An Improved Process of and Apparatus for Electrically Heating Compact or Pulverized Substances Difficult to Fuse or Infusible.
Year: 1899

page_text: Date of Application, 20th Mar., 1899-Accepted, 6th May, 1899
COMPLETE SPECIFICATION.
An Improved Process of and Apparatus for Electrically Heating
Compact or Pulverized Substances Difficult to Fuse or Infusible.
I, WILHELM BORCHERS, of 3, Lousberg Strasse, Aix la Chapelle, in the German
Empire, Professor of Metallurgy, 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, reference being had to
the accompanying drawings and to the letters and figures marked thereon, that is
to say:-
This invention relates to an improved process of, and apparatus for, electrically
heating compact or pulverized substances difficult to fuse, or infusible.
The construction of electric furnaces, as at present employed, is based upon the
following principles:
The substance to be heated itself forms the heating resistance; or is brought
into contact with an electrically heated resistance; or forms one or both poles of
an electric arc, or is placed in a chamber heated by independent arcs.
Now, in all cases, where it was found necessary to heat a substance by the
electric arc, the following defects could not be entirely overcome when using
furnaces of the kind heretofore constructed for this purpose;
For example, the heat generated by the are was distributed over a too limited
space; the distribution of this heat by the grouping of several smaller arcs in or
around the substances to be fused presented great difficulties, as regards the regula-
tion of these arcs; moreover, it frequently occurred that in the case of difficultly
fusing substances, in view of the reduced area or radius within which the heat
acted, that the electrodes became welded or stuck to the substances treated, or
to other parts.
Notwithstanding the many reactions taking place in electric furnaces that are
mainly owing to the sudden nature of the heating, yet it occasionally occurred―
for example, in the heating of continuous hands or slabs of material (such as
hereinafter referred to)that a too rapid change of temperature, for instance from
the normal to the assumed temperature of 3500° C. of the arc, was either injurious
or undesirable.
If, therefore, in the case of reactions in electric furnaces, a preliminary heating
of the charge is not only not injurious, but even advantageous, or if in the case of more
easily fusible substances, it should be desired to keep the fused product heated
when leaving the zone of the arc, I can by combining both heating methods, apply
the advantages of resistance heating (consisting in facilitating the distribution
and regulation of heat) to arc furnaces.
The following examples reference to which is made in the drawing will at once
show that, in this manner, many of the defects inherent in electric furnaces of one
ezzatom or the other, are obviated.

page_text: Figure represents a furnace, such for instance as would be suitable for
producing calcium carbide, or metals fusing with difficulty, that is to say, for
producing substances the crude constituents, or ores, of which, as well as
the products themselves, are fusible with difficulty.
Figure 2 is a section on the line a, b, of Figure 1.
Figure 3 shows an arrangement in which the arc pole is located above that
portion of the hearth in which the smelted product accumulates.
Figure 4 represents a further arrangement of furnace on the basis of Figure 1,
which may be advantageously employed when treating substances which smelt with
difficulty.
Figure is a section on the line b, c, of Figure 4.
Figure 6 represents a furnace for treating continuous lengths or slabs of
material.
Figure 7 is a section on the line c, d, of Figure 6.
Figure 8 is a section on the line, f, of Figure 6.
Referring now to Figures 1 to 3, the charge falls from a hopper or suitably
shaped shoot (up which the hot gases of reaction pass, thus effecting a preliminary
heating of the charge) into the chamber V, wherein they travel along the fusing
zone towards L.
On starting the apparatus, the carbon electrode W, which is later on to serve
as the heating resistance, is brought so close to the electrode L that the arc is
struck. It is then withdrawn, whereupon, in the case of charges capable of
conducting, or capable of becoming conductive in the presence of heat, that
portion of the charge B which lies between the electrodes W and L will come into
the circuit and, at its extreme end, will form a counter electrode to L.
arc.
The gradually tapering electrode W, as well as the charge B (so far as the latter
is capable of conductivity, or has acquired conductivity by the action of the heat
from L and W) continually decrease in their respective cross sections towards the
In other words, in W, as well as in the conductive portion of B, the
resistance constantly increases due to the cross sections decreasing, and consequently
the temperature increases porportionately, as they approach the arc, at which
point only a slight increase of temperature is required in order to effect the
fusion.
The fused material flows into a collecting vessel C, located in an adjacent
chamber.
If the substance to be heated is infusible, for instance carbon for conversion into
graphite, the forward movement of the same is, with a suitably inclined hearth,
preferably effected by imparting to the carbon electrode W a slight to and fro
movement by means of a crank, or an eccentric.
In the form illustrated in Figure 3 the are pole L is arranged above the lowest
end of the hearth, where the smelted product accumulates. This arrangement
is employed where smelted products of a different nature are formed which are
desired to be separated from each other, while in the liquid state, as is done in
ordinary metallurgical furnaces.
Pulverized substances, capable of conducting, or of becoming conductive by heat,
as well as substances which are infusible, or which are fusible only with difficulty,
may also be raised to the desired temperature by this heating process, by using
furnaces such as represented in Figures 4 and 5.
In this case, carbon blocks or plates P are employed, as the contacts for the
portion of the charge B to be brought into the circuit as heating resistance, and
which is in the form of an upright column or pile.
The descent of the charge may be regulated by a rotatable disc S, kept cool. In
proximity to this dise, two electrodes L, of the same polarity and consisting of
carbon plates, surround the charge. The lower part of the charge B thus forms
the counter pole or electrode, whilst the charge located between the arc zone and
the contact blocks or plates P is so chosen, as regards its cross sectional area, as to
offer a sufficiently strong resistance to permit of its being pre-heated sufficiently
by the passing current.

page_text: The material falling from the disc S, collects in a pocket of iron, or other appro-
priate material, from the bottom of which it can be discharged by opening a
slide St.
It is also possible, by means of the furnace shewn in Figures 6, 7 and 8,
to introduce into the furnace briquette-shaped charges of material, consisting
of substances either capable of conducting, or of becoming conductive, when
heated.
M is the outlet of a machine, like a brick-making machine, from which the
charge B, in form of a continuous slab or bar, is propelled over a carbon contact
block P into the ara where it either melts, or, if infusible, periodically breaks up
under its own weight.
The portion of the slab B which lies between the zone of the arc L, and the
contact block P, as well as the portion which lies between the lowermost and
uppermost end of the long contact block P forms a resistance. Now, starting from
the upper edge of said block, the amount of current supplied to this resistance
increases as the resistance approaches the lower edge of P. Hence, the said
resistance will, as it proceeds towards the zone of the arc, be gradually heated
more and more, until, on reaching the arc, it will attain the maximum
temperature.
In order that the resistance may be altered at will, the electrode L which is
surrounded by a protecting cover capable of being cooled, is adjustably arranged.
It may also be pointed out, in reference to the above examples, that fusible
substances can also be so introduced into the circuit as to be first struck by the arc,
and can be then kept hot, say in the form of a liquid stream, by means of resistance
heating, whether for completing a reaction not yet finished at the time of passing
the arc, or for the separation of differently fusible products.
It is not however so much the forms of the apparatus described which constitute
the essential feature of the invention, as the heating process itself, for which an
infinite variety of apparatus of the kind described is applicable.
my said
Having now particularly described and ascertained the nature of
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. A process for the continuous heating of substances in electric furnaces, in
which prior to the substances reaching the arc-zone, they are passed between
5 appropriately arranged and shaped electrodes, so as to be first included in the
preliminary heating that may
circuit as resistances and to be thus subjected to a
or may not increase in intensity, substantially as described.
2. For carrying out the process forming the subject of the first claim, for the
purpose of obtaining calcium carbide, or for heating infusible substances, a
furnace presenting this characteristic feature, that a tapering electrode (W) is
so arranged at an angle to the adjustable electrode, that the layer of material placed
upon the former electrode and moved towards the arc, decreases in cross section,
so that consequently the resistance increases in proportion, while in the case of
infusible substances, the carbon electrode admits of being moved to and fro for
the purpose of displacing the substances, substantially as described.
3. A constructional form of the furnace characterized by the second claim, the
essential feature being that carbon contact blocks or plates (P) are inserted into
the feed conduit of the material, opposite the mouth of which conduit two carbon
plates (L) with are electrodes of equal polarity, are arranged, whilst a cool and
50 rotatable disc (S), serving as a support, regulates the descent of the layer of
material, substantially as described.
4. For carrying out the process characterized by the first claim, in the case of
heating continuous slabs of material, a furnace of the kind set forth in the second
claim, the essential feature consisting in the arrangement of a rigid carbon

page_text: contact block (P) over which the slab shaped material is gradually passed towards
and into the arc, substantially as described.
Dated this 20th day of March 1899
ERNEST DE PASS,
Chartered Patent Agent,
78, Fleet Street, London, and 5A, Market Street, Nottingham,
Agent for the Applicant.