AN IMPROVED SYSTEM OR METHOD OF AND APPARATUS FOR EFFECTING THE COMBUSTION OF FUEL FOR THE MORE PERFECT UTILIZATION THEREOF
Year: 1868

page_text: LETTERS PATENT to Arnould Eugéne Georges Thenard, of No. 6,
Place St. Sulpice, Paris, but at present residing at Provence Hotel,
Leicester Square, in the County of Middlesex, for the Invention.
of "AN IMPROVED SYSTEM OR METHOD OF AND APPARATUS FOR EFFECTING
THE COMBUSTION OF FUEL FOR THE MORE PERFECT UTILIZATION THEREOF."
Sealed the 8th December 1868, and dated the 11th June 1868.
PROVISIONAL SPECIFICATION left by the said Arnould Eugénet
Georges Thenard at the Office of the Commissioners of Patents,
with his Petition, on the 11th June 1868:
I, ARNOULD EUGENE GEORGES THENARD, of No. 6, Place St. Sulpice,
Paris, but at present residing at Provence Hotel, Leicester Square, in
the County of Middlesex, do hereby declare the nature of the said.
Invention for "AN IMPROVED SYSTEM OR METHOD OF AND APPARATUS FOR

page_text: EFFECTING THE COMBUSTION OF FUEL POR THE MORE PERFECT UTILIZATION
THEREOF," to be as follows:-
The economization of fuel and the production of the highest tem-
peratures therefrom are two of the most important problems of the
present day.
In the method of effecting the combustion of fuel which constitutes
my present Invention, owing to the almost mathematical precision with
which the combustion takes place, the two problems above mentioned
are in my opinion solved in a more perfect manner than by any system
heretofore employed, although based upon principles more or less known
and applied, but which have never been studied, understood, and more
particularly combined so perfectly as they have been by me.
Before entering into the details of my Invention, I will give a
summary of the general principles involved therein.
In the combustion of fuel there are two distinct processes carried on,
by each of which heat is developed; by the first fuel is transformed
.into combustible gases, and by the second the gases thus formed in their
turn undergo combustion.
The conversion of solid fuel by means of atmospheric air and heat
into a combustible gas presents no serious difficulty, it is only necessary
for this purpose to send a limited quantity of air through a sufficiently
thick layer of incandescent fuel; but the perfect combustion of the
gases so produced is a more difficult matter. It is a very delicate
operation, requiring a high degree of precision, which has never yet
been perfectly attained, but which I believe I have approached nearer
than has been done before.
The characteristic sign of perfect combustion, producing the maximum
useful effect united with the maximum intensity of heat is the absolute
neutrality of the flame produced, that is, the total absence in the same
of both combustible gas and oxygen, and it is therefore the attainment
of such neutral flame that must be sought for in solving the problem of
perfect combustion. For this purpose it is necessary during the whole
process of combustion, no matter how long it may last, that the com-
bustible gases produced by previous partial combustion of solid fuel be
.constant in both quantity and quality, as must also be the supply of
air to effect their combustion, or that if the one vary the other shall
at the same time vary in the requisite proportion for restoring the

page_text: equilibrium. This is the first problem to be solved. It is necessary.
also that the decrease of affinity that active or combustible gases. are
subject to owing to the presence of inert or non-combustible gases
(which are necessarily mixed with them in continually increasing pro--
portion owing to the combustion of the active gases) be not too great,"
or rather that it be compensated for by another force which obliges
them to enter into combination, or in other words, to burn until no
trace of them is left. This is the second and last problem to be
solved..
The Production of Combustible Gases.-When coke or very dry charcoal
is burnt in a furnace in a sufficiently thick layer, and by the agency of a.
limited quantity of air, a mixture of carbonic oxide and nitrogen gases
is produced in the proportion of about one volume of the former to two
volumes of the latter. In this case therefore the first problem is solved
as far as regards the composition of the combustible gases, but not as
regards their volume. But this is not the case when coal, peat, or
wood is employed in place of charcoal or coke; in such case these
gases become mixed in very unequal proportions with the product of.
distillation, which at every moment alter the composition of the com-:
bustible gases. It is therefore necessary in the case of coal to seck for
means to insure regularity in the composition of the products. of the
preliminary combustion. For this purpose I have recourse to the system.
of combustion "per decensum' as employed in certain description of
furnaces used in the manufacture of ceramic ware, and known as.
"Alandier's," that is to say, I cause the air required for the proliminary.
combustion to enter from above and to descend through a deep layer.
of fuel ignited at the bottom, so that the combustible gases produced
issue at the bottom of the layer of fuel. Under these conditions, as the
combustion does not rise above a certain level, below which all fuel is
in a state of combustion, while above such level all the fuel is in an.
unconverted state, a true equilibrium is established so long as there
exists unconverted fuel, whereby products are obtained that are uniform
both in quantity and quality for one and the same influx of air. This
is one of the fundamental principles of my new system.
33
Regulation of the Air-The next question to be determined is how
to obtain a regular influx of air required for the above purpose. In
ordinary furnaces the air enters, at one place only, namely, the grate,..
but in furnaces constructed according to my Invention the air enters. at.

page_text: two points, the orifices at each of which are specially adapted to the
particular functions which they have to fulfil.
Regulation of the Air for the Preliminary Combustion.-Owing to the
accumulation of ashes, and more particularly to the variations in the
dimensions and direction of the crevices in the fuel through which the
air has to pass, it meets with continually varying resistances, which
render its volume so inconstant that the figure representing the extreme
differences is a fraction greater than that which represents the force
that propels or draws the air into the furnace. It is impossible to do
away entirely with these differences, but they may easily be diminished
to such a degree as to render their influence inappreciable. It is only
requisite for this purpose to introduce the air under a certain pressure,
which I effect by employing in place of a chimney draught or apparatus
producing a weak blast blowing machines and other similar apparatus.
capable of producing powerful blasts or draughts. If, however, such a
blast or draught of increased pressure be necessary to insure perfect com-
bustion, yet the ordinary chimney draught or a blast or draught produced
by a fan or steam jet will give a sufficiently good effect to render them
applicable with advantage in some cases, more particularly where a
less intense heat is required, as for steam boilers.
The Final Combustion.-There are three conditions which tend to
assist the final combustion; first, the decrease of inertia of the com-
bustible gases; secondly, the elevation of the temperature of the gases
present; third, the intimate and rapid intermixture of the combustible
gases and the ignited gases in a medium favourable to combustion.
The apparatus I employ in carrying my Invention into practice fulfils
each of these conditions, at least as perfectly and under certain circum-
stances better than has been done by previous arrangements.
Inertia of the Combustible Gases.-Coke and charcoal produce the
most inert gases; their inertia is such that in order to compensate for
it recourse is had continually to the old expedient of injecting steam
into the ignited fuel. When coal is burnt by an ascending draught of
air after the first rich hydrocarbon gases have been distilled off, which
takes place rapidly, the coke gases are evolved, that is, the most inert
gases, which continue to be developed during the greater part of the
time that the combustion takes place. On the contrary, by combustion
"per decensum," although during the first period more of the volatile
products are destroyed than in the other case, yet as they are far from

page_text: being all destroyed and as they are generated with regularity the gases
never attain the excessive poverty mentioned above, and by the
assistance of the other means the combustion is always sufficiently easy
and perfect as not to require the injection of steam. Consequently,
for the combustion of coal and with respect to the lowest degree of
inertia in the combustible gases, my apparatus is superior to those in
which the preliminary combustion takes place by ascending draught,
and these are the most numerous.
The Temperature of the Gases.-In order for a combustible gaseous
mixture to burn it must be first of all raised to the temperature at
which it is to be consumed, and this temperature must be increased in
proportion to the inertia of the mixture. According to this datum the
preliminary superheating of the air, and, if necessary, of the combustible
gases, by the help of the waste flames has the treble advantage of
regaining part of the waste heat, of producing a higher temperature, and
of facilitating the final combustion. I heat the air when waste heat is
produced by any of the ordinary methods, but I do this rather for the
sake of retaining part of the heat produced by the burnt gases than for
the purpose of facilitating combustion, for by my improved system the
gases are rendered sufficiently combustible to burn almost instantly and
completely with cold air. This is an invaluable advantage, as it
permits the adoption of my apparatus with the greatest success in
operations in which the heat is in a great measure absorbed, and
consequently where little or no waste heat is produced, as in heating
boilers of all descriptions.
The Intimate Mixture of the Combustible and Burning Gases.-There
are few apparatus in which this important point has been duly con-
sidered, and this constitutes the greatest defect of the apparatus known
as "Alandier's," which my method has so far resembled in many
respects, but from which it will now differ considerably. For a chemical
reaction to take place the reagents must first of all be in perfect
contact, whence the necessity of the close and rapid intermixture of the
gases to be burnt with air. This does not occur in the before-mentioned
furnaces known as "Alandier's," but it is accomplished to a high degree
of perfection in my apperatus. In an "Alandier" the combustible
gases and the air, on account of their widely different degrees of density
and of their mode of coming together, remain relatively speaking a long
time in stratified layers, like oil or rather alcohol on water, the water

page_text: representing the air, the alcohol the combustible gases. In my system
nothing of the kind takes place; in fact, the air instead of coming in
slowly and following the direction of the combustible gases rushes
violently against them as they issue from the solid fuel, and by being
made to whirl round with them in a confined space, close intermixture
suddenly takes place in contact with the burning coal, which in
exercising on it a rapid catalytic action by raising the temperature
partly contributes towards rendering combustion instantaneous and
tolerably complete, so that with cold air the gases burnt usually contain
no more than 1 per cent. of oxygen and 2 per cent. of carbonic oxide,
while with air raised to red heat there remain neither oxygen nor
combustible gases in excess. This is the second and last fundamental
point on which is based my method of combustion, and consequently
the apparatus by which it is realized, a description of which is given
below.
Various arrangements of apparatus may be employed for carrying my
above-described method of combustion into practice. Thus in one
arrangement I construct a chamber of fire-brick of the form of a
truncated conc, which is filled with fuel from the top, and below which
is a second chamber, which I will term the "melting chamber,"
separated from the upper one by a fire-brick arch. When the apparatus
is employed for steam boilers or for heating liquids this melting
chamber constitutes the furnace of the boiler. Immediately above the
melting chamber is placed a blast pipe of triangular section, surrounded
by burning fuel, through which pipe the air for the combustion of the
gases is introduced, which air in escaping therefrom through two side
apertures, mixes with the combustible gases in whirling round with the
same over the burning fuel near the said openings. The flame produced
by this perfect combustion passes through flues or openings into the
melting chamber below. The upper chamber is filled with fuel through
an opening at top, closed by a cover fitted into an annular trough, and
provided with a clay or sand lute. The ashes as they accumulate in the
bottom of the upper chamber are removed through two side openings
closed with luted plugs. The air required for the preliminary com-
bustion is introduced through a blast pipe situated in the top of the
upper chamber, and communicating with the blowing apparatus, while a
branch from this pipe conducts the air into the before-mentioned
triangular pipe below, serving for the final combustion. An opening is.

page_text: formed in the melting chamber for working the materials contained
therein, which opening is provided with a sliding door. In connection
with the furnace is an apparatus for superheating the air by means of the
waste heat of the gases. The sole of the upper chamber inclines towards
the side openings for removing the slag, while the under surface of the
sole constituting the roof of the melting chamber is made of a parabolic
form, so as to concentrate the heat on the sole of this chamber. In the
melting chamber may be carried on any processes that are conducted in
ordinary furnaces, such as the manufacture of iron, glass, pottery,
roasting ores, smelting copper, bronze, lead, and other operations. Also
the flames may be conducted from such chamber into the flues of steam
boilers, the melting chamber serving generally in place of the ordinary
boiler or other furnace.
In another arrangement of the apparatus the melting chamber is
placed at the side of the fuel chamber, which is constructed in the same
manner as above described, and which communicates with the melting
chamber by means of a lateral opening, on each side of which is the
blast pipe through which the air enters for supporting the complete
combustion, so that the combustible gases generated in the fuel chamber
in passing through the lateral opening become intimately mixed with the
jets of air entering through the blast pipe, which effects their complete
combustion, and the resulting intensely heated flame then passes
through the side aperture into the melting chamber; this is, as before,
provided with lateral openings for working the materials contained
therein; an apparatus is also applied for superheating the air required
for combustion, as in the previous arrangement.