An Improved Process and Apparatus, for the Manufacture of Calcium Carbide.
Year: 1896

page_text: Date of Application, 23rd June, 1896-Accepted,. 5th: Sept.,. 1896
COMPLETE SPECIFICATION."
An Improved Process and Apparatus, for the Manufacture of
Calcium Carbide.
We, WILLIAM ROBERTS KING, Mechanical Engineer, and FRANCIS. WYATT,
Chemist, both of 12 Old Slip, New York City, New York; United States of
America, 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:-
The object of our invention is to provide an improved process of forming calcium
carbide and an improved electric furnace for carrying out said process and for the
reduction of metallic oxides generally, which process and furnace shall not only be
more effective, simple and cheap than those heretofore employed, but shall also be
capable of use in a substantially continuous operation.
In processes heretofore employed, it has been found" necessary to wait after a
quantity of calcium carbide has been formed by the action of an electric arc
furnace a considerable time for the furnace and its charge to cool before removing
the charge and recharging. Many ingenious attempts have been made to increase
the, capacity of such furnaces and to diminish the time during which the furnace
has to remain idle; but the delay is still very considerable and seriously interferes
with the commercial manufacture of calcium carbide. There are very many other
serious difficulties in the processes theretofore employed, which will readily suggest
themselves to persons who are practically familiar with this art; and as far as we
are aware, no thoroughly satisfactory process of forming calcium carbide has as yet
been found.
Our improved process enables us to dispense altogether with a furnace and does
away entirely with the necessity of waiting for the substance under treatment to
be cooled before a second charge can be operated upon. In this way, our process
becomes substantially continuous, the current being turned off for such a short
time that the aggregate of such stoppages in a day's run is of practically little
importance.
To carry out this invention and secure the desired results, we first make a heap
of pulverized coke and ground lime of any desired height. This may be a simple,
heap or mound of ordinary hillock shape in the open air or the sides may be shored
up to prevent the mound from taking up too much. room, if preferred. This
shoring up may be done by wooden planks, bricks or any other material desired,
but is not in any sense necessary to the carrying out of the process.
We then force..downward through the centre of this heap, until it reaches a
point sufficiently near the bottom to allow the insertion of an electrode, a core of
good conducting material.. Of course, if desired, the electrode may be first put'in
position, and the mound made.over it. Electric connection is made with the lower
end of this core, through the electrode.
The upper: end, of this core is then electrically connected preferably by means of
an electrode to the other pole of a battery or dynamo machine and the mixture.
of coke and lime heaped up around this point of connection to a sufficient height
to shut out the air.. Either a direct or an alternating current may be employed, as
preferred..
The current is..then turned on and continued until-the-voltmeter and ammeter.
show that the currrent is no longer fusing the carbon and calcium to produce
calcium carbide. This becomes evident when the voltage gets too low or the

page_text: resistance too. high. During the operation, the gases set free by the decomposition
of the lime and coke seek the surface of the heap, where they burst into flame.
Should the flame at any time be too prominent, the workman should shovel a little
more of the mound on to the flame, as this undue prominence shows the presence
of a too ready escape for the gases. When the operation is complete, there is a
white hot nugget of calcium carbide surrounding or taking the place of the core.
The core has preferably been destroyed and if made of carbon of coke, forms an
integral part of the calcium carbide nugget.
The nugget is now lifted out of the mound and transported to a convenient place
where it is allowed to cool. A new core is substituted for the old one, the mound
of lime and coke heaped up around it, electrical connection again made, and a new
nugget formed.
We have found in spite of the intense heat necessary for the formation of
calcium carbide, namely, about 5,000 degrees, Fahrenheit, which has to be
maintained in the vicinity of the core, the surface of the mound, except where
the gases are burning, is sufficiently cool to be handled readily. It does not
heat the shovels of the workmen and does not even feel. uncomfortably warm to
the hand.
It is obvious that our improved process is of extreme simplicity, doing away
with all elaborate and expensive apparatus and consists virtually in the heating of
the vertical centre of a mound composed of pulverized coke and ground lime to a
white heat by the passage through said vertical centre of an electric current
along the conducting core which preferably becomes destroyed during the
process..
We have found that simple pulverized lime and coke mixed in about equal
proportions may be effectively employed in our improved process without previous
treatment.
:
This process, though particularly intended for the formation of calcium carbide,
may be employed with advantage in the formation of the carbides of the other
alkali metals and alkaline earth metals by substituting their oxides or compounds
for the lime..
Simple mechanism for carrying our improved process into practical operation,
without employing a furnace, is shown in Fig. 1 of the accompanying drawings, in
which:
A is a mound of mixed coke and lime resting upon the ground or floor B. At
about the vertical centre of this mound, we set the lower electrode C, which is
connected to a dynamo machine by the wire a. Dis the core, which is preferably
of carbon, of smaller diameter than the electrode, and which rests upon the lower
electrode in a substantially vertical position through the vertical centre of the
mound. E is the upper electrode .in. substantially vertical line with the lower.
electrode, and when in operation, is supported only by the core D and the
surrounding mass of material. As these latter fuse and thereby shrink, the upper
electrode is allowed to descend freely by reason of its weight. F is a simple form
of supporting frame for the electrode, when not in use. The electrode is mounted
upon the slide rods bb of good conducting material, which pass through the
insulating sleeves c-c attached to the frame F. and at their upper ends are con-
nected to the wire d which leads to the dynamo machine.. The electrode is lifted
away from the mound, when not in use, by the .chain G passing over the pulley f
and secured to the roller g, which is free to revolve in one direction, but is turned
in the other direction by the crank h and held in place by the pawl and ratchet
device usual in such cases.
This frame F is a swinging frame for obvious reasons.
His a simple swinging frame carrying the lifting tongs I and adapted to bring
said tongs over the vertical centre of the mound, into which they are adapted to
descend and grasp the nugget, while still hot, and raise it out of the mound. The
frame is then swung out of the way and the nugget is deposited on any suitable.
transporting device, not shown...
'

page_text: When, for any reason, it is preferable to employ a furnace in carrying out this
process, we prefer to use one like that shown in Fig. 2 of the drawings.
Heretofore, when calcium carbide has been manufactured in an electric furnace,
it has been usual to employ an electric arc furnace. We have not found 'the
electric are very well adapted to this purpose; and one object of our invention is
to provide a simple form of electric furnace, which employs the incandescent
principle in distinction from the are principle.
.
Among the many disadvantages, which, aside from its expensiveness, attend the use
of the electric are for this purpose, may be mentioned, two which are, perhaps, the
most serious. The first is that the heat of the arc being more effective elsewhere
than at the centre of the field, for the reason that after the formation of the
carbide, no further action takes place, it has been found that the calcium carbide,
when formed, frequently contains an unassimilated mass of carbon or coke in its
centre. This indicates an absolute loss of just so much energy. The second
disadvantage is that the distance between the electrodes and the resistance of the
current are constantly changing to conform to the changes in character and
quantity of the molten mass within the electric field.
Referring to Fig. 2:
}
K is an upright furnace open at the top. The walls and bottom e-e of this
furnace may be made of fire brick, common brick or any desired durable material
with or without a non-conducting granular filling i, as'desired, as the mixture from
which we manufacture the calcium carbide is such a bad conductor of heat and
electricity that the walls of the furnace are not subjected, even where the furnace
is run continuously, to any undue amount of heat or electric force.
Through the bottom of the furnace and preferably in its vertical centre, there
projects upward the negative electrode C. This is preferably a good sized carbon
stick; but we have found that the wear upon this electrode is so slight that it is
not necessary to provide any feeding or adjusting mechanism for it. When in
course of time, the top of the electrode wears down to the level of the bottom of
the furnace, a blow of a hammer will drive it in enough for 'all practical purposes.
It is not necessary to the action of the furnace that this electrode should project
into the furnace at all. It is, however, a matter of convenience in bringing about
contact with the destructible core to have the electrode project somewhat above
the bottom of the furnace, as its position has to be discovered by feeling. This
electrode is of course connected by a suitable wire a to the negative pole of
the dynamo or other source of electric supply.
E is the positive electrode which is adjustably mounted upon the swinging
frame F which stands at one side of the furnace and is provided with a raising and
lowering device J consisting of the chain G attached to the electrode and passing
over the pulley f on the framework. The other end of said chain is attached
to the roller g provided with a suitable ratchet, as shown, the roller being free to
turn in one direction to permit the electrode to move downward, when otherwise
unsupported. The electrode is lifted by turning the roller g in the opposite
direction by the crank h, by means of which the electrode E may be lifted
or depressed, as 'occasion requires. This electrode is connected to the positive pole
of the dynamo by the wire d and conducting rods b-b, which are insulated from
the framework F by the posts cc, through which they pass, and is preferably a
carbon stick of the same diameter as the electrode C.
The distance between these electrodes is of slight importance and will depend
upon the desired height of the furnace, as they are not intended, when in action, to
shoot a spark across the intervening space, but are connected by the core D. This
core should be of good conducting material and is preferably a small rod of carbon
or coke, so that it may be destroyed and become a constituent part of the calcium
carbide as it forms. .
>
A is the material ont of which the calcium carbide is to be formed. This
material consists of about equal portions of pulverized coke and ground lime, and
is simply shoveled into the furnace to any desired height and the conducting

page_text: core D is then driven down through the mass until it comes in substantial contact
with the electrode C. It is not necessary that the contact thus brought about
should be electrically perfect, as the operation of the furnace will soon dispose of
any particles of material which may be crushed or held between the lower end.
of the core and the upper part of the electrode.
The
... The swinging frame F is then turned so as to bring the electrode E directly over
the core D and the electrode is then lowered into contact with the core.
material A is then heaped up a little around the sides of the upper electrode, so as
to prevent free access of the air to said core.
I is a pair of grasping jaws or lifting tongs suitably mounted upon a swinging.
. device H conveniently located near the furnace. Its function is to force its way
downward through the mass of material after the calcium carbide has been formed,
the latter being in the form of a nugget, and rising, lift 'this nugget clear of the
furnace and carry it to a convenient distance, where it may be allowed to cool and
subjected to any desired subsequent operation. As this removal of the nugget.
takes place without allowing the charge of the furnace to cool and as another
conduction core can be inserted immediately, it is obvious that the interval between
successive charges of the furnace is so slight that the operation may be fairly
considered continuous.
Of course, very extensive modifications may be made in the various devices for
bringing the upper electrode into position and removing it therefrom or for the
removal of the nugget or for the insertion of the conducting core, without departing
from the spirit of our invention.
The operation of our improved furnace is as follows:
A mixture of lime and coke is put in the furnace to the desired height, the upper
electrode being out of the way. A suitable conducting core is forced down through
the material substantially into contact with the electrode C. The upper electrode
is then swung into position and lowered into contact with the conducting core.
The mixed lime and coke is heaped up around the sides of the upper electrode so
as to cover its point of contact with the core. The current is then turned on.
and the core brought to incandescence. Either a direct or an alternating current
may be used. The white heat is maintained until a nugget of calcium carbide is
formed. This is readily determined by the ammeter and voltmeter usually employed
for testing electric currents.
The maintenance of a temperature sufficient to keep the mass at white heat
necessitates the presence in the path of the current, as is well known, of a large
amount of resistance. This is indicated by the number of volts and amperes shown
by the ammeter and volt-meter. The fused calcium carbide offering much less
resistance to the current than the mixture of coke and lime, it is obvious that when
the resistance is thus shown to have fallen below that of said mixture, the current
is doing no work, but simply flowing along the fused calcium carbide.
The upper electrode is then raised and swung out of the way. The grasping
jaws are then swung over the furnace and lowered open into the mass of coke and
lime. The jaws are then closed around the nugget of calcium carbide and rising,
lift it out of the mass, which then falls in and fills the hole thereby. left, while the.
jaws are swung away carrying the calcium carbide nugget. A new core is inserted,
a little more coke and lime shoveled into the furnace and a new nugget formed in
the same way. This process can be continued indefinitely.
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. The above described substantially continuous process of forming calcium
carbide, which consists in forming a mound of coke and lime mixed in proper
proportions around, a core of conducting material supported in vertical position
between two, superposed electrodes, heating the vertical centre of said mound to
incandescence by passing an electric current through said electrodes and core and

page_text: maintaining said current until a nugget of calcium carbide is formed in said mound,.
permitting the upper electrode to descend freely as the supporting mixture beneath
it is gradually reduced and fused, removing said nugget while hot, inserting a new
core, covering it with the material of said mound and repeating the specified
steps.
2. The above described process of forming calcium carbide, which consists in
forming a mound of coke and lime mixed in proper proportions around a core of
conducting material supported in vertical position between two superposed
electrodes, heating the vertical centre of said mound to incandescence by passing
an electric current through said electrodes and core and maintaining said current,
until a nugget of calcium carbide is formed in said mound, permitting the upper
electrode to descend freely as the supporting mixture beneath it is gradually
reduced and fused, removing said nugget, inserting a new core, covering it with
the material of said mound and repeating the specified steps.
3. The above described electric furnace for producing calcium carbide, which
consists of two electrodes, one above the other, the upper one being removable,
devices for raising, lowering and removing the upper electrode, suitable electric
connections for connecting the two electrodes with currents of opposite polarity, a
conducting core connecting said electrodes with each other when in operating
position, and devices, substantially as described, for raising the carbide nugget,.
when formed, out of said furnace, so that the latter may be used immediately for
the formation of another nugget.
Dated this 5th day of June 1896.
WILLIAM ROBERTS KING.
FRANCIS WYATT.
Haseltine, Lake & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicants..