Improvements in the Process and Apparatus for the Production of Carbide of Calcium.
Year: 1897

page_text: Date of Application (in United Kingdom), 20th Sept., 1897
Complete Specification Left, 20th June, 1898-Accepted, 23rd July, 1898
PROVISIONAL SPECIFICATION.
Improvements in the Process and Apparatus for the Production of
Carbide of Calcium.
I, RAOUL PIERRE PICTET, of Geneva, Switzerland, Chemist, do hereby declare
the nature of this invention to be as follows:-
-
Up to the present the only furnaces by means of which carbide of calcium,
called in commerce carbite, has been produced commercially, have utilised as sole
source of heat the electric current in special furnaces.
The current is introduced into a powdery mass, a mixture of lime and carbon,
by means of strong carbon electrodes and the powdered substances are brought
to the temperatures of the electric arc.
The considerable quantity of heat required for bringing the lime and carbon
from the surrounding temperature to that required for fusing and softening them,
say about 3000° C., is supplied entirely by electric energy.
At this high temperature the materials must be fused and supplied with the
latent heat of fusion.
Finally when the temperature has been raised to about 2500° C. or 2800° C.
the necessary heat must be supplied for dissociating the lime, (oxide of calcium),
and allowing the fixed carbon, which is more resistant to heat than the oxygen,
to take the place of this latter and replace it in the combination.
The affinity of calcium for oxygen being very much greater than that of this
metal for carbon, the balance of the double reaction is made up by this loss of heat
which the electric current compensates.
This is the actual working of electrical furnaces. The present patent application
has for its object a furnace intended for the manufacture of carbite, but by em-
ploying the electric current solely for terminating the chemical reaction of the
calcium with the carbon.
This furnace acts by stages or zones of temperatures, rising progressively in
accordance with the power of the combustible employed.
I construct the furnace vertically or very obliquely, in such a manner that all
the materials introduced from above descend naturally towards the bottom by the
sole action of their weight.
The furnace, which has a general resemblance to a cupola used for the fusion
of iron, comprises an outer casing, and an inner casing some distance within the
outer casing, made of fire bricks of the very best possible quality, or of any

page_text: other suitable material, so forming an inner chamber or crucible and a chamber
between the double casing.
A charging passage is provided leading from the outside of the furnace into
the upper part of the inner chamber, and through this is introduced a mixture of
coke and lime with an excess of carbon.
In order to obtain a reducing action, it is suitable to mix with these materials
a certain quantity of long flame coal, pitch, tar and other residues from the treat-
ment of coal, which, by the progressively high temperatures of the furnace give
off hydrogen more or less pure.
Instead of introducing the substances into the interior in the form of powder,
it is in certain cases agglomerated into the form of sufficiently hard briquettes,
and from the outside, through the double casing of the furnace, a certain quantity
of air is passed, through tuyeres of fire brick. The air becomes heated in passing
through the double casing which is kept at a high temperature by means of a coke
or coal fire maintained in the lower part of this double casing, and then, being
heated, it penetrates round the briquettes.
The oxygen combines with the hydrogen to form steam; a portion of the
oxygen combines with a portion of the carbon to form carbonic oxide and carbonic
acid. The heat produced by these reactions and the mixture of all these gases,
as well as those produced by the decomposition of the lime by the electric arc,
rises in the furnace and heats the mass of the materials which are thus brought
to a high temperature before being subjected to the electric arc.
The briquettes allow these gases to circulate and descend again afterwards into
the double casing by means of chimneys constructed in the thickness of the
furnace, and finally to escape outside by a chimney.
The effect of this arrangement is to diminish the quantity of combustible re-
quired for obtaining the desired temperature between the outer and inner casings.
In order to obtain an easier fusion of the mass, an appropriate flux may in
certain cases be added to it.
A little below the tuyeres the mixture of lime and carbon is brought to the
softening point at about 2300° C. to 2400° C.
Lastly, near the bottom of the inner chamber is the place occupied by the
electric arc which passes between two carbon electrodes.
These electrodes are so placed that the arc is very exactly in the centre of the
inner chamber.
The temperature rises beyond 3000° C. and the reaction terminates.
The temperature is so high that it is necessary to protect the inner casing of
the furnace.
The following is an arrangement which is suitable for this purpose.
At the bottom of the inner chamber a narrow opening is arranged, care being
taken that the edges of the opening rise in the direction of the voltaic arc, thus
assuming the form of a crater cone.
Owing to this arrangement, the walls of the furnace are protected by masses
of carbite which cannot run out, and remain stagnant against the edges.
By the natural action of radiation they thicken and lose a little of their high
temperature.
The fluid carbite flows naturally through the narrow opening before referred
to into a suitable receptacle.
A system of poking allows the opening to be kept constantly open.
To work the furnace, the first thing is to fill it with the materials indicated
above, then it is lit up and the electric current is sent through.
As soon as the liquid carbite commences to flow, supplies are put in above
through the charging passage in exact proportion to the strength of the flow,
care being taken to put in a mixture with an excess of carbon; an excess which is
determined by practical results.
As a matter of course, one might, without going beyond the limits of the
present invention, increase the number of stages or zones of heating; as well as,

page_text: in certain cases, have only two zones of heating, the first being heated by air and
carbon and the second by the electric arc.
Dated this 18th day of September 1897
SLOAN & LLOYD BARNES,
26, Castle Street, Liverpool, Patent Agents.
Improvements in the Process and Apparatus for the Production of
Carbide of Calcium.
I, RAOUL PIERRE PICTET, of Geneva, Switzerland, Chemist, do hereby declare
the nature of this invention and in what manner the same is to be performed,. to
be particularly described and ascertained in and by the following statement:-
My present invention has reference to the production of carbide of calcium,
called in commerce carbite, and comprises certain improvements applicable to my
previous invention for which I have obtained Letters Patent dated 2nd May, 1896,
and numbered 9358.
Apart from my said previous invention the only furnaces by means of which
carbide of calcium has hitherto been produced commercially, have utilised as sole
source of heat the electric current.
The current is introduced into a powdery mass, a mixture of lime and carbon,
by means of strong carbon electrodes and the powdered substances are brought to
the temperatures of the electric arc.
The considerable quantity of heat required for bringing the lime and carbon
from the surrounding temperature to that required for fusing and softening them,
say about 3000° C., is supplied entirely by electric energy.
At this high temperature the materials must be fused and supplied with the
latent heat of fusion.
Finally when the temperature has been raised to about 2500° C. or 2800° C.
the necessary heat must be supplied for dissocating the lime, oxide of calcium,
and allowing the fixed carbon, which is more resistant to heat than the oxygen,
to take the place of this latter and replace it in the combination.
The affinity of calcium for oxygen being very much greater than that of this
metal for carbon, the balance of the double reaction is made up by this loss of heat
which the electric current compensates.
This is the actual working of electrical furnaces. The present invention
has for its object a furnace intended for the manufacture of carbite, but by em-
ploying the electric current solely for terminating the chemical reaction of the
calcium with the carbon.
This furnace acts by stages or zones of temperatures, rising progressively in
accordance with the power of the combustible employed.
I have illustrated my invention in the accompanying drawings, in which Figs. I
and II are sectional elevations on the lines X, X, and Y, Y, respectively of
Fig. III, and Fig. III is a sectional plan on the line Z, Z, of Figs. I and II.
Throughout the drawings, the same parts are indicated by the same reference
figures.
I construct the furnace vertically or very obliquely, in such a manner that all
the materials introduced from above descend naturally towards the bottom by the
sole action of their weight.
A is the outer casing of the cupola very similar to the furnaces used for the
fusion of iron..

page_text: B is an inner casing of fire bricks of the very best possible quality, or of any
other suitable material..
Through the upper part a of the furnace is introduced a mixture 6 of coke and
lime with an excess of carbon.
In order to obtain a reducing action, it is suitable to mix with these materials
a certain quantity of long flame coal, pitch, tar and other residues from the treat-
ment of coal, which by the progressively high temperatures of the furnace give
off hydrogen more or less pure.
-Instead of introducing the substance into the interior in the form of powder,
it is in certain cases agglomerated into the form of sufficiently hard briquettes,
and from the outside, through the double casing of the furnace, a certain quantity
of air is passed through tuyeres of fire brick, of which only two, C and D are
represented in the drawing. The air becomes heated in passing through the
double casing which is kept at a high temperature by means of a coke or coal
fire maintained in the lower part of this double casing, and then, being heated,
it penetrates round the briquettes.
The oxygen combines with the hydrogen to form steam; a portion of the
oxygen combines with a portion of the carbon to form carbonic oxide and carbonic
acid. The heat produced by these reactions and the mixture of all these gases,
as well as those produced by the decomposition of the lime by the electric arc,
rises in the furnace and heats the mass of the materials which are thus brought
to a high temperature before being subjected to the electric arc.
The briquettes allow these gases to circulate and descend again afterwards into
the double casing by means of chimneys d constructed in the thickness of the
furnace, and finally to escape outside by a chimney.
The effect of this arrangement is to diminish the quantity of combustible re-
quired for obtaining the desired temperature between the two casings A and B.
In order to obtain an easier fusion of the mass, an appropriate flux may in
certain cases be added to it.
In the part 6 of the cupola the mixture of lime and carbon is brought to the
softening point at about 2300° C. to 2400° C.
Lastly at 6 is the place occupied by the electric arc which passes between the
two carbon electrodes E, E¹.
These electrodes are so placed that the arc is very exactly in the centre of the
cupola.
The temperature rises beyond 3000° C. and the reaction terminates.
The temperature is so high that it is necessary to protect the inner casing of
the furnace.
The following is an arrangement which is suitable for this purpose.
At the bottom, at F, a narrow opening is arranged, care being taken that the
edges of the opening rise in the direction of the voltaic arc, thus assuming the
form of a crater cone.
Owing to this arrangement, the walls of the furnace are protected by masses
of carbite which cannot run out and remain stagnant against the edges.
By the natural action of radiation they thicken and lose a little of their high
temperature.
The fluid carbide flows naturally through the opening F into G where it may
be collected in moulds.
A system of poking allows the opening F to be kept constantly open.
To work the furnace the first thing is to fill it with the materials indicated
above, then it is lit up and the electric current is sent through.
"
As soon as the liquid carbite commences to flow, supplies are put in above
through a in exact proportion to the strength of the flow, care being taken to
put in a mixture with an excess of carbon, an excess which is determined by
practical results.
As a matter of course, one might, without going beyond the limits of the
present invention, increase the number of stages or zones of heating; as well as,

page_text: in certain cases, have only two zones of heating, the first being heated by air and
carbon and the second by the electric arc, and the details of execution may
obviously be varied according to requirements.
I wish it to be understood that I make no claim herein to any features of the
process and apparatus for the production of carbide of calcium set forth in the
Specification to my prior Letters Patent aforesaid, but
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:-
1. The process of preparing carbite which consists in mixing with powdered
lime and carbon some reducing substances at high temperature, such as coal, pitch
and others with or without the addition of fluxes, and then introducing these sub-
stances into a suitable furnace into which air is brought by tuyeres, which in
combining with the hydrogen and the carbon heats the substances intensely before
their arrival at the electric arc, substantially as described.
2. The furnace for the manufacture of carbite arranged in such a manner that
the liquid carbite protects the most exposed portion of the casing, and that the
gases formed in the central portion are utilised for heating the outer casing,
substantially as described and illustrated.
Dated this 18th day of June 1898.
SLOAN & LLOYD BARNES,
Castle Chambers, 26, Castle Street, Liverpool,
Agents for the Applicant.