IMPROVEMENTS IN KILNS FOR BURNING PORTLAND CEMENT
Year: 1878

page_text: LETTERS PATENT to Charles Amand, of Boulevard de Strasbourg, No. 23, Paris,
Engineer, for the Invention of "IMPROVEMENTS IN KILNS FOR BURNING
PORTLAND CEMENT."
Sealed the 17th January 1879, and dated the 22nd July 1878.
PROVISIONAL SPECIFICATION left by the said Charles Amand at the Office
of the Commissioners of Patents on the 22nd July 1878.
CHARLES AMAND, of Boulevard de Strasbourg, No. 23, Paris, Engineer.
MENTS IN KILNS FOR BURNING PORTLAND CEMENT."
"IMPROVE-
The improvements characterizing my continuous kiln have for object the econo-
mical burning of Portland cement at a high temperature.
The burning of cement requires the temperature of welding heat, which is difficult
to obtain, as it also demands a perfect homogeneity in the degree of burning. This
result I easily obtain by the application of a thin layer of hot air at a pressure of a
quarter atmosphere to the flame at its exit from the furnace."
I will now describe the arrangement of my continuous kiln for burning Portland
cement.
In my system the beneficial effects are partly due to the fact that the products to.
be burnt are not in contact with the combustible or fuel.
My kiln is composed of a gallery of 15 metres in length by 3 meters in width in.
the interior. This gallery is built on arches to allow the atmospheric air to pass in
on all sides, to maintain a low temperature beneath the refractory body of the kiln,.
and to protect the metallic parts of the waggons from the heat. It should con-
stantly contain 5 waggons, each 3 metres in length, the tops of which form the sole
or bottom of the kiln.
For the burning of products other than cement it will be requisite to make the;
kiln 21 metres long instead of 15; the gallery will then contain 7 waggons; these.
waggons travel on iron rails supported by masonry; they are provided with refrac-
tory open-worked sides up to the height of the arch of the furnace, so that the
•

page_text: flame may penetrate to the centre of the products to be burnt when they arrive
opposite the furnaces, the open-worked sides also serving to prevent the falling of
the products against the walls of the gallery.
Two doors, one at each extremity of the gallery, open for the admittance and
exit of the waggons carrying the products to be burnt.
In the middle of the gallery at each side is a furnace surmounted by a surbased
arch (voute surbaissee).
The draught is effected through the mouth of the furnace, whence the heated
gases pass to the chimney by a special arrangement of flues.
A "recuperator" of heat, or heating chamber, placed upon the arch of the kiln
receives cold air from a small blowing machine, which is heated in the heating
chamber, acquiring a temperature of 400 to 500 degrees centigrade, and is projected
by a jet on to the flame at its exit from the furnace with a force about equal to the
initial pressure supplied by the blower.
Lastly. Two little openings are formed in the wall of the gallery at each side of
the furnaces, which may be plugged with clay; they serve to measure the tempera-
tun hu moang of a nerameter
When the kiln has been well dried four empty waggons and a fifth carrying the
products to be burnt (about 16,000 kilogrammes) are successively introduced by the
entrance door. The door is then closed, all the joints are luted, and heat is produced,
which is gradually augmented.
When the first charge is known to be well dried the doors are opened, and an
empty waggon is withdrawn at the exit door, whilst a fresh charge to be burnt is
introduced at the other end. The heat is then augmented to its maximum, and
when the calcination of the products previously dried is judged to be sufficient the
preceding operation is repeated, which brings them in front of the furnaces. At
this moment the products in front of the furnaces are calcined, and are about to be
burnt, the products on the waggon directly behind are dried and about to be calcined;
and, finally, those on the waggon just introduced into the kiln are still wet and are
about to be dried. To effect this the fire is urged, the flame burns the products
placed on the waggon immediately in front of the furnaces by passing through them,
and abandoning a great part of its caloric; the flame then encounters the products
on the waggon behind, effecting their calcination by penetrating through them, and
finishing its combustion.
After passing through this last mass the combustible gases are entirely burnt,
and there only remain the incombustible but heated gases, which dry the products
on the waggon nearest the entrance door by passing through them into the
chimney.
At the end of a certain time, which I estimate at 8 hours at the maximum, the
products facing the furnaces are completely burnt, and a fresh charge is introduced!
which forces the waggon on which they are placed into the farther end of the kiln,
which is not heated, where they gradually cool. This operation of the waggons iš
seen to be very simple, and may be accelerated by giving an incline to the rails
of 1 centimetre in a metre, and placing a winch at the exit door for the withdrawal
of the waggons.
The cement should be moulded into little bricks to obtain the good result; they
are piled better on the waggons, leaving the necessary space between them for the
flame to penetrate in a uniform manner.
In consequence of the arrangement of my kiln, and the manner in which the
products to be burnt, moulded into bricks, may be distributed in it, the flame will
completely embrace the latter; the exact temperature which the burning of Portland
cement requires will thus be given to it, and may be ascertained by the pyrometer,
and the furnace regulated accordingly.
The time necessary for the burning of a charge is 8 hours, because the kiln having

page_text: three compartments; the mass to be burnt passing successively through each of
these will be,-
1st. Exposed during 8 hours to a temperature of about 400 degrees for
drying.
2ndly. Exposed during 8 hours at a red-heat temperature for calcination.
3rdly. Exposed during 8 hours at a white-heat temperature for burning.
It will be seen that a burning operation may be effected in 8 hours, since in
reality each mass to be burnt is exposed to the heat during 24 hours.
In kilns where the mass is mixed with the combustible by alternate layers the
burning of Portland cement lasts sometimes 48 hours before it is complete, but it is
to be remarked that this burning is only effected from the bottom to the top of the
kiln successively; therefore, if the draught is at all impeded, the delay which it will
suffer may be easily understood.
In my kiln, on the contrary, the temperature is always uniform, excepting at the
moment of charging and withdrawal, when the kiln remains open during 3 or 4
minutes; but this short cooling does not cause any harm, since the charges in the
kiln are advanced into the next compartment.
.
The dimensions of my kiln are calculated so as to give 10 tons of burnt cement
at each charge, and I estimate to be able to make an operation every 8 hours, being
30 tons of cement in 24 hours.
It is even probable that 4 or 5 withdrawing operations may be made in one day,
thus obtaining from 40 to 50 tons of burnt cement in 24 hours, but if only 30 tons.
are reckoned upon a very low cost price will be obtained, because in addition to the
advantages of a continuous burning there would be a great economy of fuel by the
application of hot air to the flame at its exit from the furnaces.
The hot air projected on to the flame at a certain pressure will moreover have the
great advantage of forcing the flame to penetrate first the lower part of the mass
to be burnt, so that it is as thoroughly burnt as the upper part. This hot air is
projected in a thin sheet on to the flame when the latter has passed the surbased
arch which separates the kiln from the furnace, and is applied over the whole width
of the furnace, so that all the flame receives it.
In every case of heating by means of a flame a juxtaposition of the combustible
gases and the air is produced, and not a thorough mixture or mingling. The result
is that a considerable part of the combustible escapes without being burnt; this is
the phenonomen which is called the "parallelism of layers of gas." This I avoid
by mingling the flames together in their course by means of the current or sheet of
hot air.
By my system the cost price of the burning of a ton of cement would be from
3 francs 50 centimes to 4 francs, according to the price of the fuel and labour in the
different localities in which my kiln may be erected, whereas with the ordinary
kiln hitherto employed this price would amount to about 15 francs.
My kiln is adapted to the burning of Portland and other analogous cement.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Charles Amand in the Great Seal Patent Office on the 22nd January
1879.
CHARLES AMAND, of Boulevard de Strasbourg, No. 23, Paris, Engineer. " IMPROVE-
MENTS IN KILNS FOR BURNING PORTLAND CEMENT."
The improvements characterizing my continuous kiln have for object the econo-
mical burning of Portland cement at a high temperature.
The burning of cement requires the temperature of welding heat, which is difficult
to obtain, as it also demands a perfect homogeneity in the degree of burning. This

page_text: result I easily obtain by the application of a thin layer of hot air at a pressure of a
quarter atmosphere to the flame at its exit from the furnace.
I will now describe the arrangement of my continuous kiln for burning Portland
cement.
In my system the beneficial effects are partly due to the fact that the products to
be burnt are not in contact with the combustible or fuel.
My kiln is shown, in longitudinal section, Figure 1; transverse section through
M, N, Figure 2; transverse section through P, Q, Figure 3; and in horizontal
section, Figure 4.
It is composed of a gallery or long chamber A (preferably) of 15 metres in length ]
by 3 metres in width in the interior. This gallery or chamber is built on arches B
to allow the atmospheric air to pass in on all sides to maintain a low temperature
under the refractory bottom or sole C of the kiln, and to protect the metallic parts
of the waggons from the heat. It should constantly contain 5 waggons or trucks
D, each 3 metres in length, the floors of which form the sole or bottom C of the
kiln.
These trucks or waggons travel on iron rails f, supported by masonry; they are
provided with refractory open-worked sides a up to the height of the furnace arch,
so that the flame may penetrate to the centre of the products to be burnt when they
arrive opposite the fires or furnaces, the open-worked sides also serving to prevent
the falling of the products against the walls of the gallery.
Two doors E, one at each end of the gallery, open for the admittance and exit of
the waggons D, carrying the products to be burnt.
In the middle of the chamber or gallery at each side is a fire or furnace hearth F,.
2 metres 50 centimetres wide, surmounted by a surbased arch.
The draught of the kiln is effected through the entrance, whence the heated gases
pass to the chimney G by a special arrangement of flues.
A "recuperator" of heat or heating chamber H, placed upon the arch above the
kiln, receives cold air from a small blowing machine; this cold air is heated in the
heating chamber, acquiring a temperature of 400 to 500 degrees centigrade, and is
projected or thrown on to the flame (in the direction of the arrows) as it leaves the
fire or furnace with a pressure about equal to the initial pressure supplied by the
blower.
The "recuperator" or heating chamber may be (as in Figure 5) a simple tube t
with two branches t¹ embedded in sand arranged above the arch.
Lastly. Two little openings o are formed in the wall of the gallery of the kiln at
each side of the fires or furnaces, which may be plugged with clay; they serve to
measure the temperature by means of a "Wedgood" or other suitable pyrometer.
When the kiln has been well dried 4 empty waggons and a fifth carrying the
products to be burnt (about 16,000 kilogrammes) are successively introduced by
the entrance door. The door is then closed, all the joints are luted, and heat is
introduced, which is gradually augmented.
When the first charge is known to be sufficiently dried the doors are opened, and
an empty waggon is withdrawn at the exit door, whilst a fresh charge to be burnt
is introduced at the other end. The heat is then augmented to its maximuin, and
when the calcination of the products previously dried is judged to be sufficient the
preceding operation is repeated, which brings them in front of the furnaces. At
this moment the products on the truck or waggon in front of the fires or furnaces
are calcined and are about to be burnt, the products on the waggon directly behind
are dried and about to be calcined, and finally those on the waggon just introduced
into the kiln are still wet and are about to be dried. To effect this the fire is urged,
the flame burns the products placed on the waggon immediately in front of the
furnace by passing through them, and abandoning a great part of its caloric; the

page_text: flame then encounters the products on the waggon behind, effecting their calcination
by penetrating through them and finishing its combustion.
After passing through this last mass the combustible gases are entirely burnt,
and there only remain the uncombustible but heated gases, which dry the last
products on the waggon nearest the entrance door by passing through them into the
chimney.
At the end of a certain time, which I estimate at 8 hours at the maximum, the
products on the waggon facing the furnaces are completely burnt, and a fresh charge
is introduced, which forces the waggon on which they are placed into the farther
end of the kiln, which is not heated, where they gradually cool up to the time they
are withdrawn from the kiln. This operation of the waggons is seen to be most
simple.
In consequence of the arrangement of my kiln, and the manner in which the
products to be burned moulded into bricks may be distributed in it, the flame-will
completely embrace the latter; the exact temperature which the burning of Port-
land cement requires will thus be given to it, and may be ascertained by the
pyrometer, and the furnace regulated accordingly.
The time necessary for the burning of a charge is 8 hours, because the kiln having.
three compartments, each mass or batch of products to be burnt passing successively
through each of these will be,-
First. Exposed during 8 hours in the first compartment to a temperature of from
300 to 400 degrees centigrade.
--
Secondly. Exposed during 8 hours in the middle compartment to a red-heat
temperature for calcination.
Thirdly. Exposed during 8 hours in the last compartment to a white-heat tem-
perature where the burning is effected.
It will be seen that a burning operation may be effected in 8 hours, since in
reality each mass to be burnt is exposed to the heat during 24 hours.
In kilns where the mass to be burnt is mixed with the combustible by alternate
layers the burning of Portland cement lasts sometimes 48 hours before it is complete,
but it is to be remarked that this burning is only effected from the bottom to the
top of the kiln successively; therefore if the draught is at all impeded the delay
which the burning will suffer may be easily understood.
In my kiln on the contrary the temperature is always uniform, excepting during
the short space of time the kiln is required to be open for the purpose of introducing
and withdrawing a waggon, but this short cooling does not cause any harm since
the two charges in the kiln are advanced into the next compartment.
The dimensions of my kiln are calculated so as to give 10 tons of burnt cement
at each charge, and I estimate to be able to complete an operation every 8 hours,
being 30 tons of cement in 24 hours. This amount of 30 tons of produce in 24 hours
is only a minimum amount.
In the kilns before mentioned, where the burning is effected in alternate layers
of produce and combustible or fuel, the burning sometimes takes 48 hours, but when
there is a good draught it takes but 24 hours. Now as in these kilns the burning
is propagated by alternate layers from the bottom to the top of the kiln, it would
not be completed in 24 hours if each layer had to be kept for 8 hours at a white-
heat temperature.
Another fact in support of what has just been said is that the burning of cement
is not effected at a temperature lower than 1500 degrees centigrade. Now in the kilns
on the "layer" system, although the layers of combustible or fuel are very thick, they
would not be thick enough to give a temperature of 1500 degrees during 8 hours,
and as the burning is complete, it is evident that it is effected in less than
8 hours.
My continuous kiln therefore permits 4 to 5 withdrawals from the kiln in a day,
and of obtaining from 40 to 50 tons of burnt cement in 24 hours; but by only
allowing for 30 tons the cost price of the burning will be very low, since in addition
to all the advantages of a continuous burning there is also a great economy in fuel

page_text: or combustible by causing hot air to act on the flame at its exit from the furnace ;
the flame will thereby be forced to first penetrate the lower part of the mass to be
burnt, so that this lower portion will be as efficiently burnt as the upper portion.
To effect this result I cause jets of hot or heated air to be thrown (as shown in
the Drawing) on to the flame when it has passed through the arch which separates
the furnace from the hearth; this hot air is thrown over the whole width of the
hearth so that it acts on all the flame.
The economy of fuel obtained by the employment of compressed hot air is con-
siderable, because in all cases of heating by means of a flame a juxtaposition of
combustible gases and air is produced in the current, not a thorough mixture or
compound. The result is that a considerable portion of combustible gases escape
without being burnt; this is the phenomonen called "the parallelism of layers of
gas."
It is the chief cause of the great expenditure of fuel, because in consequence
of this "parallelism" the quantity of air being in a manner insufficient for the
proper combustion of the bicarburet of hydrogen, which chiefly composes the flames,
this bicarburet decomposes into protocarburet which is burnt and into carbon,
which forms nearly the whole of the black smoke which is seen at the chimney.
I avoid this "parallelism" by mixing jets of hot air with the flames in their course.
The air, heated to from 400 to 500 degrees, ignites the particles and the carbon
vapour, which being thus, as are also the combustible gases intimately mixed with
air, are almost completely burnt.
By my system the maximum cost price of the burning of a ton of cement would
be from 3 francs 50 centimes to 4 francs, according to the price of fuel and labour
in the different localities in which my kilns may be erected, whereas with the
ordinary kilns hitherto employed the cost price is about 15 francs.
And 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 improved arrangement of an economical high-temperature continuous kiln
for burning Portland and other analogous cements, as described and shown.
Secondly. I claim specially the arrangement of the kiln with a layer or jets of air
thrown or projected by pressure in a thin sheet on to the flame in the hearth,
forcing the flame to penetrate all the parts of the mass to be burnt, as herein-before
described.
In witness whereof, I, the said Charles Amand, have hereunto set my hand and
seal, this Eleventh day of January, One thousand eight hundred and seventy-
Witness,
J. ARMENGAUD, jeune,
Of Paris,
Bd. de Strasbourg, 23,
Civil Engineer.
CHARLES AMAND. (L.S.