An Improved Method of and Apparatus for the Production of Calcium Carbide, applicable also to other purposes.
Year: 1897

page_text: Date of Application, 3rd Feb., 1897
Complete Specification Left, 2nd Nov., 1897-Accepted, 29th Jan.; 1898
PROVISIONAL SPECIFICATION.
An Improved Method of and Apparatus for the Production of Calcium
Carbide, applicable also to other purposes.
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;-
-
The present invention relates to an improved method of and apparatus for the
production of calcium carbide and is applicable also to the reduction of metals
from their oxides and the fixation of atmospheric nitrogen. The invention has
reference particularly to an efficient and economical method whereby the materials
to be treated, (such, for example, as a mixture of lime and coke) after being
preliminarily heated or fixed by the heat of combustion are subjected either inter-
mittently or continuously to a zone of electrical heat energy, and thereby heated
and fused, the finished product being subsequently removed from the zone of
electrical heat energy in the manner hereinafter stated.
In carrying out the invention, an electric circuit is made or completed between
two opposed electrodes by means of a conductor, consisting of a portion of the
finished product, as for example, calcium carbide. The carbide conductor is fused
by the passage through it of an electric current, and I thus have a fused bath of
carbide performing the function of a heating electric conductor, upon which bath,
unconverted carbide forming material may be fed, either continuously or inter-
mittently; whereby, the heat of incandescence, caused by the passage of the
electric current through the fused carbide, converts the fresh material into carbide.
When the fused bath or fluid electric conductor shall, from the freshly converted
material, acquire a sufficient conductivity or carrying capacity for the electric
current, that is to say, when the heating conductor or fluid bath shall become so
large as not to offer sufficient resistance to the passage through it of the electric
current, then a portion of the converted material or fused bath is removed, either
by tapping away the excess of fused carbide, or by lowering the bath relatively
to the position of the electrodes, or by otherwise removing the material.
The fluid carbide conductor is never sufficiently removed or tapped away as to
break contact between the said opposed electrodes, so that there shall always
remain a body of incandescent carbide, maintaining contact between the opposed
electrodes.
Heretofore, carbide has sometimes been made by the incandescence of a core or
conductor passed through a body of coke and lime mixture, so that, by the incan-
descence of the core, the surrounding materials have been converted into carbide,
or the materials have been subjected to the influence of an electric arc in various
ways. By the present invention, I employ, neither a core nor an arc, but a fused
bath or conductor of molten carbide, making contact between two electrodes, upon
which bath are fed the materials to be converted.
I have found that, by means of the oxygen-coal-gas flame, or by means of a
mixture of atmospheric air and coal gas or water gas, (the air and water gas being
preliminarily heated to as high a temperature as possible), burned in contact with.

page_text: a mixture of equal parts of powdered lime and coke, it is possible, by the combus-
tion in the oxygen of the water gas and a-portion of the carbon in the mixture,
to fuse the lime thereof, making a molten mass of lime, with particles of uncon-
sumed carbon suspended therein. I therefore preferably employ this means, and
preliminarily fuse the materials by the heat of combustion prior to their subjection
to electrical influence for conversion into carbide, thereby not only preliminarily
heating the materials in the ordinary sense of the word, but also supplying the
latent heat of fusion by the heat of combustion, so that electricity is simply
employed for the purpose of producing the reaction necessary for forming carbide,
thereby minimising the quantity of electric current needed.
I am led to believe by my experiments that the passage of an electric current
through the body of materials, that is to say the influence of electricity, is neces-
sary to the reaction and one of the objects of the present invention is to furnish,
in a practical manner, the heat necessary for the reaction by the heat of combustion,
and to use electricity only for its electrolytical or combining influence to cause
the said reaction.
I find, furthermore, a very good mixture for my purpose, when producing
calcium carbide, is two parts of bituminous coal to one part of lime, or chalk;
thus, when operating at the mouth of a coal pit, there would be no necessity of
previously coking the coal or of burning the lime. I utilise the gases escaping
from my furnace to preliminarily heat air or I may further utilise the gases in
any suitable manner for working machinery to generate an electric current, I can
thus utilise the excess of gases due to the use of bituminous coal.
In preparing the materials for treatment in my furnace, they are first preferably
pulverised, or thoroughly incorporated, and then compressed, preferably into a
tubular, corrugated or other suitable form that will not admit of too close prox-
imity or packing of the materials, but that will permit of spaces existing in the
said materials, in order to allow the upward flow of the gases through them in
the furnace, and also to make allowance for the swelling of the bituminous coal
when subjected to the heat. within the furnace.
The form of furnace which I preferably employ is one with a rectangular interior
shaft or space for the reception of the materials, the furnace being preferably
vertically disposed, although it may be successfully operated either in an oblique
or a horizontal position. The furnace preferably is made of considerable vertical
height, or has a considerable length of shaft for the reception of the materials, in
order, to as much as possible, utilise the preliminary heating effect of the materials
by combustion therein, and also to give due weight to the column to facilitate the
operation of the furnace, and the conversion of the materials therein and extraction
of the product therefrom. The shaft is preferably made of increased width
in the direction of the passage of the electric current, to obtain a wider space
between the opposed electrodes, than in a transverse direction thereto, and the
furnace shaft is preferably of a width approximating the diameter of the elec-
trodes, so that the materials descending through the shaft above the electrodes
shall arrive in the space between the electrodes in the form of a rectangular body
of material approximating, in one dimension the diameter of the elec-
trodes, and in the other dimension, the distance between them. The
space about the electrodes is preferably made considerably larger than the shaft
above them, and the electrodes are pushed into this chambered portion of the
furnace in such wise, and to such an extent, as to penetrate a certain distance into
the unconverted carbide forming material, (the lime and coke mixture) thus
obtaining a protection to the surrounding walls of the furnace by means of a body
of lime and coke mixture to protect the furnace from the intense heat and products
of the reaction therein.
One of the electrodes may be made in such form, or of such configuration as to
constitute in whole or part the wall of the furnace opposed to the other electrode,
and it may be made of such thickness as to permit the fused material or carbide
to be tapped or drawn off through it, the tap hole being disposed at such elevation

page_text: in respect to the interior molten bed of carbide, as to draw off such portion of it
as may be desired, leaving a sufficient residual quantity to maintain efficient
contact between the opposed electrodes.
The following method of discharging the furnace may be adopted: An aperture
or opening at the bottom of the furnace may be provided of such dimensions as
to permit the body of carbide, formed between the electrodes to descend, a suitable
device being provided to regulate its descent to such an extent as shall permit. a
sufficient body of fused carbide to remain between the electrodes to. maintain the
electrical contact between them.
In order to minimise the expensiveness of the electrodes and to prevent too
rapid consumption of them, I preferably make them as follows:-A mixture, in
suitable proportions, of pulverulent coke or carbon and carbide, is made. This
is compressed and then subjected to a very high temperature, preferably by
passing through the conductor an electric current of sufficient power as to fuse
the carbide, thus agglutinating the particles of carbon, and making an efficient and
firm conductor, and one not much effected by the oxygen set free by the reaction
of lime with coke, because the carbide contained in the electrode will be neutral
to such action, and will serve to cover and protect the particles of carbon, further-
more permitting the electrodes to be made of very cheap material. To this end, a
cylinder of carbon, made in the usual manner, may be filled with the above
mixture and employed as an electrode.
In operating the furnace above described, either or both of the electrodes, (one
of which, at least, is preferably cylindrical) are disposed in such manner as to
permit of their being forced into, or withdrawn from the furnace, and electric
contact is preferably made with the electrode, by means of carbon dust or other
disintegrated or pulverulent or yielding contact substance compressed upon it.
In carrying out my invention for the fixation of atmospheric nitrogen, and the
production of nitrides, cyanides, and the like, I preferably proceed as follows; A
molten bath is maintained between opposed electrodes, in the manner hereinbefore
described, and when such bath is itself a conductor, no additional or subsidiary
conductor need be employed, but when such bath is not a sufficiently good con-
ductor, then the bath may be heated to a desired temperature by the heat of
incandescence of another conducting medium or heating conductor making contact
between the opposed electrodes.
forced
A bath of fused potash and carbon or of fused magnesia, barium, or other
suitable material, may be employed, either mixed or unmixed with carbon, accord-
ing as a cyanide or a nitride is desired to be formed. A current of nitrogen or air
is then caused to circulate either over the said bath, or 1S
upward through it, the air or nitrogen being preferably preliminarily
heated by the heat of combustion or by electricity or both, to as high a temperature
as practicable, in order that it may enter, or come into contact with the fused bath'
at as high a temperature as possible.
An Improved Method of and Apparatus for the Production of Calcium
Carbide, applicable also to other purposes.
HUDSON MAXIM, of 377, Norwood Road, S.E. London, Chemist & Mechanical
Engineer, do hereby declare the nature of this invention, and in what manner the

page_text: same is to be performed, to be particularly described and ascertained in and by the
following statement:-
This invention relates to methods of and apparatus for highly heating and
electro-thermally treating materials, more especially for the manufacture of
calcium carbide, in an efficient and economical manner. According to my inven-
tion the materials to be treated (for example a mixture of bituminous coal and lime
or chalk, or a mixture of lime and coke) are heated to a very high temperature
and are then subjected to an electric current or to a zone of electrical heat energy,
by which they are changed into carbide, the latter being then removed from such
zone in any suitable manner. The electric circuit is made or completed between
two opposed electrodes by means of a conductor consisting of the calcium carbide
formed between the electrodes or by a conducting core. The heat for prelimi-
narily heating the materials to be treated is preferably obtained by burning in a
suitable shaft or chamber through which the materials are fed, fuel gas and air
which have been previously heated by the waste gases from the said shaft or
chamber and further superheated by burning a portion of the fuel gas and air
in a superheating chamber through which the said gas and air are led. Sometimes,
however, the fuel gas is not heated and the combustion may be arranged to take
place in a chamber outside and around the shaft. The hearth or chamber in
which the actual conversion into carbide takes place, as well as the construction
of the electrodes and the method of removing the carbide may be varied in many
ways as will be hereinafter described.
Referring to the accompanying drawings which illustrate my invention —
Fig. 1 is a vertical section of an electrical furnace and preliminary heating
apparatus.
Figs. 2 to 5 are vertical sections, and Fig. 6 is a horizontal section of the electric
hearth illustrating various modifications of construction.
Referring to Fig. 1, the furnace structure A is built up of firebrick enclosed in
a steel casing B. C is the electrical hearth, D denotes one of the electrodes.
There may be one pair of electrodes as indicated in Fig. 3, or there may be several
pairs if desired. The materials to be treated pass to the electrical hearth down a
stack E by gravity, assisted, if necessary, by a weight G, and are heated therein
by gaseous fuel and air which enter through nozzles H, H¹ near the bottom of the
stack. Before arriving at the nozzles H, H', the air and gaseous fuel are very
highly heated as follows, that is to say: J is a heating chamber, which is traversed
by a series of pipes K for the air, and another series & for the gaseous fuel. Lis
a superheating chamber which is similarly traversed by pipes K₁ and k¹, the latter
being continuations of the pipes K, & in the heating chamber. The air enters
the system of pipes at K² and traverses the pipes K and K' successively and then
emerges by the nozzle H¹, while the gaseous fuel enters the system of pipes at k²
and traverses the pipes and successively, and then emerges by the nozzle H,
where it meets the air and is burnt in the shaft E and heats the materials in the
said shaft. The products of combustion passing up the shaft are converted to a
fuel gas carbonic oxide-by an excess of carbon in the material to be treated,
and pass out through openings e near the top and thence by the passage e¹ and
chamber they pass to a perforated pipe e³, whence they emerge and burn in the
heating chamber J, circulate round the pipes K, and heat the air and fuel gas
therein, and finally pass out to the chimney by the flue e. The heated air and
gas from the pipes K, & circulate through the pipes K¹¹ in the superheater L,
portions of the same being drawn off from the lower end of said pipes and delivered
through a burner M into the superheater chamber L, where they are burnt and
serve to generate increased heat in the said chamber, thus further heating the
air and fuel gas passing through the pipes K¹¹. It will thus be understood that
the air and fuel gas are heated to a very high temperature before they emerge
from the nozzles H, H¹ into the shaft E, and consequently when they are burnt
the temperature generated in the shaft is extremely high."

page_text: The heating chambers are preferably lined with magnesia, and the shaft E
with magnesia. The pipes K, k, K¹¹ are made of magnesia. In some instances
the shaft E is oblique or may even be horizontal. In the latter case it will be
necessary to provide means for pushing the materials along it. If preferred the
superheated gas emitting from the nozzles H, H', may burn in a chamber F sur-
rounding the shaft, the products of combustion either passing to heat the pipes in
the heater J, or by the passage F to the flue F¹ (in dotted lines).
I have found that by the above method it is possible by the combustion in the air
of the fuel gas and a portion of the carbon in the mixture to fuse the lime thereof,
making a molten mass of lime, with particles of unconsumed carbon suspended
therein. I therefore by preference employ this means, and preliminarily fuse
the materials by the heat of combustion prior to their subjection to electrical
influence for conversion into carbide, thereby not only preliminarily heating the
materials in the ordinary sense of the word, but also supplying the latent heat of
fusion by the heat of combustion, so that electricity is simply employed for the
purpose of producing the reaction necessary for forming carbide, thereby minimising
the quantity of electric current needed.
I am led to believe by my experiments that the passage of an electric current
in closest proximity to the body of materials, that is to say, the influence of elec-
tricity, is necessary to the reaction and one of the objects of the present invention
is to furnish, in a practicable manner, the heat necessary for the reaction by the
heat of combustion, and to use electricity only for its electrolytical or combining
influence to cause the said reaction.
I find a very good mixture for my purpose is two parts of bituminous coal to
one part of lime or chalk; thus, when operating at the mouth of a coal pit, there
would be no necessity of previously coking the coal or of burning the lime. The
gases being excellent fuel, escaping from my furnace are utilised as above
described and in addition, they may be further utilised in any suitable manner for
working machinery to generate an electric current, thus avoiding any waste of the
excess of gases due to the use of bituminous coal.
In preparing the materials for treatment in my furnace, they are first preferably
pulverised, or thoroughly incorporated, and then compressed, preferably, into
strongly coherent. blocks of tubular, corrugated, or other suitable form that will
not admit of too close proximity or packing of the material, but that will permit
of spaces existing in the said materials, in order to allow the upward flow of the
gases through them in the furnace, and also to make allowance for the swelling
of the bituminous coal when subjected to the heat within the furnace.
The form of furnace which I preferably employ is one having a rectangular
interior shaft or space for the reception of the materials. It is preferably made of
considerable vertical height, or has a considerable length of shaft for the reception
of the materials, in order to, as much as possible, utilise the preliminary heating
effect of the materials by combustion therein, and also to give due weight to the
column to facilitate the operation of the furnace, and the conversion of the materials
therein and extraction of the product therefrom. The shaft is preferably made of
increased width in the direction of the passage of the electric current, to obtain a
wider space between the opposed electrodes than in a transverse direction thereto,
and the furnace shaft is preferably of a width approximating the diameter of the
electrodes, so that the materials descending through the shaft above the electrodes
shall arrive in the space between the electrodes in the form of a rectangular body
of material approximating, in one dimension, the diameter of the electrodes, and in
the other dimension, the distance between them. The space about the electrodes,
that is to say, the electric hearth or electrode chamber C, is made considerably
larger than the shaft, and the electrodes are pushed into this chambered portion
of the furnace in such wise, and to such an extent, as to penetrate a certain distance
into the unconverted carbide forming material (the lime and coke mixture) whereby
the surrounding walls of the furnace are protected by a body of lime and coke
mixture from the intense heat and products of the reaction therein.

page_text: In electrically treating the materials a small conductor of carbon, but preferably
of carbide is placed between the electrodes and raised to intense incandescence by
the electric current passing therethrough, thus combining with and converting the
surrounding materials into a gradually increasing quantity of molten calcium
carbide.
When the fluid electric conductor, or molten converted material shall, from the
freshly converted material, acquire a sufficient conductivity or carrying capacity
for the electric current, that is to say, when the heating conductor or incandescent
fluid shall become so large as not to offer sufficient resistance to the passage through
it of the electric current, then a portion of the converted material is removed,
by tapping away the excess of fused carbide, or by otherwise removing the
material, but the fluid carbide conductor is never sufficiently removed or tapped
away as to break contact between the said opposed electrodes, so that there shall
always remain a body of incandescent carbide, maintaining contact between the
opposed electrodes and serving to continue the process in the above manner.
One of the electrodes is sometimes made in such form or of such configuration
as to constitute in whole or part the wall of the furnace opposite the other elec-
trode as indicated in Fig. 2, and it may be perforated at d to permit the fused
material or carbide to be tapped or drawn off through it, the tap hole being
disposed at such elevation in respect to the interior molten bed of carbide, as to
draw off as much of it as may be desired, leaving a sufficient residual quantity to
maintain efficient contact between the opposed electrodes.
I sometimes discharge the carbide by means of a plunger p, Fig. 4, which
normally forms the floor of the electric hearth and which can be drawn away by
its handle p¹, to allow the carbide to fall, and then is pushed back to discharge the
carbide and to close the bottom of the furnace again. A sufficient body of fused
carbide is allowed to remain between the electrodes, to maintain the electrical
contact between them.
In order to minimise the cost of the electrodes and to prevent too rapid consump
tion of them, I preferably make them as follows;-A mixture, in suitable propor-
tions, of pulverulent coke or carbon and carbide, is made. This is compressed and
then subjected to a very high temperature, preferably by passing through the
conductor an electric current of sufficient power to fuse the carbide, thus aggluti-
nating the particles of carbon and carbide and making an efficient and firm
conductor, (Fig. 2) and one not corroded by the fused carbide nor much affected
by the oxygen set free by the reaction of lime with coke, because the carbide
contained in the electrode which is neutral to such action serves to cover and
protect the particles of carbon. Furthermore, this construction permits the elec-
trodes to be made of very cheap material. To this end, a carbon tube, made in
the usual manner, may be filled with the above mixture, and employed as an
electrode, as indicated in Fig. 2. In Figs. 5 & 6 I have shown electrodes D¹
made of loose carbon dust, or pieces of carbon or both forced into the furnace
against a stop at the back by means of screws q', q¹.
In operating the furnace above described, either or both of the electrodes (one
of which at least, is preferably cylindrical), is or are disposed in such manner
for example, in stuffing boxes d'd, as to permit of their being pushed into or
withdrawn from the furnace, and electric contact is preferably made with the
electrode, by means of carbon dust d³, or other disintegrated or pulverulent or
yielding contact substance compressed upon it by means of screw glands d³ or
otherwise.
In the above described method I fuse the carbide formed between the electrodes,
and thus form a fluid bath of carbide, making contact between the electrodes
upon which bath are fed the materials to be converted. I sometimes, however,
in lieu of the bath, employ an incandescent core or conductor passed through the
body of the coal or coke and lime mixture, so that by the incandescence of the
core the surrounding materials are converted into carbide, or I sometimes employ
an electric arc for this purpose.

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
-
First. The herein described process of making calcium carbide, which consists
in maintaining a body of calcium carbide in a molten condition by passing through
it an electric current, forming carbide from materials supplied to the body of
molten carbide by the incandescent heat thereof, and removing the excess of carbide
thus formed, leaving an incandescent body of carbide for continuing the process.
Second. The herein described method of making calcium carbide in an electrio
furnace, which consists in forming a body of calcium carbide in a molten condition,
by passing through it an electric current, and removing a quantity of the carbide
thus formed through one of the electrodes of the said furnace.
Third. The herein described electrical conductor, consisting of a carbon tube,
filled with a carbide, or a mixture of a carbide and carbon.
Fourth. In the manufacture of calcium carbide the method of preparing carbide
forming materials, which consists of pulverising the materials, incorporating them
together, then compressing or agglutinating solidly together the pulverulent
mixture into blocks and then feeding the same to an electric furnace."
Fifth. An electric furnace having a rectangular chamber provided with elec-
trodes of less diameter than either dimension of the chamber, and provided with a
supply conduit having a diameter approximate to the diameter of the electrodes
to be supplied with a column of carbide forming material, of less diameter than
either dimension of the furnace chamber.
Sixth. The process of treating materials for the production of carbides which
consists in mixing carbonate of one or more metals with a quantity of carbon or
carbonaceous or bituminous material containing volatile matter, sufficiently heating
them to produce carbonic acid gas from the carbonates and fuel gases from the
carbonaceous material, reducing the carbonic acid gas by the carbon present in
the mixture to carbonic oxide and using the fuel gases then produced to continue
heating fresh materials or to produce electric energy for further treating the
materials or for other purposes.
Dated this 2nd day of November 1897