IMPROVEMENTS IN KILNS FOR BURNING LIME AND CEMENT
Year: 1868

page_text: LETTERS PATENT to Henry Young Darracott Scott, of Ealing, in the
County of Middlesex, Lieutenant-Colonel in the Royal Engineers,
for the Invention of "IMPROVEMENTS IN KILNS FOR BURNING LIME AND
CEMENT."
Sealed the 14th August 1868, and dated the 2nd May 1868.
PROVISIONAL SPECIFICATION left by the said Henry Young Darracott
Scott at the Office of the Commissioners of Patents, with his
Petition, on the 2nd May 1868..
I, HENRY YOUNG DARRACOTT SCOTT, of Ealing, in the County of
5 Middlesex, Lieutenant-Colonel in the Royal Engineers, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN KILNS
FOR BURNING LIME AND CEMENT," to be as follows:-
My Invention of improvements in kilns for burning lime and
cement has for its object to render the continuous system of burning
more economical, certain, and uniform than the processes now in use.

page_text: In carrying out my Invention fire-places are arranged in such a
manner as regards the firing chamber as to ensure that the flames from
the fuel shall act upon many points of the mass to be operated upon,
and that this mass in its downward course shall be gradually subjected
to an increased heat towards the termination and most difficult part of
the operation. To this end I construct long fire-places on each side of
the firing chamber, arranged in two or more tiers and communicating
with this chamber by lateral openings. These fire-places are of
considerable length and are fed with fuel at one or both ends. I
sometimes employ only one tier of fire-places, but I prefer to use two or
more, as the upper ones enable the kilns to be made of much greater
capacity and are useful in the earlier stages of calcination which the
lower tier will then complete. The lowest part of the firing chamber,
or that below the bottom tier of fire-places, forms a cooling chamber, and
is so arranged that the heat derived from it is made subservient both
to feed the fire-places with hot air and also act as a smoke consumer.
For this object flues or air passages are inserted in the walls and
divisions of the cooling chamber, and through these flues sufficient air
is passed to carry on a coking process on the fuel in the fire-places
above, leaving the gaseous products derived from its partial combustion
to be fully consumed by the air which passes in at the draw holes of
the cooling chamber, and so up through the body of the kiln. To
facilitate the expulsion of the carbonic acid pipes or conduits are also
introduced into the walls and divisions of the cooling chamber, and by
this means steam is generated and is conducted by suitable outlets or
jets into the mass contained in the firing chamber, so that it may
ascend into the body of the kiln and form an atmosphere of vapour
.of water in and amongst the ignited limestone.
ESPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Henry Young Darracott Scott in the Great Seal 30
Patent Office on the 2nd November 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
YOUNG DARRACOTT SCOTT, of Ealing, in the County of Middlesex,
Lieutenant-Colonel in the Royal Engineers, send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Second day of May, in the year of our
Lord One thousand eight hundred and sixty-eight, in the thirty-first
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Henry Young Darracott Scott, Her special
licence that I, the said Henry Young Darracott Scott, my executors,
administrators, and assigns, or such others as I, the said Henry Young
Darracott Scott, my executors, administrators, 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 KILNS FOR BURNING LIME AND CEMENT,"
upon the condition (amongst others) that I, the said Henry Young
Darracott Scott, 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 caldar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Henry Young Darracott Scott, do
hereby declare the nature of my said Invention, and in what manner
the same is to be performed, to be particularly described and ascertained
in and by the following statement, reference being had to the Drawing
hereunto annexed, and to the letters and figures marked thereon (that
is to say):-
The improvements relate to that class of limekiln in which the
lime is burned by a continuous process, the fires being. situated at the
side or sides or around the circumference of the firing chamber in+
which the limestone to be calcined is contained; and the object of the.
improvements is to save fuel by burning the lime in a more economical:
and uniform manner than is at present practised..
In carrying out my Invention I so arrange the different parts of the
kiln as to make use of the waste heat of the lime already calcined for
raising the temperature of a supply of fresh air which is admitted.
through it with the object of consuming the combustible gases,
(included in ordinary language under the term. smoke) which results

page_text: from burning a thick layer of carbonaceous fuel by a limited access of
air inadequate for its complete combustion. I purposely also adapt the
arrangements of the grates and employ other well-known means (tending
to the increase of such combustible gases) to the greatest degree, and I
regulate the quantity of atmospheric air which is admitted through the
heated lime so that it may be proportioned to the combustible gases
which have to be consumed. In this manner not only is the waste
heat made available, but the gaseous fuel is chiefly consumed in and
amongst the lime where the heat is required instead of near the firc-
bars at some distance from the lime, at the same time actual solid
contact between the lime and fuel to be consumed (which is always
injurious to the lime) is avoided.
In the accompanying Drawing I have shewn at Fig. 1 a transverse
section, and Fig. 2 a longitudinal section of a kiln constructed in the
manner which is best adapted for effecting these objects. The barrel
of the kiln is composed of three compartments consisting, first, of a
drying and heating chamber A at the upper part of the kiln, and into.
which the limestone is first introduced, and from which it passes
downwards as the calcined lime is withdrawn at the openings O, O, at
the lower part of the kiln. The second compartment is below the
first one A and is the firing chamber B, in which the limestone is
converted into lime by the heat of the fires S and F. A cooling
chamber C forms the third compartment, and into this the lime
descends after calcination and when it is made to give up its waste
heat to streams of fresh air which are allowed to enter through
openings in the draw hole doors O, or through equivalent openings in
the brickwork of the cooling chamber, which doors or openings admit.
of being regulated. Similar openings in the brickwork at a higher level
than the draw holes O are useful when the periods between the
drawings are occasionally long; they are then employed instead of.
the lower holes O. By keeping the latter shut the lime is saved from
too lengthened an action of the moisture which passes in with the fresh
air, and which of course,exerts a slacking action upon it after the lime
has reached the temperature at which it will combine with water.
The fresh air may be introduced immediately below the fires, but by
taking it in at a lower level more waste heat is saved and a
bettter distribution of it is effected. Somewhat below the bottom
of the firing chamber B a portion of the fresh air (admitted through
the doors O) is allowed to pass upwards by the flues f, f, whilst the

page_text: remainder flows onwards through the firing chamber B with a.
constantly increasing temperature derived from the lime, until it
encounters the combustible gases which are issuing from the fire-places
F and S to the throats t and g. The portion of the air passing up
from the lower part of the kiln by the channels f,f, is led into the
firing chamber at p, p, for the more perfect admixture of the air with
the combustible gases which are to be consumed as fuel.
The fire-places S and F are of novel construction, as will be seen at
Fig. 2. They are of considerable length and consist of alternate dead
spaces or shelves K and spaces with fire-bars I. The fire-places are
placed on each side of the firing chamber and are arranged in two or
more tiers communicating with this chamber by lateral openings, and
are fed with fuel at one or both ends. For caking coal which produces
clinkers. The fire-bars I are set two feet six inches to three feet below
the shelves K, but for non-caking coal which produces soft ashes they
may (in order to save space) be placed on the same level with them.
The fires are fed through the doors at the ends of the kiln, and the
charges are thrown so as chiefly to lodge upon the shelves K, K, (see
left-hand side of the transverse section Fig. 1. Here the fuel undergoes
a caking process, and the hydrocarbons are expelled and escape through
the openings t and g, and arc consuned by the fresh air which is
constantly rising from the holes ○ below or is passing through the
holes p, p, as already described. When the fuel on the shelves K is
partially coked and the incandescent fuel over the fire-bars I has sunk
some inches below the general level of the fuel a long tool or rake
is introduced by end doors whose position is indicated in the longitudinal
section by the letter a in order to level the fuel and admit of a fresh
charge being thrown in. Clinkers are removed through the openings T,
Fig. 1, which also serve to enable any pieces of lime which may
accidentally get jammed into the throats g and t to be thrust out and
also to admit a draft of cold air to bring down the lime charge if from
too long a delay in drawing it has arched itself across the kiln.
Sufficient air to keep up the necessary rapidity of combustion is brought
under the fire-bars I, I, either by channels in the brickwork of the
kiln, or as shown in the Drawing through the doors b, b, of the
ash-pit L, L. The first plan is only advisable when the lime cooling
chamber can be made of great depth and there is waste heat available
for warming the air for the fires as well as for the consumption of their

page_text: combustible gases. The latter plan is the simpler and will generally be
the best. Instead of feeding the fires from the end or ends of the kiln
I sometimes employ hoppers r, as shewn on the right-hand side of
the transverse section, Fig. 1. These hoppers are placed at the sides of
the kilns so as to obtain a constant delivery of fuel on the shelves K,
and over the fire-bars, thus obtaining a continuous system of coaling
that requires only the occasional use of the rake to keep the shelves
free from an excessive accumulation of hard caked coal which might
otherwise impede the supply. The grates above described, especially
the first, are adapted for the use of cheap, small, and dirty coal. If,
however, non-caking coal without clinker is to be employed I sometimes
make use of a form of fire-place in which the bars are placed at a. steep
angle in continuation of the sole of the hopper which feeds them.
Other forms of fire-place, including the ordinary one, are also available,
and may be employed, if thought advisable, on grounds of economy of
construction and of simplicity, taking care however to have a much
thicker layer of fuel than is generally used so that a considerable volume
of combustible gases may be generated. The quantity of gaseous
products derivable from carbonaceous fuel burned under the foregoing
conditions may be augmented as is well known by passing vapour of
water through the incandescent fuel. The nature of the changes which
are undergone by the fuel when burned under such conditions, whether
as respects limited air supply or a supply of steam, are too well known
and understood to require description, but it may be advisable to point
out that the advantage resulting from the use of the steam does not
confine itself to an increased supply of gaseous fuel, but that when the
gases so produced are again reoxydised assistance is rendered in the
expulsion of the carbonic acid from the stone. It is well known that
limestone parts with its carbonic acid with great difficulty in an
atmosphere of carbonic acid, and in proportion as such an atmosphere
prevails the difficulty of decomposition is greater. The partial substitu-
tion therefore of vapour of water for carbonic acid which results from
the employment of steam in the manner described in and around the
limestone in the firing chamber greatly facilitates the process, and
consequently effects: a saving of fuel. The steam may be generated in
pipes acting as boilers laid on the stops of the division walls between the
draw holes and fitted with proper conduits to the ash-pits L, L, or the
boilers may
be built into the side walls of the kiln or from the throat
sill at t, or again it will be sufficient to keep the ash-pits wet by any

page_text: simple means. The quantity of air to be admitted by the air holes
below the fires for the consumption of the combustible gases depends
mainly on the thickness of the layer of fuel, the freedom or otherwise
with which it burns into a spongy mass giving free access of air through
its pores, and on the employment of steam or its omission, but also of
course on the chemical composition of the coal, which indeed, as well
as the two first-named elements of variation, influences again the
quantity of steam which it is possible to use with advantage. The rate
however at which the fuel is being burned, together with the rate of
ingress of air to the ash-pit, it is easy to calculate, on well-known
principles of chemical combination how much gaseous fuel remains
to be consumed in the body of the kiln, and consequently how much
air should be admitted for its consumption through the inlets in the
bottom part of the kiln. In a kiln thirty-five feet in height in the pan
one hole in the fire-door three-quarters of an inch in diameter will admit
from eight to ten cubic feet of air per minute, the kiln being in full
firing, and with limestone of average quality about one ton of coals w¨
be required for the burning of twelve to fifteen tons of stone.
From the above description of my process it is evident that many
modifications might be introduced without departing from the principle
upon which the process is based. It would, for instance, be easy to use
one fire-place or group of fire-places to supply several kilns with gaseous
fuel to be burned with fresh air entering through the hot calcined lime,
as above described; or, again, a portion of the gaseous fuel may in a kiln
of a circular form in plan be taken up through a central column. I do
not therefore confine myself to the particular forms or dimensions in
the kilns herein shewn.
Having now described my Invention, and the methed I prefer to adopt
for carrying the same into effect, I wish it to be understood that I claim,
the general arrangement and construction of parts for limekilns fitted
with fire-places specially adapted for the generation of combustible
gases combined with air holes in the lower part of the kiln for the
admission of a supply of fresh air for the consumption of such gases.
I claim also heating the kiln by the combustion of the gases derived
from carbonaceous fuel and produced by the employment of a thick

page_text: And I also claim heating the kiln by the combustion of the gases
derived from passing steam through the ignited mass of fuel, whether in
special or ordinary fire-places, in the manner above set forth.
In witness whereof, I, the said Henry Young Darracott Scott,
have hereunto set my hand and seal, the Seventeenth day of
October, in the year of Our Lord One thousand eight hundred
and sixty-eight..