A Furnace or Kiln for Calcining Cement Materials.
Year: 1898

page_text: Date of Application, 13th Sept., 1898-Accepted, 29th Oct., 1898
COMPLETE SPECIFICATION.
A Furnace or Kiln for Calcining Cement Materials.
I, VALDEMAR KJELDSEN, of Ennigerloh, Westphalia, in the Empire of Germany,
Cement Expert, 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 :-
This invention relates to a furnace or kiln for calciuing cement materials.
As is well known so called blast furnaces or kilns are employed for calcining
lime, cement and similar material. This is usually effected by introducing the
material to be burnt and the fuel in separate and successive layers until the kiln or
furnace is filled. The firing usually takes place from below. The supply of air
for combustion is conveyed through the high kiln or furnace which acts as a
chimney. The zone of combustion gradually rises. By drawing off the already
calcined material the fire zone is maintained at a predetermined height so that the
cooling material warms the air supplied for combustion, and the gases of combustion
warm the fresh material to be burnt.
The ordinary furnaces or kilns, however, possess the disadvantage that, when
materials which soften or crumble are being treated, the draught is easily clogged
or stopped because the said material by its softening or crumbling cuts off the
necessary supply of air.
It has been demonstrated in practice that material is always calcined unequally
in such furnaces so that it is necessary to sort it into weak and hard brands or
charges. As the weak brand is a product of inferior quality only it is very un-
economical to burn in furnaces or kilns. This disadvantage can easily be obviated
by altering the furnace in such a manner that fuel can be supplied thereto at any
desired point. To this end the furnace is provided with a large number of holes which
can be easily closed and opened and which enable the process to be observed from
the outside, and, when necessary, permit air to be supplied to the fuel.
In the drawing I have illustrated in vertical section a furnace of this construc-
tion, the said furnace being built of a number of iron rings a, a the lowermost
of which rests upon iron supports b, b. At its upper part the furnace is separated
from a chimney by a dome.
The operation of the furnace is as follows:--The lower open part of the furnace,
which is designed for the removal of the completely calcined material, is filled
with incombustible materials upon which an easily combustible layer of wood and
coal rests. The charging is completed in similar layers, that is to say, charge and
fuel alternately. When the furnace is half filled the lower wood layer is ignited.
The flame rises higher and higher, and, in proportion as the fire rises, the furnace is
filled alternately with material to be calcined and fuel. When calciued material is
removed below then further material is added above. With the assistance of the
air inlets c, c arranged around the whole surface of the furnace the process can be
watched and regulated by introducing air at any part where combustion is retarded.
Practical experiments have shewn that it is very possible to obtain in a furnace of
this kind a practically homogenous calcined product if the attendant exercises the
necessary care and attention.

page_text: The technical improvement consists in the fact that in furnaces wherein the
material moves in a vertical direction combustion is practically maintained in one
zone and that air can be introduced at those parts at which combustion, by reason
of want of air, is retarded.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
Calcining-furnaces or kilns the walls of which are formed with a large number
of orifices or openings which have for their object to regulate the combustion,
substantially as hereinbefore described and illustrated.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.