to carry the
branch pipes E round the upper part of kilns, connecting them with the interiors at
several places by smaller branches.
Suitable means, such as sheet iron flaps, or doors H H, are provided for closing
the drawing hole or holes, or they may be closed by temporary walls. A chamber
may thus be formed beneath the bars of kilns.
I, Fig. 4, is a main pipe or channel, closed at one end, and connected at the other
end J with a gas exhauster, an exhausting fan, or other means for producing an
artificial draught. Branches L M communicate with each kiln at some convenient
place beneath the bars. Each of these branches is provided with an arrangement
for making or closing communication between the kilns and the main pipe or
channel I. A blank flange or flap N, Fig. 2 is very suitable. It may be effectually
secured by screws, and while efficiently closing, it at the same time prevents the
entrance of foreign matter to the pipes.
We will suppose that kiln B is loaded with wet material and that A has
nearly burned off, the actual process of calcination being nearly or quite at
an end.
The charge will then have sunk to about the level indicated by the dotted line,
and it will consist of a mass of hot cement clinker, the upper portion of which will
be in a state of glowing redness.
At about this condition of the burning kiln the covers C C of both it and the one
containing the wet material to be operated upon are closed. The valves F in the
branch pipes E E communicating with the interiors of these two kilns are opened
and the drawing holes of B containing the wet charge are closed by the flaps
HH or by temporary walls. The loading holes O P R (Fig. 2) are carefully
stopped.
Kiln B is now put in communication with the main pipe I, Fig. 4, by opening
the flap N, or whatever other arrangement is provided in branch M, the branch L
being closed. The exhauster, or other apparatus for producing a forced draught,
at J is now set working the effect of which is to draw a current of air through the
hot clinker in A. This air which is now at a high temperature passes out by the
branch E in kiln A along main pipe D through branch E in kiln B downwards
through the mass of wet material this kiln contains and finally by the branch M
and main pipe I to the exhausting apparatus at J. The operation is continued
until the contents of B are dry. B may then be lighted and will in its turn dry
the contents of another kiln, and so on.

page_text: Kilns A and B are supposed to form two of a series, in which one or more in
any position may be used for heating the air to dry the contents of one or more in
any other position. In the case of two kilns only being employed it will simply
be necessary to connect them above the loading level by a flue or pipe. Any
greater number may also be connected in the same manner, without the inter-
vention of a main or gathering flue or pipe D, but it will be obvious that by
this method any one kiln can only be worked in connection with the ones
adjoining it.
I may in some cases prefer not to admit the air to be heated through the hot
mass of clinker, but to pass it wholly or partially over the surface.
For this purpose suitable apertures may be provided in the walls of kilns, or the
temporary filling of either or both of the upper loading holes O P, Fig. 2, of the
hot kiln may be removed. The drawing holes at bottom may or may not be
closed.
In the event of the products of combustion from a number of kilns passing to
one shaft it will only be necessary, when commencing the operation of drying, in
place of lowering the covers CC of domes, to close the dampers connecting the
kilns operated on with the shaft. The other details of the process are conducted
just as they would be if the kilns were used as open ones.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is
In the manufacture of Portland Cement by the dry process, the method of
passing an artificial current of air through the calcined cement, after the process of
combustion in an intermittent kiln is completed, so as to heat the air and the
subsequent utilization of this heated air for the desiccation of a charge of raw
material stacked in another kiln or kilns ready for burning in the manner herein
set forth.
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