Improved Method and Apparatus more especially intended for Manufacturing Calcium Carbide, and for the Reduction of Metals from their Oxides.
Year: 1896

page_text: Date of Application, 13th Nov., 1896
Complete Specification Left, 11th Sept., 1897-Accepted, 16th Oct., 1897
PROVISIONAL DIECIFICATION
An Improved Method and Apparatus more especially intended for
Manufacturing Calcium Carbide, and for the Reduction of Metals
from their Oxides.
I, HUDSON MAXIM, of Thurlow Lodge, 377 Norwood Road, London, S.E., Chemist
and Mechanical Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention relates to an improved method and apparatus more especially
intended for manufacturing calcium carbide and for the reduction of metals from
their oxides.
According to my improved method I am able to employ an inexpensive and
economical apparatus for the utilisation of an electric current or electrical heat
energy for the purposes above stated, and to employ in conjunction therewith, the
heat of combustion in as intense a form as possible, and to subject to such heat the
materials to be treated, either preliminarily to, or in conjunction with, the subjecting
of the materials to the electrical heat energy, or to the electric current.
I also provide means for the ready establishment of an electric circnit through
the materials to be treated, whereby the said materials may be reduced by the heat
of incandescence, and I further provide means for readily removing the carbide or
other product forined by the heat, and for supplying fresh material to fill its place
to be in turn converted or reduced.
In carrying out the invention, means are provided for establishing contact between
an electric heating conductor and a source of electrical energy by means of a
sliding contact. For a heating conductor, a thin filament sheet, or rod of carbon,
is preferably, employed. The carbon rod or heating conductor, in entering, or being
made to pass through, the material, is also made to pass along and bear upon a
conducting surface, from which it receives its supply of electrical energy. This
may be effected by sliding the heating conductor upon or between a carbon surface
or surfaces in such wise as to establish and maintain as perfect contact as possible.
Whereas a heating conductor is destroyed or consuined as a rule, or is removed with
the product formed, and its place must be readily supplied with a fresh conductor,
this according to my invention is easily effected by causing a new portion of the
conductor to enter the material, by merely sliding it along in contact with the
conducting surface from which it receives its electrical supply.
The preferable method of forming electrical contact with a heating conductor is
to provide a contact surface of broken, disintegrated, or powdered material, prefer-
ably carbon, or other refractory conducting material, and the preferable method of
maintaining the electric contact with the disintegrated or powdered surface is to
pass the heating conductor through a body of disintegrated or powdered conducting
material, and to press the said material upon the conductor, or to subject such
material to pressure in a direction at right angles to the longitudinal axis of the
heating conductor. This may be effected in a very simple manner by filling a hollow
cylinder of suitable material, such as graphite, or a fire-clay pipe, or a metallic
cylinder, such as iron, with powdered carbon, or other refractory conducting material,

page_text: which will not be destroyed by the heat of the heating conductor. The pipe is
transversely perforated, that is to say, openings are made in the pipe in order to
permit the carbon rods or heating conductors to be passed freely through the pipe
in a direction at right angles to its longitudinal axis. The pipe with the contained
powdered material serves as a conductor or electrical carrier to supply the heating
conductor with electrical energy.
Any suitable number of transverse openings may be formed through the pipe, in
order to admit of the passage of several heating conductors, and two such pipes so
constructed may be arranged in a position parallel to each other, and the inter-
vening space be filled with the material to be treated, and the heating conductor or
conductors be passed through the material, thereby formning contact between the two
cylinders and the conducting material they contain. The cylinders are each,
preferably, provided with a screw or other ineans for subjecting the conducting
material contained in them to pressure, in order to maintain efficient electrical
contact between the contained material and the heating conductor or conductors.
By the method last above mentioned, and by such an apparatus, a bed of carbide
forming material may be acted upon by one or several licating conductors simul-
taneously, and the carbide removed as fast as it is formed, by simply withdrawing
it by means of a hook or tongs or grapple, or other suitable incans, without
disturbing other portions of the bed of material under conversion or treatment.
The bed of carbide forming material may be readily replenished and supplied by
shovelling fresh inaterial upon it.
After the removal of a body of carbide, and the filling of the space occupied by
it with fresh material, the old heating conductor may be replaced by a new one
which is passed transversely through one of the aforesaid conducting cylinders and
contained conducting material, to and in contact with the opposite conducting
cylinder and contained conducting material, and also through the intervening carbide
forming material. The electric current will preferably be allowed to pass continually,
by one or more heating conductors, through the carbide forming material, the
current being broken only at points when and where a portion of the carbide is
removed when formed. This prevents undue fluctuations of the current, and also
obviates the necessity of any resistance regulator, so that the maximum heating
energy of the electric current, is utilised for the formation of the carbide..
So simple and efficient is this method that a single operator is sufficient to attend
to an apparatus employing several thousand electrical horse-power.
When employing the heat of combustion preliminarily to, or in conjunction with
the heat of the electric current, I preferably proceed as follows:-I separately and
simultaneously raise a suitable fuel and atmospheric air to a high temperature by
passing them through suitable conduits which are highly heated externally. I
may employ coal dust as a fuel, but I prefer to employ water gas or other suitable
gaseous fuel. When I have raised the separate currents of air and water gas to a
very high temperature, and as high as can be obtained by the heat of ordinary
combustion, portions of the highly heated air and water gas are burned in another
apparatus or furnace through which the remaining portions of the highly heated air
and water gas are made to pass, in order that they may be very highly superheated.
Then the highly superheated air and water gas are thence conducted into and burned
within another apparatus or furnace within which the carbide forming material is
placed and subjected to the heat energy of the combustion of the highly superheated
air and water gas.
Oxygen combining with hydrogen, as in the oxy-hydrogen blow-pipe, will produce
a temperature of, say, 5,000 degrees Fahr. This is due to the very large quantity
of heat evolved by the combustion of hydrogen with oxygen, and while hydrogen
will produce 62,000 British ther.nal units per pound in combustion with oxygen,
one pound of carbon will evolve only about 17,000 such heat units. Nevertheless,
carbon is capable of combining with oxygen to produce heat, even at temperatures
above which hydrogen will not combine with oxygen, that is to say, at temperatures
at which hydrogen and oxygen are entirely dissociated. Therefore, if carbon or a

page_text: body rich in carbon, such as water gas, be preliminarily heated, at a temperature
approximating that of the oxy-hydrogen flaine, then a higher temperature may be
obtained by the combustion of water gas with oxygen, than can be obtained by the
combustion of hydrogen alone with oxygen.
So intense a heat may be obtained in the manner above described, that the lime
of the carbide forming material may be fused, and then, when fused, and while in a
fused state, be subjected to electrical influence, or to the heating effect of an
electric current passed through it, either by the resistance offered by the fused
material itself, or by means of a heating conductor passed through it in the manner
herein before stated.
The lime of the carbide forming material may be fused in the presence of the
carbon, without forming carbide, but by the method above stated I consider that a
temperature above the fusing point of lime will be obtained, which is necessary to
the production of carbide, and then an electric current may be passed through the
fused material simply to facilitate the reaction required for the formation of
carbide.
3
1000
An Improved Method and Apparatus more especially intended for
Manufacturing Calcium Carbide, an for the Reduction of Metals
from their Oxides.
I, HUDSON MAXIM, of Thurlow Lodge, 377, Norwood Road, London, S.E., Chemist
and Mechanical Engineer, do hereby declare the nature of this inveation 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 an improved method and apparatus more especially
intended for manufacturing calcium carbide, and for the reduction of metals from their.
oxides.
According to my improved method I am enabled to employ an inexpensive and
economical apparatus for the utilisation of an electric current or electrical heat energy
for the purposes above stated, and I am also enabled to subject the materials to be
treated to the heat of combustion in as intense a form as practicable, either
preliminarily to, or in conjunction with, the subjecting of the said materials to the.
electrical heat energy, or to the electric current.
I also provide means for the ready establishment of an electric circuit through the
materials to be treated, whereby the said materials may be reduced by the heat of
incandescence, and I further provide means for readily removing the carbide or other
product formned by the heat, and for supplying fresh material to fill its place to be in
turn converted or reduced.
In carrying out the said invention, means are provided for establishing contact
between an electric incandescence heating conductor and a source of electrical energy
by means of a sliding contact. For a heating conductor, a thin filament, sheet, or
rod of carbon is preferably employed. This carbon rod or heating conductor, in
entering, or being made to pass through, the material, is also made to pass along and
hear upon a conducting surface, from which it receives its supply of electrical energy.
This may be effected by sliding the heating conductor upon or between a carbon
surface or surfaces in such wise as to establish and maintain as perfect contact as

page_text: practicable. As a heating conductor is destroyed or consumed as a rule, or is removed
with the product formed, its place must be supplied with a fresh conductor; this
according to my invention is easily effected by causing a new conductor or a new
portion of the conductor to enter or pass through the material, by merely sliding it
along in contact with the conducting surface from which it receives its electrical
supply.
The preferable method of forming electrical contact with the heating conductor is
to provide a contact surface of broken, disintegrated, or powdered material, preferably
carbon, or other refractory conducting material; and the preferable method of main-
taining the electric contact with the disintegrated or powdered surface is to pass the
heating conductor through a body of disintegrated or powdered conducting inaterial,
and to press the said material forcibly against the conductor, or to subject such
material to pressure in a direction at right angles to the longitudinal axis of the
heating conductor. This may be effected in a very simple manner by filling a hollow
cylinder, trough or receptacle of suitable material, such as graphite, or a fire-clay pipe,
or a metallic cylinder, such as iron, with powdered carhon, or other refractory
conducting material, which will not be destroyed by the heat of the heating conductor.
The said pipe, trough or other receptacle is perforated, that is to say, openings are
made in the same to permit the carbon rods or heating conductors to be passed freely
through it in a direction at right angles to the longitudinal axis of the chamber for
containing the materials to be treated. The said pipe, trough or receptacle with the
contained powdered material serves as an electrode or electrical carrier to supply the
heating conductor with electrical energy.
My said invention, moreover, comprises other improvements hereinafter described.
In the accompanying drawings
Figure 1 is a vertical central section of a portion of one form of my electric furnace
for the production of calcium carbide.
Figure 2 is a horizontal section illustrating another form or modification thereof.
Figure 3 is a horizontal section illustrating a further modification thereof, one of
the electrodes or terminals being shown in plan.
The remaining figures of the drawings are hereinafter referred to.
indicates the electric incandescence heating conductor; b, b are the receptacles
for the pulverulent carbon or other suitable conducting material, which, in
Figures 1, 2 and 3, are shown as metallic tubos or cylinders. In the arrangement
shown in Figure 1, two of these cylinders b are fixed opposite each other in the sides
of the furnace F, and are connected respectively by suitable conductors with the two
poles of a source of electrical energy. The inner end of each tube or cylinder b is
closed by a slab or block c of carbon or other suitable material, provided with a
central hole through which the conductor a is thrust. In the outer end of each tube
or receptacle b is screwed a gland d the interior whereof is made conical so that,
when it is screwed in, it will compress the mass e of powder or the like in the said
tube or receptacle and thus maintain the said powder or the like in close contact with
the conductor a, whilst permitting the said conductor to be pushed through from
time to time as it is consumed.
The carbide-forming materials are fed into the furnace F and are treated therein as
hereinafter described. To permit the discharge of the carbide produced, without
interrupting the process, the furnace F is provided at the bottom with a sliding
door f.
In the arrangement shown in Figure 2. granulated carbon or the like is introduced
into two tubular receptacles or electrodes band is compressed therein by means of
plungers g worked by screw-threaded rods g¹; and an electric incandescence
heating conductor is passed through a hole F¹ in the furnace F and through one mass
of granulated carbon or the like and into the other.
In the modification of my electric furnace shown in Figure 3, a single heating
conductor a is passed through two tubular receptacles or electrodes b fixed in opposite
ides of the furnace F; and the mass e of powdered carbon or the like is compressed
round the said conductor by means of conical plungers g worked by hollow screw-

page_text: threaded rods g, through which rods the said conductor a is also passed. When the
part of the said conductor heated to incandescence is consumed, the said conductor
can be easily renewed without detaching any of the part of the apparatus, the pressure
on the powdered material e being, relieved if necessary to permit the introduction
of a fresh rod, and being then again applied.
Any suitable number of transverse openings may be formed through a pipe,
trough or receptacle containing pulverulent or granular conducting material for
the purpose above specified, in order to admit of the passage of several heating
conductors. I sometimes arrange two pipes, troughs or receptacles so constructed,
in a position parallel to each other, and fill the intervening space with the material
to be treated, so that the heating conductors pass through the material, thereby
forming contact between the two pipes, troughs or receptacles and the conducting
material which they contain. The said pipes, troughs or receptacles are each,
preferably, provided with one or more screws, weights or other suitable means for -
subjecting the conducting material contained in them to pressure, in order to main-
tain efficient electrical contact between the contained material and the heating
conductor or conductors.
In Figures 4 and 5, I have shown an arrangement of this kind, Figure 4 being a
plan partly in horizontal section, and Figure 5 an end view partly in transverse
section. In the furnace F, a chamber G for the carbide-forming material is provided
by fixing in the said furnace at a suitable distance apart vertical walls which extend.
from end to end of the said furnace, and form, with the side walls of the furnace,
troughs or receptacles for the powdered carbon or other conducting material.e. These
walls are transversely perforated to permit the passage through them of electric
incandescence heating conductors a, of which any desired number may be employed.
These conductors are introduced through holes in one side wall of the furnace and are
passed through the said furnace and through the chamber G and into or through
holes in the other side wall of the furnace. The requisite pressure is applied to the
powdered carbon or the like by means of weights j, Figure 5, which serve as electrodes
or terminals; or other devices for this purpose, such, for instance, as those shown in
Figures 1, 2 and 3 may be used.
By the method last above described, and by such an apparatus, a bed of carbide-
forming material may be acted upon by several heating conductors simultaneously,
and the carbide removed as fast as it is forined, by simply withdrawing it by means
of a hook or tongs or grapple, or other suitable means, without disturbing other
portions of the bed of material under conversion or treatment. The bed of carbide-
forming material may be readily replenished and supplied by shovelling fresh
material upon it. After the removal of a body of the carbide, and the filling of the
space occupied by it with fresh material, the old heating conductor may be replaced
by a new one, which is passed transversely through the aforesaid troughs or through
one of the aforesaid conducting cylinders and the contained conducting material, to
and through or into the opposite conducting trough or cylinder and the contained
conducting material, and also through the intervening carbide-forming material. The
electric current will preferably be allowed to pass continually, by one or more heating
conductors, through the carbide-forming material, the current being broken only at
points when and where a portion of the carbide is removed when formed. This
prevents undue fluctuations of the current, and also obviates the necessity of
employing any resistance-regulator, so that the maximum heating energy of the
electric current is utilized for the forination of the carbide.
So simple and efficient is this method that a single operator is sufficient to attend
to an apparatus employing several thousand electrical horse-power.
When employing the heat of combustion preliminarily to, or in conjunction with
the heat of the electric current, I preferably proceed as follows:-I separately and
simultaneously raise a suitable fuel and atmospheric air to a high temperature by
passing them through suitable conduits which are highly heated externally. I
nay employ coal-dust as a fuel, but I prefer to employ water-gas or other suitable
gaseous fuel.
When I have raised the separate currents of air and water-gas to"
.

page_text: a very high temperature, say, for instance, as high as can be obtained by the heat
of ordinary combustion, portions of the highly heated air and water-gas are burned
in another apparatus or furnace, through which the remaining portions of the highly
heated air and water-gas are made to pass, in order that they may be very highly
superheated. Then the highly superheated air and water-gas are thence conducted
into and burned within another apparatus or furnace, within which the carbide-
forming material is placed and subjected to the heat energy of the combustion of the
highly superheated air and water-gas. Or the heated gas and air are superheated in
the second furnace by the burning of a portion of the superheated gas and air, the
remainder thereof being utilized to heat the carbide-forming material.
In Figure 6 I have shown a convenient and advantageous form of apparatus for
this purpose.
kis a furnace for preliminarily heating fuel-gas and air which are
passed respectively through pipes, m extending across the said furnace. These
pipes are arranged in series or groups situated one above another, the
air-pipes m extending at right angles to the gas-pipes ; and the said
groups are connected respectively by chambers or heads 1, m³, and connecting
pipes 12, m².
The heating of these groups of pipes is effected by gases
from an independent source or from a combustion-chamber F' surrounding a
chainber or shaft G in which the carbide-forming materials are placed, which
combustion-chamber is connected by a suitable flue F2 with one or more perforated
pipes in the lower part of the furnace k. Beneath the furnace is a superheating
furnace similarly provided with groups of gas and air pipes l, m connected
respectively with the pipes in the furnace k, and also with tuyeres 13, m" extending
into the combustion-chamber F. If desired, the said tuyeres may extend directly
into the shaft G, containing the carbide-forming materials. I prefer, however, to
burn the superheated gas and air in the said combustion-chamber, so that they will
not come in contact with the said materials. A portion of the superheated gas and
air is conducted through branch-pipes 4, into the furnace p to be burnt therein
for the purpose of superheating the gas and air passing from the pipes in the furnace k
through the pipes in the furnace p. y is a cock for controlling the flow of
superheated gas and air into the said furnace p for the purpose of being burnt
therein. Or, if desired, heated gas from the pipes in the furnace k may be
mixed with superheated air from the pipes m in the furnace p, and the mixture
burnt in the last-namned furnace. Or a portion of the heated gas and air from the
pipes in the furnace k can be burnt in the furnace p for the purpose of superheating
the gas and air passing through the pipes therein.
Oxygen combining with hydrogen, as in the oxy-hydrogen blow-pipe, will
produce a temperature of, say, 5,000 degrees Fahrenheit. This is due to the very
large quantity of heat evolved by the combustion of hydrogen with oxygen; and
while hydrogen will produce about, 62,000 British thermal units per pound in
combustion with oxygen, one pound of carbon will evolve only about 17,000 such
heat units. Nevertheless, carbon is capable of combining with oxygen to produce
heat, even at temperatures above which hydrogen will not combine with oxygen,
that is to say, at temperatures at which hydrogen and oxygen are entirely
dissociated. Therefore, if carbon or a body rich in carbon, such as water-gas, be
preliminarily heated, at a temperature approximating that of the oxy-hydrogen
flame, then a higher temperature may be obtained by the combustion of water-
gas with oxygen than can be obtained by the combustion of hydrogen alone with
oxygen.
So intense a heat may be obtained in the manner above described, that the
lime of the carbide-forming material may be fused, and then, when fused, and
while in a fused state, be subjected to electrical influence, or to the heating
effect of an electric current passed through it, either by the resistance offered by
the fused material itself, or by means of a heating conductor a passed through it in
the manner herein before stated.
The lime of the carbide-forming material may be fused in the presence of the
carbon, without forming carbide, but by the method above stated I consider that a

page_text: temperature above the fusing point of lime will he obtained, which is necessary to
the'production of carbide, and then an electric current may be passed through the
fused material simply to facilitate the reaction required for the formation of
carbide.
The method and apparatas above described are also applicable, as will be readily
understood, for the reduction of aluminium and other metals from refractory ores
or oxides.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the saine is to be performed, I declare that what I
claim is
First. The herein described method of establishing electrical connection between
an electric incandescence heating conductor and an electrode connected with one of
the poles of a source of electrical energy, whereby a yielding or sliding contact is
provided, for the purpose above specified.
Second. An electric incandescence heating conductor extending through and
capable of longitudinal movement in a tube or other suitable receptacle which
contains pulverulent or other suitable material for establishing electrical connection
between such conductor and the said tube or receptacle or other suitable electrode or
terminal, whilst permitting the required longitudinal movement of the said conductor,
substantially as hereinbefore described.
Third. The combination of an electric incandescence heating conductor, a
surrounding metallic tube or cylinder, a mass of pulverulent or granular refractory
conductive material enclosed between the said tube or eylinder and conductor, and
means for compressing the said mass, substantially as hereinbefore described.
Fourth. The combination, with two electrodes or terminals, of an electric
incandescence heating conductor electrically connected therewith through the
medium of compressed pulverulent or other suitable material arranges het ween the
said conductor and each of the said electrodes or terminals, substantially as
hereinbefore described and for the purposes specified.
Fifth. The employment, in an electric furnace, of two or more electric
incandescence heating conductors each electrically connected with two oppositely
arranged electrodes in such a manner as to provide a sliding contact, substantially as
herein before described.
Sixth. The combination of a chamber for the reception of carbide-forming material,
and means for establishing electrical connection between oppositely arranged
electrodes and through the carbide-forming material at two or more points,
substantially as hereinbefore described.
Seventh. The herein described process of making calcium carbide, which consists
in fusing the carbide-forming material by the heat of combustion, and converting
the said material into carbide by the aid of electricity.
Eighth. The superheating of previously heated fuel-gas and air by the combustion
of a portion of such heated or superheated gases, substantially as, and for the
purposes, above specified.
Ninth. In the manufacture of calcium carbide, the herein described process
consisting in heating separate currents of air and fuel-gas, by passing them through
heating furnaces, in the first of which fuel-gas is burned, and in the second, or
succeeding furnace, they are superheated by the combustion of a portion of the highly
heated or superheated air and fuel-gas, and then burning the superheated gases or
the remainder thereof for heating the carbide-forming materials.
Tenth. The combination of a furnace provided with pipes for the passage of gases
to be heated, a combustion-chamber for heating material enclosed in a shaft extending
through the said chamber, and means for burning in the said combustion-chamber
the heated gases from the pipes in the said furnace, substantially as, and for the
purposes, above specified.
Eleventh. The combination of a preliminary heating furnace, a superheating
furnace, pipes in the said furnaces for the passage of gases to be heated or

page_text: superheated, a combustion-chamber for heating materials contained in a shaft
extending through the said chamber, and means for burning in the said combustion-
chamber, the superheated gases from the pipes in the said superheating furnace,
(with or without the means for burning a portion of the said gases in the said
superheating furnace) all substantially as, and for the purposes, above specified.
Twelfth. The improved apparatus constructed substantially as hereinbefore
described with reference to Figures 1, 2 or 3, or to Figures 4 and 5 or to Figure 6
of the drawings and for the purposes specified.
Dated the 11th day of September 1897.
D. YOUNG & Co.,
11 and 12, Southampton Buildings, London, W.C.,
Agents for the Applicant.