A New or Improved Lining for the Walls of Electric Furnaces.
Year: 1886

page_text: A New or Improved Lining for the Walls of Electric Furnaces.
I, WILLIAM PHILLIPS THOMPSON, Fel. Inst. P.A. of the Agency for Foreign
Patent Solicitors, 6 Lord Street, Liverpool, in the County of Lancaster, and 323 High
Holborn, in the County of Middlesex, Civil Engineer, do hereby declare the nature
of this invention (a communication from abroad by Eugene H. Cowles and Alfred
H. Cowles both of Cleveland, County of Cuyhoga, State of Ohio, United States of
America, Inventors) and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
This invention relates to the construction of the interior walls of furnaces in
which metallurgical operations are performed by means of electricity, and particu-
larly to the class of furnaces wherein a lining of powdered charcoal or like material
immediately surrounds the charge, and this invention consists in treating the
material of which the said interior walls are usually composed with chemical sub-
stances, or in substituting for the said material a mixture, which is not deteriorated
BO quickly by the action of the heat and electricity.
Prior to this invention the interior walls of electric furnaces have been made of
finely powdered material that is a poor conductor both of heat and electricity,
charcoal being preferably used, that material being a bad conductor of both heat
and electricity and very suitable for the purpose; these interior walls protect the
outer walls of firebrick or other material, and form a lining of considerable thick-
ness which protects the charge.
It has, however, been found in the practical working of electric furnaces that the
fine carbon heretofore used to separate the charge from the walls becomes baked
and hardened when the furnace has been for some time in operation; and that
after a certain number of heats its density becomes so much increased and its
structure otherwise so changed from being subjected to the intense heat and the
action of the current, that it loses in a measure its insulating character.
According to the present invention the finely pulverized charcoal is treated with
certain chemicals, or a mixture substituted therefor of any finely divided materials
of such a character that the temperature of reduction of the interior walls when

page_text: formed of the same will be above that of the material being acted upon by the
current in the furnace.
In selecting substances to form the mixture of which the interior walls are to
consist, those are chosen by preference which would not deteriorate the products
obtained from the furnace, should any chance or partial reduction of them take
place, and those substances are also selected which if reduced by the heat of the
furnace would be volatilized and driven away from the centre of the furnace without
coming in contact with the charge..
Water impregnated with lime is preferably used for the above described purpose.
The finely powdered charcoal is soaked in this until the surfaces of all the particles
are covered with calcium oxide, which also penetrates into the pores of the larger
particles, and renders the charcoal more refractory in its resistance to heat, and
considerably increases its resistance to the flow of the electric current.
When the interior furnace walls are constructed of charcoal thus prepared, they
will last for a much longer time and the work which can be done within them by
a given amount of electrical energy is very much increased.
Other chemicals may be used in place of lime, which will have a similar effect
upon the powdered charcoal, water containing the gelatinous hydrated oxide of
aluminium may be used, and also other substances of a similar nature.
Instead of washing or soaking the charcoal in an aqueous solution, a mixture
may be formed of charcoal and lime, both in a finely pulverized state, and the
interior furnace walls may be constructed of this mixture, or a mixture of finely
pulverized charcoal and powdered oxide of aluminium may be used to effect the
same results and make the walls very poor conductors of both heat and electricity.
The presence of the fine particles of lime or like material through the mass of
powdered charcoal prevents the latter from caking and solidifying.
In the accompanying drawings-
Figure 1 is a transverse section through an electric furnace.
Figure 2 is a horizontal section through the saine.
A is the charge to be reduced, B the electrodes between which the charge is
placed. C is the furnace lining which keeps the charge from contact with the
furnace walls.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is
1. In an electric furnace in which the current passes through the charge, a lining
for the walls of the furnace consisting of a homogeneous mixture of charcoal and a
refractory material which is a poor conductor of electricity, both being in a finely
divided condition, substantially as and for the purpose set forth.
2. A lining for the walls of an electric furnace, consisting of finely divided
charcoal previously prepared by soaking it in water impregnated with lime,
substantially as and for the purpose set forth.
3. A lining for the walls of an electric furnace consisting of a homogeneous
mixture of charcoal and lime, both of which are in a finely divided condition substan-
tially as and for the purpose set forth..
Dated this 25th day of January 1886.