Improved Process for Electric Smelting or Reducing.
Year: 1899

page_text: Date of Application, 20th Feb., 1899-Accepted, 1st Apr., 1899
COMPLETE SPECIFICATION.
Improved Process for Electric Smelting or Reducing.
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, that is to say:-
In "Borchers Electro-Metallurgie," published in 1891, first edition, pages
61-64, a process was suggested for reducing refractory metallic oxides by mix-
ing them with the requisite reducing agent, say carbon, packing the mixture
round a carbon rod serving as an electric heating resistance, and finally passing
an electric current through such resistance.
It has since been ascertained that this method of operating presents, for many
purposes, a number of disadvantages, which, however, are also met with with
even in a larger degree in other electric smelting or reducing processes at present
known.
For instance, the charge becomes covered with dust; or its constituents become
separated by the reaction gases; or the resistance constantly decreases owing to
the conductive action of the fused products; or the parts of the charge, farthest
away from the heating resistance, are liable to cake owing to the infusible nature
of the carbon, this caking preventing movement of the charge towards the zone
of fusion.
Now, according to the present invention, in order to avoid these disadvantages
the carbon intended for carrying out the reactions, instead of being mixed with
the substances to be acted on, is used in the form of bars or plates, as a resistance
in a suitable circuit, whilst the substance to be treated is packed round the car-
bon, care being taken that the said substance is not too finely disintegrated.
As an example of the operations taking place in this process, the manufacture
of calcium carbide, say from lime and carbon, may be described.
The carbon may be made up into a coherent mass or body by kneading with
tar, then formed or moulded, and baked, after which it may be used as a heating
resistance in the furnace. Or instead, the carbon, in a granular but not too
finely disintegrated form, may be rammed in between the conducting carbon
rods or poles in the furnace, suitable moulds being employed to facilitate this
operation.
Around these resistances is packed coarsely disintegrated lime.
On causing a powerful electric current to traverse the carbon resistance, the
particles of lime adjacent thereto will become fused, and by contact with the
electrically heated carbon will be converted into carbide. The place of the carbon
thus consumed. is taken by the next particles of lime, and the molten carbide,
as produced, collects at the bottom of the furnace until the whole of the carbon
has been consumed and converted into carbide, whereupon the current is then
switched off.

page_text: By my improved process, instead of encountering the disadvantages above
mentioned, the following advantages are obtained:
The charge is not liable to be covered with dust,
The gases evolved are free from dust, and hence no clogging of the discharge
pipes need be apprehended, so that it is possible to work with closed furnaces
provided with small discharge pipes, and to directly utilize the gas obtained,
say for driving gas engines.
Moreover, during working, the reaction takes place at the points of contact
between the electrically heated carbon and the substance to be. decomposed,
namely at the place where the requisite heat is supplied by the carbon resist-
ance the most stable of the substances participating in the reaction.
The fused products readily accumulate in the lower parts of the furnace, as the
absence of admixed carbon allows them to run together freely, whereby the
remaining portion of the carbon is left free to act upon the next portion of oxide
that comes into contact with it.
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:
I
1. In electric smelting or 'reducing, inserting the whole of the carbon intended
for the reaction as the resistance into an electric furnace and packing the sub-
stance to be acted on-for instance an oxide, such as lime-round such carbon
resistance without admixture with carbon, and then passing a powerful electric
current through the said resistance, substantially as set forth.
2. My improved process for electric smelting or reducing, substantially as
herein before described.