Improvements in Electric Furnaces for use in the Manufacture of Calcium Carbide, applicable also for obtaining Metals from their Salts.
Year: 1897

page_text: Date of Application, 2nd Feb., 1887
Complete Specification Left, 22nd July, 1897-Accepted, 22nd Jan., 1898
no di appication, ENG 100., 1007
Complete Specification Left, 22nd July, 1897-Accepted, 22nd Jan., 1898
PROVISIONAL SPECIFICATION.
Improvements in Electric Furnaces for use in the Manufacture of
Calcium Carbide, applicable also for obtaining Metals from their
Salts.
We, LOUIS BRESSON, Engineer, of 143, Avenue de Saxe and PAUL PACOTTE, Civil
Engineer, of 30, Rue Servient, both of Lyons, in the Republic of France, do horeby
declare the nature of this invention to be as follows:-
This invention relates to an electric furnace or so called " reversible" furnace
and to the use thereof in the manufacture of carbide of calcium and its application
in the Metallurgy for obtaining metals by the electrolytical decomposition at a
high temperature of the salts of these metals.
1. ACTUAL STATE OF THE MANUFACTURE OF CARBIDE OF CALCIUM.
The industrial electric furnaces serving at present for the manufacture of carbide
of calcium are not constructed under the conditions required for the heat generated
by the electrical energy to be wholly absorbed by the bodies brought together,
lime and carbon, which when heated to a high temperature, combine to form
carbide of calcium. The output is far under the theoretical output calculated accord-
ing to the available energy.
On the other hand the use of these furnaces offers great difficulties.
1. They are generally too large; experience has shown that the carbide of
calcium manufactured in small quantity and consequently not being overheated
will produce more acetylene gas.
2. About the end of the manufacture, when the furnace is nearly full, the mass
manufactured in the first place, which is near the furnace-hearth, has become
solid. Therefore to remove the carbide it is necessary that the furnace should be
allowed to cool. The heat which is stored up in the same is thus lost.
3. In the manufacture of carbide of calcium by the methods heretofore in use,
the lime and carbon are mixed up into a very fine powder when the mixture falls
in the furnace as it works a portion of the carbon is converted into carbon-oxide
which burns within the furnace, it undergoes this transformation before it has
time to fix upon the calcium which is not yet separated from its oxygen, which
therefore is still in a state of lime. In order to obviate this inconvenience in the
manufacture, 5 or 6 times the quantity of carbon which enters into the composition
of the carbide of calcium are mixed with the lime. Sometimes the excess of carbon
burus out, the carbide is then pure. Sometimes this excess is not burnt or it is
burnt altogether; in one case the carbide contains carbon, in the other case it
contains lime.
Our electric furnaco which we call "Electric reversible furnace" for our method
for manufacturing carbide of calcium does not present any of the difficulties or
inconveniences involved by the use of all furnaces employed now.

page_text: II. DESCRIPTION OF THE FURNACE.
Our furnace is constructed as follows:
It is composed of a crucible in graphite of slight thickness surrounded with
magnesia it is supported at its base by a red copper breech which supplies thereto
the positive current from a dynamo. Said breech is movable and by means of 4
adjusting screws it may be hold constantly in contact with the furnace. The
crucible and the breech are insulated by their magnesia shell and the whole is
enclosed in a cylinder having a base of a truncated cone shape in sheet steel of
10 m/m. This cylinder is surrounded by a rim carrying two journals movable on
two brackets resting upon an U shaped iron frame. These journals are controlled
by two gear wheels (the motion through the gear wheels may be replaced by a lever)
which receive their motion from a crank. This mechanism imparts to the furnace
a rotary motion on itself around the axis of the journals. The negative current is
supplied by 5 carbons of 30 m/m. in diameter in a lozenge-like arrangement and
equidistant from each other relatively to the surface of the hearth, by means of this
arrangement au incandescent focus is obtained on the whole surface of the furnace,
and the entire mass, receives the same heat and consequently has the same homo-
geneity. These carbons are held by a vertical support which can be moved upwards
by means of a crank acting on a pinion which communicates its motion to a toothed
rack; by means of this mechanism the carbons may be rapidly withdrawn from or
introduced into the furnace.
III. CONSIDERATIONS ON THE USE AND OPERATION OF THE FURNACE.
1. Our furnace absorbs little heat, the shell of the magnesia crucible, a body
absolutely fire-proof reverberates by reflection to the centre of the furnace all the
calorific rays which would attempt to store up in the apparatus; consequently, the
heat generated is entirely utilized. According to our calculations and experiences,
one horse-power, say 736 Watts produced by a current of 12 amperes at 60 Volts,
has given us from 8, 5 kg. to 9 kg. carbide of calcium per twenty-four hours. Our
output is therefore a theoretical one.
2. Our furnace has a capacity 30 cubic decimeters and receives 3000 amperes at
60 volts. As the density of the carbide of calcium is 2, 2, castings of 50 kg. may
be made in this furnace. The time necessary for this production varies from 30
to 35 minutes for one furnace working normally. When the furnace is full, the
product of the beginning of the operation is still semi-liquid, that is to say pasty.
Therefore by means of the reversing mechanism the furnace may be emptied at.
once and remains still hot and ready for a new operation; consequently, there is
no loss in heat for warming the furnace again.
3 By reason of the amount of heat evolved by our furnace, it is impossible to use
the mixture of lime and carbon in a powdered condition; as soon as this mixture
was projected into the furnace, the carbon was converted into carbon oxide, and only
lime remained in the apparatus. We thought of conglomerating our mixture
in the form of small balls having a diameter of from 1 to 1.5 centimetre, and we
ascertained that the theoretical quantity of lime and carbon could be brought
together, however by putting therein a slight excess of carbon to compensate for
that which comes at the surface of the balls at the moment the mixture is intro-
dured into the apparatus. In fact the conglomerates leaving the carbon sheltered
from the air, this carbon arrives at the reaction focus without having its nature
changed.
Under the above conditions of manufacture the carbide of calcium is absolutely
pure. The pellets are introduced into the furnace by means of a mechanical
distributing hopper which, without necessity for looking after the same, supplies
the furnace.

page_text: Improvements in Electric Furnaces for use in the Manufacture of
Calcium Carbide, applicable also for obtaining Metals from their
Salts.
We, LOUIS BRESSON, Engineer, of 143, Avenue de Saxe, and PAUL PACOTTE, Civil
Engineer, of 30, Rue Servient, both of Lyons, in the Republic of France, 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; -
Electric furnaces as practically used at present for the manufacture of calcium
carbide are not constructed to suit the conditions which are necessary in order to
attain that the heat produced by the electric current, be totally absorbed by the
bodies under treatment; namely lime and carbon, which when raised to a high
temperature, combine to form calcium carbide. The actual yield is far below the
theoretical output calculated according to the energy expended.
On the other hand the use of these furnaces presents great difficulties.
1. They are, in general, too large; experience has proved that calcium carbide
manufactured in small quantities and therefore not superheated, was capable of
producing a larger amount of acetylene gas.
2. Toward the end of the manufacturing operation, when the furnace is nearly
full, the mass first manufactured and which is nearest the base of the furnace,
become solid. Therefore in order to withdraw the carbide, it is necessary that the
furnace be cooled down, whereby, the heat accumulated therein, is lost. The same
is also lost if the carbide is caused to flow off in proportion as it is produced.
3. In manufacturing calcium carbide according to the methods heretofore
employed, the lime and the carbon are mixed in form of a very fine powder; as
this mixture is dropped into the working furnace, a portion of the carbon is trans-
formed into oxide of carbon which burns upon the exterior of the furnace; it under-
goes this transformation before it has time to fix upon the calcium, which has not
yet been separated from its oxygen, and which therefore is still in the state of lime.
To remedy this disadvantage in the manufacture, 5 or 6 times the quantity of
carbon which combines to form calcium carbide is mixed with the lime. Some-
times the excess of carbon is burnt, and in that case the carbide is pure. Some-
times this excess has not been burnt or the whole carbon is burnt in the one case
the carbide contains carbon and in the other lime.
"
Our improved electric furnace which we term the reversible electric furnace
for carrying out our process of manufacturing calcium carbide, does not present any
of the difficulties or any such inconveniences as result from the use of all furnaces
heretofore employed.
II. DESCRIPTION OF THE FURNACE.
Referring to the accompanying drawing.
Our furnace is constructed in the following manner :

page_text: :
of magnesia, asbestos or other insulating material held in place by an envelope B
of sheet steel. It is upon this envelope that the spindles H are fixed. The ourrent
is conducted to the breech D which serves as the positive anode.
The cylinder B is provided with two journals H moveable on or in bearings I
carried by a frame K; upon one of these journals a fly wheel O or a lever is mounted
by the aid of which a rotary motion around its horizontal axis can be imparted
to the furnace.
The negative current is conveyed through carbons N so arranged as to distribute
the current over the whole surface of the furnace. These carbons are suspended
from a bracket M which is capable of being raised or lowered through the medium
of a rack G, as indicated in the drawing, or by, a windlass, or by any other means
which allow the carbons to be rapidly withdrawn from, or introduced into the
furnace.
The currents can pass simultaneously through all carbons, or successively through
each carbon. The machines with multiplephase currents furnish a simple means
for obtaining this succession, the number of carbons being equal to the number
of phases less one, of the machine; so that a furnace with several arcs alternating
according to the number of phases is provided.
We have stated that in the case of several carbons, the electric arc passed from
one carbon to the other in order to act upon the whole surface of the substance to
be treated. The same results may be obtained with a single carbon by causing the
arc to travel over the surface of the substance and this may be effected by displacing
the carbon in the crucible in such a manner as to cause it to describe a circum-
ference concentric to the axis of the said crucible.
By means of these arrangements an incandescent fire place extending over the
whole surface of the furnace is obtained; the whole mass receiving the same heat
and consequently presents the same homogeneity.
The regulation of the arc is advantageously effected by means of a small motor L
connected in shunt to the current passing to the furnace, and carrying a pinion
which engages with the rack bar G which raises the carbons. When there is short
circuit in the furnace, the current passes to the dynamo L which raises the carbons
to the point where it only receives the amount of current required to prevent them
from redescending. As the position of equilibrium is maintained, the are is
constantly regulated at a loss of energy which is much less than that sustained
with the use of resistances inserted into the circuit.
III. CONSIDERATIONS OF THE USE AND THE WORKING OF THE FURNACE.
Our furnace absorbs but little heat, the crucible jacket of magnesia or other
refractory substance returns by reflecting to the centre of the furnace all the rays
of heat which would otherwise lodge in the apparatus consequently the heat pro-
duced is totally utilized.
When the furnace is full, the product formed at the commencement of the opera-
tion is still semi-liquid that is to say presents a doughy quality. Therefore by
means of the reversing mechanism the furnace which remains hot. and ready for a
fresh operation, can be emptied by a single operation cousequently no heat is lost
in order to re-heat the furnace.
By reason of the quantity of heat set free by our furnace, it is impossible to
employ the mixture of lime and carbon in a powdered state; if such mixture were
thrown into the furnace, the carbon would be converted into oxide of carbon, and
there would only remain lime in our apparatus. We thought of agglomerating our
mixture in the form of small balls having a diameter between of from 1 to 1.5
centimetre and have found that the theoretically required quantity of lime and
carbon may be used, taking however a slight excess of carbon to compensate for that
which presents itself upon the surface of such balls at the time when the mixture
is introduced into the apparatus. In fact as the agglomerated pieces or balls
leaving the carbon sheltered from the action of the air, this carbon arrives in the

page_text: reaction-furnace without having changed its nature. When manufactured under
the conditions above described the calcium carbide is absolutely pure.
The agglomerates of lime and carbon employed in our furnace are obtained by
the ordinary processes of agglomeration, that is to say by the intimate mixture of
the substances reduced to powder and their compression in moulds. It is not
necessary to add other matter the lime itself serving as an agglomerant.
The small pieces or balls are introduced into the furnace by means of a mechani-
cal-distributing-hopper of any suitable known kind. In furnaces in which a
single rotary carbon-electrode is employed, the feeding is effected periodically after
the arc has passed.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is:- ―
1. An improved electric furnace applicable for the manufacture of calcium
carbide and for obtaining metals by electrolytical decomposition, at high tempera-
ture, from the salts of such metals; the said furnace consisting of a graphite
crucible surrounded by magnesia or other had heat and electricity conducting sub-
stance and provided with journals or axle ends enabling the same to be reversed.
2. In the furnace constructed as above described: the anode formed by a
metallic breech in perfect contact with the base of the crucible; the cathode being
constituted by several carbons equally distributed over the surface of the furnace,
or by a single carbon circularly displaceable around the axis of the furnace; and
the device for regulating the arc or arcs formed between the said anode and cathode
by means of a dynamo connected in shunt to the current passing to the furnace.
3. In the manufacture of calcium carbide by means of the furnace above
described the feeding of the furnace with a mixture of lime and carbon in a
suitably agglomerated state.
Dated this 22nd day of July 1897.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agonts for the Applicants.