Improvements in the Process and' Apparatus for the Production of Carbide of Calcium.
Year: 1896

page_text: COMPLETE 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 and in what manner the same is to be
performed to be particularly described and. ascertained in and' by the following
statement:-
Up to the present time the electric, current has been the sole, source of heat
utilized in furnaces in which carbide of calcium, called in commerce carbite has
been produced on a manufacturing scale.
The current is introduced into a powdered mass, a mixture of lime. and carbon,
by means of thick carbon electrodes, and the pulverulent materials are brought to
the temperatures of the electric arc.
The considerable quantity of heat necessary to bring the lime and carbon from
the temperature of the atmosphere to that necessary to fuse and soften them, say
about 3000° C. is furnished entirely by electric energy.
At this high temperature the materials must be fused and furnished with the .
latent heat of fusion.
Finally, when the temperature is at about 2500° or 2800° there must be
furnished the quantity of heat necessary for disassociating the lime (oxide of
calcium), and for allowing the fixed carbon which is more resistant to heat than the
oxygen to take the place of this latter and. to replace it in the combination.
The affinity of calcium for oxygen being very much greater than the affinity of
this metal for the carbon, the balance of the. double reaction is paid for by loss of
heat which is compensated for by the electric current.
Such is the actual working of the electric furnaces.
The present invention has for its object a furnace for the manufacture of carbite,
but in which the electric current is used only to complete the chemical reaction of
the calcium with the carbon.
This furnace works by layers or zones of temperatures rising propressively in
proportion to the intensity of the.combustible employed.
The following is a description of the apparatus which is shewn in vertical section
in the annexed drawing.
The furnace is arranged vertically or it might be obliquely in such a manner
that the materials introduced at the top descend towards the bottom by their own
weight.
A is the outer casing of a cupola, very similar to the furnaces employed for the
fusion of iron.
B is an inner lining of refractory bricks of the best possible quality or it might
be of other suitable material.
The furnace is divided into three portions or zones Heated successively by more
and more intense sources of heat:
A mixture of coke and lime with excess of carbon is introduced into the furnace C ;
a strong current of air is led in by the tuyere D.
There are several tuyeres D placed round the circumference of the furnace and
at the same height.
.
:
The carbon burns under the action of the current of air and: heats the lime with
the excess of, unburnt carbon to. about 2000° C.
In the portion E situated below C, one or more blow pipes are placed formed of
two pipes F G which bring hydrogen and oxygen into the cupola.

page_text: Water gas with a current of air, oxygen or air enriched with oxygen may also
be employed.
The oxygen of the lime given off in the lower portion H will moreover augment
the intensity of the combustion of the hydrogen.
In the portion E of the cupola, the mixture of lime and carbon is brought to the
softening point at about 2300° to 2400° C.
As many blow pipes are placed on the circumference of the cupola as are
necessary to insure regular heating of the mass.
Lastly in the portion H is the electric arc which plays between the two stout
electrodes I I.
These electrodes are placed in such a manner that the arc is very exactly in the
centre of the cupola.
The temperature rises above 3000° C. and the double reaction takes place; the
gaseous oxygen given off feeds the combustion at E, carbon taking its place.
The temperature is so elevated that the inner lining of the surface must be
protected.
The following is a suitable arrangement for this purpose.
There is formed in the bottom at K a narrow opening, care being taken that the
sides of the opening are raised in the direction of the voltaic arc, thus having the
form of a crater cone.
By this arrangement the walls of the furnace are protected by masses of carbite
which cannot flow away and remain staguant against the sides.
By the natural action of radiation, they thicken and lose a little of their high
temperature.
The fluid carbite flows by the opening K into the crucible L.
By means of bars the opening K is kept always open.
To work the furnace it is filled with lime and carbon and then the three stages
are lighted up.
As soon as the liquid carbite commences to flow the furnace is charged at the
top in exact proportion to the rate of flow, care being taken to use a mixture with
excess of carbon, the excess being determined according to the results obtained and
the nature of the gas led in by the blow pipes.
Of course the number of stages or zones of heating may be increased or in certain
cases there may be only two heating zones, the first heated by air and carbon and
the second by the electric arc.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
. claim is :-
1. In the manufacture of carbite, heating a mixture of lime and carbon first by
the combustion of fuel and then by the electric arc obtaining thereby a further rise
of temperature sufficient to bring about the desired reaction.
2. A furnace for the manufacture of carbite in which the mixture of lime and
carbon is progressively heated.
a) By the combustion of carbon by the action of a strong current of air, in the
upper portions of the furnace.
b) By the hydrogen and oxygen blow pipes, or water gas utilising the oxygen
of the lime to increase its calorific powers.
c) By the electric arc to complete the operation.
3. The furnace for the manufacture of carbite substantially as described and
shown in the annexed drawing, arranged in such a manner that the liquid carbite
protects the most exposed portion of the lining.
Dated this Second day of May 1806
CARPMAEL & Co.,
Agents for the Applicant.